Supercritical Carbon Dioxide Power: A Revolutionary Development in Energy Technology

“When a temperature and pressure increase beyond the critical point, a substance enters a supercritical state where a distinction between liquid and gas phases does not exist. The critical temperature and pressure of CO2 are 31℃ and 74 bar, respectively, which are relatively easy to reach. This study started from the idea that those properties of CO2 can be tapped into power generation. Approximately a 3 to 5 percent increase in generating efficiency is expected when using the supercritical CO2 power system, where the waste heat is retrieved and used in power generation. Given that only a 1 percent increase in generating efficiency at every power plant in Korea has the same effect as building two nuclear power plants, a small increase in generating efficiency creates a substantial ripple effect from a technological perspective. This study is a future-oriented one in that it holds not only the technical values regarding a patent, but also the potential to provide solutions to the energy problem, one of the most important issues globally.”

The next generation power technology with increased efficiency and smaller system size

An efficient use of energy has been a shared concern among numerous engineers around the globe since the world is now faced with an energy issue. Domestically, the development of more advanced energy technology is urgent because Korea is now importing more than 90 percent of its energy from abroad. Professor Lee, Jeong Ik and his CO2 research team looked into the ‘Supercritical CO2 Power System’, which utilizes carbon dioxide for power generation.

Most of the power generated throughout the world comes from steam turbines using water or a gas turbines generating power by combusting the fuel gas with compressed air. The problem is that those two methods and the material technologies employed have almost reached their limits in terms of increasing the efficiency. With those methods, thermal efficiency, reduction in CO2 emission, and other performances have very little room for further improvement. Still, those methods have their own strengths: the steam turbine uses less energy than the gas turbine in the water pressurizing process, while the gas turbine has higher efficiency than the steam turbine as it generates power at higher temperature, producing higher output in smaller-sized equipment when compared to the steam turbine.

The ‘Supercritical CO2 power system and its operating method by changes in heatsink temperature (patent)' suggested by Professor Lee’s team combines the merits of the two conventional generating methods mentioned earlier; this new system has 3 to 5 percent higher generating efficiency and requires approximately a tenth of the facility size when compared to the conventional methods. The team applied for a patent for this system.

This study started five years ago from basic research on a generating system employing nuclear energy. It was assumed then by the team that before applying the technology to the nuclear energy, it should first be applied to gas turbines, industrial waste heat recovery including high temperature fuel cells, all of which have relatively lower risk, as preparatory stages for pilot plant establishment and further research on the commercialization. At that time, Saudi Aramco established the ‘Saudi Aramco – KAIST CO2 Management Center’ at KAIST in order to conduct research centering on greenhouse gas emission reduction and to develop a supercritical CO2 power system boasting higher generating efficiency. In response, Professor Lee’s team researched the waste heat source at combined cycle power plants, which at that time were recently established in Saudi Arabia. The team is now working on a project titled, ‘Development of high efficiency gas turbine combustion system using CO2 basic cycle’ for the third year and plans to proceed with empirical and follow-up studies going forward.

It is expected that the supercritical CO2 power technology may suggest a key solution to the overall energy problems and can be utilized in a wide array of areas, including turbomachinery design technology, supercritical fluid technology, and technology for natural gas liquefaction and storage in a vessel. It is also expected that the power generation without consuming water can be realized in desert environments in places like Saudi Arabia once the patent-pending research on the system configuration and operation method of the supercritical carbon dioxide generation by heatsink temperature is optimized. Through this technology, a power plant can maintain decent performances in an environment where the difference in temperatures between day and night is great, as in a desert. Furthermore, power generation near urban areas and a reduction in greenhouse gases can also be expected with the increased efficiency and compact size of the generating facilities employing the supercritical CO2. Thanks to these merits, the supercritical CO2 power system is highly acclaimed as a revolutionary energy technology for the next generation.

Prof. Lee, Jeong Ik
2015 Annual Report