Long-Duration Energy Storage Connects the Wind and Solar Dots in Texas

A new resource for businesses seeking clean energy is emerging in the form of long-duration energy storage systems. Long-duration systems can produce electricity from wind and solar resources on a steady basis, regardless of the weather or time of day. They can also offer additional benefits including safety, ease of management and avoidance of toxic substances.

The need for long-duration energy storage

Lithium-ion battery arrays are currently the main form of energy storage systems for renewable resources. Utilities and other users routinely deploy them to fill in recurring gaps in wind and solar availability. Energy storage also enables renewable energy buyers to take advantage of low prices when excess wind and solar power are on the grid and avoid costly peak rates during high-demand periods.

Lithium-ion energy storage will likely continue to be relevant for the foreseeable future. However, as wind and solar resources take up an increasing amount of space in the nation’s electricity supply, the need for new long-duration storage systems has come into sharper focus.

“Lithium-ion is great for short duration, but there are supply chain and safety issues. If you want storage for 10 hours, or days, or weeks, you need long-duration energy storage,” explains Julia Souder, CEO of the multinational organization Long Duration Energy Storage Council.

One main issue is the relatively short length of duration for lithium-ion battery arrays. Four hours of duration is common, and a timespan of up to eight hours is emerging. Still, for planning, reliability and resiliency purposes, the U.S. Department of Energy advocates for long-duration periods of more than 10 hours, ranging up to days, weeks, months and even whole seasons.

Fire prevention is also a concern for lithium-ion technology due to the flammable electrolyte used in lithium-ion batteries. In addition, the lithium supply chain has raised issues, partly due to the use of open-pit mining and the evaporation of brine in large lagoons. More sustainable lithium recovery technologies are in development, but in the meantime, new lithium mines in the U.S. have already become the focus of criticism over environmental and cultural impacts.

Texas is primed for long-duration energy storage

Texas has been an epicenter of U.S. oil and gas production for generations, so it may seem an unlikely place to spot new innovations in long-duration energy storage. Nevertheless, the state’s vast wind and solar resources have made it an ideal place to establish new long-duration energy storage systems.

In addition to leading on wind and solar power, Texas is already among the top states for energy storage capacity, including several projects that demonstrate new and emerging long-duration energy storage technologies.

The unique character of the Texas grid also encourages innovation. Other states in the contiguous U.S. can share power generation resources through a network of interconnection regions. The regional system was established in the 1990s to help ensure reliability and resiliency on a national basis.

In contrast, almost the entire state of Texas is walled off into its own, isolated grid. The falling costs of wind and solar power have motivated the state’s grid manager — the Electric Reliability Council of Texas (ERCOT) — to focus attention on renewable energy resources within the state, leading to an emphasis on energy storage, as well. 

Innovations in long-duration energy storage

There is a “huge push” for new duration-extending battery formulas based on alternative chemistries including zinc, iron and vanadium, Souder said. Many of these new electrochemical solutions are containerized, and multiple containers can be stacked at the same site to provide for different types of energy storage.

Green hydrogen and thermal energy storage systems also fall into the long-duration category, Souder explained. Both are beginning to emerge in Texas, with examples including the ambitious Hydrogen City green hydrogen project in Duval County and research into new thermal storage materials at Texas A&M University.

“Everyone is asking about fossil fuels and how to replace gas plants. This is what our thermal energy storage companies are doing,” Souder said. “They are working with utilities and making heat from wind or solar power.”

Leveraging the natural gravity of the Earth

Another type of solution is illustrated by the energy storage startup Renewell Energy, headquartered in Texas and California. The company describes its Gravity Well system as flexible and able to generate electricity for “weeks to months scenarios” as well as shorter durations of two to eight hours.

Gravity systems deploy excess renewable energy to raise blocks or other weights. When the weights are released, their gradual downward motion drives a mechanical system that generates electricity.

The concept is similar to pumped hydropower storage systems, which today account for the vast majority of long-duration energy storage capacity in the U.S. However, pumped hydropower requires specific geological features, ample water resources and significant infrastructure. Block-type gravity systems can be applied on a much greater range of sites, with a relatively small infrastructure footprint.

Renewell partnered with the U.S. Department of Energy in a five-year project to deploy Gravity Well systems within disused oil and gas wells in the U.S. for energy storage, while also plugging them and monitoring for any signs of leakage.

The Swiss firm Energy Vault is also bringing its above-ground gravity storage system to Texas, in a partnership with Enel Green Power.

Compressed air energy storage is another new long-duration technology emerging in Texas. One system under construction in West Texas is deploying natural salt caverns for storage and renewable energy for the compression system. Though the system requires natural gas to heat the compressed air, it is described as a more efficient alternative to conventional gas-fired power plants. Green hydrogen could also potentially fill that role, eliminating the need for fossil fuel.

One last dot to connect

Now that the technology pieces are falling into place, the Long Duration Energy Storage Council is focusing on energy market policies that create a healthy economic environment for long-duration systems. Financial support from the U.S. Department of Energy and a 30 percent tax credit for standalone energy storage systems in the 2022 Inflation Reduction Act have made a difference, but more can be done in order to accelerate investment.

“What we need to see is storage treated as a transmission asset, not just a generation asset,” Souder said. “It can maximize renewables and defer building new transmission lines.”

Texas Gov. Greg Abbott and other leading officials continue to lobby against renewable energy, but cracks are appearing in their opposition. In December, for example, Abbott issued an official statement of support for a massive green hydrogen project in Wilbarger County.

Extreme heat related to climate change is also turning attention to the benefits of energy storage. The state’s wind and solar assets are already credited with helping the Texas grid cope with high demand during a series of heat waves this summer. Now, energy storage is also playing a role. 

Last week, Climatewire reporter Benjamin Storrow observed on Scientific American that a “battery boom is helping to stabilize the Texas power grid, offering a template for utilities that want to cut their greenhouse gases even as air conditioners hum wildly during heat waves." The article focused on short-duration battery systems, which were called into action between the hours of 3:00 p.m. and 8:00 p.m. one evening when air conditioning use soared. In addition to supporting grid stability during that period, the extra capacity helped to reduce demand-related price spikes.

With new long-duration energy storage systems in hand, Texas businesses can look forward to a more stable and resilient grid, improved predictability in their electricity costs, and more opportunities to free themselves from the burden of fossil fuels.

Image credit: Abby Anaday/Unsplash