Clifford Federspiel, Research Specialist, Center for the Built Environment
David Auslander, Professor of Mechanical Engineering

Sponsor: UCEI

Many electrical loads used to control process variables such as temperature in buildings are operated as binary, or "on-off" devices (or staged if more than one "on" state) rather than as continuously modulating devices. The operation of binary loads such as air-conditioners is not usually coordinated with the operation of other binary loads. The devices are normally turned on and shut off when the process variable (e.g., space temperature) crosses a level. The advantage of using level-crossings to trigger operation is that the control logic is extremely simple. The disadvantages are that control performance may be poor. Simple level-crossing logic cannot control the variation in the process variable that results from the on-off nature of the operation. It is also not well-suited for staged operation in which there exists two or more "on" states.

The operation of binary loads is also not coordinated with the billing and metering events that affect the cost of electric power. Such events include the start of the billing period, the start of a daily or hourly period at which the cost of consumption changes, and the start of each demand interval. Daily events that affect the cost of electricity are the start/stop events associated with on-peak and off-peak periods in a time-of-use rate structure. Hourly events that affect the cost of electricity are the changes in the consumption prices of a real-time-pricing (RTP) rate structure. The demand interval is the time over which power is accumulated for the purposes of billing. Demand intervals are most commonly 15-minute, non-overlapping intervals of time.

The goals of this project are to develop and demonstrate the benefit of control software that coordinates the operation of binary electrical loads in buildings. Computer simulations will be used to compare the new control software with existing methods of operating binary electrical loads. Comparisons will be made on the basis of energy use, energy cost, control performance, and maintenance cost.

This study is important because reliability and cost of electrical power are of increasing concern. This project will reduce the cost of electrical power by reducing the variability in the demand for electrical power and improving the load factor. Doing so will reduce the need to set aside backup power to meet unpredictable loads. In a deregulated energy market, this project will decrease the cost for the consumer because the consumer will be able to use the improved load factor and reduced variability to negotiate a lower rate from a supplier. In a regulated energy market, this project will decrease the cost for the consumer by lowering the peak demand.