Creating an Energy Flow Diagram: Heat Pump, Photovoltaic System and More
The energy flow diagram in Polysun — also known as a Sankey diagram — visualizes a system’s energy balance in a clear graphical representation. The width of the arrows directly indicates the size of the respective energy flow. This makes it possible to transparently trace energy input, distribution, and losses, and quickly identify optimization potential.
Energy Flow Diagram: Layout, Structure and Color Coding
The energy flow diagram is accessed via the menu Results → Energy flow diagram.
Structure of the Diagram
The diagram is arranged from left to right:
- Left: Energy sources (environmental energy, fuels, electricity from the grid)
- Middle: Generators and converters (heat pump, boiler, CHP unit, solar collectors)
- Right: Consumers (space heating, hot water) and losses
The arrow width corresponds to the amount of energy transported — wider arrows mean larger energy flows.
Color Coding
| Color | Type of energy |
|---|---|
| Blue | Cooling energy |
| Red | Heating energy |
| Yellow | Electrical energy |
| Green | Environmental energy (geothermal, solar, outdoor air) |
| Copper | Combustion energy |
| Gray | Losses |
| Purple | Various energies |
Creating an Energy Flow Diagram for Cascaded Heat Pumps
For systems with cascaded heat generators — such as booster heat pumps or multi-stage systems — Polysun detects this automatically. When creating the energy flow diagram, a dialog window opens to define the cascade layout.
Heat Pump Cascade Dialog: Defining Stages
If the wrong selection was made, or if you want to make subsequent adjustments to the visualization, the dialog for defining the cascade layout can be reopened at any time. To do so, click the “Change cascade layout” button in the bottom right of the energy flow diagram.
Identifying Deficits in the System
The energy flow diagram clearly highlights system deficits with a cross-text. This indicates when the system is unable to supply the required energy.
In addition, the diagram shows the proportion in which each heat generator contributes to covering the energy demand — making it easy to identify optimization potential and inefficient components at a glance.
FAQ
Can I use the energy flow diagram to compare different system concepts?
Yes. Polysun creates a separate energy flow diagram for each system variant. This allows different generator configurations to be visually compared and evaluated on a well-founded basis
Are complex hybrid systems also displayed correctly?
Yes. Polysun automatically detects cascaded systems — such as booster heat pumps or multivalent systems with a CHP unit, heat pump, and peak-load boiler — and displays the energy flows correctly.
How does the energy flow diagram help with system sizing?
The diagram shows at a glance the coverage share provided by each heat generator. This makes it easy to check whether the sizing of the heat pump or boiler matches the heat consumption, and how much of the heat demand is covered by which heat generator.