| Energy storage
from the lower cavern into the upper cavern to store energy. To recover the energy, the brine flows through a hydroelectric turbine – just as in regular pumped storage to generate electricity back to the grid. The compressed air freely flows between the caverns as brine is moved out of one and into the other. There is a practical limit on how big you can make the caverns, so a single upper cavern and lower cavern form a 5MW pair with 20 hours of storage. But the caverns can be built adjacent to each other in a “LEGO” type approach that allows for repetitive construction. Studies have shown that simple designs with repetitive construction produce cost savings and schedule reliability as opposed to single bespoke designs. Five cavern pairs can be tied together on the surface with standard sized piping to form a unit with a single 25MW pump/turbine. Multiple units can then be combined to form larger commercial installations. A 125MW facility with 2500MWh of storage would occupy about 90 acres of salt dome. Multiple salt dome locations have been identified that are large enough to support commercial sized locations with transmission lines nearby. Cavern Energy Storage is completing the preliminary engineering and will soon begin to look for partners and investors to build a 1MW demonstration unit using existing salt dome caverns. From there, the plan will be to build a 5MW demonstration using salt dome caverns optimised for energy storage. The 5MW unit would be the first phase of a larger commercial unit.
Looking ahead The market for energy storage in the US is still evolving
as increased renewables are added to the grid. Across the grid in Texas, which is operated by the Electric Reliability Council of Texas (ERCOT), high levels of renewables have created volatility that can provide an income in excess of what underground pumped storage would require. ERCOT is seeing short duration (1 to 4-hour) price spikes that are being met with batteries and peakier power plants. Lithium-ion battery installations in ERCOT have already topped 7GW and will likely be 9GW by next summer. But these battery systems have short lives, less than 20 years, and depend on lithium and a number of other metals that have challenging supply chains. Plus, the batteries need additional income from the ancillary market
Left: Underground pumped storage hydroelectric
which is becoming saturated. Long duration energy storage is clearly needed in all the long-term forecasts but is challenged in competing in the short term with batteries and peakier natural gas power plants. Whereas China has taken a long-term view and decided to commit to building pumped storage in quantity, the US continues to let short term markets dictate and is not directly investing in LDES construction. Regulators and legislators need to be convinced of the necessity of LDES for future grid operations. In conjunction with industry, they need to set up market mechanisms to provide the encouragement to build LDES. Discussions about LDES being treated like transmission lines as opposed to having to depend on arbitrage are a good start. But whatever the decisions, the market mechanisms need to be put into place so the US can start building long duration energy storage before it becomes a critical necessity. And when those market mechanisms are in place, Cavern Energy Storage will be ready to build this economical choice for the Gulf Coast by leveraging the salt domes that the region has been blessed with.
Author info
William M Taggart is the Founder and CEO of Cavern Storage Energy.
Email:
william@cavernenergy.com
www.cavernenergy.com
Left: 125MW commercial facility
www.waterpowermagazine.com | September 2024 | 37
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53
