Peak Power Plug-In

What problem does Fourth Power seek to solve?

Simply put, this is an issue of peak power. When you think about the changes that are happening in the electricity system, electricity load has largely been flat for the last 30 to 40 years. That is about to spike, and that creates a need to manage very high peaks of energy [demand]. Not only do we have load growth, but the traditional way that we have dealt with those peaks is through what are called peaking plants. These are highly inefficient, highly expensive, highly polluting plants that deal with the peak hours of a day, week, or month. The majority of these were built either around 2000 or in the late ’70s, with some exceptions. The maintenance costs are very expensive.

What Fourth Power is out to solve is the problem of addressing the peak. We are one of the only technologies that can be a plug-in-place replacement for peaking power plants, because we have energy density that creates a very small parcel of land requirement to provide peak power during the times that the grid needs it the most. And a lot of these needs occur near urban corridors.

What are the drawbacks with other energy storage solutions, such as lithium ion?

Lithium ion is just a very different technology. It has a high round-trip efficiency, but the cost is high and the land requirements for something that can adequately replace a peaking power plant make it fairly inaccessible, both from a cost and physical footprint perspective. Other types of long-duration energy storage, such as iron-air and compressed air, lack the power density that we have. They’re all really good technologies, but they will require significantly more land than we do. What we’re focused on are places where peaking power plants are either retiring or where utilities want to build new abilities to deal with peak power in a physically confined environment, and we think that that’s what the grid will need over the next 20 years.

What energy sources do peaking power plants use?

These are very, very old plants for the most part. These peaking power plants, they might run 30 or 40 times a year. They use coal, they use natural gas, some of them use bunker fuel. This is very low-efficiency fuel with a fair bit of pollution and a fair bit of cost. In New Jersey, for example, there are 25 gas- and oil-fired peaking plants. Three-quarters of them are over 30 years old, and they primarily burn oil. These exist everywhere. These types of peaking plants, they’re very expensive, they pollute a lot, but they’re really important for the reliability of the grid.

As we add more renewable energy, how important is reliability?

It’s really important. Renewables have a high value for energy, meaning it’s very predictable when a solar or wind plant puts out power, but it’s not considered a high-reliability asset because storm clouds or less-than-expected wind make it so that it’s not an on-demand resource for the grid. This is what’s important about technologies like ours, long-duration energy storage technologies, because it allows you to weather, no pun intended, a long period without sun, without wind, or a winter storm, where you have stress on assets from all ends of the spectrum. Our goal is to not only make renewables more reliable, but actually to make the entire system more reliable by giving it more ability to manage all these different stressors.

What is Fourth Power’s solution?

Basically, we are a technology that takes electricity from the grid during periods when it’s cheap, or when it’s underutilized, and we use that to heat tin to 2,400 degrees Celsius. To put that in comparison, remember those old incandescent light bulbs? The tungsten filament in an incandescent light bulb is at 2,400 degrees Celsius. It’s actually a very similar profile to what we’re doing, except we’re doing it at a much larger scale. The liquid tin is transported through a piping network, made entirely out of graphite, which weaves through an assembly containing thousands of 1-ton carbon blocks, which are the equivalent of that tungsten filament. These massive carbon blocks are heated up to 2,400 degrees C. And, of course, as an object gets very hot, just like a light bulb, it emits large amounts of light. We have a specially designed solar cell called a thermophotovoltaic (or TPV) cell that we actuate into the heat and light source. We’re able to convert electricity to heat, store that energy as heat, and then convert it back to power whenever the grid needs it, using that type of solar cell.

How does it stay hot?

We maintain the heat through a wide insulation layer; it’s insulated with raw petroleum coke. And petroleum coke is, of course, the waste product of refineries. We essentially buy that raw petroleum coke, layer it on top of the carbon blocks, which means that the heat only escapes at about a percent a day. It stays very hot for a very, very long time. That’s why we have very long durations of power.

Can it scale with power demand?

One of the advantages of our system is that the duration for which you store power and the power that you put out are both independent, which means that over time you can add storage blocks to increase how long you store the power, or you can add power modules to increase the power output of your system. Both of them are independent, which allows the technology to scale with overall demand.

How much land is needed to build a utility-scale model of this system?

This is what’s exciting. So, a 1 gigawatt-hour battery—it could power 100,000 homes for 10 hours—can fit into a parcel the size of a football field. We’re getting to these extremely high temperatures, which allows you to move power more efficiently, therefore requiring less space for the infrastructure to move power around.

Are there safety concerns, like fires for lithium-ion batteries?

This is one of the reasons why we’re very optimistic about our technology. With an electrochemical battery, like lithium ion, their issue is what’s called a thermal runaway event, where you have a chemical reaction that is happening that you cannot unhappen. Rather, our system is housed in a completely inert environment.

All technologies need to look at the worst-case scenario. So, I’m going to walk you through our worst-case scenario. We have carbon blocks that are extremely hot. The first level of protection is that it’s in an argon environment, meaning there’s no oxygen. Let’s say that argon environment gets punctured, and oxygen goes inside. What would essentially happen is a lot of the heat would probably result in extreme damage to the overall facility. But it would just take weeks for it to cool down. There would not be an active fire. There would be significant damage to the system if all of the safety protocols were breached, but it wouldn’t have this spillover safety and community effect that we’re seeing from a lot of lithium-ion systems, where you have fires that are unmanageable and uncontrollable. There are safety issues with everything. The worst-case issue with our technology [is] a different level of safety profile than with other technologies.

How is Fourth Power using the roughly $50 million it has raised to date?

A lot is going into engineers. We’re building our demo. A lot of this is first-of-a-kind design work and building systems for our first functional demo. We have a team of about 30 brilliant folks, the majority of whom are engineers and who have fantastic experience to help us scale.

What’s next for Fourth Power?

We’re building a fully integrated demonstration right now outside of Boston, at our headquarters, which we expect to begin commissioning later this year. In 2027, we plan to begin building our commercial pilot, hosted at a customer’s site (that has not yet been announced), which will be approximately 10 times the size of our demo. Around 2028, we expect to be available in the commercial market. And we expect more commercial agreements as we go down the technology risk retirement curve, more commercial structures in place for early deployments.

The landscape of the energy system is just fundamentally changing. Power demand from AI data centers is causing the power sector to really look at how to tackle the triple crises of reliability, of affordability, and of climate change, both emissions as well as impacts of climate change. We’re in a once in a generation, once in a lifetime, moment now. And that’s why technologies like ours are right time, right place.