Demand Controlled Ventilation Energy Savings for Air Handling Units

Abstract

Heat, cooling, and ventilation units are major energy consumers for commercial buildings, they can consume as much as 50% of the total annual power usage of a building. Coherent management of an air handling system’s energy is a key factor of reducing the energy costs and CO2 emissions that are associated with the demand for ventilating and conditioning the air in a building. The issue is that buildings are frequently over ventilated as a full assessment of the air handling unit (AHU) data is not evaluated by building operators. According to ASHRAE standards there are three key parameters that control indoor air quality (IAQ); these are the temperature, humidity, and CO2. Commonly occupancy setpoints implemented by building operators are focused on temperature and humidity control while neglecting the CO2 levels and their impact. While this may seem insignificant additional data proves to be important and can assist with energy management. Additionally, it can develop awareness of implementable procedures which conserve energy. Furthermore, data is not monitored in regard to the continuous assessment of the energy consumption with respect to analysis of opportunities to implement energy saving control strategies. By using these standards as a guide an AHUs energy can be managed more effectively by measuring the data and assessing the outputs compared to the standard. Previous research has shown that up to 75% savings for the ventilation fan energy is achievable when taking into account ASHRAE ventilation standards and controlling outside air ventilation, however, this research has omitted investigating the savings for other energy consumers associated with AHU’s operation. In order to assess the demand, it is required that the CO2 levels of the occupied zones be measured, and the outdoor air ventilation rate be adjusted based on real-time demand. The goal of the research is to assess the number of CO¬2 sensors needed to accurately measure demand-based needs for ventilation and determine an algorithm that will help building operators assess the energy savings by implementing demand-controlled ventilation (DCV) procedures. The scope of this research is to identify what sensors at minimum are required to collect the most pertinent data for implementation of a comprehensive energy saving algorithms and assess the impact on energy consumption of AHUs when demand-controlled ventilation procedures are implemented.