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Part 3: Demand Response: How to Meet Load-Reduction Targets
By James Piper, P.E.
August 2011 -
Energy Efficiency Article Use Policy
Before committing to a program, managers must understand the amount of load they will reduce and the way they will meet that target.
They can start by identifying the loads they can shed with minimal disruption to operations. The amount must be significant enough to make a meaningful contribution to the overall load reduction. Typical loads include air-conditioning compressors, lighting systems, electrical heaters, elevators, and non-critical process loads.
Next, managers need to determine the amount of time they can take each load out of service without significantly disrupting operations. For example, large chiller systems have a built-in thermal-flywheel effect that allows the system to shut down for a specific timeframe with little or no noticeable change in space temperatures.
The key is to identify the length of time they can be out of service. Smaller systems, such as heat pumps serving a particular area within the facility, typically have a much shorter downtime period before seriously affecting operations.
Looking beyond HVAC systems, lighting systems — particularly those where every fourth or fifth fixture connects to a standby generator — offer additional opportunities. In most cases, facilities can shut the systems down for extended periods. If lighting systems will be a major component in the demand-response plan, mangers need to make sure shutting off lights does not compromise safety.
In facilities with a centralized BAS, managers need to work with technicians to determine if the system's software will allow the system to automatically shut down designated loads once the facility receives notice of a demand-response event. If the system cannot automatically shut down the equipment, managers need to build in enough time for operators to respond manually.
In situations where technicians are manually shutting down equipment at the start of an event, they also must restart those loads once the event concludes. Managers must consider the time required to manually turn off loads when establishing the program. Not all facilities can respond quickly enough to justify participation.
Fortunately, technologies are available with additional ones under development that will help to automate the demand-reduction process. When implemented, these systems will automatically shut down the loads for the designated period once the utility sends event notification. Again, managers will have to weigh the cost benefit of these systems.
Finally, managers should not overlook the impact standby generators can make in meeting demand-reduction goals. Running generators costs money. Generators require fuel, and their components require ongoing maintenance. They make noise, potentially disrupting facility operations. But, with the proper loads connected to them, generators can reduce a facility's electrical demand, particularly for the duration of most demand-response events.
Demand Response: Commitment to Curtailing Energy
Part 1: Demand-Response Programs: Understand Risks and Benefits
Part 2: Demand Response: How to Coordinate Peak-Load Reductions
Part 4: Demand-Response Programs Affect Operations and Occupants