Seasonal storage and demand side management in district heating systems with demand uncertainty.

District heating is an under-researched part of the energy system, notwithstanding its enormous potential to contribute to Greenhouse Gas emission reductions. Low-temperature district heating is a key technology for energy-efficient urban heat supply as it supports an efficient utilization of low-grade waste-heat and renewable heat sources. The low operating temperature for such grids facilitates the integration of seasonal thermal energy storage, enabling a high degree of operational flexibility in the utilization of both uncontrollable and controllable heat sources. Yet, an inherent challenge of optimizing the operation of low-temperature district heating networks and its flexibility is the underlying uncertainty in heat demand. We develop a new stochastic model to minimize the total operational cost of district heating networks with local waste heat utilization, seasonal storage and uncertain demand. We consider in particular how demand side management and seasonal storage can improve the operational flexibility and thereby reduce costs. We analyze different set-ups of a local low-temperature district heating network under development in a new residential area in Trondheim, Norway. We find up to 37% reductions in carbon dioxide emissions, 29% generation reduction in peak hours, and 10% lower operational costs. These large values highlight the significance of flexibility options in low-temperature district heating networks for cost-effective, large-scale deployment