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SAHC Project

Promotion of Solar Assisted Heating and Cooling in the agrofood sector

Intelligent Energy – Europe (IEE)

ALTENER- Renewable heating and cooling

EIE/07/224

D(4) Evaluation of components for solar

refrigeration

Deliverable Author: Laura Sisó / Oriol Gavaldà Organization: AIGUASOL E-mail: [email protected]

Dissemination level : PU / CO Publication date: 30/06/2008

Version: v 1.0

Project website: www.sahc.eu

SAHC Project_D4 Evaluation of absorption heat pumps for solar refrigeration of 73

Content List INDEX

1 ABSTRACT__________________________________________________ 4

2 INTRODUCTION______________________________________________ 5

2.1 WP 3. EVALUATION OF AVAILABLE TECHNOLOGIES AND BEST PRACTICES. OVERVIEW 5

2.2 TASK 3.1 STUDIES, BEST PRACTICES AND GUIDELINES 5

2.3 TASK 3.2 TECHNOLOGY ANALYSIS AND FUNCTIONAL SCHEMES 5

3 SOLAR COOLING TECHNOLOGIES APPLICABLE TO INDUSTRIAL PROCESSES ________________________________________________ 7

3.1 INTRODUCTION 7

3.2 CLOSED SYSTEMS / THERMALLY DRIVEN CHILLERS 10 3.2.1 GENERAL ISSUES 10 3.2.2 GUIDELINES FOR DESIGN, CONTROL AND OPERATION 13 3.2.3 ABSORPTION SINGLE EFFECT LITHIUM BROMIDE-WATER 14 3.2.4 ABSORPTION SINGLE EFFECT WATER-AMMONIA 16 3.2.5 ABSORPTION DOUBLE EFFECT 16 3.2.6 STEAM EJECTOR CYCLES 18 3.2.7 ADSORPTION 19 3.2.8 OTHER AUXILIARY EQUIPMENT 22

3.3 SOLAR COLLECTORS 26 3.3.1 INTRODUCTION 26 3.3.2 SOLAR COLLECTOR EFFICIENCY PARAMETERS 27 3.3.3 FLAT-PLATE COLLECTORS 28 3.3.4 SOLAR AIR COLLECTORS 28 3.3.5 EVACUATED TUBE COLLECTORS 29 3.3.6 CPC TYPE COLLECTORS (STATIONARY CONCENTRATORS) 31 3.3.7 PARABOLIC TROUGH COLLECTORS 32

3.4 ENERGY BALANCE. PRIMARY ENERGY SAVINGS AND OTHER ENVIRONMENTAL BENEFITS 33 3.4.1 GENERAL ISSUES 33 3.4.2 PRIMARY ENERGY SAVINGS 33 3.4.3 SPECIFIC PRIMARY ENERGY ANALYSIS 36 3.4.4 ENVIRONMENTAL BENEFFITS 38

3.5 ECONOMICS: INVESTMENT AND OPERATION COSTS 38

4 BEST PRACTICES ___________________________________________ 41

5 REFERENCES ______________________________________________ 42


Disclaimer

The sole responsibility for the content of this publication lies with the authors. It does not necessarily reflect the opinion of the European Communities. The European Commission is not responsible for any use that maybe made of the information

contained therein.


1 ABSTRACT

This report contents the results of activity WP 3 Evaluation of available technologies and best practices included in the project SAHC Promotion of solar assisted heating and cooling in the agrofood sector. This report shows the status of the art of the technology of solar cooling (that also provides heat to other processes) and present some reference cases to demonstrate the technical feasibility of these systems.


2 INTRODUCTION

2.1 WP 3. EVALUATION OF AVAILABLE TECHNOLOGIES AND BEST PRACTICES.

OVERVIEW

The WP3 of SAHC consists of an identification of the best practices and technical guidelines at the present status of the art for solar assisted heating and cooling systems. Besides the description of the technology collected from on-going and finished projects, also the evaluation of performance and costs of available technologies for low temperature absorption cooling has been done in the framework of this activity. It includes solar thermal collectors and storage and absorption chillers. Finally the know-how learnt has been reflected in functional schemes, including solar collectors, absorption chillers, thermal storage and back-up systems for the application of solar assisted heating and cooling systems in the agro-food sector. This work-package has been divided in two subtasks:

1. Task 3.1 Studies, best practices and guidelines 2. Task 3.2 Technology analysis and functional schemes

The present report collects the results of TASK 3.1.

2.2 TASK 3.1 STUDIES, BEST PRACTICES AND GUIDELINES

In this subtask, the technology description and the best practices on demonstration projects for solar driven cooling applicable to industrial production have been assessed. The information has been collected from previously funded EU projects and collaboration networks as TASK 25 and TASK 38 of the International Energy Agency, Solar Heating and Cooling Programme, as it is listed below:

1. Task 25. Solar Assisted Air-Conditioning of Buildings. IEA-SHC Programme 2. Task 38. Solar Air-Conditioning and Refrigeration. IEA-SHC Programme 3. POSHIP: The Potential of Solar Heat in Industrial Processes. EC DG Energy and Transport.

Coordinator: Aiguasol Enginyeria. (Contract NNE5-1999-0308) 4. Climasol. Solar air conditioning guide. EC DG Energy and Transport. 5. SACE. Solar Air Conditioning in Europe. EC Research Directorate General.

http://www.ocp.tudelft.nl/ev/res/sace.htm 6. ROCOCO. Reduction of costs of solar cooling systems (contract No

TREN/05/FP6EN/S07.54855/020094) 7. SOLAIR. Increasing the market implementation of Solar-Air conditioning systems for small

and medium applications in residential and commercial buildings (contract no EIE/06/034/SI2.446612)

8. SHADA .Sustainable Habitat Design Adviser. http://www.sustainable-buildings.org

2.3 TASK 3.2 TECHNOLOGY ANALYSIS AND FUNCTIONAL SCHEMES

From previous activities in the project, the information about the most suitable equipment for solar assisted heating and cooling systems in agro-food sector has been determined.


Components, ranges of size and characteristics have been defined. A survey has been performed on the market, contacting producers of components, to update the available information. A number of manufacturers for each component have been selected and the average performances and range of cost has been defined. This part of the study has evaluated:

• The applicability of available technologies for solar driven cooling with relation to the load profiles identified before and to different typologies of solar collectors (in relation to the temperature needed for the heat source and to the different climatic conditions)

• The configuration and operational modes presently applied for the integration of solar assisted heating and cooling systems.


3 SOLAR COOLING TECHNOLOGIES APPLICABLE TO

INDUSTRIAL PROCESSES

3.1 INTRODUCTION

The EU industrial sector requires high energy supply (30% of total energy consumption). About two thirds of the final energy use in the European industrial sector is heat1, as shown in Fig 1. Moreover, recent studies highlighted that the food and agro industry heat demand is entirely concentrated in the low and medium temperature ranges2 so that it particularly fits with the use of solar thermal technologies.

Figure 1. Energy share of the industrial sector

Many production processes have simultaneously a heat and cold demand and produce a significant amount of waste heat. The use of the latter has the advantage of being in concurrence with the heat demand of the process. The reuse of this waste heat needs to be done at a temperature level as high as possible. Traditional energy systems usually supply energy at much higher temperatures than those needed, thus allowing the use of small and cheap heat exchangers. The integration of solar thermal driven technologies is therefore a great challenge for both solar and process engineers. A detailed planning and previous energy efficiency analysis using the pinch methodology are necessary to successfully and economically integrate solar thermal power into industrial processes. The pinch analysis enables process engineers to study an industrial process as a whole, aiming at energy efficiency maximisation. Such technique can be used to track energy flows throughout a process, thus revealing where heat is being lost and identifying the areas where energy can be saved for the least amount of money. On the other hand among the circa 100 existing solar assisted cooling plants, only a few are working at collector-field temperatures well above 80°C and even less are refrigeration applications. For several reasons, the efforts of the solar cooling community have concentrated on air-conditioning applications rather than developing experiences within industrial applications.

1 GREEN PAPER – TOWARDS A EUROPEAN STRATEGY FOR THE SECURITY OF ENERGY SUPPLY, Brussels, 2001 2 Ecoheatcool, The European Heat Market - Final Report, 2006

Final Energy Use of the EU - Industry share of heat and electricity

Heat67%

Electricity33%

18,6 % of the total final energy use in the EU


Consequently there is a need to gain experience on solar refrigeration systems. Only the correct choice of appropriate medium temperature collectors and heat driven cooling technology makes the use of solar cooling for refrigeration in industrial processes feasible (even for low temperature refrigeration). There is a high potential and advantages in comparison to applications in other sectors due to a significant economy of scale (i.e., refrigeration technologies represent a large share of the investment and operation costs). Besides that, the wider the range of temperature for solar applications is, the higher the costs savings of the solar systems are, due to a longer period of solar energy use.

Figure 2. Estimated heat demands for EU25+ACC4+EFTA3

This demand increase has various negative consequences.

• As most air-conditioning systems are supplied by electricity, this demand increase results in increases in both electricity consumption and the associated greenhouse gas emissions.

• In addition, electrically powered vapour compression chiller technology uses CFC and HCFC refrigerants that cause pollution.

• Furthermore, there is a serious drawback in the increase of peak loads. The demand increase is most notable during the hottest summer days and sometimes results in a peak of demand that is beyond the present capacity of the electricity network. Big cities with a large amount of office buildings or popular coastal areas with many hotels and seasonal demand peaks are examples of areas where this situation has been happening in recent summer seasons. In case of industries the drawback causes looses in production and as a consequence in the economy of the company.

• The foreseen increase in energy prices makes crucial the development of alternative energy units for the industries.

In this context, the introduction of other technologies that permit cooling using energy other than electricity is not only attractive, it is also necessary. The application of solar energy in cooling systems has several advantages, besides of offering a solution to the above mentioned difficulties. These include:

• The maximum cooling load generally coincides with the maximum available radiation.


• The equipment uses working fluids that are completely harmless, such as water and salt solutions.

• The technology enables solar thermal plants for heat purposes to be usefully exploited even when there is no heat demand.

Solar energy can be converted into forms suitable for final use cooling by means of several physical principles and various technologies. A general overview is given by Figure 13.

vapour compression cycle

electric processphotovoltaic panel

counterflow absorber

liquid sorbent

desiccant rotor fixed bed process

solid sorbent

open cycles

ammonia-water water-lithium bromide

liquid sorbentabsorption

adsorption (eg. water-silicagel)

dry absorption(eg. ammonia-salt)

solid sorbent

closed cycles

heat transformation process

rankine cycle steam jet cycle Vuilleumier cycle

thermomechanical process

thermal processsolar thermal collector

solar radiation

Figure 3. Overview of physical methods to use solar radiation for cooling. (Legend - Yellow: commercially available technology used for

solar-assisted air-conditioning; Grey: technology at the stage of pilot projects or system testing)4

The first distinction relates to solar radiation transformation processes. There are two different technological options: photovoltaics or solar thermal energy. Solar radiation can be converted into electricity using photovoltaic panels, and this electricity can be applied to drive a vapour compression chiller. The present photovoltaics trend in industrialised countries (not isolated off-grid sites) is towards grid-connected systems. These systems have the advantage that they do not need battery energy storage as also benefit from economic incentives of a premium sale price of electricity supplied to the network. Taking into account this idea, it would be more interesting (economically) to supply the electricity produced by a photovoltaic system to the electricity network than to use it to drive a chiller. Despite this economic circumstance, when a considering a new project an initial question should be asked: Which option is more appropriate, photovoltaics to compensate for the electricity a building will use for air-conditioning or a solar thermal system to assist the air-conditioning system? This question must be answered by assessing and comparing all the technical requirements, the primary energy and emissions saved and the related economic factors. Solar assisted air-conditioning systems based on photovoltaics have the same features as common photovoltaics technology. As such they are beyond the scope of this document that is related only to thermal processes and market available technologies. The present technologies in air conditioning or cooling systems driven by solar heat and based on a heat transformation process can be initially classified as open systems and closed systems.

� Open systems: in this case, the refrigerant, that is always water, is in contact with the atmosphere. These systems act directly over the air in an air-handling unit (all-air-system), cooling and dehumidifying it according to the comfort conditions. The open systems are based on a combination of sorptive dehumidification and evaporative cooling, and are usually known as desiccant and evaporative cooling (DEC) systems. The sorbent material can be solid or liquid, although the second is not yet introduced in the market. The solar heat energy is used to regenerate the equipment used to dehumidify the air.

3 Hans-Martin Henning (Ed.): Solar-Assisted Air-Conditioning in Buildings. A Handbook for Planners. SpringerWienNewYork. 2003 4 Source: Hans-Martin Henning (Ed.): Solar-Assisted Air-Conditioning in Buildings. A Handbook for Planners. SpringerWienNewYork. 2003


� Closed systems: the solar heat is supplied to a thermally driven chiller that produces cold

water. This water can be directly distributed to the air conditioning system by means of fan-coils or chilled ceilings (water-system) or to a cooling coil in an air-handling unit (all-air-system). Two types of equipment are present in the market nowadays: absorption and adsorption chillers.

The present document has not considered the open systems due to they are specially applicable on air-conditioning plants. The application of solar cooling in agro-food processes leads to the use of solar resource at different temperature levels, from -5ºC to 95 ºC. In that sense, the authors have focused on the description of the technology in closed systems since they fit better in this variety of different uses of solar heat.

3.2 CLOSED SYSTEMS / THERMALLY DRIVEN CHILLERS

3.2.1 GENERAL ISSUES

Thermally driven chillers , both absorption and adsorption types, operate on the basis of a process that permits heat transfer from a low temperature source to a high temperature source. This is made possible by using additional heat from a higher temperature level. This principle is similar to that applied in electrically driven vapour compression chillers. The difference is that electricity consumption is substituted by heat consumption. The low temperature source corresponds to the room to be cooled (or the medium that transfers the energy from there). Most of the systems work at 7ºC - 12ºC (fan-coil based or the ones requiring second-skin coolers for industrial tanks) or lower, 6ºC - 9ºC, (application of a dehumidification coil in an air-handling unit) but higher temperatures, 15ºC - 18ºC, are suitable for chilled ceiling based systems. The heat absorbed is rejected to the atmosphere, usually by a cooling tower. The additional heat necessary for the operation of the system can come from solar collectors or from other sources such as direct combustion, cogeneration, district heating or waste heat. For most of the solar thermal applications (selective flat-plate, evacuated tube, stationary CPC collectors) the maximum temperature required by the machine must not exceed 90 ºC. Higher temperatures are possible with other technologies as parabolic trough collectors. Air collectors are not suitable for providing heat to thermal driven chillers as the fluid to be heated is water. The type of solar collectors most suitable for any specific application of solar assisted air conditioning system is highly dependant on the global available irradiation and on other uses of the heat produced (heating, domestic hot water, other thermal processes). The efficiency of thermally driven chiller can be represented by the Coefficient of Performance (COP). The parameter is defined as the relation between the useful cooling and the required driving heat. In the case of electrically driven compression chillers, the parameter refers to electricity consumption. The next schematic diagram, illustrates the energy balance of a thermally driven chiller:


Figure 4. Energy balance in a thermally driven chiller

In the energy balance of a complete solar assisted air conditioning system, electricity consumption in fans and pumps of the installation must be also considered. If the COP of the chiller increases, it means that the driving heat is smaller as well as the rejected heat. This means that the energy consumption by pumps in heating cycle will be reduced and also that the cooling tower fans. The efficiency of a solar assisted air conditioning system is highly dependant on the temperature levels in the thermally driven chiller circuits:

� The higher the temperature of the driving heat, the higher the COP of the chiller but the lower the efficiency of the collector field.

� The lower the temperature of the rejected heat, the higher the COP of the chiller but the bigger the size of the cooling tower.

� The higher the temperature of the cooling output, the higher the COP.

From the last statement it can be observed that fan-coil based systems that require 7ºC of cold water production have lower chiller efficiencies than chilled ceiling based systems that can work at 15 ºC. The advantages of thermally driven chillers compared to electrically driven vapour compression chillers include the following:

� Maintenance costs are lower as there are fewer moving parts. � Operation costs are lower as electricity consumption is very low (around 1% - 5 % of chilled

water capacity). � Performance is higher in nominal conditions at a partial load. � The substances used are absolutely safe environmentally (water, lithium bromide, ammonia,

silica gel). The main equipment types in the category of thermal driven chillers are absorption and adsorption machines. In the following table, the principal market features are summarised.

heat

cold

Q

QCOP=

rejectedcoldheat QQQ =+

COPQ

Q

heat

rejected +=1

driving heat

cooling output

rejected heat

SOLAR PRODUCTION

AIR CONDITIONING SYSTEM

Thigh ; Qheat

Tlow ; Qcold

Tmedium ; Qrejected

AMBIENT

COOLING TOWER

COPQ

Q

cold

rejected 11+=


Table 1. Thermal driven chillers main features for present market5

process absorption adsorption

stages single effect double effect single effect

ab/adsorbent lithium bromide / water (1) silica gel

refrigerant water / ammonia (1) water

generator T. 80 ºC – 110 ºC 140 ºC - 160 ºC 60 ºC – 95 ºC

flow hot water or overheated water

overheated water or steam

hot water

COP 0.6 - 0.8 0.9 – 1.2 0.4 – 0.7

market capacity

< 35 kW incipient market

35 kW to 100 kW few manufacturers

>100 kW wide market

>100 kW wide market

< 50 kW (Sort.)

50 – 350 kW (May.)

70 – 1220 kW (Nis.)

manufacturers Climatewell, Rotartica, Sonnenklima, Schucö, Yazaki,

Broad, EAW, Carrier, Trane, York, LG Machinery, Sanyo-McQuay, Entropie, Thermax, …

Sortech, Mayekawa, Nishiodo

suitable solar collector selective flat-plate

evacuated tube

stationary CPC

parabolic trough

selective flat-plate

evacuated tube

stationary CPC (1) Pair of absorbent /refrigerant are as in the same order as indicated

The next schematic diagram illustrates an installation that uses a thermally driven chiller connected to solar collectors.

Figure 5. Thermally driven, chiller based, system with solar collectors and back-up heat pump

In order to reduce the surface of solar field one alternative can be to use systems with improved COP, which may be achieved with a higher temperature of the heat source. To take advantage of a high temperature heat source, absorption systems must be configured in stages (Alefeld, 1982). The principle is to use the heat rejected from the condenser to power additional desorbers, thereby approximately doubling or tripling the amount of refrigerant extracted out of solution with no extra solar heat spent6.

5 Source: AIGUASOL S.C.C.L. 6 Source of this concept description: SACE. Solar Air Conditioning in Europe. EC Research Directorate General. http://www.ocp.tudelft.nl/ev/res/sace.htm


Most of the present experiences on solar cooling use LiBr/H2O instead of H2O/NH3. The advantages of LiBr/H2O are the following:

• Non-toxic substances • Lower working pressures • Non-volatile absorbent (rectification of refrigerant is not required, see Chapter 3.2.4) • COP relatively high (typical COP for LiBr/H2O is around 0.7 and for H2O/NH3 is 0.5, 30 %

lower) However, they have also the following disadvantage:

• Water cooled is required (using of cooling tower is the most common technology with the inconvenience of legionella risk).

• Higher physical size, due to the large vapour volume of the water refrigerant.

3.2.2 GUIDELINES FOR DESIGN, CONTROL AND OPERATION7

In case of LiBr/H2O, the following issues must be considered:

• Freezing of refrigerant and cooling tower water at ambient temperature below 0ºC. That problem must be considered in winter. If cooling is not used to empty the pipes and equipment is recommended.

• Crystallization of the LiBr solution at high concentration. It can occur o At high temperature level on generator o At low temperatures on re-cooling inlet to the absorption chiller

Control of both temperatures is required to avoid those risks. It is recommended to use three ways valves. These valves can be used also to control the capacity of the machine.

The following considerations are referred to the whole design of solar cooling plant based on thermally driven chillers and are focused on minimizing the primary energy consumption of the whole system:

• Operation of the solar field in match flow is recommended to fit the temperature of the absorption chiller and to reduce the pump consumption in solar field.

• Use of gas or fuel boiler as back-up: This configuration must be used only with higher solar fractions over cooling demand since in other case the consumption of primary energy could be higher than the application with vapour compression chillers. The reason is the lower COP of absorption regarding with compression. The appropriate solar fraction depends on the particular application but in common air-conditioning profiles it must be higher than 60-70 %. Other risks on boiler as back-up are to break the stratification of the storage tank and also to convert the solar collectors into a heat sink, if boiler is connected in series with solar collectors and radiation is low. An interesting application is the absorption chillers with two stages and two different entrances for heat, one coming from solar and the other from a boiler, at higher temperature.

• Use of compression chiller as back-up. This is a possible solution to overcome the previous problems. This is particularly appropriate when solar cooling fraction is low. It can operate in parallel or in series with the absorption chiller, depending on the demand profile and the user requirement.

7 Collected from: SACE. Solar Air Conditioning in Europe. EC Research Directorate General. http://www.ocp.tudelft.nl/ev/res/sace.htm, YAZAKI provider ABSORSISTEM, S.L. and AIGUASOL SCCL experience.


• The use of buffer storage is recommended to stabilize the operation and control of the whole system, avoiding the transfer of possible temperature peaks of collector field to the rest of the equipment.

• The control strategy must take into account the security of the plant and also the minimization of primary energy consumption (back-up and parasitic electricity). Different control strategies can be implemented to adequate the solar resource to the demand profile. Some examples that also can be combined between them are:

o To keep constant or to leave variable the inlet temperature at generator (boiler as back-up is required).

o To determine the optimum value to fix the set-up in the inlet temperature of the generator.

o To vary the inlet temperature at absorber changing the fan-speed or using a three-way valve.

o To determine the optimum value to fix the set-up in the inlet temperature of the absorber.

o To control the pump of distribution of cold water to the building (variable flow) depending on the water temperature difference between supply and return.

3.2.3 ABSORPTION SINGLE EFFECT LITHIUM BROMIDE-WATER

Absorption chillers are thermally driven chillers where compression of the refrigerant is achieved by using a liquid refrigerant/sorbent solution and a heat source that replaces the electric consumption of a vapour compression chiller. This kind of thermally driven chiller is very common both for air conditioning and industrial applications. The market is widespread and well established. As shown in Table 1, absorption chillers can be classified according the following criteria.

� Depending on stages: single effect or double effect � Depending on the absorbent – refrigerant pairing: lithium bromide-water or water-ammoniac

For applications above 0ºC, as the case of the air conditioning systems, the most common application is the lithium bromide-water systems. Water-ammoniac machines are more usual in food preservation or other industrial applications. The supplied heat source can be hot water, overheated water, steam or direct combustion. Direct combustion technology is not included in the table above as their use with solar energy is not compatible in this context. Moreover, for common solar collector technology the most common absorption chillers are single effect types driven by hot water. The main components in an absorption chiller are the following, and can be seen in the following figure.

� Generator (or desorber) � Absorber � Condenser � Evaporator

Absorption cycles are based on the fact that the boiling point of a mixture is higher than the corresponding boiling point of a pure liquid. Figure 6. Scheme of single effect cycle. Source: YAZAKI


Moreover, the evaporation of the refrigerant is possible as the recipient is at very low pressure (around 6 mmHg). The operation of absorption machines is explained in the following paragraphs:

1. The refrigerant (water in LiBr absorption machines) evaporates in the evaporator, at very low pressure, extracting heat from the fluid that must be cooled. This happens at a low temperature.

2. The refrigerant vapour flows to the absorber that is directly communicated with the

evaporator. There, it is absorbed by the concentrated solution. In this process, latent heat of condensation and mixing is produced and this must be removed by a cooling coil that comes from a cooling tower.

3. The diluted solution produced in the absorber is pumped to the generator where it is heated

to above its boiling point by the heat source (a solar collector field in the case of solar assisted air-conditioning systems). The refrigerant is separated again from the solution at high pressure and the concentrated solution is driven to the absorber.

4. The refrigerant vapour flows to the condenser at high pressure. The condenser is directly

communicated with a generator. Here the vapour is condensed by the cooling water. This water comes from the absorber and is driven to the cooling tower to reject all the amount of heat obtained in the absorption machine.

5. The liquid refrigerant pressure is reduced by an expansion valve. The refrigerant then flows

to the evaporator.

Most commercially available absorption chillers need a solution pump to transport the diluted solution from the absorber to the generator. The electricity power of this pump is around 1% - 5 % of the cooling capacity. As shown in the previous figure, there is a heat exchanger between the diluted solution and the concentrated solution to pre-heat the flow driven to the generator. The internal control of the absorption chiller must avoid crystallisation of the solution. This can occur if the temperature of cooling water coming from cooling tower is too low. The limiting temperature depends on the manufacturer. A typical value is 24 ºC.

Figure 7. Absorption machines. Sources: YAZAKI (left) and BROAD (right)


3.2.4 ABSORPTION SINGLE EFFECT WATER-AMMONIA

The operation of absorption single effect H2O/NH3 chillers is similar to the one described for the case of LiBr/H2O but changing the substances that are absorbent (H2O) and refrigerant (NH3). The main advantage of H2O/NH3 is the large range of applications for evaporation temperature from 5 ºC to -50ºC, that includes air-conditioning, brine cooling and deep freezing. The COP is relatively high for air-conditioning purposes (5ºC) reaching values of 0.6 and decreases whith evaporator temperature. One of the particular facts of the pair H2O/NH3 is the need of rectification. In this case the water is the absorbent and this has a significant vapour pressure when boiling in comparison with LiBr, that can be neglected. The pressure of water when the generator temperature is higher than 90 ºC makes to reduce the concentration of ammonia. Then the content of water may be excessive in evaporator causing some problems, especially for deep-freezing applications. Therefore the process of rectification leads to remove the water to the refrigerant (NH3) vapour. The rectification equipment is very well-known in the process engineering field and has to fulfil the task to enlarge the concentration of the refrigerant in the vapour to the range of 99.0-99.5%. The principle of rectification consist of the following: the ammonia/water vapour rises out of the generator and contacts the concentrate working fluid, which has a temperature only few below the boiling point, at large surfaces. For that purpose the strong (concentrate) working fluid is pumped to the top of the generator, is distributed on the cross section and drips, for example through a recharging set, with a large surface. The recharging set is a simple rectification facility that consists of heaped up steel or glass tubes. In counter flow to the strong working fluid, which drips from the top to the bottom of the recharging set, the ammonia/water vapour rises from the bottom to the top. At first water of the ammonia/water vapour condenses at the surface of the strong working fluid and at first ammonia evaporates out of the boiling strong working fluid on its way from the top to the bottom. The one after the other following steps of condensing and evaporating result a significant higher concentration of ammonia in the vapour, which enters the condenser. But the rectification needs also additional heat for the same evaporation capacity as without rectification. Thus, the thermal COP is lower with rectification than without but deeper evaporation temperatures could be reached and disturbances in evaporator avoided8. Small absorption refrigeration machines, with evaporation temperatures round 0ºC have a simpler and cheaper rectification system than larger systems or freezing systems. Also the top of a falling film generator could be designed as a simple rectificator adjusted to the working fluid heat exchanger.

3.2.5 ABSORPTION DOUBLE EFFECT

In the multi-staging absorption chillers, as for instance, double effect the principle consist of two desorbers and two condensers to supply only one combination of absorber-evaporator. In comparison to single effect machine ,the following additional elements are included: condenser (7), desorber (8), heat exchanger (9) and expansion valve (10). The numbers in brackets correspond to Figure 9. 8 Source of the description of rectification: SACE. Solar Air Conditioning in Europe. EC Research Directorate General. http://www.ocp.tudelft.nl/ev/res/sace.htm

Figure 8. Small capacity H2O/NH3 chiller. Source: PINK


The system operates at three pressure levels and four temperature levels. The weak solution (state 14) leaving the absorber (2) is circulated to the two desorbers, connected in series and is regenerated in two stages, sharing the process between both desorbers. The solar heat at the highest temperature is applied to the high-temperature desorber (8). Meanwhile the low temperature desorber (4) receives the rejected heat from the high temperature condenser (loop 7-8). The condensates form both condensers expand into the evaporator.

Figure 9. Scheme of double effect cycle. Sources: Reference (Grossman, 2002)

The same principle can be extended to triple effect with three desorbers and three condensers when sufficiently high temperature of the heat source is available. Double effect equipment has been largely introduced in U.S.A and Japan market, particularly with gas-fired applications. Triple effect equipment is nowadays still under development but close to the market. The Figure 10 shows the relation of COP with the supplied temperature to the desorber, for several multi-effect chillers, under the same size components and operation tempearatures (re-cooling water inlet at 30 ºC and chilled water outlet at 7ºC). It must be noticed that for each absorption cycle there is a minimum value of the temperature level supplied to generator below which it does not perform


at all. If this temperature increases, the COP rises sharply, then levels off to some asymptotic value9.

Figure 10. Coefficient of Performance as a function of solar heat supply temperature for single, double and

triple effect LiBr-water absorption chillers

The benefits of double effect regarding the single effect cycles is that the cooling effect per unit of heat can be nearly doubled. As shown in Table 1, this equipment requires temperatures above 140 ºC, but the COP can reach 1.0-1.2. They are not the most suitable type for use in applications using common solar collectors but can be an interesting option if coupled with parabolic trough collectors (see Chapter 3.3.7).The application of double effect with parabolic trough collectors offers an opportunity to overcome the barrier of efficiency in existing cooling systems based of single effect thermally driven chillers and flat-plate collectors or evacuated tube collectors. However, in case of double effect it should be noticed that the high driving temperatures must be kept in order not to go in sharply decrease of the COP. These considerations influence the design of the solar system regarding the operation pressures, expansion vessel, etc.

3.2.6 STEAM EJECTOR CYCLES

The application of steam ejector cycles with solar energy is nowadays on research state of the technology. The scheme in following figure shows the performance. It corresponds to a project in Overhausen (Germany) of 17 kW of cooling capacity where COP values of 0.85 where obtained. This technology is really promising with application of parabolic trough collectors able to produce steam.

9 Documented in Gommed and Grossman, 1990


Figure 11. Scheme of stem ejector system with parabolic through collectors

3.2.7 ADSORPTION

Adsorption chillers are thermally driven chillers based on the adsorption principle. This consists of gas molecules bonding with the pores of a highly porous hygroscopic material. The physical effect of adsorption is produced due to the fact that the partial water vapour pressure at the surface of a hygroscopic (adsorbent) material is lower than the partial water vapour pressure in air. Consequently, these kinds of materials are suitable for attracting water vapour from the air and binding it in their structure as water without increasing its volume or resulting in a structural change. After reaching the saturation point the adsorptive substances must be regenerated to prepare the material for a further use and to close a cyclic process. This is achieved by using a heat source. The drying effect of these adsorbent materials decreases with increasing desiccant moisture and corresponding decreasing humidity or decreasing water vapour partial pressure in the air. Increasing temperature also causes the drying effect to decrease. The process of sorptive dehumidification in desiccant and evaporative cooling cycles is an example of an adsorption process. Another application is the use of activated carbon filters, as adsorbent materials, in process engineering in order to clean waste air streams contaminated with solvents. The most common industrial absorbents are silica gel, activated carbon and alumina, because their surface areas per unit weight are enormous. Activated carbon is produced by roasting organic material to decompose it into carbon granules. Coconut shell, wood and bone are common sources. Silica gel is a matrix of hydrated silicon dioxide. Alumina is mined or precipitated aluminium oxide and hydroxide. The adsorption thermally driven chiller operation cycle is based on two physical phenomena:

� The adsorptive material (silica gel in commercial equipment) has water vapour adsorption capacity.


� The water evaporates at very low temperatures when the ambient pressure is very low (5-6 mm Hg).

In a closed system in a vacuum, water can be evaporated out of the silica gel by the application of heat (hot water at a lower temperature). After condensation in a condenser, the water is sprayed into another closed section of the vessel and evaporates in the vacuum that also exists in this section. In this way, heat is obtained from a pipe coil of a chilled water heat exchanger. The adsorption chiller main structure is a pressure vessel made from steel and sub-divided in four chambers:

� An upper chamber that works as a condenser � Two middle chambers alongside one another used as generator-receivers � A lower chamber that that works as an evaporator.

The generator-receivers are each linked to the condenser and the evaporator via flap valves. Inside each chamber, there is a copper tube heat exchanger. The two middle chambers of generator receivers are filled with granular silica gel material. The following picture, illustrates the cycle schematically.

Figure 12. Scheme of adsorption machine and its cycle. Source: ALBRING Industrial Agency GmbH. MYCOM Adsorption chiller Technology

The operation of adsorption machines is explained in the next paragraph:

1. The cycle starts with the evacuation of the pressure vessel by a vacuum pump is installed in the machine for this purpose. After the vacuum is achieved, a given amount of water is admitted to the system.

2. The machine operates in 10 minute cycles. In the first cycle, heat is supplied to one

generator which contains silica gel saturated with water vapour (HE1 in Figure 12). Meanwhile, the other chamber (HE2 in Figure 12), containing dried silica gel, acts as the


receiver of water vapour from the evaporator. During this process, the receiver and the condenser are cooled by the cooling water circuit. This is usually connected to a cooling tower to dissipate the heat to the atmosphere.

3. At the end of these 10 minutes, the pneumatic valves remain closed for a 40 second re-

circulation phase during which the cooling and heating water of the silica gel heat exchangers are mixed for partial heat recovery and also to prevent hot or cold shock.

4. After this short stage, the machine is switched over by means of the pneumatic valves. The

chamber which had previously acted as the receiver (HE2 in Figure 12) now acts as the generator and is heated, whilst the other chamber (HE1 in Figure 12) now operates as the receiver and is cooled.

5. During this periodic process, water vapour is produced which is condensed again to form

water in the condenser (located above the generators). This refrigerant then is pumped through an injection valve into the evaporator chamber and evaporated in the higher vacuum in this chamber, drawing heat from the chilled water circulating through the evaporator heat exchanger. The resulting water vapour is condensed again and adsorbed by the dry silica gel in the adjacent receiver.

At present, there are only two Asian manufacturers with commercially available equipment. The average COP of this equipment is around 0.5 - 0.6. The following pictures show two models. In the second one, the various components are labelled.

Figure 13. Absorption machines. Sources: MYCOM (left) and NYSHIODO (right)

The main advantages of adsorption chillers compared with absorption chillers are as follows: � The operating temperatures at the generator can be lower: from 60 ºC to 90 ºC in adsorption,

compared to 90 ºC to 120 ºC in single effect absorption chillers. � There is no lower limit to the cooling water temperature in the back-cooling system as there

is no danger of crystallisation.


� Changes in the COP are not so dependent of the generator water temperature or cooling water temperature as in the absorption chillers (see picture below).

Figure 14. Example of coefficient of performance comparison between adsorption and absorption equipment.

On the other hand, the main disadvantages of adsorption chillers compared with absorption chillers are as follows:

� The average COP of the adsorption equipment is worse in comparison with absorption equipment.

� The equipment in the market at present is both larger and heavier than comparable single effect absorption chillers.

� Adsorption equipment is more expensive.

3.2.8 OTHER AUXILIARY EQUIPMENT

3.2.8.1 COOLING TOWER

A cooling tower is a heat rejection device. It extracts waste heat to the atmosphere though the cooling of a water stream to a lower temperature. The type of heat rejection in a cooling tower is evaporative because as a small portion of the water being cooled is allowed to evaporate into a moving air stream to provide significant cooling to the rest of that water stream. The heat from the water stream transferred to the air stream raises the temperature and the relative humidity of the air to 100%. This air is then discharged to the atmosphere. Evaporative heat rejection devices such as cooling towers are commonly used to provide significantly lower water temperatures than achievable with air cooled or dry heat rejection devices, achieving more cost-effective and energy efficient operation of systems. Common applications for cooling towers include the supply of cooled water for air-conditioning, manufacturing and electric power generation. The generic term cooling tower is used to describe both direct (open circuit) and indirect (closed circuit) heat rejection equipment.


A direct, or open circuit, cooling tower is an enclosed structure with internal means to distribute the warm water fed to it over a honeycomb packing or fill. The fill provides a vastly expanded air-water interface for air heating and evaporation to take place. Water is cooled as it descends through the fill by gravity while in direct contact with air that passes over it. The cooled water is then collected in a cold water basin below the fill from which it is pumped back through the process to absorb more heat. The heated and moisture laden air leaving the fill is discharged to the atmosphere at a point remote enough from the air inlets to prevent its being drawn back into the cooling tower. The fill may consist of multiple, mainly vertical, wetted surfaces upon which a thin film of water spreads (film fill), or several levels of horizontal splash elements which create a cascade of many small droplets that have a large combined surface area (splash fill). An indirect, or closed circuit, cooling tower involves no direct contact of the air and the fluid, usually water or a glycol mixture, being cooled. Unlike the open cooling tower, the indirect cooling tower has two separate fluid circuits. The first is an external circuit in which water is recirculated around the second circuit. The second is made up of tube bundles (closed coils) connected to the hot process fluid to be cooled and returned in a closed circuit. Air is drawn through the recirculating water cascading over the outside of the hot tubes, providing evaporative cooling similar to that in an open cooling tower. In operation, heat flows from the internal fluid circuit, through the tube walls of the coils, to the external circuit where it causes some water evaporation and heats air that then is extracted to the atmosphere. Operation of indirect cooling towers is therefore very similar to that of open cooling tower with one exception: the process fluid being cooled is contained in a closed circuit and is not directly exposed to the atmosphere or to the recirculated (external) water. There are several hybrid systems which are able to determine if the operation is done in a sensible cooling mode against ambient air or in a latent cooling mode by water evaporation. In a counter-flow cooling tower air travels upward through the fill or tube bundles, in the opposite direction to the downward travelling water. In a cross-flow cooling tower air moves horizontally through the fill as the water moves downward. Cooling towers are also characterized by the means by which air is moved. Mechanical-draft cooling towers rely on power-driven fans to draw or force the air through the tower. Natural-draft cooling towers use the buoyancy of the exhaust air rising in a tall chimney to provide the draft. A fan-assisted natural-draft cooling tower employs mechanical draft to augment the buoyancy effect. The most common application of cooling towers is to be used as heat rejection equipment for a thermally driven chiller in an open circuit, counter-flow arrangement with air entering at the bottom of the tower and a suction fan located at the top.

Figure 15. Scheme of cooling tower (open circuit). Source: EVAPCO


If cooled water is returned from the cooling tower for reuse, some water must be added to replace the portion of the flow that evaporates. Because evaporation consists of pure water, the concentration of dissolved minerals and other solids in the remaining circulating water will tend to increase unless some means of dissolved-solids control, such as blow-down, is provided. Some water is also lost by droplets being carried out with the exhaust air. This loss is typically reduced to a very small amount by installing baffle-like devices, called drift eliminators, to collect the droplets. In order to maintain a steady water level, the amount of water replaced must equal the total of evaporation, blow-down and drift losses and others such as wind blow-out and leakage losses. The capacity of a cooling tower depends strongly of the wet bulb temperature of the ambient air. The minimum temperature gradient between this value and the temperature of the water leaving the tower is around 3ºC - 5ºC.

3.2.8.2 FAN-COILS

Fan-coils are the most common terminal equipment in water based air-conditioning systems. A fan coil is a heat exchanger with a fan that simply circulates indoor air over it. This thermostatically controlled fan draws air from the room and blows it over the coil of bundled copper tubes that form the heat exchanger. This coil is supplied with cold water (air-conditioning use) or hot water (heating use) that circulates inside the tubes. The air flowing over the coil is cooled or heated prior to entering the room. The cold or hot water is produced centrally. In case of solar assisted air-conditioning systems, one of the technologies explained previously, thermally driven chiller based systems may be used (see Chapters 3.2.3 and 3.2.7). The control of fan-coils can be based simply on a thermostat or can incorporate more sophisticated elements such as variable speed fans, three way valves, etc. There are different models such as ceiling mounted, concealed or recessed vertical floor units. Two main types of fan-coils can be distinguished in the market, as a function of the kind of water based air-conditioning system they are used in:

� Two-pipe systems have one supply pipe and one return pipe. The heat exchanger can supply either heating or cooling. This kind of fan-coil is usually installed in systems that operate either in heating mode or in cooling mode in all zones of a building. Simultaneity between uses (heating in one zone and cooling in another) is not allowed.

� Four-pipe systems are equipped with two independent coils, one for heating and one for

cooling. Valves in each circuit control the coil capacity. This type of equipment and system is installed where heating and cooling can occur simultaneously in different zones of a building.

Some two-pipe fan-coils are equipped with an electric heater. Common standard operation conditions for fan-coils are 7 ºC -12 ºC for cooling and 45 ºC - 50 ºC for heating.


In comparison with chilled ceilings (see Chapter 3.2.8.3) the operating temperature of fan-coils is very low. This is a drawback in the case of solar assisted air-conditioning systems as the lower the chilled water temperature, the lower the coefficient of performance in the thermally driven chiller. Commercially available fan-coils typically have cooling capacities that vary between 0.5 kW and 10 kW. In general, their heating capacity is twice the cooling capacity. Fan coil performance can oscillate between 10 % and 100 % of nominal conditions as a function of air flow rate. Most fan-coils models in the market are equipped with condensation disposal device where control of indoor humidity is possible. Condensation occurs when air is cooled below its dew-point and depends on indoor conditions.

3.2.8.3 CHILLED CEILINGS

A chilled ceiling contains a network of tubes, usually plastic or copper, in which cold water circulates. The network of tubes is either attached to the ceiling and covered by a false ceiling, or directly attached to the false ceiling elements, or clipped onto metal diffusers. In air-conditioning systems that use chilled ceilings, the main part of the sensible load is met by this equipment. A ventilation system is also required to cover the latent load as a chilled ceiling is not able to do this. The proportional split of heat transfer between radiative and convective mechanisms in a chilled ceiling depends on the ceiling configuration. If the tubes are completely enclosed in the ceiling, transmission is by radiation. However, if the chilled elements are hung in a metal structure (a more ‘open’ system) part of the transfer happens by convection. Water is the transfer medium cooling the room. The water inlet temperature in a chilled ceiling can vary between 15 ºC and 18 ºC, and a temperature difference of 2 ºC – 3 ºC is produced in the system. The cooling capacity of chilled ceilings ranges from 70 W/m2 for drop-in ceiling applications and up to 140 W/m2 for free-hanging designs10. In order to avoid condensation it is necessary to provide the installation with dew-point sensors. When the condensation temperature is going to be reached, water flow is reduced or supply temperature increased, to reduce the cooling capacity of the system. This kind of cold water networks can be placed on walls or floors. In the case of chilled floors, a useful application is for cooling and heating supply depending on the season. The floor network is often made entirely of plastic materials that are placed in an insulated layer, to reduce heat losses. The entire construction is then embedded in a floating slab. The considerations mentioned earlier regarding ventilation, latent loads and condensation are applicable for chilled floors as well as chilled ceilings. Furthermore the fact that chilled floors have a high thermal inertia must be considered. In case of cooling-only applications this inertia should be reduced. However, in heating supply applications this is not of interest. This difference is because maximum cooling demand usually occurs during midday but maximum heating demand happens at the end of the day. Radiant floor heating technology is well-established but the cooling applications are more recent and less well known. The main advantages are that:

� The same equipment supplies heating and cooling

10 Figures valid for a difference between room air temperature and average water temperature of 10 ºC


� It is completely integrated in the structural elements so no room space is occupied by terminal elements for air-conditioning.

The main disadvantage of chilled floors is the relatively low cooling capacity (in the range of 35 W/m2 - 40 W/m2.11). This can be enough for rooms where comfort conditions do not need to reach the standard values. However, for most building zones, a supplementary air based air-conditioning system will be necessary to cover the part of the sensible loads (besides latent loads and ventilation) not covered by the chilled floor. The main advantage of chilled ceilings and floors, with regard to solar assisted air-conditioning systems, is the higher operating temperatures compared to fan-coils. The range of inlet-outlet temperatures is around 16 ºC – 19 ºC compared to a typical fan-coil range of 7 ºC – 12 ºC. This fact results in an increased thermally driven chiller capacity and COP.

3.3 SOLAR COLLECTORS

3.3.1 INTRODUCTION

The input temperature range required of the solar part of solar assisted air conditioning systems depends on the type of cooling equipment used: 50 °C or more, for desiccant cooling based open systems, 65 ºC or more for adsorption chiller based closed systems and 85 ºC or more for absorption chiller based closed systems. Due to this temperature difference, the choice of the most suitable solar collector type varies according to cooling equipment type. In this chapter, brief technical descriptions of the available solar collector technologies and solar system concepts are given. The simplest solar collector consists of a black surface with some fluid circulating in or around it. The fluid serves to extract the heat produced by the radiation absorbed from the sun so that it can be used for some practical application. The heat losses from such an absorber are large if nothing is done to reduce them. The losses can be reduced by placing the collector in a box, with insulation behind it and with a transparent cover. This simple arrangement is known as a single cover flat-plate collector.

Figure 16. Cross-section of a flat-plate solar collector (left). Detail of flat-plate collector (right), source: VIESSMANN

The selection of the appropriate collector type depends mainly on the desired working temperature and on climatic conditions.

11 Figure valid for indoor temperature of 26 ºC and floor surface temperature of 20 ºC


Solar collector efficiency decreases as the fluid temperature increases or the available solar radiation decreases. A graphical representation of the instantaneous efficiency for different collector technologies is given in Figure 17. Different collector technologies have been developed in order to achieve a higher efficiency at higher temperatures. Two major types of solar collectors can be considered for providing the temperatures required in closed solar assisted air conditioning systems:

� Stationary collectors. These collectors do not use any mechanisms to track the sun. They can produce heat at low and medium temperatures (up to 150 °C). Flat-plate collectors, evacuated tube collectors and compound parabolic concentrator (CPC) type concentrators, belong to this group of collectors.

� Parabolic trough collectors. These are one-axis sun tracking collectors used both in solar

process heat plants and in large power plants for solar thermal electricity generation. Temperatures up to 300 °C can be obtained with good efficiency.

In addition to these collector types that offer better efficiency at high temperatures, solar air collectors offer good results at low temperatures and are therefore suitable for applications such as desiccant cooling. A description of the most important solar collector types is given in the following sections.

3.3.2 SOLAR COLLECTOR EFFICIENCY PARAMETERS

The instantaneous efficiency (η) of a solar collector is defined by the ratio of the power delivered to the load (circulating fluid) to the incident solar irradiation on the aperture area of the collector.

The efficiency is usually represented as a function of TG

T∆ where:

∆T (K) is the difference between the average fluid temperature (the temperature of the fluid used to extract the collected power) and the atmospheric temperature;

GT (W/m2) is the amount of incident solar radiation available to the collector.

The instantaneous efficiency η is thus written as:

T210 G

T*)Tcc(c

∆∆+−=η

Where: c0 is the optical efficiency (a function of collector cover transmission, receiver absorption

and reflectivity of mirrors in the case of concentrators) c1, c2 are the linear and quadratic heat loss coefficients; parameters that characterise the heat

losses from the collector to the atmosphere (including convection, conduction and radiation heat loss mechanisms). c1 (W/K m2); c2 (W/K2m2).

In the next figure, the efficiency of different type of collectors is shown as a function of temperature difference between ambient air and average temperature inside the collector.


Figure 17. Instantaneous efficiency for different solar collector types.

3.3.3 FLAT-PLATE COLLECTORS

As already mentioned, the flat-plate collector (FPC) is the simplest type used to transform the energy from the sun into heat. The fluid circulating in the absorber is usually water (often with additives for freeze protection) although other liquids (and even steam) can be used depending on the application and the required operating temperature. In an attempt to control heat losses, these collectors incorporate different technologies.

� Selective vs. non-selective absorbers. Radiation losses are one of the three heat losses mechanisms in solar collectors. They can be controlled by the use of so-called selective coatings applied on the absorber. These coatings are designed to have the highest possible absorption in the visible and near infrared spectra, and the lowest possible emissivity in the infrared spectra corresponding to the collector operating temperatures. Collectors using these coated absorbers are called selective and all the others, those simply painted black, are referred to as non-selective.

� Single cover / double cover; convection barriers. Another heat loss mechanism is

convection. One way to reduce convection losses is by using a double transparent cover, which is usually a transparent film placed behind the glass cover. The best material for this is Teflon, which has a high transmissivity and very good heat resistance. The use of transparent insulation materials is another possibility for high efficient stationary flat-plate collector manufacture.

3.3.4 SOLAR AIR COLLECTORS

Solar air collectors operate just like flat-plate liquid collectors but the heat transfer fluid is air instead of a liquid and a fan provokes the circulation instead of a pump. They are suitable for open systems (desiccant and evaporative cooling) but not for closed system (based on thermally driven chillers). The main advantages of this technology compared to flat-plate liquid collectors are:

� There are neither freezing problems (winter) nor overheating problems (summer).


� The system components are simpler than in hydraulic systems.

� There is no risk of liquid leakage. The main disadvantages of solar air collectors are:

� No standard heat storage units are available on the market.

� The fan electricity consumption due to pressure drops is higher than for pumps in an equivalent solar field based on liquid solar collectors.

� The efficiency of the collectors is lower than flat-plate collectors.

3.3.5 EVACUATED TUBE COLLECTORS

Evacuated tube collectors (ETC) are made up of rows of parallel glass tubes connected to a header pipe. Each single tube is evacuated in order to reduce heat losses. The tubular geometry is necessary to support the pressure difference between the atmospheric pressure and the internal vacuum. Evacuated tube collectors can be classified in two main groups:

� Direct flow tubes: the heat transfer fluid flows through the absorber � Heat pipe tubes: tubes with heat transfer between the absorber and heat transfer fluid of the

collector using the heat-pipe principle

Figure 19. Evacuated tube collector (ETC). Source: APRICUS-SOLAR

Direct flow evacuated tubes collectors

This collector consists of a group of glass tubes. Inside each tube there is a flat or curved aluminium plate which is attached to a metal (usually copper) or glass pipe depending on the configuration. The aluminium plate is generally coated with a selective coating such as Tinox. The heat transfer fluid is water and circulates through the pipes, one for inlet fluid and other for outlet fluid. There are several types of collector, classified according to the distribution of these pipes:

� Collectors with concentric fluid inlet and outlet (glass-metal): this construction has the advantage of rotational symmetry. Thus, each

inlet and

oulet pipes

absorber

inlet and

oulet pipes

absorber

Figure 20. Construction types of direct flow collectors: concentric

pipes and separated pipes.

Figure 18. Installation with solar air collectors in façade. Source: GRAMMER


single pipe can be easily rotated allowing the absorber fin to have the desired tilt angle even if the collector is mounted horizontally.

� Collectors with two separated pipes for inlet and outlet (glass-metal): this is the

traditional type of evacuated tube collector. In some cases the absorber is flat and in other cases it is curved.

� Sydney type collector (glass-glass): this collector consists of

two glass tubes fused together at one end. The inner tube is coated with an integrated cylindrical metal absorber, usually with selective absorbing material.

The first two types mentioned are very efficient at low working temperatures (heating or domestic hot water applications) but can suffer problems relating to loss of vacuum. This is primarily due to the fact that their seal is glass to metal. The heat expansion rates of these two materials are different and so after a few years of daily contraction and expansion the seal can fail resulting in a loss of vacuum. Glass-glass tubes, although generally not quite as efficient as glass-metal tubes, are generally more reliable and much cheaper. However, for some very high temperature solar cooling applications, the efficiency of glass-glass tubes can be even better than efficiency of glass-metal tubes. This depends on the technical parameters of the collector, and the working and ambient temperatures. Some evacuated tube collectors include rear mounted reflectors behind the evacuated tube collectors or inside the glass tube. The external reflectors increases the radiation received by the collector as the radiation that usually passes through the gap between tubes is driven back onto the absorber. More information about this application can be found in chapter 3.3.6.

Figure 22. Sydney type collector with CPC reflector (left). Source: MICROTHERM Energietechnik GmbH. Concentric pipes collector with

reflector inside the glass tube (right). Source SCHOTT.

Heat pipe evacuated tube collectors

The heat pipe is hollow and the space inside evacuated, much the same as the solar tube. In this case the aim is not insulation but rather a change of the state of the liquid inside. Inside the heat pipe is a small quantity of purified water and some special additives. Due to the vacuum of the tube, the water boils at a lower temperature, typically 30 ºC. So, when the heat pipe is heated above 30ºC the water vaporizes. This vapour rapidly rises to the top of the heat pipe transferring heat in the condenser. As the heat is lost at the condenser, the vapour condenses to form a liquid and returns to the bottom of the heat pipe and the process starts again. Figure 35 illustrates this process.

Figure 21. Construction types of direct flow collectors: glass-glass pipes. Source: APRICUS-SOLAR


Material quality and clean conditions are extremely important to the manufacture of a good quality

heat pipe. The presence of impurities inside the heat pipe will adversely affect performance. The purity of the copper itself must also be very high, containing only trace amounts of oxygen and other elements. If the copper contains too much oxygen or other elements, they will leach out into the vacuum forming a pocket of air in the top of the heat pipe. This has the effect of moving the heat pipe's hottest point (of the heat condenser end) downward away from the condenser. This is obviously detrimental to performance, hence the need to use only very high purity copper. Often, heat pipes use a wick or capillary system to aid the flow of liquid. This is not necessary if the interior surface of the copper is extremely smooth, allowing efficient flow of the liquid back to the bottom.

The heat pipe has two copper components, the shaft and the condenser. Prior to evacuation, the

condenser is brazed to the shaft. Note that the condenser has a much larger diameter than the shaft; this is to provide a large surface area over which heat transfer to the header can occur.

One advantage of heat pipes compared to direct flow evacuated tubes is the “dry” connection between the absorber and the header. This fact makes the installation process easier. However the collector must always be mounted with a minimum tilt angle (minimum around 25º) in order to allow the condenser internal fluid of the heat pipe to return to the hot absorber.

3.3.6 CPC TYPE COLLECTORS (STATIONARY CONCENTRATORS)

Another way to reduce the heat losses of a solar collector is to reduce the absorber area with respect to the collecting area. This works because heat losses are proportional to the absorber area and not to the collecting (aperture) area. Such concentration can be obtained using reflectors that, after one or more reflections, force the incident radiation within a certain angle (called acceptance angle) into the collector aperture in the direction of the absorber. The solar radiation concentration can be obtained by so-called non-imaging optics, where the relation between concentration and the acceptance angle (θ) is the maximum allowed by basic physical principles. In two dimensional geometry this is defined as:

( )θ=

sin

1Cmax

Figure 23. Heat pipe collector. Source: APRICUS-SOLAR

Figure 24.Detail of the connection of a heat pipe collector to the water circuit. Source:

VIESSMANN


For a fully stationary collector, θ must be large, i.e. the concentration must be low. It can be demonstrated that, for an ideal concentrator, the acceptance angle is θ = 30° and that the resultant concentration is 2. These collectors are also called CPC (Compound Parabolic Concentrator) type concentrators (see Figure 25) since a combination of parabolas was the first configuration discovered to operate on the above-mentioned limit. Mirrors are produced with the proper shape and reflect the radiation on to the absorber.

The wide acceptance angle of these devices allows them to collect both diffuse and beam radiation just like a flat-plate collector does. This is an interesting feature for this type of concentrators in comparison with tracking concentrators.

3.3.7 PARABOLIC TROUGH COLLECTORS

Solar tracking concentrators are classified depending on the way they track the movement of the sun:

� One-axis solar tracking and linear focus systems can track the sun only along its angle of elevation over the horizon.

� In two-axis tracking and point focus systems (parabolic dishes, tower plants with heliostats and solar furnaces) the sun’s rays are always perpendicular to the collector surfaces. Point focus systems are normally only used for applications requiring temperatures higher than 400 °C.

The most characteristic one axis-tracking collector is the so-called parabolic trough collector (PTC, see Figure 26). Parabolic trough collectors are the most mature concentrating solar technology to generate heat at temperatures up to 400 °C for solar thermal electricity generation or process heat applications. Reflectors with a parabolic shape concentrate direct solar radiation onto the receptor located in the focal line of the parabola. The receptor consists of an absorber tube of an area usually 25 to 35 times smaller than the aperture. The fluid to be heated is circulated through the absorber piping. Water and thermal oil are typically used as working fluids. Parabolic trough collectors have a very low thermal loss coefficient and are therefore well suited also for applications at higher temperatures. They do not use the diffuse part of the solar radiation, however they do make a better usage of the direct (beam) radiation than stationary collectors due to the sun tracking mechanism. In the U.S.A. several installations with collector areas between 500 m² and 2 500 m² have been erected during the 1990‘s. They have proved reliable in contrast to former systems. In recent years several companies have started selling parabolic trough collectors for the temperature range 50 °C - 300 °C.

Figure 25. Layout of a CPC type collector with a tubular absorber.


Figure 26. Parabolic trough collector with east-west oriented axis (left). Application of parabolic trough

collectors in industrial process (right).

3.4 ENERGY BALANCE. PRIMARY ENERGY SAVINGS AND OTHER

ENVIRONMENTAL BENEFITS

3.4.1 GENERAL ISSUES

The aim of using solar energy in air-conditioning supply is to reduce consumption of fossil fuels and electricity. It means reducing primary energy consumption and the associated polluting atmospheric emissions. Therefore, the energy performance of solar assisted air-conditioning systems is one of the main parameters that define their value. Achieving this value usually involves additional capital investment relative to conventional technologies. However, the resultant energy savings reduce energy costs and these contribute to the recovery of the initial extra-cost of the installation. This chapter offers some guidelines for the assessment of the energy and environmental performance of solar assisted air-conditioning systems. Economic factors are presented on the next chapter.

3.4.2 PRIMARY ENERGY SAVINGS

The common strategy used to assess the energy performance of a solar assisted air-conditioning system is to compare its primary energy consumption with that of a conventional system (a system using only fossil fuels and electricity to supply the same load in the same climatic conditions). Another important possibility to consider when calculations are made is the use of year long operation simulations. The maximum time step recommended is one hour due to the need to consider solar radiation variability, climatic conditions and load throughout the year. When designing an installation, the objective is to understand the most unfavourable conditions. Here in contrast, when assessing energy performance, the objective is to determine the behaviour of the system over time. In order to carry out these calculations it is necessary to use simulation programs or similar tools, both for load determination and for energy performance of the installation. The main parameters that are calculated in an annual energy balance are as follows:


� Load for heating, cooling and other thermal uses � Solar production

− Solar heat production − Heating (and other heat uses) produced by solar system − Cooling produced by the solar system12 − Gross solar system efficiency − Net solar system efficiency − Solar heating fraction − Solar cooling fraction

� Fossil fuels and electricity consumption − Electricity consumption for heating (and other heat uses) − Electricity consumption for cooling − Fossil fuel consumption for heating (and other heat uses) − Fossil fuel consumption for cooling − Boiler efficiency − COP of electrically driven compression chiller − COP of thermally driven chiller

� Primary energy − Primary energy consumption − Primary energy savings − Relative primary energy savings − Specific solar heat production (per unit of collector surface) − Specific primary energy savings (per unit of collector surface)

Although not indicated in the previous list, it is also important to assess the water consumption of the system. In installations where cooling towers or humidifiers are used, consumption is usually higher than in a conventional installation. The following table details the main equations needed to assess the energy performance.

12 The “solar system” includes all the equipment from solar collector to solar storage and excludes the boiler back-up (if there is one).


Table 2. Energy performance equations in a solar assisted air-conditioning system

concept equation parameters used

Solar heat production (absolute and specific) butotuse QQQ −=

col

useuse A

Qq =

Quse: useful heat from solar system.

Qtot: total heat required for heating and cooling; in case of cooling it is considered to be the corresponding heat in the generator of the thermally driven chiller or the regeneration heat needed in the DEC system.

Qbu: heat produced by a back-up system (boiler).

Acol: solar collector surface (absorber).

Gross solar system efficiency

colcol

solgross IA

Q

⋅=η

Qsol: production from solar system after the storage tank

Icol: solar radiation received by the collector plane.

Net solar system efficiency

colcol

usenet IA

Q

⋅=η

Process quality number

1

1

_

_

−

−==

cold

rejectionheat

driving

rejectionheat

eq

Carnot

eq

T

T

T

T

COP

COP

COPPQN

Solar COP netthermalsolar COPCOP η*=

Primary energy consumption

elec

elec

fossilbu

buPE

EQE

εεη+

⋅=

Eel: electricity consumed in the installation (electrically driven compression chiller, fans, pumps, cooling tower, etc.).

ηbu: efficiency of the back-up system (boiler).

εfossil: primary energy conversion factor of the fossil fuel used for the back-up heat source (gas, oil, etc).

εelec: primary energy conversion factor of the electricity.

Primary energy savings (absolute, relative and specific)

solarPErefPEPEsave EEE −=

PEref

PEsaverelPEsave E

EE =−

col

PEsaverelPEsave A

EE =−

EPEref: primary energy consumption by the reference system, which uses fossil fuels and electricity.

EPEsolar: primary energy consumption by solar assisted air-conditioning system.


The difference between the gross solar system efficiency and the net solar system efficiency shows the amount of solar energy that cannot be used as there is no demand for solar heat, neither for heating nor for cooling. The primary energy conversion factors consider the efficiency of the different transformation and transport processes used to change energy from the state in which is “naturally” present to the state of its final use by the installation equipment. In the case of the fossil fuels, losses in the extraction process from the oilfield (or gas field), in refinery processes and in transportation are considered. The usual values for εfossil: are in the range 0.95 - 0.90 kWhfossil/kWhPE. In the case of electricity the efficiency of the generation plant must also be considered. One calculation methodology used considers the total electricity produced in a country and its distribution accounting for the different technologies and their associated efficiencies (conventional, fossil fuel or nuclear fuelled, thermal electricity plant, combined-cycle plant, cogeneration plant, hydroelectric plant and other renewable energy plant). The usual values for εelecl: are between 0.3 and 0.4 kWhelec/kWhPE.

3.4.3 SPECIFIC PRIMARY ENERGY ANALYSIS

In general, the primary energy consumption of solar assisted air-conditioning systems can be compared with conventional air-conditioning systems considering the specific primary energy consumption parameters or, in other words, by referring to a unit of cold production. In this case, the formulae to be considered are as follows:

Table 3. Specific primary energy comparison between solar assisted air-conditioning systems and conventional air-conditioning systems

concept equation parameters used

Specific primary energy consumption of a conventional chiller convelec

convspc COPPE

⋅=− ε

1

COPconv: relation between the cold produced and the electricity consumed in a conventional chiller.

εelec: primary energy conversion factor of the electricity.

Specific primary energy consumption of a thermally driven chiller supplied by solar energy and fossil-fuelled boiler as back-up ( ) cooltowspccool

thfossilbusolspc

PESF

COPPE

−

−

+−

⋅⋅⋅

=

1

1

εη

ηbu: efficiency of the back-up system (boiler).

εfossil: primary energy conversion factor of the fossil fuel used for the back-up heat source (gas, oil, etc).

COPth: relation between cold produced and thermal energy consumed in a thermally driven chiller.

SFcool: solar fraction for cooling.

PEspc-cooltow: specific primary energy consumption of the cooling tower.

Specific primary energy consumption for the cooling tower

⋅+⋅= −

−thelec

cooltowspccooltowspc COP

EPE

11

ε

Espc-cooltow: specific electricity consumption of the cooling tower per unit of heat rejected (including circulation pump).


It is assumed that the COPconv takes into account the average electricity consumption, including the electricity needed for heat rejection at the condenser. The figures shown are valid for a system with a thermally driven chiller with a back-up, fossil-fuelled, boiler able to cover the peak cooling load. In order to compare a desiccant cooling unit, the conventional system for reference should be a conventional air-handling unit with a vapour compression chiller for cooling production (sensible and latent load). In desiccant cooling systems there is no cooling tower but the electricity consumed by fans must be taken into account as this is usually higher in solar systems than in conventional systems. An example of this kind of analysis has been calculated for a thermal driven chiller supplied by solar energy and by a natural gas boiler in comparison with an electrically driven vapour compression chiller taking into account the following hypothesis: Espc-cooltow=5 % ηbu=0.85 εfossil=0.95 εelec=0.34 SFcool=0 % - 100 % COPth=0.5 – 0.8 COPconv=2.0 – 4.5

Figure 27. Specific primary energy consumption depending on solar fraction for a several cooling systems

The results shown in the previous graph show that if the solar assisted air-conditioning system is compared with a conventional air-conditioning system with a high COP, only a high solar fraction should be accepted. For instance, consider a COPth of 0.7. Compared to a conventional system with a COPconv of 2.0, a solar system with solar cooling fraction of 35 % or more consumes less primary energy than this conventional system. However, if the reference system is one with a COPconv of 4.5 the solar system only consumes less if the solar cooling fraction is higher than 85 %. The same solar system with a COPth of 0.7 and a solar fraction of 70 % has a primary energy consumption of 0.89 kWhPE/kWhcold. This figure is 40 % lower than the corresponding consumption for a conventional system with a COPconv of 2.0, but 36 % higher than the corresponding consumption for a conventional system with a COPconv of 4.5.

0.000

0.500

1.000

1.500

2.000

2.500

3.000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Solar Fraction Cooling

PE

spc

sol/c

on

v (k

Wh

PE

/kW

hco

ld)

COP 0.5 COP 0.55 COP 0.6 COP 0.65 COP 0.7

COP 0.75 COP 0.8 COPconv 2.0 COPconv 4.5


The analysis shows that it is necessary to reach a certain solar fraction value in order to have a solar assisted air-conditioning system (based on thermally driven chiller with fossil-fuelled boiler as back-up) that operates with a lower primary energy consumption than a conventional system (based on a electrically driven vapour compression chiller). The system performance with regard to primary energy consumption improves when either the COPth or the solar fraction increases and the specific electricity consumption in the cooling tower decreases. If the system is designed so that there is no back-up boiler for the thermally driven chiller (that is to say the cooling capacity is divided between the thermally driven chiller only supplied with solar energy and an electricity driven vapour compression chiller) the minimum solar fraction is not limited.

3.4.4 ENVIRONMENTAL BENEFFITS

Solar assisted air-conditioning systems have lower environmental impact than conventional air-conditioning systems. The main factors for this are as follows: • The lower primary energy consumption of an energy system, the lower the CO2 emissions. • Solar assisted air-conditioning system use only harmless substances such as water or salts

instead of CFC or HCFC refrigerants. The values of the avoided CO2 emissions are proportional to the reductions in fossil fuel or electricity consumption. In the case of electricity, the precise value depends on the distribution of the technologies that contribute to the total amount of electricity production (as explained in Chapter 3.4.2). In this case, nuclear power and renewable energy sources have no associated CO2 emissions. In the case of fossil fuels, the values of CO2 are those emitted during the combustion process. Some reference values for electricity conversion to CO2 emissions are as follows. In Spain, the emissions are given as 0.455 kg CO2 per kWh of electricity, and 0.2 kg CO2 per kWh of natural gas. One disadvantage of some solar assisted air-conditioning systems is an increase in water consumption related with the use of cooling towers or humidifier. This issue must be assessed also in the design of the systems together with the energy balance.

3.5 ECONOMICS: INVESTMENT AND OPERATION COSTS

Solar assisted air-conditioning systems operate in a pioneers’ market. They are not fully economically competitive with systems that use conventional energy sources (fossil fuels and electricity). This is mainly due to two factors. Firstly, despite the technical maturity of the systems, in terms of air-conditioning installation supply requirements, the investment cost of the various components in solar cooling units (solar collectors, desiccant rotor, adsorption chillers, etc.) is much higher than conventional system components. Secondly, conventional fuel prices do not take into account the environmental and social costs of fossil fuels and electricity. Economic comparisons of solar assisted and conventional systems in these circumstances almost inevitably conclude that the cost of solar assisted air-conditioning systems is unfavourable. Therefore, public subsidies are necessary to make the implementation of most installations feasible.


When a solar assisted air-conditioning system is planned, the economics of the system should be compared with a reference installation based on conventional systems in order to assess the economic value, as it has been shown for the energy balance (see Chapter 3.4). The parameters that must be included in an economic balance are the following:

� Investment costs − Material costs of each sub-system of the installation − Costs of accessories, valves, pipes, pumps, etc − Control system costs − Labour costs − Engineering works costs − Subsidies (to be subtracted from the total costs)

� Annual costs − Capital cost − Electricity cost (consumption) − Electricity cost (peak) − Fossil fuel cost (consumption) − Fossil fuel cost (fixed) − Water cost − Maintenance cost

An annuity factor is used in order to calculate the annual capital cost of the initial investment. To calculate the cost of energy and water, the annual consumption figures from the energy balance are used considering prices for electricity and fossil fuels and water. The total investment costs and the total annual cost are calculated by summing all the subjects included in each list. The following formula can be used to calculate the economic performance of both the solar assisted system and the conventional system.


Table 4. Economic balance equations in a solar assisted air-conditioning system

concept equation used parameters

Annual extra-cost of solar system refannualsolannualsolannual CCC −−− −=∆

Cannual-sol: annual costs of the solar assisted air conditioning system.

Cannual-ref: annual costs of the conventional system.

(capital, fuels, water and maintenance included)

Annual saving of operation and maintenance of solar system

solannualoprefannualopsolannualop CCC −−−−−− −=∆ Cop-annual-sol: annual costs of operation the solar assisted air conditioning system.

Cop-annual-ref: annual costs of operation of the conventional system.

Pay-back time

solannualop

refinvestsolinvestpayback C

CC

−−

−−

∆−

=τ Cinvest-sol: total investment cost of the solar assisted air conditioning system.

Cinvest-ref: total investment cost of the conventional system.

Cost of saved primary energy

savedPE

solannualsavedPE E

CC

−

−−

∆= EPE-saved: primary energy saving of the solar system compared to the reference system.

The payback time is significant when the operational costs of the solar assisted air-conditioning system are lower than the operational costs of the reference system. The parameter of cost of saved primary energy has the advantage of referring to the difference in annual cost due to the energy savings. In this way, the higher the primary energy savings, the lower the cost of it, instead of the extra-costs of the solar assisted system. This second parameter indicates the cost of saving one unit of primary energy. It is a good figure for comparing different configurations of the solar assisted air-conditioning system (varying solar surface, storage capacity, etc) or different energy saving measures such as passive cooling techniques or other conventional systems that improve the energy performance although they do not use solar energy.


4 BEST PRACTICES

The following reference cases have been included in this chapter:

- Cooling in wine cellar in Banyuls, France - Cooling in wine cellar Peitler, Austria - Process cooling in Fontedoso, Spain - Process cooling in Sarantis, Greece - Cooling in Brisa building, Portugal - Cooling in domain Neferis, Tunisia - Cooling in Ipswich Hospital, Australia

WINE CELLAR BANYULS52 kW cooling and 130 m2 vacuum tubes collectors

DATA SOURCEThe data provided come from SOLAIR PROJECT where were provided from Mr. Daniel Mugnierfrom TECSOL (Perpignan, France). For additional information use [email protected]

The system is in operation since 1991.

BUILDINGBUILDING DESCRIPTION

The building type is a wine cellar with a 4 500 m2 of cooled area (15 000 m3 of cooled volume).The building construction can be assessed as with heavy inertia.

HEAT IS REQUIRED FORThe heat is required for space cooling only. The peak cooling load is 52 kW. The use of cooling is from may to september.

BUILDING FACILITIESThe buiding has a mechanical centralized ventilation system of 25 000 m3/hThe cooling system distribution is based on fan coils that operates between 10ºC and 14ºC

2 Building 1 BANYULS

COOLING STRATEGYThe cooling strategy is based on solar alone (no back up)

PROCESSPROCESS DESCRIPTION

The cooling process is used to cool the areas where the bottles of wine are stored

PROCESSES SUPPLIED BY SOLAR THERMAL SYSTEM

Processes 1 2 3

Process space cooling

Type of process (*) space cooling

Continous / Batch continous

Operating hours per day daily

Exit temperature of the network(°C) 30 ºC

Temperature of process (°C) 10 ºC

Useful heat demand ( MWh / year) 2240 (**)(**) period 31/08/2007 - 09/09/2007

(*) Types of processesSpace cooling Sterilisation Washing, dyeing, bleaching Hot water Space heating Pasteurisation Preheating of boiler feed-water DegreasingWort boiling Scalding Drying Spinning and weavingBottle washing Paint drying Cooking Paper pulp cookingOther :

Operating days per year: 150 d/ year

ANNUAL USEFUL HEAT DEMAND : MWh/year (**)2240


HEAT SOURCESCOLLECTORS

The collector array has a surface of 130 m2 (absorber area) of vacuum tubes with water as medium flowThe model is CORTEC 2 and the manufacturer is GIORDANO INDUSTRIES (France)The installation was done in a tilt roofThe control of the system is based on high flow.

SOLAR HEAT STORAGEThere is a single tank of hot water with a total volume of 1 m3.

AUXILIARY HEATING SYSTEMThere is no auxiliary heating system

COOLING EQUIPMENTThe cooling equipment are two absorption chillers with a total capacity of 52 kW with nominal COP of 0.7The distributed medium temperature is 10 ºC and the nominal driving heat temperature is 85 ºC.The model is WFC 7.5 and the manufacturer is YAZAKI (Japan)The absorption chiller is driven only by solar thermal heat

HEAT REJECTIONThe heat rejection is done with a wet cooling tower with a total capacity of 180 kWThe nominal electricity consumption is 1.5 kWThe model is PMS 9-130 and the manufacturer is MITA (Italy)

BACK-UP CHILLERThere is no back-up chiller

COLD STORAGEThere is no cold storage

RESULTS FROM SYSTEM OPERATIONENERGY INPUTS

Radiation gain (collector surface): 6910 kWh/m2

Useful energy from collector in TDC: 3699 kWh Driving heat input in TDC: 3699 kWhProduced cold: 2240 kWh


Rejected heat: 7317 kWhThermal coefficient of performance (COP_thermal): 0.61Solar coverage of cooling demand: 100 %

Useful energy from collector for other thermal uses: 0 kWhSolar coverage of other thermal uses: 0 %

Produced cold with vapour compression chiller: - kWhElectricity input: - kWhCoefficient of performance (COP_electric): -

Auxiliary electricity consumption: 0 kWh

Data corresponding to the period: 31/08/2007 - 09/09/2007

COMMENTS

COSTSTotal investment costs: €Specific costs: 1686 €/m2

4216 €/kWDistribution of PLANT costs

Solar collectors: 70 %Cold production and recooling: 21 %Back-up cold and hot: 0 %Storage: 1 %Electricity, control and monitoring: 8 %

Planning and commissioning costs 7880Distribution over PLANT costs 4 %

Annual costsOperation: n.a. €/year

n.a. €/m2

n.a. €/kWMaintenance: 1740 €/year

13 €/m2

33 €/kW

Year of reference 1991

Percentage of plant turnover (energy costs) n.aPercentage of savings over total plant turnover n.a

FINANCINGEU subsidies

219210

The primary loop pump is widely oversized because designed at the origin to vehiculate antifreezing fluid. The control of this pump is based on the signal of a crepuscular sensor (the pump is on an averag of 12 hours/day in summer period). These two facts lead to a electric COP which is of nearly 4,7 and which could be close to 8 if the pump would be replaced and if a irradiance sensor would be used for the control.

EU subsidiesNational subsidies 20%Regional subsidies 17%Other subsidiesUser cash 63%User loan


SCHEME OF THE SYSTEM

1 BANYULS5 System Scheme

COMMENTS

The system was intially designed with a plate heat exchanger between the collectors and the storage so that it can work in winter with anti freezing fluid. In 1995, the heat exchanger has been replaced by a 3 way valve and all the fluids are water


GENERAL USER REACTIONS

GENERAL ASSESSMENT

The user is completely satisfied with the installation. He has been involved particularly in comunication anddissemination of the project

This system has a good adequation between solar production and cooling load of the 3 storage levelsof the building. Therefore the confort requirements are succesfully reached.

A lot of different articles, reports on TV and publicationcustomer. The user is also using the system as a mar

PERFORMANCE ASSESSMENT

The user is satisfied with the performance and do not need any back-up.

The system is completely reliable. There have not been major troubles in the system since 1995

9 Qualitative assessment 1 BANYULS

This installation is a very good success for the end user. The solar cold production is in adequation with the load of the building : decrease the temperature increase in the wine cellar

y p y j y

No nuisance problem have been detected along the operation of the plant

There is the following potential of the optimisation: it could be changed the primary loop pump controlwith a crepuscular sensor by a irradiation sensor to decrease the electric COP of the system


MAJOR LESSONS LEARNT


View of the building with the system

10 Figures, Fotos 1 BANYULS

Absorption chiller

Technical premises with the buffer storage

Cooling towerPictures from TECSOL courtesyPictures from TECSOL courtesy

WINE CELLAR PEITLER10 kW cooling and 100 m2 flat-plate collectors

DATA SOURCEThe data provided come from ROCOCO PROJECT where were provided from Mr. Reinhard Ungerböckfrom CONNES (Graz, Austria). For additional information use [email protected]??



The building type is a wine cellar with a 100 m2 of cooled area (250 m3 of cooled volume).The building construction can be assessed as with heavy inertia.

HEAT IS REQUIRED FORThe heat is required for space cooling and process coolingThe use of cooling is from may to october.

BUILDING FACILITIESThe buiding has a mechanical centralized ventilation system The cooling system distribution is based on fan coils that operates between 10ºC and 16ºC and air-distribution system.

2 Building 2 PEITLER

COOLING STRATEGYThe cooling strategy is based on full air-conditioning system (solar+back-up)




Processes 1 2 3



Continous / Batch continous n.a.

Operating hours per day daily n.a.

Exit temperature of the network(°C) 16 ºC 10 ºC

Temperature of process (°C) 10 ºC 5 ºC

Useful heat demand ( MWh / year) n.a. n.a.


Operating days per year: 180 d/ year space cooling60 d/ year process cooling

ANNUAL USEFUL HEAT DEMAND : MWh/year

process cooling

process cooling

n.a. y



The collector array has a surface of 100 m2 (absorber area) of flat-plate collectors with water as medium flowThe model is ÖKOTECH and the manufacturer is ÖKOTECH (Austria)The installation was done in a tilt roof (40º)

SOLAR HEAT STORAGEThere is a two tanks of hot water with a total volume of 2 m3. These are placed indoor.

AUXILIARY HEATING SYSTEMThere auxiliary heating system has a external exchanger (direct type) and a woodchips boiler of 40 kW.

COOLING EQUIPMENTThe cooling equipment is one absorption chiller with a total capacity of 10 kWThe chillers has H2O as absorbent and NH3 as refrigerantThe model is PINK and the manufacturer is PINK (Austria)The absorption chiller is driven by solar heat power in a fraction of 80-85 %

HEAT REJECTIONThe heat rejection is done with a wet cooling tower with a total capacity of 30 kWThe nominal electricity consumption is 0.8 kWThe manufacturer is BALTIMORE AIRCOIL (U.S.)

BACK-UP CHILLERThere is no back-up chiller

COLD STORAGEThere is an horizontal tank of water of 500 liters and a nominal exchange temperature of 5 ºC


Radiation gain (collector surface): n.a kWh/m2

Useful energy from collector in TDC: n.a kWh Driving heat input in TDC: n.a kWhProduced cold: n a kWh


Produced cold: n.a kWhRejected heat: n.a kWhThermal coefficient of performance (COP_thermal): n.aSolar coverage of cooling demand: n.a %

Useful energy from collector for other thermal uses: n.a kWhSolar coverage of other thermal uses: n.a %

Produced cold with vapour compression chiller: n.a kWhElectricity input: n.a kWhCoefficient of performance (COP_electric): n.a

Auxiliary electricity consumption: n.a kWh

Data corresponding to the period:

COMMENTS

COSTSTotal investment costs: €Specific costs: €/m2

€/kWDistribution of PLANT costs

Solar collectors: n.a %Cold production and recooling: n.a %Back-up cold and hot: n.a %Storage: n.a %Electricity, control and monitoring: n.a %

Planning and commissioning costs n.aDistribution over PLANT costs n.a %


n.a. €/m2


n.a €/m2

n.a €/kW

Year of reference n.a


FINANCINGEU subsidies 40%N ti l b idi

n.an.a

National subsidiesRegional subsidies 35%Other subsidies (private) 10%User cash 15%User loan



PEITLER5 System Scheme 2

COMMENTS

In modern winery, large stainless steel tanks are filled with the grape juice. The following processes need of coolingFermentation of the grape juice.- to reach higher quality in wine, the fermentation process that is exothermal, can be controlled by cooling of the grape juice in the steel tanks. The recommended temperature of the grape juice shouldbe kept at 17-18 ºC during the fermentation.Tartar (wine cristal) extraction.- after the fermentation of the grape juice the tartar is extracted by cooling down the wine in th large tanks until 3 ºC. The cristals sinks to the bottom of the tanks and the wine is stabilized and ready to be bottled and storaged.Cooling and dehumidification of wine bottle storage.- space cooling in the place where wine bottles arestored is necessary to keep the best conditions of humidity and temperature for the wine.

The NH3-absorption-chiller used in this installation was specially made for this plant. This is a solar and/orbiomass driven chiller.The generator is divided in two sections. One is for lower temperatures of the solarheat storage and the other is for conventional heat comming from the biomass burner. The falling film technology of the generator allows the easy integration of this design principle.



GENERAL ASSESSMENT

No problems so far, site runs almost automatic, only 3 incidents.


Only 3 incidents that have been solved.

9 Qualitative assessment 2 PEITLER

The system runs properly. There has been increased selling of wine through interested (technical educated) visitors





10 Figures, Fotos 2 PEITLER

PROCESS COOLING FONTEDOSO105 kW cooling and 470 m2 flat-plate collectors

DATA SOURCEThe data provided come from ROCOCO PROJECT where were provided from FONTEDOSO (El Oso, Spain).

The company ABSORSISTEM (distributor of YAZAKI chillers) also provided information about this installation. For additional information use [email protected] system is working since 2002.


The building type is a factory of bottling water for human use.

HEAT IS REQUIRED FORThe heat is required for heating water for cleaning the bottling circuit, cooling of molding process of plastic botles, space cooling and space heating of offices of the industry

BUILDING FACILITIESThe facilities are divided in three systems:- solar thermal plant that provides heat to heating water for cleaning and space heating of offices- absorption chiller that provides cooling of molding process and space - back-up system based on gasoil boillerThe cooling system distribution is based on fan coils, for the space coolingThe building surface that requires heating or cooling has 140 m2

COOLING STRATEGY

2 Building 3 FONTEDOSO

The cooling demand is covered by absorption chiller which is fired by hot water that comes from solarplant or from back-up boiler.Three heat exchangers separates the processes from the energy plant (heating for industrial cleaning,space heating and cooling).


The industrial process of bottling water for human use requires a careful cleaning, rinsing anddisinfection process. This is done with water at 85 ºC. Also the plastic bottles are made using molds that need to be cooled. The other thermal processes are the space heating and the space coolingof offices.


Processes 1 2 3 4


Type of process (*) space cooling cooling space heating heating

Continous / Batch from may to septem ? from october to april continous

Operating hours per day n.a 8 n.a 8

Exit temperature of the network(°C) n.a n.a n.a 85

Temperature of process (°C) n.a n.a n.a n.a

Useful heat demand ( MWh / year) n.a 218 n.a 124


Operating days per year: n.a d/ year

cooling molds heating washing, disinfection

ANNUAL USEFUL HEAT DEMAND : MWh/yearn.a



The collector array has a surface of 470 m2 (absorber area) of flat plate collectors with transparent isolation TIMThe model is MADE-5000-ST and the manufacturer MADE (UNISOLAR)The installation was done in a tilt roof (30º)The medium of heat transfer is water+glicol

SOLAR HEAT STORAGEThere are three tanks of hot water. For industrial washing 10 m3, for cooling 15 m3 and for heating 5 m3.

AUXILIARY HEATING SYSTEMThere is auxiliary heating system with an oil boiler of 400 kW and 3 auxiliary tanks (7.5 m3, 7.5 m3 and 2.5 m3)

COOLING EQUIPMENTThe cooling equipment are two absorption chillers with a total capacity of 100 kW with nominal COP of 0.7The models are WFC SC20 and WFC SC10 and the manufacturer is YAZAKI (Japan)

HEAT REJECTIONThe heat rejection is done with a wet cooling tower.

BACK-UP CHILLERThere is no back-up chiller.

COLD STORAGEThere is cold storage with a tank of 1 m3.


Radiation gain (collector surface): n.a kWh/m2

Useful energy from collector in TDC: n.a kWh Driving heat input in TDC: n.a kWhProduced cold: n.a kWhRejected heat: n.a kWhThermal coefficient of performance (COP_thermal): n.a

2 Building 3 FONTEDOSO

Solar coverage of cooling demand: n.a %

Useful energy from collector for other thermal uses: n.a kWhSolar coverage of other thermal uses: (industrial washing and space heating) 65 %




COMMENTS


3,761 €/kWDistribution of PLANT costs




n.a. €/m2

n.a. €/kWMaintenance: n.a €/year

n.a €/m2

n.a €/kW

Year of reference


FINANCINGEU subsidies n.aNational subsidies 36%Regional subsidies 18.5%

376,099

gOther subsidies n.aUser cash User loan n.a

45.50%


SCHEME OF THE SYSTEMn.a.

3 FONTEDOSO5 System Scheme

COMMENTS

The storage tanks of 10 m3 and 15 m3 must be appropriate for the food industria and have interaction with the bottles that are for human use. Then the material used is stainless steel. The isolation is of 0.1 m thickness.The three heat exchangers has a total capacity of 300 kW.



GENERAL ASSESSMENT


9 Qualitative assessment 3 FONTEDOSO




View of collectors field and cooling tower

10 Figures, Fotos 3 FONTEDOSO

View of absorption chillers

Pictures with courtesy of ABSORSISTEM S.L.

Cosmetic Factory Sarantis S.A.700 kW cooling and 2700m² flat plate collectors

DATA SOURCEThe data provided come from reports for operation of the constructor of the systemand from the Procesol project reports



The building type is a warehouse of cosmetic company. The airconditioned space is 22,000m² (130,000m³)

HEAT IS REQUIRED FORThe solar system provides heating and cooling of the new buildings and warehouse of the company

BUILDING FACILITIESThe system provides hot water of 55°C (for heating) or 8-10°C (for cooling)Air handling units and fan coils are used to condition the air

COOLING STRATEGY

2 Building 4 SARANTIS

COOLING STRATEGYSince the load can be very high, 3 conventional electric coolers of 350 kfor peak load coverage. 2 oil boillers (1200kW each) supply hot water whenever required for the operation both of the chillers during the night period and the heting when there is cloudiness.


The cooling process is used to cool the warehouse and the offices of the buildingThe heating process is used to heat the warehouse and the offices of the building and for DHW


Processes 1 2 3

Process space cooling space heating

Type of process (*) space cooling space heating

Continous / Batch continous continous

Operating hours per day daily daily

Exit temperature of the network(°C) 25°C 25°C

Temperature of process (°C) 7-12 ºC 45-40°C

Useful heat demand ( MWh / year) 740 1200



ANNUAL USEFUL HEAT DEMAND : MWh/year1940



The collector array has a surface of 2664 m² of selective flat plate collectors with water as medium flowThe model is CLIMASOL 2 and the manufacturer is SOLE S.A. (Greece)The installation was done in a field next to the building

SOLAR HEAT STORAGE3000lt buffer tank

AUXILIARY HEATING SYSTEM2 diesel-oil boillers of 1000kW each for solar collectors' backup

COOLING EQUIPMENTThe cooling equipment are two adsorption chillers with a total capacity of 700 kW with nominal COP of 0.6The distributed medium temperature is 8-10 ºC and the nominal driving heat temperature is 70-75 ºC.The Adsorption chillers were the NAK of the German company GBU The adsorption chillers are driven by solar thermal heat and the backup boilers

HEAT REJECTIONThe heat rejection is done with 2 wet cooling tower with a total capacity of 1000 kWThe two cooling towers are made by BAC (Belgium)

BACK-UP CHILLER3 350kW compression chillers used to cover the peak cooling demand

COLD STORAGEThere is no cold storage



Useful energy from collector in TDC: 1719 MWh Driving heat input in TDC: 1719 MWhProduced cold: 1090 MWh

2 Building 4 SARANTIS

Rejected heat: kWhThermal coefficient of performance (COP_thermal): 0.6Solar coverage of cooling demand: 52 %

Useful energy from collector for other thermal uses: 629 MWhSolar coverage of other thermal uses: 51 %


Auxiliary electricity consumption: - kWh

Data corresponding to the period: 1999-2004

COMMENTS

COSTSTotal investment costs: €Specific costs: 528.8 €/m2


Solar collectors: - %Cold production and recooling: - %Back-up cold and hot: - %Storage: - %Electricity, control and monitoring: - %

Planning and commissioning costs -Distribution over PLANT costs - %


n.a. €/m2


9.384 €/m2

35.71 €/kW



FINANCINGEU subsidies

1408657

The primary loop pump is widely oversized because designed at the origin to vehiculate antifreezing fluid. The control of this pump is based on the signal of a crepuscular sensor (the pump is on an averag of 12 hours/day in summer period). These two facts lead to a electric COP which is of nearly 4,7 and which could be close to 8 if the pump would be replaced and if a irradiance sensor would be used for the control.

National subsidies 0%Regional subsidies 50%Other subsidiesUser cash 50%User loan



4 SARANTIS5 System Scheme

COMMENTS

Cosmetic Factory Sarantis S.A700 kW cooling and 2700m² flat plate collectors


GENERAL ASSESSMENT


The user is very satisfied with the performance

The system is completely reliable. There have not been major troubles in the system since 2000

9 Qualitative assessment 4 SARANTIS

This installation is a very good success for the end user. The solar cold production covers the base load of the building

The owners of the building are very satisfied by all aspects of their investment, i.e. financial, environmental, etc., they also believe that the whole project contributes to the ecological image of their company to their clients, employees, the government and the public

The project has been awarded by “Energy Globe Award 2001”as the world’s third best investment for sustainable energy in the year 2001 and by CRES in Greece (Centre for Renewable Energy Sources) as the best investment in Greece for the year 1999.

y p y j y


CO2SO2CONOXHC

Parti


There is the following potential of the optimisation: to install a heat exchanger between the collectors and the heating system (for heating period) in order to ease the maintenance of the collector field (but this would reduce the solar performance by a small amount)

5.124.596 kg/year89.268 kg/year

There has been a problem with water leacakge dwe to large expansions of the collector field, so measures taken was to install 2 (two) more suitably designed expansion joints on each group of 18 collectors. The groups are 74 so 148 new expansion joints were created.

After shutdown and emptying the collectors’ field in Christmas 2003, and with very cold weather of minus 20oC 30 collectors were “broken” from freezing. This meant that these collectors were not fully drained due to the poor emptying behavior. The emptying behavior of the collectors’ field was improved by installing one manual drain valve at the lowest position of each group of 18 collectors, making it a total of 74 drain valves.

1.076 kg/year201.216 kg/year

302 kg/year4.606 kg/year

Cosmetic Factory Sarantis S.A700 kW cooling and 2700m² flat plate collectors



10 Figures, Fotos 4 SARANTIS

Collector Field

2 Adsorption Chillers

Cooling Towers

Domain Neferis Winery13 kW cooling and 88 m2 fresnel collectors

DATA SOURCEThe data provided come from MEDISCO PROJECT where were provided from Mr. Alberto Maurofrom Politecnico di Milano (Milan, Italy). For additional information use [email protected]

The system is in operation since 2008

PlantPLANT DESCRIPTION

The Plant have 23 wine storage tanks The building construction can be assessed as with heavy inertia.

HEAT IS REQUIRED FORthe production process requires a considerable amount of cool energy at temperatures ranging from 0 to 20° C. The production phases during which a considerable amount of cool energy is required are:· Grapes pre-cooling· Must clarification · Must fermentation · Must storage

PLANT FACILITIES· 1 wine press · 1 stemmer· 2 heat exchangers· 23 wine storage tanks

2 PLANT 6 Tunisia

COOLING STRATEGYThe solar cooling system is supposed to cover one third of the cooling load of three wine storage tanks.




Processes 1 2 3

Process storage tank cooling

Type of process (*) Process cooling

Continous / Batch batch

Operating hours per day vary accordiing to load profile

Exit temperature of the network(°C) variable -5 to +5

Temperature of process (°C) variable; depends ontype of process

Useful heat demand ( MWh / year) ---



ANNUAL USEFUL HEAT DEMAND : MWh/year (**)



The collector array has a surface of 88 m2 (absorber area) of fresnel collector with water as medium flowThethe manufacturer is PSE (Germany)The installation was done on groundThe control of the system is based on high flow.

SOLAR HEAT STORAGEThere is a no hot storage due to the high temperature and pressure of the fluid in the primary loop

AUXILIARY HEATING SYSTEMThere is no auxiliary heating system

COOLING EQUIPMENTThe cooling equipment are one single effect absorption chillers with a nominal capacity of 13 kW with nominal COThe distributed medium temperature is -4 ºC and the nominal driving heat temperature is 120-180 ºC.The model is ACF 60-00 LB and the manufacturer is Robur (Italy)The absorption chiller is driven only by solar thermal heat

HEAT REJECTIONThe heat rejection is done with the chiller internal dry cooler.

BACK-UP CHILLERThere is an existing chiller with the capacity of 800 kW.

COLD STORAGE3000 L water-glycol cold storage



Useful energy from collector in TDC: - kWh Driving heat input in TDC: - kWhProduced cold: - kWh

2 Building 6 Tunisia

Rejected heat: - kWhThermal coefficient of performance (COP_thermal): -Solar coverage of cooling demand: - %

Useful energy from collector for other thermal uses: 0 kWhSolar coverage of other thermal uses: 0 %


Auxiliary electricity consumption: 0 kWh

Data corresponding to the period: 17/06/2008 - 25/06/2008

COMMENTS



Solar collectors: 33.3 %Cold production and recooling: provided from project partnerBack-up cold and hot: 0 %Storage: 5 %Electricity, control and monitoring: 16.7 %

Planning and commissioning costs -Distribution over PLANT costs - %


n.a. €/m2

n.a. €/kWMaintenance: - €/year

- €/m2

- €/kW



FINANCINGEU subsidies 50%

120000

The data we have for the system operation is for the preliminary operation and the reliable operation data will be available soon.

National subsidies 50%Regional subsidiesOther subsidiesUser cash User loan



6 Tunisia5 System Scheme



GENERAL ASSESSMENT

The end user is a partner of the project, and showed a high interst in the installation and technology.


The system is operating since the beggining of June 2008 and no assessment has been done yet.

This installation is a very good success for the end user. The solar cold production is in adequation with the load of the building : decrease the temperature increase in the wine cellar

9 Qualitative assessment 6 Tunisia




View of the plant

10 Figures, Fotos 6 Tunisia

Top view of the system

Absorption chiller with pump and flow meter

cold storage

control panel

Load side- wine storages

Pictures from Polimi courtesyPictures from Polimi courtesy

HOSPITAL ISPWICH (AUSTRALIA)300 kW cooling and 570 m2 tracking parabolic collectors

DATA SOURCEThe data provided come from Task 38 "Solar air conditioning and refrigeration"- subtask B ofSolar Heating and Cooling (SHC) Programme of Internation Energy Agency (IEA)The plant was commissioned by Energy Conservation Systems (ECS), one of the companies partneringQueensland Health’s Eco Efficiency Unit in Energy Performance ContractsThe system was installed in late 2007More infos Energy Conservation Systems (ECS) - www.ecsaustralia.com


The hospital is fully air conditioned and served by 2 water cooled centrifugal chillers and one water cooled screw chiller with total installed capacity of 4.5 MWr.The HVAC system of the site represents approximately 50% of the electrical peak energy necessary to conditionthe building spaces

COOLING STRATEGYThe chilled water produced through the absorption chiller is connected to the existing chilled water circuitin a "side stream" arrangement. This configuration provides the maximum flexibility as the absorption chiller is able to operate in both parallel and series modes with the existing chillers.The absorption chiller is controlled by the BMS, which receives thermal data and status signals by the PLC.The absorption chiller is to operate continuously as a lead chiller

2 BUILDING 7 IPSWICH

The absorption chiller is to operate continuously as a lead chiller providing there is a sufficient amount of solar thermal heat to operate the chiller efficiently


Processes 1



Continous / Batch

Operating hours per day n.a

Exit temperature of the network(°C) n.a

Temperature of process (°C) n.a

Useful heat demand ( MWh / year) n.a


Operating days per year: n.a d/ year

ANNUAL USEFUL HEAT DEMAND : MWh/yearn.a



The collector field includes 43 tracking parabolic collectors and has a total output of 225 kilowatt thermalThe manufacturer is BROAD. Working condition is 15°C delta T with max output 180°CThe collector field is installed on the roof of a multi-storey car park and has a total collector aperture of 570 m2occupying an area of 920 m2The field has a fixed Nourth-South axis and tracking East-West. The tracking system is controlled by a Omron PLCwhich monitors the radiation levels and tracks to the sun as it travels across the sky.The primary loop is which include the solar collector array contains thermal oil and the secondary loop goingto the absoprtion chiller contains water. The energy transfer between the 2 loops is conducted via heat exchanger.

SOLAR HEAT STORAGEThere is a 6 m3 thermal storage tank for the hot water.The storage tank has a dual purpose and is also used as an expansion tank and is charged with Nitrogen

AUXILIARY HEATING SYSTEMThe chiller is provided with back up gas burner

COOLING EQUIPMENTThe solar cooling is realised through a 300 kWr double effect absorption chiller (H2O/LiBr)The model is BZH25 manufacturer is BROAD (China)

HEAT REJECTIONThe heat rejection is done with a wet cooling tower.

BACK-UP CHILLERThe chiller water produced through the absorption chiller is connected to the existing chilled water circuit in a "sidestream" arrangement.The HVAC system is served by 2 water cooled centrifugal chillers and one water cooled screw chiller with total installed capacity of 4.5 MWr.

COLD STORAGEn.a.


Intercepted energy for the collector field 600,000 kWh/year

2 SYSTEM 7 IPSWICH

Useful energy from collector: 410,000 kWh/yearDriving heat input in TDC: n.a kWhProduced cold: n.a kWhRejected heat: n.a kWhThermal coefficient of performance (COP_thermal): n.aSolar coverage of cooling demand: n.a %

Useful energy from collector for other thermal uses: n.a kWhSolar coverage of other thermal uses: (industrial washing and space heating) n.a %




COMMENTS

COSTSTotal investment costs: €Specific costs: #¡VALOR! €/m2

#¡VALOR! €/kWDistribution of PLANT costs




n.a. €/m2

n.a. €/kWMaintenance: n.a €/year

n.a €/m2

n.a €/kW

Year of reference


FINANCINGEU subsidies n a

no data already available from the monitoring of the plant

n.a.

EU subsidies n.aNational subsidies n.aRegional subsidiesOther subsidies n.aUser cash User loan n.a

n.a.

n.a.



7 IPSWICH5 System Scheme

COMMENTSPrimary loop works with 210°C oil as heat transfer fluid. Oil volume in primary loop is about 500L. Heat exchanger between primary and secondary loop has a capacity of 225 kW. Secondary loop works with 175°C water as heat trasfer fluid. Hot water delta T across the absorption chiller is 15°C. The secondary loop flow rate is 3.6 L/s



GENERAL ASSESSMENT


9 Qualitative assessment 7 IPSWICH




View of collectors field on hospital car park roof

10 Figures, Fotos 7 IPSWICH

Storage/expansion tank

View of absorption chiller

Pictures with courtesy of Energy Conservation Systems (ECS) - Australia


5 REFERENCES

1. Hans-Martin Henning (Ed.): Solar-Assisted Air-Conditioning in Buildings. A Handbook for Planners. SpringerWienNewYork. 2003

2. Arsenal Research. Using the sun to create comfortable indoor conditions. IEA-SHC Task 25. 3. Climasol. Solar air conditioning guide. EC DG Energy and Transport. 4. POSHIP: The Potential of Solar Heat in Industrial Processes. EC DG Energy and Transport.

Coordinator: Aiguasol Enginyeria. (Contract NNE5-1999-0308) 5. Technical description of the adsorption chiller. Albring Industrial Agency GmbH, Germany.

Mycom Adsorption Chiller Technology 6. SACE. Solar Air Conditioning in Europe. EC Research Directorate General.

http://www.ocp.tudelft.nl/ev/res/sace.htm 7. Cooling Technology Institute. http://www.cti.org/whatis/coolingtowerdetail.shtml 8. AP Solar Collectors. http://www.apricus-solar.com 9. Gershon Grossman: Solar powered systems for cooling, dehumidification and air-conditioning.

Solar Energy Vol. 72 nº1. 2002. 10. ROCOCO. Reduction of costs of solar cooling systems (contract No

TREN/05/FP6EN/S07.54855/020094) 11. SOLAIR.Increasing the market implementation of Solar-Air conditioning systems for small and

medium applications in residential and commercial buildings (contract no EIE/06/034/SI2.446612)

12. Private communications form ABSORSISTEM S:L: (Distributor of YAZAKI in Spain) 13. TRNSYS. Transient System Symulation Program. SEL, Solar Energy Laboratory, University of

Wisconsin, Madison (USA). Version 16.0. 14. SHADA .Sustainable Habitat Design Adviser. http://www.sustainable-buildings.org 15. Werner Weiss and Mattias Rommel: Process heat collectors. State of the art within TASK 33/IV

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