DSM Options

Figure 20-2 shows representative load shape objectives of utilities that underlie utility-sponsored DSM programs. These programs are designed to produce certain load shapes as a means of accomplishing their objectives. Following are descriptions of the main categories of electric utility DSM programs.

• Conservation programs: The promotion of decreased electricity usage throughout the year, usually with some commensurate reduction in peak period demand. Reducing the electricity consumed is accomplished by improving the efficiency of energy-using devices.

Examples include the installation of high-efficiency lighting, motors, and electric chillers, as well as the installation of insulation to reduce heat gain and, therefore, cooling load.

Load leveling programs: The adjustment of electric load according to the cost of serving it by time-of-use. Reducing peak seasonal or daily demands, for example, generally impacts directly on the need to build new peaking capacity (e.g., power plants) and, therefore, can result in significant savings. The five general types of load leveling programs are:

— Load building programs that involve increasing electric loads. An example is the use of heat pumps to build winter electric load for summer peaking electric utilities, although this may also increase summer peak loads.

— Valley filling programs that build load but target increases in load in daily or seasonal off-peak periods. Valley filling programs build load to improve system efficiency without the need for additional utility investment. An example is electric space heating equipment that does not increase peak loads for summer peaking utilities.

— Peak clipping/load shedding programs that reduce peak seasonal, daily, or hourly demand in order to defer or avoid the need to add new generation, transmission, and/or distribution capacity. Examples are duty-cycle or load shedding energy management systems and interruptible electric rate programs.

— Peak shifting programs that retain electric load, but move it from peak demand periods to lower demand or off-peak periods. Examples are programs that involve a change in production schedules or the use of thermal energy storage (TES) systems that allow for cooling systems to operate off-peak and store ice or chilled water for use during peak periods.

— Seasonal load reduction that changes load shape, yielding increased electric utility seasonal control over the level and/or timing of demand. Examples include high-efficiency cooling equipment and fuel switching for seasonal end-uses such as cooling.

Fuel (or energy source) switching programs: These involve encouraging customers to improve energy service efficiency by selecting an alternative fuel (or energy source). These fuel choice strategies are currently most commonly used by combined electric and gas utilities seeking to lower electric peak demand while filling a gas throughput valley. In some cases, fuel switching programs result through unilateral or joint electric and gas utility planning encouraged by state regulatory commissions. While listed separately, this category may be considered part of peak clipping, seasonal load reduction, or conservation.

The choice of load shaping strategy for a utility will depend upon its unique load characteristics. The utility's load factor and peaking times will determine whether it will need new baseload power capacity or peaking capacity and where it may seek to do its load building or load reductions.

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