Electric utility incentive programs encourage industrial and manufacturing companies to reduce power consumption by paying part of the cost to upgrade to more efficient equipment. It’s a great concept, but many customers only go after low-hanging fruit, such as upgrades for lighting or air compressors, and go no further.
But don’t ignore vacuum. When a vacuum system is centralized, operates at uniform pressure plant-wide, and employs cutting-edge technology to match production with demand, the energy savings can quickly pay for the upgrade. Utilities are typically willing (and often eager) to provide businesses with financial incentives so efficiency upgrades pay for themselves even sooner.
This story looks at a vacuum system upgrade project completed by a Pennsylvania-based manufacturer of decorated packaging. The customer uses vacuum primarily for pick-and-place operations, such as feeding tin or aluminum sheets into printing, stamping and forming machines. Vacuum operates continuously 24/5, although during peak demand periods it runs 24/7. During normal operations, workers set up a production batch, run the process, then break it down and set up the next batch, run the process, and so on. Material and process variables are involved in making different products, so there are fluctuations in vacuum demand.
The previously installed vacuum system included two 30 HP (22 kW) water-cooled vacuum pumps (one running full-time, the other a spare), and one 16 HP (12 kW) water chiller, for total installed horsepower of 46 HP (34 kW). After the upgrade, the vacuum system now includes one 20 HP (15 kW) Atlas Copco GHS 900 VSD+ air-cooled vacuum pump with Variable Speed Drive. Power savings were achieved by a reduction in installed horsepower of 26 HP (19.4 kW), as well as improved pump performance that enabled a plant-wide reduction in vacuum pressure from 25 in Hg to 21 in Hg.
These efficiency improvements reduced the customer’s annual power consumption from 177,752 kWh/yr to 57,660 kWh/yr, a savings of 120,092 kWh/yr, or 68 percent. The utility rebate, based on $.06/kWh, totaled $7,205.52 and effectively doubled the first year’s energy savings. The upgrade to Variable Speed Drive technology paid for itself in just over a year when compared to the cost of a fixed speed vacuum pump replacement.
Significantly, the entire cost of operating and maintaining the water chiller was eliminated by upgrading to an air-cooled vacuum pump. One existing pump and the water chiller were kept online as backup so production is won’t be interrupted if the new pump is offline for service.
The entire cost of operating and maintaining the 16 HP (12 kW) water chiller was
eliminated by upgrading to an air-cooled vacuum pump.
Enabling Efficiency Upgrades
Electric utilities welcome projects that reduce power consumption because they reduce the need to expand production capacity to meet increasing market demands. This customer’s power supplier, PPL Electric Utilities, considers rebates for vacuum system upgrades under their Custom Incentive Program. CLEAResult, a PPL partner that serves customers across 29 counties in central Pennsylvania, facilitated the customer’s vacuum upgrade project to ensure that it complied with the program’s guidelines and qualified for the rebate.
“Too many people don’t want to mess with something that isn’t broken or that works well enough, and they close their eyes to technology that works better and saves money,” said Bud Fogleman, Senior Market Outreach Specialist for CLEAResult in Wyomissing, PA. “Very often discussions about efficiency upgrades start with lighting and progress to compressed air, and that’s great, but now we are starting new conversations about vacuum. We’d like to see even more.”
While PPL’s Prescriptive Incentive Program offers set rebates for specific equipment upgrades, their Custom program calculates upgrade incentives individually through measurement and verification. “When a custom project is identified, we collect metering data on the existing equipment to use as a baseline,” Fogleman explained. “We look at conditions as they exist and then project the estimated savings created with the new equipment so we’re able to reserve funds for the project incentive. The project is cleared, installation takes place and when it’s complete we collect metering data with the new equipment and compare that to the baseline. We actually go a step further, when possible, and collect actual production data to normalize for vacuum usage over an entire production year. We have done several vacuum system upgrade projects to date and other projects are in the works right now.”
Key Project Considerations
When there is one vacuum pressure requirement plant-wide, it is possible to centralize the system to take advantage of production efficiencies and energy savings. “With a uniform pressure requirement across the plant with constantly changing demands, a centralized system with a Variable Speed Drive vacuum pump can provide a substantial reduction in operating costs,” said Eric Slaymaker, Sales Manager for Atlas Copco Compressors LLC Oil-free Air Division in Reading, PA. “That’s the approach we took with this customer.”
To justify the investment in more efficient equipment, the customer conducted a technical analysis with the help of Atlas Copco. “Our team performed a V-Box analysis on the customer’s vacuum systems,” said Slaymaker. “The V-Box is a data logger that captures power consumption data. We installed it on the existing vacuum system, which literally took only a couple minutes, and let it collect data for a week while the customer ran their process normally. Using that data, we ran computer simulations of pressure function and power, and compared the performance and efficiency of existing equipment to the proposed upgrade.”
With hard evidence to validate reduced electrical consumption, CLEAResult secured the utility’s commitment for a financial incentive to support the project. Once the new equipment was operating, Atlas Copco installed the V-Box and logged energy consumption data for the new vacuum pump for two weeks. Using this actual production data, the utility calculated the customer’s reduction in power consumption as 120,092 kWh/yr, and paid the incentive of $7,205.52, based on $.06/kWh.
Vacuum Pump Efficiency Gains
The rotary screw element in Atlas Copco’s vacuum pumps is fundamentally the same as the one in their rotary screw air compressors. It actually runs in the same direction, but the outlet and inlet are switched. Instead of pulling air in to compress it, air is pushed out to form vacuum.
Though compression and vacuum systems share some characteristics, their approaches to efficiency are distinct. To appreciate why, consider that the horsepower curve for vacuum is the continuation of the horsepower curve for compressed air. As the curve transitions from compression into vacuum, the horsepower requirement continues to drop because the air contains fewer and fewer molecules. This creates a challenge in operating efficiency for a vacuum pump because the highest horsepower requirement comes at atmospheric pressure, when the system is first turned on, and then decreases as vacuum pressure increases.
Consider a system that needs a 20 HP vacuum pump to start up. A fixed-speed pump must provide that power level initially, but then it continues to operate at the same speed even when less than 20 HP is needed to provide the required flow at the required pressure. When demand decreases, a fixed-speed vacuum pump typically runs unloaded, but still consumes up to 80 percent of the energy of a loaded pump. That energy is wasted.
Atlas Copco’s Variable Speed Drive technology automatically varies the speed of the vacuum pump to match demand and manages vacuum pressure at the outlet head so flow remains constant. This capability reduces energy consumption. That savings, along with a utility rebate, makes the investment in a more efficient vacuum system pay for itself quickly.
Atlas Copco GHS 900 VSD+ Vacuum Pump installed and operating at customer location.
“Atlas Copco views vacuum as a huge energy saving opportunity,” said Slaymaker. “A fixed-speed pump has to cover the worst case, but Variable Speed Drive has significant turndown capability and matches production with demand. That also means a customer can size a new vacuum pump for future growth without having to pay the ongoing operating expense for that reserve.”
With the Atlas Copco VSD+ pump operating, the customer was able to reduce vacuum pressure plant-wide from 25 in Hg to 21 in Hg. “The customer arrived at that figure by reducing pressure one step at a time to determine the minimum pressure that would satisfy all user demands plant-wide,” Slaymaker said. “At 21 in Hg, they could keep everyone happy.”
Reduced Sound Level
The previous vacuum pumps were open machines with extremely high noise levels. The Atlas Copco pump operates much more quietly, plus the equipment is surrounded by a compact, six-sided enclosure. As a result, the sound level is dramatically reduced compared to the previous system. “Sound level didn’t drive the purchase for this customer,” according to Slaymaker, “but they did want it to be quieter. They’re happy with the reduction in sound, absolutely.”
“Upgrading a vacuum system isn’t rocket science, but it takes people who understand how vacuum works and who offer equipment to deliver vacuum more efficiently,” said Slaymaker. “When Atlas Copco works with customers who appreciate the value of investing in the best technology, and with organizations like CLEAResult that help make the investments pay for themselves even sooner, together we help customers improve their production technology. Before this vacuum project began, this customer already received a rebate for a compressed air upgrade earlier in the year through CLEAResult that resulted in a 772,693 kWh/yr reduction and an incentive in the amount of $46,361.58, so we did not have to sell the concept of power savings. As soon as this customer started up the new vacuum pump, like the new air compressor, they started bringing money back into their company. The new pump has cutting-edge technology that’s much more energy efficient. It has a new warranty, it’s quieter, and it’ll be more reliable. Best of all, someone else is helping them pay for it.”
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