Global warming and the growing demand for energy are two primary problems rising in the power generation industry. A simple solution to these problems has been researched for a number of years. The SCO2 Brayton cycle is often looked into as an alternative working fluid for power generation cycles due to its compactness, high efficiency and small environmental footprint. The usage of SCO2 in nuclear reactors has been studied since the early 2000s in development of Generation IV nuclear reactors, but the idea itself can be traced back to the 1940s. During this time however, no one really looked into the potential of supercritical CO2 since steam was found to be efficient enough, not to mention it was the more understood technology when compared to SCO2. In modern times though, demand of more efficient energy continues to rise and with it, the need for SCO2.
The potential of supercritical CO2 implementation is vast across power generation applications spanning nuclear, geothermal and even fossil fuel. The cycle envisioned is a non-condensing closed loop Brayton cycle with heat addition and rejection inside the expander to indirectly heat up the carbon dioxide working fluid.
Supercritical means that the working fluid (carbon dioxide) should be kept running above its critical points (critical pressure and temperature) or 31 degree Celsius and 73 atmosphere, where it would inherit both liquid and gas characteristics, flowing like a liquid but filling containers like a gas. During the supercritical condition, SCO2 is dense, thus resulting in increasingly simple and small turbine designs. This fact leads to the probability of reduced cost in the long term.
The benefits of using carbon dioxide as a working fluid aren’t limited to what was previously mentioned in the paragraph above. Carbon dioxide is also predicted to generate more electricity per thermal input (higher efficiency) due to its lower value of compression work, reduction of greenhouse gases, and lowered water consumption, making it environmentally friendly. The cycle shows huge potential to recover low grade waste heat and no pinch limitation in the heat recovery vapor generator.