let me take a stab at explaining what this crackpot mobile_bob has in mind,,, hey
wait a minute i am that crackpot!
the system that i outlined is just that an "outline"
it is based on several hundred hours of testing in my garage to determine exactly what the specific fuel consumption
of a specific diesel genset is under various loads, conditions, rpms, various alternators, both AC and DC generation
various battery technologies, various battery voltages and various inverters, and various fuels.
my conclusion is based on testing data, and not based on "feelings" "theory" "manufactures claims" "fokelore"
"instinct" "anecdotal evidence" or anything other than what can actually be measured in the real world using quality
instrumentation, using scientific method and, done in such a manner that it could be duplicated by somebody else on
the other side of the planet.
now with the preface out of the way
what sense does it make to buy a 12/1 or 12/2 to provide for intermittent loads and then have to run it the vast majority of the
time at part loading? a typical 12hp engine will burn 2.5 to 3 times the fuel per kwatt hr to cover a 1 killawatt load, than it will
per kwatt/hr to cover a 6-7 kwatt load.
so if you build a genset that is going to run a significant amount of time, and will be installed in a typical house it will end up
burning far more fuel lopeing along at part load most of its life, just so you have enough hp in reserve to cover the intermittent
loads such as starting and running a well pump, or running an A/C system (where the compressor cycles off and on)
all i tried to illustrate was a method of covering those heavy intermittent loads with a unit that was sized properly to cover the loads
that are typical of 90% of the day.
now on the surface this system might seem overly complicated, but the reality need not be
for instance
take a small diesel engine like a 6hp r175 changfa (cheap and reliable) maybe 500bucks
attach a 110-555jho alternator about 175 bucks
put in a set of trojan/wally world t105 batteries for 12volts and 440amp/hr maybe 400 dollars?
get ahold of powersolutions, last i heard he had some 3kva inverters for 200 dollars
put together a simple controller, based on a bs2, pic or your fancy
or have a kid put one together for you maybe 100bucks
so for 1375 dollars you got a basic system that will do most of what i am talking about
and the efficiency will be just a bit better than just running the engine to directly power the loads
because as you so aptly noted the conversion steps added take away from efficiency, but
what i didn't tell you was the same alternator can be modified and applied properly to produce
24 or 48 volts and do so at an efficiency that meets and in some cases exceeds the efficiency of an ST head
now the system exceeds the efficiency of a standard 6/1 driving an st head on a continuous basis. or drive two inverters
and exceed the efficiency of a 12/1 or 12/2 and
have a better surge capability and short term overload capacity as well (measured in minutes based on load a battery capacity)
also yes, wind, solar and hydro could easily be plugged into the system to further increase efficiency and usefulness.
oh and lest i forget,, you got nice and stable flicker free 60hz, stable 120volts and depending on inverter a cleaner
sine wave than the utility and certainly better than any generator can deliver.
what i have outlined is nothing new, it is not even my idea, although i wish it were and i had the idea patented.
now then lets go a bit further on pricing
if a guy is patient and keeps an eye out, there is alot of stuff out there that comes up from time to time
i just finished collecting the final bits of an exeltech mx series redundant inverter system, with 10kwatts of capacity
and a 3 second rating of 22kwatts (for starting that tough well pump, etc), the set retails for right at 13 grand as configured
and i got it surplus for just over a grand with shipping.
if you develop good relationships with suppliers you can get really good deals on engine's, i know because i just passed on
a good deal to a fellow board member on a 25/2 listeroid a few months back, he got it for about half the going rate for one.
same goes for alternators, i picked up two 320amp leece neville alternators off of ebay a year or so back
for 300 each, they retail for over 2200 each
the 110-555jho alternator i referenced are on sale at some truck dealer every month for about 160bucks new out the door
no core price, for a 160amp unit that is about as tough an alternator as ever has been built and lightyears ahead of any car
alternator bar none.
now in closing,
does this make sense for everyone? certainly not!
i wouldnt recommend this to someone that only needs backup power once every year or three for a windstorm outage
of a few hours or days.
does it make sense for an offgrid application? yes definitely!
i have all the test data to prove that there is simply no way running any engine, or any genset, whether diy or one from the eom
genset manufactures that you will meet or exceed the efficiencies available with such a system as i outlined.
honda , yamaha and others came part way to where this system is with their inverter generators, tie in a battery bank and they
would be there if not for being optimized to run without batteries.
perhaps this is too complicated for some folks? perhaps it is not in keeping with the KISS principle?
bear in mind that today's cars are loaded with computer controls and they do a pretty good job, reliably and efficiently
given the epa constraints they operate under and...
they are complicated as hell, anything but KISS, and no way would i want to sit down and try to explain to you or anyone
how each system works and why it is needed,,,
although if pressed to do so i could!
bob g