What are the advantages of Compress Air Optimization Using Frequency Inverter?

Question

A brewery uses compressed air for its production processes. It employs a compressor driven by an AC motor to produce the required volume and pressure during production days (Monday to Friday). The power consumed by the compressor is just alright during peak load or high plant air demand. Now, during lean days (Saturday and Sunday) only about 20% of the total compressor capacity could be utilized by the plant with the same and only one high power compressor motor. The management wants to cut down operational expenses.

Answer 1

You probably are talking about a screw compressor, which runs continuously. The frequency inverter would be a variable speed drive, I take it. So, when the load is low, it could run at a lower speed. The problem is that VSD (or VFD) are expensive and the kwh savings may not justify installing one.

If it is just a regular compressed air installation, you could try installing larger receiver tanks, i.e., system volume, and try shutting down the compressor while the system pressure holds. IOW, let the compressor cycle.

or,

install a regular reciprocating compressor, which is designed to cycle.

However, while the compressor is idle, the kwh load will be low, regardless.

Finally, remember, management is always right, so, if management wants it, don´t argue. Nobody likes a wise ***, but management loves to look wise.
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Answer 2

It is an Interesting coincidence that just a few days ago I read an article on the subject, unfortunately I don't remember where, so I can't jive you a link. Basically the authors premises was VSD compressors were generally oversold, they have their uses, but not as often as the people selling them would like you to believe.
The point brought up before, that if the compressor is operating in stop-start mode, a VFD probably won't help you much, makes sense, but if it is a continuously running compressor it might be worthwhile, just take what the sales person tells you with a grain of salt.

Answer 3

You need to submit some more data like no. of compressors and type/capacity, reciever capacity and compressor capacity control during normal operation/ part load operation, pressure switch settings for compressor load/unload,plant air consumption rate to find a practical solution
or you may consult with compressor supplier to select a optimum mode of opration to save energy.
Variable frequency drive may be suitable / economic only if installed capacity is large enough .

Answer 4

I don't get your question even though each of the words in it is known to me.

Rather than a a standard motor that draws the same power whether it is heavily loaded or not you could get a variable speed motor and a variable speed drive, Combining that with an air flow meter you can create a system in which the motor slows down and compresses less air per minute , drawing less AC current, during the lighter load times. The initial cost is higher but there would be significant energy savings.

Answer 5

I couldn't tell you without some solid numbers.

If it's the kind of compressor that's designed to run intermittently anyway, then there's no reason to make any change.

It would be a simple matter to run some cost and power consumption numbers, in order to justify buying a smaller unit to use during off days.

Answer 6

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