Predictive control strategies for optimizing temperature stability in instantaneous hot water systems

• Published in: HVAC&R research 2021-05, Vol.27 (5), p.679-690
• Main Authors: Ehtiwesh, Ismael A. S., Quintã, André F., Ferreira, Jorge A. F.
• Format: Article
• Language: English
• Subjects: Control stability; Controllers; Energy consumption; Gas heating; Hot water heating; Predictive control; Residential energy; Water flow; Water heaters; Water temperature
• ISSN: 2374-4731; 2374-474X
• DOI: 10.1080/23744731.2021.1890959

Domestic hot water production is responsible for a significant part of domestic energy consumption; instantaneous gas heating devices are widely used because they don't require reservoirs, therefore have a competitive use/consumption ratio compared to other technologies. However, users' perception of comfort is severely affected by sudden changes in temperature outside the desired temperature. The instability of the water temperature with overshoots and undershoots is the most common disadvantage, which occurs mainly due to sudden changes in the water flow requested by users and the response delays inherent to the heating system. Traditional heat cell power controllers have difficulties in responding to these problems in a timely manner, as they don't have the capacity to anticipate the effects of sudden variations in water flowrate. In this work, predictive control strategies were developed which, due to its predictive nature, allows anticipating and correcting the negative effects of sudden variations of water flowrate in the temperature. A comparative analysis of model based predictive controllers (MPCs), with and without adaptive function, with traditional controllers used in the tankless gas water heaters (TGWHs) was carried out. Tests in a simulated environment demonstrated better performances in the stabilization of temperature during sudden changes in water flowrates.