WO2013025094A2

WO2013025094A2 - Photovoltaic-thermal collector apparatus

Info

Publication number: WO2013025094A2
Application number: PCT/MY2012/000229
Authority: WO
Inventors: Faridah HUSSAIN; Zulkhairi ANUAR; Mohd. Yusof OTHMAN
Original assignee: Sirim Berhad
Priority date: 2011-08-18
Filing date: 2012-08-13
Publication date: 2013-02-21
Also published as: MY173884A; CN104040882A; WO2013025094A3

Abstract

There is disclosed a photovoltaic-thermal collector apparatus (1) comprising of a heat exchanger module (15), a mono-crystalline, silicon solar cell photovoltaic, module (16), a blower (11), a ducting (13) to provide path for air flow and a variable voltage regulator (113) for controlling the speed of the blower (11). The heat exchanger module (15) is formed having a cross-sectional honeycomb structure with an inlet (14) and outlet (17) for air flow.

Description

PHOTOVOLTAIC-THERMAL COLLECTOR APPARATUS 1.0 TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of solar energy harvesting. More particularly, the present invention relates to a compact aluminum hexagonal honeycomb heat exchanger module integrated into a solar photovoltaic thermal collector for efficient and reliable operation of the same.

2.0 BACKGROUND ON INVENTION The technology toward harnessing solar energy has advanced considerably in recent years due to the growing demand for renewable energy sources. A partial list of solar applications includes space ^ heating and cooling through solar architecture, solar hot water, . solar cooking, and high temperature process heat for industrial purposes .

Active solar technology includes the use of photovoltaic (PV) modules to harness the energy. A major drawback of PV modules is in their efficiency which is dependent on temperature_.. PV modules suffer from a drop in efficiency with the rise in temperature due to increased resistance. The commercially available PV modules efficiency claimed by manufactures is only in the range of 6% to 16% at a temperature of 25°C. Due to the relatively low efficiency . provided by the PV modules, the solar industry continue to search for better ways to harvest solar energy and one of the means is by using solar photovoltaic thermal collector, also known as PV/T technology. The PV/T technology incorporates PV modules and solar thermal collector into one integrated system. This advanced system is engineered to carry heat away from the PV modules thereby cooling the modules and thus improving their efficiency by lowering resistance. The PV modules is use to convert solar radiation into electricity while the solar thermal collector is designed to collect remaining energy and removes waste heat from the PV module. A simultaneous cooling system using air or water is provided as a medium for heat transfer. The heat output from the system can be collected and stored as thermal energy.

While PV/T has been able to overcome the problem described in solar harvesting, many researches have continuously been done to seek improvement in the technology. One of the areas studied is the heat exchanger to cool the PV modules as it has significant impact on the system efficiency. For example, Mohd had studied performance of a single pass PV/T system with aluminum v-grooved absorber plate, attached at the back of the PV module, and obtained an increase in electrical and thermal efficiency by 1% and 30% (Mohd. Yusof Hj . Othman, H.R.2009.Performance. Study of Photovoltaic- Thermal (PV/T) Solar Collector with v-Grooved Absorber Plate. Sains Malaysiana: 537-541) . In another studies by Jin, it was found that a PV/T system with rectangular tunnel heat exchanger yield a better thermal efficiency compared to the conventional PV/T system. Jin obtained electrical and thermal efficiency of 10.02% and 54.70% by utilizing a single pass air base solar collector with rectangular tunnel heat exchanger, which is made of aluminum, for harnessing solar energy (Jin, G. L .2010. Evaluation of Single-Pass Photovoltaic-Thermal Air Collector with Rectangular Tunnel Absorber. American Journal of Applied Sciences: 277-282). Despite the feasibility of these PV/T systems, there is still need to improve the efficiency of the PV/T system to the maximum level. Hence, it is desirable to seek for the alternative heat exchanger that is capable of ^"maximizing the electrical and thermal efficiency of the PV/T system.

It is therefore an object of the present invention to provide a PV/T system capable of maximizing thermal efficiency and maintaining electrical efficiency at high temperature; such PV/T system includes a heat exchanger module, a mono-crystalline silicon solar cell photovoltaic module, a blower, a ducting to provide path for air flow and a variable voltage regulator for controlling the speed of said blower. The heat exchanger module is . formed having a cross-sectional honeycomb structure with an inlet and outlet for air flow. Such heat exchanger would provide a large surface area for an efficient heat transfer from the mono-crystalline silicon solar cell photovoltaic module. The use of the aluminum hexagonal honeycomb heat exchanger is found to be able to maintain electrical efficiency of the mono-crystalline silicon, solar cell . photovoltaic module at high temperature. Further, .the design of the aluminum hexagonal honeycomb heat exchanger which is compact and light would provide a highly dependable apparatus to be utilized into Building Integrated Photovoltaic/Thermal application. 3.0 SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a photovoltaic-thermal collector apparatus capable of maximizing thermal efficiency.

It is yet another object of the. present invention to provide a photovoltaic-thermal collector apparatus that is capable of maintaining electrical efficiency at high temperature.

These and other objects of the present invention are accomplished by providing, A photovoltaic-thermal collector apparatus comprising a combination of a heat exchanger module, a mono- crystalline silicon solar cell photovoltaic module, a blower, a ducting to provide path for air flow and a variable voltage regulator for controlling the speed of said blower; characterized in that, said heat exchanger module having a cross-sectional honeycomb structure with an inlet and outlet for . air flow. 4.0 BRIEF DESCRIPTION OF THE DRAWINGS

Other aspect of the . present invention and their advantages will be discerned after studying the Detailed Description in conjunction with the accompanying drawings in which:

Figure 1 shows a perspective view of the photovoltaic- thermal collector apparatus according to one embodiment of the present invention.

Figure 2, shows cross-sectional view of the heat exchanger module according to one embodiment of the present invention.

Figure 3, shows a graphs of output temperature (T_out) against values of mass flow rate according to one embodiment of the present invention.

Figure 4, shows differences between inlet and outlet temperature according to one embodiment of the present invention.

Figure 5, shows electrical efficiency of _. the photovoltaic-thermal collector apparatus with and without the heat exchanger module according to one embodiment of the present invention.

Figure 6,. shows thermal efficiency of the photovoltaic- thermal collector apparatus with and without the heat exchanger module according to one embodiment of the present invention.

5.0 DETAILED DESCRIPTION OF THE DRAWINGS

In the broadest aspect of the invention, a photovoltaic- thermal collector apparatus comprising of a combination of a heat exchanger module, a mono-crystalline silicon solar cell photovoltaic module, a blower, a ducting to provide path for ^; air flow and a variable voltage regulator for controlling the speed of the blower. Referring now to Figure 1 showing the photovoltaic- thermal collector apparatus (1) use for simultaneously producing electrical and thermal energy according to one embodiment of the present invention. The apparatus (1) comprising of a blower (11), a heater (12), and a ducting (13) as the components to provide consistent air flow through the photovoltaic-thermal collector apparatus (1). A variable voltage regulator (113) is use to control the speed of the blower (11) and another variable voltage regulator (114) is use to control temperature of the heater .(12). The apparatus (1) further comprises of a heat exchanger module (15) installed at the back of a mono-crystalline silicon solar cell photovoltaic module (16). The heat exchanger module (15) has a cross- sectional honeycomb structure which enable uniform air flow through its inlet (14) and outlet. (17). A flow meter (not shown) is provided to measure the air speed at the inlet (14) of the heat exchanger module (15). The heater (2) temperature is adjusted for maintaining the temperature at the inlet (14) of the heat exchanger module (15) to be equal with the ambient temperature. A stack of aluminum ( 18 ) -polyethylene ( 19 ) -aluminum (110) sheet is attached below the heat exchanger module (15). ^' The polyethylene (19) sheet is use as a thermal insulator to minimize heat loss from the apparatus. A plurality of type T-thermocouple is provided for measuring temperature. A pair of type T thermocouple (not shown) is use to measure the temperature at the inlet (14) of. the heat exchanger module (15) . Another two units of type T thermocouple are use to measure temperature at the outlet (17) of the heat exchanger module (15) . Four units of type T thermocouple (not shown) are attached to the back of the mono-crystalline silicon solar cell photovoltaic module (16) for measuring temperature of the photovoltaic module (16) and another two units of type T thermocouple are attached at the back of the aluminum^' sheet (19) .

Referring now to Figure 2 showing the cross-sectional view (2) of the heat exchanger module (15). The heat exchanger module (15) is shown to have a hexagonal cross- sectional view (2). The heat exchanger module (15) is fabricated by stacking a plurality of corrugated aluminum sheet .

Referring back to Figure 1. The photovoltaic-thermal collector apparatus (1) has been subjected to an indoor experimental work for investigating its electrical and thermal efficiency. In order to obtain a steady state thermal performance of a solar collector, the apparatus (1) has been tested under a solar simulator. For comparison purposes, the apparatus (1) was evaluated with and without the heat exchanger module (15). Different mass flow rate ranges from 0.011 kg/s to 0.113 kg/s have been introduced to the apparatus (1) in order to observe the effect of mass flow rate towards the efficiency of the system.

The experimental work was conducted under two different solar irradiance values which are 583 W/m² and 808 W/m². Air which act as the heat removing fluid was made to flow through the apparatus (1). For each solar irradiance value setting, five different points of mass flow rate was tested. The mass^' flow rate had been set to be 0.011 kg/s, 0.032 kg/s, 0.049 kg/s, 0.078 kg/s and 0.113 kg/s. A voltage regulator (113) as shown in Figure 1 has been used to control the speed of the blower (11) in order to obtain the required mass flow rate. To observe the consistency .of the experimental result, the same experiment has been repeated for three times. At each setting of solar irradiance and mass flow rate, data for parameter such as short circuit current, I_sc (A) current, I (A); maximum current, I_max (A); open circuit voltage, V_oc (V) ; voltage, (V) ; maximum voltage, V_max (V) ; ambient temperature (°C); temperature (°C) at the inlet (14) of the heat exchanger module (15); temperature (°C) at the outlet (17) of the heat exchanger module (15); temperature (°C) of the mono-crystalline silicon solar cell photovoltaic module (16); and temperature (°C) at the back of the aluminum sheet (110) were measured. Two units of variable rheostat (39 Ω and 10 Ω ) were used during the IV curve measurement. Digital multimeter and 10 units of type T thermocouple were used to measure, the voltage, current and temperature. The measured data were used to calculate the electrical and thermal efficiency of the photovoltaic-thermal collector apparatus (1). Mass flow rate, m of air was calculated using the following equation: m = pAVav

where m is mass flow rate, p is density of air, A is area of the input and V_av is air velocity. Measured values of short circuit current, I_sc ( A ) and open circuit voltage, V_oc (V) , was obtained by connecting the mono-crystalline silicon solar cell photovoltaic module (16) directly to the multimeter. By regulating the variable rheostat, an IV curve shall be performed. From the IV curve, maximum current, I_max ( A ) and maximum voltage, V_max were determined. With this parameter, maximum power (Pmax) was calculated using the following equation:

The electrical efficiency, _eiec of the system, was calculated using the following equation: nelec = Im_X_Vm X 100%

A_CS Area of the mono-crystalline silicon solar cell, photovoltaic module (16) coved by solar cell is^: represented by A_c and S is the solar irradiance. Mass flow rate, m; specific heat of air, Cp; input temperature, Ti_n; output temperature, T_out; area of mono-crystalline silicon solar cell photovoltaic module (16), A_p; and solar irradiance, S; were used to calculate the thermal efficiency of the apparatus (1) by using the following equation: = mC_p(T_out - Tin) x 100%

A_PS

Referring now to Figure 3 showing the graphs of output temperature (T_out) against values of mass flow rate. Data for system performance with and without honeycomb at solar irradiance of 583 W/m₂ and 808 /m2 are shown on the graph. It is proved that large contact area of the heat exchanger module (15, refer to Figure 1) with the back of the mono-crystalline silicon solar cell photovoltaic module (16, refer to Figure 1) has enable it to transfer heat from photovoltaic module (16, refer to Figure 1) efficiently. Furthermore the geometrical honeycomb structure of the heat exchanger module (15, refer to Figure 1) has enables heat from the photovoltaic module (16, refer to Figure 1) to be transferred efficiently through radiation, convection and conduction. Air which as heat removing fluid absorbed the heat and flow to the end of the apparatus (1) . It is shown in Figure 3 that for both setting of solar irradiance, the output temperature of the apparatus (1, refer to Figure 1) with the heat exchanger module (15, refer to Figure 1) is in average 5 °C higher compare to the apparatus without the heat exchanger module (15, refer to Figure 1). Referring now to Figure 4 showing the differences between inlet and outlet temperature. It is shown that the apparatus (1, refe to Figure 1) with heat exchanger module (15, refer to Figure 1) have higher differences in their inlet and outlet temperature thereby producing higher thermal efficiency.

Referring now to Figure 5 showing the electrical efficiency of the photovoltaic-thermal collector apparatus (1, refer to Figure 1) with and without the heat exchanger module (15, refer to Figure 1) . It is shown that the electrical efficiency increased with the increased of the mass flow rate. The electrical efficiency of the mono-crystalline silicon solar cell photovoltaic module (16, refer to Figure 1) for both apparatus (1) with and without the heat exchanger module (15, refer to Figure 1) is approximately 7 % at high temperature .

Referring now to Figure 6 showing the. thermal efficiency of the photovoltaic-thermal collector apparatus (1, refer to Figure 1) with and without the heat exchanger module (15, refer to Figure 1) . It was shown that thermal efficiency of photovoltaic-thermal collector apparatus (1, refer to Figure 1) with the heat exchanger module (15, refer to Figure 1) is much higher than the photovoltaic-thermal collector apparatus (1, refer to Figure 1) without the heat exchanger module (15, refer to Figure 1) . At mass flow rate of 0.049 kg/s, the percentage of increasing thermal' efficiency with the usage of heat exchanger module (15, refer to Figure 1) is almost 50%. The photovoltaic-thermal collector apparatus with the heat exchanger module (15, refer to Figure 1) is capable of producing maximum thermal efficiency of 85%.

While the preferred embodiments of the present invention have been described, it should be understood that various changes, adaptations and modifications may be made thereto. It should be understood, therefore, that the invention- is not limited to details of the illustrated invention shown in the figures and that variations in such minor details will be apparent to one skilled in the art.

Claims

WHAT IS CLAIMED IS:

1. A photovoltaic-thermal collector apparatus (1) comprising; a heat exchanger module (15);

a mono-crystalline silicon solar . cell photovoltaic module (16) ;

a blower ( 11 ) ;

a ducting (13); and

a variable voltage regulator (113) for controlling the speed of said blower (11); characterized in that, said heat exchanger module (15) having a cross- sectional honeycomb structure with an inlet (14) and outlet (17) for air flow.

2. A photovoltaic-thermal collector apparatus (1) as claimed in Claim 1, further characterized in that a flow meter (not shown) is provided for measuring speed of air at said inlet . (14) of said heat exchanger module ( 15 ) .

3. A photovoltaic-thermal collector apparatus as claimed in any of the preceding claims, further characterized in that a heater (12) is incorporated into said apparatus (1) for maintaining air temperature in the said inlet (14) of said heat exchanger module (15) to be equal with ambient temperature.

A photovoltaic-thermal collector apparatus (1) as claimed in Claim 3, further characterized in that a variable voltage regulator (114) is provided for controlling the operation of said heater (12).

A photovoltaic-thermal collector apparatus (1) as claimed in any of the preceding claims, further characterized in that said heat exchanger module (15) is installed horizontally into channel located at the back of said mono-crystalline silicon solar cell photovoltaic module (16).

A photovoltaic-thermal collector apparatus (1) as claimed in Claim 5, further characterized in that a stack of aluminum ( 18 ) -polyethylene (19) -aluminum sheet (110) is attached below said heat exchanger module ( 15 ) .

A photovoltaic-thermal collector apparatus (1) as claimed in any of the preceding claims, further characterized in that a plurality of type T thermocouple (not shown) is provided for measuring temperature of said inlet (14) of said heat exchanger module (15), said outlet (17) of said heat exchanger module (15), said, mono-crystalline silicon solar cell photovoltaic module (16) and said, aluminum sheet

(110).

A photovoltaic-thermal collector apparatus (1) as claimed in Claim 7,. further characterized in that a cardboard (111) is used to cover said outlet (17) of said heat exchanger module (15) from environment condition.

A photovoltaic-thermal collector apparatus (1) as claimed in any of the preceding claim, further characterized in that a pair of fans (112) is provided above said ducting to remove infrared radiation from halogen lamps of solar simulator. 10. A photovoltaic-thermal collector apparatus (1) as claimed in any of the preceding claim, further characterized in that said photovoltaic-thermal collector apparatus is. of the compact construction type. 11. A photovoltaic-thermal collector apparatus (1) as claimed in Claim 10, further characterized in that said photovoltaic-thermal collector .apparatus isused for solar energy harvesting.