Oh No!
Am I turning Green?

Anyone that knows me, would know that I'm  not exactly a liberal. I like guns, Rush Limbaugh, Fox News,  Southern Baptists, and strict constructionist judges.

I believe in God, have been married to Vicki for 38 years, stand and salute when the National Anthem is played, believe in lower taxes, smaller government, and individual responsibility.

While I'm a big fan of our national parks, hiking, and outdoors, I don't support making the polar bear an endangered species, think that we are crazy not to be drilling for oil in Alaska, and  have serious doubts that humans have, or even could, cause climate change.

I don't hate oil companies, and am fearful that bureaucratic meddling in the oil markets will result not in lower prices, but in gas lines as the supplies divert to other countries with less onerous regulation. 

Self-appointed ecology police, through silly and disruptive lawsuits, demonstrations, and lobbying have managed, in the eyes of many Americans, to equate the word "green" with "idiot."   That's unfortunate, because going green doesn't have to be silly or idiotic.

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 EMA has been involved in the electronic motor drive business for almost 20 years now.  Drives are "Green Technology."  Per most accounts, electric motors are the single largest users of electrical energy, and only about 10% of motors have drives on them.  A recent article in US News & World Report gave several examples of significant energy savings accomplished through applying Variable Frequency Drives (VFDs).

As more and more commercial buildings and industrial facilities seek LEED certification as a "green" building, more and more interest is being paid to using VFDs to significantly reduce  electrical consumption.

How do VFDs save energy?

 

      First, a caution..   I've often used a little formula to encourage young engineers to be properly cynical of glib technology pitches.

   OK, I'm joking (sort of).  But to be truthful, I've seen VFDs put on applications where it was necessary for the motor to run full speed, full load, all of the time.  Putting a drive on that application will not only fail to save energy, it will actually use more due to the losses within the drive. The same thing can apply to other "green" technologies. One example that comes to mind is several well intentioned recycling projects that used more energy and resources in the recycling process than the original product used.  Many people are now questioning the wisdom of ethanol subsidies due to the resources it consumes.   It's always best to look carefully at any supposedly green technology, and apply both hard science and common sense. 

So, HOW DO VFDs save energy? The best opportunities for saving energy with VFDs is on centrifugal fan and pump applications. What's known as the Affinity Laws for Pumps and Fans follows:

 

 

 

 

 

 

 

 

This simply means:  A SMALL reduction in speed
means a BIG reduction in energy consumed.

Let's look at a real world example:

EMA added VFDs to four 40 horsepower air-handlers at an Atlanta area hospital that had been controlling pressure with inlet vanes.  We installed 4 Yaskawa E7 VFDs, and simply controlled them with the same system that was controlling the mechanical inlet vanes. (We locked the vanes in an open position). The payback, including all installation and engineering costs, was roughly 1 year (1 year and 15 days to be exact).  Their yearly energy savings thereafter was almost $14,000 per year at current rates.  Think about that for a moment..  $14,000.00 per year in energy savings JUST for putting VFDs on 4 air-handlers! A very simple, no hassle, and straight forward project.  Great way to GREEN your building!

 

Motors are usually sized for the maximum load anticipated. In a typical HVAC situation, this means the hottest day, with the most people in the building. But very few days are the hottest, and seldom is the building completely occupied.  This means that the system can operate well below its maximum ratings, and by slowing the motors, rather than using dampers, vanes, or valves to restrict flow, the affinity laws apply. 

Aside from saving natural resources, this amounts to significant dollar savings for the facility, and in almost every case, much tighter control of the building air quality.

So even the most staunch right wing conservative can actually be happy about going green!  Listen, if I like it, anybody will!

Eddie Mayfield
edmayfield@emainc.net

EMA Drive Lines, May 2008
www.emainc.net

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