Industrial energy conservation, “Where does the reasoning begin?”, as one of my engineering professor’s would say. Most industrial plants today have “low hanging fruit” opportunities that can readily be identified and will deliver quick payback with small investments. Industrial energy conservation has become a big topic with a wide range of products, technologies, and services being promoted to save energy in industrial and process plants that can be overwhelming. Many technologies, including sophisticated optimization to increase the energy efficiency of plants and processes, can be complex and expensive. Another component of an ongoing energy conservation program is sub-metering energy use, energy dashboards, and benchmarking that are useful tools and are being recommended as a first step by many automation suppliers. The majority of first step energy conservation measures only require common sense and basic engineering knowledge. Many plants are better served by first pursuing a basic energy conservation program to identify actions that save energy quickly.
As with any other project, you need to develop an understanding of the opportunities and challenges and then develop a plan. Starting with a basic program will put you and your company on the path to increasing energy efficiency and getting early results that build credibility with management to do more in the future. The information and basic steps described here should help you get started on the path to saving energy.
Economics
Energy costs in most industries are likely the most uncontrollable raw material cost for manufacturing or at a minimum in the top three raw material inputs that directly impact production profits. The U.S. Energy Information Administration report, International Energy Outlook 2011, predicts world energy use to increase 117% from 2008 to 2035. Energy has not typically been on the production bill of materials, but this is a growing trend. Savings generated from energy conservation drops directly to the bottom line increasing profits. The other economic impact is environmental, which more companies are considering important for social reasons, and in a growing number of countries, there is a surcharge for carbon dioxide emissions. A simple example illustrates the impact: It takes approximately 394 pounds of coal to keep a single 100 watt incandescent light bulb burning for 12 hours each day for a year. Burning the coal to produce this energy creates 936 pounds of acid rain causing 1,000 pounds of carbon dioxide and 7.8 pounds of sulfur dioxide. In addition, 90% of the energy consumed by the incandescent bulb is given off as heat rather than light.
These are the steps to start an energy conservation program and identify “low hanging fruit” opportunities.
Get management support
Management support is an essential ingredient of the action plan to allow you to be proactive in going after opportunities to identify and make improvements. At this stage, the goal is to get enough management buy in to pursue basic energy-saving measures to have successes that prove the value of energy saving investments. This will illustrate the potential cost and productivity advantages of energy projects and build credibility with management to pursue more aggressive energy efficiency program later. Starting with a simple profile of overall energy use for your facility provides a basis to interest management, illustrates the size of the opportunity, and the baseline from which to measure your overall progress. Get the energy bills for electricity, natural gas, and fuel oil for the last year, and determine your total annual and monthly energy costs by fuel type. The U.S. Department of Energy notes as much as 1.6 to 3.2 quadrillion Btu could be saved by improving the efficiency and reducing energy losses in industrial systems (10-20% reduction in energy use). Energy conservation investments should be treated as another way to improve profits.
Form an energy team
Energy teams in manufacturing facilities identify energy-saving opportunities, develop an energy plan, and implement cost-saving measures. Energy teams should include members from plant and process engineering, maintenance engineering, procurement, and production since energy systems are part of the fabric of a plant.
Energy conservation basics
Orienting the team to thinking about the sources of energy and fundamental ways to save energy is important before doing a plant walk through to identify energy conservation opportunities.
Energy sources used by plants are sometimes referred to as W.A.G.E.S., and this is a convenient way to remember major energy categories namely, water, air, gas (Natural Gas, other gases or fuels), electric, and steam. Throughout a plant, energy sources are transported and used in the production process. The main categories of basic energy conservation are eliminating losses, matching supply to demand, and increasing equipment efficiency.
- Eliminating losses
Eliminating energy losses is the most fundamental energy conservation strategy that is not glamorous but is generally low cost and high payback. Consider a simple water leak of one drop per second = 1 cup every 10 minutes, consumes over 3,200 gallons (12,000 liters) a year.
- Load matching
Existing plants and processes generally have a number of opportunities to match the required output of equipment to the production need. When energy was lower cost, many machine and process designs and operating procedures were not optimized. For example, on a project in a wire mill at a steel plant, the set points for large oil heaters used in the process were set significantly above the required temperature. A simple lowering of setpoint and adding an automatic change to a standby setpoint when the process was not in run mode had significant savings.
- Efficiency retrofit
Simple replacement of basic energy consuming devices with newer technology can save energy. Using more efficient light bulbs, sometimes requiring fixture changes, is a straightforward change to save energy. A bigger investment that can lower energy consumption and lower maintenance cost is replacing existing motors with NEMA Premium Efficient or EISA-compliant motors to decrease power consumption. In many cases, smaller-size motors can be used increasing the savings since the motors on existing equipment in many cases were larger than required. Some utility companies even offer incentives to customers who install new motors and gear drives. The government has been mandating minimum efficiency levels for motors manufactured in the U.S. since 1997 originally under the Energy Policy Act (EPAct), and now under the Energy Independence and Security Act (EISA). After EPAct was implemented, motor manufacturers began improving their efficiencies beyond the minimum requirements, so the National Electrical Manufacturers Association (NEMA) developed its own standard to identify motors that exceeded the mandated levels. Recognizing the industry’s ability to meet an elevated set of standards, the EISA mandated all motors manufactured after 19 December 2010 must meet NEMA Premium Efficient standards. A complete list of NEMA Premium Efficient standards is available at www.nema.org.
Walk through
Doing plant walk throughs to identify potential areas for improvement and the equipment that uses the most energy in your plant is a valuable use of time. In many plants, a minority of the equipment accounts for the majority of energy consumption. Things to look for include large pieces of equipment and equipment that runs most of the time or that runs periodically but use substantial energy. Tell people in the plant you are on a hunt for energy wasters and ask for ideas. Today it is easy to use a digital camera, video camera, tablet computer, and/or digital voice recorder to take comprehensive notes. Based on this information, a plan can be put together for energy saving measures.
Target area examples
These are examples of potential areas to save energy.
- Compressed air
Compressed air is an essential energy resource within industries. The efficiency of a compressed air system starts at the compressor and stops at the point of use. Losses due to leakages within the pipework can cause extreme and completely unnecessary costs and reduce the efficiency drastically. Leakages are a constant consumer of compressed air 365 days a year. Over the years, compressed air systems often get extended with different materials being used, pipe diameters that are not optimal, and poor installation practices. Tracking down leaks is a detective job, and making all plant personnel aware of the issue and requesting they report suspected leaks will help. Monitoring air compressor operation during plant shut down time can provide insight into compressed air leakage issues.
- Steam
According to the U.S. Department of Energy, more than 45% of all the fuel burned by U.S. manufacturers is consumed creating steam. Steam is used in many production processes and for building heat and electricity generation. Steam is not free; it costs a great deal of money to feed the boilers generating the steam. Steam is a very efficient way to transport heat energy, and it is easily moved in pressurized piping systems that can deliver that energy at manageable costs.
When steam gets to its point of use and gives up its latent heat to the environment or to a process, it condenses into water, which must be returned to the boiler for reconversion to steam. Faulty steam traps are a large energy waster. Steam traps are valves designed to remove condensate as well as air from the piping system. Steam traps can fail open or closed creating problems. There are a number of technologies available to detect faulty steam traps including thermal and ultrasonic devices. Devices are also available to continually monitor steam traps and report status over industrial networks or more recently over wireless communications making them easy to install.
Thermal imager devices can also be used while steam systems are in operation to scan steam transmission lines for blockages, identifying closed valves, leaky steam pipes, blocked heat exchangers, and various boiler issues.
Consider creating a regular inspection route that includes all key steam-system components in your facility that are inspected at least annually.
- Pumps
Pumps are used widely in industry to provide cooling and lubrication services, to transfer fluids for processing, and to provide the motive force in hydraulic systems. Since they serve such diverse needs, pumps range in size from fractions of a horsepower to several thousand horsepower. Common maintenance items to improve efficiency include bearing lubrication and replacement, mechanical seal replacement, and packing tightening and replacement.
Conservative engineering practices often result in the specification, purchase, and installation of pumps that exceed process requirements. Engineers often decide to include a margin of safety in sizing pumps to compensate for uncertainties in the design process. Anticipated expansions in system capacity and potential fouling effects add to the tendency to specify pumps that are “one size up” from those that meet system requirements. The cost of oversizing pumps extends beyond energy bills. Excess fluid power must be dissipated by a valve, a pressure-regulating device, or the system piping itself, which increases system wear and maintenance costs. There are five common indications that a pump is oversized: excessive flow noise, highly throttled flow control valves, heavy use of bypass lines, frequent replacements of bearings and seals, and intermittent pump operation.
Pumps that experience highly variable demand conditions are often good candidates for a variable frequency drive (VFD) to regulate motor speed to match the pump’s output to required levels. The principal advantage of VFDs is better matching between the fluid energy that the system requires and the energy that the pump delivers to the system. As system demand changes, the VFD adjusts the pump speed to meet this demand, reducing the energy lost to throttling or bypassing excess flow. The resulting energy and maintenance cost savings often justify the investment in the VFD. However, VFDs are not practical for all applications, such as systems that operate high static head pressures and those that operate for extended periods under low-flow conditions.
- Insulation
Anything that has insulation that is aging is a source of energy loss; prime examples are chilled water and steam pipes. Un-insulated steam distribution and condensate return lines are a constant source of wasted energy. Insulation frequently becomes damaged or is removed and never replaced during steam system repair. Water damage commonly creates insulation damage caused by leaking valves, external pipe leaks, tube leaks, or leaks from adjacent equipment. Any surface over 120°F should be insulated, including boiler surfaces, steam and condensate return piping, and fittings.
Develop a strategy
The final step is to create a strategy for sustaining plant-wide efforts to improve and maintain the efficiency of your energy systems. Keep staff motivated to achieve savings at your plant through monthly or bi-monthly meetings of the energy team, tracking and reporting on your energy and cost savings, and periodic reassessments of equipment and opportunities. Once areas for saving energy in one plant are identified, they can generally be replicated in other plants.
Reference: http://www.isa.org/InTechTemplate.cfm?template=/ContentManagement/ContentDisplay.cfm&ContentID=88538
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