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University of Southern QueenslandFACULTY OF ENGINEERING AND SURVEYING

Solar Powered Domestic Air Conditioning System

A Major Design Project Submitted by

Byron Manthey, Sam Pike, Rafiqul Mohammed, Rhyan Wall. Nevin Thomas

In fulfilment of the requirements of

Bachelor of Engineering MEC3303 – System Design

Submitted: 27th October 2014

Semester 2 2014

Table of Contents

Samuel Pike 27/Oct/2014

Executive Summary...............................................................................................................................2

List of Figures.........................................................................................................................................4

List of Tables..........................................................................................................................................4

Nomenclature (Put into Alp order)........................................................................................................4

1.0 Introduction/ Background...............................................................................................................5

1.1 Outline of the Project..................................................................................................................6

1.2 Defining the Project.....................................................................................................................6

1.3 Project Planning...........................................................................................................................6

Gantt chart.....................................................................................................................................7

2. Literature Review..............................................................................................................................7

2.1 Background on Solar Panel and Air conditioner Solar Panel........................................................8

2.2 Air Conditioner..........................................................................................................................12

2.3 Thermal Comfort Levels for Human Occupancy (Byron)............................................................18

2.3.1 Method for Determining Acceptable Thermal Conditions in Occupied Space....................19

2.3.2 Toowoomba climate...........................................................................................................21

2.4 Heat Engine Stirling Engines................................................................................................22

2.4.1 Stirling Cycle Refrigerator/Heat Pump................................................................................24

2.5 Fans...........................................................................................................................................26

2.5.1 Axial fans.............................................................................................................................27

2.5.2 Centrifugal fans...................................................................................................................29

2.6 Ventilation and Ducting.............................................................................................................32

2.6.1Types of Ducting..................................................................................................................33

2.6.2 Ventilation System..............................................................................................................34

2.7 Solar collectors..........................................................................................................................36

Background..................................................................................................................................37

Available solar thermal collector.................................................................................................38

Conclusion...................................................................................................................................42

2.7.1 Photovoltaic Panels................................................................................................................43

3.0 Proposed Design............................................................................................................................44

3.1 Conceptual Designs....................................................................................................................44

References...........................................................................................................................................49

Appendix A: Communications Log.......................................................................................................52

Appendix B: Project Planning..............................................................................................................58


Nomenclature (Put into Alp order)

FEA Finite Element Analysis

Stirling Engine A heat engine which uses cyclic action of compression and expansion of a working fluid being it air or gas to convert heat energy into mechanical work

AC Air Conditioning


1.0 Introduction/ Background

Australia’s climate has a variety of weather from dry arid conditions in the west of the country to hot humid tropical conditions in the northern parts of the country during the spring and summer months of September to February. In order to feel comfortable during the warmer months most people turn on the air conditioners in their homes dropping the ambient temperatures inside the home to a more comfortable level of around 24-25 degrees (Daikin 2014).

With rising electricity costs there has been a push in recent years to find cheaper and cleaner ways to produce energy, which not only reduces greenhouse gases but reduces money spent on electricity bills.

Current air-conditioning systems require large amounts of electricity from the power grid to run either ducted, split systems or multi split systems in the domestic home. In the summer periods this in turn draws huge amounts of power from the already strained energy grid (Strengers 2010).

This Report looks into the use of solar powered air conditioners as an alternative to current air-conditioning technologies in order to reduce the running cost and energy usage.

1.1 Outline of the Project

The aim of this project is to design a domestic solar powered air conditioning system utilizing thermodynamic principles.

This project will be a collaborative group effort from the following 5 students studying MEC3303 System Design: Samuel Pike, Byron Manthey, Nevin Thomas, Rafiq Mohammed, Rhyan Wall

1.2 Defining the Project

Below is the design brief given for this project?

Solar Powered Domestic Air Conditioning System

Australian homes use large amount of electricity in powering domestic air conditioning systems. Your team task is to replace such a system with one that is powered by the sun.

The work effort will involve the investigation of any existing systems and the conceptual design of a new system, an appropriate assessment of market and costing issues and especially detailed mechanical design.

Based on initial investigations into the topic area, various assumptions are going to have to be made in order to quantify and qualify the project. From discussions with various team members and results of literature found the following design decisions were made.

1. A Domestic 3 bedroom house2. Southern Hemisphere, Toowoomba, Australia 3. Ducted Air-conditioning4. Half an Acre of Land around the house


2.4 Heat Engine Stirling Engines

Air conditioning --> common methods like the vapour cycle--> alternative methods that utilise heat engines/pumps (list benefits)

Heat engines are cyclic devices or machines that convert heat energy to work. They all do this in a characteristically similar way by receiving heat from a high temperature source and converting a portion of this energy into work (e.g. a rotating shaft). The remainder of this heat is then expelled as waste energy to a low temperature sink (Cengel & Boles 2006). When heat engines are used as refrigerators or heat pumps, the processes are reversed; heat is transferred from a low temperature source to a high temperature source. Whilst all heat engines operate in a similar manner, specific cycles are more commonly used in different applications.

Totally reversible cycles are used in theory to define the upper limits of real cycles' performances. Two cycles that are totally reversible and involve similar processes to the Carnot cycle (probably one of the most well-known reversible cycles) are the Stirling and Ericsson cycles (Cengel & Boles 2006). Engine designs based on these cycles are external combustion engines (meaning that the source of heat is external) and a regeneration process during which heat is transferred to a thermal energy storage device; significantly increasing efficiency.

These cycles are difficult to achieve in practice and were long only of theoretical interest. They are limited by a number of factors, including (Chen 1998):

all heat transfer processes take place through a finite temperature differences; totally reversible cycles are impossible to achieve; and regenerators are not 100% efficient.

However recent developments in research and technology renewed interest in engines operating on these cycles. The main difference between the Stirling and Ericsson cycles is that regeneration, machines operating on the Stirling cycle are the most efficient practical heat engines ever built (Haywood 2011).

When the Stirling cycle is reversed, the machines operating on the cycle act as refrigerators or heat pumps. The ideal Stirling refrigeration cycle is identical to the Stirling cycle, except the heat absorbing end of the device becomes the cold end and the heat rejecting end of the device becomes the hot region. Compared to conventional methods, Stirling refrigerators or heat pumps can improve the overall energy utilisation efficiency and are environmentally friendly. They also offer the use of safe refrigerants such as air and helium, avoiding the use of more commonly used refrigerants that are harmful to the environment; a 'natural' choice for cooling applications (Elgendy & Schmidt 2010).


There have been multiple studies conducted on the Stirling cycle which support its use in refrigeration based cycles, claiming high efficiency, low power requirements, and better performance overall. Whilst they have been found to work effectively as cryogenic freezers, studies conducted by Tyagi et al. (Tyagi, Chen & Kaushik 2004; Tyagi, Kaushik & Singhal 2002) found that the performance of the Stirling refrigeration cycle is better when the sink inlet temperature (i.e. the temperature outside) is lower and the source side inlet temperature (i.e. the temperature of the room to be cooled) is higher; supporting its use in air conditioning applications.

Schematic of irreversible Stirling/Ericsson refrigeration cycle (Tyagi, Kaushik & Singhal 2002)

2.4.1 Stirling Cycle Refrigerator/Heat PumpLike all Stirling cycle machines, the Stirling cycle refrigerator consists of the following major components (Haywood 2011):

Working gas:Stirling cycle is a closed cycle so during the multiple thermodynamic processes, the working gas operates in a closed system environment; allows for safe refrigerant use.

Heat exchangers:Two are used to transfer heat across the system boundary; a heat absorbing and a heat rejecting heat exchanger.

Displacer mechanism:The displacer works to alternate the working gas between the hot and cold ends of the device via the regenerator.

Regenerator:A thermal barrier between the hot and cold ends of the machine, as well as a thermal store for the cycle. Heat is deposited to the regenerator, as it is circulated via the displacer mechanism, and the temperature of the working gas is lowered; and vice versus as the reverse occurs.


Expansion/compression mechanism:This is the mechanism that requires the net work input to expand and/or compress the working gas. Without this, it is impossible according to the second law of thermodynamics to move heat from a low to high temperature source.

Block diagrams of ideal Stirling-cycle refrigerator/heat pump (Haywood 2011)

During the Stirling refrigeration cycle, there are four main processes (refer to Figure____):

1. Isothermal (constant temperature) expansion: Low-pressure working gas isothermally expands at the cold part of the machine, absorbs heat from the cold space (via the heat absorbing heat-exchanger), thus doing work on the power-piston.

2. Isochoric (constant volume) displacement:The displacer-piston transfers all of the working gas isochorically through the regenerator to the hot end of the machine. Heat is delivered to the gas as it passes through the regenerator, thus increasing the temperature of the gas to that of the hot space. As the temperature increases, the gas pressure increases significantly.

3. Isothermal compression:The power-piston does work on the gas and compresses it isothermally at hot end temperature, hence rejecting heat to the hot space (via the heat rejecting heat-exchanger).


Because the gas is at high pressure, more work is required for compression than was obtained from the gas during expansion. The cycle therefore has a network input.

4. Isochoric displacement:The displacer-piston transfers all of the working gas isochorically to the cold end of the machine via the regenerator. Heat is absorbed from the gas as is passes through the regenerator, thus decreasing the temperature of the gas to that of the cold space. As the temperature decreases, the gas pressure decreases significantly; where the system returns to its initial conditions.

Thermodynamic Processes in the ideal Stirling-cycle refrigerator/heat pump (Haywood 2011)


2.5 Fans

Currently there are two main types of fans used to pump air through air conditioning systems; Axial and Centrifugal fans. Axial fans are broken up three main variations: tube axial fans and vane axial fans (Toolbox 2014a), where the air flow is parallel to the spinning shaft. Centrifugal fans come in backward inclined and forward inclined fan configurations, where the airflow is radial to the spinning shaft.

2.5.1 Axial fans

Tube axial fan: are designed for an application’s where clean dry air is guaranteed and self-cleaning is not required. The fan needs to be aligned with the airflow, would be used in applications where space is not an issue. The main disadvantage about this type of fan is that it can’t handle small air flow applications as the minimum CFM is 2,500 which is a volume flow rate of 1180 L/s. The fan can withstand air stream temperatures up to 40°C in normal operation, but for special applications can handle up to 200°C (fan 2014).The advantages of this fan design is that the blade pitch can be manually adjusted to allow for future higher or lower flow conditions.

Below is a typical layout of a tube axial fan:

Figure 1: Diagram of Tube axial fan (Engineering 2014, p. 3) Figure 2: Domestic Tube Axial Fan (Aerovent 2014)

Tube axial fans are often called duct fans due to their placement in ventilation ducts, and due to their size they are used in large domestic or industrial applications. They can withstand grit and sand ingestion as well as work in a corrosive environment. This type of fan is often used close to the sea and marine environments on ships. Where very high airflows are needed these fans can be mounted in series such as high rise buildings.


Figure 3: Performance Curve of a Tube Axial Fan (Engineering 2014)

Vane Axial Fan: are designed for applications where a constant flow rate needs to be maintained, this is done by the use variable guide vanes which are either motor or electrically driven.

Figure 3: Motor Driven Vane Axial Fan (Air 2014) Figure 4: Electric Driven Vane Axial Fan (Air 2014)

Figure 5: Diagram of Vane Axial Fan (Engineering 2014)

The variable guide vanes straighten the air and recover the energy of rotation by the adjustment of the guide vanes to the point of smoothing out the performance curve. Other advantageous of the variables guide vanes is the ability to change the pitch of the blades in motion to allow a higher or lower volume of air through the fan.


Due to the mechanical pitch changing mechanism this fan is not conducive to corrosive environments and works with the best efficiency curve when it’s operating in clean dry air. This particular fan works well in duct environments with inline flow designs and where ample space is available to install the fan assembly.

Below is the vane axial fan’s performance curve, when placed in comparison with the tube axial fan the vane axial fans performance curves is visibly smoother.

Figure 6: Performance curve of Vane Axial Fan (Engineering 2014)

2.5.2 Centrifugal fans

Centrifugal fans or blowers are used when space is a big issue, as seen from the photo below. The intake of the centrifugal fan is on the side of the fan and the outlet is close to the inlet. This particular example is a single intake model mainly used in smaller air conditioning applications (Industries 2014).

Figure 7: Single intake Centrifugal fan (Wikapedia 2014)

There are many types of types of centrifugal fans available on the market; the two most commonly used on domestic air conditioners are the backward curved blades and the forward curved blade fan versions.


Intake

Outlet

Backward curved blade centrifugal fan: Like all centrifugal blowers the fan blades are designed to provide the best efficiency for a given rpm. Unlike axial fans very high efficiencies close to 80% can be achieved by using a centrifugal fan. Other important considerations when using these types of fans are their quiet operation, the small space that they can occupy and their high volume high pressure ratio. But unlike the tube axial fan, the backward curves centrifugal fan can run on direct drive or belt drive but needs dry clean air to operate at its best efficiency.

In the case of the backward curved blade configuration, they are mainly used as suction or inducing fan, which draws air across the air conditioner condenser. The disadvantage of this kind of fan design is a higher speed of the fan is required to produce the same volume of air. As a result they are mainly used in large diameter fan configurations.

Figure 8: Backwards curved blade (Bob 2014)

This type of centrifugal fan performance curve shows that with an increase the delivery volume, the horsepower increases until the highest efficiency of fan performance is reached then drops of again. Other issues of this design are that certain blade configurations can increase the rate of dust and solids build-up; as a result dust protection is often needed in the form of extra air channels and thus the efficiency of blades drops of dramatically.

Figure 9: Backward curved blades in various configurations (Airtek 2014)


Forward curved blades centrifugal fan: The forward curved blade centrifugal fan is the most common type of domestic air conditioning fan on the market because of its high volume low pressure fan design in which the fan blades are facing towards the outflow. So the fan is scooping a constant volume of air every revolution. The advantages of this design are; A lower rpm than required for the backwards facing curved blade to deliver the same volume of air and quieter operation as a result. The disadvantages of this design a greater number of blades required hence a higher weight than the backwards facing curved blade. The performance chart below shows that a lower rpm is needed to deliver the same delivery volume, thus the high volume, low pressure advantage of this style of fan.

Figure 10: Forward curved blades centrifugal fan performance chart (Bob 2014, p. 4)

Figure 11: Dual intake forward centrifugal fan (ehmpapst 2014, p. 5)

The above figure is an example of a forward centrifugal fan used in many domestic air conditioning applications. The dual intake allows a balanced amount of air to enter the fan thus allowing a constant volume of air to exit across the fan outlet.


Formula’s

In order to calculate the right centrifugal fan speed, flow rate and power consumptionThe following Laws need to be considered used.

Figure 12: Affinity Laws (Toolbox 2014b)


2.6 Ventilation and Ducting

In order for an AC system to deliver metered conditioned air into living areas of a home a series of ducts are required to send air from the AC to the rooms. The diameter of the ducting changes with the distance to be travelled throughout the house.

Figure 1: Ducted AC system (SAE 2014)

2.6.1Types of Ducting

In modern buildings there is two types of ducting configurations metal ducts and flexible ducts. Metal ducting is mainly used in office and industrial applications. Whereas flexible ducting in better suited to domestic applications as they are often smaller and fit into tighter spaces than metal ducts.

Metal Ducts: Large inflexible square ducts that often need to be custom made for a particular area and are often expensive. The advantages of this type of duct are the strength and rigidity of the installation. These types of ducts are mainly used in large office buildings and industrial areas where flexible duct work could be easily damaged. Metal ducts are often not insulated which means that they lose cooling into crawl spaces and attics over long duct runs (ebay 2014).

Figure 2: Metal duct (Isover 2013)

Other advantages of un-insulated ducting are; in temperate climates such as Toowoomba, the ducts themselves provide air exchange rates which provide free cooling properties by the nature of their metal design thus providing fresh air into the office space without turning on the AC system. Modern ductwork has insulation installed in the dusts preventing losses due to the nature of the metal duct work, glass wool and mineral wool are often used to also reduce AC system noise through the ducts.


Flexible ducting: Flexible ducting is the most common type of ducting utilised in domestic operations. It’s cheap, lightweight and can be formed easily into required shape. It comes in two general forms; un-insulated and insulated.

Figure 5: Installed ducting in a ceiling (Inc 2011, p. 2)

Un-insulated flexible ducts are made of Aluminium and is mainly used in domestic roof ceilings with insulation, its comes in standard 10m lengths, in a wide variety of diameters from 76mm - 1200mm and are fire resistant.

Figure 3: Un-insulated flexible ducting (Plus 2014) Insulated flexible ducting is a new type of ducting using 25mm fibreglass polyester insulation material like which eliminates much of the sound as well as utilising a vapour jacket made from Metalized Polyester which dramatically improves the thermal efficiency of the ducts by retaining the mixed air temperature for longer periods of time. Although these ducts are slightly more expensive than un-insulated ducts, the benefits greatly outweigh the additional cost.

Figure 4: Insulated duct (Plus 2014)


2.6.2 Ventilation System

Most domestic ventilation systems have basic components that fix together to form the AC system. Below is a mock-up of a complete AC system used to test components.

Figure 5: Mock-up of ducted AC system (Inc 2011)

Figures 6: Duct System (Pack 2008)


Figure 7: Individual components of Ventilation System (Pack 2008)

2.7 Solar collectors

The world’s reliance on energy sources produced from fossils fuels is at its highest point since its inception. This reliance and every increasing demand is recognised by most developed countries as doing unacceptable amounts of damage to the natural environment. This recognition is influencing a continually growing demand for environmentally friendly energy production alternatives. This chapter of the report will address the alternatives of energy production utilising the sun as the main energy source.

Solar Thermal

Square Dish

Power Kinetics have developed and improved their concept for solar energy collection named the Square Dish. Their design uses a unique sun tracking system, with a series of mirrors mounted on a pivoting axis that allows the collector to track the seasonal change in trajectory of the sun. The Square Dish solar collector works by focusing the sun on a centralised point. The energy created from this focusing, results in the production of steam, this steam can be used to power a generator or an energy source reliant on thermal energy. The maximum temperature of steam produced by the power kinetics design is 400°C, E.K.Inall et al 1994. As can been seen in figure XX a detail breakdown of the components of the design are present, take note of the solars collector’s ability to rotate with the sun and the ability of each mirror array to tilt to optimise the angle with the sun.


Solar collector pipping

One of the main parts of a solar thermal array is the piping needed to transport the steam from the solar collector to the source of energy conversion. The standard closed cell, polymer pipe insulation is only rate to 105°C ( Berrill, T,D, 2010) and is not suitable for the application of solar collectors. The pipework and insulation must be able to withstand temperatures in excess of 300°C, in an all-weather environment subjected to direct ultraviolet exposure.

BackgroundThe Sun is the main resource of solar power, It is a sphere of intensely hot gaseous with a diameter of 1.39×10^9 m and is on average, 1.5×10^11 m from the earth. The sun has an effective blackbody temperature of 5777K (Duffie & Beckman 2013).

Solar power is captured when energy from the sun is converted in to electricity or used to heat air, water, or other fluids. There are currently two main type of technology available; solar thermal and solar photovoltaic.

Solar photovoltaic: Photovoltaic cells (PV) directly converted sunlight in to electricity. PV cells are made from semiconductor materials such as silicon, which act as insulators at low temperatures and as conductors when heat is available.

Solar thermal: Solar thermal systems convert sunlight in to thermal energy (heat). Most thermal system use solar energy for space heating or to heat water. However this heat energy can be used to drive a refrigeration cycle to provide solar based cooling system. The heat can also be used to make steam which can operate steam turbine to produce electricity.

Available solar thermal collector

There are many different type of solar thermal collector are available:


Figure 1 (Watt 2010)

Evacuated tube solar thermal systems is one of the most popular solar thermal systems. An

evacuated solar system is the most efficient and a common means of solar thermal energy

generation with a rate of efficiency of 70 per cent. As an example, if the collector generates 3000

kilowatt hours of energy in a year then 2100 kilowatt hours would be utilised in the system for

heating water(The Renewable Energy Hub). The rate of efficiency

is achieved because of the way in which the evacuated tube

systems are constructed, meaning they have excellent insulation

and are virtually unaffected by air temperatures. The collector

itself is made up of rows of insulated glass tubes that contain

copper pipes at their core. Water is heated in the collector and is

then sent through the pipes to the water tank. This type of

collector is the most efficient, but also the most expensive.

Flat plate solar thermal system are another common type of

solar collector which have been in use since the 1950s. The main

components of a flat plate panel are a dark coloured flat plate absorber with an insulated cover, a

heat transferring liquid containing antifreeze to transfer heat from

the absorber to the water tank, and an insulated backing. The flat

plate feature of the solar panel increases the surface area for heat

absorption. The heat transfer liquid is circulated through copper or

silicon tubes contained within the flat surface plate. This type of

panels easy to install and its used for mostly domistic hot water

needs.

Thermodynamic panels are a new development in solar thermal technology. They are closely

related to air source heat pumps in their design but are deployed on the roof or walls like regular

solar thermal panels and do not have to be south facing. The concept behind

thermodynamic solar technology is that it acts like a reverse freezer and they differ from

conventional solar thermal in that they do not use solar radiation to heat up heat

transferring liquids.

Solar thermal air collector are mostly used for space heating and can be both glazed and

unglazed. They are among the most efficient and economical solar thermal technologies


Figure 2(The Renewable Energy Hub)

Figure 3 (The Renewable Energy Hub)

Figure 4(The Renewable Energy Hub)

available and are mostly used in the

commercial sector. The top sheet of a glazed

system has a transparent top layer and an

insulated surrounding frame and back panel

to prevent heat loss to the surrounding air.

An unglazed system uses an absorber plate

which air passes over while heat is taken

from the absorber.

Solar thermal bowl collector is similar in

fashion to a parabolic dish but has a fixed

mirror instead of a tracking mirror which a

parabolic dish would use. The solar

concentrator (dish) gets the solar energy

coming directly from the sun. The resulting beam of concentrated sunlight is reflected onto a

thermal receiver that collects the solar heat. The dish is mounted on a structure that tracks the sun

continuously throughout the day to reflect the highest percentage of

sunlight possible onto the thermal receiver.

The power conversion unit includes the thermal receiver and the Stirling engine with generator. It

absorbs the concentrated beams of solar energy, converts them to heat, and transfers the heat to

the piston cylinder (engine) to run fly-wheel and generate power through the generator. A Stirling

engine uses the heated fluid to move pistons and create mechanical power. The mechanical work, in

the form of the rotation of the engine's crankshaft, drives a generator and produces electrical

power.

The above picture shows is orientable dish parabolic solar collector its made up of an aluminium

paraboloid with a polymeric inside. The stirling fixed on heat focus spot with the generator. Generaly

this type of stirling engine can produces power between 500W to 2 kW depend on how efficient the

reflector is.


Figure 5 (The Renewable Energy Hub)

Thermal efficiency of the dish solar collector:

Actual usefull heat gain quof the dish collector, considering conduction, convection and radiation

heat losses is given by (Yaqi, Yaling & Weiwei 2011).

Where, I = Solar flux intensity

Aapp= Collector aperture area

η0=¿Collector Optical efficiency

Arec=¿Absorber area

h = Conduction and convection co-

efficient

T H=¿ Absorber Temperature

T H = Ambient temperature

ε = emissivity fector of the

collector

δ = The Stefan’s constants


Figure 6: (Themodynamics parabolic solar concentrators (Stirling engine) 2013)

Figure 7 (Yaqi, Yaling & Weiwei 2011)

Solar collector also had many different

dimensional form, the most efficient

collector is half sphear with coller plate. The concentrates the incident beam irradiation on to a

smaller area called focal point (Reddy & Veershetty 2013) where the receiver devise is located. The

solar irradiation absorbed by the receiver and moved through the cavity to working station. The

parabolic dish continuously tracks the sun in the two axes that azimuth and elevation.

Solar cavity receiver: Heat loss from solar receiver is also common problem, the natural convection

and radiation heat losses from receiver substantially reduced the performance.

Picture of FEA analysis of different angle positioned of absorber;


Figure 8 (Reddy & Sendhil Kumar 2008)

Above picture shows from 2D numerical analysis of receiver carried out for positive inclination angles of 0 to 90 degree, the maximum heat lose occurs at 0 degree and most efficient is at 90 degree positioned receiver.

Conclusion

Those many different types of thermal collector are mostly to use for house hole hot water system

which is water flow through panel to the reserve tank. Solar thermal bowl collector is the suitable for

operating Stirling engine which directly supply heat to the absorber cavity. Further need to find dish

sizes and the amount of heat required to operate engine.

2.7.1 Photovoltaic Panels

Photovoltaics (PV) are a method of producing energy by converting solar radiation into electrical energy. The process works by the photovoltaic panels consisting of a number of solar cells absorbing the solar radiation and with the use of semiconductors converting the solar radiation to electrical current. The advantages of PV over conventional energy sources are detailed below;

Pollution free. Long life span 20 - 40 years +. Can return a cost offset. Reduces transmission losses. Low operation costs.

In a typical solar cell, sunlight detaches electrons from their host silicon atoms. During this process protons are captured by electrons and impart enough energy to disassociate the electron from its host atom. The upper part of the solar cell consists of a membrane called a Pn-junction, when the electron crosses the membrane it is unable to return. The free electron causes a negative voltage on the upper surface of the membrane and a positive voltage on the lower surface. The cells are connected in larges panels and the result is a substantial supply of voltage.


Figure 9 PV setup (http://theconversation.com/)

Figure XX shows the common setup of a PV system. It comprises of a number of PV panels, an isolation switch, generation meter, main fuse box, and an inverter to transfer the voltage from DC to AC. The mean cost associated with a PV system for a standard size house is between $6000-$8500 (Blakers, A, 2013).

3.0 Proposed Design

3.1 Conceptual Designs


Initial Conceptual Flow Diagram System Flow Diagram


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