Updating the documenation around the heat pump

## Direct heat with industrial Heat Pump

 Below is a schematic representation of the direct heat production with an industrial heat pump system, 

 which effectively allows to increase outlet temperature for a district heating network, 

 relative to the geothermal source production temperature

 which effectively allows the system to increase outlet temperature for a district heating network, 

 relative to the geothermal source production temperature.

### Determining the Injection Temperature

![Figure description](../../images/cartoon_heatpump.png)

*Figure 2: a schematic representation of the system.

On the left is the primary circuit of geothermal brine with temperature Tprod, 

assumed equal to the aquifer temperature Taq. 

The temperature is first lowered by amount ΔT1 in the heat exchanger. 

Next, the temperature is lowered by amount ΔT2 in the heat pump to the injection temperature Tinj. 

On the right hand side is the district heating network. 

The cool water returning from the network at temperature Tdh_out is first heated in the heat exchanger 

to Tdh_out + ΔT1, and then by the heatpump to the heat network inlet temperature Tdh_in.

It is assumed that condenser and evaporator temperatures of the heatpump are respectively 3°C lower and higher 

than the source and outlet temperature of the heat pump*

On the left is the primary circuit of geothermal brine while on the right is the circuit of the district-heating system.

The model has four elements:

1. A Geothermal system, Tprod is the temperature of the water produced from the reservoir, while Tinj is the temperature of the water pumped back into the aquifer.

2. A District heating system, Tdh_out is the water that comes _from_ the district heating system, while Tdh_in is the water that goes _to_ the district heating system

3. A Heat Exchanger, which transfers heat from the production water of the Geothermal system to the district-heating system.

4. A Heat Pump, which consumes grid electricity to further heat up the district-heating water and cool the geothermal system water. 

When modelling the system:

1. The production temperature, Tprod, is assumed equal to the temperature of the reservoir.

2. The district heating return temperature, Tdh_out, is known (set by the user, default: 35°C)

2. The district heating input temperature, Tdh_in, is known (set by the user, default: 70°C)

This leaves the Injection temperature Tinj, as the remaining unknown.

This is calculated using the equation:

Tinj = Tprod - ΔT1 - ΔT2

where:

ΔT1 = Tprod - Tdh_in, must be between 0 -> ΔTmax (user specified)

ΔT2 = Tdh_in - (Tdh_out + ΔT1)

### Two simple examples

Using the following input: Tprod = 60°C, Tdh_in = 70°C, Tdh_out = 35°C

It is clear that the production temperature of the aquifer is not hot enough to fully supply the district-heating system.

First, the district heating system is heated by:

ΔT1 = Tprod - Tdh_in, 60 - 70 = -10°C. This is below 0°C so ΔT1 = 0°C.

ΔT2 = Tdh_in - (Tdh_out + ΔT1) = Tdh_in - Tdh_out = 35°C

Tinj = 60 - ΔT1 - ΔT2 = 25°C

### Calculating the Coefficient of Performance (COP)

The COP of the heat pump is given by the following equation:

For direct heat it does not include added heat in the heatpump from the compressor.

The reason not to include this is to account for geothermal energy only. This setting can be changed by setting

### Default values

Proposed parameters are the following:

Proposed default parameters are the following:

| parameter                                                              | symbol         | value  | unit     |

|------------------------------------------------------------------------|----------------|--------|----------|

| use heat pump                                                          | HPuse          | True   | bool     |

| HP application target temperature is Tdh_in                            | HPapp          | True   | bool     |

| target district heat outlet temperature                                | Tdh_in         | 80     | °C       |

| minimum aquifer production temperature                                 | Tminprod       | 40     | °C       |

| maximum cooling temperature for reinjection relative to reservoir (ΔT) | ΔTmax          | 40-200 | °C       |

  timestamp: 1740946648058

- pypi: ./

  name: pythermogis

  version: 1.2.4

  sha256: 4406d3c4da3a9e6ee46a39b7ce7b61063e676db495638f1f9d992ac174589913

  version: 1.2.5

  sha256: f7faf166eaa5141f37e7e96c2fc7f2c01cf26da4be5fc5164aa0c8c784614e2b

  requires_dist:

  - jpype1>=1.5.2,<2

  - xarray==2024.9.0.*

        self.assertTrue(np.isclose(10.401010755009017, results.utc(), 0.001))

        self.assertTrue(np.isclose(16.50359210062243, results.capex(), 0.001))

    @pytest.mark.skip("This test requires a fix in the java core. ignore until fix is pushed")

    # @pytest.mark.skip("This test requires a fix in the java core. ignore until fix is pushed")

    def test_calculateDoubletPerformance_directheatHP_App(self):

        """

        This is a copy of a test from the Java ThermoGisDoubletTest.java script; to validate that this python implementation of the ThermoGIS Doublet