Building a better, more efficient plant
Inside Machines: Variable frequency drives (VFDs), which can significantly impact energy efficiency goals by optimizing performance and reducing energy consumption by up to 50%, are among options in the U.S. Department of Energy Better Buildings, Better Plants Program.
According to the U.S. Department of Energy (DOE), the Better Buildings, Better Plants Program is a national partnership initiative to drive a 25% reduction in industrial energy intensity in 10 years, while decreasing carbon emissions and enhancing U.S. competitiveness. Led by the Advanced Manufacturing Office (AMO) within DOE’s Office of Energy Efficiency and Renewable Energy (EERE), the initiative is designed to encourage and recognize U.S. companies that are raising the bar for all manufacturing facilities by establishing and achieving ambitious energy efficiency goals. Among enabling technologies are variable frequency drives (VFDs), which can significantly impact the goal by optimizing performance and reducing energy consumption by up to 50%.
To date, 123 Better Buildings, Better Plants Program Partners are demonstrating their commitment to energy savings by signing a voluntary pledge to reduce energy intensity by 25% over the next 10 years. Collectively, these companies are showing that good energy management practices are good for business, good for the economy, and good for the environment.
The Energy Policy Act of 2005 defines energy intensity as the “primary energy consumed by each unit of physical output in an industrial process.” These units of physical output (also called units of production) can be the number, mass, volume, size, functionality or economic value of a product. In pledging to reduce their energy intensity by 25%, companies agree to establish an energy intensity baseline and track the change in energy intensity throughout their participation in the program. They also develop an energy management plan within one year of being a Program Partner with a blueprint for achieving targeted energy reductions.
In addition, Program Partners must designate a corporate energy manager who will be DOE’s point of contact for the partnership and annually report energy intensity and energy use data and achievements to DOE.
In exchange for their pledge, Program Partners have access to a technical account manager (TAM) assigned by DOE to organize and coordinate services. TAMs will help establish and analyze key energy use data and metrics for the development of baselines and plans. They will also identify emerging, energy-efficient technologies applicable to plant operations.
In addition, AMO and its partners will offer Program Partners combined assessment and training programs in plant settings. This includes guidance on how to identify and prioritize energy-saving opportunities, effectively implement and replicate energy-saving projects, and integrate assessments into an energy management strategy. Workshops are available on financing options, advanced technology, energy analysis software, energy management, and other topics. The program also offers Program Partners access to proven energy analysis software tools and other technical resources from DOE, states, utilities, and other partner organizations.
The Better Buildings, Better Plants Program gives national recognition to participating companies when they sign the pledge and achieve progress toward energy intensity targets. This includes a welcome letter from DOE, a feature on the DOE website, a congratulatory letter after achieving an annual improvement rate equal to or better than 2.5%, and a letter and plaque from DOE upon achieving the 10-year target.
Improving efficiency today
Companies that make the pledge to be a Program Partner have at their disposal a variety of actions to help achieve the energy intensity reduction goal. Insulation can be improved, leaks in compressed air systems repaired, motion sensors and energy-efficient lighting installed, and other enabling technologies introduced. Among these enabling technologies are variable frequency drives (VFDs), which can significantly impact the goal by optimizing performance and reducing energy consumption by up to 50%.
VFDs provide easy and efficient control of any device powered by an ac motor, including fans, pumps, compressors, hoists, etc. The resulting energy savings are tied to the technology and the fact that applications need less energy when idle or operating with partial loads. By varying the frequency of electrical current supplied to a motor, VFDs can reduce a motor’s rotational speed to match the workload more precisely, which multiplies energy savings and, through smoother control, reduces noise and maintenance and improves reliability. Controlling pressure also reduces losses in irrigation and distribution systems, conserving water. Customized programming enables a plant manager to determine what parameters are essential to their specific need.
To optimize VFD performance, plant managers can take advantage of a manufacturer’s commissioning service and maintenance programs. A professional start-up service includes a review of the drive installation, ensuring appropriate cooling clearances and connection integrity. Drives are then programmed for the specific application, enabling an organization to realize the full benefits of VFD technology. Customer orientation training may also be provided to help familiarize plant staff with the drive’s programming and operation.
Preventive maintenance ensures that equipment runs efficiently and safely over the course of its lifetime, saving energy, improving functionalities, and avoiding downtime and costly equipment failures. VFD parameters can be periodically adjusted for changing application requirements. Drive service professionals provide VFD services to enable organizations to focus their technical personnel on other core business operation activities.
In addition to the installation of VFDs, motor upgrades can help a plant achieve its energy intensity reduction goal.
For example, integrated motors and gear boxes are available, combining highly efficient permanent-magnet three-phase synchronous motor and an optimized bevel gear box. The drive helps to optimize plant productivity and increase energy efficiency. As a whole, the system can reach an efficiency level as high as 89%, yielding energy savings as much as 25% compared with conventional systems.
A compact integrated motor and gearbox can be used in transport and conveying systems, as well as machines and equipment. The drive has been designed especially for use in the food and beverage industry, although it offers significant benefits in all conveyor drive applications.
Compared to traditional systems, an integrated unit can cover many applications with one drive size and only a low number of variants, reducing spare part inventory. Uniform mechanical dimensions ease engineering, and depending on the application, plant managers can choose between two versions, one for use in dry and wet production areas and another for use in wet areas, areas with high cleaning intensity, and aseptic and clean room production areas.
By installing the drive, plant managers can realize longer service intervals. The drive system runs 35,000 operating hours in partial operation between oil changes (by using food grade oil). This means long service intervals, low maintenance cost and effort, and low operating costs.
Together, VFDs, high-efficiency motor upgrades, and other high-efficiency technologies can help plants successfully reduce energy use and operating costs. And, by participating in the Better Buildings, Better Plants Program, facilities can help shape tomorrow’s industry—spurring job creation and a stronger economy and contributing to a more sustainable environment.
VFDs reduce energy consumption in two operations
Real-world examples of the energy savings associated with the installation of VFDs include two very different operations: the Ste. Genevieve cement manufacturing facility near Bloomsdale, Mo., and the Gunn’s Hill Cheese plant in Woodstock, Ontario, Canada.
Operated by Holcim (U.S.), one of the largest suppliers of portland and blended cements and related mineral components in the United States, the Ste. Genevieve plant is the largest one kiln line cement plant in North America and is capable of producing more than 4 million metric tons of cement per year and 12,000 metric tons of clinker per day. Clinker is the critical mineral compound used in making cement.
The operation in Ste. Genevieve uses several fan motors, ranging up to 350 hp, to create the proper airflow in the cooler, where hot clinker is cooled from as high as 1450 C to 100 C. When initially installed, the motors used across-the-line starters, with dampers that applied full-voltage to the motor terminals at start-up, resulting in high start-up inrush currents. Additionally, the dampers were operating at less than 100% open for a majority of the year.
To increase overall efficiency, the company installed variable frequency drives designed to handle industrial applications on the fan motors. The variable frequency drives slashed the plant’s utility bill by enough to pay for the project in less than 2 years and reduced utility demand charges by reducing inrush current at start-up. In addition, for the second year in a row, the company received the U.S. Environmental Protection Agency’s Energy Star for Super Energy Efficiency.
At Gunn’s Hill Artisan Cheese, known for its handcrafted, Swiss-style soft, semi-hard, and hard cheeses, several variable frequency drives were installed in three areas—fluid pumps, the ventilation system, and the cooling compressor—to improve energy efficiency and control. Three VFDs were applied to drive the pumps used to off-load milk from the truck into the raw tank, transfer milk into vats and for washing, allowing the company to set three speeds without damaging the motors.
Another drive was applied to the reverse pressurized air handler that supplies the entire facility with 100% fresh air. As a result, the air handler only needs to supply make-up air to maintain the required positive air pressure in the plant. Another was used in a NEMA 12 enclosure to modulate the compressor in the outdoor chiller, reducing costs and providing a wide range of adaptability.
- Patrick Appleby is vice president of sales for the industry and food and beverage segments within Danfoss VLT Drives in North America. Patrick has 25 years of motors and drives experience in various roles such as inside sales, application engineering, product specialist, regional sales management, e-marketing, conventional marketing, and sales leadership. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering and Plant Engineering, firstname.lastname@example.org.
See linked article below on Gunn's Hill Artisan Cheese.
Also, DOE provides more information about the Better Buildings, Better Plants Program and how a plant can achieve its energy intensity reduction goal. www1.eere.energy.gov/manufacturing/tech_assistance/betterplants/
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