Heat losses disappear in sankey when supply of residual heat exceeds a certain value

[claudiavalkenier]

Context

While I was setting up the supply of HT heat sources in a scenario, I noticed the following in the Sankey:

When residual heat is set to 50 TJ (and deep geothermal set to 20 MW), the Sankey shows heat losses flowing out of heat. However, when I increase the residual heat to 60 TJ, these losses disappear. (see screenshots)

This suggests that something may not be working properly at the node energy_heat_network_storage_ht_steam_hot_water. At 50 TJ, the energy_distribution_ht_steam_hot_water still shows 112.6 MJ, whereas in the 60 TJ case it shows 0 TJ. This difference appears to be related to the disappearance of the losses.

Steps to reproduce

• Open https://energytransitionmodel.com/scenarios/1427474 and the sankey
• Go to Supply > HT district heating
• Set geothermal (deep) to 20 MW
• Set residual heat to and 50 TJ and then to 60 TJ

Tagging @kaskranenburgQ here since we've discussed this issue!

[kaskranenburgQ]

Inspected this issue together with @claudiavalkenier.
Found the following:

• Problem arises in the query conversion_loss_steam_hot_water_to_steam_hot_water, more specifically this part of the query:
  V( FILTER(G(sankey_conversion_group),"steam_hot_water_output_conversion > 0.0 && steam_hot_water_input_conversion > 0.0"), "**steam_hot_water_output_conversion** * steam_hot_water_input_conversion / (1 - loss_output_conversion) * output_of_loss" )

When the residual heat input is set to 50 TJ, a small amount of energy is still necessary from the storage to account for the peaks in the heat demand.

Therefore the steam_hot_water_output_conversion for the node energy_heat_network_storage_ht_steam_hot_water is a positive number and the query conversion_loss_steam_hot_water_to_steam_hot_water calculates the storage surplus as losses.

When the residual heat input is set to 60 TJ, no heat is necessary from the storage to serve the peak. Therefore the steam_hot_water_output_conversion for the node energy_heat_network_storage_ht_steam_hot_water is 0.0, and the query conversion_loss_steam_hot_water_to_steam_hot_water does not calculate the storage surplus as losses.

This is the gap in the outcomes that we see.

This is part of a bigger discussion on whether we should view the storage surplus at the end of the year as losses or not. Notifying @mabijkerk because of this.

[mabijkerk]

So you're saying that the unused heat is not taken into account in the loss query? I would say that, yes, the unused heat should be taken into account as: it is wasted losses.

We should also check how this shows up for the hydrogen storage.

[kaskranenburgQ]

So you're saying that the unused heat is not taken into account in the loss query? I would say that, yes, the unused heat should be taken into account as: it is wasted losses.

Not always, it's only ignored when 100% the heat that is stored is not used at any given time.
So, when just 0.001% of the stored heat is used at some point, the losses will be accounted for correctly.