Optimal network topology and alignment design for minimizing construction costs of wind farm access roads

Designing road networks for wind farms in complex terrain is a challenging task, especially under tight construction budgets. Traditional manual methods are time-consuming and may yield suboptimal results. A new structured three-phase optimization framework named TriPhase is proposed to automate and minimize road construction costs from corridor selection to earthwork. Phase one formulates corridor selection as a Steiner minimum tree problem over a terrain-aware graph, incorporating slope and curvature constraints. In phase two, each road segment undergoes horizontal alignment optimization using a bilevel model, where a mixed-integer linear program evaluates vertical alignment costs. To ensure solver compatibility and performance, the model is reformulated explicitly for Gurobi. The final phase applies a network-wide convex optimization model to refine vertical alignment and earthwork costs. Numerical experiments on real-world sites demonstrate up to 14% cost savings compared to previously developed manual designs, validating the framework’s effectiveness and practical relevance.