# Starting with a Blank Slate - what would you do differently?

E

#### Ecnerwal

Jan 1, 1970
0
After a couple of years of construction and recovering finances, I'm
getting nearer to buying significant parts of my off-grid system. Some
parts will have to be staged purchases as more money comes in, but the
initial chunk of battery, first inverter, charge controller, one string
of panels, and all that interconnection NEC meeting "stuff" that ends up
costing a lot more than it seems like it should.

At present my offgrid system consists of an unsuitable generator (3600
RPM welder/generator, air cooled) and a bank balance.

As far as I can tell, an installation in Vermont which is off-grid gets
diddly for rebates, tax breaks, etc. Location is SW Vermont, wind
potential stinks (84 foot straight-growing trees), likely solar + fuel
for a good long time since solar alone would blow the budget (though
fuel prices are right up there at the moment with no signs of dropping).
Going to have to lay waste to more trees than planned (not a big lawn
fan) to get sun in for panels. Only hope for microhydro would be very
micro - if the gravity well pans out and has noticable excess water.

Good or bad experiences with cut-rate internet dealers welcomed - good
experiences with dealers local to me also welcomed - I may well have
missed some. Cash is definitely a limiting factor - the budget for the
inital phase is probably not much more than $12,000, assuming no surprises with other aspects already budgeted. I admit to being somewhat bemused by the wealth of PV cells which tout being cheaper to make, yet which cost more per watt than other products they are supposed to be cheaper than (eg, Unisolar, Evergreen). My inital application is a bit odd .vs. typical offgrid houses - the first building up is the shop. It will have need of some pumping capacity for radiant heat (probably a couple of ~125 watt pumps, duty cycle not certain), and sporadic use of up to 3-4 HP worth of motors, along with as much as a kilowatt+ (even if it's _very_ efficent, slow-starting metal halide - a few dim CFs just won't cut it) of lighting. It might sit for most of a week (or longer) doing nothing but running the heat, and then get used for several hours of motor-heavy work - a low average, but high peak use. Over time more typical house loads will be added. I'm strongly considering DC pumps for the heat, but that might limit me to 24V (or needing to fiddle about to get 24V from 48V). Thus far all motor loads can be run 120V (3-4hp is multiple motors at once). While many could be switched to 240V for less amperage, messing about with balancing 240/120V seems more complex than just sizing the wiring correctly for 120V. General thoughts are 48V battery bank, with a dedicated "power house" including a nice basement/vault for them to hide from the winter (and summer) in. All reading indicates that I should try to make the battery as big as I need for the next 10 years right off the bat, and that the ideal situation would be 2V individual cells in a single series string. Of course, many people seem much happier having switched to AGM or gel batteries (which don't appear to come in 2V cells) and the lowest starting cost option of golf cart batteries is 6V and high maintenance with a likely need to run several parallel strings, with associated equalization headaches. A liquid-cooled diesel generator has been in the plans, but is becoming more questionable as the price of all forms of petroleum shoots up. I will no doubt start undersized for panels, and then have to plan to add them in chunks over time as more money comes in (I have a practical aversion to loans if they can be avoided - saves a lot of money on the long run). Presumably this will mean needing to run the generator to top up the battery some, as well as to support the major loads if run for much length of time in the early phase. PVWatts indicates that Nov/Dec are the worst months - sounds about right for the cloudy VT weather. I'm mostly looking for ideas about what you would do differently if you were starting with a blank slate, within the context of the general background information I've provided to make it less a purely vague question. Aspects like detailed system sizing are inherently somewhat vague, as it's not just a matter of household appliances with predictable use times and power draw, nor much room for "reduce power use first" with motors that inherently need a good deal of power (even if they could be 100% efficient, which they cannot). N #### [email protected] Jan 1, 1970 0 Ecnerwal said: At present my offgrid system consists of an unsuitable generator (3600 RPM welder/generator, air cooled) and a bank balance. You can quickly convert that pesky bank balance into PVs ...wind potential stinks (84 foot straight-growing trees)... Aka "towers"? My inital application is a bit odd .vs. typical offgrid houses - the first building up is the shop. It will have need of some pumping capacity for radiant heat (probably a couple of ~125 watt pumps, duty cycle not certain), and sporadic use of up to 3-4 HP worth of motors, along with as much as a kilowatt+ (even if it's _very_ efficent, slow-starting metal halide - a few dim CFs just won't cut it) of lighting. It might sit for most of a week (or longer) doing nothing but running the heat... I'm mostly looking for ideas about what you would do differently if you were starting with a blank slate, within the context of the general background information I've provided... How about a sunspace over the insulated south wall of the shop, or some polycarbonate "solar siding" to make an air heater to lower the heating fuel bill, with a few small windows and lightshelves near the top of the south wall to provide light? Full sun is about 10K footcandles. A well-lit office is 50, 200X less. Nick N #### [email protected] Jan 1, 1970 0 Harry Chickpea said: One idea might be constructing a large bin in the shop area on top of an EDPM lined pan, using hardware cloth and rebar to contain the small angular rocks that make up most grout. Sounds great So this "grout" is pieces of marble...? This bin would then be sealed with a layer of gunnite over the hardware cloth, How about a simple EPDM cover? The bin would receive the exhaust gasses at the base through a manifold. The rocks would absorb the heat and condense out the water while the generator was operating... The rocks could provide lots of surface. The box might also have a few hollow concrete blocks to lessen the airflow resistance and a few plastic 55 gallon water drums to store more heat in the same volume... The bin would then slowly release the heat to the shop during the rest of the week. This box could do a good job of collecting heat, but the rate of heat distribution might be increased and controlled with another room airpath inside the box to extract heat, vs just letting heat leave via the walls. Nick B #### Bruce in Alaska Jan 1, 1970 0 Ecnerwal said: After a couple of years of construction and recovering finances, I'm getting nearer to buying significant parts of my off-grid system. Some parts will have to be staged purchases as more money comes in, but the initial chunk of battery, first inverter, charge controller, one string of panels, and all that interconnection NEC meeting "stuff" that ends up costing a lot more than it seems like it should. snipped for brevity..... Things I would do different, if I had it all to do over....... 1. Any Inverter that is more than 3Kw needs to be 48Vdc.... My Trace 4024 should have been a 4048..... 2. L16's are great but real Industrial 2Vdc/cell Batteries are much better in the long run, and not that much more expensive... I really like my Absolyte II AGM 24Vdc 800Amp/hr Bank. 3. Any Geneset should be diesel, and NEVER be 3600 Rpm..... Real gensets are 1800 Rpm, or less, and have a real Pressure Oil system with BIG filters.... I have seen WAY TO MANY 3600 Rpm wonders die after a few hundred hours of operation. My Fairbanks/Morse 45B 2.5Kw 1200 Rpm really is sweet, as it uses a cup of fuel/hour at rated load, has a MTBF in the 40K hours, and makes more mechanical noise that exhaust noise. 4. Generate all the PrimePower at 240Vac and transform it down to 120Vac for the Inverters and 120 House Loads. Keeps the L1 & L2 Loads balanced by definition, and you can still have a 240Vac loads like Clothes Dryer, to keep the little lady happy. (Propane Dryer isn't an option as the cabin is heated with an Open Flame Pot Diesel Burning Stove) 5. Solar is great, but this far north it really only makes sense in the summertime, and then I would only buy them in 120+ Watt panels, and a MPPT Charge Controller with Three State Battery Charging, and Diversion Capability is really the way to go.... 6. Gensets should be all Liquid Cooled, and the radiators should be Hydronic Floor Heating Tubing, or Forced Air Heat Exchangers INSIDE the insulated living space. You paid for those BTU's when you purchased the "Dead Dinasour Guts", so why are you trying to heat the outside world with them..... You might never have to actually burn supplimental firewood, if you charge you batteries on a regular basis..... Well that's my list Bruce in alaska G #### G Wood Jan 1, 1970 0 I have 75 100 amp hour AGM batteries made by Dynasty Model number UPS12-370FR available. I also have all the connector cables and switches, circuit breakers etc for these batteries as well as stands on wheels. If you are interested, you can reach me at [email protected]. I live in Ontario, not very far from Vermont and would be interested in making a deal. E #### Ecnerwal Jan 1, 1970 0 I'll try one compact reply to several replies to my original post: Ron Rosenfeld asks about pump wattage and system sizing: My recollection of the power draw (125 watts) typical of the pumps that fit my curves; 9gpm, 12 foot dynamic head, off the top of my head - each driving 3 parallel loops of 3/4" id tubing 250 feet long - and I'm very happy I did not decide to use 1/2" tubing. I have not bought those yet, either. I could use 6 3GPM X 12ft head pumps, but this did not appear to be much better on power, and cost a lot more for pumps. There are only 2 zones, so 2 pumps appears to make more sense than 6. I'll have to make a call on system size (at least "as relates to battery") when I buy the battery. Everything else I'm planning should be easily upgradable without loss, and can thus start smaller than it will end up - present plan is Outback VFX3648 and MX60, both of which can simply be added to when/if original capacity is exceeded. I expect that it will be eventually, but buying multiples up front will be fiscally questionable at present. If the rest of it allows I might go for a pair of inverters up front, since I'm sure I'll need/want at least that many eventually. And I'll remember to oversize the battery interconnects with 4 or so in mind, so I don't have to go back and redo those at a loss later (unless I decide that the initial battery won't be around at that point, more likely if I decide to take Harry's advice to start with a cheap GCB setup for the first one on the assumption that I'll beat it (or the other assumption that I'll get started for cheaper that way, and have a much better idea of what I want when I replace it later with a "good one" for more money). Heat recovery is in the plan with the liquid cooled diesel genset - and this is one of many reasons (the rest of which Bruce covered with his usual great input - I've picked his brains on the subject before) the air-cooled 2-pole gasoline gen/welder is unsuitable. Just feeling temporarily depressed about any dead dinosaur guts with the prices all going crazy after Katrina, and have my doubts about WVO availability as anything to depend on long-term (especially as DDG goes crazy). However, putting the genset in the shop is NOT on the list, because the present one is (temporarily for the past 18 months or so), and I don't like it one bit. Much easier to move heat and power than to put up with noise; And I'll get better noise isolation with a sound insulated building and another 20 feet of distance than I do with a sound insulated room inside. I also prefer to keep both fuel and poison gasses out of the shop building as much as possible - not having CO in the building trumps detecting it, IMHO. Still, Harry has a creative approach that might appeal to someone else. I've got a lot of insulation, a hydronic slab, various heat inputs planned, and will use Polypropylene Glycol where needed to guard against unfortunate freezing incidents should something go wrong. That's already included in the head calculations for the pumps... I do have a scheme to collect exhaust heat, but it centers on a scrounged Weil-Mclain oil-fired steam boiler (which might be convertible to hot water) - I figure if I feed the diesel exhaust in instead of the oil gun, it should be a pretty competent heat exchanger (I know from painful experience with my tractor that diesel exhaust is plenty hot). My only nagging concern is some notation about keeping it above 120F to ward off "low temperature corrosion", which might be a problem with intermittent operation...the fact that it's considerably oversized (were it running the burner) to my heat load should mean it will be able to remove a good deal of the useful heat from the (cooler than a flame) exhaust. An ID fan on the stack is in the plan to make sure that the powerhouse and heat exchange area is not a deathtrap (and that will have detectors too). Nick has tossed in some random idiocy with some sensible stuff. I'll address the idiocy first: If I put all the cash in PVs, then I don't have any of the rest of the system - useless. If I hang a wind generator in a tree, it's still in the wind shadow of all the other trees - and the fact that the trees grow straight up is indicative of the low wind potential of the site. To get above the trees and tree turbulence would take about a 150 foot tower (minimum), and there are no 200 foot trees sticking up from the nice even ~85 foot canopy to be chopped off at 150 feet, guyed, used as a tower (...die from being topped, rot out and fall down, smashing expensive wind generator.) Just plain not cost effective for the piddling amount of wind available, not to mention maintenance and the hassles with the town (really quite laid back, but not about towers) to put any such thing up. Air and water heaters on south wall are in process, and it also has 6 great big honking windows (low-e, and they might get thermal shutters/hot air collectors if I can build something that's very easy to use - I know from past experience that window insulation which is a PITA is worse than useless.) The main shop floor has an 11.5 foot ceiling; the windows are 6x3 feet, ~5 feet apart (thats where the collectors go - sunspace considered and dropped earlier in design phase for several reasons) except for the center two which are quite close together to provide extra natural light at the workbench. But on dark days all this does not do it, even less at night. I've been in and hated a wide variety of windowless cave shops, and this isn't going to be one. I guess that covers Gary as well - while I do have a 10x10 insulated garage door, that faces east into trees and hill. There are two smaller windows on W and N wall, partly for light, mostly for egress. I thank you for your input, and await any further input based on experience - it is quite useful and can point out some of the subtler pitfalls. N #### [email protected] Jan 1, 1970 0 Ecnerwal said: Heat recovery is in the plan with the liquid cooled diesel genset... Liquid cooled is nice for cogen. Intelligen also added a stacked plate exhaust gas heat exchanger about the size of a softball to their 11 HP Lister-Petter diesel. I do have a scheme to collect exhaust heat, but it centers on a scrounged Weil-Mclain oil-fired steam boiler (which might be convertible to hot water) - I figure if I feed the diesel exhaust in instead of the oil gun, it should be a pretty competent heat exchanger... Sounds interesting. My only nagging concern is some notation about keeping it above 120F to ward off "low temperature corrosion"... Perhaps you can find a way to keep it 120 F or below, for condensation without corrosion. Intelligen's final particulate filter was a 55 gallon drum. Nick has tossed in some random idiocy with some sensible stuff. I'll address the idiocy first: If I put all the cash in PVs, then I don't have any of the rest of the system - useless. Can you say "humor"? PVs are hideously expensive... If I hang a wind generator in a tree, it's still in the wind shadow of all the other trees - and the fact that the trees grow straight up is indicative of the low wind potential of the site. To get above the trees and tree turbulence would take about a 150 foot tower (minimum)... Or fewer trees, at least upwind. Then again, if there's little wind... Air and water heaters on south wall are in process... Nice. and it also has 6 great big honking windows... More expensive and much less efficient on cloudy days than air heaters, eg "solar siding," eg 4'x12' sheets of$1/ft^2 Dynaglas clear corrugated
polycarbonate greenhouse roofing 6" away from a dark metal shop wall.
Ceiling mass can store sunspace heat, as in the Italian Barra system.
The main shop floor has an 11.5 foot ceiling;

A white ceiling with clerestory windows with lightshelves (reflective above)
above eye level could move lots of natural light deep into the shop...

Good luck

Nick

E

#### Ecnerwal

Jan 1, 1970
0
and it also has 6 great big honking windows...

More expensive and much less efficient on cloudy days than air heaters,[/QUOTE]

The windows are about light Nick, not heat. Low-e windows actually suck
for heat collection, but importing non-low-e triple glazed units (which
have better perfomance in a heating climate than double-glazed low-e)
was a multi-thousand-dollar-extra boondoggle I opted to not bother with,
as I have plenty of space to put up dedicated collectors to collect heat
with, more efficiently than windows. So, the collectors between them are
about heat, and possible collector on the face of possible shutters (for
when the building is not occupied, or at night) are about heat, but the
windows are about light. They run from ~3'8" to ~9'8", providing height
to get light in deep as well as egress and a view out. I considered
little windows up high and decided that that felt a bit too much like a
box I couldn't see out of. I considered adding some higher than these
ones, but the price of little windows is far more per square foot than
large windows, so I opted not to.

E

#### Ecnerwal

Jan 1, 1970
0
One other comment: Battery location.

You need to have real good ventilation to get rid of the hydrogen gas they
produce. If they are kept charged, you don't have to worry about freezing
unless the enclosure temperature gets below about -50°F

But I do have to expect them not to work as well (from cold) or not to
live as long (from summer heat). Dropping them in the ground solves both
of those problems nicely. The one concern I have about putting them in a
basement (of the powerhouse) or vault is possible problems from
condensation in the summer, when they are cool but the air is humid -
lots of grease on the connections, I guess.
Because of the hydrogen issue, you may not want to keep them in the

One more reason that the plan is for a dedicated powerhouse, separate
from living/working spaces. I suppose if I sucked it though limestone to
whack the tiny acid droplets I could pull generator intake air from the
battery room, ventilating it and using up the hydrogen, but the better
part of valor is a dedicated vent stack on that room. Acid is hell on
steel, and ruining engines is expensive.

N

#### [email protected]

Jan 1, 1970
0
Ecnerwal said:
The windows are about light Nick, not heat.

I realize that. Smuckers Harness Shop (an Amish enterprise) in Churchtown
PA is set up like this, with lots of south windows over workbenches, gas
lights, and an outdoor Lister-Petter diesel to run all the machines from
overhead shafts. They make harness for customers round the world, including
the Queen of England. They have 7 PCs in the billing dept. When a Phila
Inquirer reporter asked Mr. Smucker if the PCs would get them in trouble
with his pastor, he said "No. We also value local employment, and
the pastor is one our employees."
...I have plenty of space to put up dedicated collectors to collect heat
with, more efficiently than windows.
Good.

So, the collectors between them are about heat, and possible collector on
the face of possible shutters (for when the building is not occupied, or

I don't understand what you mean by shutters. I suggested "solar siding,"
ie a layer of clear polycarbonate glazing over the dark south insulated
shop wall, with an airgap and vent holes at top and bottom (maybe 5% of
the glazed area) through the barn wall with lightweight passive plastic
film one-way dampers to prevent reverse air thermosyphoning at night.
but the windows are about light. They run from ~3'8" to ~9'8", providing
height to get light in deep as well as egress and a view out. I considered
little windows up high and decided that that felt a bit too much like a
box I couldn't see out of. I considered adding some higher than these
ones, but the price of little windows is far more per square foot than
large windows, so I opted not to.

Views are nice, but you might also have some clerestory "windows" (which
might also be simple vent holes in the insulated barn wall behind the
solar siding) above eye level, with light shelves below... 1 ft^2 of
direct sun can provide good light for 200 ft^2 of shop, if it's well-
distributed. A white ceiling with reflective lightshelves below the
clerestory "windows" can help a lot with that, geometrically-speaking.

Insulating/reflective foamboard lightshelves that automatically fold up
to a vertical position at night to block the vent holes could be a bonus.
They might also partially fold up during the day to regulate light levels.

Nick

E

#### Ecnerwal

Jan 1, 1970
0
I don't understand what you mean by shutters.

A foam (or stress-skin, as I still have the holes I cut out to put the
windows in) plug fit to the inside of the window frame, and arranged in
some simple, non-space-hogging, quick and easy to deploy fashion (hinged
from the ceiling, with a rope and pulleys, perhaps) which raises the
insulation at the window from the R3 or so back up near R35 or so, which
the rest of the wall is at. Also makes it rather dark inside, but
intended for non-occupied or already dark out use. A collector could be
built into the face of this sort of thing.

Generically, movable window insulation. Which does not work in the long
run if it's difficult or time-consuming to use, thus my emphasis on it
needing to be a simple, easy, and reliable arrangement.

A

#### Anthony Matonak

Jan 1, 1970
0
Ecnerwal said:
A foam (or stress-skin, as I still have the holes I cut out to put the
windows in) plug fit to the inside of the window frame, and arranged in
some simple, non-space-hogging, quick and easy to deploy fashion (hinged
from the ceiling, with a rope and pulleys, perhaps) which raises the
insulation at the window from the R3 or so back up near R35 or so, which
the rest of the wall is at. Also makes it rather dark inside, but
intended for non-occupied or already dark out use. A collector could be
built into the face of this sort of thing.

Perhaps you could cut small holes into your movable window insulation
plugs. These could allow a limited amount of light through the assembly
when they are covering the window without sacrificing too much of their
insulating value. I've found that a little light is vastly preferable
to no light at all. Place these holes at eye level, make them about a
foot across and they can double for providing views. Cover them on one
or both sides with a little polycarbonate or plastic film and the holes
won't have so much of a draft.

Anthony

K

#### Kiwi John

Jan 1, 1970
0
have a look at www.theoutbackshed.com.au look at the fisher and pykel
washing machine motor its a permanant magnet motor rewire it ie cut the
coils and resolder them and if you have a creek on the property change it
to a hydro unit

its easy to build and if you make it simple using its own bearings you
can just put a box section over them weld a pipe onto it and your off and
running takes less than a day to build if you can put a couple up all the
better

i just used a hub out of a water evap air cooler and screwed a section of
puts out up to 40v at around 20 amp

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