transpired solar air heaters

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Transpired Solar Air Heaters

Large TSAH on an industrial building in the USA (Source: Conserval Systems Inc, Canada)>r 1

This technical information sheet is intended to be a

useful and practical guide on the Transpired Solar Air

Heater (TSAH) technology to assist architects and

engineers to specify the technology in building designs.

IntroductionTSAH use clean, ree solar energy to supply tempered ventilation

air to reduce the total heating load or all, or a portion o abuilding. This technology consists o a dark perorated building

cladding that absorbs solar energy. Outside air is drawn through

small holes in the cladding by a an. The air is heated as it travels

up through the cavity, behind the cladding and into the building

supplying outside air and space heating >r 1 .

The technology, which uses similar principles to conventional

solar air heaters and Trombe walls, has evolved over 30 years

through signicant research rom the USA. The technology is

used extensively in Canada, the USA and Europe where there are

hundreds o examples it has been proven to be cost

eective >Rr 5 .

By using this document and other reerences listed, an engineer

will be able to establish key variables including approximateheating capacity, wall areas and an power. In addition, an

architect will be able to determine appropriate applications or, with

the use o reerences, detail a wall that includes a TSAH.

SuitabilityMost effective for buildings with:

> large heating loads

> high outside air requirements

> large indoor spaces

> high ceilings

> large north acing walls

Most suited to:

> Supermarkets

> Sports halls

> Assembly halls

> Factories and other industrial buildings

> Tempering air or other building types such as oces,

schools and apartments.

Not suited to:

TSAH are not recommended when a building has an existing

heat recovery system, a minimal space heating requirement or

where there is no outside air requirement.

NAME : Yousef Adel Mohamed elwakeel

R.N : 12101411

CLASS : 25


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bfs> Reduces cost o heating outside air

> Reduces building wall heat losses

> Destraties indoor air when supplied athigh level

> Improves indoor air quality by supplyingconstant tempered outside air

> Reduces cold air inltration by creating apositive air pressure, hence improving comort

> Can be an architectural eature by recladdingor covering old, existing walls

> Protects northern wall rom unwantedsummer heat gain

> Can preheat outside air by 15C or more

> Reduce greenhouse gas pollution by reducingheating and cooling energy required

cssI installed as a retrot the additional costs are orcladding, xings, fashing, grilles, ans, dampersand connecting ductwork. In new buildings, thecost o heating coils may be included to allow

cost comparisons with other systems (such asradiant heating). The cost o the collector claddingincluding xings and fashing, at the time owriting, is less than $100/m2 subject to quantitiesand access. Net capital cost can be very low innew buildings when the cladding is integratedwith the building aade. The cost o ans, grilles,dampers and ductwork will depend on the sizeand application.

Preheating ventilation air with solar energyremoves load rom a conventional spaceheating system, saving energy and money. Casestudies have shown payback periods can beapproximately 5 years >Rr 5 .

Cost

sand

Benefts

Desig

ndescription The installation o a TSAH is relatively simple.

The collector can be attached to a buildingsexisting structure. The cladding is supportedby the building rame using vertical channelsattached to the existing wall. Horizontalchannels are then attached to the verticalchannels, and the perorated cladding is xed tothe horizontal channels.

Solar collector cladding material(Source: NREL Image Exchange)

>r 3

A hole is cut through the wall or air fow into the

building with duct work connections requiredto orm a seal between a an and the wall. Thean is typically an axial an, along with dampersand controls mounted directly to the interiorside o the wall. This is then connected to the airsupply ducts. >r 4 shows some details, see>Rr 4 or urther examples.

Large unobstructed north acing wall areas

are ideal. The system will still work inother orientations however, with reducedeectiveness. Penetrations, such as windows,also aect eciency.

TSAH are an excellent new construction,reurbishment or retrot solution, particularlywhere a north wall is un-insulated or requires newcladding. The cladding can be tted around wallsand doors. The system can also be connected toexisting conventional ans and ductwork

As the system is sensitive to fuctuations in solarenergy (i.e. cloud cover), the system is typicallycombined with a conventional space heating

system, either air based or radiant to maintaincomort. As an alternative, the system could becombined with thermal storage, such as a rockstore, to extend its heating capacity.

There are many variables that determine

the optimum design and performance of

the system. Collector plate properties are

important including:

> plate surace absorptance (colour)

> size o the perorations

> porosity o the plate

> prole or shape o the plate

System design issues are alsoimportant including:

> air fow rate

> size o the air gap

> location o air intake ans

> detailing or weather proong

> available wall area

>Rr 2 >Rr 3 and >Rr 5 provide guidance on these variables.

A black collector is best, but a wide choice o darkto medium colours may be used with eciencylosses less than 10%.

c !Ds h r s-v sr,

s rss h dd sr h h s s d

dsd v h hh.

SolarWall detail (Source: ConservalEngineering Inc o Canada)

>r 4


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Technic

aldescription

>figure6

TypicalinstallationofaTSAH

>Reerene5

>igur 5 shows a schematic o a typical installation

o a TSAH. The north-acing wall o a building is

covered with a solar collector, consisting o dark-

coloured aluminium or steel cladding perorated

with 12 mm diameter holes. The collector is

externally mounted on the building wall with an air

gap (approximately 150 mm >Rrn 5 and is

sealed around the sides. At the top o the collector

there is a plenum which connects to a an, and air

distribution ducts are installed inside the building.

These ducts can distribute the air directly as or an

industrial building, reer to >igur 6 , or in other

building types the system can be connected to

the buildings heating and ventilation system. By

placing a recirculation damper between the solar

collector and the supply an the raction o indoor

air that is mixed with the incoming solar-heated air

can be controlled so that constant temperature air is

distributed to the building.

In summer, there is a bypass damper which allows

outside air to pass directly into the ventilation

system i required, not through the TSAH. The

cladding does not signicantly overheat in summer

because the stack eect causes outside air to enter

the cladding along the bottom and rise to the top

where it exits through holes in the outer skin. The

net result is that any unwanted solar gain will be

transerred to the air and not to the interior o the

wall. In addition the sun is also higher in the sky in

summer, thereore shining primarily on the roo, not

on the wall. The bypass damper can also be used

or night purging o heat.

>igur 5 The suns radiation warms the solar collectorsurace. Air is heated as it is drawn into the cavity by orced

convection (Source: Conserval Engineering Inc o Canada)

thnil prormnTypically the TSAH does not replace a buildings

heating system. Rather, it works to reduce the

energy required by the heating system to maintain

the building temperature by tempering the supply

air. It also helps reduce cold drats that cause

discomort by reducing the negative pressure in a

building caused by inltration through the aade.

The solar collector is expected to have a lietime

o over 20 years >Rrn 5 . The only moving

parts o the system, the ans and dampers, are

the same as in a conventional system and can last

15 years with regular maintenance.

SizingEstablishing appropriate collector sizing or

available capacity is critical. The Federal

Technology Alert >Rrn 5 on TSAH provides

a good method or sizing. It also provides a good

method or estimating potential energy savings.

There is also a calculator produced by

Natural Resources Canada called RetScreen,

which can help calculate sizing and savings

(www.rsrn.n).

Solar data or estimating energy savings can beobtained rom the Australian Climatic Database

or the ANZSES Solar Radiation database.

The best way to design a TSAH is with a dynamic

thermal simulation sotware package such as

TRNSYS, TAS or IES Virtual Environment. The

majority o these sotware packages can model

the TSAH technology specically or with the solar

air heater being treated as a separate zone on the

outside o the building.

Generally, given incident solar radiation on the

north wall or clear winter day o 400700 W/m2

and 3565% collector eciency >Rrn 3 the

ollowing perormances can be achieved:> Air temperature rise 15C >Rrn 5

> Heat output: 140455 W/m2

This will vary depending on the design o the system.

>igur 8 Typical installation o a TSAH on brick andmetal walls (Source: Conserval Engineering Inc o Canada)


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exmpl o hmhodology or sizing tSaH

The ollowing example is based on the method

provided in >Rrn 5 and >igur 7 .

A gymnasium requires an outside air fow rate o

5,000 l/s and has 200 m2 o available north acing

wall. Given the typical range o airfow through a

TSAH o 20 to 40 l/s/m2 >Rrn 5 , then the

collector area required is between 125 and 250 m2.

Th i i th TSAH

45

40

35

30

25

20

15

10

05

00

0 100 200 300 400 500 600 700 800 900 1000

>igur 7 Air-temperature rise vs. Solar radiation orvarious fow rates: A= 5 l/s/m_, B= 20 l/s/m_, C= 35.5l/s/m_ (Source: Conserval Engineering Inc o Canada)

Solr Rdiion W/m2 o SolrWll

airtem

perureRiseDegc

A

B

C


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Transpired collectors provide the

most reliable, best perorming,

and lowest cost solar heating or

commercial and industrial buildingsavailable on the market today.Quote: u.S. DepaRtment of eneRgy

Case Study

Many hundreds o TSAH have been installed internationally.For example, a Battery Plant in Canada has an installationcovering 420 m2 o wall area. This caters or 19,000 l/s ooutside air supply. The system has demonstrated heatingenergy savings o approximately 1,000 GJ/year or around$10,000/year. The retroft installation cost o less than $70,000($160/m2) in total, including duct modifcations and had apayback period o less than 7 years >Rr 5 . Note thatthese fgures have been directly converted rom Canadiandollars to Australian Dollars in 2006 and were consideredrepresentative at the time o writing. All costs will be site andapplication dependent.


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Ss Vr

Level 28, Urban Workshop

50 Lonsdale Street Melbourne 3000

T > 03 8626 8700

E > [email protected]

W > www.sustainability.vic.gov.au

There are currently no Australian suppliers/manuacturers

o TSAH. However, transpired solar air heaters can be

constructed o standard profle cladding with perorations

and standard ventilation system components. Having said

this, a great deal o R&D has gone into the optimisation opatented systems.

Solarwall by Conserval Engineering the inventors o

the TSAH are happy to provide inormation and

purchasing options.

Contact inormation:

T> 416 661 7057

E> [email protected]

www.srw.

>Rr 1 Solar Preheated Ventilation Air Systems,Advanced Building Technologies Website Produced byNatural Resources Canada & Public Works and GovernmentServices Canada www.advancedbuildings.org/_rames/r_t_

vent_solar.htm>Rr 2 RETScreen (Freeware), Solar Air Heating

Project Analysis Module, Natural Resources Canada,www.retscreen.net

>Rr 3 Use O Perorated Metal Sheets AsSolar Collectors For Building Space Heating by AvindaWeerakoon, Peter Richards, Joe Deans rom the Departmento Mechanical Engineering, University o Auckland and IanMcClew rom Dimond, New Zealand (EcoLibrium - AIRAHMagazine, August 2004)

>Rr 4 Solar Air Systems A Design Handbook.Editors Robert Hastings & Ove Morck. James and JamesDecember 2000 (280 pages) (reer Section IV.3)

>Rr 5 Federal Technology Alert: TranspiredCollectors (Solar Pre-heaters or Outdoor Ventilation Air)rom the U.S. Department o Energy (24 pages)www.eere.energy.gov/emp/pds/FTA_trans_coll.pd

>Rr 6 Solar Air Heating presentation by USNational Renewable Energy Laboratory (NREL) or FederalEnergy management Program (FEMP) (23 slides)www.nrel.gov/emp/ppt/solar_air_heating.ppt

>Rr 7 A CFD Heat Transer Analysis o The TranspiredSolar Collector Under No-Wind Conditions by S. J.

Arulanandam rom the Department o Mechanical Engineering,University o Alberta, Edmonton, AB., Canada & K. G.Terry Hollands and E. Brundrett Department o MechanicalEngineering, University o Waterloo, Waterloo, ON, Canada

>Rr 8 National Renewable Energy Lab Uses CFD toDevelop Low-Cost, Solar Collector by Keith Gawlik, StaResearch Engineer, National Renewable Energy LaboratoryGolden, Colorado, published in Journal Articles by FluentSotware Users (JA087) (3 pages)

>Rr 9 Design o Experiments Heats Up Solar EnergyResearch. by Richard Burnham based on Interview with KeithGawlik, Ph.D. Senior Engineer National Renewable EnergyLaboratory (NREL) (6 pages)

>Rr 10 Emerging technologies and practice 04 ACEEEH17 Solar Preheated ventilation systems (SolarWall TM)www.aceee.org/pubs/a042_h17.pd (2 pages)

>Rr 11Excellent website with calculation tools,images, specifcations and product details

www.cagroup.ltd.uk/products_solarwall.html

>Rr 12 Horsham Library, Transpired Solar Air Heater

>Rr 13 St Leonards College, SustainableTechnologies Centre, Solar Wall

References and ToolsManufacturers / Suppliers

It simply works The

simplest, most efcient

and least expensive way

to preheat outside air or

industrial and commercial

applications is through

the use o a perorated

plate absorbernatuRal ReSouRceS canaDa - feDeRal

goVeRnment DepaRtment SpecialiSing in

SuStainable DeVelopment

transpired solar air heaters

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