Fixed-Speed vs. VSD Air Compressors: Reducing Compressed Air Energy Waste in Aerospace Manufacturing
An aerospace manufacturer wanted to reduce the carbon footprint of a 30-building campus by reducing energy use. To do so, it contracted with Renew Energy Partners, which identifies opportunities and implements solutions under its energy-as-a-service model.
Fixed-Speed Air Compressors vs. Varying Compressed Air Demand
Renew Energy Partners helps industrial and commercial companies achieve their decarbonization goals by designing, installing and maintaining new equipment, entering into long-term financial arrangements with those customers to provide the funding.
One recent project started when Steve Pritchard, Managing Principal, met the head of the sustainability corporate council for an aerospace manufacturer at a conference. That chance conversation led to a project at the customer’s manufacturing campus in the Southeast. One building on the campus contained the manufacturing line, while other buildings contained preassembly and painting operations. In all, the campus included roughly 30 buildings, with a dozen used for product creation. The project’s goals were open-ended: See where the facility was wasting energy and come up with a plan to address those cases.
Steve Pritchard, Managing Principal, Renew Energy Partners.
The company began with a detailed audit of the full campus’s processes. The audit uncovered significant compressed air leaks, so the company brought in Edison Energy (now called Trio) an industrial sustainability service partner with expertise in compressed air system design. The service partner discovered the facility had two aging fixed-speed compressed air systems using load/no load controls, even though compressed air demand varied. The facility’s primary compressed air system served five of the buildings, while a distributed compressed air system served the others.
The audit also uncovered problems with the aging heatless desiccant compressed air dryer. It required excess purge air for regeneration, but due to repair issues still wasn’t properly drying the air. The moisture issues this created were most pronounced in the painting system.
Planning a Major Industrial Facility Improvement
Before the company began its work, the customer’s compressed air systems included three 365 cfm fixed-speed, lubricated, air-cooled, rotary screw air compressors and a heatless desiccant compressed air dryer requiring 60 cfm to operate.
“The audit was a three-day process,” Pritchard said. “We brought all of our standard, experienced engineers who cross both the mechanical and electrical sides of industrial operations. We generally start with an interview with key plant personnel as an introduction, and talk about how we're going to go about things. We gather any essential information. The customer dedicated one of its main facilities specialists to work with us. Because this was a defense contractor, we couldn’t walk around unescorted, so we had to have escorted access. The customer walked us through all 30 buildings on-site. We did a comprehensive review of the facilities, including all major energy-using equipment.”
Measurement and verification were completed by installing temporary metering devices and capturing 30 days’ worth of data. Measurements captured air compressor energy use, total scfm and system pressure at one-minute intervals.
“We completed a detailed review of its building management system and energy management systems, including looking at control logic for several different components and systems in the buildings,” Pritchard said. “We did a comprehensive review of lighting, variable-speed drives and the compressed air system. It was closer to a level two audit, given the time and effort we put into it. We then created a comprehensive audit report. When we presented the results, we looked for opportunities we could tackle under our energy-as-a-service model. We identified the investments we would make in new systems and equipment, as well as the savings that would come with those improvements. Then, we signed an energy service agreement with the customer.
“We completed this project in two phases. Improving the compressed air systems was in phase one. When you do something as big as a campus and identify so many opportunities, you have to figure out how to make it manageable, not because of capital investment, but because of resource investment on the facility side. Even now, there are still modifications which have to happen. Customers generally participate in the design review process, so you have to make it manageable for them, as well as for us. We found a natural break after the first phase.”
The purpose of the audit is to identify energy-reducing opportunities and determine the size of each opportunity. The company presents recommendations to the customer, and they decide together which opportunities are worth further work. The company then creates a detailed engineering study with design recommendations.
A VSD Air Compressor Manages Varying Demand
After studies were completed, the company solved the problem of varying compressed air demand by replacing one older fixed-speed air compressor with a new variable-speed drive, rotary screw air compressor, adding a sequencer and joining the two compressed air systems. The company recommended a 75 horsepower (hp), variable-speed, lubricated, air-cooled, rotary screw air compressor capable of delivering 345 cfm at 125 psig, to replace one of the three existing air compressors. The two older air compressors would meet the baseload compressed air requirements, while the new VSD air compressor would operate as a trim.
Solving the problem of insufficiently dry air meant replacing the aging heatless compressed air dryer with a new heatless desiccant compressed air dryer. It was capable of providing a -40°F (-40°C) dew point for 275 cfm at 100 psig The new model’s purge management controller and improved valve design made it a more energy-efficient choice.
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The company installed a 75 hp, variable-speed, lubricated, air-cooled, rotary screw air compressor.
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A new heatless desiccant compressed air dryer solved the problem of too much moisture in the compressed air stream.
The work done included a compressed air leak survey, then leak repairs. “The typical process for compressed air leak surveys is doing a walk-through of the site with ultrasonic sensing equipment, walking the compressed air piping system and identifying leaks through noise,” said John Luleich, Vice President, Project and Asset Management. “Based on the compressed air system pressure and the level of noise, the survey can determine the leak size and the leakage rate. Those are all logged and tagged in the field, and then we're provided a quote for repairs. Depending on the customer, sometimes they'll take on some of the repairs themselves, or we'll coordinate the repairs with a service vendor. Typically, you can monitor the actual compressed air use before the compressed air leak repairs, then compare the measurement with a measurement taken after the repairs are done.”
John Luleich, Vice President, Project and Asset Management, Renew Energy Partners.
Teaching Customers the Importance of Ongoing Maintenance
One thing the company tried to impress upon this customer was how achieving energy savings isn’t a one-time fix. Yes, the company could implement changes and make repairs, but new problems would creep in if regular maintenance was neglected. During its leak detection audit, the company identified 82 compressed air system leaks with 129 cfm of compressed air waste. Compressed air leaks ranged from 1.0 to 3.7 cfm at operating compressed air pressures of 112-115 psig. A successful overhaul meant not only repairing those leaks, but also teaching the maintenance staff how to prevent and repair new ones.
“The maintenance staff, as you can imagine, for a facility that big had a lot on its plate. They have a lot in the work order backlog,” Pritchard said. “Being able to help them not only identify leaks, but then identify a solution to prevent the leak from happening again was our focus. Whether it meant replacing a failing valve, modifying the compressed air piping system at a particular location or changing the kind of compressed air connection they had, all of those were on the table as we looked at individual leaks and addressed them.”
Why would a large and successful manufacturer need to work with an outside company to help with decarbonization and financing? It’s a question Pritchard hears often. For big corporations, capital is focused on delivering products for customers. Even when manufacturers identify equipment opportunities for saving energy, the initiatives have trouble getting funding. For many, it’s more expedient to work with a third party able to recommend and make improvements, and then finance the upgrade over time. Using outside capital becomes the best way for some to move sustainability and efficiency goals forward.
In a post-project study, the company determined it saved this customer 125,500 kWh per year through compressed air system leak repairs, 113,000 kWh per year by adding a VSD air compressor and 33,600 kWh per year by substituting a more efficient heatless desiccant compressed air dryer.
Renew Energy Partners“Renew Energy Partners is an onsite energy, clean energy and energy efficiency company formed to remove the twin roadblocks of tapping into energy-efficient technology for the commercial and industrial sector in the United States,” explained Steve Pritchard, Managing Principal. “We provide the solution to two problems we've seen primarily with commercial customers. The first one is the complexity of energy efficiency or clean energy projects. It's not a customer’s core business, usually, and so we try to bring to the table turnkey sets of solutions. We also address capital needs. We design, build, own and operate assets and improvements, fund those assets and then sign long-term energy-as-a-service contracts – including power purchase agreements and thermal energy purchase agreements – with customers. We do everything from soup to nuts. “We started in 2013 when this was an evolving, nascent industry. We set out not to be a supplier of a single energy efficiency solution, like lighting-as-a-service, because typically commercial customers don't come to us and say, ‘We'd just like you to replace the lights.’ They're looking for a broader set of solutions to address energy efficiency and carbon reduction. That's the sweet spot of our mission. “The company started from a connection I had with my co-founder, Charlie Lord, and our other co-founder, Doug Foy. Doug and I had worked together in state government, but Doug had also done a lot of consulting work on the energy efficiency side for cities. We identified this gap in the uptake of energy efficiency and energy-efficient technologies on the commercial and industrial side. “How do we address that? How do we get the commercial and industrial industry to tackle what was a robust amount of energy that had the potential to be reduced? The company was formed out of that idea. It was a formation of only three individuals to start with. We had the right disparate backgrounds to create what I think is an interesting, exciting and valuable company. “We work with commercial and industrial clients. We work in the manufacturing industrial sector, healthcare, hospitals, multifamily, hospitality and even education. We'll look at all sectors on the commercial side. The biggest indicator is how much energy they use and what kind of opportunity there is for us to reduce their energy use, improve their cost structure and reduce their carbon footprint. “One of our primary focuses has been the automobile industry, but we're also in retail and consumer goods, and that group continues to grow. We support not only the main manufacturers in the auto industry, but also the host of suppliers supplying those facilities. All of those facilities tend to be big and have multiple suppliers, and the suppliers themselves tend to be pretty good-sized companies with manufacturing facilities of their own where they provide components. We’ve worked with defense contractors as well, and that’s a focus of ours. “We have a team of 15 people. We don't have a team of in-house design engineers; we have a team of project engineers who are the project managers and executors of individual projects, but we rely heavily on a lot of our design-build strategic partners to facilitate getting projects done, and then we rely on partners on the operations and maintenance side. “We have a robust asset management side, because once we build something, we're in it for the long haul. The contracts we sign with customers tend to be 10 or more years. We own the assets, we maintain the assets and we make sure they deliver on the expectations we started with.” For more information, visit https://renewep.com.
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