Predicted efficiencies still far short of the 50% thermal efficiencies
claimed for sCO2 at a 600 C turbine inlet temperature. This is
primarily a limitation of the laboratory-scale demonstration turbine
used for the present study. At around 250 kWe in size, the test
facility was intended to be large enough to confront the fundamental
issues for sCO2 Brayton cycle technology, but small enough to
be affordable over several years of incremental funding. For adoption
of sCO2 in a solar-thermal power plant, a number of required
advances remain and are largely addressed by moving to larger
equipment in 10 MWe range. For large capacity factors and indirect
systems, heat exchange between CO2 and a secondary fluid amenable
to solar is also required. This represents a significant challenge
in terms of material selection as well as heat exchanger design.
Improvements in bearings and seals to prevent leakage are also required,
especially as the system scales up from the small prototype
included here.