Andreas Späth

The future is solar-powered

2014-04-28 09:45

Andreas Wilson-Späth

People who believe that the solution to our energy woes – the need to generate enough electricity without mucking up the climate – lies with renewable energy sources are frequently dismissed as idealists and dreamers.

“The sun doesn’t shine all the time and the wind doesn’t blow constantly – they’ll never satisfy our electricity demand”. That’s the chorus so-called realists who insist that we need fossil fuels (oil, coal, natural gas, fracked shale gas, tar sands, etc.) or nuclear energy to power our cities and factories repeat endlessly.

Ongoing developments in the field of renewables make such statements increasingly invalid. Even a cursory look at some of the advances and innovations reported just in the area of solar photovoltaic (PV) systems (the technology that uses solar cells to transform sunlight into direct current electricity) should convert the skeptics, even without taking into consideration similar progress in other fields from wind power to solar thermal energy.

Improved efficiency

Thin film solar technology devices can convert around 20% of the sunlight that strikes them into electricity, while the record for conventional silicon solar cells is in the 40% range. But new techniques and novel materials are constantly pushing up efficiency levels while decreasing production costs.

Incorporating lenses into solar cells to focus impacting light, and stacking various semiconductor materials sensitive to different wavelengths of light on top of one another, are just two examples of how more of the sun’s energy can be captured.

There is growing excitement about solar cells made out of a mineral called perovskite. Their efficiency record currently stands at around 15%, but scientists predict that it could reach 50% in the not too distant future. The promise is that light-weight and flexible perovskite solar panels can be manufactured more cheaply in high volumes than conventional silicon equivalents.

Solar power with little sun

Germany’s successful use of solar PV energy shows that the technology works even in places that aren’t very sunny. South Africa is blessed with sunshine and has exceptional solar power potential. If only we used more of it!

Recent developments mean that we will increasingly be able to harness the energy of sunlight even in relatively poor light and overcast conditions. One breakthrough that makes this possible involves organic photovoltaics (OPV) – solar panels made of organic superconductors that can be coated onto large areas and even 3D printed into different shapes.

While conventional silicon solar cells require direct light to operate, OPV panels generate electricity in diffuse and low-angle light. They’ll work on cloudy days, late in the afternoon, early in the morning and on winter days. OPV efficiency continues to improve and experts predict that in future they will be more flexible, thinner and cheaper to manufacture than silicon-based alternatives.

Solar power with no sun

But what about times when the sun don’t shine at all?

Federico Capasso, a professor at Harvard University, has proposed a somewhat more indirect method for gathering solar energy that is available day and night.

Much of the energy that hits the earth as sunlight during the day is constantly emitted back into space from the surface of the planet as infrared radiation. Capasso suggests that it should be possible to capture and use this energy with a device he calls an "emissive energy harvester".

Making solar power available as electricity when the sun’s down doesn’t have to be quite so exotic an affair, however. Researchers are steadily improving the capacity and performance of energy storage technology that does just that.

Colleagues of Capasso’s at Harvard, for example, have recently shown that flow batteries containing organic molecules called quinones can be used to store large quantities of energy at low cost in connection with both domestic and industrial-scale solar power installations. When surplus solar power is available the quinine molecules in large tanks are pumped with energy which can be released when there is no sunshine.

Community power

The sun bathes us in enough free energy every day to provide for all of our electricity needs. Morally, advances in harnessing this energy are making support for dangerous fossil fuel and atomic energy increasingly dubious.

Some of the most inspirational examples for making a solar-powered future a reality come from small communities, like the Bavarian village of Wildpoldsried which generates over 300% more electricity from solar panels and other renewable sources than it consumes, exporting the rest, and Balcombe in the UK [], a town at the centre of the British fracking boom, where defiant residents have started a cooperative with the long-term aim of producing all of their electricity using renewables.

- Andreas is a freelance writer with a PhD in geochemistry. Follow him on Twitter: @Andreas_Spath
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