Energy bill savings through alternative management measures
To control the development of Legionella in sanitary systems, the WTCB and VITO drew up the "Handbook of Best Available Techniques for Legionella control", or BAT handbook for short (https://www.zorg-en-gezondheid.be/handboek-bestbeschikbare-technieken-voor-legionellabeheersing). The techniques described in it (BAT) aim to prevent the development of Legionella bacteria in the distribution systems of sanitary water within residential and non-residential buildings. These techniques are aimed at keeping water temperatures outside the interval of 25°C to 55°C. The standard management measure for legionella control in hot water is temperature control, which means that sanitary hot water is kept at a temperature of at least 60°C.
The Flemish Department of Care (Departement Zorg) has recognized several alternative management measures that allow deviation from this standard management measure. The advantage is twofold.
First, savings can be made on the investment of a secondary heating step. If the hot water temperature can be limited to 50°C, it is sufficient to work with a heat exchanger to reach this temperature. If a hot water temperature of 60°C is required, a secondary heating step must therefore be installed.
Secondly, heating costs are considerably lower when the hot water temperature drops. Two independent studies demonstrate this. In the doctoral study "Coupled thermohydraulic and biological modelling of Legionella pneumophila in residential hot water systems" by dr ir Elisa Van Kenhove, 2019, the difference in energy demand was investigated between maintaining a constant hot water temperature of 60°C and a hot water temperature of 37°C, alternated with heat shocks. This showed the energy saving to be 38%. A second study carried out by Unica Energy Solutions and presented at Aqua Nederland 2022 calculated that a constant reduction from 65°C to 55°C produced a saving of 31% in energy demand. The 32% lower CO2 emissions were an additional benefit.
To prevent Legionella formation at reduced temperatures, only chemical water disinfection is accepted as a certain solution today. The approach with the Konax® Easydis Unit falls under this. Other alternative techniques are being further developed and evaluated.