How to make PV solar cell work with efficiency at hot climate,
Efficiency of each photovoltaic cell decrease with increasing of temperature. Good technology is monocrystalic cells (high efficiency) with cooling of back side.
Amorphous PV modules is suitable for hot Iraq climate (Although it's has low efficiency) due to the drop of voltage with temperature is smaller than the Si-crystalline modules which have high drop Temperature coefficient for voltage
CIGS multijunction PV cells have highest efficiency and a good cooling mechanism available
Dear Dr. Dhafer AL-Shamkhee
An important question
I think it is better to take advantage of solar energy directly, such as solar chimneys, etc.
The atmosphere of Iraq in addition to the highest DBTs and dust problem are two of the main reasons for reducing the efficiency and life of solar cells.
Best regards
The loss of efficiency with temperature arises because of the shunt diode which obeys - roughly - the diode equation; so as temperature rises the voltage across the diode, for a given current, will drop. So the cell output voltage drops. Really the only way round this is cooling. However, the problem is that 80% (roughly) of solar energy on the cell heats it up uselessly and getting rid of this energy with a heat pump will use most if not all of the cell's output. In countries like Iraq where the low altitude ambient air temperature can be very high, there isn't much you can in practice do. Up in the mountains however the air temperature is a LOT less and here solar cells will work extremely well.
Dear Dhafer,
The temperature affect the the generated optimum power of the solar cells due to the thermal generation of the electron hole pairs which increases slightly the photo current while decreasing relatively appreciably the open circuit voltage.
As the intrinsic concatenation of the material of the material at room temperatures decreases the solar cells made from this material will be less sensitive to temperature variation. So GaSA is less sensitive to temperature rise.
So, it is used to work in relatively high temperature environment like space.
Theoretically materials with higher bandgap Eg with be more robust against temperature rise. However it photoconvestion efficiency will be smaller because it s response to photons will start at higher photon energies wasting part of the incident radiation.
I think as the colleagues hinted the silicon solar cells are a good solution and can be used also in Iraq. In Saudi Arabia there is the solar village with Silicon PV generators they are working well. I think the environment in Iraq is less aggressive than in Saudi Arabia. In the upper Egypt in Aswan, there are si solar cell PV generators working good.
I find the proposal of Tonny is good.
For silicon it is so that its efficiency decreases as about .004 per 1 degree centigrade rise. Assuming 60 degrees above 25 degrees then the efficiency will decrease only by 2.4 percent which will be compensated by the stronger solar radiation.
I think the problem is the module lifetime because of the excessive thermal stresses as the temperature changes in a large margin between day and night.
To overcome this problem i think we have to change the encapsulation technology of the solar cells which is the panel making.
I proposed encapsulation which relief the thermal stresses and repairable.
Please see the link:Chapter Solar cells and arrays: Principles, analysis and design
Best wishes
high efficiency thin film PV solar modules like CIGS modules which have small value of temperature loss coefficient not exceed than 0.32%/C in compare with crystalline silicon technology as well as u can use HIT silicon PV solar modules
Dear Dr. Dhafer
The attached search is related to your question.
Kind regards..
https://www.researchgate.net/publication/305641928_Operation_of_Solar_Energy_Systems_in_Hot_Climate
Dear Dr. Dhafer
There are several ways to minimize the negative effects of high temperatures on PV system such as Iraq climate as follows:
- By fixing the appropriate air gap between PV panel and roof
to allow convective air flow to cool the panels down.
- Ensure that panels are constructed with light-colored materials, to reduce heat absorption .
Best regard ...
Dear Mr. Salah, thank u for your answer, but I would like to clarify some issues related to your suggestion , firstly
- By fixing the appropriate air gap between PV panel and roof to allow convective air flow to cool the panels down
U know well the ambient temperature in middle and south of Iraq in summer not less than 45 centigrade and most installer of PV Solar system in our country set the tilt angle of the panels at 30 degree with horizon (according to the Latitude of the sites) therefore I think this solution not enough to solve the problem .
Ensure that panels are constructed with light-colored materials, to reduce heat absorption
all designers and manufacturers of PV Solar panels do hard work to increase the absorption of incident solar radiation on PV Surface panel to increase input power to get maximum power yield , therefore there is no real relation between the colors of anti reflection coating which covered the front surface of panel and the heat effect.
finally u can check the heating effect on the performance of the panel from the value of temperature Loss Coefficient for power which printed on the PV nameplate
Regards
Dr. Naseer Alsudany
Dear Furkan,
in most cases the monocrystalline panels have high value of temperature loss coefficient of power when u want to get less value u will find it in poly crystalline but the best minimum values u can get it in thin film panels like amorphous silicon, CdTe, CIS, CIGS, HIT Si, .........
and this is related to the geometry of the PN junction of the solar cells
Regards
Dr. Naseer
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