← Back to CHP waste heat
CHP WASTE HEAT · TECHNICAL ARTICLE

Heat pumps: raising the temperature of CHP waste heat

Part of a CHP unit's heat output may be steady but too cool for a particular customer. An industrial heat pump addresses this mismatch: it takes heat at a lower temperature, uses electricity and supplies a greater quantity of heat at a higher temperature.

6 min readSources are listed at the end of the article
Isometric illustration of a CHP engine connected to an industrial heat pump by a blue heat circuit and to a process facility by an orange circuit
A heat pump connects a lower-temperature source to an industrial user requiring a higher temperature.

A heat pump does not create heat from nothing. It draws existing heat from cooling water, a return circuit or another low-temperature source and uses a compressor to raise its temperature. It is therefore relevant where sufficient heat is available but is not hot enough.

A typical biogas plant case

A CHP unit has a hot-water stream left unused after meeting its own heating needs. A nearby industrial facility requires higher temperatures for washing, drying, evaporation or steam. Instead of rejecting the CHP heat, the plant supplies it to a heat pump, whose electric compressor raises the temperature to meet process requirements.

What determines electricity consumption?

As a rule, the smaller the difference between source and required output temperatures, the more favourably a heat pump operates. The first step is therefore to find the warmest available source and the lowest temperature the process genuinely needs. It may be worthwhile to reduce process temperature requirements before sizing the heat pump.

The boiler need not be replaced entirely

A hybrid arrangement is often more economical: the heat pump covers base heat demand, while the existing boiler remains for peaks, production start-up and backup. The heat pump can then be sized for many operating hours rather than an infrequent peak load.

Examples of current technology

  • GEA develops industrial high-temperature heat pumps; the Tiense Suiker project illustrates the use of industrial waste heat to reach approximately 135–160 °C.
  • MAN Energy Solutions offers large industrial heat pumps for process heat and district heating, using lower-temperature waste heat to produce hot water or steam.
  • Turboden also develops large heat-pump systems for industrial and district heat alongside ORC technology.

What needs checking on site?

  • temperature and flow of the available source throughout the year
  • required supply temperature and process return temperature
  • electricity price and availability
  • annual operating hours and load variation
  • potential to use the system's cold side at the same time
  • space, noise and integration with existing boilers

Where cooling is needed at the same time, some projects can gain an additional benefit by using both the useful cold and hot sides of the same heat pump.

Key pointA heat pump does more than compete with a boiler. It can make lower-temperature CHP heat useful to a process requiring a higher temperature.

Sources and further reading

This article is for information. An actual installation requires a heat balance, equipment manufacturer data and checks of local conditions, permits and applicable regulations. The illustration shows a functional concept, not a detailed engineering design.