Houston: Storing solar power for night-time use actually increases both energy consumption and emissions compared with sending excess solar energy directly to the utility grid, according to a new study.
Homes with solar panels do not require on-site storage to reap the biggest economic and environmental benefits of solar energy, researchers said.
They assessed the trade-offs of adding home energy storage to households with existing solar panels, shedding light on the benefits and drawbacks of adding storage considering today’s full energy grid mix. There is a growing interest in using energy storage to capture solar energy to reduce reliance on traditional utilities.
However for now, few homes have on-site storage to hold their solar energy for later use in the home. “The good news is that storage is not required to make solar panels useful or cost-effective,” said Michael Webber, professor at University of Texas at Austin in the US.
“This also counters the prevailing myth that storage is needed to integrate distributed solar power just because it does not produce energy at night,” said Webber. Webber and Robert Fares, a fellow at the US Department of Energy, analysed the impact of home energy storage using electricity data from almost 100 Texas households that are part of a smart grid test bed.
They found that storing solar energy for night-time use increases a household’s annual energy consumption — in comparison with using solar panels without storage — because storage consumes some energy every time it charges and discharges.
The researchers estimated that adding energy storage to a household with solar panels increases its annual energy consumption by about 324 to 591 kilowatt-hours. “I expected that storage would lead to an increase in energy consumption,” Fares said. “But I was surprised that the increase could be so significant – about an 8 to 14 per cent increase on average over the year,” said Fares.
The researchers also found that adding storage indirectly increases overall emissions of carbon dioxide, sulphur dioxide and nitrogen dioxide based on Texas grid mix, which is primarily made up of fossil fuels. The increase in emissions is primarily due to the increase in energy consumption required to account for storage inefficiencies, researchers said.
As storage affects what time of day a household draws electricity from the grid, it also influences emissions in that way, they said. If a homeowner is seeking to reduce their environmental footprint, adding storage would not make the household more green, but it should not be dismissed either. “Solar combined with storage is still a lot cleaner than having no solar at all,” Fares said. The study was published in the journal Nature Energy.