03-05-2021 | | By Sam Brown
Recently, Fraunhofer ISE announced that it had developed the first solar cell with an efficiency of 35.9% beating all current records. So what challenges do typical solar panels face, what has the research team achieved, and could they replace panels of the future?
Fighting against climate change presents the challenge of finding alternative renewable energy sources. For example, wind turbines allow us to harness the power of the wind while dams harness the power of gravity. However, solar panels allow us to take advantage of the largest renewable energy source; the sun.
At 1,000W per square meter, the Earth receives a fair amount of energy from the sun, and it is this energy that powers life on Earth. This energy can be extracted using solar panels that directly convert solar radiation into electricity, but multiple challenges are faced when using solar panels.
The main concern with solar panels is the technology used by the solar panel; polycrystalline or monocrystalline. Polycrystalline solar panels are made using lower-grade silicon containing multiple crystals of silicon (hence polycrystalline). Monocrystalline solar panels, however, are made from single pieces of silicon crystal. As a result, polycrystalline solar panels are cheaper than monocrystalline panels, but their lower efficiency makes them larger. The efficiency of polycrystalline panels typically falls between 13% to 16% whereas monocrystalline efficiency falls between 15% to 20%.
Recently, researchers from the Fraunhofer Institute for Solar Energy Systems ISE has announced the development of a solar cell with an efficiency of 35.9%. Compared to standard cells with efficiencies of 15%, this is a major leap in the development of solar technology.
The new cell, however, is very different from a typical product panel. Instead of using a single PN junction with a back reflector, the cell uses a multi-junction design that layers multiple different PN junctions on top of each other. These extremely thin layers used different semiconductor materials to create junctions that have different energy bands. As a result, more photons of different frequencies can be more readily absorbed by the cell, and therefore convert more of the incident energy into electricity.
According to the researchers, the key to the increased efficiency in their solar panel comes from gallium-indium-arsenide-phosphide as the middle semiconductor layer. Researchers from the Tampere University in Finland have developed another multi-junction solar cell with a maximum theoretical efficiency of 50% showing that solar panel technology has a long way to go.
The most obvious reason for developing more efficient solar panels is to improve the energy density of solar panels. As the efficiency of a solar panel increases, the less space the panel needs to take up for the same power output. But, of course, typical solar installations would translate increased efficiencies directly into greater power output instead (as all the available space would be used up).
The second reason for increasing solar panel efficiency is to help reduce the cost of solar panels. As the efficiency increases, the size of such panels can be decreased. Therefore, newer panels can be made smaller and therefore use less material. Furthermore, replacing older technology with newer technology helps increase the viability of the new technology (economically), and result in better power solutions for the future.
The third reason for increasing solar panel efficiency is the reduction in the weight of the final panel. As the world moves towards electric vehicles, there is a demand even to make aircraft battery-powered, and such aircraft could have panels mounted on them (either to increase the range of the craft or power it outright). However, low-efficiency panels are far heavier than more efficient panels and thus not practical for flying crafts. The use of more efficient panels reduces the overall weight (or increases the overall power depending), making the use of solar panels on aircraft more likely.