Okay thanks so i did understand something wrong. But couldnt one use something like an gas turbine to heat it Up? With the right combination one could get some pretty huge Energy out of it which is perfect for ships. I think that was called combined powerplants or so.
One could use
any source of heat: gas turbine exhaust, fossil fuels, nuclear, solar, biomass, geothermal.
Combined cycle plants are fairly common, and have nameplate efficiencies pushing (or exceeding) 50%. Frequently, they use gas turbine exhaust to heat water. A combined cycle plant was proposed as an improvement for the USN's Burke class destroyers but was canceled due to worries about reliability and maintainability.
This supercritical CO2 cycle may be a great bottoming cycle, as it may be able to use a fairly low temperature heat source. Supercritical CO2 is much easier than supercritical H2O, which is fairly common for modern utility plants, as the pressure can be lower that with water.
As an aside, binary cycles (where this CO2 turbine may be used) are fairly old technology,
e.g., HELCO's South Meadow station (mercury Rankine cycle topping a conventional steam cycle) which was commissioned in 1929 and decommissioned sometime in the 1960s.
There have been a number of alternatives to water proposed as working fluids for Rankine cycles, including ammonia, mercury, potassium, cesium, organics,
e.g., Freon, and sulfur. There have also been cycles built around mixtures, such as the Kalina cycle, and various absorption cycles. Overall, I think I'd much rather have a CO2 turbine running in my neighborhood than one using ammonia, sulfur, or (God help us), mercury.