A research paper from scientists at Swansea University describes their tool for analyzing thermodynamic limits of organic semiconductor-based photovoltaics (OPVs). One of the findings was that semi-transparent solar PV deployed in greenhouses may deliver comparable performance to conventional crystalline silicon PV.
September 13, 2024 Patrick Jowett
Scientists from Swansea University in the United Kingdom have developed a tool to help identify optimal photovoltaic materials for agrivoltaics.
The research paper “On the Performance Limits of Agrivoltaics – From Thermodynamic to Geo-Meteorological Considerations,” published in the journal Solar RRL, explores the thermodynamic limits of organic semiconductor-based photovoltaics (OPVs) and their potential performance as agrivoltaics.
The team developed a freeware tool that predicts the light transmission, absorption and power generation of different solar materials using geographical, physical and electrical measurements. They say it could be applied nearly anywhere in the world and to their knowledge, is the first accurate device-level model to predict the thermodynamic performance limits of various semiconductors for semitransparent agrivoltaics.
“This technology, which allows us to compare many types of PV material, could help us determine how we balance food production and renewable energy generation,” said Austin Kay, the study’s lead author.
The paper says the tool will be particularly valuable for molecular semiconductors such as organics and perovskites, “wherein tunable bandgaps and electro-optics can be manipulated and engineered.”
A press release from the university explains that some PV materials have a wide bandgap, which means the material absorbs higher-energy light with a shorter wavelength, typically blue light, while materials with a narrower bandgap absorb lower-energy, longer wavelength, typically red light. Such knowledge can help select the right materials for semi-transparent agrivoltaics, as crops mainly absorb red and blue light to photosynthesize, reflecting green light.
In the paper’s conclusion, the researchers explain that the active layers of semitransparent OPVs should be around 100 nm thick for optimal agrivoltaic performance, with the exact thickness required dependent on the optical and transport properties of a given device.
During their research, the team also defined a coverage factor (CF) for deploying PV cells on a protected cropping structure, such as a greenhouse. They found the light-utilization efficiency (LUE), which quantifies the amount of incident light converted to electrical power by PVs or made available to crops, of semi-transparent agrivoltaics based on OPVs is comparable with that of opaque solar cells that are based on inorganic semiconductors such as crystalline silicon or gallium arsenide.
“Overall, we found that state-of-the-art, inorganic PVs generate more power per square meter than semitransparent OPVs, but the CF-weighted LUEs of OPVs can compete with established inorganic systems,” the paper concludes.
The researchers add that other considerations can inform choices for agrivoltaics, including the stability of the device, the robustness of the protected cropping environment, the local climate, the time of the year, and the wavelength sensitivity of the crop. “It is never just a matter of maximizing transmission and power generation,” the paper says.
Earlier this year, a project led by Swansea University began exploring the potential of setting up manufacturing hubs for low-cost PV modules in Africa, Asia and the Indo-Pacific.
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