Best practices

Separate energy carriers

Imagine a system where a heat pump is used to produce heat for both heating and hot water. One may be tempted to use heat as corresponding energy carrier for both purposes. However, this is not recommended. Instead, one could use heating and hotwater as energy carriers (or any other naming, as long as it creates a distinction).

Why?

  1. Clarity: It is easier to understand the system when energy carriers are clearly separated.

  2. Flexibility: It is easier to change the system later on. For example, if one wants to replace the heat pump with a gas boiler - but just for hot water - it is easier to do so when the energy carriers are separated.

  3. Consistency: It is easier to compare different systems when the energy carriers are consistently named.

  4. Error prevention: It is less likely to make mistakes when the energy carriers are clearly separated. Mistkenly connecting two Nodes with heat, that in reality could not be connected since they are part of two different systems, cannot happen when the energy carriers are separated.

  5. Plotting: It is easier to plot the system when the energy carriers are separated. For example, one can plot the heat demand for heating and hot water separately, or immediately see how much energy is being spent to supply the different demands.

These are just a few reasons why it is recommended to separate energy carriers. Different systems may have different requirements, so it is up to the user to decide how to name the energy carriers. However, it is recommended to keep the energy carriers as separate as reasonable.

Definition: Energy carrier

According to ISO 13600, an energy carrier is either a substance or a phenomenon that can be used to produce mechanical work or heat or to operate chemical or physical processes.

This may be seen as motivation why, in this case, the argument “both are heat” may not be valid: In the end, the actual “carrier” is most likely water, and not heat (even if that is most commonly used as “carrier”). However, no one would argue to actually use water in this example, which shows that the choice of heat would already be “not 100% exact”; therefore, the separation into different two carriers does not “mis-represent” reality, but instead just makes our “abstraction” (= not using water as carrier) more explicit.