Novel Power-to-Gas Tech Begins Testing in the US
A new pilot combines hydrogen, microbes and biogas to perform energy storage.
Last month, a team of researchers and engineers quietly installed a first-of-its-kind energy reactor on a campus of a government lab just west of Denver, Colorado. The device — a 25-foot-tall, thin mass of industrial silver pipes and tanks — is a test of a rather unusual way to store energy using microbes, hydrogen and clean electricity.
Similar technology is being tested in pilot projects across Europe, but the reactor in Colorado is one of the only ones operating within the U.S. If the process, known as “power-to-gas” by those in the industry, is able to be deployed at a bigger scale and at a lower cost it could some day offer a solution to store large amounts of electricity produced by wind and solar over long periods of time.
For now, it’s a novel experiment, at least in the U.S. “It’s pretty slick,” said Kevin Harrison, senior engineer for the National Renewable Energy Labs, describing the new reactor. NREL worked on the project in tandem with Southern California Gas Company and engineering firm Burns & McDonnell.
The project works by taking electricity, which can come from excess wind and solar, to power an electrolyzer that splits water to make hydrogen. The hydrogen is then combined with carbon dioxide and fed into a reactor filled with microbes.
On NREL’s campus, the gases are added to the bottom of the reactor and as they float to the top, paddles slowly spin and break them up. The hardest part is breaking up the bubbles so that they’re small enough for the bugs to eat them, explained Harrison.
The microbes, which aren’t genetically modified, wake up and start consuming the gases at around 120 degrees Fahrenheit. After eating the gases, they spit out methane, commonly called biogas. The team chose these microbes partly because they can do the process over and over again. “They’re a tough bug,” noted Harrison.
The biogas can be used like regular fossil-fuel based natural gas to heat homes and businesses. It can also go directly into the natural gas pipeline network without needing to be cleaned up, researchers say.
Gas utility Southern California Gas Company, a subsidiary of Sempra Energy, has a keen interest in new ways to produce and use biogas. It’s also the same company that suffered a massive gas leak in late 2015, which is thought to be the largest methane leak in U.S. history.
New technology could help the gas giant be more environmentally friendly, and the technology has promise to make wind and solar more competitive.
The idea is that electricity for power-to-gas projects would come from a solar plant or a wind farm when they’re producing excess low cost energy — during a windy night or a sunny afternoon, for example. Instead of wasting that electricity, it could be stored for weeks or even months and used at a later date in the form of hydrogen or biogas.
Other power-to-gas projects eschew the use of microbes. A demonstration project on the University of California (UCI), Irvine campus, also supported by SoCalGas, takes excess solar energy from solar panels and powers a 60-kilowatt electrolyzer to make hydrogen. The hydrogen can be piped into the existing natural gas infrastructure.
Jack Brouwer, associate professor of mechanical and aerospace engineering at UCI, said the demo project on the university campus suggests that power-to-gas tech can be used to provide very fast ramp rates, like when a cloud goes over solar panels.
It also suggests that storing energy as hydrogen could be cheaper than batteries on a large scale and can be used to store energy seasonally. “The energy could be produced in January and used in June,” said Brouwer. Batteries aren’t efficient enough to do that economically, he argued.
