Episode Details

Pumped Storage Hydropower as a Climate Solution

Pumped storage hydropower, also known as water batteries, are often used as a means to store excess renewable energy. For example, solar and wind may generate more energy than is needed during certain times of the day and less than what is needed at other times.  As a result, water batteries are extremely useful as a way to store and release energy during peak demand periods or when renewable sources are unavailable (i.e, when the sun is down). This form of energy storage is used in many places across the country, and across the world, including Tennessee, Kentucky, and San Diego. 

Current and Future Use of Pumped Storage Hydropower

In San Diego County, a proposed pumped storage hydropower project would connect a lake to large underground pipes which will “connect this lake to a new reservoir… 1100 feet higher in elevation” so that “when the sun is high in the sky, California’s abundant solar power will pump water into that upper reservoir.” When the sun is down, the water would be released to the lower lake, generating around ”500 megawatts of electricity for up to eight hours” which is “enough to power 130,000 typical homes.”

At Tennessee’s Raccoon Mountain, TVA stores the excess energy as gravitational potential energy and produces about “1700 megawatts of electricity” when in demand during the day. It takes extremely long for these projects to get approved because the investment is “more than 2 billion dollars for a large plant”.  The project consists of three components: a lower reservoir “bounded by a 62 meter high dam” and “replenished as need to make up for evaporation;” an underground powerhouse which is “a 137-meter-long cavern” housing “three pump turbines;” and an upper reservoir which “would be some 600 meters across and bounded by a 53 meter high dam.”

All currently operating pumped storage hydropower projects in the U.S. are “open-loop” facilities, meaning the lower reservoir is a natural water source such as a lake or river. This is the case with the San Diego and Racoon Mountain projects. In contrast, “closed-loop” pumped storage is built offstream and operates independently of natural waterways. For example, at a proposed pumped storage facility in Kentucky, an old coal mine is being repurposed to be used as a water battery. This land has “hosted mining for at least 70 years” and this “project would deliver up to 287 megawat