One Inch Supercritical CO2 Micro Turbine Performance at 100 C, 300 C, 500 C, and 700 C
One Inch Supercritical CO2 Micro Turbine Performance at 100 C, 300 C, 500 C, and 700 C
OverviewSupercritical CO2 (sCO2) micro turbines offer compact, high-density power at small scales. This article presents a sizing study of a purpose-designed one inch diameter sCO2 radial inflow turbine. Power output estimates are given at four turbine inlet temperatures, along with heat rates expressed in BTU per kilowatt.Design BasisTurbine outer diameter: 25.4 mm (1 inch)Inlet annulus height: ~0.5 mmInlet pressure: ~150 barTurbine isentropic efficiency: ~70 percentWhole cycle (turbine + recuperator + generator + compressor) derating: ~30 percentHeat sink: ~40 C (104 F)Estimated Shaft Power OutputBased on flow area, density, and enthalpy drops across typical stage pressure ratios, the one inch turbine could deliver:100 C inlet: ~6 kilowatts net300 C inlet: ~7 kilowatts net500 C inlet: ~8 kilowatts net700 C inlet: ~8.5 kilowatts netHeat Rate in BTU per KilowattHeat rate is the amount of heat input required per unit of power output. Conversion uses 1 kWh = 3412 BTU.100 C source, 40 C sinkPractical efficiency ~6 to 12 percentHeat rate ~28500 to 57000 BTU per kilowatt300 C source, 40 C sinkPractical efficiency ~20 to 30 percentHeat rate ~11400 to 17100 BTU per kilowatt500 C source, 40 C sinkPractical efficiency ~35 to 45 percentHeat rate ~7600 to 9750 BTU per kilowatt700 C source, 40 C sinkPractical efficiency ~45 to 55 percentHeat rate ~6200 to 7600 BTU per kilowattKey Insights1. Low temperature operation (100 C) produces measurable shaft power but with poor efficiency. Heat rate is very high, meaning large amounts of heat input per kilowatt.2. Moderate temperatures (300 C) improve efficiency significantly, reducing heat rate to values comparable with early generation steam turbines.3. High temperatures (500 C to 700 C) are where sCO2 cycles shine. Power per unit size improves and heat rates drop into the same range as large modern power plants, even in this small micro turbine format.4. Mechanical limits—tip speed, rotor stress, and sealing—become the practical bottlenecks for higher inlet temperatures rather than thermodynamics.ConclusionA one inch diameter supercritical CO2 turbine can produce between 6 and 8.5 kilowatts of shaft power depending on inlet temperature. Heat rates range from nearly 60,000 BTU per kilowatt at 100 C down to around 6,200 BTU per kilowatt at 700 C. The results show that compact sCO2 hardware has real potential, but only at higher turbine inlet temperatures does it achieve competitive efficiency.
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