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I want to build a system which consists of solar thermal collectors and ground source heat exchanger. I have a whole season weather data, which is connected with solar thermal collectors. I want to see how much heat will be released during the whole season from solar collectors to the ground by ground source heat exchanger respectively borehole, and the increased ground temperature by heat release.

Although I have the same number of unknowns and equations, the singularity error comes up.

Is there any missing process element?

Screenshot of model

Markus A.
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Orhun C.
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1 Answers1

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The thermo-hydraulic part of your model needs a "ground" component to provide the reference pressure and enthalpy, since the heat exchanger components only describe changes in pressure/enthalpy.

You could use, e.g., a Modelica.Fluid.Sources.Boundary_pT, Modelica.Fluid.Sources.Boundary_ph or Buildings.Fluid.Storage.ExpansionVessel component for that.

Rene Just Nielsen
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  • Hi Rene, Thanks for the reply. As you mentioned, I used in Model additionally `Modelica.Fluid.Sources.Boundary_ph` element. The simulation works, however the temperature of solar collectors i suppose in summer exceeds the allowable maximum temperature which corrosponds 130 Celcius. I want to release these excessive heat to the ground and find out how much the ground temperature increases resp. how much heat will be released to the ground. Would not make more sense to use `Modelica.Fluid.Sources.Boundary_pT` in order to look at the changing of ground temperature during the whole year. – Orhun C. Aug 08 '22 at 14:49
  • Yes, a `Boundary_pT` would work as well. However, it won't solve the heat dissipation problem in a "good" way. Eventually, the irradiated energy will heat up the closed system beyond the limits of the (assumed) liquid water medium model, unless you remove the heat. The borehole model should do this, pressumably through a `HeatPort` – Rene Just Nielsen Aug 09 '22 at 06:35
  • I am agree with you that solving the heat dissipation problem would be easier with a heat port. However, `BoreHole` model does not have a heat port. I would like to set up the system so that when the solar thermal collectors reach the maximum temperature, release the heat into the ground. – Orhun C. Aug 09 '22 at 11:58
  • Perhaps you could use some of the borehole models in `Buildings.Fluid.Geothermal.BoreFields`. For instance `Buildings.Fluid.Geothermal.BoreFields.BaseClasses.Boreholes.OneUTube` which (among others) has a heat port. – Rene Just Nielsen Aug 09 '22 at 13:24