Civil Engineering Reference
In-Depth Information
Power monitoring and process control to minimize peak use
•
Security
•
Fire protection
•
Maintenance scheduling
•
Report generation
•
These systems should be applied with realistic expectations. They are versatile, but
there are limits to their capabilities. They can be very cost-effective if integrated with
a plant control system. Systems to aid in shifting to off-peak use range from simple
ones that schedule for the operation of pumps, such as backwash, to relatively so-
phisticated computer programs that monitor and predict system needs to optimize
storage to defer pumping.
The following software features should be considered for any energy management
system:
Prioritized selection of the most energy-efficient (in terms of kilowatt-hours per
million gallons or million liters) booster pumps, plant pumps, and wells
•
Real-time monitoring, load reduction, or demand load shedding to take better
advantage of time-of-use rate structures
•
Monitoring of real-time electrical energy prices from a variety of suppliers and
selection of the lowest-cost power available. This capability will be advantageous
as electricity markets are deregulated.
•
Sounding an alarm when a demand target is exceeded or when a pump or other
equipment's efficiency changes from the target condition
•
Automatic operation of pumping systems to fill storage tanks during off-peak or
partial-peak utility rate periods (for facilities where there is sufficient storage)
•
Using programmable logic to control VFDs for maintaining distribution system
pressures and reservoir / wetwell levels
•
Locking out certain equipment or pump stations during peak periods
•
Energy management systems that monitor and control electrical demand can be
inexpensive and highly effective. They operate by regulating real-time demand infor-
mation (taken directly from the electric utility meter) and comparing the demand to a
preset target value. If the target value is approached or exceeded, an alarm will sound
and a manual or computerized load-shedding program will initiate. Energy from
nonessential or even essential equipment will be shut off or reduced until the demand
is reduced below the target or alarm value.
The impact of installing a simple energy management system is shown in Figures
30-12 and 30-13. In 1994, HDR conducted an energy optimization study of a 1.2-
mgd (4.5-ML / d) water treatment plant and recommended the implementation of a
simple EMS to control demand. The system was installed in late 1995. As shown in
Figure 30-12, the demand was systematically reduced from the 150-175-kW range to
approximately 110 kW. More important, costs were reduced by over $1,000 per month,
a 17 percent decrease (Fig. 30-13).
Most electrical utilities are anxious to assist with planning and implementation of
energy conservation measures. Utilities should be contacted early in the project plan-
ning stage in order to gain maximum benefit from their advice.
