New compressor for residential heat pumps

Space heating and domestic hot water in the residential sector represent a major source of energy consumption, especially in Nordic countries. In Canada, this use represented 1,200 PJ in 2019, or 3.6 times that of air transport, with the majority coming from fossil fuels, contributing to over 7% of the country's greenhouse gas (GHG) emissions. Large-scale deployment of residential heat pumps for space heating and domestic hot water would make a major contribution to decarbonizing the economy and reducing GHGs. A particular challenge would be to create a new generation of cold-climate heat pumps that would increase their heating capacity and energy efficiency at low temperatures. On the other hand, they could also be used for heating in electric vehicles, replacing the inefficient electric resistance heating so detrimental to their autonomy that some of these vehicles have to heat with fossil fuels. Finally, air conditioning, which can also be provided by heat pumps, accounts for 7.8% of global GHG emissions. To achieve the 50% increase in air-conditioning system efficiency by 2030 targeted by the Global Cooling Pledge (COP28), improvements are needed. But one of the components of heat pumps - the compressor - is fragile, and when it breaks down, it's difficult to repair and expensive to replace, partly because of the small size of residential heat pumps. What's more, their operation is not optimal for energy efficiency.

However, residential heat pumps could be cheaper and more efficient: the compressors they typically use could be replaced by equivalents that are less costly to replace and offer better isentropic efficiency. Instead of scroll compressors, Professor Vo's team is proposing the use of centrifugal compressors, and has even developed a new model whose key component, the impeller, has a geometry simple enough to operate at lower speeds and undergo less stress, allowing it to be made of plastic rather than machined metal. The lower cost of this type of compressor could also make it easier to adapt heat pumps to colder climates by using several compressors in series. This promising technology has already achieved good results in numerical simulation on a preliminary design, but a prototype still needs to be designed and manufactured before it can be validated in the laboratory.

This new compressor will then have to be integrated with the other components of a residential heat pump featuring a low GWP (Global Warming Potential) refrigerant, and tested to measure the increase in compression efficiency and coefficient of performance compared with the original scroll compressor heat pump. The long-term aim of this project is to commercialize a new compressor that would reduce the cost of small heat pumps, so that they can be rapidly deployed for residential heating and in electric vehicles, thereby reducing GHGs and energy consumption.