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7 steps to optimise energy use in manufacturing processes

7 steps to optimise energy use in manufacturing processes

Often the primary focus of industrial energy efficiency initiatives is utility production. This is perfectly understandable, given that the products are the very purpose of the activity and cannot suffer the slightest drop in quality or production rate. So are the production processes themselves out of bounds? The answer is no: it is possible (and often desirable) to cast a critical eye on their energy efficiency, too. Here are a few pointers to get you started…

 

Get the operators involved

In factories and workshops, as elsewhere, the aim is to get it right: quality products, produced as per the instructions and KPIs, with the backing of experience and knowledge. Except that these good intentions sometimes (and even often) result in energy-hungry practices such as allowing over-generous safety margins for power and/or operating time, mistaking habits for instructions (“We’ve been doing it that way for 30 years and no-one has ever complained”) and a glaring failure to take energy aspects into consideration. Admittedly energy efficiency is not the priority, but that is no reason to totally disregard it.

 

The solutions:

Find compromises for the safety margins. This calls for complete confidence in your facilities, your plant and your skills.

Regularly check for skills and knowledge gaps, and either provide the necessary training and/or transfer staff to another position.

With the help of outside tools and expertise, take a critical look at ingrained habits.

 

 

Use your waste heat

Virtually all processes generate residual heat, which is not always put to use. Sometimes for good reason, because it would clearly not be cost-effective. But often mistakenly, for want of having thoroughly investigated the possibilities. Will it be cost-effective to use the compressor cooling water to preheat your boiler room water? While there are exchangers for all forms of heat recovery (gas/gas, liquid/liquid, liquid/gas, etc.), you still need to be sure that heat production coincides with the heat requirements, that the power and temperature are compatible, that the distance between heat producers and consumers is reasonable, and so on.

 

The solution:

Use the PINCH method.

This tool (now available as software) can be used to analyse a heat system and maximise energy efficiency by using exchangers, taking into account the necessary investments, the price of energy, etc.

 

 

Fine-tune your regulations

Instrumentation and control strategy regularly runs up against two types of problems. First, identifying the right settings to adjust. This is no easy task if you are not thoroughly familiar with the factory’s processes and plant. Second, defining the regulation settings. How can you be sure that the PID (proportional, integral and derived) corrections are neither “standard” nor arbitrary?

 

The solution:

Get the operators to talk to the instrumentation and control system with the help of an analysis tool and possibly an outside expert. Over and above the obvious benefits of working in collaboration, the aim is to make the regulation’s operation totally objective and detect malfunctions (pumping problems, dead bands, connection/disconnection of the machines, improper sequencing/overlapping of regulation loops, etc.).

 

 

Make the configuration more flexible

“There must be 10% residual moisture in our raw material.” Really? What happens if there is 9% or 11%? What impact will it have on the quality of the finished product? On process reliability? On plant servicing and maintenance? And, most importantly, how much does it cost to reduce this moisture point? Is there potential for increasing ease of operation, productivity and energy?

 

The solution:

Switch from set points to set zones: 10% +/1.

Naturally the initiative calls for an in-depth study of the processes, along with quality, maintenance, instrumentation & control, etc. Physical testing is also useful.

 

 

Avoid plant obsolescence

Is there any need to remind readers that a used machine will ALWAYS use more energy than a new one? Of course, we are not talking about replacing plant that is still serviceable by more economical models (though this can sometimes pay off). But it is exasperating to see a team’s energy-saving efforts thwarted by antiquated machinery simply because there is no budget for CAPEX.

 

The solution:

Get management on side with a convincing argument! Make sure you have a solid financial case and can demonstrate a fast ROI (including energy, quality, maintenance costs, etc.).

Don’t forget differential investment: if you have to replace a machine whatever happens, the ROI of an efficient (and expensive) machine can be counted against a replacement with an identical machine.

 

 

Renovate your distribution networks

Take the example of a hot water network that supplies five buildings. Twenty years after its construction, two of the buildings have disappeared and been replaced by another building situated further away on the site. To adequately service the more distant, energy-hungry building, the network has to operate at a higher pressure and temperature. A boon for the other users, who take advantage of the fact to consume more than is actually necessary!

 

The solution:

Regularly conduct a thorough review of your distribution networks (layout, settings, balance). At the very least, install equipment and meters to encourage more responsible user behaviour.

Remember to cut off buildings when they are not using energy (at night, over weekends and during holidays, etc.).

 

 

Give managers the tools they need

Who knows most about the workshop’s operation: the manager who monitors the KPIs on Excel or the shop floor foreman who grapples with it on a daily basis? Admittedly they do not have the same job remit, but even so: how can you reconcile energy efficiency and ease of operation (which are fundamentally opposed) without first-hand experience of the constraints on the ground?

 

The solutions:

Managers, keep a finger on the workshop’s pulse! Go to the workshops every day to listen, ask questions and talk to the people who work there with genuine, well-meaning interest. Stay in touch with your teams’ concerns and keep their trust in you: it will ease the way when you want to change their habits. Naturally you should also buy a digital energy-management platform (Blu.e has a very good one to offer!) to document and back up your analyses and proposals.