OSeMOSYS

OSeMOSYS, short for Open Source energy Modeling System, is an open-source framework for long-term energy system optimization and policy analysis. It is designed to be transparent, flexible, and accessible to researchers, policymakers, and educators, enabling the exploration of least-cost evolutions of energy supply and demand while incorporating technology options, costs, constraints, and policy targets. The model represents the energy system as a set of technologies and fuels across time slices, such as years or multi-year periods.

In OSeMOSYS, decision variables include capacities, energy production by technology, and capital stock, with the objective of minimizing total system cost (investment plus operation and maintenance) over the planning horizon. The model enforces energy balance constraints, technology and resource constraints, and policy constraints such as renewable energy shares or emission targets. It supports demand projections, technology learning, and policy specifications, allowing users to test scenarios, sensitivities, and different future conditions. The framework is designed to be solver-agnostic and well-documented to promote transparency and reproducibility.

Implementation and use: OSeMOSYS is released under an open license and is intended for use by researchers, governments, and educators. Models can be built in plain text and solved with standard optimization solvers such as GLPK, CBC, or commercial solvers. Its modular structure facilitates adding new technologies, fuels, and policies, and it supports scenario analysis, sensitivity studies, and regional or national energy planning. It has been applied in academic and policy contexts to compare pathway options for electricity, heating, and transportation, with particular emphasis on developing countries.