Today’s quest for energy- and cost-efficient machinery was the driving force behind Aerzen’s endeavor to combines the technology of a positive displacement blower with a screw compressor together in one unit. With 145 years of experience behind it, Aerzen accomplished this feat by building the Delta Hybrid rotary lobe compressor with extremely satisfying results. This unique combination of technologies utilizes the company’s experience in the design and production of rotary lobe blowers, which it’s been building since 1868, and screw compressors, which it’s produced since 1943. The concept offers new possibilities for generating positive pressure or vacuum in a variety of applications. “By applying screw compressor technology to low-pressure air compression, we’ve greatly improved efficiency,” said Pierre Noack, President and CEO of Aerzen USA. The Delta Hybrid has seven patents or patent applications, making it one of the most innovative products in compression technology.
Energy Efficiency, Reduced Life Cycle Costs (LCC)
Over a 10-year operating period, energy costs equate to about 90% of the total life cycle costs (LCC) of a compressor. “Around three years ago, the realization of just how much the industry was spending on energy costs emerged as a major consideration when purchasing equipment, “ said Noack. “And less energy consumption results in less greenhouse gas emissions.” To meet the demand for energy-efficient equipment, Aerzen looked at the problem from every angle to analyze the big picture. “The solution depends on each individual client and their application and can integrate a combination of products,” said Noack. “We consider how we can get the highest efficiency out of the existing situation, taking into account the reality of the customer’s operation. Many manufacturers claim their products can save money, but the only way to know is by analyzing the real operating conditions including operating times at various loads, winter and summer, considering system aging and fouling as well as drive efficiency under these varying conditions. We show exactly where the cost savings come from and provide background information as to how we got there [see case study below].”
When building its completely green facility at its U.S. headquarters, Aerzen hosted a design charette—a week-long roundtable discussion for all of the pre-selected architects, contractors, consultants, everyone involved in the project. “This integrated approach to design improves communication and allows us to be creative—one idea can stem from another, which is not possible with a traditional fragmented approach,” said Noack. “The end product resulted in a building that uses 50% less energy and offers better working conditions. This also is how we approach the design of our products; we take the most valuable input from a variety of sources and combine it in the best possible way.”
Case Study Proves 30% Energy Savings in WWTP
After testing and refining the Delta Hybrid in Europe for four years, Aerzen debuted it in the United States last October at WEFTEC®, the Water Environment Federation’s annual conference, in New Orleans, LA. Following the introduction, the Huntingdon, NY Wastewater Treatment Plant (WWTP) agreed to conduct a side-by-side test of the Delta Hybrid and its two-year-old existing blower system. This provided the first opportunity to demonstrate the machinery in the U.S. wastewater market place. The town had been searching for a solution to the high energy costs of plant’s current system and frequent mechanical failures that the manufacturer could not resolve, so Plant Supervisor John Pavlik agreed to design the comparison test and serve as the technical field consultant for the analysis.
Prior to testing, plant operators began collecting operating data from the existing blowers in August 2010 to set a baseline. The Delta Hybrid was installed next to the existing blower in November, and two power demand meters were attached to measure kilowatts used hourly and at peak demand. Operators recorded readings four times daily for two months, as well as checked blower pressures and temperatures. Numbers showed a 28%-29% daily energy reduction, a 30% peak demand reduction, and a 45o F cooler temperature in the Delta Hybrid. “We were actually shocked at these numbers and even double-checked them,” said Pavlik. “The peak demand, which is the maximum amount of electricity a unit uses to start, numbers also differed greatly. The existing units used 85 peak kW vs. 58 peak kW in the Delta Hybrid (28% less). This is significant, as Long Island Power Authority (LIPA) monitors and charges us for that peak (guaranteed) amount.”
Aerzen also introduced a new remote monitoring system for the Delta Hybrid, which allows it to track data and trends via Internet connection. “The system monitors the inlet and discharge temperature, vibration, speed, and oil temperature as well as the inlet and discharge pressure to help us provide real-time results to the operators,” said Tom McCurdy, Northern USA Regional Manager, Water and Wastewater Blower and Compressor Sales. “Officials at Huntingdon WWTP were thrilled to advise town residents of the projected cost savings these initial results showed.” Projections showed an annual savings of \$79,320 for the plant, a two-year payback.
Expanded Operating/Pressure Ranges
As blowers are one the biggest consumers of electricity in a wastewater treatment plant, proper selection, considering sizing, range of flow, and pressure for a particular application, is critical on the front end. In all cases, engineers try to ensure that the plant has sufficient capacity to meet the maximum load performance, even on the hottest and most humid day. “To cover this base and account for hypothetical future population growth, engineers sometimes have to implement oversized systems that can’t efficiently handle the current operating conditions of the plant,” said McCurdy. “I have seen many cases where blowers have been installed in wastewater plants that can handle 100,000 gallons of water per day, and they process only 30,000 gallons per day. Most blowers are not designed for such a turn-down range and waste a lot of electricity when operating at the low end, especially if excess air needs to be vented.”
The current cost per kWh and the predicted increase in energy costs are strong motivators pushing companies to rightsize systems. The Delta Hybrid has the capability of operating within a 4:1 range, allowing for a more efficient process and requiring less electricity overall to operate. “A wide turndown capability is crucial in different phases of wastewater treatment, as factors such as the influent load and temperature outside can affect the amount of air needed,” said Noack. “The combination of the screw compressor technology to the low-pressure rotary lobe blower application provides the ability to adjust the air flow to achieve the highest level of efficiency even at the low end of the range.” The Delta Hybrid expands the reliable operating range of low-pressure positive displacement machines. It comes in two internal configurations to achieve best performance in the most needed pressure range: a 3+3 twisted rotor profile is used for low pressures up to 800 mbar (12 psi), whereas a 3+4 rotor profile is used for pressures up to 1500 mbar (22 psi). Most wastewater treatment plants require 8 psig or more pressure and benefit from a 3+4 screw rotor configuration because the internal compression it produces helps to increase the compression efficiency. Moreover, all the package components are designed and configured to integrate all the benefits.
For applications such as wastewater treatment and food industries, the cooler operating temperature of the Delta Hybrid provide one of its most advantageous features. “Many membranes and diffusion systems, particularly in the wastewater treatment application, are made of synthetic materials that can age prematurely when exposed to higher temperatures,” said Noack. “As the Delta Hybrid operates at a lower temperature, the system materials maintain their performance over a longer period of time, which also contributes to lower the energy usage. Moreover, the absence of any absorption material in the silencers of the Delta Hybrid downstream to the inlet air filter eliminates migration of fibers or particles and partial clogging of the diffuser pores, which would altogether defeat the purpose of investing in an energy-efficient machine.”
In addition to providing significant energy and cost savings, testing at Huntingdon WWTP showed that the Delta Hybrid holds its ground in fundamental areas such as reliability and durability, maintenance costs, economy of space, ease of handling, and noise level. “Our current units require an oil change every 400-600 hours (4-6 weeks), while the Delta Hybrid requires a change every two years, reducing costs dramatically,” said Pavlik. According to Noack, the belt-drive technology is the simple beauty behind the design. “It is very simple, self-tensioning, 97% to 98% efficient, and it enables to optimize the driver speed, regardless of whether the machine is used with an adjustable speed drive (VFD) or not. It provides versatility and adaptability to different applications,” he said.
The modular, compact design of the Delta Hybrid allows multiple units to sit side by side, saving space while offering ample access for maintenance, although it did not require much according to Pavlik. He also pointed out that the unit is relatively quiet compared to others. When running with the acoustic enclosure open, he noted that although workers still had to use hearing protection, such as ear plugs, other units require use of double hearing protection, such as plugs and ear muffs.
Aerzen USA Corporation
Founded in 1983 and located in Coatesville, PA, Aerzen USA is a wholly-owned division of the German manufacturer Aerzener Maschinenfabrik GmbH, a recognized world leader in the production of rotary positive displacement blowers, compressors, and vacuum pumps since 1868. The company has 1,700 employees working on all continents with 7 sales offices in Germany, some 40 national and international subsidiary companies, and further representations in more than 100 countries.
For more information on the Delta Hybrid, visit www.aerzenusa.com.