Hello everyone

I am trying to model a small island system that contains PV, Wind and Battery storage as investment candidates. I have also set up a Diesel generator using the OffsetConverter to account for the non static efficiency. But this introduces the NonConvexity and turns the problem to an MILP. I have tried solving the model with Gurobi but even for a small system like mine it cant find a solution for a one year optimization (takes 2-3 days and then my laptop runs out of memory).

Do you have any suggestions on how to avoid this issue? I thought about using the PiecewiseLinearConverter but I am not sure if it will solve this issue if i try to capture the efficiency curve using a function. I am also not sure if I can implement a min_load for the generator either (meaning that I dont want it to operate below 50% capacity if it needs to operate)

Any help/suggestions would be appreciated

**PS: Here is the Offset converter definition and the model size from Gurobi**

Optimize a model with 113889 rows, 105131 columns and 293519 nonzeros

Model fingerprint: 0x7900b732

Variable types: 96371 continuous, 8760 integer (8760 binary)

Coefficient statistics:

Matrix range [1e-03, 1e+03]

Objective range [1e-01, 1e+05]

Bounds range [1e+00, 1e+05]

RHS range [7e-01, 4e+00]

Presolve removed 43811 rows and 52569 columns

Presolve time: 1.03s

Presolved: 70078 rows, 52562 columns, 188377 nonzeros

Variable types: 43802 continuous, 8760 integer (8760 binary)

Deterministic concurrent LP optimizer: primal and dual simplex

Showing primal log only…

```
elif diesel_gen_type ==2:
min_load = 0.5
max_load = 1.0
min_efficiency = 0.299
max_efficiency = 0.3698
c1 = (max_load / max_efficiency - min_load / min_efficiency) / (
max_load - min_load
)
c0 = min_load * (1 / min_efficiency - c1)
diesel_generator = solph.components.OffsetConverter(
label = 'diesel_generator',
inputs = {bus_diesel: solph.flows.Flow()},
outputs= {
bus_electricity: solph.flows.Flow(
min=min_load,
max=max_load,
nominal_value=1200, variable_costs= 50,
nonconvex = solph.NonConvex(),
),
},
coefficients=(c0, c1),
)
```