Backup Power Schemes

wb8foz wb8foz at
Fri Aug 8 23:38:43 UTC 1997

Eric Osborne sez:
> OK, let's see if we can turn this thread from BBN-bashing into something
> a bit more constructive.  I've seen several posts in the past few days 
> concerning optimal power backup strategies, both short and long term
> (battery, diesel, and/or nuclear).  Anybody out there care to share your 
> strategies?  

Putting on my EE hat:

	48vdc string, everything running off it is the #1 best
	answer from reliability. Time proven by THE paranoid folks
	in the world, Bell System Practices. 
	But the initial expense, space, weight, safety aspects,
	ventilation; all make this unlikely for anything except
	a tariff-funded CO. And it need generators. You can not
	really store many hours of energy in oxides of lead; it
	just costs too much. [Last time I asked, RBOC CO's had
	several hours worth of battery; in theory long enough
	to get a semi-mounted unit there if the local generator

That takes us back to UPSi on equipment, and generators. Technologies
available are:

	Gasoline engine -- used for smallest. Mucho fire code hassles.

	Diesel. The old-line standby. Fuel is much safer to store,
	but needs tending. The block must be kept heated in cold
	climates if you want it to start. All sizes - Cat makes
	'em as big as you want -- I've helped tend a pair of
	600kw units in a third world county....

	Gas Turbine. Not very fuel-efficient, but much less routine
	maint than Diesels. Also smaller.

	Propane fuel
	Natural Gas

All share the same hassles to some extent or another. They have to
be run, UNDER LOAD, an hour+ per month. They need the oil changed.
They need clean fuel; #2 Diesel tends to grow weird bugs that clog
the filters. The propane and natural gas can feed modified gasoline
piston engines and turbines. Some Diesels run on a fix of #2 and
gases. [The ultimate example -- a sewage plant will recover sewer
gas and use it w/Diesel. If your userbase is full of BS; or your
tie curls and your boss has 2 horns, you might go this route...] 
Natural gas has advantages of no storage hassles; propane does
not go stale.

In short, they all need tending. Regularly. 

As for installing, there are a million details. Ventilation. Fire
codes. Noise & Neighbors. Floor loading. Power transfer. Load
segregation [what is, and what's NOT, an emergency load...]
Hire an engineering fire with experience in your locale -- this
is not a task for anything less.

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