Long Duration Energy Storage (LDES) is finally getting the global attention it deserves, both as the grid stability solution for variable power and as an essential part of the reliable, resilient grid needed for future economic growth. Yet, despite massive innovation in the industry, much of the current discussion about LDES—its potential and its limitations—has revolved around a handful of established technologies like pumped hydro. But we’re entering the “golden age” of LDES. New innovations are being tested and breakthroughs are even being made with older technologies, making them more efficient, cost-effective, and commercially viable to be used with today’s grid.
That’s where Hydrostor’s advanced compressed air energy storage (A-CAES) comes in, as a modern take on the traditional compressed air energy storage (CAES) technology that has been around for decades. With a few critical changes, Hydrostor has built on the proven principles at the heart of CAES, while addressing the difficult economics and siting constraints of traditional compressed air systems.
Currently two traditional large-scale CAES facilities exist in Germany and Alabama. Both remain in operation today, a testament to the long asset life and reliability of compressed air energy storage. But there’s a reason traditional CAES technology hasn’t been built around the world. When these existing CAES facilities charge the system by pumping compressed air into underground caverns, the heat that is created during the compression process is vented to the surrounding atmosphere rather than being captured and stored. Natural gas combustion is then used to reheat the compressed air as it is released and expanded during the discharge process. In addition to creating greenhouse gas (GHG) emissions, variable costs associated with the fuels makes running these plants expensive, and less economical than a typical natural gas plant.
Hydrostor’s innovation, a proprietary thermal storage system, eliminates the need for a fuel source by capturing heat from the charging process for later use during discharge. In addition to eliminating the need for natural gas, Hydrostor’s thermal storage innovation improves system efficiency, and reduces overall operating costs.
CAPTION: By capturing the heat used in the air compression process, Hydrostor has eliminated the need for fuel to re-heat the air during the discharge process, making A-CAES emissions-free and less costly than traditional CAES
Both CAES and Hydrostor’s A-CAES use underground caverns to store compressed air. For CAES, that required finding salt formations, building salt caverns there, and siting storage facilities in those locations. Salt formations are relatively rare, though, and aren’t commonly located where the grid demands large-scale energy storage. Conversely, by using hydrostatic pressure to reduce the required cavern volume, Hydrostor’s A-CAES caverns can be created in most stable, hard-rock geological settings, greatly increasing the number of locations around the world where projects can be delivered. While both A-CAES and pumped hydro use water as part of their energy storage solution, A-CAES is much more space and resource-efficient. For example, a pumped hydro system with a standard operating head of 150 meters would require 20 times more water than A-CAES, while a very high-head pumped hydro system with a 600 meter head would still require 5 times more water.
CAPTION: Hydrostor’s use of hard-rock caverns, rather than salt caverns, makes its A-CAES systems easier to site near the areas where energy storage is needed
While Hydrostor’s A-CAES wouldn’t exist without the foundation of traditional CAES technology, its unique innovations eliminate its predecessor’s constraints. The efficiency, siting flexibility, and zero-emissions profile advantages that A-CAES brings to the table ensure it can serve more grid applications and bring better value to customers than traditional CAES.