HVAC Systems Operation Control Based on Indirect Occupant-Centric Method for Ensuring Safety Conditions and Reducing Energy Use in Public Buildings after Covid-19

A stronger interest in energy independence from unreliable suppliers, together with an increasing awareness towards climate changes and possible consequences, are affecting and accelerating the so-called clean energy transition. Such a transition envisages several actions, and one of them is the need to improve the energy efficiency of buildings – which are one of the most energy-intensive sectors – leveraging advanced energy monitoring systems. It is however well-established that strategies for energy efficiency should not jeopardize occupants’ health and quality of life. Therefore, energy management systems should be ideally designed both to guarantee the required health conditions and acceptable comfort level and at the same time to minimize energy waste. A classic example is represented by ventilation systems, which especially in the post-pandemic period, are often left in full operation also when buildings are empty or with low occupancy.Considering the topic and the available literature, this paper provides a multi-objective optimization approach to control HVAC systems to ensure Indoor Air Quality (IAQ) and healthy conditions by controlling energy use. The IAQ is guaranteed through the definition of an absolute threshold value of CO2 concentration, while the minimization of the infection risk is ensured through the development of a relationship between this and the increase of CO2 concentration over time. In this way, HVAC systems, and in particular ventilation rate, can be tailored around the actual occupancy of the building. The method is extensively tested in a real case study in educational buildings, and expected improvements in energy consumption are evaluated.