By Timothy A. Warren, PE, LEED AP BD+C
The variety of systems and user requirements associated with manufacturing facilities present many challenges, one of which is energy reduction. With these challenges there is opportunity to be creative to find economical and efficient systems that will serve companies well for many years.
Design professionals have a direct impact on energy efficiency, and I feel very strongly that environmental stewardship needs to be a core competency of any firm operating in this market space. As a mechanical engineer, I primarily associate sustainability of MEP systems and industrial buildings with energy reduction.
Why is this?
For starters, here are some of the jaw-dropping statistics about industrial energy:
- 30% of all greenhouse gas emissions in the United States
- 37% of all greenhouse gas emissions worldwide
- 40% of energy use worldwide
If this isn’t horrible enough, as much as 30% of this energy is wasted, costing more than $180 billion annually in the United States alone.
There are many ways to reduce energy. Opportunities range from the “low-hanging fruit” that are straightforward and inexpensive to the more complex and sometimes expensive opportunities that may offer a greater return. So how do you get from here to there when it comes to energy reduction?
It starts with a corporate commitment and a management plan. The ENERGY STAR Guide for Identifying Energy Savings in Manufacturing Plants, sponsored by the EPA, discusses the principals for energy management and provides a comprehensive summary of energy efficient practices and technologies, potential savings, and references to more detailed information. This a very useful document for those operating within the manufacturing sector.
The guide includes two interesting graphics:
Source: US Department of Energy
One thing that certainly doesn’t surprise most industrial users is that motor systems use the greatest amount of electricity. These are the process systems and traditionally represent a point of contention between industrial buildings and LEED certification. In the previous versions of LEED, energy reduction was measured as a whole. That meant as a building designer, I could find ways to reduce the energy efficiency of HVAC systems to a large degree; however, because energy was being evaluated as a whole, including process loads, any energy reduction would be insignificant when compared to the overall energy use of the building.
I like to think of energy categories as “buckets” where energy is being used, and each bucket represents a potential to reduce energy within a manufacturing operation. These buckets include:
- Motors
- Compressed Air
- Pumps
- Hot Water and Steam Systems
- HVAC
- Lighting
- Process Integration
- Process Heating-Furnaces
Of course it’s hard to classify all the various energy uses of manufacturing plants in a few categories, but these “buckets” offer many opportunities to increase energy efficiency and ultimately reduce energy costs. In reviewing the energy reduction strategies within the guide, I wanted to share my perspective on strategies that are beyond the more common measures, or “low-hanging fruit,” that most manufacturers likely have previously addressed. These are the “mid-hanging fruit,” or items you may turn to after gobbling up the easy measures and ask, “What do we do now?” These items have as much potential, and possibly more, when it comes to reducing energy in your facility.
I certainly cannot cover all items in this post, so this will be the first of several posts addressing this topic. I will start by tackling the Motor category, since they are the main electricity consumer and best place to begin – hey, if you want to make a big impact, attack the biggest factor.
MOTORS
How do you start?…it starts with a plan.
Motor Management Plan: The largest energy user needs managed. You’ll need an inventory and tracking program to document and understand what you have and where it is used, including spares. You’ll need guidelines for proactive repair-and-replace decisions. You’ll need to develop a specification for procuring or repairing motors. And finally you’ll need to develop and implement a predictive and preventative maintenance program. These measures work toward ensuring proper use and application of your motors as well as maintaining motor operating efficiency.
Select Highest Efficiency as Applicable: Select motors strategically by balancing efficiency with the motor’s life cycle cost rather than just first cost and installation costs. Up to 95% of a motor’s cost is actually the energy expense over its life, while purchase, installation, and maintenance costs represent only 5% of total expenses. Premium efficiency motors are most attractive when annual operation exceeds 2000 hours/year. There is a software tool in the Energy Star Guide to assist with motor selection. You may want to also review any available rebates and/or incentives that may positively impact payback times.
Properly Size Motors: It’s plain and simple, motors operate most efficiently when fully loaded. Both efficiency and power factor are reduced at part load. On average, replacing motors properly matched to the loads they serve can save 1% of total motor electricity consumption. An important point here is having a proper spare inventory when replacing motors. I’m sure many times, in a pinch during a failure, an oversized motor is used based on availability. However, they often stay in place far longer than they should, thus increasing energy use and costs.
Consider Variable Speed Drives: Variable speed drives (VSD) can provide energy savings as high as 60% by matching motor speed to the load requirements. In doing so, they will allow motor efficiency to be maintained and only provide the work needed. Note that VSDs are not for every application. The load of the driven equipment must be variable for VSDs to make sense.
Correct Power Factor: While I realize a mechanical engineer talking about power factor is like an electrical engineer explaining the cooling and dehumidifying process, I’ll give it my best shot! Motors are an inductive load measured in KVA. Power is made up of resistive power (KW) and reactive power (KVA). Resistive power, known as active power, is converted to actual work. Therefore, power factor (PF) = KW/KVA. As power factor is reduced due to inefficient motor loadings, the KVA increases, resulting in increased power consumption that usually does not show up in the KW usage. Utilities typically measure and bill KW; however they typically have penalties for low power factor, therefore costing you more money. Power factor can be corrected by reducing inefficient motor loadings, using high efficient or premium efficient motors, and installing capacitors in the AC circuit to reduce the reactive power in the system. Advantages are reduced cost and increased capacity of the electrical distribution system.
In the next post we’ll look at how to reduce the energy use of your compressed air and pump systems.
Questions about reducing energy in your industrial facility? Contact Tim Warren at 717.434.1566 or twarren@jdbe.com.
