The US has fairly strict air quality control laws. It is
relatively expensive to operate a desiel generator more
than 100-200 hours a year in a major urban area due to the
permits and environmental pollution control requirements.
In most cases, it is less expensive to use utility power
in the USA, and generators only for backup. With the
California power situation, several people have done a
lot of research on the trade-offs between utility and backup
power.
The result is, except for disasters, most backup generators
are not regularly operated for extended periods.
Before their budget was cut, the Department of Energy had
a great Backup Power Working Group. You can read the
results of their work at
http://www.dp.doe.gov/CTG/bpwg/bpwg.htm
You should remember that generators are mechanical devices.
Wear and tear during extended run-times *WILL* result in
breakdowns. The longer your operate the generators, the
more failures you will experience. Its always a trade-off
between how long you test mechanical equipment. Based on
DOE studies, many people actually over-test their backup
generators.
Standard Bell telephone CO design doesn't assume extended
disasters. Some colocation facility designers have designed
their generator plants differently than normal Bell practice.
But even colocation facility operations need to set some
limits to their design conditions.
Locations with power problems
25 Broadway
32 Old Slip
ATT Local Service (WTC basement)
Sprint/Sprint PCS (location unknown)
Locations destroyed
Verizon/Genuity WTC
Until I know what happened, and read the final report, I
can't say if any particular design could have performed
any better.
In our new datacenter in Newton, NJ, we are in the process of getting RFPs to install Capstone micro turbines for backup power. They are DESIGNED to run for 8,000 hours before the first maintenance is needed. At 333 days (8k hours) an airfilter should be changed. They can run for 60 months 24/7 before a rebuild is needed. They need a tuneup kit at 24 and 48 months (assuming 24/7 service) at a cost of $2700 per service. They are impressive units, but... 1. They give off extreme amounts of heat (which can be used to heat your building), 2. they rely on natural or LP gas. 3. they are VERY expensive compared to diesel gensets - 2-4 times as much per Kw! A 60kW unit costs $69,775 A 28kW unit is $45,582. They can be ganged together to provide N+1 redundancy and load sharing.
http://www.capstoneturbine.com
I have no financial interest in the company, but they seem to be the only game in town with a unit with EXTREME runtimes. Does anyone else use these at their datacenter(s)?
-Robert
Tellurian Networks - The Ultimate Internet Connection
http://www.tellurian.com | 888-TELLURIAN | 973-300-9211
"It is never too late to be what you might have been." -George Eliot
[ staying from nanog to power-generation again... 
]
Gas (LPG [propane] or Natural Gas) burns far more "cleanly" that Diesel does.
due to this, you have far longer periods between maintenance, as there is much less that needs to be changed on the engine/genset.
that's the good part of it.
the bad part of it is that:
- there is less 'energy' in Gas (LPG or Natural) versus the equivalent weight/volume of Diesel.
(in technical terms, the "net calorific value" (the amount of energy per gram) is lower for gas
versus Diesel). that means that you need more of it to generate the same amount of energy.
(read: it burns more to generate the same amount of energy)
- Gas is typically harder to store lots of than Diesel. LOTS harder.
one of the 'nice' properties of Diesel is that it doesn't catch fire easily. (except under extreme
temperature or extreme pressure, or both).
you most definitely cannot say the same thing about Gas.
[in power-station-construction, this is a huge plus for Diesel. boilermakers and welders could
go about their job, even if there was a pool of diesel from leaks in a newly installed
generator. :-)]
many Diesel gensets can be "converted" to operate on LPG/Natural Gas instead.
they typically end up with a higher operating temperature (but not significantly so), and may need some upgrades to some of the auxiliary equipment (fuel pump, cooling system / heat-exchangers / radiators), as well as some relatively minor mods to the engine itself. you also need a Governor that knows that its using LPG/NG rather than Diesel - the characteristics of how the engine behaves/responds are quite different.
on the topic of Oil Filters, one of the things that can be done to help "clean" the oil in a Diesel genset is to add a Centrifugal Pump to seperate the solids from the oil. this makes it possible to extend the maintenance periods (at least for Oil Filter changes) of Diesel gensets as well as improve the lifetime of the oil itself.
(Diesel gensets are fairly oil-hungry. that is normal).
cheers,
lincoln.