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Wastewater Heat Pump

The amount of wastewater created by the system can directly be retrieved from the amount of DHW required and then be used as the low temperature source for a heat pump.

Figure 43 System diagram of a heat pump operating of wastewater


Set-up summary




Supply technologies


Energy Carriers

Energy Demands


Water-water HP 1

Water-water HP 2

Air-water HP

Virtual technology




Primary Input

Primary Input

Primary Input









Heat ambient







Heat 30-40°C



(primary) output

(primary) output



Heat 70-80°C





(primary) output

(primary) input

Heat 70-80°C forward






Primary output









Set-up Implementation

Figure 44 Set-up Implementation for a heat pump operating on wastewater


For correctly modelling the wastewater, three energy carriers must be defined (names are up to the users):


  • Hot water (as the output of the technologies)

  • Hot water forward (as the demand)

  • Hot water return (the wastewater)


Figure 45 Creation of needed energy carriers for a heat pump operating on waste water


A virtual technology will then create one unit of hot water forward and hot water return for each unit of hot water produced.


Figure 46 Modelling of wastewater as a virtual supply technology

It is necessary to add an export of wastewater, to assure that the energy balance can be solved, when DHW is to be produced but there is not heating demand that requires wastewater to be used.


Figure 47 Necessary exports to balance the energy for a wastewater heat pump


In a similar reflexion, there need to be a technology allowing to create heating, which is not based on wastewater (for cases where no wastewater is available). In this case, the heat pump is considered to have a second mode, working on an alternative anergy source.


Figure 48 Use of a new mode to use as an alternative source for heating

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