Environmental Engineering Reference
plaint of a hot or cold temperature or a draft, an operator may zoom in to
the space to feel and measure the temperature. Zooming inside the VAV
box, the operator could check the damper position and view readouts of
air volume and temperature. The thermostat or damper control could be
adjusted while observing the system's operation. The operator could also
check the operation of fans, boilers and chillers using this zoom control.
Adding a sensor to a room could be a simple operation. The sensor may
have a self-adhesive backing and stick to the wall. Power could be sup-
plied to the unit by a built-in solar cell with battery backup. The sensor
would broadcast using infrared, radio wave, or microwave. The computer
will recognize the sensor and assign a point number. The system would
map the location of the sensor using triangulation of the signal and its in-
ternal map of the building. A self-optimization routine would be used to
search for the optimum control strategy to utilize the new sensor.
Power management may involve devices that regulate the on and off
times of selected loads, such as fans, heaters, and motors. These devices
reduce the electrical demand (kilowatts) and regulate energy consump-
tion (kilowatt hours). In the past most of the energy savings has mainly
been in heating.
Power management devices can be electromechanical, electronic, or
computer based. The operation of one or more loads is interrupted by the
power management system based on control algorithms and building-op-
erating parameters, such as temperatures, air flow, or occupancy. The sav-
ings in electrical energy use and cost range from 0 to 50% or more.
Demand limit control is a technique that raises the cooling setpoint
in order to reduce some stages of cooling. This is a building wide sequence
that requires equipment turn-off and avoids demand peaks. Load-shap-
ing involves the prediction of demand excursions for shedding loads or
starting power generators to avoid setting new peaks.
Power-monitoring software can be used to analyze energy use and
power quality. It can identify load profiles to help with rate negotiation.
If companies know their energy profiles, how and when they consume
power, they can negotiate better rates for the type and amount of power
Electrical demand is defined as the average load connected by a user