by David Von Seggern, Sierra Club Maine Volunteer
Recently, there was a burst of media coverage on a proposed battery storage project near Lincoln, ME. The project is in the very earliest stages of planning, but what catches our attention is that it intends to use iron-air battery technology. This technology, long in development, seems poised for commercial deployment; and in this case it is being brought forth by Form Energy. The facility is planned to be able to supply to the grid 8,500 MWh of energy delivered at a rate of up to 85 MW. As a reference, the electrical load in Maine in 2022 was 34,970 MWh/day; thus the facility, in principle, could keep Maine going for about one-quarter of a day or supply about one-fourth of the electrical load over four days.
Already, a battery storage facility is under construction near Gorham, ME, using proven lithium-battery technology. That facility, developed by Plus Power, will be able to provide to the grid 350 MWh of electrical energy delivered at a rate of up to 175 MW. Comparing their energy capacity, we see that the Lincoln facility, if fully built out, would supply nearly 25 times as much energy to the grid.
The iron-air battery works on the same chemical principle as all batteries: oxidation-reduction. Oxidation, involving the loss of electrons, occurs at the negative electrode, the anode. Reduction, involving the gain of electrons, occurs at the positive electrode, the cathode. When the battery is connected to a circuit, electrons generated at the anode travel through the circuit to the cathode, supplying electrical energy. When the anode runs out of electrons, hence runs out of energy, some batteries can be recharged (“rechargeable” batteries) by running the current in the opposite direction, sending electrons from the cathode to the anode.
Oxidation processes are exothermic, thus supplying energy to a circuit, which may be the electrical power grid. In reverse, the charging cycle is endothermic, taking energy from the grid and storing it via the conversion of oxidized iron back to pure iron and releasing oxygen. The iron-air battery charge-discharge processes are somewhat complex, and that is why it has taken so long to bring iron-air batteries to market as large-scale energy storage devices that will reliably go through thousands of cycles and perform each cycle with high efficiency (low waste heat energy).
We are excited that the iron-air-battery technology may be demonstrated on a large scale in Maine, making Maine a leader in the use of this new and relatively benign technology. Using iron instead of lithium as the working substance in a battery would involve mining an element that is abundant and has high concentration in ores compared to the much less abundant lithium that occurs at low concentration.
Moreover, other rare metals such as magnesium and cobalt are not required. Thus we should have far less environmental impact in manufacturing iron-air batteries as opposed to lithium-ion batteries.
We are also excited that battery storage facilities will come online in Maine and eventually replace the use of natural gas peaker plants when the electrical demand peaks. A report commissioned by the Clean Energy States Alliance shows that Maine would benefit cost-wise from such replacement while avoiding the greenhouse gas emissions of natural gas plants. Adding battery storage to the grid is essential to achieving the long-term goal of a fully green electrical supply in Maine while keeping electrical rates reasonable.
Consider that a battery storage facility is a generator of electricity when it is needed, supplying electricity to the grid just as wind or solar farms. The fact that electricity had to be input to the battery facility makes it a different type of generator, but the discharge cycle provides the same commodity as true generators. Those not familiar with battery storage may be surprised at the small footprint that these facilities have, compared to wind and solar farms. For example, the Gorham battery storage facility will take about five acres of land space. The nameplate capacity of the facility is 175 MW, giving about 35 MW per acre. Solar farms vary in their footprint, but a rule of thumb is that their nameplate capacity is 5 -10 MW per acre. This is a difference of a factor of 3.5 to 7 in land utilization to input electricity to the grid at equal rates. It is no wonder that solar farms are being increasingly paired with battery storage facilities which take up little additional space.