If your manufacturing process is well into its middle age, you might recall a time when your facility’s utility bills were a passing irritation rather than the chronic pain they are today. On the positive side, you have a range of solutions you can implement to reduce water, gas, and electricity usage. Here, we’ve described a few proven strategies that result in significant savings with the added benefit of attractive payback terms.
Thermal processing plants use great amounts of water for both processing and cleaning. It typically comes from city water systems and often needs to be heated, which runs up costs on two different utility bills. By installing recirculation systems, you can reuse the cooling water. In one such system, the emersion water used to cool cans is recovered and piped to heat exchangers where it is indirectly cooled in a cooling tower. When necessary, the water is cooled further using chillers. The water is then returned to the process. These systems can be extremely cost effective. SSOE installed one in a Midwest food plant that used two million gallons of water a day. The company was able to payback the cost of its system in 2.5 years for a 40% ROI.
In older plants that use furnaces or ovens in their processes, the heat is often simply released into the atmosphere. If the system can reclaim the heat and direct it to where it pre-heats water or air to be used at another point in the process, you can save appreciable energy. In one thermal processing plant, city water was used for cooling via a heat exchange system, but the resulting hot water went down the drain. By adding a recirculation cooling loop, SSOE reduced the cost of water and sewer. Going one step further, the cooling water is now being piped to a heat exchanger to pre-heat the ingredients at the front end of the process. Recapturing the heat saves a significant amount of natural gas. Thanks to both systems, the company is saving $500,000 a year for a 40% ROI.
In many manufacturing plants, cleaning equipment and production lines for changeover is a water-intensive operation. Companies who use low-pressure washers may find high-pressure washing actually uses less water because it takes less time. Aside from saving utilities, a quicker washing process also reduces costly downtime—by as much as 75% in some cases.
If your industrial process still runs on traditional motors and valves rather than variable frequency drives (VFD), it’s time to reassess your reasons for not converting. You may be missing an opportunity to save electricity at a very reasonable total cost. VFDs adjust the speed of the motor electronically so they always run at the most efficient speed for the process. Fixed speed motors, on the other hand, are typically sized for worst-case scenarios: for extreme temperature conditions or loads. Since motors are less efficient when lightly loaded, these motors squander electricity.
When VFDs first came out they were considered expensive specialty equipment. Now that they are widely used, the systems themselves cost less, require less maintenance, and they permit removal of valves that require periodic service or replacement. Paybacks range from 18 months to 3 years. Although VFDs have been available for some time, many manufacturers have not yet made the conversion for various reasons. For some, due to the critical nature of the process being controlled, shutting down for retrofitting can involve more risk than simply replacing existing equipment. A good alternative is to first test VFDs on a small operation so you can fine tune the start-up to plan ahead for replacement of major systems during the next scheduled shut down.
One often-overlooked potential source of savings is the utility meters themselves. For relatively low cost, you can install independent meters to validate the actual usage of steam, natural gas, and water against the meters that calculate billings. Why pay for such redundancy? To verify billings for one. For example, a cereal manufacturer that purchased process steam from an adjacent sister plant installed an independent steam-flow meter at the entrance to the plant. They learned they were being billed for up to twice as much steam as was actually delivered.
In addition, installing benchmark meters shows what it costs to run individual production lines, facilities, and operations as a whole—in real time. Independent metering of two lines running side by side can reveal information about equipment reliability and the need for maintenance. Benchmark metering is also an excellent way to compare how operating at different times of the day affects utility costs. It can open up opportunities to reduce costs through demand-side management and off-peak usage.
Successful energy-saving strategies are as much about people as they are about equipment or systems. When the people running or working in the plant are serious about saving energy, they will be proactive about finding and implementing solutions. Invariably, large-scale systems are going to require vigilance and regular maintenance so they can deliver the highest reduction to your utilities. You’ll want to demonstrate that energy-savings is a priority and back it up procedurally to receive the greatest benefit from your investment.