Existing industrial standards, e.g., American Society of Heating, Refrigeration, Air-conditioning Engineers (ASHRAE) Standards 62.1 and 90.1, set up detailed advanced energy efficient operations. However, some operations cannot readily be implemented because of the lack of low cost, reliable water and air flow meters. Consequently, the lack of flow measurements leads to inadequate energy performance evaluation for heating, ventilation and air conditioning (HVAC) system. The goal of this project was to improve the energy efficiency of Department of Defense (DoD) buildings while maintaining or improving indoor air quality by increasing the intelligence of building energy management using virtual flow meter technologies. Specifically, the technical objectives were to:

  1. Validate energy savings, costs and benefits of the proposed technologies, including the virtual flow meters and the performance degradation detection (PDD).
  2. Document findings and guidelines from the demonstration to promote low-cost virtual meter implementation through the existing DoD energy meter policies and encourage widespread adoption of the Building automation system (BAS)-embedded PDD.
  3. Enable technology transfer through the demonstration by showcasing benefits of the technology to increase DoD and vendor acceptance.

Technology Description

The virtual flow meter technology was a key component of the PDD in this project. Three different types of virtual meters significantly enhanced the measurement capacity of the BAS. They are described as follows: In Type 1 meters, the whole building level chilled water flow rate and hot water flow rate were virtually obtained using pump operational characteristics, namely a pump flow meter. In Type 2 meters, the airflow rate in each air handling unit (AHU) was virtually obtained using fan operational characteristics, namely a fan flow meter. In Type 3 meters, the chilled water flow rate in each AHU was virtually obtained using control valve operational characteristics, namely a control valve flow meter. The PDD used the BAS data plus the measurements from the virtual flow meters at pumps, fans and valves to determine the actual energy use of key building systems and subsystems. The energy use and air/water flow rates of energy efficient operations for those systems, i.e., reference values for practices conforming to standards and guidelines set by ASHRAE and other authorities, can also be obtained through virtual flow measurements based on energy balance and/or mechanisms of subsystems. By comparing the actual energy use/setpoint with the reference energy use/setpoint, the energy degradation or operating system malfunctions can be detected.

Demonstration Results

The demonstration involved validation of 43 virtual fan/valve/pump flow meters. Of these, 40 meters (93%) had errors of less than 1.2% at 95% confidence. The remaining 3 meters had errors between 2% to 3% at 95% confidence. The average annual total cost savings was $74,629 based on the blended utility rate of $0.0522/kWh and $4.02/MMBtu, i.e., 15% annual energy cost. It is worth mentioning that the demonstration building is a Leadership in Energy and Environmental Design (LEED) certified new clinic building. All the savings were obtained through soft corrections on the system operation sequences without hardware replacements. For the demonstration building, the total cost was $110,295 with a simple payback of 1.5 years.

Implementation Issues

The implementation issues include obtaining cybersecurity clearances, as well as potential increases in facility operators’ workload. Therefore, a more economical implementation approach would be to hire contractors, either BAS service providers or technology licensee (the PDD installer), by paying a small monthly fee to maintain service to support the technology.