Looking for advice on datacenter electrical/generator

Robert Boyle robert at tellurian.com
Sat Apr 5 05:11:30 UTC 2003

At 06:25 PM 4/4/2003 -0800, you wrote:
>     > http://electrochem.cwru.edu/yeager/ohiofuelcell/Norrick-Cummins.pdf
>You're right, that's really good reading.

It is interesting to see where they think backup power generation is going 
and the current ratios of operating costs vs. purchase costs vs. fuel 
availability vs. power outputs and duty cycles.

>     > interesting unit which uses propane and/or natural gas mixed with 
> the air
>     > to extend the runtime by adding significant BTUs from the gas. 
> However, it
>     > can run directly on diesel alone should the gas supply be 
> interrupted for
>     > some reason. Very neat technology and obvious after the fact, but 
> much more
>     > expensive.


This is one manufacturer of the control systems. We currently have enough 
diesel fuel to run for about 10 days without refueling so I couldn't 
justify the 2-3 times higher expense of a bi-fuel genset.  Apparently, 
pretty much any genset can be modified for bi-fuel operation without any 
internal modification. The other advantage to bi-fuel systems is that the 
slew rate problems of lp/ng gensets are completely avoided. For those who 
haven't seen or heard of problems with natural gas or propane powered 
gensets, this is another argument against them. We heard from multiple 
genset vendors of slew problems and several actually refused to sell us gas 
gensets when they learned about our application - powering high inductive 
loads (A/C compressors) as well as UPSes with computer equipment. 
Apparently as the load changes based on cooling equipment cycling on and 
off, gas generators (even with electronic governors) have trouble keeping 
the RPMs constant. Cummings specifically stated that diesel gensets don't 
have this problem due to the higher slew rate and more accurate RPM control 
due to the higher energy density of diesel fuel - just another data point. 
He also noted that the bi-fuel (diesel/gas) systems did not exhibit this 
problem either.


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