I've got a chemical plant in Charleston on AEP's Schedule IM rate and I'm trying to analyze their load profile to identify potential demand savings opportunities. The facility has pretty consistent baseload around 850 kW but there are these sharp 15-minute spikes up to 1,200 kW that happen 2-3 times per week, usually mid-afternoon. The plant manager swears they don't have any equipment that would cause such precise short-duration peaks. Anyone have experience with unexplained demand spikes in industrial interval data?
Appalachian Power load profile analysis - need advice
Wanda - those kind of sharp, short spikes in industrial facilities are often caused by large motor starts, especially if they're running older equipment without soft starters. Even a 200 HP motor can pull 6-8 times its rated current during startup. Have you looked at correlating the spike times with production schedules or specific equipment cycling? The plant operators might not even realize when certain motors are starting if it's automated.
Patty's right about motor starts being a common culprit. I had a similar case with an Omaha manufacturing plant where a 300 HP compressor was causing 400 kW demand spikes every time it cycled on. The solution was installing a soft starter which reduced the inrush current by about 70%. Paid for itself in demand charge savings within 8 months. You might also want to check if multiple pieces of equipment are starting simultaneously due to shared control systems.
Thanks Greg and Patty. I spent some time on-site yesterday with a power logger and found the smoking gun - they have three 150 HP cooling water pumps that all start within a 5-minute window when the plant temperature control system calls for cooling. The staggered startup is creating cumulative demand spikes that last just long enough to register in the 15-minute intervals. Plant manager had no idea this was happening since it's all automated.
Wanda that's a classic load management opportunity! You could probably save them $15-20K annually just by reprogramming the control system to start those pumps in sequence instead of simultaneously. Even a 2-minute delay between starts would spread out the inrush current and eliminate those demand spikes. I've seen similar savings in food processing plants with multiple compressor systems.
Marcus is spot on about sequencing the starts. I worked on a textile plant in Alabama that had similar issues with multiple air handling units starting simultaneously. We installed a simple load sequencer that staggered the starts by 90 seconds each and reduced their monthly demand charges by about $2,800. The payback was under 6 months. TVA even had a rebate program that covered half the equipment cost.
Albert that's great to hear about the TVA rebate program. I'll check if AEP has anything similar for demand management equipment. The plant is definitely interested in the sequencing solution after I showed them the potential savings. Those three pumps are costing them about $18,000 annually in excess demand charges based on the current billing rate of $12.50/kW.
Don't forget to factor in the load factor improvement when you calculate the savings. Reducing those demand spikes will improve their overall load factor which could qualify them for better rate schedules down the road. I've had clients save additional money by moving to time-of-use rates after improving their demand profile through better load management.
Elmer that's an excellent point about rate schedule optimization. This client's load factor is currently around 65% but eliminating those spikes could push it over 75% which would make them eligible for AEP's Schedule IP rate with lower demand charges. I'll run the numbers on both the immediate demand savings and the potential rate schedule benefits.
Great detective work Wanda! This is exactly the kind of forensic analysis that separates good auditors from great ones. Motor sequencing projects are usually easy sells to management because the ROI is so clear and the payback is quick. Make sure to document the baseline demand profile thoroughly before any changes so you can measure and verify the actual savings. Keep us posted on how the project turns out!
Thanks Randy! I'll definitely document everything carefully and post updates as the project progresses. The plant operations manager is presenting the sequencing proposal to executive management next week. Having the detailed interval data analysis really helps make the business case compelling. This forum is invaluable for getting insights from experienced practitioners like everyone here.