I can solve the problem with some metaheuristic method (e.g. genetic algorithm or simulated annealing). They can help avoiding local optima. I'll solve it in Python even if it is formulated in Excel.
Relevant Skills and Experience
PhD in optimization (of energy supply systems) using various methods. Good knowledge of Python and Excel and their optimization tools.
Proposed Milestones
$160 USD - Solving the optimization problem.
Additional Services Offered
$200 USD - Consulting related to applied optimization.
Since your problem is non-convex, integer and relatively large, I suggest attempting to use metaheuristic methods. They **don't guarantee** obtaining global optima, but in practice they usually find either the **optimal solution or some good near-optimal solution**. After such solution is obtained one might try to further improve it with local search. There are several more tricks. These methods are very popular in both scientific and practical applications. Additionally, they let us be more flexible when formulating problems and choosing optimization tools.
Whether the problem is formulated in Excel or Python, I'd solve it with the Python solver. If it is in Excel, I can also try solving it inside Excel, without additional apps (this depends on the problem, Excel version, etc.).
Please, have in mind that I'm not going to use Python 2 (since I'm not comfortable with it), only Python 3!