By Kim Robson:
Last November in Hembrug, Netherlands, more than 300 LED lights were illuminated by a Dutch company launching a new energy project called “Starry Sky.” What makes this electricity different is that it’s made by harnessing the energy of living plants. The company, Plant-e, envisions a future when people can use their yards to charge their electric vehicles. The technology also could supply power to some of the world’s poorest regions.
“Starry Sky” and lines of LED street markers near Plant-e’s Wageningen headquarters are the company’s first two
commercial installations using the emerging technology. Both lighting projects utilize native aquatic plants supplied by local greenhouses grown in two-square-foot plastic modular containers. The company also sells Wi-Fi hot spots, mobile chargers, and rooftop electricity modules — all fueled by the byproducts of living plants.
Here’s how it works:
Via photosynthesis, a plant produces sugars. The plant uses some of the sugars to grow, but it also discharges a lot of it into the soil as waste. As the waste breaks down, it releases protons and electrons. By inserting an electrode into the soil, the electrons can be harvested as electricity. The plant isn’t harmed by harvesting the electricity, and can keep growing while electricity is being produced.
The technology is not yet advanced enough to compete with solar panels and wind turbines. While it may not be practical in the United States, where households use high amounts of electricity, it could prove life changing in poorer regions of the world.
Just as with solar and wind energy, plant energy yields vary based on climate. In the Netherlands, Plant-e’s installations will be unable to produce electricity during the coldest part of winter because the technology doesn’t work when the ground freezes.
Plant-e’s co-founder and CEO, Marjolein Helder, plans to expand the technology to wetlands and rice paddies where electricity can be generated on a larger scale, bringing power to some of the world’s poorest places.
Helder says that a one-square-meter garden can produce 28 kilowatt-hours per year. By comparison, the average U.S. household in 2012 used 10,837 kilowatt-hours a year. To power a home in the United States, one would need about 4,000 square feet, about the size of a large backyard. But the average Netherlands household uses only 3,500 kilowatt-hours a year. And for the 1.4 billion people in Africa and Southeast Asia who have no access to electricity, the technology could mean a sea change in quality of life.
Next, Plant-e plans to use existing wetlands, peat bogs, mangrove forests, rice paddies, and river deltas to generate electricity by placing a tube horizontally below the surface, using the same process as the modular system. The company created a prototype tubular system last year.
“Modular systems are interesting, but you can only scale up to a certain size because it’s pretty labor- and material-intensive,” Helder said. “A tubular system can just be rolled out through the field and it just works because the plants are already there. So for the longer term, for the really large scale, that’s much more interesting.”