Certainly interesting tech. While the energy-per-massflow is pretty crap for co2 compared to water, that doesn’t matter since in a sealed recirculating system it’s cheap to just increase mass flow. But co2 tranistions from liquid to SC-fluid at pressures equivalent to current LP steam turbines, but at a fraction of the temperature (31C at 7.3MPa). You would need the phase change for maximum heat movement/volume change of course.
But this does mean that if your initial charge was precise enough, you could very well drive one of these power cycles with a heat source that operated only a little higher than human body temperature with significantly cheaper engineering materials (albeit at a terrible efficiency). Pretty wild to think about from a thermodynamics perspective.
More specifically, it behaves as a supercritical fluid above its critical temperature (304.128 K, 30.9780 °C, 87.7604 °F)[1] and critical pressure (7.3773 MPa, 72.808 atm, 1,070.0 psi, 73.773 bar),[1] expanding to fill its container like a gas but with a density like that of a liquid.
For perspective on that pressure: a US natural gas car fills at 3,600psi (240 Bar)
Supercritical C02 turbines are fuel agnostic, but the really interesting development here is using them in conjunction with concentrated solar power systems. Power cycles based on a sCO2 working fluid have the potential for higher thermal efficiencies and a lower capital cost when compared to state-of-the-art steam-based power cycles.
Concentrated solar power has long taken a back seat to photovoltaics as the dominant means of generating solar power, but maybe it’s about to have a renaissance. Australia’s National Science Agency CSIRO, says it has made a key breakthrough with concentrated solar thermal technology (CST) that could see it act as grid storage batteries.
This article contains a turbine picture…
