January 25, 2021 — The U.S. Department of Energy (DOE) has awarded $950,000 in funding to three energy storage research projects led by Southwest Research Institute. SwRI will use novel materials and technologies to develop and integrate thermal, mechanical and chemical systems to demonstrate methods of storing solar and wind power to enhance the reliable and predictable operation of the utility grid.
Natalie Smith, an SwRI senior research engineer, will lead a feasibility study for the integration of a pumped-heat energy storage system into a fossil fuel-fired power plant. Supported by $200,000 in DOE funding, the study is aimed at addressing the timing mismatch between supply and demand that limits the dependability of renewable energy sources like solar and wind power and stresses the electricity grid.
“When the sun goes down, most people are heading home from work to cook dinner, watch television, etc.,” Smith said. “This huge increase in power demand occurs when solar resources are no longer available and forces communities to rely on fossil-fired power plants. These plants operate at low load during the day when solar energy is high, and then must ramp up quickly to higher powers at peak times. This varying operational profile results in the burning of more fuel and the creation of more harmful emissions instead of operating as designed at efficient baseload. We want to be able to use solar and wind power when the sun isn’t shining and the wind isn’t blowing.”
Smith will integrate a pumped-heat energy storage system with an existing fossil-fired power plant.
“This system uses technology that we already use in power generation: turbines, compressors and heat exchangers,” Smith explained. “When there’s excess power, from renewable or fossil fuel sources, we use that energy to run a heat pump, which creates both hot and cool energy storage, similar to the way a refrigerator works. That hot and cold energy goes into very well-insulated tanks to be used at peak demand hours to generate power.”
SwRI senior research engineer Joshua Schmitt, supported by $250,000 from the DOE, is leading the development of an advanced hydrogen energy storage system using aerogel in a cryogenic flux capacitor (CFC). This project uses the natural phenomenon of physisorption, a novel method originally developed by NASA to mechanically store molecules on the surfaces of a solid material.
“Physisorption begins with this phenomenon in the natural world that occurs when a gas or fluid binds itself to a material that has a high surface area, like a sponge that is very porous,” Schmitt said. “To take advantage of this and maximize the density of storage, we use complex materials with extremely high surface areas to store the hydrogen gas.”
By storing the gas in these porous materials, the hydrogen reaches a density that is close to its liquid state. Commonly, to reach this state, hydrogen gas must be pressurized in thick-walled containers or kept at temperatures near absolute zero, which is costly and requires a large amount of energy to maintain.
SwRI will use the synthetic, highly-porous aerogel material to capture the hydrogen gas produced by an electrolyzer cell to test the rate at which the fuel flows and can be stored. The energy storage system is designed to accept gaseous hydrogen at ambient conditions from the electrolyzer.
Aaron Rimpel, a group leader in SwRI’s Rotating Machine Dynamics section, will lead SwRI’s role in the development of their commercial partner’s patent-pending Liquid Air Combined Cycle™ for power and storage. Rimpel’s project, supported by $250,000 in funding, utilizes a cryogenic system that creates and stores liquid air, which can be expanded through a turbine to generate electricity at a later time.
“During periods of low cost electrical energy or excess renewable energy, this system would utilize cryogenic refrigeration equipment to condense atmospheric air into its liquid phase,” Rimpel said. “The liquid air can be stored until periods of higher cost electricity or higher demand electricity.”
During periods of high demand, liquid air would be pumped to higher pressure, heated by extracting thermal energy from a waste heat source, and expanded through a turbine to drive an electrical generator. This discharge cycle will act as a bottoming cycle for a combustion turbine, extracting available heat energy from the hot exhaust gases, and can further be integrated with an organic Rankine cycle to improve overall efficiency.
SwRI provides advanced science and applied technology for energy storage systems ranging from electric vehicle batteries to thermal, mechanical and chemical energy storage.