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  • Sarah Lozanova

Long-Term Energy Storage Will Impact The Future Of Renewable Energy

As the world transitions to renewable energy sources, the issue of intermittency is critical to overcome. If renewable electricity sources, including wind and solar power, can completely phase out the use of coal and natural gas, we will need to have energy around the clock. Sometimes wind and solar farms produce surplus power when demand is low, resulting in waste.

Although lithium-ion batteries in utility-scale battery storage systems are great for short-term energy storage, they are not currently cost-effective for long periods of time, and they can experience issues with thermal runaway. Advancing long-duration energy storage (LDES) technologies is critical to the decarbonization of energy by providing system flexibility and managing fluctuations in energy supply and demand. Let’s explore this topic to gain a greater understanding of how LDES can help decarbonize energy in a reliable and cost-effective manner.

What Is Long Duration Energy Storage?

LDES technologies include mechanical, thermal, electrochemical, and chemical storage systems that can store energy economically for days or even weeks. Ideally, these technologies will use low-cost and readily available raw materials and have high energy densities. However, there is currently no clear leader among long-duration energy storage technologies, but there are several promising options.

The United States Department of Energy defines LDES as energy storage systems capable of providing electricity for durations of 10 hours or more. The Bipartisan Infrastructure Law appropriates $505 million to develop LDES demonstrations “to validate new technologies and enhance the capabilities of customers and communities to integrate grid storage more effectively.”

According to Greentech Media, the five most promising LDES technologies are:

Pumped Storage Hydropower (PSH)

This involves pumping water from a low to a high reservoir. When electricity is needed, water is released and generates electricity at hydroelectric power plants. Once built, these projects are inexpensive to operate. However, few sites are suitable for this application, they disrupt ecosystems, and projects can cost billions of dollars.

The first use of PSH dates back to the 1890s in Switzerland and Italy, and it was first used in the United States in the 1930s. There are currently 43 PSH plants in the United States, and there is the potential to double the pumped storage hydropower capacity.

Stacked Blocks

Like pumped hydro, this technology involves converting electricity into potential energy through the use of heavy blocks. However, it doesn’t have many of the same challenges and can be deployed in a wider range of locations.

The Swiss company Energy Vault creates stacked block energy storage systems that power crane motors to move concrete blocks up a tower. Then, the crane motors can go in reverse when lowering blocks, creating electricity in a process that is about 85% efficient. Energy Vault was recently selected for a 440-mWh storage system in Nevada.

Liquid Air Energy Storage (LAES)

This technology involves storing electricity in the form of liquid air or Nitrogen at temperatures below -150 degrees Celsius. A charging device uses off-peak electricity to power a liquefier which produces liquid air that is held in an insulated tank at low pressure. A power recovery unit re-gasifies liquid air to power a turbine to generate electricity. Unlike pumped hydro, there aren’t geographical constraints, and it uses components used in other commercial applications.

Highview Power specializes in cryogenic energy storage and is based in the United Kingdom and the United States. It has numerous projects in various stages of development that utilize LAES technology, including two existing pilot projects.

Underground Compressed Air

This concept uses excess electricity to pump compressed air into a cavern. Releasing the compressed air powers a generator to produce electricity as needed.

Although this technology has geologic constraints, the Canadian company Hydrostor is trying to overcome this by using purpose-built caves or mine shafts. It has a variety of projects in development or operation in the United States, Canada, Chile, and Australia.

Flow Batteries (Redox Flow Batteries)

This electrochemical cell provides chemical energy from two chemical components dissolved in liquids pumped through the system on separate sides of a membrane held between two electrodes. Most batteries contain two tanks of liquids that circulate in their own respective spaces.

ESS is a publicly traded company based in the United States that produces flow batteries with a liquid electrolyte containing dissolved iron. It has a deal with the Sacramento Municipal Utility District in California to provide 200 MW of its products.

The LDES Council

The LDES Council is a nonprofit, executive-led organization with over 60 members in 19 countries and is dedicated to the acceleration of LDES technologies and applications. It provides guidance on LDES systems to governments, utility providers, and large electricity users, and its members include technology innovators, investors, and energy users.

The LDES Council is dedicated to the wide-scale adoption of long-duration energy storage to accelerate the use of clean energy, displacing the use of fossil fuels and achieving carbon neutrality. It provides member-driven, fact-based guidance and research to help achieve net zero for energy grids by 2040.

Benefits Of LDES

One of the biggest advantages of LDES is how it promotes grid flexibility, enabling greater deployment of wind power and solar energy. Greater use of renewable energy is critical for decarbonizing the power grid and sustainability.

Long-duration storage allows energy to be stored for days or even weeks, making it easier to meet electricity demand with renewable sources by avoiding over-generation. For example, if you consider the duck curve for solar power generation, there are times in some markets when solar panels can produce more energy than is needed by the power grid. This causes utilities to curtail solar production, resulting in waste. However, LDES systems could avoid this waste by storing electricity for times of higher demand.

It also helps promote resiliency and grid reliability by preparing electric grids for unexpected conditions and increasing electricity demand from greater use of electric vehicles. In addition, cheaper and more efficient LDES technologies will help store electricity more economically, keeping electricity prices down. The most promising LDES use low-cost and readily available raw materials that can be relatively easily deployed in a variety of settings.

Long Term Energy Storage Puts Climate Goals Within Reach

About 20% of the electricity produced in the United States in 2021 was from renewable sources, primarily wind, hydropower, and solar, according to the Energy Information Administration. However, to slow climate change, it is critical to phase out the use of fossil fuels as quickly as possible. The advancement of LDES is essential for curtailing greenhouse gas emissions while ensuring a reliable and cost-effective power supply.

Several companies are constructing long-duration energy storage systems, including Energy Vault, Highview Power, Hydrostor, and ESS, and the Bipartisan Infrastructure Law is allocating $505 million for LDES demonstrations. As more LDES projects are constructed, it will be easier to evaluate which technologies are the most promising for large-scale deployment for the power sector.

Want to learn more about solar energy? Check out the GreenLancer blog for articles about utility-scale solar and microgrids.

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