Innovative Approach to Gas Turbine Efficiency
A new enterprise has emerged with a compelling plan aimed at enhancing the efficiency of gas turbines that currently power data centres, employing liquid carbon dioxide as a key component. American Supercritical recently unveiled an impressive funding round of $8 million, with the ambition to modernise the inefficient gas turbines prevalent in many data centres. The initiative seeks to replace these outdated units with more energy-efficient alternatives, all while ensuring that emissions do not rise—though it is important to note that gas turbines will continue to emit carbon pollution. This innovative technology has the potential to be applied across a wide range of energy sources, especially as electricity demand continues to surge.
Co-founder Simon Shuham expressed their intent, stating, “We want to start with gas turbines, but eventually expand our scope beyond that.”
The Efficiency Dilemma
In the United States, the majority of large gas power plants utilise a series of thermal engines in a process known as combined cycle. Initially, turbines generate electricity through the combustion of compressed air and natural gas, followed by an independent engine that harnesses hot exhaust gases to produce steam and generate additional power. However, for various reasons, data centres across the country have predominantly chosen to rely on simple cycle turbines, which eliminate the steam component.
These simple cycle turbines prove to be substantially less efficient than their combined cycle counterparts. Typically, only around 35% of the energy from simple cycle turbines is converted into electricity, with the remainder escaping as exhaust gases. In contrast, combined cycle plants achieve efficiency rates of approximately 60 to 65%. As a result, simple cycle plants become a less environmentally friendly option, as they emit significant greenhouse gases.
The sheer size of some of these plants, coupled with their inefficiency, poses a significant threat to the climate. A case in point is a massive power facility in Texas, being constructed by Amazon, which is set to operate on simple cycle turbines and has been permitted to emit over 33 million tonnes of greenhouse gases annually—far exceeding the emissions of several smaller nations.
Understanding Supercritical CO2
The founders of American Supercritical believe that these small, inefficient turbines could serve as ideal candidates for supercritical CO2 technology. Carbon dioxide reaches a supercritical state when it is pressurised and maintained at a specific temperature, acquiring the density of a liquid while retaining gas-like behaviour. This unique state allows it to transfer energy more efficiently through significantly smaller equipment.
The company aims to integrate its units with small gas turbines to bolster power generation. While the turbines would continue to use gas, the supercritical CO2 unit can harness the hot exhaust gases produced by the turbines to generate additional electricity. Instead of utilising this heat to boil water and create steam, the heat is directly transferred through pressurised CO2, enabling extra energy production without additional emissions.
“We are essentially building miniature combined cycle plants,” Shuham remarked.
Substantial Efficiency Gains
Employing supercritical CO2 may also significantly reduce or even eliminate water consumption in the energy generation process, a feature that has garnered considerable interest from data centres. Notably, the CO2 operates in a closed-loop system, negating the need for replenishment. Co-founder Matthew Carlson, who has extensively researched supercritical CO2 for over a decade, compares this system to cooling systems that circulate CO2 for efficient temperature regulation.
Initially, the company plans to offer a 10-megawatt unit, which is relatively modest by gas power plant standards. American Supercritical estimates that incorporating supercritical CO2 units could enhance turbine efficiency by up to 50% without escalating greenhouse gas emissions or water usage. However, modernising all inefficient gas turbines powering data centres with supercritical CO2 units will not eliminate emissions entirely. The production and utilisation of natural gas, even with efficient turbines, contribute to global warming, and data centres represent a burgeoning source of pollution at a time when the world is striving to reduce consumption.
Advancements in Supercritical CO2 Technology
The application of supercritical CO2 in energy generation has been under investigation for over 50 years at various US national laboratories. In the past two decades, research has transitioned from theoretical studies to practical experimentation, propelled by technological advancements that simplify the pressurisation process. Doug Hofer, an advisor to American Supercritical and a former turbine engineer at GE, highlights significant innovations, including the development of more compact and cost-effective heat exchangers that facilitate the heating and cooling of CO2.
American Supercritical is not the only company striving to commercialise this technology, as noted by Subith Vasu, a professor of engineering at the University of Central Florida, who leads a laboratory focused on advanced turbomachinery and energy research. Companies face challenges that must be overcome to achieve commercial success. Vasu warns, “When venturing into new technologies, one must have all associated components and the supply chain ready.” He adds that technical obstacles abound, and “cost has been a significant concern.”
Hofer points out that part of the delay stems from major companies being content with the performance of traditional power plants and reluctant to invest in alternative technologies. Additionally, turbine manufacturers may be hesitant to fund potential competitors. “It’s the innovator’s dilemma, isn’t it?” he observes. “For this technology to gain traction, it requires external influence.”
The anticipated $7 trillion investment in data centres globally by 2030 has opened a new market potential, especially for an industry competing for the greatest amount of energy possible from the electrical grid to gain an advantage in the artificial intelligence race.
“There is an incredible willingness to pay [for energy], but they face supply issues,” asserts Shuham. “The goal is to intervene, modernise their current systems, and enable them to build additional data centres or eliminate some of the gas turbines.”
Earlier this year, China announced the commencement of operations at the world’s first geothermal plant using supercritical CO2. Carlson states that throughout his professional journey, he has engaged in supercritical CO2 applications in nuclear, geothermal, and solar energy. Both he and Shuham affirm that their units could be adapted to work with small modular reactors, a technology that has received strong backing from the Trump administration. The company claims to have already signed an initial agreement with a yet undisclosed firm, and it also indicates compatibility with other heat sources.
“All we need is to heat something, and we can convert that into electricity,” concludes Carlson.