Energy Storage that Grows with the Grid

To make renewable energy as reliable as fossil fuels, we need large-scale batteries to store and supply electricity to the grid when the sun isn’t shining or the wind isn’t blowing.

But not all batteries are created equal.

That’s where Fourth Power comes in. Our technology makes renewable energy an on-demand energy source through utility-scale thermal storage. We can harness today’s wasted wind and solar production to respond to grid needs at a cost competitive with fossil fuels.

Our modular battery can provide 5 to 10 hours of storage to meet needs now and scale with renewable deployment for needs up to 100 hours and any increment in between. With the ability to provide short- and long-duration energy storage (LDES), we can start small and grow with the grid to save consumers money and ensure a clean energy future.

Key Features

Low Cost

Fourth Power is among the highest energy density options, enabling us to store electricity at the lowest cost — less than $25/kWh-e — ten times cheaper than lithium-ion batteries. When paired with renewable energy, Fourth Power can serve power that is the same cost or cheaper than the combustion of natural gas.

Inexpensive carbon blocks are used to store energy at record-breaking temperatures.


Our technology is cost-effective even at short durations, so we can offer a modular storage system that grows with the grid – providing short-duration storage now and long-duration energy storage later as the transition to fully decarbonized infrastructure takes place. Doubling the duration of a Fourth Power system is a fraction of the cost of initial installation.

Each subsystem of Fourth Power’s thermal battery is separately housed – this allows energy and power to be scaled independently.

Flexible & Fast

Grid-scale, long-duration batteries must have flexible discharge rates and reaction times to give grid operators complete control over how and when the stored energy is used. Within seconds of notice, Fourth Power’s technology can dispatch affordable, clean energy for a few hours to days.

Fourth Power’s thermophotovoltaic (TPV) power sticks can be moved in and out of the light, which allows the system to respond quickly and flexibly to grid needs.

High power

Our Guinness World Record graphite plumbing system operates at almost half the temperature of the sun and allows us to transfer 10 to 100 times more heat than any other company with the same size equipment.

Fourth Power’s heater operates at an extremely high temperature – almost half the temperature of the sun – which enables the system to have high power density.


Our thermal battery technology was engineered with safety in mind from start to finish. The enclosed system is not pressurized – there is no risk of explosion. The argon gas environment prevents oxidation, adding a critical layer of protection. And as a chemically inert system, there are no concerns of thermal runaway.

An outer enclosure houses the subsystems of the battery and keeps the system contained in an argon environment, rendering the system safe from fire risk and chemical degradation.

Long life

Our thermal storage long-duration batteries experience no corrosion, and are engineered to have a 30+ year life.

Fourth Power’s liquid metal pumps — along with the rest of the system — have been designed for 30+ years of life with no corrosion.



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