Supercritical carbon dioxide power plants, which use CO2 heated above its “critical” temperature and pressure so that it is in a fluid state, have the potential to improve fuel efficiency compared to traditional steam and water systems.
The US Department of Energy says these systems, if successful, could greatly improve the efficiency of geothermal, coal, nuclear and solar thermal power production, while also reducing emissions.
Supercritical CO2 power systems could also “significantly” reduce the size of future power plants, says Franklin Orr, DOE’s under secretary for science and energy. “Smaller size and increased efficiency can lead to lower costs and fewer greenhouse gas emissions,” Orr said.
But here’s the problem: no commercially feasible supercritical CO2 plant exists.
A new $110 million project, managed by the Gas Technology Institute (GTI), Southwest Research Institute (SwRI) and General Electric Global Research aims to change this.
Last week the DOE said it will award up to $80 million for this six-year project, which will design, build and operate a 10-megawatts electrical supercritical CO2 pilot plant test facility in San Antonio, Texas. GTI and and SwRI will provide an additional $30 million, San Antonio Express-News reports.
The experimental project aims to advance commercialization of supercritical CO2 power systems by testing the potential energy efficiency and cost benefits of this technology.
Today the average efficiency of the US fleet of steam Rankine cycle power plants is in the lower 30 percent range, according to the DOE, which says this new facility has the potential to demonstrate greater than 50 percent cycle efficiency.
The project will provide an “opportunity for industry and government to work together” on supercritical CO2 facilities, “bringing it one step closer to commercialization,” the DOE said in a statement.
The pilot power plant will be located at SwRI’s headquarters. In a statement, SwRI president Adam L. Hamilton said the institute is “proud to be part of a project that will demonstrate the world’s first large-scale sCO2 power plant.”
But is it feasible at scale? Lux Research analyst Yuan-Sheng Yu says it’s too early to say. “However, it should be noted that the involvement of GTI in this project would have one of the leading energy technology R&D institutions driving the technology behind this project,” he said.
The price point — $110 million for 10MW of installed capacity — is high, compared to other forms of renewable energy, Yu added. On a dollar-per-installed capacity basis, solar PV, wine and even biomass combined heat and power are all closer to $2 per megawatt to $6 per megawatt, according to the National Renewable Energy Laboratory.
A major challenge with supercritical CO2 is the amount of energy input requires to heat CO2 above critical temperature and pressure points. “The efficiency rate of 50 percent will be critical to potentially offset any additional cost inputs for an already more capital expensive process,” Yu said.
“However, the emission benefits of supercritical CO2 is also one of the main value propositions of the process that first offers a potential near-term solution of reducing CO2 as carbon capture continues to struggle to gain traction due to its high costs and second can potentially also reduce NOx and SOx emissions that are also key areas that regulatory policies are looking to become more stringent on,” Yu said. “And as utilities today continue to ‘clean up’ their electricity mix, the opportunities of supercritical CO2 could potentially be a low-hanging fruit before utilities take the leap towards more traditional forms of clean electricity such as solar, wind and hydro.”