Storing renewables with aquifer thermal energy storage

Scientists at the US Department of Energy’s Lawrence Berkeley National Laboratory have proposed the use of aquifer thermal energy storage (ATES) as a way to store intermittent wind and solar power for seasonal thermal storage.

“We found that, with ATES, a huge amount of energy can be stored, and it can be stored for a long period of time,” said researcher A.T.D Perera. “As a result, the heating and cooling energy demand during extreme hot or cold periods can be met without adding an additional burden on the grid, making urban energy infrastructure more resilient.”

The researchers conducted a simulation with a stochastic optimization model and designed distributed multi-energy systems (DMES) that use ATES as long-term thermal storage. In the proposed system configurations, renewable electricity from wind and solar is used to pump water up from existing underground reservoirs and heat this water at the surface during the summer, or in times with high excess wind power. Then, the same water can be pumped back down to restart the cycle.

“It actually stays fairly hot because the Earth is a pretty good insulator,” said researcher Peter Nico. “So then when you pull it up in the winter, months later, that water’s way hotter than the ambient air and you can use it to heat your buildings. Or vice versa, you can pull up water and let it cool and then you can put it back down and store it until you need cooling during hot summer months. It’s a way of storing energy as temperature underground.”

The academics considered costs, grid-integration levels, and fuel consumption. They then designed a case study of a neighborhood in Chicago featuring 58 two-floor, single-family residences with typical residential heating and cooling systems.

“The results showed that adding ATES to the grid could reduce consumption of petroleum products by up to 40%, though it would cost 15 to 20% more than existing energy storage technologies,” the scientists explained. “But, on the other hand, energy storage technologies are having sharp cost reductions, and after just a few years of developing ATES, we could easily break even.”

The team presented its findings in “Enhancing flexibility for climate change using seasonal energy storage (aquifer thermal energy storage) in distributed energy systems,” which was recently published in Applied Energy.

“ATES will also make the future grid more resilient to outages caused by high power demands during heat waves – which happen quite often these days in many high-population U.S. areas, including Chicago,” they concluded. “Because ATES-driven cooling uses far less electricity than air conditioners, it only needs enough power to pump the water around.”