On the possibilities to increase energy efficiency of domestic hot water preparation systems in existing buildings - Long term field research

Energy consumption for domestic hot water (DHW) preparation is one of the main components of the energy balance of the existing and newly designed buildings. However, based on the number of existing buildings and the related opportunities to improve energy efficiency, an important issue is to propose effective and low cost methods that allow to reduce the heat consumption in existing domestic hot water systems and are fast in the implementation. This article presents the results of an experimental research conducted in 12 objects (9 multifamily buildings and 3 thermal substations) assigned to three groups (A, B and C), depending on the analyzed feature of the domestic hot water system. The objects in the group A were analyzed in detail (each 1 h during one full heating season) in order to clearly show the amount of the heat used for circulation of hot water. The group B of objects characterized by the installation of temperature control valves (TCVs) under the risers of circulation installation. The third group consisted of the objects in which the temperature of hot water was decreased during the night hours. The objects from group B and C were analyzed over 8 years. The share of heat losses associated with the circulation of hot water in the total heat consumption supplied for its preparation was in the range from 56.7% to 70.5% for the Group A objects. On the other hand, the energy savings were calculated using different methodologies and for the recommended one they ranged from 8.5% to 49.5% for group B objects and from 6.0% to 14.4% for group C objects. (C) 2019 Elsevier Ltd. All rights reserved.