By Ron Marshall
What is my compressed air’s electric bill percentage? This is a difficult question to answer, because rarely are there any energy meters installed on typical compressed air systems. But there are some hints if we do some research.
Years ago, the USDOE did a detailed study of motor systems and found that about 62% of industrial electrical consumption was made up of motor driven loads. Of this, about 16% of the total motor load was air compressors. So, on average, about 10% of an average electrical bill is eaten by air compressors.
But, like all averages, things can vary. A compressed air audit at a large foundry with giant electric arc furnaces showed a different story. The system had 6 large 200-hp compressors running most of the time. However, compared to the very large demand of the furnaces, the air compressor energy worked out to a mere 0.5% of the total bill.
Meanwhile, a very small factory producing paint sample cards purchased a much-oversized air compressor on eBay. When a system audit was done, it showed that the air compressor was consuming 50% of the total facility electrical consumption!
So, the answer varies. Most compressed air auditors will say that a 20% figure is pretty typical. But of that proportion there are usually significant energy savings opportunities. In most cases, reductions of between 10% and 30% can be gained by applying low-cost or no-cost efficiency improvements. Mostly these improvements are achieved by better controlling air compressor and reducing waste through leak reduction and elimination of wasteful end uses.
And consider this — using compressed air to produce a mechanical output is extremely inefficient. For a perfect lossless system, roughly 7 to 8 hp is consumed at the air compressor for every 1 hp of mechanical energy at any compressed air driven end-use. For a real-life system with leaks, pressure loss and compressor inefficiency things can get much worse.
Curious to find out the cost of your air system? Call in some experts to monitor your system. Most compressor suppliers or service companies have personnel who can do basic compressed air system assessments.
Filed Under: Compressed Air Technologies, Engineering Basics, Pneumatic Tips