Decarbonising the grid means storing energy from renewables. Aquifers can do that, suggests an ASHRAE article written by Aliyah Kovner. This is part one of a two part article.
Aquifer thermal energy storage (ATES) uses naturally occurring underground water to store energy that can be used to heat and cool buildings.
About 12% of the total global energy demand comes from heating and cooling homes and businesses. A new study suggests that using underground water to maintain comfortable temperatures could reduce consumption of natural gas and electricity in this sector by 40% in the United States. The approach, called aquifer thermal energy storage (ATES), could also help prevent blackouts caused by high power demand during extreme weather events.
“We need storage to absorb the fluctuating energy from solar and wind, and most people are interested in batteries and other kinds of electrical storage. But we were wondering whether there’s any opportunity to use geothermal energy storage, because heating and cooling is such a predominant part of the energy demand for buildings,” said first author A.T.D Perera, a former postdoctoral researcher at Lawrence Berkeley National Laboratory (Berkeley Lab) now at Princeton University’s Andlinger Center for Energy and Environment.
“We found that, with ATES, a huge amount of energy can be stored, and it can be stored for a long period of time,” Perera said. “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 study, published this week in Applied Energy, is the first examination of how ATES could fit into the larger goal of decarbonising U.S. energy systems by storing intermittent renewable energy to use when the sun isn’t shining and the turbines aren’t spinning. After building a comprehensive technological and economic simulation of an energy system, the authors found that ATES is a compelling option for heating and cooling energy storage that, alongside other technologies such as batteries, could help end our reliance on fossil fuel-derived backup power and enable a fully renewable grid.
GIF showing aquifer geothermal energy storage technology in the summer and in the winter.
Aquifer thermal energy storage (ATES) uses naturally occurring underground water to store energy that can be used to heat and cool buildings. When paired with wind and solar energy, ATES becomes a zero-carbon option for temperature regulation. These illustrations show how the water is moved upward for heating in the hot months, then pumped back down and stored until winter, when the (still) warm water is brought back up to heat buildings. The same process occurs in winter, leading to stored cold water to use in summer months. (Credit: Jenny Nuss/Berkeley Lab)
Putting thermodynamics to work
ATES is a delightfully simple concept that leverages the heat-absorbing property of water and the natural geological features of the planet. You simply pump water up from existing underground reservoirs and heat it at the surface in the summer with environmental heat or excess energy from solar, or any time of the year with wind. Then you pump it back down.
“It actually stays fairly hot because the Earth is a pretty good insulator,” explained co-author Peter Nico, deputy director of the Energy Geosciences Division at Berkeley Lab and lead of the Resilient Energy, Water and Infrastructure Domain. “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.”
ATES is not yet widely used in the United States, though it is gaining recognition internationally, most notably in the Netherlands. One major perk is that these systems get ‘free’ thermal energy from seasonal temperature changes, which can be bolstered by the addition of artificial heating and cooling generated by electricity. As such, they perform very well in areas with large seasonal fluctuations, but have the potential to work anywhere, so long as there is wind or solar to hook up to. In regards to other impacts, ATES systems are designed to avoid impinging upon critical drinking water resources – often the water used is from deeper aquifers than the drinking water supply – and do not introduce any chemicals into the water.
Supplied by Cooling Post and edited by Eamonn Ryan.