Optimal economic and environmental design of multi-energy systems

Designing decentralized energy systems in an optimal way can substantially reduce costs and environmental burdens. However, most models for the optimal design of multi-energy systems (MESs) exclude a comprehensive environmental assessment and consider limited technology options for relevant energy-intensive sectors, such as the industrial and mobility sectors. This paper presents a multi-objective optimization framework for designing MESs, which includes life cycle environmental burdens and considers a wide portfolio of technology options for residential, mobility, and industrial sectors. The optimization problem is formulated as a mixed integer linear program that minimizes costs and greenhouse gas (GHG) emissions while meeting the energy demands of given end-users. Whereas our MESs optimization framework can be applied for a large range of boundary conditions, the geographical island Eigerøy (Norway) is used as a showcase as it includes substantial industrial activities. Results demonstrate that, when properly designed, MESs are already cost-competitive with incumbent energy systems, and significant reductions in the amount of natural gas (92%) and GHG emissions (73%) can be obtained with a marginal cost increase (18%). Stricter decarbonization targets incur larger costs. A broad portfolio of technologies is deployed when minimizing GHG emissions and integrating the industrial sector. Environmental trade-offs are identified when considering the construction phase of energy technologies. Therefore, we argue that (i) MES designs and assessments require a thorough life cycle assessment beyond GHG emissions, and (ii) the entire life cycle should be considered when designing MESs, with the construction phase contributing up to 80% of specific environmental impact categories.