Skip to content

Decommissioning & retrofit logic

This note explains how PyPSA‑SPICE handles plant capacity that reaches the end of its technical lifetime while you still want to allow the model to keep operating the plant by paying for a retrofit. To represent this, each plant can be split into two paired assets:

  • Normal asset (e.g., XY_SO_COAL) — the existing fleet/capacity
  • Retrofit asset (e.g., XY_SO_COAL_RETRO) — the portion that can be continued through retrofit investment

Note

Key assumption: retrofit asset is treated as an upgrade of the existing capacity, so it pays only the retrofit CAPEX rather than the full greenfield cost of constructing a new plant.

Logic overview

  • Base year (2025): capacity that is already over-lifetime is shifted from the normal asset to the retrofit asset (treated as retrofitted, not decommissioned).

  • Future year (e.g., 2030): capacity that becomes over-lifetime is written to decomission_capacity.csv. Hence, substations can decommission it from the normal fleet; the same amount becomes the maximum retrofit investment option via retro.p_nom_max_2030.

%%{init: {"theme":"base","themeVariables":{"fontSize":"11px", "htmlLabels": true}}}%%
flowchart TB
A[["<div style='text-align:left; margin:0'><u>Inputs</u>
- normal p_nom
- commissioning year + lifetime
- base year 2025
- future year(s) e.g. 2030</div>"]] --> B{"End of lifetime in 2025?"}

B -- Yes --> C["MW_over_2025"]
C --> D["normal.p_nom -= MW_over_2025"]
C --> E["retro.p_nom  += MW_over_2025
(assume retrofit, not decommission)"]

B -- No --> F{"End of lifetime in 2030?"}
D --> F
E --> F

F -- Yes --> G["MW_over_2030"]
G --> H["<div style='text-align:left; margin:0'><u>Write decomission_capacity.csv</u>
(node, normal_asset, 2030, MW_over_2030)
→ substation can decommission from normal fleet</div>"]
G --> I["<div style='text-align:left; margin:0'><u>Set retrofit option</u>
retro.p_nom_max_2030 = MW_over_2030
→ model may invest (pay retrofit CAPEX)</div>"]

F -- No --> J["No decommision/retrofit done"]

H --> K[["<div style='text-align:left; margin:0'><u>Outputs</u>
- updated p_nom (2025 normal & retro)
- decomission_capacity.csv (future retirements)
- retrofit cap p_nom_max_year</div>"]]

I --> K
J --> K

N{{"<div style='text-align:left; margin:0'><u>Assumptions</u>
- normal vs retrofit assets
- retrofit assets pay retrofit CAPEX only
- 2025: shift MW to p_nom in retrofit assets
- 2030: decommissionable, but optional retrofit</div>"}} -.-> A