Brainstorm: Energy Efficiency
This feature originally ran in the November/December 2010 issue of Food Manufacturing.
The Food Manufacturing Brainstorm features industry experts sharing their perspectives on issues critical to the overall food industry marketplace. In this issue, we ask: What is the most overlooked factor food manufacturers should consider in order to make their facilities more energy efficient?
Don Giles, Director of Sales, Processing Division, Heat and Control, Inc.
Millions of BTUs of unused heat escape every hour up exhaust stacks from fryers, heat exchangers, ovens and other equipment in food processing plants. This wasted exhaust heat can be captured by systems so it can be reused for processing, sanitation and heating the workplace in order to provide more energy efficiency. Examples of such systems include:
- Booster Heaters. Mounted over the stack of most any heat exchanger, booster heaters use normally wasted exhaust gases to preheat cooking oil and increase heat exchanger efficiency by up to 10 percent.
- Stack Heat Recovery Systems. Recover heat from fryer exhaust stacks by condensing steam to make hot water for sanitation, blanching, boiler feed water or even heating buildings.
- Combustion Air Preheat Systems. When high-temperature air is introduced into a burner, less fuel is required for combustion. Combustion air preheat systems utilize normally wasted exhaust heat to reduce the energy usage of a heat exchanger and increase its efficiency up to 4 percent. Additional modules can be added to further increase the overall process efficiency by preheating make-up cooking oil, air and water.
- Pollution Control Heat Exchanger. As our KleenHeat heat exchangers heat cooking oil, they also incinerate and remove odors, oil vapors and other particulates from fryer exhaust that would normally pollute the air and area around plants.
Loic Moreau, Business Segment Manager, New Business for LEM
It may sound obvious, but simple energy monitoring is typically overlooked. Routine food manufacturing processes like heating, cooling, mixing and others are typically extremely energy intensive, and thus present tremendous opportunity for efficiency improvements and cost savings. Often, merely taking a deeper look into the details of your energy usage can reveal relatively quick and easy ways to reduce consumption.
For example, when manufacturers are unaware of their facilities’ energy usage during peak demand periods, they can wind up paying unnecessarily high utility bills. Or, sometimes the equipment itself runs inefficiently due to factors such as age, condition or location, and minor repairs or replacements might make a significant dent in the facility’s energy consumption. Additionally, some projects keep motors or heaters running continuously, even though they are only required for part of a production cycle.
Manufacturers can improve many of these inefficiencies by simply monitoring and gathering energy consumption information over a short period of time. Electric sub-metering, for instance, provides visibility into a site’s greatest efficiencies and energy losses. By monitoring usage in this way, manufacturers can identify opportunities to save an average of 15-20 percent on energy costs by:
- Verifying the accuracy of utility bills
- Allocating energy costs to specific departments of processes or customers.
- Assigning accountability to energy users
- Determining benchmark equipment and system efficiency
- Identifying performance problems in processes and equipment
With this kind of insight, manufacturers can develop and implement corrective action to drive down energy waste—like reallocating energy consumption from peak demand periods to off-peak periods or reducing run-time for machines that do not need to run constantly—tailored to their specific facilities and applications.
James Rauh, Cooling Water Product Manager, Garratt-Callahan Company
The utility plant is the heart of any food processing facility. Whether it is steam used for sterilization, pasteurization or sanitation, or cooling used for refrigeration, the facility cannot operate without it. Over the past several years, cost cutting measures have, in many instances, taken dedicated operators out of the utility plant. Because processing equipment maintenance issues usually take priority over the operation and testing of steam generating and cooling equipment, they are consequently neglected. With the costs of both energy and water rising today, there are potentially many areas within the utility plant that can produce significant energy savings and extend equipment life.
Improperly operating boilers and cooling equipment can result in significant energy losses:
- Leaking pipes and steam traps result in loss of water and also Btu’s of heat energy.
- Leaks in condensate return systems likewise waste water and Btu’s.
- Not maintaining proper burner settings results in wasted fuel and increased energy costs.
- Improper chemical feed results in deposits which retard heat transfer resulting in increased fuel usage in boilers and electrical consumption in compressors and chillers.
- Operating with lower than desired cycles of concentration wastes water, Btu’s and chemicals.
- Not performing general housekeeping on cooling towers or evaporative condensers can increase fan motor electrical costs, and accumulation of sludge can foul heat transfer surfaces.
- Lack of a properly applied and maintained microbial control program in cooling equipment can lead to loss of heat transfer with increased electrical costs and potential for equipment damage.
- Failure to maintain chemical feed and control equipment can result in corrosion or severe fouling of equipment, both of which consume extra energy and eventually may require production shutdown for cleaning, repair and possibly replacement.
- If onsite waste treatment operations are not operated properly, excessive water losses can result and opportunities for recycling wastewater for reuse may be overlooked.
While individually these may not seem significant, in total they can have a major impact on a facility’s energy efficiency. Placing a full time hands-on person over operation and maintenance of the utility plant can potentially result in finding and correcting the above examples of inefficient conditions in the facility.
New technology developments can also significantly benefit an operation. A qualified water treatment service company can survey your entire facility looking at all potential opportunities for water and energy savings. A summary energy audit will demonstrate potential energy savings and calculate the ROI that can be achieved.
Tim Wray, Professional Engineer and LEED Accredited Professional, KJWW
System commissioning is an often overlooked strategy that increases the energy efficiency of a facility. By verifying that energy-saving design measures and plans are actually functioning and performing as intended, owners can realize real savings. All too often money is spent on great energy-saving ideas, but in the rush to get the plant online, the control systems are not finalized. It is our experience that not enough time is allotted in the construction process to verify proper operation of equipment, controls and processes.
An integral part of commissioning is training — both for facility manager and operators — to ensure their understanding of systems and how they work. One example is lighting controls that are based on occupancy sensors. By setting the occupant sensitivity and duration, lighting energy consumption can be reduced by 5 to as much as 40 percent, depending on area usage. Lighting controls that are based on the production schedule can reduce lighting during off shifts or weekends. Additional energy can be saved when the facility manager understands the system and updates controls as production schedules change.
Oftentimes there is equipment that does not require full exhaust airflow at all times, and by placing these units on variable frequency drives (VFDs), a facility can realize cost savings from reduced energy usage. Reducing the amount of exhaust results in less outside air flowing through air handling units (used to offset the exhaust and pressurization), which results in less energy used to temper the outside air. Without balancing and verifying systems and their operations, the cost savings may not be realized.
Existing facilities also will benefit from commissioning and identifying opportunities for retrofitting of energy-saving equipment or controls.
Rowan Sanders, Director of Marketing and Communications, Veolia Energy North America
Energy efficiency solutions that are often overlooked by food manufacturers, but which should be strongly considered, are combined heat and power (CHP) and district energy.
CHP is the simultaneous production of electricity and heat, which results in the consumption of much lower volumes of fossil fuels than using separate technologies to produce heat and power. Whereas traditional power plants release a great deal of waste heat to the environment during the fuel conversion process, CHP plants recycle the waste heat and convert it into useful energy.
District energy is the local production and distribution of thermal energy (heating or cooling) to nearby buildings. Manufacturers may use the principles of district energy to distribute the heat and power from CHP to all of their buildings. With an onsite central CHP plant, food manufacturers can have highly reliable and efficient energy assets dedicated to providing their critical requirements, while also lowering regional emissions.
District energy can meet the thermal energy needs of food manufacturers in the form of steam, or hot and/or super-heated water for all forms of the cooking, separation and preservation processes. These systems also meet the requirements for safety-critical chilling, for food processing production and distribution facilities and for achieving cold chain continuity.
By implementing a CHP and district energy solution onsite, manufacturers are typically able to produce heat and power while consuming 40 percent less fuel. Another advantage of CHP is that it enables fuel flexibility. Biomass waste by-products of a manufacturing process can also serve as potential sources of fuel.
By reducing a large food processing facility’s reliance on the electric grid, CHP can also provide significant benefits to the state or region by relieving congestion on the local electricity grid. It is for this and other environmental and economic reasons that the U.S. Department of Energy has publicly recognized the potential for CHP in the food processing industry.
Food manufacturers that take advantage of these proven solutions can increase their reliability, control their costs, minimize their operating risks, increase their energy efficiency and reduce greenhouse gas emissions.
Paul Humphreys, Vice President Communications and Branding, Atlas Copco Compressors
When considering ways to make a food manufacturing facility more efficient, managers often focus their efforts on how to minimize the use of the big three utilities: water, electricity and natural gas. However, compressed air production, the fourth utility, is often overlooked at a great expense.
According to the Assessment of the Market for Compressed Air Efficiency Services issued by the U.S. Department of Energy, compressed air accounts for 10 percent of all electricity use in U.S. manufacturing. Even within the most efficient compressed air systems, only 10 to 15 percent of the input energy is ultimately delivered as compressed air. When leaks, inefficient design and inappropriate uses are included in the equation, energy waste becomes astounding; estimates indicate that poorly designed and maintained compressed air systems in the United States account for up to $3.2 billion in wasted energy usage annually.
Thankfully, there are simple steps managers can take to save their facility significant money. The first step is a compressed air audit. A careful examination of a facility’s compressed air system will likely reveal several opportunities for reducing the plant’s energy draw, resulting in significant energy savings, lower operating costs and a minimized impact on the environment through a smaller carbon footprint.
The next step for managers is understanding the production and usage of compressed air. The largest component of wasted energy in the process of manufacturing compressed air is heat loss. Heat recovery is an option offered now with most compressed air packages and recovery of around 90 percent of the input electrical energy is often the norm and far from the exception. Leaks feed artificial demand and turning up the pressure to compensate for the pressure loss only results in feeding more air to the leaks. Depending on pressure requirements and energy costs, a single ¼-inch leak in a compressed air line can cost a facility from $2,500 to more than $8,000 per year. Locating and fixing leaks throughout a facility’s compressed air system will result in significant savings.
Additional savings can be attained through proper system management and maintenance, and using the latest technological advancements. For instance, taking advantage of variable speed drive technology, which matches the production of compressed air to the actual demand, can reduce costs by around 35 percent. Plant managers should also look at inappropriate uses of compressed air; for example, applications where a low pressure blower might be better suited to an application than a compressor.
Sam Gladis, Business Director-Heat Pumps, Vilter Manufacturing
Energy costs are a major concern of any food producer. One of the most overlooked factors that food manufacturers should consider to make their facilities more energy efficient is waste heat recovery.
Most processing facilities use refrigeration systems for blast and spiral freezers, chillers, processing rooms, and cold storage. The heat removed by the refrigeration systems is usually dumped to the atmosphere as wasted heat. At the same time, facilities are paying for fossil fuels to heat water for processing and clean up. The enormous amount of wasted heat from the refrigeration system can be efficiently recovered and used to meet the hot water needs of the facility.
Waste heat recovery on this scale was not possible just a few years ago because the temperature of the rejected heat was too low to be used directly. Now, low-grade heat can be economically recovered and raised to a useful temperature with ammonia heat pumps and single-screw compressors.
Heat pumps are widely used in commercial and residential HVACV applications to harness heat. The cost of electricity to run a heat pump is much lower that the cost of fossil fuels to heat water, because of the inherent efficiency of the refrigeration cycle to move heat from one location to another. Producers can use a lot less fossil fuels in their boilers if they capture the heat they paid for, rather than throwing it away to the atmosphere.
Facility managers focus on payback and the long-term energy savings, and include energy rebates and efficiency incentives in the decision. A waste heat capture system will pay for itself quickly and continue to save money for many years.
Recent screw compressor design improvements are what enable these new high-pressure heat recovery systems. Using a single-screw compressor heat pump with ammonia, waste heat can be captured and converted very efficiently to heat water up to 195°F. Even if the captured heat cannot provide all of the water heating needed, it can still offload the boilers by preheating the water and feeding it to the boiler.
To use ammonia at temperatures and pressure required for large heat pump applications, the screw compressors must be able to handle a minimum of 750 psia at 195°F. The unique Vilter single-screw compressors with cast steel housings are designed for 1100 psia at 230°F. This allows the compressor to generate higher condensing temperatures, producing water up to 195°F.
Ed McGovern, Vice President Sales & Business Development North America, PIAB
Vacuum technology is one area of the production process in which manufacturers can significantly reduce energy use. New energy-efficient pumps, ejectors and generators work at lower pressures, to help avoid flow losses. For example, Piab’s piINLINE™ COAX-based vacuum ejectors can reduce energy consumption by 50 percent compared to traditional technology.
Another technological advance that improves energy efficiency in the use of vacuum technology is the incorporation of lighter materials into machinery. Exchanging metal for high-tech plastics in the construction of machines and robots, for example, means they can be reduced in size, and require less energy to operate.
Although it is relatively small, the suction cup itself can also pack a big punch in terms of energy savings. Enhanced sealing capability, even on non-smooth surfaces, means less flow capacity is needed from the system to get a strong grip on handled objects. Suction cups built to collapse and return easily allow smaller pumps to be used to complete the task, contributing to additional energy savings. High-quality cups also provide greater lifting power compared to conventional alternatives, meaning fewer cups are required and less energy is used. One example is Piab’s recently launched modular piGRIP™ suction cup that allows manufacturers to choose the ideal combination of lip and bellow so packaging lines can handle products at previously unprecedented speeds while realizing energy savings.
Manufacturers also have choices when it comes to the set up and design of their vacuum systems. Where centralized vacuum technology creates considerable pipe losses and transporting vacuum systems require significantly more energy, decentralized systems can be an energy-efficient alternative. Less transporting of vacuum is needed, lowering loss of vacuum through the pipe. Adding to this, smaller pumps and ejectors can be used with a decentralized system, requiring less energy, and enabling significant savings. Manufacturers can also consider the use of cartridge systems, which allow integration closer to the point of use and further reduce flow losses.
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