Microbreweries: Reducing energy costs through high-efficiency fan motors

by Katie Daniel | March 12, 2018 2:19 pm

HORIZONS
By Cheryl Higgins
Annually, breweries in the United States spend more than $200 million on energy[1], which is equal to three to eight percent of the production costs of beer. Surprisingly, microbreweries can consume as much as twice the energy per barrel of finished product as large breweries. They also have narrow profit margins, which makes energy efficiency measures a particularly effective way to save money and increase turnover.

Energy usage varies among brewpub operations. However, food preparation and HVAC consume the greatest amount. Typically, energy is viewed as a fixed expense—but, it is an easily controllable operating cost. With prudent energy efficiency investments, such as space-saving rooftop HVAC systems with high-efficiency fan motors, breweries are able to lessen energy costs and consumption while reducing their carbon footprint.

High-efficiency chiller systems and craft breweries
Few industries have seen as much growth and evolution in the past 30 years as craft breweries. This growing sector has changed the purchasing and drinking habits of many beer lovers. Energy management has become a major priority for brewery operators. As they have grown from hobbyist scale to more commercial significance, craft brewers have taken a growing interest in sustainability, particularly in terms of energy use. As production has increased in scale, energy efficiency has also become a more important financial consideration.  (Click here[2] for additional information on energy costs.)

In general, the brewing process involves:

• mixing (or ‘mashing’) malted barley and other grains with high-temperature water;
• draining the resulting liquid, or wort, off the mashed grains;
• boiling the wort while adding hops and (optionally) other spices;
• cooling the wort; and
• adding yeast and letting the mixture ferment
  at a temperature that is best suited to the strain of yeast that is the best employed.

Once the wort has fermented, bottles are cleaned and filled with the resulting beer and packaged for delivery. Depending on the brewery, beer may be cellared or kept in cold storage before distribution. (For more information, click here[3].)

Refrigeration is a necessity in most breweries. Often, separate refrigeration systems are operating within a single brewery. Refrigeration costs can contribute to more than 30 percent of a brewer’s electrical consumption. (For more information, click here[4].) With energy prices already high and continuing to rise, paying attention to factors affecting efficiency, such as the chiller system, can pay big dividends. High-efficiency brewery chillers with PMAC fan motors—providing higher torque—can help reduce energy costs.

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Self-contained HVAC systems
About half of all U.S. commercial space is cooled by self-contained, packaged air-conditioning units—including air-handling fans and sometimes also gas or electric heating equipment—sitting on rooftops.

There are a number of ways to achieve efficiency in the rooftop units, from adding coil surface to applying the latest compressor technologies (e.g. scroll, twin-single, and staging compressors) or equipping them with variable speed advances.

Highly efficient fan motors, the heart of HVAC equipment, are also extremely important to rooftop unit efficiency. Most of a rooftop’s power consumption is from the compressor, followed by the supply and condenser fans. However, because the fans run to provide ventilation even when the compressor is not on, they can account for up to 45 percent of the equipment’s energy use.

Increasing rooftop unit efficiency not only reduces energy use, but also lowers peak usage time (i.e. power used during the hours when the energy grid suffers the greatest strain), which supports better energy management for the facility and lessens environmental impact.

PMAC motors
The permanent magnet alternating current (PMAC) motor is traditionally a more complex construction than the standard induction one. The design has been simplified by using powerful permanent magnets to create a constant flux in the air gap, thereby eliminating the need for the rotor windings and brushes normally used for excitation in synchronous motors. This results in the accurate performance of a synchronous motor, combined with the robust design of a standard induction motor. The equipment is energized directly on the stator by the variable-speed drive.

Benefits for HVAC retrofits
One example of PMAC benefits can be found in commercial HVAC retrofits. In certain centrifugally loaded variable-speed applications (e.g. pumps, fans, and blowers), PMAC motors boost efficiency—and, in many instances, can direct-drive these designs. Fans are unique as they are typically sized by torque, yet direct-driving PMAC motors can eliminate the need for belts, pulleys, and sheaves. With power transmission devices like gear reducers simplified or removed, one can see increased service life of the entire drive system. Reduced maintenance is particularly helpful at buildings where fans are installed on roofs.

Motor-driven components used in HVAC and refrigeration are the highest energy consumers in both the residential and commercial sectors. (Click here[6] for more information.) In the commercial segment, the combined HVAC and refrigeration categories account for 93 percent of motor-driven energy use. Clearly, both refrigeration and HVAC applications offer an excellent opportunity for helping reduce energy consumption.

For almost all equipment types in both the residential and commercial sectors, the market is transitioning to permanent magnet motor technology. This technology is becoming increasingly cost-effective—upgrading to a PMAC motor typically delivers a payback in just 12 to 23 months with a noticeable reduction in monthly utility bills. This motor type also offers other non-energy benefits, such as reduced noise and the ability to reach higher rotational speeds.

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Advantages of PMAC motor
Standard induction motors are not particularly well suited for low-speed operation as their efficiency drops with the reduction in speed. They may also be unable to deliver sufficiently smooth torque across the lower speed range. This is normally overcome by employing a gearbox. Utilizing a PMAC motor with an external drive eliminates the need for a gearbox and saves space and installation costs, since the foundations just need to be prepared for a single piece of machinery. This also gives more freedom in the layout design. (Click here[8] for additional details.)

The PMAC motor can deliver more power from a smaller unit. They are suitable for variable- or constant-torque applications. The drive and application parameters dictate to the motor how much torque to produce at any given speed. This flexibility makes PMACs suitable for variable-speed operation requiring ultra-high motor efficiency.

Currently, PMAC motors cannot be used in washdown places (e.g. food processing plants) or in an application requiring explosion-proof motors. Also, anything requiring more than 6000 revolutions per minute (RPM) will not work with a PMAC motor. Additionally, these motors always require an AC inverter to run, which adds to the cost.

A standard AC induction motor does not require an inverter unless the speed needs changing. For many customers, the technology of a PMAC motor is too new, costs more, and they do not see the payback as quickly as they would like. Also, if it is an original equipment manufacturer (OEM) application, the customer most likely has to recertify the equipment for Underwriters Laboratory (UL), Canadian Standards Association (CSA), or similar agencies.

Higher productivity
Advanced PMAC technology can improve system performance using a radial permanent magnetic design that minimizes any rotor loss, significantly reducing operating temperature and vibration. When a PMAC motor is matched with a variable-frequency drive (VFD), the combination helps optimize mechanical systems to achieve the maximum output and lowest total cost of operation.

PMAC motors provide:

• higher efficiencies achieved across a speed range;
• greater torque capabilities;
• greater power density; and
• more lightness than AC induction motors in a comparison within the same horsepower (HP) range.

PMAC motor speed is limited by back electromotive force (EMF)—voltage opposing the current that causes it—because the latter increases directly with the motor speed. The motor is connected to the electronic drive and its electronic components are designed for a maximum voltage above the rated drive voltage. Normally, the motor and controls are designed to operate well below the maximum voltage of the components. However, if motor speed exceeds the design speed range—either being powered from the control or being driven by the load—it is then possible to exceed the maximum voltage of the drive components and cause failures. VFDs are capable of limiting motor back EMF when operating properly. However, if the drive faults and loses control during speeding, it cannot protect itself.

Conclusion
Industrial brewing chillers are an efficient way of quickly cooling wort as well as maintaining the temperatures in brite and fermentation tanks. The process of heating and cooling the wort is critical to the success of craft beer. It is crucial the chiller operates quickly and efficiently to lower the wort back to the ideal temperature.

Today’s craft breweries are making great strides in reducing their energy consumption and costs, and in implementing the latest technologies and practices for efficiencies. This is achieved through the use of chiller systems equipped with high-efficiency PMAC motors. These motors, in comparison to the AC varieties, significantly reduce operating temperature and vibration, provide higher efficiencies achieved across a wider speed range, and offer greater torque capabilities as well as increased power density.

Cheryl Higgins is product marketing manager with Leeson Electric, a manufacturer of various electric motors, mechanical and electrical motion controls, and power generation products serving markets all around the world. She is responsible for new product development and training, and has more than 35 years of industry experience managing technical and applications teams. Higgins can be reached at cheryl.higgins@leeson.com[9].

Source URL: https://www.constructionspecifier.com/56450-2/

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