Abstract
The development of sustainable and innovative solutions for the production and supply of energy at district level is nowadays one of the main technical challenges. In the past, district heating and cooling networks aimed to achieve greater energy efficiency through the centralization of the energy production process but with relevant losses related to heat transport. Moving towards a higher share of renewables and lower demand of primary energy requires redesign of the energy district networks. The novel concept of cold district heating networks aims to combine the advantages of a centralized energy distribution system with low heat losses in energy supply. This combined effect is achieved through the centralized supply of water at relatively low temperatures (in the range 10–25 °C), which is then heated up by decentralized heat pumps. Moreover, cold district heating networks are also very suitable for cooling delivery, since cold water supplying can be directly used for cooling purposes (i.e., free cooling) or to feed decentralized chillers with very high energy efficiency ratio. This paper provides a preliminary literature review of existing cold district heating networks and then qualitatively analyses benefits and drawbacks in comparison with the alternatives currently used to produce heat and cold at district level, including the evaluation of major barriers to its further development.
Highlights
The integration and implementation of renewable energy systems at district scale is described in a number of recent reports and studies, including [1,2,3,4,5,6]
This paper provides a preliminary literature review of existing cold district heating networks and qualitatively analyses benefits and drawbacks in comparison with the alternatives currently used to produce heat and cold at district level, including the evaluation of major barriers to its further development
The amount of energy saving depends on working conditions, in particular cold ring water temperature and temperature to the end-users, which influence the coefficient of performance (COP) and energy efficiency ratio (EER) of reversible heat pumps
Summary
The integration and implementation of renewable energy systems at district scale is described in a number of recent reports and studies, including [1,2,3,4,5,6]. In ULTDH networks, decentralized micro-heat power stations should be used to boost the domestic hot water (DHW) temperature as needed [21] Another advantage of 4th generation systems is the possibility of using cheaper materials like plastic for pipes and other network components, including a relevant decrease of insulator thickness and related costs. A possible alternative is the use of decentralized absorption chillers for the production of cold, the supplying pipeline being a hot network [44,45]: in this case, the application of 4th generation district heating networks would be not favoured, since hot water temperatures lower than 85–90 ◦ C produce lower (if any) cooling effect in the absorption chillers. Economic aspects related to energy prices are not directly evaluated in the paper since both electric energy and thermal energy production are affected by local frameworks
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