This can happen when the fuel cell is shut down after normal operation without applying any mitigation strategies. Alink, in Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, 2014 Shutdownĭegradation by low temperatures after shutdown is mainly caused by the volume expansion of residual water during phase transition from liquid to solid phase. But GSHP system operating costs tend to be lower than those for air-source heat pumps.īoth ground- and air-source heat pumps can provide heating in the winter and, through a reverse operation mode, cooling in summer. Although the cost of GSHP systems can vary, installation costs are normally lower for air source rather than GSHPs. Īir-source heat pumps are relatively simple to install compared to GSHPs, and the earth connection in a GSHP is usually difficult to reach after installation. Air-to-water heat pumps are typically used in residential buildings having hydronic heat distribution systems.
Bivalent heat pumps are a special type, developed in Canada, that use a burner to increase the air temperature entering the outdoor coil, permitting operation at lower outdoor temperatures. Add on heat pumps are designed to be used with another source of supplementary heat.
Air-source heat pumps can be add-on or all electric or bivalent. The most common is the air-to-air heat pump, which extracts heat from the air and transfers it to either the inside or outside of the building, depending on the season. There are two types of air-source heat pumps: air-to-air and air-to-water. Īir-source heat pumps draw heat from the outside air during the heating season and reject heat to the outside air during cooling season. During summer months the process is reversed, with heat extracted from the indoor air and transferred to the ground. Heat is removed from the earth via a liquid, such as ground water or an antifreeze solution, and the temperature of the liquid is raised by the heat pump and the heat is transferred to indoor air. Ruzhu Wang, in Handbook of Energy Efficiency in Buildings, 2019 8.1 Comparison of Ground- and Air-Source Heat PumpsĪ GSHP uses the ground or water in the ground or both as the sources of heat for buildings in the winter and as sinks for heat removed in the summer.
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