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ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 possibility to shift to a low-temperature DH is considered as a feasible solution to compensate for the loss of performance of the network in combination with a systematic approach to the refurbishment of the connected buildings. For this purpose, an integrated model for both buildings and network has been developed. Several refurbishment measures for the existing buildings have been investigated and a multiobjective (energy and economic) optimization has been conducted, by means of a genetic algorithm to reduce the computational time. The results highlight that the building refurbishment strongly influence both the energy and economic performance of the DH system. The distribution efficiency is considerably low during summer − only domestic hot water (DHW) need − and when a high number of refurbished buildings is considered in the DH network. Nevertheless, the implementation of the minimum network temperature allows a partial compensation for both the energy and the economic losses deriving from the refurbishment. Although an incentive to promote the use of heat at lower temperature has been considered, the economic loss deriving from the incentive could not be paid back.

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This article deals with biomass‐based technologies for polygeneration and district heating ( DH ). The relevant technologies for the generation of heat, power, and biofuels are presented in Section 1 taking into account thermochemical, chemical, and biological pathways. In particular, the opportunity of integrating them for polygeneration—also according to the biorefinery concept—is analyzed here. Biomass combined heat and power ( CHP ) systems for DH application have been compared considering size, efficiency, flexibility of operation, and field experience. In Section 2, heat distribution systems have been described taking advantage of the previous analysis on generation technologies and pointing out the existing relation between distribution, generation efficiencies, and DH network temperature. The current trend toward low temperature DH systems has been then extensively analyzed. The effects of the possible variation in the heat demand—both in the short term (i.e., daily to seasonal utilization profiles) and in the medium term (e.g., building refurbishment)—on the DH system operation and efficiency, are presented here. The biomass CHP systems are also discussed in the vision to extend the smart grid concept to thermal networks. As a whole, pilot or real‐plant data and validated theoretical models are used to support the analysis.

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