Optimizing thermal energy storage in fourth generation thermal networks

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Future renewable energy systems will need to integrate thermal energy storage in order to bridge periods of low renewable energy availability and to optimize system operation. On the other hand, the integration of storage can reduce curtailment during periods with excessive renewable energy availability. Sensible TES shows great potential in the latest generation of thermal networks (4th generation thermal networks), which are expected to be very performant in coping with waste heat sources and distributed generation based on renewable sources. This research aims at optimizing the location and size of different possible sensible TES systems in a thermal network. Linearized component models are used, combined with an optimal control strategy. This control strategy assumes perfect knowledge of disturbances and comfort constraints are incorporated. The implementation of the novel pipe model described by van der Heijde et al. is crucial to obtain realistic optima. For thermal networks supplied with low temperature differences, which is the case in 4th generation networks, the relative importance of the heat losses increases and this necessitates the use of realistic heat loss models. An important question to be answered is whether the best option (in terms of cost, or energy use) is to install a large central storage system, or to have a number of smaller decentralized units at strategic locations in the network. A simulation case study in the city of Genk (Belgium), which consists of 18 000 buildings and spans an area of over 80 km2, is selected in order to have a realistic virtual test bed for the optimization algorithm.

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