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Highly efficient solar cells -Possible or not?

In order for solar power technologies to become competitive with fossil fuels they will not only have to become cheaper than they are now but also much more efficient. Currently dominant solar power technology used in most of today's solar panels use the semiconducting material silicon to convert the sunlight into electricity. The problem is that solar cells can only use a small portion of available sunlight, with the rest just generating heat.

The scientists have calculated that this heat from unused sunlight accounts for a total loss of more than 50 percent of the initial solar energy reaching the cell. Researchers from all around the globe are therefore conducting many different researches with the goal of finding the way to somehow harvest this lost energy which would make solar cells more efficient.

The current solar power technologies require high temperatures to make conversion possible, and the main problem with this working principle is the fact that solar cell efficiency rapidly decreases at higher temperatures. This was a stumbling block to many different researches but not to scientists from Stanford as they have figured out the way to simultaneously use the light and heat of the sun to generate electricity. According to them this could result in doubled efficiency compared to today's technologies, and thus make solar power much more competitive with fossil fuels.

This new process is called "photon enhanced thermionic emission" (PETE). The key component of this process is coating a piece of semiconducting material with a thin layer of the metal cesium, because this enables the material to use both light and heat to generate electricity.

The difference between this new technology and currently dominant solar power technologies is the fact that while most silicon solar cells have been rendered inert by the time the temperature reaches 100 degrees Celsius, the "photon enhanced thermionic emission" doesn't hit peak efficiency until it is well over 200 degrees C.

Scientists have also explained that PETE devices would work best in solar concentrators (parabolic dishes), which can get as hot as 800 degrees C because this process performs best at temperatures well in excess of what a conventional rooftop solar panel would reach.

Conventional solar panel system never gets hot enough for their waste heat to be useful in thermal energy conversion, but the high temperatures at which PETE device performs are perfect for generating usable high temperature waste heat.

Nick Belosh, assistant professor at the Stanford University, the lead researcher of this study, said that "this process can get to 50 percent efficiency or more under solar concentration, but if combined with a thermal conversion cycle, could reach 55 or even 60 percent - almost triple the efficiency of existing systems".

Will this study turn out to be the first step towards the highly efficient solar energy cells? Potential is there, and theory works perfectly but implementation is really the key that separates success from failure. The Stanford team already expressed desire to design the PETE devices and implement them to existing systems so it will be interesting to follow their further progress.

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