A heat pump extracts heat from a source, such as the battery pack, it then amplifies (increases the working fluid temperature) and transfers the heat to a radiator where it can be cooled by the ambient air.
This process can be run in either direction, hence a battery pack can be cooled or heated. The heating is achieved by extracting heat from the air, pumping that to a higher temperature and then cooling the working fluid using the battery cells.
The amount of energy put into pumping the working fluid compared to the heat moved between the source and sink is known as the coefficient of performance (COP). Typically COP values are between 3-5. That means for 1kWh of energy put into the heat pump it provides between 3kWh and 5kWh of heating or cooling.
A heat pump is one of several battery cooling options, sitting at the more complex end of the range compared with approaches such as passive cooling.
References
- Lars Reinholdt, Jóhannes Kristófersson, Benjamin Zühlsdorf, Brian Elmegaard, Jonas Jensen, Torben Ommen, Pernille Hartmund Jørgensen, Heat pump COP, part 1: Generalized method for screening of system integration potentials, Danish Technological Institute
See also: Battery Heating