Because roof space is limited, the amount of the sun’s energy that can be extracted per square metre matters.
Plants typically extract 5% of the sun’s energy, and most roof solar panels on the market extract between 14% and 22%, although figures vary.
Last October, the website Mashable reported that SolarCity, whose chairman is Elon Musk, had launched a rooftop solar panel with a peak efficiency of 22.04%, claiming it was the world’s most efficient rooftop panel.
Insolight, a startup supported by Switzerland’s EPFL in Lausanne, has now come up with a panel that is 36.4% efficient, double the current average. This result, which could be a world record, has been validated by the Fraunhofer Institute, an independent lab based in Germany.
The efficiency of a photo voltaic solar panel is calculated by taking the amount of electricity it produces divided by the energy it is exposed to. Energy exposure is directly related to the panel’s surface area.
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Solar cells have been invented with efficiency greater than 36.4%. For example the Fraunhofer ISE/Soitec cell, which was developed with input from the same lab that tested a prototype of Insolight’s panel, is 46% efficient. However, there is a difference between a solar cell and a solar panel. A solar panel is an arrangement, or array of cells. Solar cells are an element of a solar panel, and only one determinant of its overall efficiency.
So how does Insolight’s solar panel work?
Plastic magnifying lenses concentrate the sun’s rays onto small pieces of costly high-performance solar cell technology normally reserved for spacecraft. The lenses work like funnels for the sun’s rays. Without these funnels the supercell technology would only be used to a small fraction of its potential. In addition, the team invented a system that adjusts the lenses’ angle as the sun moves, further increasing efficiency. This patented micro-tracking system moves several millimetres a day in line with a real time sensor that tracks the sun’s location overhead. These two innovations together deliver the panel’s high efficiency.
One of the strengths of Insolight’s technology is that it will soon be ready to be used in the mass production of roof solar panels.
Speaking to the company, journalist Cecelia Carron says that the founders are convinced that their solar panels will lower the price per kWh paid by consumers. The system will probably be a little more expensive to buy, “but this will be quickly offset by the additional energy that will be generated,” says Florian Gerlich, COO.