Energy Saving Ideas for Industrial Air Compressors
Why save compressed air?
Compressed air is an essential resource: it is often referred to as the fourth utility after gas, electricity and water. The common misconception however is that it is free. Air is free - until it is compressed.
There are two main reasons for reducing the amount of compressed air you use:
- It is expensive
- To produce it requires a lot of of energy (Usually electricity)
We often use it because it's there and it's convenient. The cost and effects on the environment are invisible, so no-one is aware of compressed airs' real impact.
The real cost of compressed air.
Natural resources, such as coal, gas or oil, are used to generate electricity. This secondary energy source is then used to produce compressed air. This makes it very expensive, about ten times the cost of electricity.
Only 4% of the coal mined from the ground is usefully converted into compressed air, the rest is lost in waste heat at the power station, along transmission lines, and finally in the compressor itself.
For every 100 units of electricity which go into the compressor, only 10 units are available for use. The rest is rejected as waste heat.
You can effectively cut the cost of compressed air if you recover the waste heat from the compressor, e.g. by ducting the warm air to heat nearby areas of the plant during winter.
The importance of maintenance.
Most people think that the largest cost is the purchase price of the compressor, then the running costs are mostly maintenance. NOT TRUE! Over a 10 year period 75% of the total cost is energy - i.e. electricity.
If maintenance is neglected, electricity use increases e.g. when a filter is clogged, extra power is needed to overcome the obstruction, so the generating pressure is increased. More energy = more costs.
The most important issue for production is that the compressed air system is reliable. The supply will be more reliable with regular maintenance.
How can I get started?
Calculate how much your compressed air system costs your business each year.
You can get approximate running costs in terms of electricity for a compressor each year, using the calculation below
| Size of Motor (kW) |
x | Cost of
Electricity Per Unit |
x | Running hours per day |
x | Days | x | Weeks |
Example; A factory runs a 100KW compressor 24 hours a day, 5.5 days a week, all year round. It pays 10p per unit (kilowatt hour) for electricity.
Cost = 100 x 0.10 x 24 x 5.5 x 52 = £68,640 a year!
This figure is only a guideline, since it assumes only fully load running, and it also does not take into account of actual motor efficiency.
Check for leaks
The typical leak rate on a site can be up to 40%. That's a lot of compressed air wasted, so the compressor will have to work harder and longer.
Switch off when not needed.
Compressed installations are often left on overnight, even when there is no production. This is very wasteful because
- Power is being used to feed leaks:
- Even when compressors are idling, they can still draw 40% of their full load current.
Controls
Compressors switch on and off as the pressure demand varies. This 'cycling' is very wasteful in terms of energy.
Fitting timers and control systems, including variable speed drives can minimise or eliminate the on load and off load patterns and save substantial amounts of money.
Action Plan
Contact CompCare Compressed Air and carry out a complete review today of the whole compressed air system.