fix: expressions returning zero for non-extendable generators #1451
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The curtailment(), capacity(), and capex() methods in the optimization expressions module now correctly handle networks with only non-extendable generators. Previously, these methods raised KeyError when accessing optimization variables that don't exist for fixed capacities. Uses comp.fixed property and comp._operational_attrs for cleaner code. Closes #1316
FabianHofmann
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Irieo
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Dec 1, 2025
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@FabianHofmann This works. I tried cases with mixed capacity (ext & non-est), things like max_hours for storage units. Don't see any issues but for an xarray warning which I mention above.
lkstrp
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Dec 2, 2025
pypsa/optimization/expressions.py
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| query = f"~{nominal_attrs[c]}_extendable" | ||
| capacity = capacity + n.c[c].static.query(query)["p_nom"] | ||
| costs = n.c[c].static[cost_attribute][capacity.indexes["name"]] | ||
| comp = n.c[c] |
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The internal convention we started is c for pypsa.Component and component as parameter name to pass any string or pypsa.Component. I think we can just also rename c: str here since this is internal. I will just adjust
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sure thing, I'll do that
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Summary
Fix
curtailment(),capacity(), andcapex()expressions returning zero for networks with only non-extendable generators.Closes #1316
Root Cause
The methods accessed optimization model variables directly (
n.model.variables[f"{c}-{attr}"]). For non-extendable generators, this variable doesn't exist since there's nothing to optimize. The@pass_none_if_keyerrordecorator caught the KeyError and returned None, resulting in zero expressions.Solution
LinearExpressionfor non-extendable components when the variable doesn't existcomp.fixedproperty andcomp._operational_attrs["nom"]for cleaner, more idiomatic codenominal_attrsimportTest Plan