The New Iron Age: The Potential of Affordable, Safe, and Clean Energy Storage – EQ Mag
The United States is accelerating into the sustainable energy transition, aided by the landmark Inflation Reduction Act (P.L. 117-169) (IRA) and the Infrastructure Investment and Jobs Act (P.L. 117-58) (IIJA), which provide billions of dollars in funding for renewable and clean energy development, as well as tax credits and incentives that prioritize environmental and equity-focused projects. The United States is positioned to massively expand its renewable energy industry. But in order to build out U.S. renewable infrastructure to its fullest potential, we will need to better address energy storage. Iron-air and iron-flow batteries are promising solutions with the potential to help renewable energy truly scale up.
One challenge facing the energy transition is that several key forms of renewable energy rely on intermittent natural conditions, such as sunlight or wind, to generate energy. These sources are often referred to as variable renewable energy, or VRE. Although renewable energy sources are plentiful, until recently, there were few promising ways to store excess energy produced by wind or solar for later use. Now, batteries based on abundant and safe iron can offer reliable storage to meet growing energy needs.
An Energy Storage Solution: Iron-Air and Iron-Flow
Utilities are working with companies like Tesla to install lithium-ion batteries to provide storage for the grid; however, these batteries provide only short bursts of charge, generally storing enough electricity to discharge for about four hours. The electric grid, which needs reliable access to electricity 24/7 regardless of active production, needs greater storage capacity if it is to be powered by intermittent renewables.
Iron-flow batteries are one possible solution. They operate by moving two electrolyte solutions across a carbon membrane, which generates electricity. The iron-flow batteries currently on the market, like those developed by ESS, can provide between six and twelve hours of storage and so occupy the niche of inter-day storage. This timeframe is ideal for addressing a renewable energy issue known as the “duck curve,” which refers to the mismatch between solar energy production and peak energy demand. Solar production is highest when the sun is shining and demand is relatively low (during temperate days). In the evenings, demand skyrockets but solar production stops. This creates a challenge for the renewable energy industry, one that ESS believes iron-flow batteries can solve.
While iron-flow batteries could play an important role by providing a safer and more affordable mode of inter-day storage, a truly resilient electric grid needs to be able to store days of energy. Multi-day storage would ensure that power can be maintained through periods of low energy production, for example during severe weather or following a disaster.
Iron-air batteries, like those produced by Boston-based battery company Form Energy, can store 100 hours of energy, providing coverage for a days-long gap in renewable energy production. Iron-air batteries use a process called “reversible rusting” to store electricity, converting iron into rust and rust back into iron in a cycle that can store an electrical current. The batteries first absorb air, causing the iron they contain to rust. The chemical reaction that creates rust also generates electricity, which can be dispatched as needed. Reversing the current (i.e., recharging the batteries) turns the rust back into iron, readying the system for another round.
Lithium-ion batteries overtook iron-air as the default battery technology because they can be made much smaller. Lithium-ion batteries power most phones, laptops, electric vehicles, and more. They can pack a big punch in a small package, making them an attractive part of the ongoing charge towards electrification. Nevertheless, iron-air batteries may be poised to fill a key electrification need by providing reliable, safe, multi-day storage that can easily plug into existing grid infrastructure. That is because iron has several advantages compared to lithium.
The Iron Advantage
In addition to being able to store less energy than iron-based alternatives, lithium-ion batteries have other requirements that make them less-than-ideal for grid storage applications. Above all, lithium-ion batteries need lithium, which does not come cheap. Lithium is comparatively rare and is in high and growing demand, as the production of electric vehicles increases dramatically. Lithium demand is set to skyrocket even further with the Biden-Harris Administration’s goal of making 50 percent of new vehicle sales electric by 2030. Using iron-air batteries in place of lithium-based batteries in grid storage could help take some of the stress off the supply chain since iron-based batteries do not require lithium.
Another attractive aspect to iron-based batteries is that their iron could potentially be sourced and processed in the United States. Working to strengthen domestic supply chains is a priority of the Biden-Harris Administration, as evidenced in the IRA guidelines that increase tax benefits for manufacturers meeting domestic sourcing criteria. In an interview with EESI, ESS Director of Corporate Communications Morgan Pitts noted that over 80 percent of the company’s materials by volume are domestically sourced, and 100 percent of its production is domestic. Form Energy is set to install its first commercial-scale project in Minnesota, which has an abundant supply of iron. According to Form CEO Mateo Jaramillo, the state’s iron deposits were an exciting benefit to their site choice. Jaramillo writes that Form Energy is “very actively investigating what it would be like to use [Minnesota iron] as a resource.” Iron-air and iron-flow batteries offer the opportunity to prioritize U.S. sourcing, production, and labor in the transition to renewable energy.
Unlike iron-flow batteries, lithium-ion batteries require precise temperature regulation to function, losing significant efficiency after temperatures rise above 77 degrees Fahrenheit. For states with hot summers, this necessitates the installation of expensive cooling equipment in battery storage facilities. On top of adding to the economic cost, air conditioning contributes to energy consumption and can increase pollution from carbon-emitting energy sources. According to ESS, iron-flow batteries function efficiently in a much wider temperature range of 23 to 104 degrees Fahrenheit, making them ideal for installation in outdoor environments while also avoiding the financial and environmental costs of temperature regulation. This advantage will become even more important as climate change triggers rising temperatures across the United States.
Another benefit of iron-based batteries is their safety. The electrolyte solution in iron-flow batteries, for example, has a pH comparable to wine, and the batteries pose no risk of combustion. Furthermore, the materials used are highly recyclable. The nature of iron-based batteries means that they have a much longer lifespan than lithium-ion batteries, which degrade quickly after four to seven years of use. ESS batteries have a lifespan of 25 years and, in theory, the iron and electrolyte solutions could be reused indefinitely. By contrast, lithium-ion batteries require specialized disposal to avoid potential combustion, creating an additional cost to energy suppliers and potentially polluting nearby environments.
The Future of Iron Batteries
While iron-based batteries offer promising potential, they are still a developing technology, and therefore require support for research and effective implementation. Federal funding has already helped iron battery development, with the Advanced Research Projects Agency-Energy (ARPA-E) having funded ESS research into using iron slurry for a longer-duration battery. In an email with EESI, Morgan Pitts said that the collaboration between ESS and ARPA-E “played a key role” in allowing the company to refine iron-flow technology and prepare for market-scale deployment. Continued federal support can help the United States harness this technological advancement in the development of renewable energy.
The IRA and IIJA provide billions in funding to implement energy storage, with the IIJA designating $505 million specifically for energy storage, and the IRA creating an Energy Investment Tax Credit of 30 percent for energy storage. Directing this funding to prioritize safe, affordable, and domestically-sourced energy storage technology could boost the production and deployment of iron batteries, leading to potential benefits for U.S. markets, manufacturing, and most importantly, the climate.