save extra_functionality in pypsa network

[lisazeyen]

saving the extra functionality in the pypsa network (maybe as a string?)

Describe the feature you'd like to see

Please give a clear and concise description and provide context why the feature would be useful. Also, we'd appreciate any implementation ideas and references you already have.

[FabianHofmann]

The idea is nice, but storing the extra functionality itself as a string is a bit tricky -> consider the case when the code syntax changes a bit, then the function strings do not work anymore. Debugging this could be very annoying.

I'd rather propose that with the linopy integration we store the solving model itself together with the network in a nc file. It would 'only' require adding the model netcdf writing into nc importer/exporter of pypsa (with a optional flag of course). It might bloat the nc file a bit, but it would be very clean. What do you think?

[fneum]

That sound nice! Could become large, but I wouldn't mind if it brings the convenience and is optional.

[fneum]

Just thought about it again. Sketch of the alternative solution:

n.extra_functionality = """
    def extra_functionality(n, sns):
        discharger_bool = n.links.index.str.contains("battery discharger")
        charger_bool = n.links.index.str.contains("battery charger")
        dischargers_ext= n.links[discharger_bool].query("p_nom_extendable").index
        chargers_ext= n.links[charger_bool].query("p_nom_extendable").index
        eff = n.links.efficiency[dischargers_ext].values
        lhs = n.model["Link-p_nom"].loc[chargers_ext] - n.model["Link-p_nom"].loc[dischargers_ext] * eff
        n.model.add_constraints(lhs == 0, name="Link-charger_ratio")
    """

# somewhere in n.lopf / n.optimize
if hasattr(n, "extra_functionality"):
    exec(n.extra_functionality)

[fneum]

I think in any case it makes sense to store the code of the extra_functionality -- even if it is not re-executed -- for model documentation.