Temperature and simultaneous demand are decisive
First establish heat output and its temperature level for the particular machine. Then compare demand over the day and year. Summer compressor operation will not save hall heating without suitable summer heat demand. The transfer heat exchanger has losses and requires a temperature difference.
The compressor must still be cooled with no heat demand
The installation must safely reject heat even when the storage tank has reached its set temperature or production does not need heat. Heat recovery must not disable essential cooling. Payback then compares investment with the energy actually replaced, the original source's energy price and its efficiency.
What to check in practice
- Measure compressor operation and heat demand simultaneously.
- Verify achievable outlet temperature and heat transfer capacity.
- Include auxiliary energy, maintenance and operation without heat demand in the financial assessment.
Example scenario
A usable 20 kW over 1,500 overlapping operating hours represents 30,000 kWh of heat. If it replaces a source with 90% efficiency, this corresponds to about 33,300 kWh of that source's input energy. Its price, additional costs and investment then determine savings and payback.
What to watch out for
- Multiplying maximum heat output by all operating hours without accounting for seasonality.
- Confusing fuel price with the price of useful heat delivered.
- Promising the same recoverable share and temperature for every compressor.
Can heat also be used to heat water?
Yes, provided the temperature level, required demand and suitable circuit separation match. The source temperature must permit heat transfer; for example, water cannot be heated to 80 °C using 60 °C heat without an additional source.