TACKLING ELECTRICAL ENERGY EFFICIENCY IN INDUSTRIAL PLANTS

Electricity is an indispensable energy carrier in industrial plants, where it is used to power induction motors, provides energy for the heating of materials, in lighting applications, for activities such as welding and soldering, in induction furnaces and for many other uses. Individual industries tend to have quite different electrical energy demands, but it is safe to say that as electricity prices continue to escalate, most management teams have electricity savings firmly in their sights.

Why concern your organisation with energy efficiency?

Reducing electrical energy consumption is of interest to sustainability-focused organisations for the following reasons:

    

          In energy-intensive industries electrical energy efficiency is a powerful profit driver. This is becoming even more of an issue in countries such as South Africa, where electricity prices for industrial organisations have been escalating at in excess of 25%/annum for a few years in succession now;

        Every unit of electrical energy saved translates into a reduced impact on the environment. In South Africa, each kWh of energy produced is estimated to generate 1.015 kg of carbon dioxide equivalents¹ due to the coal-heavy nature of our energy mix. Then there are of course the large amounts of water required to generate power from coal, along with particulate emissions, mercury emissions and potential quality impacts on water resources. Further up the value chain, there are significant impacts arising from coal mining. From a life-cycle perspective, there are therefore few more meaningful things an organisation can do for the environment than to reduce electrical energy consumption.

     The above issues have social impacts, since increased profits can contribute towards job creation, both directly within a business and within its broader value chain, and environmental degradation generally tends to hurt socially vulnerable communities more. In emerging economies (and in first world countries too at times), power supplies can also be limited and energy efficiency therefore helps to make limited resources available to more consumers.

How to go about it? 

How should individual industrial power consumers begin an energy efficiency programme, and what are the important issues to consider when doing so? The nature of your industry will dictate where you will need to focus, but where should you start, and how are the savings actually going to be realised? I will hopefully answer some of these questions in this article.

Baseline your performance

The first thing you need to do is to analyse and understand your electricity bills and each cost element contained in them. When analysing an industrial site’s energy profile, I typically look at monthly bills stretching back over the most recent two year period. This gives me a sense of any seasonality in electricity consumption, the timing and scale of past price increases, and the tariff structure employed. Linking energy consumption to production levels is useful in terms of understanding crude energy intensity levels e.g. kWh/ton of production, and I typically construct trends of the data in order to provide insight into patterns. This exercise alone can immediately suggest savings opportunities. For example, there may be opportunities to shift load and achieve a lower average cost of electricity where time-of-use and maximum demand charges are applied.  

Assess the performance of individual processes and energy users

Conducting an energy audit of your operations at the process level should be your next activity in the quest to become more energy-efficient. There are typically a number of specialist companies you could approach to conduct such an audit. The audit should look at individual aspects of your operation and every point at which electricity is being used, but should also incorporate a “systems view” which takes potential impacts and synergies between individual areas into account. Hence, if you are reducing the energy requirements of a furnace, for example, it is not only about making the furnace more efficient, but also about reducing the levels of rework which that furnace needs to process. Solving a problem of that nature may require a review of downstream operations in relation to the furnace, and cannot be solved by looking at the energy efficiency of those operations and the furnace as separate entities.

An electrical energy efficiency audit will highlight areas of opportunity, and for each of these, the next step is to identify appropriate solutions. These solutions need not require large investment, and could include changes to shop floor work practices, the implementation of improved management systems, the performance of appropriate preventive maintenance tasks, changes to process set points and other approaches. The table below outlines a few examples of these types of solutions.

ENERGY EFFICIENCY PROBLEMS THAT DO NOT REQUIRE INVESTMENT FOR THEIR SOLUTION

ENERGY EFFICIENCY OPPORTUNITY	SOLUTION
Electrically heated process baths are operated at too high a temperature.	Reduce temperature set point by 5 deg. C
Refrigeration plant evaporative condenser is not removing enough heat from the refrigerant. Tubes were found to be excessively scaled up and some nozzles were blocked.	Institute a chemical de-scaling programme for the condenser tubes and a blowdown procedure for the cooling water.
Too many factory lights were found to be left on unnecessarily at night.	Add more switches to allow areas to be individually controlled, and institute a checklist for plant operators for implementation when the plant is shut down at night.
Compressed air reticulation system was found to have excessive air leaks.	Institute a regular leak detection and maintenance programme.
Compressed air pressure too high.	Reduce compressor pressure set point.
V-belts on drive systems slipping excessively.	Measure belt tension and correct regularly, taking care to check alignment at the same time.
Air conditioners set at too low a temperature during the warm months.	Increase the air conditioner temperature set points.
Production systems running on idle for long periods due to poor planning.	Investigate bottlenecks in material flow and improve planning processes.

Technological solutions are widely available to improve energy efficiency, and it is worthwhile to keep up to date with latest developments through regular engagements with OEM’s, and attending industry engagements (seminars/conferences). There is also a wealth of information available on the internet, but take care to verify manufacturers’ claims.

Understand the risks associated with individual solutions

Whether solutions are technological or not, remember to assess the risks involved with the implementation of any solution. Reducing the temperature of a process bath in an electroplating operation could have implications for drag out losses, for example, and dropping air pressure on a site could affect the operation of individual machines. While not all such risks can be quantified beforehand, make a point of evaluating the impacts of changes made so that if there are unintended consequences, these can be rapidly detected and dealt with. Where there are significant capital costs involved in your solution, consider life cycle costs, not just capital outlay. While operating costs tend to dominate life cycle costs for electrical equipment such as lighting, consider also environmental impacts, and the challenges that could be associated with the safe disposal of used components.

A useful risk management strategy is to pursue limited implementation, which allows an assessment of post-implementation performance prior to making larger financial commitments. This is particularly important when working with novel technologies, but of course cannot be used to assess risks which only present themselves after a long period of time, since implementation would be unduly delayed. Another option would be to insist on client references, and to contact these clients to get their views on the merits of individual energy efficiency products.

Evaluate implemented options and use feedback constructively

Finally, each implemented sub-project should be reviewed against the criteria which justified its implementation in the first place. This aspect of implementation, which you could call “performance testing”, is in my experience the most neglected part of energy efficiency project implementation. Are those new lighting arrangements really using the amount of energy expected, and is the light provided sufficient and sustained? If not, what is the problem? As with all continuous improvement, improvements in energy efficiency are also subject to the Plan-Do-Check-Act cycle.

I will review individual energy efficiency opportunities and how to practically assess these in future posts.

References

1. Letete, Guma and Marquard, “Information on climate change in South Africa: greenhouse gas emissions and mitigation options”, University of Cape Town Energy Research Centre.