include an option to use only dispatch optimization (with fixed capacities)

[nehadimri1991]

At present, this would need to be hard coded every time it is needed (should be parameterized)

[xavijoba]

to fix the capacities, could we not fix upper and lower bounds to the same value (or very close) ?

[nehadimri1991]

Fixing capacities directly in the excel file doesn't solve this. The parameter 'nonconvex' needs to be set 'False' for each transformer/storage and the 'offset' parameter (which points to the base investment cost) should not be given in this case. When 'nonconvex' is set to False, 'offset' should be 0, otherwise this leads to an error.