The U.S. Department of Energy (DOE) estimates that the U.S. will need 700 to 900 GW of additional capacity to reach net-zero emissions by 2050. As well as natural gas and nuclear, a lot of that will come from renewables. Without energy storage, though, a significant portion of wind and solar energy will be wasted.
According to the U.S. Energy Information Administration (EIA), utility-scale generation of solar electricity averaged 63.1 Gigawatt hours (GWh) between 10:00 a.m. and 6:00 p.m. each day in the lower 48 states in August of 2024. That’s 36% more than for the same hours in August of 2023. Unsurprisingly, California, Texas and Florida make up the bulk of new installations. However, these states often generate more solar energy than the grid can accept. Some solar operators are being told to curtail production, and not by a paltry amount. During 2024, California curtailed over 3 million MWh of solar energy. And the situation appears to be worsening. The quantity of solar power lost in 2024 is double what it was in 2021. There is so much excess power, at times, that it is even being shut off during the hottest parts of the day when demand is high.
No wonder there is so much attention on the funding of lithium-ion battery energy storage systems (BESS). The DOE announced over $3 billion in BESS grants in 2024 for 25 selected projects across 14 states. BESS provides up to four hours of energy storage. That’s a good start. But longer-term forms of storage are urgently needed to increase the efficiency of a renewable-heavy grid. Here are some of the main options for long duration energy storage (LDES).
Mechanical energy storage
Mechanical energy storage solutions are among the most mature of the LDES options. This category includes two primary forms of mechanical technologies: compressed air energy storage (CAES) and pumped hydro systems. In addition, there are a collection of other alternatives, many of which are a variant of CAES. These include liquid air energy storage (LAES), thermal storage, CO2 cycle and gravity-based systems. The basic idea is to convert electrical energy into potential or kinetic energy that is later converted back to electricity.
March 5, 2025
February 11, 2025