Occupant-centric building controls or Occupant-centric controls (OCC) is a control strategy for the indoor environment, that specifically focuses on meeting the current needs of building occupants while decreasing building energy consumption. OCC can be used to control lighting and appliances, but is most commonly used to control heating, ventilation, and air conditioning (HVAC). OCC use real-time data collected on indoor environmental conditions, occupant presence and occupant preferences as inputs to energy system control strategies. By responding to real-time inputs, OCC is able to flexibly provide the proper level of energy services, such as heating and cooling, when and where it is needed by occupants. Ensuring that building energy services are provided in the right quantity is intended to improve occupant comfort while providing these services only at the right time and in the right location is intended to reduce overall energy use. In contrast to OCC, conventional building control strategies, known as Building Energy Management Systems (BEMS), typically use predetermined temperature setpoints and setback schedules. These temperatures and temperature schedules are often determined by industry standards with no input from the building occupants. Conventional BEMS typically have static operation parameters that give minimal flexibility to meet the changing needs of building occupants throughout the day, the changing needs of new building tenants, or the diverse thermal needs of any given group of building occupants. The American Society for Heating, Refrigeration and Air-conditioning Engineers has outlined that thermal comfort of occupants is influenced both by environmental conditions such as radiative heat, humidity, air speed and season as well as personal factors such as physiology, clothing worn and activity level. This dynamic and personalized nature of thermal comfort has traditionally made it complex it integrate into HVAC controls but an increase in sensing and computing capabilities along with a decrease in sensing and computing costs has made it possible for OCC to be an effective and scalable means of controlling building energy systems. With buildings consuming over 33% of global energy, and producing almost 40% of CO2 emissions, OCC could play a significant role in reducing global energy consumption and CO2 emissions.
Background
Occupant-Centric Control Inputs OCC relies on real-time occupancy and occupant preference data as inputs to the control algorithm. This data must be continually collected by various methods and can be collected on various scales including whole-building, floor, room, and sub-room. Often, it is most useful to collect data on a scale that matches the thermal zoning of the building. A thermal zone is a section of a building that is all conditioned under the same temperature setpoint. Data on occupant presence (occupied or unoccupied) and occupancy levels (number of occupants) can be collected with either explicit or implicit sensors. Explicit sensors directly measure occupancy and can include passive infrared sensors, ultrasonic motion detectors, and entranceway counting cameras. Implicit sensors measure a parameter that can be correlated to occupancy through some calibrated relationship. Examples of implicit occupancy sensors includes CO2 sensors and Wi-Fi-connected device count. The selection of occupancy sensing devices depends on the size of the space being monitored, the budget for sensors, the desired accuracy, the goal of the sensor (detecting occupant presence or count), and security considerations. Unlike occupant presence data, acquiring occupant preference data requires direct feedback from building occupants. This feedback can be solicited or unsolicited. Unsolicited occupant preference data can include the time and magnitude of a manual thermostat setpoint change. While this can be a good indicator of occupant thermal dissatisfaction, thermostat setpoint changes can be infrequent creating a barrier to integrating occupant preference into OCC. Solicited occupant preference information is often used as a means of acquiring more occupant preference information and takes the form of just-in-time surveys or Ecological Momentary Assessments (EMA). These surveys, typically deployed to computers, smart phones, or smart watches, can ask participants about their thermal sensation, thermal satisfaction or any other factor that reflects their comfort in the space. Implementing occupant preference information into OCC is still in its early stages and its practical application is still being studied in the academic environment.
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