Using electrical Storage even there is no Storage

Hey community,

I was modelling an energysystem with oemof.solph. For the model I used a electrical storage to see if it is economical to use that storage.
While the scalaroutput tells me, that there is no storagecapacity needed the sequences section tells me, that there is energy charged and discharged at the same timestep. So it uses the storage and subtracts the energy loss in the storage, but the storage never has been used.
the implementation of the storage looks like following:

estorage = solph.components.GenericStorage(
            label = "estorage",
            inputs = { e_bus: solph.Flow() },
            outputs = { e_bus: solph.Flow() },
            loss_rate = 0.007,
            # invest_relation_input_capacity
            initial_storage_level = None,
            inflow_conversion_factor = 1,
            outflow_conversion_factor = 0.9,
                ep_costs = epc_estorage,
                nonconvex = True,
                maximum = 10000,
                offset = 500
            ) )

It would be really nice if someone could tell me why that is and if there is any way that oemof charging a not existing storage.

Hi @hossi,

for me, it looks like your energy system profits from wasting energy (or has excess electricity that cannot go anywhere). Does the optimisation solve without the storage? If not, you might either add an explicit excess sink or implement your (probably renewable) source using the maxkeyword instead of fix. Also for testing, you give a minimal cost to the inflow (or outflow).

Thank you for the fast reply. I implemented an excess for eletricity, but it does not carry any value for the flow electricity to excess. It might be, because the system just generates as much as the demand needs. As far as I understood the “maxkeyword”, I can not use it because I want to test how much kWp is necessary as well.
Do you mean, that I have to set a minimal cost for one of the flows by your last point? Or do you just suggest it for testing?

Thank you in advance!

If you have a ‘fix‘ source plus an excess sink, it does not mean that no other way will be used to get rid of excess energy. Maybe, it’s easiest if you post a full energy system that shows the described behavior.

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