Accelerating the shift from fossil fuels to new and renewable energy sources is in line with the Korean government’s recent attempts to meet the aim of “going carbon neutral by 2050.” In this regard, the collaborative research team comprising professors Min-sung Kim and Dong-kyu Kim of Chung-Ang University and Principal Researcher Young Kim of the Korea Institute of Machinery and Materials (KIMM), an organization under the purview of the Ministry of Science and ICT, has effectively developed an environmentally friendly refrigerant compressor by employing an electrochemical technique as opposed to a mechanical one.
A module-type heat pump system featuring the electrochemical compressor. Image Credit: Korea Institute of Machinery and Materials.
Unlike conventional refrigerants that contain HFCs (hydrofluorocarbons), which deplete the ozone layer and cause global warming, environmentally friendly refrigerants (ammonia, R1234yf, and so on) have minimal environmental impact.
According to the Kigali Amendment to the Montreal Protocol, advanced nations in Europe, as well as the United States and Japan, are migrating to eco-friendly refrigerants until the use of HFCs is completely phased out in 2024. Using environmentally friendly refrigerants can help to prevent pollution and contribute to long-term growth.
Meanwhile, mechanical compressors have various limitations, including problems with part durability owing to rapid rotation, refrigerant contamination caused by lubricants, and loud noise. Since electrochemical compressors have no moving parts and do not require lubricants, they can assist in overcoming the drawbacks of traditional mechanical compressors.
Furthermore, electrochemical compressors can deliver a steady flow rate at varying pressure ratios, and their excellent effectiveness can help to significantly boost the heat pump's COP (coefficient of performance).
The research team created an “optimized smart farm operating solution” that can regulate all system components, including the air conditioner, LED lights, and hydroponic system, based on the outside weather. They intend to use the rooftop greenhouse to demonstrate this solution to optimize the energy-saving potential of the greenhouse.
The collaborative research team has successfully completed the test run and acquired the key technologies required to produce the environmentally friendly electrochemical refrigerant compressor and design its system. By stacking, the recently invented environmentally friendly electrochemical refrigerant compressor can achieve the required pressure and flow rate.
An electrochemical compressor, as opposed to a traditional mechanical compressor, uses hydrogen as the carrier gas and charges the ion exchange membrane with DC (direct current) voltage to compress refrigerants by the movement of ions.
Using a multi-layer freezing technique where cells are stacked in a stack structure also permits isothermal compression. Ammonia, a natural refrigerant, and R1234yf, an environmentally benign refrigerant, are the only refrigerants that have been effectively compressed.
The collaborative research team demonstrated a leak-free design to stop refrigerant leaks at high pressure and created cells that can function steadily even under frequent high-pressure circumstances. Furthermore, by creating a channel that can function well even at high voltage, the collaborative research team has maximized the electrochemical compressor’s compression efficiency.
Regardless of its size, the electrochemical compressor can deliver the required compression ratio, maintain a steady flow rate in line with the ratio, and operate extremely efficiently.
As a result, it can be utilized to design small-scale systems in addition to highly efficient plants and heat pumps. Specifically, an electrochemical ammonia compressor can be utilized for building hydrogen infrastructure since it can compress ammonia even while it serves as a transport of hydrogen.
The eco-friendly electrochemical refrigerant compressor is highly efficient and requires a small footprint, which makes it economically attractive. We are planning to develop a heat pump system using this technology to contribute to the achievement of the goal of going carbon neutral by 2050.
Dr. Young Kim, Principal Researcher, Department of Thermal Energy Solutions, Korea Institute of Machinery and Materials
The Korea Institute of Energy Technology Evaluation and Planning of the Ministry of Trade, Industry, and Energy oversaw the project for the “development of a chemical absorption-type heat pump using an electrochemical compressor,” which provided funding for this study.
Journal Reference:
Kim, M. S., et al. (2023) Parametric study on the performance of electrochemical hydrogen compressors. Renewable Energy. doi:10.1016/j.renene.2022.09.081.