A small startup just stepped out of the shadows with a fairly ambitious idea: take the dirty, inefficient gas turbines that keep so many data centers running and make them dramatically better. American Supercritical, a company that has been quietly working on this problem for a while, announced this week that it has raised $8 million in funding and is ready to talk about what it’s been building. The pitch is not to eliminate natural gas overnight, and it’s not to tear down the massive power plants that feed the world’s most powerful computers. Instead, the company wants to retrofit those plants with a clever new piece of technology that uses carbon dioxide in a strange, pressurized state to squeeze much more electricity out of the same amount of fuel. It’s a plan that could make a meaningful dent in the emissions footprint of the booming data center industry, and eventually, maybe, a much wider slice of the energy world. The company’s cofounder, Simon Shuham, says the goal is to start with gas turbines but eventually expand far beyond them. And that matters, because right now the demand for electricity is climbing at a pace that has utilities and grid operators scrambling, and data centers are one of the biggest reasons why.
To understand why American Supercritical’s technology matters, you have to understand the strange gap between the way we generate electricity and the way we waste it. Most of the largest gas-fired power plants in the United States use something called a combined-cycle process. It’s a two-step dance. First, a turbine burns a mixture of compressed air and natural gas to spin a generator and make electricity. But that burning process produces extremely hot exhaust, and instead of just letting that heat vanish into the sky, a combined-cycle plant captures it and uses it to boil water into steam. That steam then spins a second turbine and makes even more electricity. It’s an elegant system, and it’s why the most modern gas plants can convert around 60 to 65 percent of the energy in their fuel into useful power. But many data centers across the United States have chosen a simpler, cheaper route. They rely on what are called simple-cycle turbines, which skip the steam step entirely. These machines are faster to build, cheaper to install, and easier to operate, but they pay a steep price for that simplicity: they typically convert only about 35 percent of the fuel’s energy into electricity. The remaining two-thirds or so escapes as hot exhaust, a plume of wasted potential that also carries greenhouse gases into the atmosphere. That means a data center powered by simple-cycle turbines is taking much more gas to produce the same amount of power, and emitting far more carbon pollution for every megawatt it uses.
The scale of that inefficiency is genuinely startling, especially when you consider how enormous data centers have become. These facilities need electricity around the clock, and the companies building them want power on demand, without waiting years for a highly efficient combined-cycle plant to be designed, permitted, and constructed. The result is a wave of new simple-cycle gas plants rising up to serve the cloud, and some of them are truly massive. Take a facility in Texas that Amazon is building. It is powered by simple-cycle turbines and is permitted to emit more than 33 million tons of greenhouse gases each year. To put that in perspective, that’s more than the annual emissions of some entire small countries. It’s an enormous environmental toll for a single data center project, and it’s happening at exactly the moment when the world needs to be cutting emissions, not adding new sources of them. Data centers are a kind of climate paradox: they power the digital economy and all its innovations, but they are also becoming a major source of pollution. And because they need ultra-reliable power, they have turned an old, well-understood, but highly wasteful technology into a growth engine for fossil fuel use. That’s the problem American Supercritical is trying to address, not by asking data centers to shut down or demanding they abandon gas entirely, but by making those simple-cycle turbines work much harder for the climate.
The key to the company’s approach is something called supercritical carbon dioxide, and it’s genuinely fascinating once you understand what it is. Carbon dioxide becomes supercritical when it is heated and squeezed beyond a certain threshold of temperature and pressure. In that state, it occupies a kind of twilight zone between liquid and gas. It has the density of a liquid, which means it can pack a lot of energy into a small space, but it also flows and fills its container like a gas, which makes it incredibly responsive and easy to move. This unusual combination makes supercritical CO2 a fantastic medium for transferring energy. American Supercritical wants to attach a unit filled with this pressurized CO2 to the exhaust of a simple-cycle gas turbine. As that scalding hot exhaust flows past, it transfers heat directly into the carbon dioxide, which rapidly expands and spins a turbine of its own, generating additional electricity. Unlike traditional combined-cycle plants, there’s no water involved, no boiling, no steam. The heat goes straight from the gas turbine’s exhaust into the CO2, and that energy is converted into more power. The founders describe it as building miniature combined-cycle plants, and in a sense that’s exactly what it is. But it’s a much smaller, simpler, and more adaptable version of the idea, one that can be bolted onto existing turbines instead of requiring a massive new power plant.
There are several reasons this approach is so attractive for data centers, and one of the biggest is water. Traditional steam-based power generation uses enormous amounts of water for cooling and condensation, and data centers already draw intense scrutiny for their water use. Supercritical CO2 systems operate in a closed loop, meaning the carbon dioxide is sealed inside the unit and continuously reused. The company’s other cofounder, Matthew Carlson, who spent more than a decade studying supercritical CO2, likes to compare it to a refrigeration system: the same fluid circulates over and over again, moving heat from one place to another without being consumed. That means the system can generate additional electricity without requiring a constant supply of fresh water, and it doesn’t release the CO2 it uses either. According to American Supercritical’s calculations, adding their units to a simple-cycle gas turbine could boost the turbine’s efficiency by as much as 50 percent, all while producing no additional emissions and using no additional water. The company plans to start by selling a 10-megawatt unit, which is relatively small by gas plant standards, but small is part of the point. These units can be stacked or paired with individual turbines, retrofitted into existing plants, and scaled to match the needs of a particular data center. It’s a flexibility that the huge, centralized combined-cycle plants simply don’t offer, and it could make a real difference in an industry that needs power fast and has a growing list of environmental obligations.
Of course, this technology is not a magic wand. Retrofitting every inefficient gas turbine powering a data center would still leave a huge emissions problem, because natural gas itself, even when burned with far greater efficiency, is still a fossil fuel that warms the planet. American Supercritical is not claiming to make data centers green in the absolute sense. What it’s offering is a way to make them meaningfully less destructive while they still rely on gas, and to provide a bridge to whatever comes next. The company’s founders are quick to point out that the underlying supercritical CO2 technology could eventually be used with all sorts of energy sources, not just natural gas. It could capture waste heat from industrial processes, squeeze more power from geothermal or solar thermal systems, or improve a wide range of power generation technologies that produce hot exhaust. In a world where electricity demand is skyrocketing, partly because of artificial intelligence, cloud computing, and the digitization of just about everything, squeezing more useful work out of every unit of fuel is a crucial step. The startup’s first target is the simple-cycle gas turbines that have become the default choice for data centers, and that’s a smart place to start. But the bigger picture is about rethinking the way we treat heat and waste in the energy system, turning what is currently pollution and inefficiency into something useful. It won’t solve the climate crisis alone, and it shouldn’t distract from the urgent need to build truly clean sources of power. But if American Supercritical can deliver on its promise, it could buy the world a little more time, and give the data center industry a better way to grow without using quite so much dirty energy. In the meantime, the company is banking on a simple idea: that even in the middle of a revolution, making the existing system less wasteful is a revolution of its own.
