Improve motor efficiency
To improve the (overall) efficiency of any electro-mechanical system - including HVAC - all parts of the process need to be optimized. Since the largest chunk of TOTAL efficiency is in the hands of the mechanical process, a relatively small change there will have a much more noticeable effect on the overall picture.
For example:
Motor efficiency = 96 percent (typical)
VFD Drive efficiency = 98 percent (typical)
Fan efficiency = 50 percent (really generous)
Belt drive efficiency = 88 percent (typical)
PU System efficiency = (Motor)*(Drive)*(Fan)*(Belt) = 0.96*0.98*0.50*0.88 = 0.414
Now, let's work really hard at the motor design, and eke out another 1.5 percent, bringing it up to 97.5. .... PU system efficiency becomes 0.420. So the return on the system is approximately 0.5 percent for a lot of effort (and perhaps a 20 percent cost impact at the motor).
Instead, we'll leave the motor alone and put the effort and cost into the belt drive and get the same 1.5 percent increase: PU system efficiency becomes 0.421. A bit better, but still nothing to write home about.
Ahh .. but what happens when we apply all that effort into increasing the FAN efficiency by 1.5 percent? PU system efficiency becomes 0.426. Now we can see that the overall increase is about 1.2 percent!
The purpose of pushing for high- or premium-efficiency motor designs is because it's the easiest thing to point the finger at. (There's always more room to increase motor efficiency, right?) Kind of like the whole idea behind ethanol production: we choose to use a significant portion of arable land to produce crops that are not sustainable, are not used for food, and require more energy input than we can harvest as output at the end of the process. So why do it? Because it's good advertising - it makes it look like those in charge are doing "something". (And it doesn't overly ruffle the feathers of competing industries, who subsidize "those in charge".)
For example:
Motor efficiency = 96 percent (typical)
VFD Drive efficiency = 98 percent (typical)
Fan efficiency = 50 percent (really generous)
Belt drive efficiency = 88 percent (typical)
PU System efficiency = (Motor)*(Drive)*(Fan)*(Belt) = 0.96*0.98*0.50*0.88 = 0.414
Now, let's work really hard at the motor design, and eke out another 1.5 percent, bringing it up to 97.5. .... PU system efficiency becomes 0.420. So the return on the system is approximately 0.5 percent for a lot of effort (and perhaps a 20 percent cost impact at the motor).
Instead, we'll leave the motor alone and put the effort and cost into the belt drive and get the same 1.5 percent increase: PU system efficiency becomes 0.421. A bit better, but still nothing to write home about.
Ahh .. but what happens when we apply all that effort into increasing the FAN efficiency by 1.5 percent? PU system efficiency becomes 0.426. Now we can see that the overall increase is about 1.2 percent!
The purpose of pushing for high- or premium-efficiency motor designs is because it's the easiest thing to point the finger at. (There's always more room to increase motor efficiency, right?) Kind of like the whole idea behind ethanol production: we choose to use a significant portion of arable land to produce crops that are not sustainable, are not used for food, and require more energy input than we can harvest as output at the end of the process. So why do it? Because it's good advertising - it makes it look like those in charge are doing "something". (And it doesn't overly ruffle the feathers of competing industries, who subsidize "those in charge".)
