Solar Power at Night

Researchers at the Department of Energy’s Idaho National Labs say they have solved one of solar energy’s biggest problems with a new kind of thin-film solar cell that will generate power at night.

Traditional photovoltaic solar cells absorb photons from visible sunlight, converting the absorbed energy into electricity.

The key technological breakthrough coming from Idaho Labs is a tiny nano-antenna that can absorb mid-infrared rays, otherwise known as heat. The Earth absorbs sunlight all day long, and emits infrared energy constantly.

These nano antennas are stamped onto a polyethylene sheet, and researchers said the production process is easy and inexpensive. Even better, they said the new design can capture up to 80 percent of the energy in the IR light, compared to photovoltaics, which are often only about 20 percent efficient.

Of course, there’s a snag. Once the nano antennas absorb all this energy, they begin to oscillate with alternating current at a trillion times per second; the researchers say they still have to come up with a new kind of rectifier that can convert that power into usable, direct current.

Existing rectifier designs can’t handle such high-frequency oscillation, and are way too big. The researchers now must create a nano-scale rectifier, which would have to be about 1,000 times smaller than commercial rectifiers that are currently available.