Saving money through industrial energy efficiency

Today we are going to talk about how efficiency in industrial energy consumption allows us to save money. I have always been interested in the connection between reliability management and other functional responsibilities within a manufacturing organisation, such as quality and safety.

Clearly, the reliability of manufacturing processes increases quality and is one of the three primary elements of overall business effectiveness. Furthermore, when manufacturing processes are reliable and predictable, there is less chance of a workplace accident occurring. Lately, I have been thinking a lot about the relationship between reliability and energy management. In my opinion, there is a close connection that is worth exploring.

Monitoring and managing energy consumption is beneficial for both the organisation and the environment. It is a win-win situation in every sense. Currently, between 30% and 40% of the electricity we generate is required to power industrial electric motors. 

Even a small gain in energy efficiency would significantly reduce aggregate energy demand, reducing capital expenditure on building more power plants, fossil fuel consumption, and associated emissions. For your company, spending less on energy translates into real monetary savings. Furthermore, by reducing the load, use and wear and tear on industrial assets, manufacturing reliability is improved, enhancing the value of your organisation.

Outline of benefits through industrial energy consumption efficiency

During the life cycle of an industrial asset, energy consumption is often the largest expense. Some aspects of the costs of powering a machine cannot be controlled, but others can.

Let us consider for a moment the economics of powering a 200 horsepower electric motor. Assuming a load factor of 80% and a modest energy cost of €0.06 per kilowatt hour (kWh), it would cost more than €57,000 each year to power the motor, assuming 8,000 hours of operation.

A quick analysis reveals that the price of a 460-volt three-phase electric motor ranges from €5,000 to €8,000. I am sure there are motors that cost more or less, but the point is that the cost of powering the electric motor is approximately 100 times its purchase price, assuming a useful life of 10 years. A reduction of between 5% and 10% of this cost can have a profound effect on the bottom line.

In my example, a 10% improvement in energy efficiency drives an extra €5,700 below the baseline, and that's with a simple 200 hp garden-type electric motor. How are these savings achieved? I have listed a few points for your consideration. Some have direct and positive effects on operational reliability, in addition to the obvious savings in energy costs.

• 1. Select high-efficiency motors: Compare performance between technical specification plates. High-efficiency motors will cost more money upfront. Do not be swayed by initial savings. Assuming that a regular efficiency electric motor costs €5,000 and uses 10% more energy than a high-efficiency motor, which could cost more than €60,000, the latter would still reduce costs in terms of the economic rate of return over the 10-year life cycle of the electric motor (assuming 8,000 hours per year of operation). The upfront payment of a premium of £501 for a high-efficiency electric motor yields an internal rate of return of £2,291. That is the equivalent of finding a bank that would pay you £2,291 per year in interest on your deposits. A 5% energy efficiency for which you have to pay 50% more still has an internal rate of return of 115%. It is easy to justify this investment if you use life cycle cost as a decision-making tool. 
• 2. Design powertrains to improve energy efficiency. Misjudging energy losses in mechanical traction trains can significantly affect the energy bill for a single industrial asset. Of course, we want efficient engines, but improving engine efficiency is only half the battle. We also have to manage the efficiency of the driven components. Selecting efficient gearbox and coupling designs, among other actions, can substantially affect the total energy bill. Apply the principles of precision, balance, alignment, clearance, resonance and lubrication to the entire drive train.
• 3. Manage the electrical system comprehensively. If your motor control centre has faulty connections, degraded or undersized wiring, energy efficiency will be compromised in a short time. If the circuits are overheating or overloaded, energy is not being distributed efficiently. Furthermore, the reliability of the motor control centre and the motor may be compromised. In the case of eddy currents, high potential build-up also leads to electrical discharge erosion, a form of wear and tear on the mechanism referred to as “striations.” In conclusion, energy losses compromise reliability.
• 4. Operate within the ideal load range. Using our example of the electric motor, if it operates above or below its rated load range, then it produces poor energy efficiency and decreases its reliability. For most electric motors, energy efficiency decreases precipitously when the motor is operated at less than 40% of its rated load.
• 5. Optimise rebuild/replace decisions. When an asset wears out, it also becomes misaligned and loses precision, which of course results in wasted energy. After a few days, weeks or months of service, this will result in high energy efficiency costs.
• 6. Manage balance, alignment, adjustment, and resonance. Imbalance, misalignment, misadjustment, and resonance generate mechanical friction. This increases friction, which transforms electrical energy into thermal energy, and you have to pay for it. In some instances, friction is desirable. However, when it is caused by a loss of precision in the handling of imbalance, misalignment, misadjustment and resonance, you are literally paying for the energy required to increase wear and reduce the reliability of the machines. Predictive maintenance of rotating machines pays off, both in terms of reliability and energy management.
• 7. Employ precision lubrication. Selecting a lubricant with the wrong viscosity can significantly affect both energy consumption and reliability. If the viscosity is too low, there will be friction between surfaces. If the viscosity is too high, it will result in viscous drag. Both waste energy. A common mistake is the use of multipurpose grease in electric motors. The viscosity of grease is approximately 320 centistokes at 40 °C. Most electric motors require grease formulated using an oil base with a viscosity of 100 to 150 cST at 40 °C. The extra viscosity reduces energy efficiency and compromises motor reliability. Similarly, motors are often over-greased, further compromising energy efficiency and reliability. 
• 8. Energy consumption due to monitoring. Changes in asset condition are frequently revealed through energy monitoring. 

Traditionally, we use vibration analysis.n, thermography and others condition monitoring tools to identify and resolve abnormal conditions in industrial assets. By definition, if a machine begins to vibrate or overheat, it is using more energy or transforming energy with reduced efficiency, so monitoring energy efficiency is a natural part of condition monitoring. Furthermore, it is relatively easy to do and can be performed on an ongoing basis. 

Energy monitoring also allows for the comparison of the efficiency of various equipment and component designs, helping to make better decisions regarding the design and acquisition of industrial assets that minimise the life cycle cost of the property and maximise the net return on industrial assets.

Industrial energy efficiency: Energy matters

Monitoring and managing energy consumption is a wise move. A mere 5% improvement can translate into considerable savings for the organisation. If the above factors are poorly managed, it is possible to lose 10%, 15% or more. This wasted energy is often converted into heat and/or mechanical displacement (vibration). A good energy management policy and a good reliability policy are natural allies. There are many government programmes that seek to promote energy awareness, often covering all (or part) of the investment required to improve energy efficiency.

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