PERFORMANCE OF IRON-AIR ENERGY STORAGE FACILITY

PERFORMANCE OF IRON-AIR ENERGY STORAGE FACILITY

https://www.windtaskforce.org/profiles/blogs/performance-of-iron-ai...

By Willem Post 

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Form Energy’s iron-air battery storage facility would be located at the former “Lincoln Paper and Tissue” mill site in Lincoln, Maine. The facility requires about 50 acres

This major project, situated within the developing Lincoln Technology Park, represents another method for long-duration energy storage (LDES).

Key Project Details

Capacity: The multi-day energy storage system has a capacity go 85 MW/8500 MWh

Duration: The system will continuously discharge electricity for 100 hours (over 4 days).

Funding: The development received a $150 million federal grant in 2024 through a grid resilience program.

Timeline: Construction would begin in 2028, pending local approvals.

How the “Rust” Technology Works

The iron-air battery functions via a process called reversible rusting:

Discharging: The system “breathes-in” oxygen from the air, converting the internal iron pellets into rust, which generates and releases electricity.

Charging: An incoming electrical current reverses the chemistry, transforming the rust back into pure iron while “exhaling” oxygen.

Advantage: It bypasses expensive or hard-to-source components like lithium, nickel, and cobalt, utilizing iron, water, and air.

On a high-voltage (HV) grid-to-grid basis, Form Energy’s iron-air battery system operates at a round-trip efficiency (RTE) of about 40%

This means in Year 1, for every 10 MWh taken from the HV grid to charge the system, about 4 MWh are returned to the HV grid during discharge.

Steady Charge Rate: Given that a complete 0% to 100% charge takes roughly 100 hours, about 4 days, the system gains capacity at an average rate of 1% per hour.

Accounting for its round-trip efficiency of about 40% the system will take 8500/0.4 = 21,250 MWh from the HV grid over a 100-h period and delivery 8500 MWh to the HV grid over a 100-h period.

This represents an enormous $ loss, because a lot more MWh is taken from the grid than is delivered.

Form Energy’s iron-air battery storage facilities claimed to have a useful service life of 20 to 30 years, losing less than 2% of their capacity annually.

Assume Year 1 roundtrip loss factor 0.65 x 0.65 = 0.4225

That means about 20,118 MWh must be taken from the HV grid to deliver 8500 MWh

Assume Year 20 roundtrip loss factor 0.4225 x (1- 0.02) ^19 = 0.2878

That means about 20,118 MWh must be taken from the HV grid to deliver (0.2878/0.4225) x 8500 = 5790 MWh,

Assume Year 30 roundtrip loss factor 0.4225 x (1-0.02) ^29 = 0.235

That means about 20,118 MWh must be taken from the HV grid to deliver (0.235/0.4225) x 8500 = 4728 MWh

Loss factor is from HV grid to 1) step-down transformer, 2) front-end power electronics to convert AC to DC, 3) into storage, 4) out of storage, 5) back-end power electronics to convert DC to AC, 6) step-up transformer, to HV grid.

New England Dunkelflaute

New England often has near-zero wind/solar periods that last 5 to 7 days throughout the year, so called Dunkelflaute

Sometimes one Dunkelflaute is followed by another, shorter Dunkelflauta within days, i.e., well before the system had recharged.

In such events, 2 systems will be required to cover just a tiny fraction of the total consumption in New England

CONCLUSION: Based on my 40-y of experience in the design and analysis of energy systems, I judge this system to be a huge boondoggle. Some orders have been received, but no operating systems exist. For impoverished Maine to pursue this expensive project is worse than 1) electric school buses in winter, and 2) 850-ft tall, floating offshore windmills.

Here is a far superior solution that lasts at least 40 years, with minimal reduction of output over the years, requires only ONE ACRE, and can be installed in less than one year.

A 100 MW Combined Cycle Gas Turbine (CCGT) power plant is a highly efficient mid-size generation facility that uses both gas and steam turbines to convert natural gas into electricity. By capturing waste heat, these plants achieve thermal efficiencies of 50% to 60% (and up to 90% in cogeneration mode), making them much cleaner and more cost-effective than standard simple-cycle plants.

Technical Configuration

To hit a 100 MW target capacity, plants typically use

Single-Shaft 1-on-1 configuration: One ~65 MW gas turbine paired with one ~35 MW steam turbine on a single generator shaft.

How the Plant Works

1. The Topping Cycle (Gas Turbine): Natural gas burns in a combustion chamber. The expanding hot air spins the gas turbine blades to generate the first ~60–65% of the power.

2. Heat Recovery: Instead of exhausting the hot gas (often over 500°C) into the atmosphere, it passes through a Heat Recovery Steam Generator (HRSG).

3. The Bottoming Cycle (Steam Turbine): The HRSG boils water into high-pressure steam. This steam spins a secondary steam turbine to generate the remaining ~35–40% of the plant’s electricity without burning any extra fuel.

Financial and Cost Metrics (2026 Benchmarks)

• Capital Cost (EPC): Ranges between $900 and $1,400 per kW, placing the total build cost for a 100 MW facility at roughly $90 million to $140 million depending on location and logistics.

• Fuel Consumption: A 100 MW plant, at 55% efficiency, at rated output, for 24 hours, consumes about 24 x (100 x 1000) x 3412/0.55 = 14889 million Btu/day of natural gas.

• Operational Advantages: These plants provide excellent grid flexibility. They feature fast startup times to balance out intermittent renewable energy sources like wind and solar.