Low Carbon Refrigeration Technology for Sustainable Buildings
Refrigeration and cooling account for a significant fraction of total energy consumption and greenhouse gas (GHG) emission of urban buildings. Conventional vapor-compression refrigeration technology uses GHG refrigerants, e.g., chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HFC) with high global warming potential (10-300 times of CO2) and they are difficult to be recycled. The coefficient of performance (COP) of vapor-compression refrigeration is 3-4, and it is difficult to be further improved. For the above-mentioned reasons, the existing vapor-compression refrigeration faces challenges to meet the requirement of energy saving and carbon neutrality, and it should be gradually substituted by more environmentally friendly refrigeration technologies.
To overcome this challenge, a zero-GHG-refrigerant and 100%-recyclable solid-state elastocaloric refrigeration technology based on phase-transition shape memory alloys has been developed by a research team based in Hong Kong. Compared to other refrigeration alternatives, the elastocaloric refrigeration completely avoids the use of GHG refrigerants and has very high cooling power and efficiency with a material COP of up to 30. The elastocaloric refrigeration is realised by cyclic compression of nickel-titanium shape memory alloy (SMA) tubes, where the martensite-to-austenite phase transformation absorbs a large amount of heat from the surrounding environment.
By optimizing the tubular structures, the first-generation elastocaloric refrigeration prototype achieved a total cooling power of 218 watt and a temperature span of 75 ℃, which are the highest among existing elastocaloric cooling prototypes. In addition, the COP of the prototype is expected to be about 8. The research team anticipated that a cooling power of 1000 watt will be achieved by this year and 2000 watt in the coming year. They are seeking co-development partnerships with metal manufacturers or device manufacturers based in Singapore to support the scale up of their prototypes.