Towards energy efficient and healthy buildings: trade-off between Legionella pneumophila infection risk and energy efficiency of domestic hot water systems

摘要

The production of Domestic Hot Water (DHW) dominates the total energy demand. One of the main reasons for the high energy demand is that DHW is stored and distributed at temperatures above 55°C to mitigate the risk of infecting the DHW system with Legionella pneumophila. At these temperatures, Legionella pneumophila bacteria are effectively killed. For most of the applications of DHW, temperatures of only 30-40°C are required. This disparity (between 55 and 30-40°C) doubles the temperature difference between DHW system and environment and has a detrimental effect on the efficiency of DHW production units.A simulation model is developed that allows to investigate the infection risk for Legionella pneumophila in the design phase of a DHW system and to test the effectiveness of disinfection techniques on an infected system. By developing a simulation model that allows assessing the Legionella pneumophila infection risk in dynamic conditions, HVAC designers will be able firstly to thoroughly assess the infection risk associated with their design and secondly to optimize the temperature regimes, choose better hydronic controls and reduce the energy demand for DHW production. In addition to the modelling work, a test rig is built which will serve to run experiments that will allow testing, validating and improving the simulation model.In future research this thermodynamically validated model, will be used to assess the Legionella pneumophila infection risk of 5 to 10 often used DHW configurations from REHVA design guidelines for DHW systems and new design guidelines for these configurations will be proposed based on an optimization study that looks at the trade-off between Legionella pneumophila infection risk and energy efficiency.