Hello all,

An issue concerning the Panda Excel Reader / how tables communicate blank cells:

If you use the Panda Excel Reader and don’t fill every value of the parsed table, the equivalent for the cell is NaN (None Type of tables in that case). Issue: For the storage class you Need None to enable the correct working of constraints.

Example:

```
for i, s in storages.iterrows():
if s['Investment'] == 1 :
noded[i] = solph.components.GenericStorage(
label=i,
inputs={noded[s['bus']]: solph.Flow(variable_costs=s['variable_costs'],
investment = solph.Investment(ep_costs=economics.annuity(capex=s['capex_pump'], n=s['calendaric_lifetime'],wacc=s['wacc'])), max=s['max_power'])},
outputs={noded[s['bus_to']]: solph.Flow(variable_costs=s['variable_costs'],
investment = solph.Investment(ep_costs=economics.annuity(capex=s['capex_turbine'], n=s['calendaric_lifetime'],wacc=s['wacc'])), max=s['max_power'])},
capacity_loss=s['capacity_loss'],
initial_capacity=s['initial_capacity'],
capacity_max=s['max_capacity'],
capacity_min=s['min_capacity'],
inflow_conversion_factor=s['efficiency_pump'],
outflow_conversion_factor=s['efficiency_turbine'],
nominal_input_capacity_ratio = s['input_capacity_ratio'],
nominal_output_capacity_ratio = s['output_capacity_ratio'],
investment = solph.Investment(ep_costs=economics.annuity(
capex=s['capex_capacity'], n=s['calendaric_lifetime'],wacc=s['wacc'])),
)
```

In that case the Excel is blank and Returns the value NaN for the attribute `nominal_input_capacity_ratio`

, which will then give NaN into the construcotr of the storageInvestmentclass. Since for oemof NaN is not None (even though it means the same) the constraint is not issued correctly.

@uwe.krien ; I would like to hear your advice / ideas.

My ideas are all a Little “clumsy”.

- Set the values to 0 in the Excel and tell oemof to behave the same as with None.
- Also pass a NaN value to the constructor which then has to be compared for every Attribute

All is kinda messy and requires many if’s. It would be easier if you could Change every NaN value to None.