Summary:
District heating networks (DHN) are becoming an energy-saving and cost-effective alternative to conventional conversion systems (boilers, chillers, combined heating and power systems) and appear as a vector of the energy transition because of the diversity of the energy sources that can be used for their operation. They are increasingly used in cogeneration and more efficiently when operating at lower temperature levels. Indeed, many previous works were able to simulate thermal and hydraulic losses of different structures of networks. These works have been carried out in several European countries, notably in Switzerland, Great Britain but also in countries such as Denmark and Sweden. The approach for representing the networks and the simulation models could be complex to use for a general optimization purpose. This paper presents a new approach and methodology to represent the structure of the network in order to simplify models while performing accurate calculations for the thermal and hydraulic losses in the systems. The key parameters for the design and operation of the advanced heating/cooling network such as the nominal capacity of the network and the range of the working conditions (flow rates, minimum heating/cooling capacity, differential temperature on the substations) can be easily defined in hourly basis. A typical application for a set of high-performance buildings in the BlueFACTORY district (Fribourg, Switzerland) has been considered to simulate different structures (branched, mesh or mixed network systems) of advanced thermal networks. The performances, in term of pressure drop and thermal losses on the pipes, are determined in function of the geometric and operational parameters of the network. It includes the configurations of decentralized substation units (heat exchangers, heat pumps, or mixed substations) for heating and hot water production.
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