A study of demand-controlled ventilation (DCV) and constant air volume (CAV) systems

One of the most common measures of IAQ (indoor air quality) is carbon dioxide, CO2, generated by human respiration, in particular, where the main source of pollutions are occupants. In this report, the occupancy-related pollutants are considered as the main pollutant source. However, other type of sources may also be removed satisfactory when governing the ventilation system for removal of
occupancy-related pollutants. In this article, the ventilation system in a room is modelled by a simple dynamic differential equation. The model has then been used for simulations. Simulations of demand controlled ventilation (DCV) systems have been carried out and DCV systems have been compared with constant air volume (CAV). Comparisons based on good air quality (a CO2 concentration less than 1000 ppm) show that DCV using feedback system requires less integrated outdoor air flow
than base/forced ventilation no matter which controller is used. In our simulations the highest difference between CAV-system with a constant outdoor airflow rate on 0.9 m3/s and DCV with variable outdoor airflow rate is 1664 m3 during 45 min. The potential of energy savings by going from a traditional system to the DCV system is high as it is shown by an example in this article.