pRobLemS

            The photovoltaic is a device that that convert solar radiation into electricity. However, during the operation of the PV cell, only around 15% of solar radiation is converted to electricity with the rest converted to heat. The electrical efficiency will decrease when the operating temperature of the PV module increases. So, for getting the highest efficiency, the optimum temperature must be 25^oC.

            In Malaysia, the ambient temperature is  about 34^oC. Due to the increasing temperature, the efficiency will decreased and the output will be low. It is not worth it with the high cost. So, to reach the 25^oC in Malaysia is impossible but by using an active cooling, the temperature can be adjust to the lowest as possible, so the efficiency will be increased.

            There are many types of photovoltaic materials that can be used such as crystalline silicon, amorphous and etc. The commonly types that being used in industry is crystalline silicon. The crystalline silicon (c-Si) has been used as the light-absorbing semiconductor in most solar cells, even though it is a relatively poor absorber of light and requires a considerable thickness (several hundred microns) of material. Nevertheless, it has proved convenient because it yields stable solar cells with good efficiencies (15-17%, half to two-thirds of the theoretical maximum).

            The performance of photovoltaic and thermoelectric is being monitored and measured by using LabView that provide graphical display output chart, graph or pie chart. LabView also will become a problem because inefficient in using it. To overcome, LabView will be studied in more detail.

inTr0dUctioN

            In recent years, renewable energy is widely advocated by many countries. Photovoltaic cell is one of the most popular renewable energy products. It is a technology which generates electricity from sunlight and it works only with certain spectrum of the white light component of the sun. In Malaysia, the abundance of sunlight makes solar photovoltaic a very viable form for generating electricity. Since the sun is the fuel source of photovoltaic electricity, this form of electricity generation is said to be renewable.  Solar photovoltaic (PV) is not only renewable; since there is no CO2 emission in the process of electricity generation, solar photovoltaic is also considered a clean form of electricity generation or can be described as friendly environment.

            However, during the operation of the PV cell, only around 15% of solar radiation is converted to electricity with the rest converted to heat. The electrical efficiency will decrease when the operating temperature of the PV module increases.

That is because the optimum temperature of photovoltaic is 25^oC but in Malaysia, the ambient temperature is 34^oC.So, to overcome this problem, the thermoelectric is being used because it can moved the heat from one side to the other side. From this heat, it can convert into electricity because thermoelectric is a device that creates voltage when there is a different temperature on each side. By this, the efficiency will increased.

            However, it is unrealistic to expect the efficiency of both continuously. There must be some time the efficiency will drop. So, to overcome this, an active cooling have been used. Fan has been found to be the best methods to cooling the thermoelectric that can lower the temperature of thermoelectric and by this, it will raise the temperature differences between photovoltaic and thermoelectric. The highest temperature differences between the photovoltaic and thermoelectric, the higher the efficiency and the performance of PV-TE will be improved.

aBstRact

            Photovoltaic is a method for generating electric power by using solar cells to convert solar radiation energy from the sun into electricity. The concentration of radiation on the performance of the system causing heat problem and reduce the efficiency of the photovoltaic. So, the thermoelectric has been used as a device to remove the waste heat. Then, it convert the thermal waste into electricity. The thermoelectric will be attached to the back of photovoltaic modules to form a PV–TE hybrid module. By using the thermoelectric, the heat moved through the module from one side to the other because thermoelectric is a device that creates voltage when there is a different temperature on each side.

            The development and performance analysis of photovoltaic-thermoelectric (PV-TE) hybrid module with active cooling element by using LabView is a project to measure the performance of PV-TE by increasing the efficiency using the active cooling element to cool the thermoelectric.

            This research study will examine the best design for active cooling element that can increase the efficiency of photovoltaic and thermoelectric. The higher the temperature difference, the higher of the efficiency. This research study will concludes with recommendation that can improved the system in the future.

Journal of Solar Energy Engineering

Journal of Solar Energy Engineering

J. Sol. Energy Eng. / Volume 128 / Issue 2 / TECHNICAL BRIEFS

Analysis of Potential Conversion Efficiency of a Solar Hybrid System With High-Temperature Stage

J. Sol. Energy Eng.  -- May 2006 --  Volume 128,  Issue 2, 258 (3 pages)
http://dx.doi.org/10.1115/1.2189865

Author(s):
Y. V. Vorobiev
CINVESTAV-Querétaro, Libramiento Norponiente 2000, Querétaro 76230, QRO, México

J. González-Hernández
CIMAV, Miguel de Cervantes 120, Chihuahua 31109, México

A. Kribus
Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel

The analysis is given of hybrid system of solar energy conversion having a stage operating at high temperature. The system contains a radiation concentrator, a photovoltaic solar cell, and a thermal generator, which could be thermoelectric one or a heat engine. Two options are discussed, one (a) with concentration of the whole solar radiation on the PV cell working at hightemperature and coupled to the high-temperature stage, and another (b) with a special PV cell construction, which allows the use of the part of solar spectrum not absorbed in the semiconductor material of the cell ("thermal energy") to drive the high-temperature stage while the cell is working at ambient temperature. The possibilities of using different semiconductor materials are analyzed. It is shown that the demands to the cell material aredifferent in the two cases examined: in system (a) with high temperature of cell operation, the materials providing minimum temperature dependence of the conversion efficiency are necessary, for another system (b) the materials with the larger band gap are profitable. The efficiency of thermal generator is assumed to be proportional to that of the Carnot engine. The optical and thermal energy losses are taken into account, including the losses byconvection and radiation in the high-temperature stage. The radiation lossesimpose restrictions upon the working temperature of the thermal generator in the system (b), thus defining the highest possible concentration ratio. The calculations made show that the hybrid system proposed could be both efficient and practical, promising the total conversion efficiency around 25–30  % for system (a), and 30–40  % for system (b).

©2006 American Society of Mechanical Engineers

History:	Received 20 September 2005; revised 30 September 2005
Digital Object Identifier	http://dx.doi.org/10.1115/1.2189865