A mixed-integer linear programming approach for an optimal-economic design of renewable district heating systems

Global climate change has had devastating results in the last decades, and the fossil fuel-driven heating sector needs to transform into a sustainable system. Therefore, we examined the economics of different renewable and non-renewable technologies, suggesting possible transformation technologies that favour an economic system. We applied our method to a district heating system in Germany. The method is a mixed-integer linear programming model capable of optimizing the design and operation of energy converters and storage in dependency on an economic objective function. The results have shown that biomass heat plants and large-scale heat pumps can compete with gas-fired CHP plants. In 2022, gas is neither an economical nor a sustainable solution. Furthermore, it was shown that the optimizer strives towards a low-temperature system. Large-scale heat pumps, biomass plants and temperature lowering measures should be part of the design of sustainable economic district heating systems.