Energy modeling is playing an increasingly central role in understanding the impact of various loads, gains, and losses on the building energy use intensity (EUI). However, this projected EUI does not usually provide an accurate measure of the actual building energy consumption. One of the biggest reasons behind this inaccuracy is the lack of detailed understanding of occupant behavior and how it impacts the building’s operations such as changing or setting HVAC set points, switching lights on and off, and switching equipment and devices on and off. While controlling set points is easily managed with the help of an automated thermostat, occupancy and daylight sensors, as well as equipment have remained largely unregulated. Left to the mercy of the occupants to switch the equipment off when not in use, the power draw associated with those devices often remains constant, generating significant waste in the process.
Plug and process loads are unrelated to the other building loads such as lighting, heating, ventilation, cooling and water heating that aggregate to comprise a building’s total energy consumption. These plug and process loads are driven by common devices, such computers, laptops, printers, coffee machines, personal fans and heaters, humidifiers, task lighting, household appliances, and networking equipment. Plug load in a commercial building can contribute anywhere between 20 - 30% to the total building energy consumption . This ratio is similar across various building types.
The growing awareness and resultant shift towards designing sustainable buildings, through the use of improved envelope and more efficient MEP systems has led to a tremendous decrease in buildings’ per-sqft energy consumption attributed to heating and cooling loads. This has resulted in the proportional contribution of plug load to total building energy consumption to significantly increase. Thus, effective load reduction strategies like the selection of energy-efficient equipment can have a big impact on aggregate energy consumption.
In addition to installing more efficient equipment, the monitoring and control of plug load is equally, if not more important. Unfortunately, plug load often goes unregulated and unaddressed due to unmonitored occupant behavior and lack of affordable control technologies. Strategies such as active monitoring and reducing the vampire load can reduce the energy associated with total plug load by 20-50%.
The advancement of smart building technologies is necessary to solve the issue of reducing our inadequately-unmetered, unautomated, and generally-outdated buildings’ dependency on the grid for electricity. Sapient’s Autonomous Energy Management System (AEMS) is one such smart building technology.
The Sapient AEMS consists of three core technologies: a control dashboard, smart outlets, and occupancy sensors. The role of the control dashboard is to provide facilities managers with all the insight, control, reporting, and automation capabilities that a building-wide deployment of smart outlets and the resultant device-level power draw data can provide. The role of the smart outlets is to collect data, including power and device type parameters, from each and every plugged-in device in your building. These outlets also provide socket-level control over whether power is being delivered to any of those plugged-in devices. Occupancy sensors provide real-time insight into the way that occupants interact with your facility. When coupled with the understanding of how and when the devices in the building are being used, this data allows for powerful machine learning algorithms to generate rules that decide the most efficient times to power certain types of devices in your facility. Such cutting-edge, device-level power delivery optimization eliminates nearly all vampire load and can reduce aggregate plug load by upwards of 25%.
Building Codes for Plug Load
Several states and major cities across the U.S. are implementing regulatory standards and local laws aimed at curtailing energy consumption. ASHRAE 90.1 standards are the most commonly used basis for these laws and regulations, which include requirements for plug load monitoring and control. The number of jurisdictions enacting these mandates is bound to increase in the future as awareness on sustainability concepts such as Net Zero Energy buildings, passive house standards, and the negative impact of fossil fuels continues to grow.
Some of the more common energy and sustainability standards are listed below. Many of these are driving the shift towards sustainable and energy-efficient design. All of these standards and regulations now require some form of plug load monitoring and control. This is where Sapient’s smart building technology plays a key role.
ASHRAE 189.1 2011:
All buildings with connected plug and process loads that exceed 50 kVA are required to include subsystem measurement devices with remote capability that measure energy consumption data and communicate it to a data acquisition system.
Energy sub-metering of plug loads is required for all buildings 25,000 square feet or larger.
OREGON REACH CODE:
The distribution of all convenience receptacles needs to be isolated from other load types in the building.
ASHRAE 90.1. and Title 24
The two most widely used are ASHARE 90.1. and Title 24. While ASHRAE 90.1 (and corresponding IECC) codes are the basis to prove compliance for LEED, Title 24 is primarily used for mandatory compliance in the state of California.
ASHRAE 90.1 2010 / IECC 2012:
At least 50% of all 125-volt, 15- and 20-amp receptacles in private offices, conference rooms, rooms used for printing and/or copying functions, break rooms, classrooms, and individual workstations not shown on the construction documents. The same is true for at least 25% of branch circuit feeders installed for modular furniture. As a result, ASHRAE 90.1 2010 / IECC 2012 mandates the following monitoring and control requirements.
- Schedule-based — switch off the controlled devices off at the specific programmed time using a timer for areas of no more than 5000 sq.ft. and not more than one floor. The occupant can be allowed to override the control device for up to 2 hours.
- Occupancy-based —a sensor must turn off receptacles within 20 minutes of all occupants leaving a space
- System-based—an automated control or alarm system sends a signal that will turn off receptacles within 20 minutes after determining all occupants have left the space.
TITLE 24 2013:
The ordinance defines four different energy thresholds with varying levels of disaggregation requirements for plug load circuits. All commercial buildings with a plug load service between 50 and 250 kVA need to aggregate plug load separately from other loads in the building. Buildings with a plug load service exceeding 250 kVA need to separate plug loads by floor, type or area. In addition, groups of plug loads exceeding 25 kVA in an area smaller than 5,000 square feet must also be on a separate circuit. Title 24 2013 mandates the following monitoring and control requirements. Exempt from the code are receptacles designed for equipment requiring continuous operation and spaces where automatic control would risk the safety or security of the room or building occupants.
- Install a control capable of automatically shutting OFF controlled receptacles when a space is typically unoccupied, either at the receptacle or circuit level. When an automatic time switch control is installed it must incorporate an override control that allows the controlled receptacle to remain ON for no more than 2 hours from when an override is initiated and an automatic holiday “shut-OFF” feature that turns OFF all loads for at least 24 hours and then resumes normally scheduled operation. Countdown timer switches must not be used to comply with the automatic time switch control requirements.
- Install at least one controlled receptacle within 6 feet from each uncontrolled receptacle or install a split-wired receptacle with at least one controlled and one uncontrolled receptacle. Where receptacles are installed in modular furniture in open office areas, at least one controlled receptacle shall be installed at each workstation.
- Provide permanent and durable marking for controlled receptacles or circuits to differentiate them from uncontrolled receptacles or circuits.
- For hotel and motel guest rooms, install controlled receptacles for at least one-half of the 120-volt receptacles in each guestroom. Electric circuits serving controlled receptacles in guest rooms shall have captive card key controls, occupancy sensing controls, or automatic controls so the power is switched off no longer than 30 minutes after the guest room has been vacated.
In addition to complying with these sustainable building standards and actively reducing the energy consumption, there are many other benefits to Sapient’s smart building technology. Many major cities now have laws (LL 86 in New York City, for example) that require buildings over a certain square footage to achieve a specific certification of sustainability, as measured in LEED rating. Some also require buildings to report the energy consumption data to governing agencies for monitoring and benchmarking (such as LL 84 and LL 87, also in New York City).
Apart from the obvious benefits of optimization, recording such data can be a significant benefit in itself, especially for the operations managers, facilities teams, and the energy modeling community. The plug load data can be used to calibrate plug load in various energy models, while data describing occupancy, occupant behavior, power consumption, usage profiles, and other parameters can be anonymously collected and used to improve the future of energy auditing and regulation.
It’s more than likely that your building’s current energy management infrastructure is lagging behind the laws and regulations being enacted nationwide. For more information about how your building should be managed, metered, and controlled or to get a quote for equipping your building with a Sapient AEMS.