By Ryan Zimmerman, Electrical Engineer
In the previous issue of the PCC Journal, we discussed how demand control can help companies lower their utility bills by smoothing out their electrical demand (the kW amount of electricity required for operations). This article looks at six great options for setting up an effective demand control program—and eliminating those costly demand charges!
Option 1: scheduled operations. Under scheduled operations, all operations are metered to determine their electrical load and then run at predetermined times, with some functions staggered so they don’t operate simultaneously. High-demand operations are then run at night, when utilities typically relax their kW demand limits. Scheduled operations often work well in situations where production is consistent from day to day.
Option 2: manual control. In a manual demand control system, someone is responsible for monitoring electrical demand (using meters) and shutting down certain equipment when the demand reaches a target level. Manual control is an effective demand control alternative—and one that’s fairly economical to implement. But if you decide on a manual system, we recommend also incorporating some type of alarm scheme to alert personnel when facility electrical demand is nearing its limit.
Option 3: interlocks, load shedders. Interlocks prevent two or more pieces of high-demand equipment from running at the same time. Load shedders automatically shut down equipment before the target electrical demand level is reached (shutdown occurs according to a prioritized schedule). Both methods depend on metering for the capabilities they provide.Interlocks and load shedders are less flexible than other demand control options, which may not make them ideal for environments where production operations change frequently. But if you want guaranteed electrical demand control, they may be the right choice for you.
Option 4: PLCs. Because of their versatility, PLCs can perform a range of demand control functions, from equipment interlocking to complex decision making. Most facilities have an abundance of PLCs, so you may already own all of the equipment you need to implement demand control.
Keep in mind, though, PLCs are not an out-of-the-box solution: they do require custom programming. On the plus side, D.L. Steiner offers complete PLC programming services for demand control applications.
Option 5: demand control systems. Demand control systems are typically whole-facility, software- and meterbased energy management applications that can be as extensive and integrated as you care to make them. With a demand control system, you can control every aspect of energy usage at your facility, not just electrical demand. Demand control systems can be expensive, but their capabilities make them worth every penny.
Option 6: special equipment. Generators and adjustable speed drives (ASDs) can help you avoid demand charges by providing as-needed auxiliary power or by flattening out the power spikes that lead to exceeding the demand limit. The expense of these systems is often offset by what that save you over time.
With the right demand control system, you can get rid of demand charges and significantly lower your facility’s electric bills—but the key is picking the best option from all the available alternatives. For assistance in identifying your ideal demand control solution, contact D.L. Steiner.