2023ICERD8-C11 -- Case Study: Reducing Energy Consumption Through Optimizing Sequence of Operation of Existing DOAS

Introducing outdoor air to improve buildings’ indoor air quality while reducing energy consumption is always a challenge to the HVAC design engineer. The challenge becomes more complicated in hot and humid climates due to increase in dehumidification load. One of the effective methods to overcome this challenge is to separate the ventilation air from the main HVAC unit through the use of Dedicated Outdoor Air Systems (DOAS). The use of DOAS to supply ventilation air to buildings, especially in hot and humid climates, has significantly increased over the last decade; however, applying DOAS in such climates without careful consideration of energy conservation elements can result in significant increase in building’s energy consumption. This paper focuses on a case study where significant reduction in energy consumption was achieved through optimizing the sequence of operation of an existing DOAS located in humid climate in the Eastern Province of Saudi Arabia. Prior to the optimization process, the control of the existing DOAS was initially set to continuously cool the outdoor air to 12.8°C (55°F) to reduce moisture content and reheat the air to the space temperature. The cost-effective optimization technique implemented in this case study configures the sequence of operation of the DOAS to automatically reset the supply air temperature based on dry-bulb temperature and dew-point temperature of the outdoor air. The paper analyzes the annual energy consumption of the DOAS prior to the optimization (base case) and post-optimization based on actual hourly meteorological data.