Simply put, sCO2 cycles can be applied where steam cycles are currently used, with the maximum temperatures limited by the materials of construction. The highest temperature at which a turbine has been tested in a CO2 environment is 715°C. Due to the relatively low temperature drop during expansion in the turbine, the cycle must recover the maximum possible amount of heat to achieve high efficiencies. This also leads to high inlet temperatures from the heat source. For this reason, the cycle is less suitable for fossil fuel heat sources, there would be high chimney losses and thus lower exergetic efficiency unless additional, usually costly measures, are used. As a consequence, the cycle is well-suited for advanced nuclear reactors or the majority of energy storage systems based on TES (thermal energy storage). For various reasons these types of systems require higher coolant inlet temperatures.