Evaluating performance of supercritical CO2 power plants

The supercritical CO2 power cycle is one of the most promising power technologies. It is not by chance though, because carbon dioxide (CO2) has a unique combination of attributes, such as a low critical temperature, an environmentally natural origin, a high standard of safety and a low cost. Carbon dioxide is also thoroughly studied, therefore there is sufficient information surrounding it. But on the other hand, the supercritical CO2 cycle has a high energy conversion factor, such as high thermal efficiency.

It is necessary to keep in mind that the correct supercritical CO2 cycle performance calculation requires very precise models of heat exchangers and turbomachinery because a relatively small error in efficiency estimation can cause quite a significant cycle efficiency deviation.  Such deviation is significantly higher for S-CO2 cycles in comparison with Rankine cycles, for factors such as:

• The ratio of turbine work to pump work in the Rankine cycle is quite large and only a turbine performance can cause a significant effect on cycle efficiency. In a S-CO2 cycle ratio of turbine work to compressor work it is relatively small and namely it causes a significant influence on cycle efficiency (i.e. it is necessary to correctly calculate not only a turbine’s efficiency but a compressor’s efficiency – mistakes cost too much).
• The structural aspects of turbomachinery for S-CO2 cycles also should be considered because high capacity S-CO2 power plants structural limitations can cause a significant effect on turbine or compressor design.

Today we can observe a lot of articles devoted to the consideration of different S-CO2 cycle modification applications in waste heat recovery, in concentrating solar power plants (CSP), in nuclear power plants and others. In turn, each author of the S-CO2 cycle modification uses some specific tool to analyze the performance of the main power components (turbine, compressor, heat exchanger etc.,) as a whole cycle performance.

But by far, not all industry and commercial software precisely calculate turbine work, compressor work or heat exchanger efficiency because efficiency usually of these components is simply assigned but not calculated. It is obvious that it is possible to correctly calculate S-CO2 cycle performances by only a combination of precise tools for cycle performance calculation with a precise turbomachinery calculation tool.

An advanced system can help engineers to facilitate and accelerate a high quality design of a supercritical CO2 power plant.