VFDs Expand Load Capability for Demand Response Programs

By James Piper, P.E.  
OTHER PARTS OF THIS ARTICLEPt. 1: Demand Response: Strategies and Tactics for SuccessPt. 2: This PagePt. 3: Facilities With BAS Have Advantages for Demand Response Programs

VFDs have helped to expand the number of loads managers can curtail in a demand response program. They offer the advantage of significantly reducing motor energy use with even moderate reductions in motor speed.

For example, reducing the speed of a pump or fan motor by 40 percent typically reduces its energy draw by more than 70 percent. By temporarily dialing back the maximum operating speed of the device through the VFD, operators can effectively reduce electrical demand while keeping systems operating, and occupants generally do not notice the difference.

Departments can install VFDs on practically any motor-driven HVAC device — circulation pumps, booster pumps, HVAC system fans, exhaust fans, cooling tower fans, and even chillers.

The advent of smart thermostats also is expanding the capabilities of demand response. Originally, thermostats were considered smart if they allowed users to program temperature setbacks. Some smaller commercial applications also used programmable thermostats to reduce energy use during unoccupied hours.

Today's smart thermostats go beyond this setback capability and include features that prepare them for demand response. This generation of thermostats can receive a signal from the utility, a third party, or from the facility's BAS and adjust the HVAC system's operations according to predefined parameters, including adjusted temperatures or slower fan speeds.

Dimmable lighting systems solve the issues of safety and security by reducing lighting levels rather than turning entire fixtures off. Operators can control the amount of dimming to provide a balance between reduced electrical demand and the illumination requirements of the space.

Wireless links to lighting systems can provide the quick response needed. Since lighting is a major electrical load in many commercial and small business applications, the ability to control lighting electrical use alone might be sufficient reason for participation in a demand-response program.

Reduced lighting levels also produce a side benefit — reduced cooling loads. Lighting systems produce heat, so reducing the lighting electrical load also reduces the cooling load.

Continue Reading: Energy Strategies

Demand Response: Strategies and Tactics for Success

VFDs Expand Load Capability for Demand Response Programs

Facilities With BAS Have Advantages for Demand Response Programs

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  posted on 9/15/2014   Article Use Policy

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