My 87 year old, Sicilian, mother-in-law shared old-world “words of wisdom” that apply even today, to energy savings and management. She used to say, “Abbastanza abbastanza molto troppo e malamente,” which translates as, “enough is enough, too much is no good.” I imagine that this saying originally had to do with kids and horseplay, yet it certainly fits with energy management, in which you must use only what you need in order to produce. Anything more though, is no good. It’s simply waste.
Worldwide, the primary drivers behind efficiency in plant operations are energy cost savings that increase bottom line profits. For some industries, energy is a sizable production cost. For all industries, energy is a controllable production cost.
This blog will focus on maximizing operational cost savings in your plant. It is worth noting, though, that there are several secondary benefits that go along with efficiency improvements. By increasing efficiency, you can also achieve growth in process control, reliability and equipment life; and reductions in carbon footprint, maintenance and spare parts.
Manufacturing operations will commonly have opportunity to save 30-50% of “system” energy use. Common systems include fans, pumps, compressed air, steam and lighting, though other equipment will benefit from a similar approach. Address multiple systems to achieve 10-20% utility savings across-the-board. System evaluation should be done holistically to understand how all elements work together. For maximum gain, look for opportunities to increase efficiency from 3 distinct perspectives: components, process and operations. To help illustrate these areas, I will use examples involving lighting systems, as they are easy to understand.
The first step to evaluating your system is to assess its component efficiency and explore alternatives. In the case of an incandescent light bulb, common alternatives include fluorescent and LED lamps. Sixty-watt incandescent light bulbs can be replaced by either thirteen to eighteen-watt compact fluorescent bulbs or LED bulbs that use between seven and nine watts.
Next, consider the process dimension. How much output do you need? In the case of lighting in a conference room, lighting requirements vary according to how the room is used. High levels of lighting are ideal for rooms in which people are constantly reviewing the fine print of legal contracts. In an area designed for presentations, low levels of lighting are more ideal.
When selecting equipment, it is also important to consider how often you serve varying needs with a fixed output. While many plant systems have just two operating modes (on and off), they may support varying production processes. For fan and pump systems, mechanical flow controls are often present in the form of inlet guides, vanes and outlet dampers. While better than nothing, there’s still room for improvement. In this scenario, the fan or pump operates at full output while a secondary process mechanically reduces the output to better match the process need. While generally reliable, the secondary control reduces system efficiency. It is therefore better to operate your fans and pumps directly at their required output. This is commonly achieved with a variable speed drive that operates the fan or pump to precisely control the output.
Finally, to increase efficiency, consider operational dimensions of your system. When do you need the output of the system? In the case of a lighting system that operates 24/7 in a plant that produces just five days per week, you likely have the opportunity to increase efficiency and lower your costs by turning off a portion of the lighting on weekends. This same principle is true for your process equipment. Does equipment run despite no scheduled production? When you encounter a process interruption and production stops, does your equipment continue to run at its normal speed, or does it stop or drop to an idle speed?
Taken together, these three dimensions of savings will expand your operational gains and maximize the savings. Dollar cost savings also will be a function of hours of operation and cost for electricity. Now – where can you apply these principles to immediately make a difference in your operations?
For additional tips and systems, refer to the US Department of Energy, Office of Energy Efficiency & Renewable Energy for dozens of specific tips across 6 common plant systems.
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