Energy trilemma in active distribution network design: Balancing affordability, sustainability and security in optimization-based decision-making.

• Energy trilemma objectives are not always conflicting in network design. • Stand-by fossil generators combined with batteries as backup for blackouts. • Required external grid capacity ranges between 43% and 228% of peak load. • Changes in capital expenditure and self-supply could affect business models. • No consensus between 4 multi-objective decision making methods. A significant reduction in greenhouse gas emissions entails complex trade-offs among economic, environmental and security objectives of the energy trilemma. The associated proliferation of distributed energy resources in power distribution networks requires optimized planning to ensure economic efficiency and security, where security is defined as the ability to withstand outages (reliability) and imbalances between generation and load (flexibility). This paper investigates the trade-offs among active distribution network design solutions in the energy trilemma. Storage, renewable and dispatchable generators are installed to minimize cost, interruptions and emissions via epsilon-constraint mixed integer linear program. The ramping capability of distributed energy resources is harnessed to provide flexible capacity to the surrounding grid, and to enable the transition from active distribution networks into microgrids with islanding capability. Decision-making strategies for selecting the best design from a Pareto-optimal set are contrasted based on the economic, sustainability and security of the design and operations. Applying these strategies to a Californian distribution network shows nonlinear trade-offs between the trilemma objectives, reducing both emissions and interruption durations by up to 64%. Remarkably, energy supply is diversified with up to 47% of local generation entailing a strong reduction in operating expenditures. While the increase in local generation can reduce the peak imports from the surrounding grid by 56% compared to a network without distributed energy resources, enforcing strict emission limits can lead to renewable exports that exceed the peak load by 130%. Sensitivity analyses identify the performance indicators which strongly influence the selection of the best design. [ABSTRACT FROM AUTHOR]