Near-Optimal Solutions in an Open Model of a Renewable European Power System

Abstract:

Models for long-term investment planning of the power system typically return a single optimal solution per set of cost assumptions. However, typically there are many near-optimal alternatives that stand out due to other attractive properties like social acceptance, regional equity and energy autonomy. Understanding features that persist across many cost-efficient alternatives can enhance policy advice and acknowledges structural model uncertainties. We systematically explore the near-optimal feasible space of a completely renewable European electricity system model. While accounting for complex weather patterns through high spatial (200 nodes) and temporal resolution (hourly for a full year) and the installable potentials of renewable resources, we allow simultaneous capacity expansion of generation, storage and transmission infrastructure. This allows us to consider the trade-offs between different approaches to balancing fluctuations of renewable generation. We find that many similarly costly, but technologically diverse solutions exist. Already a cost deviation of 0.5% offers a wide range of options. However, either offshore or onshore wind energy along with some hydrogen storage and transmission network reinforcement are essential to keep costs within 10% of the optimum. Moreover, we show that cost optimal solutions lead to very inhomogeneous distributions of assets, but more uniform expansion plans can be achieved on a national level at little additional expense.