I will now I will blow your 22kw claim out of the water
Posted 06 March 2004 - 01:55 PM
you have stated an installed cost of $4919, does this come with a french maid for the month? or perhaps a nice brown envelope full of backhander money?
THE INSTALLED COST OF OUR 22KW MOTOR CONTROLLER IS $1253.07. THEREBY GIVING YOU A RETURN ON INVESTMENT OF LESS THAN 12 MONTHS AT AN OPERATION OF 24 HOURS PER DAY, 7 DAY WEEK. now if we can turn the motor off automatically for 1 hour per day, lets assume the motor is consuming 5kw at idle, the savings can be increased by some $254 per year, thereby giving a payback of some 10 months. quite nice if i say so myself!
I think i have stated my case!
Posted 06 March 2004 - 08:37 PM
Your comments concerning the cost of a 22KW unit are noted. The figures quoted reflected the local cost in $NZ when the paper was written some ten or so years ago. The major theme of the paper, is not to expound the costs, but the claims for the quantity of savings. I agree that as the costs of the savers come down, and the cost of energy goes up, the threshold of where they can achieve a reasonable return will shift. The installed costs of the equipemnt and the cost of energy is very localised, so there is no magic formula for everywhere. My major concern is that the performance quoted by many sellers of the technology is inaccurate, and my contention is that you can only save a portion of what is being wasted.
I am interested in your comments in regard to a 22KW motor with an idle consumption of 5KW. That means that the motor will have a full load efficiency of less than 80%. Generally, at full load, the copper los and iron loss are of the same order of magnitude. If the iron loss is in the order of 5KW, lets call it 4KW, then the full load copper loss would be of a similar order, so full load losses would be say 9 KW. this would put the full load efficiency at 22/31 = 70% which is getting low for a motor of that size. Rather than installing an energy saver, I would be looking at a more efficient motor.
Shutting the machine down when not in use is by far the better way of saving energy as you save not only the energy loss in the motor, but also the energy loss in the driven load which is usually the major loss.
Please feel free to post examples of good results here. We are not trying to knock the technology, just show the flaws in some advertising claims.
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