As countries around the world try to move away from traditional energy sources and cut carbon emissions, it is hoped that renewable sources of energy will hold the key. However, intermittent sources of energy like wind and solar sometimes generate more energy than is needed by consumers, and storing that extra energy in batteries seems like the obvious solutions. A new study from Stanford University suggests that unless technology improves significantly, battery storage may not be the best way of dealing with those surpluses.
“We looked at batteries and other promising technologies for storing solar and wind energy on the electrical grid,” said Charles Barnhart, the lead author of the study and a postdoctoral scholar at Stanford’s Global Climate and Energy Project (GCEP).
“Our primary goal was to calculate their overall energetic cost that is, the total amount of fuel and electricity required to build and operate these storage technologies. We found that when you factor in the energetic costs, grid-scale batteries make sense for storing surplus solar energy, but not for wind.”
The study, supported by GCEP, was published in the online edition of the journal Energy and Environmental Science.
Exploring Other Options
The researchers in the study also looked at other options for storing renewable energy, like pumped hydroelectric storage, a method that uses surplus electricity to pump water into a reservoir. Once demand increases, the stored water can be released through turbines to generate electricity.
“Pumped hydro is used in 99 percent of grid storage today,” Barnhart said. “It works fantastically from an energetic perspective for both wind and solar. Its energy return on investment is 10 times better than conventional batteries. But there are geologic and environmental constraints on where pumped hydro can be deployed.”
In addition to storage, there are other options for improving grid efficiency. “Energy that would otherwise be lost during times of excess could be used to pump water for irrigation or to charge a fleet of electric vehicles, for example,” said GCEP postdoctoral scholar Michael Dale, a co-author of the study.
However, it is important for society to be energy-smart about implementing new technologies, Barnhart added. “Policymakers and investors need to consider the energetic cost as well as the financial cost of new technologies,” he said. “If economics is the sole focus, then less expensive technologies that require significant amounts of energy for their manufacture, maintenance and replacement might win out even if they ultimately increase greenhouse gas emissions and negate the long-term benefits of implementing wind and solar power.”
“Our goal is to understand what’s needed to build a scalable low-carbon energy system,” said co-author Sally Benson, the director of GCEP and a professor of energy resources engineering. “Energy return on investment is one of those metrics that sheds light on potential roadblocks. Hopefully this study will provide a performance target to guide future research on grid-scale energy storage.”
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