Most of the electrical energy entering an air compressor is released as heat, and a large share of it can be recovered for space or water heating. Correct sizing of the recovery system starts with a realistic estimate of the available heat.
Where the heat goes
- Oil cooler on lubricated machines
- Aftercooler on the air side
- Motor and drive losses
- Radiation from the package
Estimation
As a rule of thumb, around 70 to 90 percent of the shaft input power can be recovered as usable heat. Multiply motor input power by a recovery factor and by operating hours to estimate the annual energy available for heating.
Sizing the system
Size the heat exchanger and water pump for the maximum continuous heat output, and match the recovery loop to the actual heat demand. Hot water recovery works best where there is a year-round need, such as washdown, process heating or boiler preheat.