Martin Wohl

In August, Form Energy received a $149,000 grant from the Department of Energy to build an 85-megawatt demonstration project in Lincoln, Maine to show how an iron-air battery installation could provide grid-level support by meeting power storage demands. Form Energy, founded by former Tesla employees who built their battery business, will manufacture the batteries at their Weirton, West Virginia plant, already in its production trial phase.

Lincoln’s Technology Park, off I-95 between Bangor and Mount Katahdin, an abandoned former pulp and paper mill site, was selected because it is near Versant Power’s Lincoln substation, where connection to the grid is practicable.

Rendering of a 56-megawatt (MW) iron-air battery installation. (Courtesy image: Form Energy)

How does this work?

The battery’s cell consists of iron in the form of microscopic granules – constituting the anode (negative), and air – containing oxygen, as the cathode (positive), within a saline electrolyte. Oxygen’s promiscuous two outer-shell electrons are eager to hook up with any reactive element partner to create an oxide, in this case, iron oxide, aka rust, and in the process, release energy in the form of electricity.

Magic happens when the process is reversed: applying electricity to rust (in the proper conditions in the electrolyte) separates the oxygen and iron, thus recharging the battery. The water-based electrolyte acts as a catalyst allowing the transfer of electrons to accomplish the rusting process. As any mariner knows, saltwater makes the process occur faster, as the water’s chloride ions interact directly with the iron.

Readers are invited to explore the chemistry in more detail at www.ResearchGate.net.

Why do this?

Iron-air battery technology is pursuing the holy grail of economically viable, grid-level energy storage to make wind and solar-generated electricity available whether or not the wind is blowing, and the sun is shining. Most other battery types are too expensive and short-lived, and alternative technologies, like pumped water storage for hydroelectric production are expensive and too cumbersome for widespread adoption.

Additionally, grid-level storage can also help non-renewable-sourced power by smoothing out voltage fluctuations and avoiding or delaying the start-up of “peaker” plants during periods of high demand.

What about other power storage options?

Iron-air batteries are not as efficient as other battery types (they return 60% of the energy used to charge them, versus about 90% for lithium-ion¹) take longer to charge, and are bigger and heavier than other types, but they have a long list of benefits for stationary storage:

• A long discharge capability, up to 100 hours, more than ten times as long as current lithium-ion batteries.
• A long cycle life, withstanding up to 10,000 charge/discharge cycles, vs. 300 to 500 for lithium ion versions, partially attributable to lower dendrite formation in iron-air batteries.
• They are pretty much non-hazardous, although the alkaline electrolyte can have a pretty high pH level, typically 13.7 (for reference, laundry bleach is at 12) and it is water-based so there is no danger of fire. While some lithium-ion batteries, such as more costly lithium iron phosphate types are non-flammable, most have flammable electrolytes
• Relatively cheap and environmentally friendly: iron and air are the main ingredients.

Because renewable sources over-produce at some times and fail to produce at others, battery efficiency is not a major concern. There’s plenty of it, and will soon be more: in 2024, California alone will generate 2.6 million megawatts of solar power in excess of requirements. Currently this power is wasted or sold to other states; that energy could be used to charge storage batteries.

As Green Energy Times reported earlier, another technology aimed at grid-level storage is the flow battery, where electrolytes, positively and negatively charged, are pumped past a membrane to generate electricity. These can be termed a type of fuel cell, because the energy is stored in the electrolyte, not the electrode, as with other types of batteries. Flow batteries require mechanical operation of pumps and face challenges including the type of element used in the electrolyte: vanadium is optimal from a performance standpoint but is a rare element difficult to refine and mined mainly in China, Russia, and South Africa. Additionally, vanadium flow battery electrolytes can be highly acidic.

What does the future look like?

Achieving grid-level energy storage is a technology horse race complicated by grid management rules and practices, principally the 4-hour capacity rule and other similar regulations – arcane constructs that limit compensation to grid-level battery providers to the first four or so hours of battery-supplied power. These regulations were adopted by many utilities when the goal was to supply power during peak usage hours only, typically 4 to 9 pm.

Supplying extra power to a grid that gets most of its electricity from renewable sources will require much longer support from storage. For example, at least 15 hours and 12 minutes per day in Maine at winter solstice, for a solar-powered source. The Department of Energy’s National Renewable Energy Lab estimated that 6 terawatt hours of storage would be needed to support a nation-wide renewable grid. At an estimated $20/kWh, this could cost $120 billion in total. When comparing the lifetime costs of power plant technologies, the cost of down-time storage should be considered for renewable installations that provide power intermittently. Levelized cost of electricity studies have shown that renewable power is generally below or at parity with fossil fuel and nuclear alternatives – the development of cheaper storage solutions and the imposition of carbon clean-up requirements on fossil fuel alternatives would tip the scales further.

Unfortunately, Form Energy did not respond to requests for comment or input on this article, so we were unable to obtain further information about the Lincoln project or their future plans.