Re: Whole house generators (slightly OT)

["BruceR" <razrbruce@xxxxxxxxxxxxxxx>]

Diesel sounds good but I'm told I may encounter permitting and delivery
problems. The benefit of NG/LP is that as long as the NG line is
operating I have an unlimited supply of gas. The LP would be a backup
only.  Most of the outages here are not the result of an islandwide
disaster such as hurricane or earthquake but more likely a downed
transmission line, a "brownout" or a car taking out a pole so NG
delivery is unaffected.

 Marc_F_Hult wrote:
> On Tue, 17 Oct 2006 15:42:41 GMT, "BruceR"
> <razrbruce@xxxxxxxxxxxxxxx> wrote in message
> <RR6Zg.13181$gU6.10463@xxxxxxxxxxxxxxxxxxxx>:
>
>> So, I think it's time for big honkin' generator to serve the whole
>> house.  I've been looking at the Generac line and I'm considering a
>> 35,000 watt unit to serve my 200amp home.  I'd appreciate any info or
>> suggestions that any of you have to offer.  I'd like to run it off
>> Natural gas with LP gas as a backup.
>
> When I was using generators to power scientific labs in the field, I
> quickly gave up on carbureted generators (gasoline, NG, LPG) because
> they were too slow to respond to load changes caused by air
> conditioners and pumps. When a heavy load kicked in, the UPS's
> powering the electronics would cycle. Eventually the batteries in the
> UPS's would become discharged and the lab electronics would recycle
> or worse.
>
> This was in the 1980's and NG/LPG/gasoline generators may have
> improved, but ABIK, the physics still favor fuel injection.
>
> Diesel, which is always 'fuel-injected', is fast to recover from a
> load because at 1800 rpm on a 4-cycle engine, there are 450/60= 75
> injections/sec (i.e., opportunities for load adjustment) so with
> electronic fuel injection, the amount of fuel injected can in theory
> be adjusted for every AC cycle. This in turn reduces the nominal KW
> rating of the genset that you actually need to buy compared to
> NG/LPG/gasoline.
>
> (Thar's steady-state KW's and then thar's *real* KW's ...  ) Big
> flywheels help a lot, but I found no useful comparative specs on
> _dynamic_ performance. Hopefully this has changed for the better.
>
> Since you are planning to allocate space for backup LP cylinder(s),
> you would may not lose space with diesel compared to the NG+LNG
> approach, esp. considering that the energy density of diesel is about
> 50% higher than that of LPG, so combined with the requirement for
> cylindrical (not rectangular) LP tanks, you can store twice as much
> energy in the same volume/area with diesel than with LPG. IME, with
> good housekeeping diesel fuel isn't unacceptably smelly.
>
> ... Marc
> Marc_F_Hult
> www.ECOntrol.org