Engineering news
Their research, published in conjunction with researchers at the University of Mannheim in Germany, is the wider use of integrated reversible power-to-gas systems that can turn electricity into hydrogen, and then convert that hydrogen back into electricity when power prices spike.
A new study published in Nature Communications assessed the potential, and found that even during periods of surging prices such fuel cells could be an economically viable source of backup electricity. By being able to switch directions, the entire system can run closer to full capacity, reducing the costs of producing both carbon-free hydrogen, and carbon-free electricity.
“The global movement toward renewable energy sources leads to power markets becoming increasingly volatile,” says Stefan Reichelstein, a professor at Stanford Graduate School of Business and a senior fellow at the Precourt Institute for Energy. “Our work shows that reversible power-to-gas systems are well on their way to becoming a cost-effective technology for smoothing power supply and for linking the electricity and hydrogen markets.”
Integrated reversible fuel cells are already on the market, but they are rarely used for this purpose – it's usually been thought that they're too expensive because of the expensive turbines required, and which sit idle much of the time. But, the researchers found that's not as much of a problem for newer systems. “When you look at the economics, the fundamental advantage is the flexibility to operate in either direction, which allows higher capacity utilization,” says Gunther Glenk, an assistant professor at the University of Mannheim, who teamed up with Reichelstein.
The researchers developed an analytical model based on actual market conditions in Texas and Germany, both of which have had gas-to-power projects for a number of years. In previous work, Reichelstein and Glenk showed that it was possible to produce hydrogen from electricity for about $3 per kilogram. That’s roughly in line with the prices that lower-volume buyers pay, though too high for large-volume customers.
The new study looks at the other side of the process, converting hydrogen back into electricity. In effect, says Reichelstein, the integrated reversible systems can help solve two problems at the same time: how to get economic value from renewable electricity when it cannot fetch a good price; and how to smooth out volatility in electricity markets. And both of those solutions help reduce carbon emissions.
“In the context of the transition to renewable energy, people are sometimes afraid of having a higher share of intermittent renewables,” says Glenk. “That needn’t be the case if these reversible power-to-gas systems were deployed at a large scale.”
Over the coming years, says Glenk, reversible power-to-gas systems could bring down the cost of carbon-free hydrogen and spur its wider use as a fuel. Steel producers, for example, are actively looking at hydrogen as a substitute for coal or natural gas.
“At the same time, lower prices for hydrogen will allow integrated, reversible power-to-gas systems to more often switch to power generation,” says Glenk. “The inherent flexibility of such systems may be a game changer.”