Overview of Solutions for the Low-Temperature Operation of Domestic Hot-Water Systems with a Circulation Loop

Theofanis Benakopoulos, William Vergo, Michele Tunzi, Robbe Salenbien and Svend Svendsen
Additional contact information
Theofanis Benakopoulos: Energy Technology Unit, Flemish Institute for Technological Research (VITO NV), Boeretang 200, 2400 Mol, Belgium
William Vergo: Department of Civil Engineering, Technical University of Denmark, Brovej, Building 118, 2800 Kongens Lyngby, Denmark
Michele Tunzi: Department of Civil Engineering, Technical University of Denmark, Brovej, Building 118, 2800 Kongens Lyngby, Denmark
Robbe Salenbien: Energy Technology Unit, Flemish Institute for Technological Research (VITO NV), Boeretang 200, 2400 Mol, Belgium
Svend Svendsen: Department of Civil Engineering, Technical University of Denmark, Brovej, Building 118, 2800 Kongens Lyngby, Denmark

Energies, 2021, vol. 14, issue 11, 1-25

Abstract: The operation of typical domestic hot water (DHW) systems with a storage tank and circulation loop, according to the regulations for hygiene and comfort, results in a significant heat demand at high operating temperatures that leads to high return temperatures to the district heating system. This article presents the potential for the low-temperature operation of new DHW solutions based on energy balance calculations and some tests in real buildings. The main results are three recommended solutions depending on combinations of the following three criteria: district heating supply temperature, relative circulation heat loss due to the use of hot water, and the existence of a low-temperature space heating system. The first solution, based on a heating power limitation in DHW tanks, with a safety functionality, may secure the required DHW temperature at all times, resulting in the limited heating power of the tank, extended reheating periods, and a DH return temperature of below 30 °C. The second solution, based on the redirection of the return flow from the DHW system to the low-temperature space heating system, can cool the return temperature to the level of the space heating system return temperature below 35 °C. The third solution, based on the use of a micro-booster heat pump system, can deliver circulation heat loss and result in a low return temperature below 35 °C. These solutions can help in the transition to low-temperature district heating.

Keywords: domestic hot water systems; low return temperature; circulation heat loss; storage tank; heat exchanger; micro-booster heat pump (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (6)

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