Meeting current energy demands without the past impacts on ecosystems is a global goal without easy solutions. Hunt is among a plethora of creative scientists and engineers around the world who are devising regenerative methods of creating and storing energy. Here are a few of those innovative ideas.

More solar energy reaches the earth from the sun in an hour than all humans consume in a year. Solar panels in space can power facilities in space, but what if it was possible to send all that energy back to Earth?

A team at Caltech under the SpaceSolar Power Initiative has been researching this question since 2015. Radio wave generators could send down electricity from space. Solar cells in space could produce power while sunlight on Earth is unreliable.

The work is ongoing, but Florian Bohn, one of the lead scientific researchers on the project, says he believes one component is ready for market: targeted wireless power.

“It’s effectively like shining a light from the generator unit to the receiver unit. The difference from a light bulb, though, is that we have electronic control of where to direct the light,” Bohn says in an interview.

His company, GuRu, has created two products for households and offices that aim to reduce reliance on the metals in wiring and batteries. Less wiring can shrink demand on copper mines, which in the past have devastated previously pristine forests and left waste behind. Reduced reliance on batteries can also shrink the pressures on lithium, cobalt and nickel sites around the world.

“We call our era a wireless era, but we still have a lot of wires,” Bohn says.

With a few generators that can fit in your hand installed around an office, warehouse or home, your devices would never be more than seconds from a power source. Batteries could shrink in size, and fewer would turn landfills into toxic waste.

Durian and jackfruit batteries

A Dongria woman collects wild jackfruit to sell in the market. Image by Indrajeet Rajkhowa.
A Dongria woman collects wild jackfruit to sell in the market. Image by Indrajeet Rajkhowa.

Vincent Gomes tried squashes — zucchini, eggplant, pumpkins — but none could quite mimic a battery. As an engineering professor at the University of Sydney, he was sure there was a fruit that could store electricity on par with a lithium-ion battery. Most fruit (and potato) batteries use the presence of acid to store energy, but these use porous nitrogen structures.

He then looked to the smelly, rotting carcasses of gobbled up durian and jackfruit, football-sized multi-seed fruits from South and Southeast Asia. For some they are too stinky to eat, for others they are a gourmet delicacy. If the technology can be scaled up, durian and jackfruit could also be used to make batteries that can charge up your phone in less than a minute.

“Other batteries use long expensive processes with nasty chemicals, but this uses a green method,” Gomes says. It’s a method, he adds, that is not particularly onerous.

The technology still lets you feast on the gooey seeds of a durian, which can weigh more than 3 kilograms (7 pounds), or a jackfruit, which can be a several times heavier. After being eaten, the inner, inedible core (full of proteins and uniquely structured nitrogen chains) is sent to a lab. There, scientists cook down the core into highly porous carbon aerogels and form them into super-capacitors, which are electrodes able to store and release energy smoothly.

While current modern batteries can wear down after several hundred charges, durian and jackfruit batteries can last tens of thousands of charges, Gomes says.

“According to our estimates, we wouldn’t need a large amount of durian or jackfruit,” he said. A single tree could over its lifetime provide hundreds of batteries.

One of the advantages of the technology is the rapid discharge of electricity, which can be useful not only for convenience in charging your personal devices, but also in renewable energy technologies that need to store electricity for a long time before filling high demand.

“You already have a nice template provided by nature that has evolved over millions of years into these fruits.”

The team has received a fair amount of interest from companies in Asia, which will shoulder the next task of development and safety testing, so that the technology can be used wherever there is a durian or jackfruit tree.

Gravity storage

Storing a ball on a ledge requires only that the ledge stays put. Gravity acts on the ball the whole time, and as long as it remains elevated it holds potential energy, i.e. the tendency to fall to the ground. Give it a push off the ledge, and that potential energy is converted into the kinetic energy of an object in motion. In that sense, then, the ledge stores energy like a battery, which can be released on demand.

Engineers believe the potential energy of height differences can work as an efficient storage mechanism for renewable energies. When sources like solar or wind overproduce, that excess energy can be used to lift heavy objects high. When those sources underproduce, dropping the objects could power a city.

That’s the idea of several start-ups. One of them, Energy Vault, has designed a skyscraper-like gravity storage tower. When there is little energy from other sources, simply drop concrete weights to power a turbine. The energy could fill the gap left by variations in renewable energies, just as a battery would.

Another company, called Heindl Energy, plans to dig into the ground, where a “very large rock mass” would be lifted by water pumps and dropped to produce up to 8 gigawatt-hours of electricity. Other companies are aiming for smaller-scale applications or hope to begin with abandoned mine shafts, which provide readily available deep holes at sites around the world.

Hunt, of the IIASA, has investigated a mid-range gravity storage device to close the small gap between cheaper batteries and hefty infrastructure projects. Using available topography, a renewable but variable energy source could lift sand, which is cheaper than other proposals for concrete, and release it when necessary.

For example, in communities within the Arctic Circle, solar energy is abundant in the summer, but nonexistent in the winter. At that time, large reservoirs of cheap sand moving downhill could provide electricity.

There are few places where mountain gravity would outperform other energy storage devices, Hunt says, but scientists recognize that local and hyper-local power solutions will be necessary to clean up energy use.

“It may not be the best solution for some places,” Hunt says. “You just hope that your idea will be used at some point and some time, but that’s another question.”

Banner image: Durian fruit. Image by Panumas Nikhomkhai via Pexels.

Article published by Genevieve Belmaker
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