New Solar Panels Work at Night

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It’s something researches have been struggling with for some time now: how to create a solar panel that produces electricity at night. Adding this capability to a solar-based source of electricity could vastly improve the economics of going solar and reduce our dependence on non-sustainable fossil fuels. The good news is that significant forward strides have been made in technologies that piggyback energy storage technology onto solar photovoltaic or solar thermal systems. So the race is on to fully utilize every joule of energy sol provides us.

Solar Cells with Efficiencies of 46% 

The US Department of Energy’s Idaho National Laboratory in Idaho Falls says its new Thin Film Solar Technology that can actually produce electricity at night. Researchers maintain that their new thin film solar cells can achieve efficiencies that far surpass the current 20%-to-25% threshold of today’s most efficient solar panels. The new technology is capable of reaching solar cell efficiencies as high as 46%. Granted, some new technologies still in their infancy have claimed super efficiencies, but these, like the “hairy” nanowire-based solar panels, are far from being realized.

Nanoantennas Replace Solar Cells

The technique developed by scientists at the Idaho National Laboratory is radically different that most conventional solar cell technologies. It produces a flexible substrate with nanoantennas and eschews solar cells entirely. The specially designed nanoantennas capture the infrared range of the sun’s energy that ordinary solar cells are incapable of harnessing. So what’s truly amazing is that the unique materials in these antennas actually absorb the earth’s heat at night when it reflects this heat in the infrared spectrum. The good news is that researchers are close to producing these super-thin solar films that can be cost-effectively manufactured. The technique embeds square spirals of conducting metal onto a sheet of plastic, each spiral of metal can be regarded as a nanoantenna with the thinness of 1/25 the diameter of a human hair.

Rise of Solar Thermophotovoltaics

Storing electricity from solar panels is expensive and in many areas simply impractical. Solar thermal power uses a concentrator to focus sunlight, which heats water into steam to run turbines. Storing this heat energy in insulated containers is at best, twice as expensive as power generated from solar panels. This has given rise to panels that incorporate solar thermophotovoltaic cells. Such cells are capable of generating electricity at night. The challenge is for those panels to be able to trap the heat they absorbed during the day. One way is to give the emitter material enough mass so it heats up slowly and retains its heat after the sun goes down. So rather than getting a sudden flood of energy during daylight hours and zero energy at night, the material provides a steady flow of energy day and night.

Granted, the concept of solar thermophotovoltaics isn’t new. Today’s researchers are basically improving its performance. While early attempts at exploiting this technology yielded efficiencies of just 1%, new results have upped that to 3.2%.  Researchers believe that slight improvements could raise the bar to 20% efficiency, which would make the technology competitive with current PV panels. Some researchers believe that efficiencies could top 80%. That said, achieving a 20% efficiency in storing energy as heat and converting it to electricity gives solar thermophotovoltaics a leg up over a 20% efficient PV panel.

Being able to harvest energy day and night has enormous commercial advantages. While the principle of nanoantennas isn’t new, the manufacturing process is bold and state-of-the-art, one that allows a flexible and inexpensive material to absorb the full wash of energy the sun bathes onto our planet.

Posted on Wednesday, October 5th, 2016