Optimizing production efficiencies of hot water units using building energy simulations - Trade-off between Legionella pneumophila contamination risk and energy efficiency

Abstract

The energy needed for domestic hot water represents an important share in the total energy use of well-insulated and airtight buildings. One of the main reasons for this high energy demand is that hot water is produced at temperatures above 60°C to mitigate the risk of contaminating the hot water system with Legionella pneumophila. However, this elevated temperature is not necessary for most domestic hot water applications, and has a negative effect on the efficiency of hot water production units. A simulation model has been developed which proposes an alternative to this constant 60°C by predicting the Legionella pneumophila concentration dynamically throughout the hot water system. Based on this knowledge, a hot water controller is added to the simulation model that sets a lower hot water comfort temperature in combination with heat shocks. In this paper, the simulation model is used to estimate the energy saving potential in a case study building, at the level of the heat production system by reaching higher production efficiencies. Three different production units, namely an electric boiler, heat pump and solar collector have been investigated. The controller is expected to become an alternative for the current, energy intensive, high temperature tap water heating systems.

A whole-system approach for quantifying the value of smart electrification for decarbonising heating in buildings

“…Hot water tanks are often sized to store about 50 L of water per person per day [69]. Hot water in domestic applications is required at a minimum of 55 • C to prevent the growth of harmful bacteria [70]. Although most newly designed heat pumps can reach these temperatures (except in extreme conditions), their performance drops considerably when the difference between condensing and evaporating temperatures increases.…”

Coupling of Modelica Domestic Hot Water Simulation Model with Controller

“…All the technical characteristics of the real boiler were used as input for the Modelica boiler component. This step is described in [10].…”