Increasing solar light to electricity conversion to new record efficiency

Optics of the spectrum splitting prototype, modeled in the 3D ray tracing software Zemax. Incoming sunlight in a solar power tower is reflected down to a silicon solar cell receiver. Credit: University of New South Wales

Solar light is a continuous source of energy, so well harvested by plants all over the world. Actually the "efficiency" of conversion of solar light to chemical energy (that is what the plant photosyntheses process does) is not so efficient, around 5% (from 3 to 6% actually). Researchers capability is way above that. Already in the 80ies photovoltaic panels had an efficiency in the order of 20%.

The problem is that plants are converting solar energy into chemical energy (sugar) that is easily stored and and way more efficient than out devices in using such energy. In addition, solar energy conversion has to compete with other sources of energy in economic terms. Hence the need for greater efficiency in conversion from solar light to electricity.

Researchers at the University of New South Wales, Australia, have demonstrated a way to push the conversion energy to 40%, a new world record in this field

What they did was to create a splitter of light wavelengths funnelling the ones that are used to convert sun light into electricity to today's commercial photovoltaic panels and using the others in different photovoltaic panels. 

The issue they are tackling is that it is too difficult to produce a photovoltaic panels that can use all the wavelengths present in a Sun beam (this is also true for leaves: they only capture a subset of the wavelengths, actually a smaller one than our photovoltaic panels and that is part of the explanation of the very low energy conversion efficiency). There have been, particularly in these last years, several attempts to manufacture solar panels that can capture wider ranges of wavelengths but that is increasing their cost to the point that the increase in efficiency is not sufficient to outbalance the increase in manufacturing cost.  On the other hand, it is cheaper to manufacture different types of panels that can capture different wavelengths. The problem then is how to split incoming sun rays in such a way that the appropriate wavelengths hit the panel most sensitive to them.

Researchers at UNSW have created such a wavelengths splitter and demonstrated it in a location near Sydney, Australia, achieving a 40% energy conversion efficiency.

This has been confirmed in an independent experiment in the US.

Of course, now it is a matter to see that the total cost of the increased number of panels and the splitter is below the valued of the increased efficiency...

Still, I like the ingenuity of researchers to approach a problem and finding alternative solutions.

Author - Roberto Saracco

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