Disabling spillage variable for storage units

[Georgios Mavromatidis]

Dear PyPSA community,

We are working with a model based on PyPSA-Eur data and for some analysis we are performing, we are interested in disabling the possibility of spillage from hydro plants.

Is there an easy option for us to do that without needing to fully remove it from the model's formulation? Something like "fixing" it to 0 for all time steps?

Any pointers? Thanks!

P.S. I am aware that this might lead to feasibility issues in case the storage fills up and there is inflow but no demand to use the stored energy, but we can deal with that :)

[Fabian Neumann]

Hi Georgios,

I don't think there's an option for disabling spillage when defining
storage unit components.

I think the easiest would be to write an extra_functionality where the
spillage variables are forced to 0.

Best wishes,

Fabian N

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[Georgios Mavromatidis]

Thank you, Fabian.

That sounds like a good approach - will try it then and write the approach here to anyone needing it for future reference.

Best,

Georgios

[Tom Brown]

Hi Georgios,

Alternatively you could build the hydro with stores, generators and
links instead, then exclude the spillage. For this you could use this
code, which automatically builds storage units from lower components:

https://github.com/PyPSA/PyPSA/blob/master/examples/sector-coupling/replace-generator-storage-units-with-store.py

Best wishes,

Tom

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> --
> Dr.-Ing.
> Fabian Neumann (he/him)
> Postdoctoral Researcher
>
> Department of Digital Transformation in Energy Systems
> Institute of Energy Technology
> Technische Universität Berlin
>
> Group website: https://tub-ensys.github.io
> <https://tub-ensys.github.io>

> Personal website: https://neumann.fyi <https://neumann.fyi>

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Professor of Digital Transformation in Energy Systems

Institute of Energy Technology
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[Georgios Mavromatidis]

Thank you, Tom. That is indeed useful.

In the meantime, I was able to have the results that I want with the "extra_functionality" approach, as follows:

def extra_functionality(n, snapshots):

    vars_soc = get_var(n, "StorageUnit", "spill")    

    lhs = linexpr((1, vars_soc))    

    define_constraints(n, lhs, "=", 0, "StorageUnit", "spill_zero")

network.lopf(solver_name="gurobi",pyomo=False, extra_functionality=extra_functionality)

Thank you both for your help!

[Franco Ferrucci]

Hi there,

With the new linopy interface, you could do this:

m = n.optimize.create_model()
hydro_spill = m.variables['StorageUnit-spill']
hydro_spill_total = hydro_spill.sum()
constraint_expression = hydro_spill_total == 0
m.add_constraints(constraint_expression, name="StorageUnit-no_spill")
result_status = n.optimize.solve_model()

(in this case, all StorageUnits are hydro power)

[Franco Ferrucci]

Hi again,

Sometimes it is too restrictive to force spillage to zero. Instead, you could add a cost to the spilled power by changing the objective function:

m = n.optimize.create_model()
hydro_spill = m.variables['StorageUnit-spill']

# Modify objective function:
m.objective = m.objective + hydro_spill * 0.01

In this case, 0.01 is the marginal cost of spilled power.

Cheers,

Franco