What are the long-term energy storage systems with the lowest cost when the continuous discharge time is different?

　　Researchers from the National Renewable Energy Laboratory in the United States recently released a research report on which energy technology can provide the lowest cost when wind power and solar power facilities are unavailable to provide electricity to the western United States interconnected grid Conducted research and investigation.

　　Researchers at the National Renewable Energy Laboratory (NREL) found that, given current and future investment cost scenarios, underground hydrogen storage technology and natural gas combined cycle (NGCC) power plants have carbon capture and storage (CCS) technology for 120 hours in energy storage applications with continuous discharge time, it can provide the lowest levelized cost of energy (LCOE). Pumped storage power generation facilities, compressed air energy storage systems, and battery energy storage systems are the energy storage solutions with the lowest LCOE for a continuous discharge time of 12 hours.

　　In terms of technology and economy, the report analyzes the long-term energy storage systems and flexible power generation technologies used in the Western United States interconnected power grid. The Western Interconnected Grid is a wide-area synchronous grid that extends from Western Canada to California. Renewable energy generation accounts for 85% of the region's power structure.

　　Researcher Chad Hunter said: "Long-term energy storage systems require greater energy storage capacity and continue to work for several days, weeks or even longer at typical charging or discharging rates."

　　The long-term energy storage system can provide rated power within a continuous discharge time of 12 hours to 7 days. Among them, the LCOE is calculated for current and future investment costs.

　　According to analysis, NGCC power plants are the lowest-cost solution for the longest continuous discharge scenario of 7 days. For the 12-hour continuous discharge time, the lowest threshold and the lowest cost options are compressed air energy storage (CAES) systems, lithium-ion battery energy storage systems, vanadium redox flow battery systems, and pumped storage power generation facilities.

　　Hunter explained: "Battery energy storage systems may play an important role in future grid-scale energy storage systems. Of course, this must take into account whether battery costs can drop as quickly as they have in the past decade."

　　For long-term energy storage systems with a continuous discharge time of more than four days, the lowest cost energy storage solutions are adiabatic compressed air energy storage (D-CAES), NGCC power plants, natural gas combustion turbines (NG-CT), Salt cave hydrogen storage facilities, and proton exchange membrane (HDV-PEM) fuel cells used in heavy-duty vehicles. They also determined that pumped storage facilities and HDV-PEM fuel cells provide the lowest LCOE in applications with continuous discharge times of 12 hours and 120 hours, respectively.

　　The research team said that when the continuous discharge time exceeds about 48 hours, the energy storage investment can be minimized, and the LCOE is more sensitive to the cost of the energy storage system.