thinking of a redesign of my proposed system

[mobile_bob]

having made the move, and about half way done with what needs to be done around here, i am now starting to think about
the cogen system that i originally designed for an offgrid home.

because life has a way of sobering one up with a dose of reality, as most here know i ended up buying a place in a small kansas town
so this means i will avail myself to the local utilities, however i am thinking that perhaps i need not be tethered to them completely.

piggybacking on the nat/gas or propane based prime mover topic, i have been doing more thinking along the lines of the use of nat/gas
which is connected to my place. it makes economic sense to use this fuel for several reasons at this time. cost, availability, shelf life, are but a few
things that make it attractive for use as a fuel along with a much cleaner exhaust which makes our friends at the epa and my neighbors happy.

i have some solar PV panels along with inverters but am short on the battery end of things,

this has got me to thinking seriously what do i need batteries for? how much battery bank do i really need? and what are my alternatives.

i am coming to the conclusion that i really do not need massive amounts of storage capacity, and i don't need some expensive exotic technology, simple lead acid batteries are still about the best bang for the buck as far as i can tell.

my thinking is as follows

1. no battery technology is not 100% efficient, 85% is about average efficiency, charging and discharging for lead acid, worse than that for
nife (edison cells) not sure about nicads or lithium ion, etc, but my bet is none of them are much better in efficiency.

2. if i accept that there is an efficiency issue, then why operate a system that is subject to this problem any more than necessary? basically if the batteries need recharging the cogen must do it, or another source must take up the job

3. i have the ability to schedule most all of my loads, spread them out to take advantage and to optimize the efficiency of my power system.

4. i have the grid to use as a fall back, backup or provider of surge power,

5. i can automate the system, in such a way that scheduling loads, and providing power for those loads could be managed in the most
efficient and cost effective manner in real time.

now the fun part, and departing from everything i have learned and been a proponent of

that being deep cycle batteries...

if i am to recharge a battery bank, my best use of a system would be not to use any more battery than is necessary to allow time for the cogen to start/stabilize and then cover the load.  this could be done in less than a minute and with a bit of auxiliary heating less than 30 seconds. so the question becomes, which battery technology is best suited for very short duration higher amperage output? the answer is the venerable starting battery.

yes i said it, i am contemplating the use of starting batteries instead of the more commonly suggested deep cycle battery.

my thinking is this, starting batteries can handle the short duration high surge requirement of my system, if i size the bank so that under
the worst of circumstances the discharge is no more than 10% (in keeping with their design parameters) i also can recharge them using much higher current levels than is typical of their deep cycle counterpart.  the starting battery because of economies of scale in production and the fiercely competitive nature of the market are about the lowest cost battery available as well. their lifespan is typically 5 years or more if one keeps the discharges under the top 10%  again in keeping with their design parameter. they can also deliver very high surge currents without damage, and do so over and over again.

so i am thinking of a modification of my original design, which really amounts to just getting my head around the problem, reprogramming the controller for load management, and a simple reprogram of the balmar switching to starting from deep cycle regime.

the overall increase in efficiency due to not using a battery to provide for loads when the cogen could do so, factoring in reduction in fuel consumption, lower battery costs, and a few less important factors has me thinking that the end result would be a very competitive system.

the system will still be 48volt nominal, building on what i have learned in gaining efficiency in the charging system and the fact i already have
the inverter system of that voltage, the solar capacity will dovetail nicely as well.

the final piece of the puzzle is finding out if there is any buy back programs in kansas for generated power, if not from cogen burning natgas
then for PV.  in any event it would not be at all difficult to provide the switch gear (which i have already) and control that with the load management system so that i can at least take from the grid what i need when i need it.

still thinking, and hoping to be installing the system before this winter when the waste heat would be easiest to use.

bob g

[LowGear]

What has a better bang for the buck than Grid-Tie?  You're going to have to pay those pesky club membership and billing fees whether you turn one 50 watt bulb on or run clothes dryers for "white noise" when you sleep at night.  Just always use a bit more than you give back.  There might even be some state or federal grants in there.  And grid power when you need or want it is just plain yummy.

Casey

[mobile_bob]

Casey

i am considering that as well, just wanted to include the battery system for continued research and development for use
in a true offgrid home.  recognizing of course that starting batteries are not suitable for offgrid use, in the classic sense.

bob g

[Tom Reed]

Hi Bob,

Glad to see you're back in the saddle again! Always enjoy reading your posts. If it were me, I'd use AGM batteries. They will accept a much higher charge rate, still allow for deep cycle if the grid goes down and they will probably have 1.5x the life of starting batteries. No maintenance required either.

[LowGear]

Tom:
     I dream of AGMs in my electric ATV but this first go around I'm staying with the cheapski lead-acid for testing and theory development.  The small marine deep cycles at Costco are about $70 and have a nice return program.  The AGMs are over $125 if I remember correctly.

Bob:
     As I remember; your shop is downstairs with a concrete floor.  I'll bet you'll have more company this summer than you've ever had in your shop before.  Kansas, a place with real seasons.

     And yes; it is nice to hear from you again.  The voyages between Tacoma and Kansas were really interesting to me.  But I was never debriefed.  Would you share the three smartest things you did and the the other three at the far end of the decision list?

Casey

[mobile_bob]

thanks Tom, i have considered going with AGM batteries as well, having used them in testing i like their ability to absorb
a bunch of amps quickly, their being sealed is nice too.

Casey

3 best and 3 worst huh?  boy now that is something to think about alright!

i think one of the best and also one of the worst turned out to be the same thing, that was the use of a shipping container
to make the move of all of the heavy stuff.
it was good because i could move a lot of stuff efficiently, on the other hand because i was forced to move before i was ready i didn't make
the best use of the available space or weight capacity. 
what i learned from that experience, is a shipping container moved by carrier to a rail head and shipped across the country and delivered to
the destination is about the best way of getting it all done, however take the time to carefully load and distribute the weight very well to get the most bang for the buck.  i probably could have saved myself one trip moving household stuff which is bulky but relatively light had i had the time to load that stuff in the container,,, i had more than enough room and enough weight capacity left to have done the job.  also of note was the condition that things arrived in, their was very very little shifting, almost like it floated from tacoma to kansas. nothing got broken even though many things were not properly secured.

so there is #1 best and probably one of the worst

#2 best was renting a true all terrain forklift, one that looks like a tractor mounted backhoe, sans the back hoe attachment and the bucket in favor of the forklift mast assy.  they are wonderful for lifting heavy stuff, traveling over rough, muddy, uneven terrain and all around a time and back saver.  coincidentally using a smaller hard rubber tire forklift on anything but concrete is just a horrible experience all in all.  so i guess that turns out to be one of the best and worst decisions

#3 has to be the lack of time to dispose of some/part or maybe even all of this crap before the move, seriously how many engine's does i guy really need? ( ok maybe all of those) but looking back i could have sold a couple vehicles, such as the isuzu npr had i had time to load out the household stuff in the container, the 55 chevy only because i have had it forever and likely will never get around to finishing it...


all in all it got done i guess, would i do it again? yes,
would i do it differently? yes

buying this place at least to this point has been one of the best decisions i ever made,  albeit my neighbor across the street has 21 weiner dogs
but even they seem to have gotten used to me and don't raise the roof ever time i walk out of the door anymore.

don't know if that answers the question or not?

if something comes to mind that is noteworthy i will post it.

bob g

[BioHazard]

That's what I've been thinking about for a long time now, working together with the grid. I only want enough batteries to get the right voltage and stabilize everything. I only need a few kilowatts output and everything that surges higher will stay on the grid. No sense in building a system that will run my welder when I've got a standard outlet right there. I need to sprinkle a few solar panels around just so the power company will give me a netmetering setup. Hopefully they don't ask why my solar panels are generating a few kilowatts in the dark...

Basically my plan is to only run the cogenerator whenever heat is needed, with electricity being a useful byproduct.

[BruceM]

Congratulations on the move, Bob.  I hope your new place works out well for you. 

A basement shop sounds nice and cool for summer, and pleasant in the winter.  Having grid power is a nice thing-  makes many things possible and easy that are a pain for off grid.

I'm using the Johnson Controls (Walmart) group 27 marine batteries. Started with them as I didn't want to use an expensive set (10 in series for my 120VDC system) for my all new prototype electronics charge regulation system. I stayed with them as they work adequately and I can't beat the price. I got 4 years service but the charge efficiency sure is dramatically different as they age.  This is just the natural "death by age" according to a Johnson engineer. I'm on my second set.  Since I have <10% DOD I suppose I could try starting batteries to see how they fare, but I have a few years to think about that decision.  Charge efficiency for the top 10% of charge is about 60% for young wet batteries according to Sandia Labs.  It took nearly 3x longer for my 4 yr batteries to charge, so maybe the charge efficiency declines to 25%?  I don't think anyone has tested AGMs for relative efficiency on the last 10% of charge.  For experimental/development work, though, it hardly matters.

[mobile_bob]

BruceM
one of the things i want to test is charge efficiency
realizing the last 10% is the least efficient area on the graph, i am left to wonder about
cycling my 10% usage out of the area between perhaps 80-90% SOC

i also realize that this will lead to hardening of the sulfation should i not top off or completely recharge the batteries
what i am unsure of as it relates to starting batteries is how long does it take for the sulfation to harden and become difficult
to break back down when recharged.

a good true deep cycle flooded cell need only be completely recharged once ever 10 days or so, and with periodic equalization they
do very well.  just not sure if the starting batteries respond the same.

my hope is they would perhaps i might have to top off more frequently, but hopefully not every day.

the charging efficiency is much better between 80-90%SOC than it is from 90-100% SOC, so i am really interested in testing for use within
this area of operation.

i only need 48volts, so my exposure is less than 400 bucks initial investment, that for group 31 screw post ~950cca batteries, they are very common in heavy duty trucks and because of economies of scale and the market place with dealers competing there is always one of the dealers with this battery on sale somewhere.

my thinking is "if" i can get 4 years or maybe 5, and do what i need done, the cost of the batteries would really be quite inconsequential.

i drink more coca cola in a week which is bad for me anyway, so maybe i divert my soda money to battery money? 

BioH:

because i bought a place in town, and having utilities it just makes sense to use them, just do so in an efficient manner. also it would allow me to do more apples to apples comparisons between what it takes to provide for my hope via utility vs my system (which would be very difficult and subjective if i were fully offgrid).

i am with you when it comes to powering things like welders, why build a system to power than when portable gas drive welders are common as dirt and very reasonably priced used. besides they make a pretty good backup generator as well.  even if i were to plug into the utility, unless i open a welding shop/production shop, how much will the utility cost really be?  likely less than 5 bucks a month for what i need. hard to compete with that in my opinion.

bottom line is this, having the utility to use as a back up gives me the time to work out a good system without having to sweat it.  then should the utility go down, i choose to unplug, or something worse happens, it is a simple to seamlessly go on with life.

bob g

[BioHazard]

Bob - what do you plan to use to charge your batteries at 48v and what are you going to use as the prime mover with natural gas?

[mobile_bob]

i am pretty much set on using the s195 in dual fuel mode, using pump diesel as the pilot fuel and nat gas as the bulk
fuel.  that is to start with.

after i see how that works out, i will then swap out the idi engine for one of my di engine's, and fit it with a spark plug, mixer/carb
and governor linkage and see how that works out. should it prove to be too high of compression for nat gas, i will then swap the cylinder
head for the idi head which should drop the compression ratio to something around 12-13:1 and see how that works out.

as for charging,  i will likely go back to the venerable 110-555jho, i have a pair fitted to the trigen now, however the drive ratio is a bit slow to
get to 48volt charging at the 1800rpm engine speed using only the output of one  of them. therefore i plan on doing the deal using both alternators hooked up in series.  that should give me about 6kwatts of charging capacity, which is likely more than the engine can produce burning nat gas. if i have to lower the comp ratio, and maybe just about right should i be able to keep the compression ratio up to the factory 20:1 ratio.

it all depends on the quality of the nat/gas and what other lower and more volatile gases might be part of the nat gas around here.

in all honesty, i should probably look to a different and first world prime mover, however if we ever have a chance with getting the epa to grant an exclusion it will come on the proving that the changfa can operate on nat gas and do so cleanly.

and there is only one way to find that out for sure, that is build the thing, and take it in and have it tested.

i am thinking maybe, just maybe if it can be shown that the engine can meet emission standards as tested at an automotive test station, maybe with the slip as proof and the fact it is used in an intermittent run cogen application, with the epa loving the cogen idea, maybe they would grant an exclusion?

probably not, but there is a better chance than ever getting them to approve a diesel for import ever again.

imho
bob g

[SteveU.]

Hi BobG
Sounds like a sound plan of action.
Important rule of life: what you have is at least twice as good as something you would have to go out and acquire. So before a fellow jumps ship, ditches what he's already got the new better be 3X as good. Best said in the song lyric, "When you can't have the one you (would like to) love . . . Love the one you got."

When/if you ever get to spark converting read this article first:
http://gardentractorpullingtips.com/ignition.htm
Good info in the beginning of this long link rich article. At least skim the center section on existing B&S and others systems to see how they handled cranking spark timing versus running spark timing so you do not break a starter or cranking arm. The real meat is toward the end with his recommending converting to battery powered ignition triggered by now common crankshaft mag sensors amlpified through rock solid, very cheap and common late 70's, early 80's American automotive ignition coils and ignition moduals. He covers all of the big three with diagrams: Chysler/Dodge, Ford and GM. Lists current parts store new PN's and principal vehicle applications for wrecking yard scrounging too.
Battery ignition mag triggered will give ~2x the spark duration. Battery powered Hall sensor triggered ~3X the duration over point/small engine magneto.

Now about 1st world quality currently available water cooled small engines that are already EPA certified  . . .  this is for those for those still without and still looking take a look see at the specs listed here on these Kubota Mini series:
http://www.countrysalesandservice.com/SuperMini_engines.html
2 and 3 cylinder Gasoline, Propane and Diesel engines all based off of the same blocks. Good comparison of specs for continuous power, torque and fuel consumption. Looks real good if ran at 2500-2800 RPM. I have personally used the DG972 three cylinder set up for methane, on methane, propane and woodgas. the smaller 752 seties is not as popular and are now being priced way down new by most of the dealers.
Interestingly for spark ignition on these they ARE useing a battery powered Hall sensor, crankshaft trigger wheel, indivudual cylinder coils and a Denso amplifier/controller. Never got around to timing light verifing if the Denso control modual had cranking versua running timing control. From the easy cranking and sweet loaded running I suspect it did.

Regards
Steve Unruh

[LowGear]

BruceM.

     I found your

I'm using the Johnson Controls (Walmart) group 27 marine batteries.

interesting.  I'm shopping Costco for the same product only to run a DC 36 volt motor.  The group 24s are about $20 cheaper at about $60.  Man do they fit easier.  How much do you believe it's going to cost me in the "pay me later" part of the scenario?  That would mean working life as well as performance.

Casey

[BruceM]

Hi LowGear,

Life is directly related to DOD for well cared for batteries that don't die of sulfation or overcharge plate erosion. The "marine" batteries we're talking about are not true deep cycle.  I don't recall the data I was given by Johnson Controls a few years ago very well, but I think you'd be lucky to get 150 cycles at 50% DOD.  You can assume that even if they are rarely used but kept on trickle charge after 3 years the capacity will likely be unacceptable if you needed 50% of capacity or more, because they won't have that much left. 

I don't think anyone uses this type of battery for a golf cart, because the cycling would be too deep and regular for them to last even one season. If you were expecting use similar to a golf cart, then you'd best look for a series set of Trojan golf cart batteries.

If you use will likely be much less demanding, I don't see the harm in trying out a cheap set.  Just remember that for these "marine" batteries, the stated AH figure is for a 1 amp draw.  So at say 20amps, you'd get about half the listed AH .

[uber39]

Hello all,
       until recently I've been running Trojan T105's in an electric car (Daihatsu Mira/Handy Van,72v dc) trying to look after them ? I would average 45-50 miles to a charge, battery set would last aprox 15000 miles,tried US Batt equivalent and got 7000 miles,( most not happy, batts not even good enough to move over onto house. There DEAD!!!! ) 6 months ago moved across to lithium ion. So far nothing but praise but another 18 months will tell. All I'm saying is some batts are a lot better then others.
       
       Ian