Given their very large overall electric loads, manufacturing facilities often have the most to gain of any commercial and industrial (C&I) customer from participating in a demand-response (DR) program. Many manufacturing plants have flexibility in their operations, making them even better candidates. Plants can achieve the financial rewards of participation without impeding production, and joining a program may even be greeted with enthusiasm by employees. But for many plants, especially those that have experienced blackouts, grid reliability is still the prime motivator. DR program participation helps keep the lights on in the service territory.
Though manufacturing facilities tend to carefully monitor their operations, they don’t always do the same with their energy use. And many facility operators have never seen a snapshot of their facility’s load profile. Simply reviewing a plant’s energy-use profile can present a compelling case for manufacturers to participate in DR programs.
Activity schedules of manufacturing facilities vary widely, as do the operations that the facilities perform. Some are active 24 hours per day while others maintain conventional business hours. On summer afternoons, outdoor temperatures may cause a manufacturing facility’s peak cooling demand to occur around the same time as manufacturing operations peak, which may also coincide with utility peaks. This makes industries like metal scrapping excellent candidates for DR because processes can be shifted to off-peak periods.
Manufacturing facilities vary widely in activities and equipment, but process loads, the primary functions of a facility, are the top energy users in nearly every instance. Compressed air is also a large consumer in 70 percent of manufacturing facilities, providing mechanical motion, cooling, pressurization, and other functions for tools, actuators, and robotics. Drivepower accounts for a major of portion of the load in some facilities as well. HVAC and lighting systems are next, followed by other equipment such as computers used in plant offices. Battery charging stations may also represent significant loads. Some high-tech manufacturing facilities employ a building automation systems (BAS), and backup generation is likely available where power outages could prove disastrous to the manufacturing process.
After performing an energy audit, a wire manufacturer achieved a noticeable load reduction by participating in a DR program (Figure 1). During the DR event, seven production lines were temporarily halted to reduce demand.
Occupant comfort is not a top priority in manufacturing facilities and HVAC energy consumption is usually rather small compared to production costs. Spaces are usually conditioned to regulate humidity and temperature to protect sensitive materials or perishable food products. Maintaining production is generally the highest priority. Opportunities exist to reduce demand systemwide without affecting production—especially at times and in processes where facilities may unwittingly be spending a lot on energy.
Manufacturing facilities can successfully participate in load reduction events using several proven strategies.
Moving processes off peak. Many manufacturing facilities can schedule processes for off-peak times if given advance notice of a DR event and others can change schedules with little notice, shifting large loads off peak. For example, when given advanced notice of a DR event, the operator of a cubic zirconia factory, which forms crystals in batches, orders nearly finished batches rushed through production and waits to start the next batch until after the peak. At some stages of the process, production can even be shut down midway without loss of product—leading to 4 megawatts of overall load reduction during the DR event.
In another example, a metal-scrapping operation powers down equipment and stockpiles scrap for the length of the curtailment, receiving 35 cents per kilowatt-hour dropped per occurrence (in addition to monthly incentives from the utility).
Switching to onsite generation. Many manufacturing facilities have onsite backup generation and are good candidates for DR programs that allow the building’s load to be shifted onto these generation sources. Switching to backup generation is usually immediate and causes no interruptions to service.
Curtailing lighting. Although lighting is one of the smallest loads in most manufacturing facilities, the facilities can still obtain some benefit by manually curtailing or dimming lights that are nonessential or located in unoccupied areas.
Using a building automation system (BAS). Found in high-tech manufacturing facilities, a BAS monitors and optimizes temperature, pressure, humidity, and flow rates while minimizing the energy use of fans, pumps, HVAC equipment, dampers, mixing boxes, and thermostats. Upon notification from the ESP of a DR event (either day-ahead or early the same day), a facility manager can order the BAS to curtail specific, predetermined loads, eliminating the need to manually adjust equipment.
Facility staff may need education about how to program the BAS to perform curtailment tasks. The existing BAS may also need to be retrofit to enable communication of the curtailment from the ESP to the BAS to the end-use equipment, unless the system already has this level of sophistication.
A 57,000-square-foot detergent manufacturing plant uses a spray tower measuring 80 feet tall by 14 feet in diameter in which heated air forces atomized liquid up the tower under high pressure, where it is then dried. Additional tasks within the plant include peripheral packaging and warehousing services. Pumps, 30- to 50-horsepower motors, and fans consume the bulk of electricity, and peak demand during the summer is approximately 450 kW.
This business participates in DR by scheduling the least energy-intensive jobs during peak demand periods. Day-ahead notification allows the vice president and production manager to plan curtailment activities in advance. They can often anticipate DR events based on the outside temperature. The plant starts production at 5:00 a.m. on curtailment days, an hour earlier than usual, allowing production to finish before the utility peak demand period begins at noon. Depending on the day’s business demands, facility operators are also able to curtail lighting in the warehousing and packaging divisions.
According to the facility’s owners, participating in DR has brought financial benefits without any negative effects on business. Every time the utility requests a load reduction, the plant has been able to comply. As a result of enrolling in the DR program, the facility saves up to $4,000 per summer on energy and demand charges, plus incentives are earned for participation. Because all curtailment strategies are manual, the facility incurs no extra expense.
In addition, the owners recognize that it’s in their best business interests to help maintain the integrity of the grid. Employees benefit because they miss rush-hour traffic by shifting their commute by an hour. They also avoid laboring during the hottest afternoons of the year. Participation in the program has netted the company an award from its utility and boosted employee morale.