Lines are shut down. No one’s in the plant-except for the energy thieves. Look around. Conveyors are running but moving nothing, their noise masking whistles and hisses escaping from ineffective pneumatic shut-off valves, leaky joints and air lines while compressors work overtime to feed the leaks. Plant lighting is up bright. A/C is, ah, so comfortable at 67°F. Hot water drips from “shut-off” cleaning systems. Fans and blowers circulate air. Pumps maintain pressure. Steam emanates from unknown sources.
Energy consultants have seen this tableau again and again. “I can generally tell within 15 minutes whether a plant has the opportunity to save substantial dollars or if they’re on top of their game,” says Paul Miles, manager of marketing technical services, PECO. Miles came to the Philadelphia-based utility as an internal energy consultant for Nestlé, where he was responsible for finding ways to cut energy costs at individual plants and labs around the country. Now he consults with industrial and commercial customers to help them save costs on energy.
“When you walk into a plant where everything is in its place, you don’t hear a lot of background noise (hissing, leaking air lines), and you don’t see equipment running unattended,” Miles adds. Unfortunately, he says, plant workers are so close to the energy wasters, they don’t even notice them. Of course, while large pumps and blowers can waste electricity if they’re not sized properly or controlled by variable frequency drives (VFDs), compressed air is the one utility people use as though it were free.
Bill Martin, program manager for Rockwell Automation’s Power and Energy Management Solutions Group, tells the story of an ice cream plant whose maintenance department affixed a 1/8-inch jet of air to each packaging machine to prevent a carton’s flap from jamming the feed system. This annoyance should have been addressed by the machine’s vendor, or could have been fixed by a small, dedicated fan mounted at the application. Multiply this compressed air usage times six machines, and watch how the cost of compressed air increases, too!
Martin also analyzed a pizza manufacturer’s air usage and found it to be consuming 600 cfm when all the equipment was shut down. Doesn’t sound like much? Energyideas.org computes the cost per cfm at about a penny per hour with an average-size compressor (18 kW/100 cfm) at an electric utility rate of five cents per kWh. So the cost at 10 cents per kWh (closer to Philadelphia rates) would be about $.02 per cfm, or 600 x $.02 = $12/hour, or $105,120 per year.
“Once upon a time,” says Peter Dalgity, senior automation engineer, manufacturing and milk supply at major New Zealand dairy company Fonterra, “no one cared about saving energy.” Dalgity says that with fast-rising energy costs, a good energy management program is common sense. So much so that Fonterra began a company-wide effort in 2003 to reduce energy consumption by 10% per unit of output by 2008/09. Its 28 manufacturing plants and 16,000 employees have been able to achieve this reduction in two years working with Rockwell Automation.
At Fonterra, where an enormous part of the operation relies on drying-turning liquid into powders-the price of energy is a major concern. To harness energy usage, Dalgity moved an employee out of production and made him energy champion for 12 months. This person spent a year reviewing reports and monitoring energy usage. Now that he’s back in production, he continues to monitor energy usage and is saving energy on a daily basis.
WAGES cost!WAGES, an acronym for the five utilities (water, air, gas, electricity and steam) is key to an energy action plan, says Jim Plourde, Schneider Electric national business development manager. This plan is a stepwise approach on paper to an energy management plan before the physical process of energy management begins. A typical energy action plan starts with a thorough analysis of all utility systems and culminates with a prioritized plan of action. Plourde says this plan cannot be outsourced; it is an iterative process that, to be done effectively, requires collaboration of both system owners and energy experts.
According to Martin, once a plan is formulated, an infrastructure can be put in place to create an energy management system. The system provides three key functions: monitoring, analyzing and controlling. Often, systems are put in place to address the monitoring function with a goal toward expanding the system to include analysis and control later on. Therefore, it’s important to plan systems that are both flexible and scalable.
Plourde says that some processors may already have many of the basic data gathering tools installed. Examples include SCADA and process automation systems and traditional energy management systems such as a metering or monitoring package. And, of course, manufacturers have a utility system, which may or may not be automated. Processors will want to maximize efficiency by bringing all the relevant data to one interface where energy usage can be measured, modeled and verified, to provide continuous tracking in real time.
In setting up a system, Dalgity found several of his plant’s existing energy monitors weren’t very accurate. They might have been OK at one point for a few readings, but wouldn’t provide the results for a large-scale energy management solution. After replacing some of the old equipment, Dalgity wired 34 manufacturing areas in the plant and came up with an interesting conclusion: Comparing product output to energy provides a metric that can be used to troubleshoot problems. For example, evaporator product output varied from one day to the next. The cause: The evaporator’s setpoint was set differently so more steam was required, or the evaporator had a leak, requiring more energy to keep vacuum in the evaporator. With an energy management system in place, Dalgity finds it easy to overlay energy use against a process state in any area of the plant, so it becomes very apparent when an area of the plant has energy usage and no product output. “We can tell if the plant is being managed and operated correctly just by the amount of energy we’re using.”
Water, water everywhereWhile water may be relatively inexpensive to acquire, the costs of pumping it and getting rid of wastewater can make it an expensive utility. According to Ivan Spronk, Schneider Electric’s manager of AC drives, pumping water or any fluid and controlling it with valves may present an opportunity to save energy. Why not decrease the speed of the pump when not as much water is required? Of course, the amount of energy savings will depend on several variables including motor size, pump type, flow pressure or volume, etc.
Using VFDs to control pump/motor speed has another potential advantage. For processors who incur penalties from their utility for low-power factors caused by several motors on the system, VFDs present a neutral-power factor contribution to the electrical distribution system. Therefore, capacitor banks are not required to correct low-power factors.
Northern Foods decided to install VFDs on three of its 75 kW motors that pump chilled water to refrigeration units at its Riverside Bakery in Nottingham, UK. Soft-start control panels had been used for 22 years, and Engineering Manager Vernon Humphries was looking for a turnkey solution to lower energy usage. Inverter Drive Systems, an ABB Drives Alliance partner, removed the soft-start panels and supplied three 55 kW ABB industrial drives in the control panels along with an analog temperature sensor that monitors the return temperature as a feedback signal. When the return water temperature is high, the pumps speed up and supply additional coolant; when the temperature drops, they slow down. Average power reduction for each of the pumps was found to be 65.2%, which translates into a cost savings of about $60,000 per year, and an ROI of 10 months.
For a casein application, Fonterra Dairy can use as much as three million liters of water per day just in washing the curd. Then there’s the water content of the milk itself. While the wastewater can be used on the farm for irrigation, it’s not clean enough to put into the river unless it’s processed further. This same issue was also true for a US pork producer that was paying fines to a public treatment system for exceeding its National Pollutant Discharge Elimination System (NPDES) permit levels for biological oxygen demand (BOD), fats, oils and grease (FOG) and total suspended solids. GE Water & Process Technologies conducted a site survey and concluded an entrapped air floatation (EAF) system licensed from Stewart Water Solutions Ltd. could effectively address these issues. Upon final testing, the processor was able to meet all governmental effluent regulations.
Air supplyThe typical compressed air system has about 10% efficiency from “wire to work.” No wonder compressed air is expensive. While preventing leaks and non-essential uses of compressed air is vital, VFDs on compressor motors can also make a difference-just as in pumping water. There are many variables, so it can be difficult to make an accurate prediction of energy savings. But when a supplier promises energy savings in excess of 50%, it may be too good to be true.
Martin recommends that facilities with several compressors put in a real-time optimization system for compressed air. For example, if a processor has two large compressors and a smaller one, the system will look at the real-time needs of the plant and know the efficiencies of each of the compressors, making certain the appropriate compressor runs at the right speed. It’s no longer necessary to control air usage by the “telephone method,” i.e., when users run low on air, they call and ask operations to put more compressors online.
Fossil fuelsGas (or other fossil fuels) can be used for several tasks: generating steam, heating the premises, powering refrigeration compressors, running a cogen plant and more. Because a processor will typically have only one gas supplier from which to choose, many opt to have boilers that can run on both gas and oil, depending on what the rates are at any given time.
Martin Michael, vice president at Advanced Automation, notes that excluding raw materials, 70% of manufacturing costs are in energy. The use of fossil fuels to power boilers for steam generation accounts for about one-third of the total US manufacturing energy consumption, and almost 80% of the boilers are nearly 30 years old or more. An efficient 10-tons-per-hour (TPH) boiler averages $135,000 per month in fuel consumption. A minor inefficiency of 1% can cost about $2,400 per day or more than $72,000 per month, resulting in $800,000+ per year in lost manufacturing costs.
Boilers today may or may not have control systems that are set up to maximize steam output while minimizing energy input. This can be especially true for plants with multiple boilers where the telephone method is used to put additional boilers online.
Michael says processors could benefit from an intelligent boiler solution capable of managing the load balance across multiple boilers to maximize the efficient use of each boiler in combination with the others. Such a solution would give plant engineers and boiler operators real-time information as well as advanced analysis algorithms to improve maintenance and identify and eliminate problems. The solution should also provide expert outside services on a regular basis.
Smarter electricityWhile conserving electricity in the plant is essential, DOE is cosponsoring with utilities and other companies an initiative called GridWise that over the next 10 to 20 years will do for the electrical grid what plant networking systems have done for industrial automation. Invensys Process Systems Technology Officer David Hardin explains that the primary charter of GridWise (www.gridwise.org) is “to drive interoperability in the smart grid as we use information technology in building a market-based and intelligent electric system.”
By electric system, Hardin means both upstream and downstream. Expect to see distributed generation systems coming online; these systems will be comprised of smaller systems often based on renewable energy, and eventually cogen (cogeneration) systems that can feed energy back to the grid. The downstream side will be a dramatic change for consumers. Right now, processors are “loosely” connected to the grid and receive price breaks if they’re willing to shed power when contacted by the utility. In a tightly coupled system, processors’ plant electrical systems will be in continuous contact with electrical providers on the grid. When there is a need for a reduction in consumption in a specific area, utilities will contact their customers in real time over the network, and a processor’s energy management system will make a choice to cut back somewhere and receive a reduced rate, or continue to use energy at an elevated rate.
Hardin, a member of the GridWise Architecture Council, says there is much work to be done, especially in determining how contracts will work and what the rate structures will be. “The idea is to have a tighter integration between a manufacturing facility and the electric system. Intelligent energy management systems running inside a plant will be able to react to pricing that can vary in real time relative to the demand or peak pricing that exists now, e.g., day-ahead pricing, ever finer-grained, real-time pricing. Systems will be able to react to pricing variations and provide intelligent responses to electrical system issues. So event reaction and real-time pricing are two areas that will be very important.”
Steam heatAccording to DOE, conventional steam boilers lose most of their efficiency with hot combustion gases going up the stack. Eric A. Kessler, eastern region sales manager for Clayton Industries, suggests adding a recovery system at the stack to reclaim lost heat. He says a recent study of 66 major steam plants showed 12.3% of fuel consumption is avoidable. Still, while payback averaged 1.7 years, only one-third of the plants implemented any improvements. Other areas of concern for boiler efficiency include:
n Under identical conditions, fuel oil fires at efficiency levels 2.5-3% higher than natural gas
Running hot and coldOvens and freezers can be energy wasters, but they don’t have to be. Ramesh Gunawardena, FMC FoodTech manager of technology and process development, says there can be energy loss at the ingress and egress of an oven, but there are methods, such as steam knives, to contain the heat. Steam knives are analogous to air curtains in doorways. Where he most often sees loss, however, is steam leaking off the stacks of a series of boxes, which typically indicates a misuse of steam. Also key to saving energy is a properly designed cooking process that makes optimal use of energy. He adds that while gas-fired ovens have been the norm in the bakery, indirect heating can often provide better containment and energy efficiency.
With freezers, there may be more energy saved in the refrigeration plant than in the freezer itself, says Ingmar Pahlsson, FMC freezer product line manager. Creating a slight pressure differential can be used to keep external air outside the freezer. High-efficiency fans also use less power and generate less heat to be removed by the refrigeration plant. In addition, a liquid/gas separator can be installed so only gas is returned to the plant.
In the plant, other basic approaches can be taken. For example, Pacific Gas and Electric’s energy consultants helped Busseto Foods expand its operation and designed energy-efficient steam and refrigeration systems. The new system allowed expansion while saving 671,000 kWh, 19,000 therms and $87,000 in annual energy costs. Two evaporative condensers with floating head pressure control using a variable setpoint control strategy and variable speed control for the fans were used in the cooling plant. The condenser fan motors are rated at 92.4% efficiency, and with a specific efficiency of 358 BTUH/watt, the condensers are 8.5% more efficient than standard units.
For more information:
Ramesh Gunawardena, FMC FoodTech, 419-627-4315, email@example.com
David Hardin, Invensys, 508-549-3362, firstname.lastname@example.org
Eric A. Kessler, Clayton Industries, 610-913-6290, email@example.com
Bill Martin, Rockwell, 414-382-3061, firstname.lastname@example.org
Paul Miles, PECO, 215-841-4141, email@example.com
Martin Michael, Advanced Automation, 610-458-8700, ext. 257, firstname.lastname@example.org
Ingmar Pahlsson, FMC FoodTech, +46-42-490-4000, email@example.com
Jim Plourde, Schneider Electric, 603-265-6556, firstname.lastname@example.org
Ivan Spronk, Schneider Electric, 919-217-6330, email@example.com