Seawater, humidity inspire new ways to generate power

The possiblity of a future power-availability crunch – spurred in part by a global increase in data usage – is driving researchers to get creative with a slew of new and modified ways to generate and store energy.

Ongoing projects include the use of seawater for batteries; grabbing ambient humidity; massive water storage systems for hydropower; and solar panels that work at night. Here are some details:

Batteries based on seawater

Seawater will provide “super-batteries,” says the University of Southern Denmark. Researchers there have been studying how to use sodium, which is abundant in seawater, as an alternative to lithium in batteries.

“Sodium is a very readily available resource,” the school says in a press release, and it can be easily extracted from seawater. Lithium, on the other hand, is a limited resource that’s mined only in a few places in the world, says research leader Dorthe Bomholdt Ravnsbæk of the department of physics, chemistry and pharmacy at the university. Batteries based on seawater would also alleviate the need for cobalt, which is used in lithium cells. The team in Denmark (working with Massachusetts Institute of Technology) believes it has come up with a new electrode material, based on manganese, that will make the seawater battery ultimately viable.

Using ambient moisture to generate power

Humidity captured with bio-electronics could end up being a viable power source for sensors, say some scientists.

“Harvesting energy from the environment offers the promise of clean power for self-sustained systems,” notes University of Massachusetts researchers in an article published in Nature. However, known technologies often have restrictive environmental requirements – solar panels that must be mounted outside, for example – that limit their energy-producing potential.

Moisture harvesting with thin-film, protein nanowires doesn’t have restrictive environmental requirements. Sustained voltages of about half a volt can be obtained from moisture present in normal, ambient air. “Connecting several devices linearly scales up the voltage and current to power electronics,” the Amherst group claims. “Our results demonstrate the feasibility of a continuous energy-harvesting strategy that is less restricted by location or environmental conditions than other sustainable approaches.”

Seasonally pumped hydropower storage 

On a larger scale, inland water storage could solve renewable power issues, say scientists at the International Institute for Applied Systems Analysis.

One big problem collecting power from the environment, as opposed to using fossil fuels, is where to store the on-the-fly electricity being generated. The Austrian organization believes that hydropower systems should be used to contain renewable energy. It’s cheap, for starters. In addition, seasonal pumped hydropower storage (SPHS) is better than wind or solar, the group claims, because it not only generates the power in real time as it’s needed, but also isn’t affected by variations— a windy day isn’t required, for example.

SPHS operates by pumping water into dammed, river-adjacent reservoirs when water flow is high but power demand is low. Water is then allowed to flow out of the reservoir, through turbines—similar to hydroelectric—when energy demand increases. Electricity is thus created. The group, in a press release related to a study just released, says the technique is highly economical, even including required land purchases, excavation and tunneling.

Nighttime, anti-solar cells

Contrary to popular belief, photovoltaic solar panels don’t actually need full sun to function. Cloud cover allows some to work just fine, just not as well. Nighttime photovoltaic, however, is something more radical:

The earth should be used as a heat source, and the night sky a heat sink, say Jeremy Munday and Tristan Deppe of the department of electrical and computer engineering at University of California, Davis. They shared their idea for nighttime photovoltaic cells in an abstract of a paper published by American Chemical Society’s ACS Photonics.

What they are suggesting is using thermoradiative photovoltaics, where deep space radiative cooling (which I’ve written about before) is combined with photovoltaics. Current is created as infrared light – or heat, in other words – is radiated into extremely cold, deep space.

“Similar to the way a normal solar cell works, but in reverse,” Munday says of their anti-solar panel concept, quoted in a UC Davis news article.