Optimal sizing of hybrid renewable energy systems in rural Alaska

Abstract

Rural Alaskan communities face extreme energy costs and energy insecurity due to logistical isolation and dependence on imported diesel fuel. This study evaluates long term decarbonization pathways for the Shungnak microgrid using a dual planning and operational framework. Tools for Energy Model Optimization and Analysis (Temoa) optimizes capacity expansion from 2025 to 2045, while a rolling horizon Unit Commitment Model (UCM) screens portfolios for hourly dispatch feasibility, generator commitment, ramping, and battery state of charge continuity. The UCM is an operational screening model rather than a complete grid stability assessment and does not represent dynamic frequency response, voltage behavior, or inertia. The constrained Business-As-Usual Reference (BAU) pathway remains diesel dependent, producing 853.9 tons of CO2 in 2045 at a cumulative discounted system cost of 24.66 million USD. Allowing wind and hydropower shifts the least cost pathway toward a diversified renewable and storage portfolio, with all five alternative core scenarios reaching zero modeled operational emissions by 2040 under baseline resource assumptions. Sensitivity tests show that discounted cost is most responsive to wind capacity factor, ranging from 12.4% below to 17.0% above Unrestrained Reference (BAU-UR), followed by hydropower availability, ranging from 9.8% below to 10.8% above. A ±30% variation in battery capital cost changes system cost by 2.3% below to 2.0% above. Capital support tests locate cost parity between 6% and 7%, with an interpolated threshold of 6.34%. Findings are specific to Shungnak, while the open source framework may be adapted to other isolated systems after local calibration.