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Part 2: Factors to Consider With Demand Response Program
By Michael C. English, P.E.
April 2014 -
Power & Communication
Before participating in a demand response program, managers should consider the following five factors:
Performance. Most buildings perform well below their potential, use more energy than necessary, and cost more to operate than they should. Participating in a program with a poorly functioning building will counteract the intended benefits.
Managers should analyze the performance of all the systems in their buildings by conducting an energy audit. This survey of operating conditions is necessary to understand the building's characteristics and the way the building performs based on occupancy, weather and activities. Once the energy audit is complete, managers can benchmark the building's energy use against that of similar facilities.
Commissioning. Over time, building performance degrades due to operational and occupancy changes, and managers and operators can overlook the resulting energy waste. Existing building commissioning (EBCx) addresses an owner's desire to improve building performance, solve comfort and operational problems, and reduce operating costs. Implementing an EBCx program is one of the most cost-effective strategies to reducing energy use, since the process helps uncover many low- and no-cost opportunities.
System knowledge. It is essential that managers know the amount of energy critical and non-critical systems require. Critical systems are those that always need a certain level of energy for the safety of occupants and the protection of equipment. Critical systems — fire and life safety, cooling for data centers, etc. — cannot shut down entirely during a demand response event. Once managers compute the load requirements of the building's systems, they can leverage and balance energy needs among systems.
Lighting. Lighting is a non-critical system, with the exception of life-safety lighting systems. Efficient lighting strategies and technologies are relatively easy and affordable to implement. Lighting does not require as much energy as HVAC systems or plug loads, but the volume of lighting in a facility, along with type of lighting, can make a significant impact.
Among the steps operators could take to curtail energy use are installing lighting controls, timers, zoning and sensors, and maintaining proper scheduling.
Most changes in lighting do not impede on occupant comfort and productivity compared to unfavorable changes in HVAC systems. Most occupants will not detect a gradual change in light level, according to the Lighting Research Center, so a 15-20 percent decrease in light output will have virtually no effect on occupants.
HVAC. HVAC adjustment provides the biggest opportunity to meet demand response signals and reduce energy. Operators should avoid drastic HVAC setting changes because they can result in unintended peaks. Too many changes also can shorten the life cycle of a system and cause immediate occupant discomfort.
To respond to a demand event, operators need to know the HVAC system's optimal set points. Increasing the temperature set point to the highest comfortable value in the summer can significantly reduce energy use. Widening the set point range by 1 degree can save up to 10 percent of the energy used by the HVAC system. Operators often need to change their operational practices, such as progressive control strategies, to ensure optimal efficiency. For example, using one chiller to serve a slightly larger load can be less expensive than adding a second chiller at part load.
Power & Communication
Part 1: Taking Charge of Demand Response
Part 3: Demand Response: The Road Ahead