LOAD MANAGEMENT AND THE SUMMER SEASON - WHY LOAD MANAGEMENT?
Power companies, communities, businesses, and homes all have times when demand for energy is greater or less based on many factors and the particular needs of the Customers. Utilities are required to have adequate electrical capacity to supply those needs at any time. Heartland is very committed to providing power at the least cost practicable and having adequate resources.
Weather, load growth and lifestyles all contribute a part in establishing Heartland’s and its Customers’ peak needs pool. Managing the demand at peak times not only reduces our Customers’ charges, but also helps Heartland with its resource pool planning and management. It is very expensive to build resources that may be used only sporadically during the year. With escalating market prices, grid congestion and the high cost of fixed resources, the need to control peak capacity use to optimize efficiency and energy costs is extremely valuable.
What is Load Management?
Load management is basically the electronic monitoring of real time power use, combined with a strategic energy management plan that, when implemented properly, may help control hourly, monthly, and annual demand usage and costs. A typical monitoring system has the ability to send a signal to individually placed control devices that open a designated circuit. This signal may be sent as a radio signal or injected right into the power line. Some examples of loads that can be successfully controlled include: water heaters, clothes dryers, water pumping motors, heating systems and air conditioners.
Implementation
Setting monthly load management goals is a combination of accurate projections of each month’s system peak without any control, estimations of the maximum amount of load under control, and a strategy.
Logic would tell you the load should continue to grow from beginning to end of each month in the fall and winter and conversely, the load would continue to become less throughout the month during the spring months. This is because it gets progressively colder in the fall and winter along with fewer daylight hours. Again, the reverse of these factors takes place in spring.
Additional information that is invaluable to the control strategy is to have historical knowledge of peak demands, day of the week, and weather conditions of the two days immediately preceding the peak and on the peak day.
There are several Internet sites that provide history of daily high and low temperatures, wind, and other factors.
Successful load management needs one more critical element. Experience. There is no better teacher.
When a community installs load management controllers, an accurate “inventory” of how many devices and how much load (number of kilowatts) for each device is critical. Although a typical electric water heater may be rated at 4.5 kW, studies show that only one-in-four is actually heating water at a particular time. For simplicity, that equates to approximately 1.1 kW for every electric water heater controlled. The amount of electric heat controlled varies from house to house and has to be estimated for each location.
When the controllers are installed, they are normally addressed in groups. This allows a group of controllers to be turned off for a designated length of time, and then back on. Just before the first group is brought on, a second group is turned off. This allows for building the total control over a longer period of time. The longer the water heaters are off, the greater the load will be when they are turned back on. If the water heater is off for a long period of time and the members of the household draw on the residual hot water, it is conceivable the load brought back on will approach 4.5 kW per device. That means there must be a scheme to bring them back on so not to generate a new peak later in the day.
In summer, the load control may include central air conditioners (A/C). In setting a controlling schedule for A/C, it is important not to shut them off and bring them back on with the intervals between cycles too short. This may be damaging to the compressor motors.
Now you’re off and running with the load control or load management – you have the receivers, monitoring and controlling equipment installed – goals and strategy should be developed.
There is no perfect forward vision, only 20-20 hindsight. Perfect control each month is unlikely. It is also important to balance between efficient load management and customer inconvenience. If customers experience too much inconvenience or discomfort, it is likely they will request not to continue to participate in the program. If a goal or target cannot be achieved during a particular month, then this higher goal should be the target to maintain for the balance of the month. When the month is over, review your goals, strategy and control log. Save this information for future reference.
The savings to the community is essentially the avoided purchased demand from the supplemental supplier (Heartland). In calendar year 2001, each kilowatt not purchased during a particular month from Heartland is a savings of $11.60.
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