10 Great tips for wasting energy

Compressed air is a costly form of energy--here's what NOT to do to improve your plant's efficiency

When did air stop being free?

For breathing, of course air still free. But compressed air is actually one of the most expensive sources of energy in a plant and costs as much as eight times the price of electricity. The electricity to run an air compressor is about 70% of its cost of ownership, far greater than the costs of buying and maintaining the compressor itself.

Compressed air is used in some sense in around 80% of all manufacturing, driving everything from conveyors and pumps to pneumatic tools and hoists. Sometimes it’s even called the “fourth utility” after electricity, water and gas.

On average across manufacturing industries, compressed air is around 10% of energy costs, but in certain industries this can be as much as 20%. Yet in a US Department of Energy study, only 20% of manufacturers have addressed the energy efficiency of their compressed air systems.

So why is such a common and expensive source of energy used so inefficiently?  A good part of the explanation can go back to the adage, “if it ain’t broke, don’t fix it.” As long as the compressed air is there to do the job it’s supposed to do, there is no reason to worry about it.

So here are 10 ways to help air compressors continue wasting air:

1. Don’t know your real cost of compressed air. There are simple calculations you can make based on your air compressor’s operating hours and work load that will tell you how much it actually costs you to run your compressor. If you can’t see the cost, you can’t see the savings opportunities.

2. Continue using compressed air inappropriately. In many factories it’s easy to find idle equipment still drawing compressed air. It’s also common to find compressed air being used when far more efficient alternatives are available – for example an electric fan requires far less energy for cooling than compressed air, and vacuums are much more efficient for cleaning debris than a compressed air nozzle.

3. Just ignore leaks. Most manufacturing processes require air compressed to around 80-90 psi (pounds per square inch), while many manufacturers compress air to over 110 psi just to compensate for leaks in the system. For every 2 psi in increased compression, you use around 1% more energy.

4. Compress air at the maximum pressure you can. Many manufacturers run large air compressor to meet the needs of their maximum demand consumers. For example if the majority of a plant’s processes require 80 psi and one process requires 95 psi, a factory will compress all its air to 95 psi. It is often far more efficient to compress air at the average load, and then implement a local booster for individual higher demand processes.

5. Don’t worry about air quality. Air quality should be matched to the end use, but it’s wasteful to delivery higher quality air than you need.

6. Don’t conduct an air demand analysis. You might find out that your average demand is far below the capacity you are compressing. Some compressors run well at full capacity, but become very inefficient at lower capacities. If your average demand is low, it’s often more efficient to have one robust compressor for peak demand, and then a smaller one for average loads.

7. Never match compressed air supply to demand. There are a number of control and storage technologies for compressed air that can accommodate occasional demand peaks. These allow you to run smaller compressors at higher energy efficiency levels.

8. Don’t connect your compressor motor to a VSD (variable speed drive). VSD’s can help match the motor speed to the demand, making sure they only do the work that is necessary.

9. Forget about receivers and filters. These are supply buffers that help accommodate demand spikes, which mean you can compress air closer to your average demand, not your peak demand.

10. Ignore opportunities to capture and reuse waste heat.

Image credit: Timitrius via creative commons on Flickr

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About the author

Philip Lewin

I'm one of the many people sharing ABB's passion and great stories for robotics and industrial ingenu-ity. It’s exciting for me to be at the leading edge of a new age for one of the most fundamental things that people do - we make things. At the same time, the awareness has never been greater that economic progress, higher living standards and new ways of making things cannot come at the expense of our environment. I’m proud to contribute to this exciting and important discussion.
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