Optical filters keep PV modules cool in two ways, extending lifetime
Result can be a very large 80% (1-sun) and 260% (multisun) increase in PV module lifetime.
|In one of two different ways to keeps solar cells cool, nonabsorbing optical filters are used to block photons with energy below the PV bandgap energy (reddish green) from reaching the PV module, while allowing the more-energetic photons (purple) to reach the module. Two configurations are shown: 1) nonconcentrating PV module with a filter that reflects subbandgap photons; and 2) concentrating setup with a filter that transmits subbandgap photons. (Drawing by John Wallace, adapted from Ref. 1)|
Two optical methods of passively reducing the operating temperature of photovoltaic (PV) modules could substantially reduce the total cost of solar installations by extending their lifetimes, according to researchers from Purdue University (West Lafayette, IN) and the National Renewable Energy Laboratory (NREL; Golden, CO).1
In the first method, subbandgap absorption in the semiconductor PV material is reduced by adding a nonabsorbing spectral filter to keep the offending spectral bands from being absorbed by the PV material. The second method consists of enhancing thermal radiation from the PV material to the surroundings by tailoring the spectral emissivity of the PV module.
These alterations can cool nonconcentrated (1-sun) and low-concentrated PV modules by up to 10°C and 20°C, respectively, say the researchers. The result is, respectively, up to a 0.5% and 1.8% efficiency increase and a very large 80% and 260% increase in PV module lifetime.
These results apply for a wide range of semiconductor PV materials, including silicon (Si), gallium arsenide (GaAs), cadmium telluride (CdTe) and copper indium gallium selenide (CIGS).
To come to these results, the researchers did a number of opto-electro-thermal simulations, in addition to accumulating data from previous research efforts.
1. Xingshu Sun et al., arXiv:1701.01678v1 [physics.optics]; 6 Jan. 2017.