Tutorial 2 – Heat pumps

Sympheny V1.1



This tutorial focuses on the modelling of heat pumps and will show you how to implement the following features in your energy model:

> Multiple temperature level heat demands

> Multi-input technologies through different representations of heat pumps/chillers

> Technology with multiple functions through the modelling of a reversible heat pump


The energy hub diagram will look like the following:


Step 0 – Getting started

The procedure here is the same as for Tutorial 1. You can name the project, Analysis and the scenario, Tutorial 2, Heat pump potential and General HPs respectively.


Step 1 - Hubs

The hub section allows you to create different energy hubs that will contain multiple energy conversion, storage and/or network technologies. This tutorial contains a single hub.

> Select Add New, name it (e.g. Neighbourhood) and press Add.


Step 2 – Energy carriers

> Select Next to move to the Energy Carriers Candidates section.

> Select Add New to define an energy carrier.

> Assign a Type, a Subtype, and a Name to each energy carrier that you create and Add it.

Find below the list of energy carriers used here.




Heating Energy



Heating Energy

Heat 70-80°C

Heat 70-80°C

Heating Energy

Heat 30-40°C

Heat 30-40°C

Heating Energy

Heat 10-20°C

Heat 10-20°C

Cooling Energy

Cooling 0-10°C

Cooling 0-10°C

Heating Energy

Heat Ambient

Heat Ambient

Electrical Energy




> Select Next to move to the Energy Demands section.


Step 3 – Energy Demands

> Press Add New to add an electricity or heat demand.

> Select the hub that requires the energy (only one hub here to choose from). Then select the energy carrier related to the demand and name this energy demand.

Here again the profiles will be chosen from the database.

> Press Generate Profile and select the following Demand Type – Building Use – Building Age combinations from the Database:

·        Cooling:  Cooling – Multi-family House – Minergie-Renovation

·        Heat 30°C-40°C: Space Heating – Multi-family House – Minergie-Renovation

·        Heat 70°C-80°C: Hot water – Multi-family House – Minergie-Renovation


> Give them an Energy Reference Area of 20’000 [m2] and select Next. This models the demand profiles for 200 multi-family housings with the hypothesis of 100 [m2] per housing.

The electricity demand of the hub is ignored. The electricity needed to make the heat pump work is determined by the optimization.

Finally, you will have the following energy demands modelled:

> Select Next to move to the Solar Resources section.


Step 4 – Solar resources

No solar resources are defined within this tutorial.


Step 5 – Import & Exports

Import Candidates are energy resources imported to the site.  This may include, for instance, electricity from the electricity grid, gas from a gas grid, heat from a thermal network, or wood pellets.  It also may include on-site energy resources like groundwater and geothermal heat, which are "imported" to the site from the ground. 

This tutorial uses two on-site imports: cold water from the Lake and ambient heat from outside (called Heat Ambient here).

1.      Lake as an import

> Select Add New to add the amount of water available from the lake.

> Select Import as the Type

> Select the energy carrier Lake and the energy hub created before. For simplicity, leave all boxes free.


2.      Heat Ambient as an on-site resource

> Repeat the procedure for the EC Heat Ambient.

Like in Tutorial 1, you will also need to import Electricity:

No exports are needed in this tutorial.


Step 6 – Supply Technologies

Heat pumps and heat exchangers are different types of conversion technologies. The following steps give more details on how to implement them.


Step 6.1 – Multi temperature levels and heat exchangers

As seen in step 0, the tutorial has 3 energy levels: cooling 0-10°C, heat 30-40°C and heat 70-80°C.  Since the heat is assumed to be dissipated and for the system to make better use of the energy, model the following virtual heat exchanger.

> Select Create Custom from the Conversion Technology Candidates Tab, fill in the boxes like given below. Don’t forget to tick the box Virtual Technology:


1.      Heat exchanger for HT -> MT


Furthermore, the cold water from the lake can directly be used to provide cooling. This is done by a heat exchanger.  However, as it is part of the water source heat pump, it will be implemented there as a separate mode.


Step 6.2 – General heat pump/chiller

The general model of a heat pump or a chiller is the same: it is a machine that transports heat from one place to another. In the case of a heat pump, the heat is brought to the target medium, while in case of a chiller, the heat is taken away from the selected medium (=cooling).   

The main difference of a chiller and a heat pump lies in the aim of their usage. The heat pumps’ goal is to provide heat while the chiller is there to provide cooling. However, since the technology is the same, a chiller will still have the LT heat as its input.


1.      Application of a heat pump

> Select Create Custom and fill in the boxes like in the following image:

Note that the heat pump to be modelled is an Air Source Heat Pump and will thus need ambient heat as an input. The cooling side of the heat pump is generally neglected. The diagram for this heat pump can be represented as such, whereas only the circled part of the heat pump is modelled:

Thus, the function has the following parameters:

> The output efficiency of as heat pump or chiller is defined based on the electricity input. Therefore, make sure that the primary EC’s box is ticked for the electricity. 


2.      Application of a chiller

In the case of a chiller, both sides are modelled. The diagram is the following:

It shows that even though the chiller takes Heat (LT) as an input, it produces cooling. At the same time, it does also produce heat, which can either be used or which needs to be rejected to the environment using cooling towers. The low temperature input of the heat pump heating side is neglected within the model.


> Select Create Custom and give the following parameters:

> The output efficiency of the heating side (in the case of a chiller, generally we talk about the waste heat that needs to be rejected to the ambient) is generally the output efficiency off the cooling side +1. Indeed, the electricity is also dissipated as it and is considered within the efficiency calculation.


Next to chillers working with electricity, you can also have an absorption chiller which works with uses heat (instead of electricity) to generate cooling.

> Select Create Custom and give the following parameters to model an absorption chiller:


Step 6.3 – Implementing a multi-input technology + technology with multiple functions

Reversible heat pumps have a cooling and a heating function.

Air source reversible heat pump

> Select Create Custom and give the heat pump the following characteristics:


The primary energy input is chosen to be electricity. Thus, the efficiency equals the COP that is assumed to be 4 (i.e. 400%).

> Select New Function to add the cooling function with the parameters:

> Finally give the heat pump the following costs characteristics:


Water source reversible heat pump (lake water)

A second reversible heat pump is modelled. This one is water source heat pump based on lake water. As already mentioned, the cold water from the lake can directly be used to provide cooling. This is done by a heat exchanger, which is modelled here as a third mode.

> Select Create Custom and give the heat pump the following characteristics:

> Fill in the first technology mode with the following characteristics:

The primary energy input must be electricity. Thus, the efficiency equals the COP that is assumed to be 5 (i.e. 500%).

> Select New Mode to add the cooling mode with the parameters:

> Select New Mode to add last mode, the free cooling, with the following characteristics:

In this case, the mode models free cooling is, meaning the heat pump is not operating, and the mode only represents a heat exchanger. This heat exchanger models the exchange with the lake water and the primary input must be the lake. The 5% electricity input is only used for the pumps. The seasonal operation is selected to ‘operation only in non-summer’ to consider that, in summer, the lake water temperature is too high for direct cooling and has to be chilled through the heat pump.

> Finally give the heat pump the following costs characteristics and press save:


Step 7 – Network Technologies and Links

This tutorial has only one hub and don’t need any links. See Tutorial 3 for an example with multiple hubs.

> Select Next to move to Other.


Step 8 – Other

This section allows to include the current interest rate in [%] to the model. Set it to 2%.


Step 9 – Review

Look at the review section to have an overview over the entire scenario specification and edit a section if needed.

> Select Finish Specification & Prepare for Execution to get to the execution of the model.


Step 10 – Execution & Results

Next to the Setup section you can find the Execution section where you select the scenario to be optimized, the two objectives the optimization should be based on and finally the number of points wanted in the pareto front.

> Select the scenarios for which you want to execute the analysis (otherwise the execute button will stay grey and cannot be selected) 

> Select Execute to start the optimization.

> Once you receive an email that the optimization is completed, Go to the Results section and Select Download to go through the results of the optimization.

> Click on View results to open the dashboard of your optimal design