# Solar & charcoal off-grid setup

I’d like to ask some of you practicing experts on what size system I need for complete grid-freedom. I have a smart meter and my power is provided by a rural power cooperative. They provide an online tool for me to look at my usage statistics by the hour, day or month. According to their tool, during the hottest days of last summer, (100+ for many consecutive days), my average hourly usage was in the 2-3 KWH range, with a daily low below 1 KWH and a high rarely above 6KWH. Even though I have a degree in electrical engineering, I’ve never worked in the industry, so my knowledge is limited to the theoretical textbook variety.

The bottom line is, what size system should I plan for? Mine will be a hybrid system combining solar (both photovoltaic and thermal) as well as, likely, charcoal-driven self-generation, using a Kohler twin cylinder 18HP engine. I have no interest or desire to grid-tie.

Alex for your question specifics the direct answer is how much base fuel wood can you actually ongoing source, and be willing to charcoal convert on a continual ongoing basis.
This has been much discussed in detail in topics in both the Small Engine Users forum section and Charcoal Users forum section here on the DOW.

THIS fuel wood supply problem is the base starting point ONLY you can answer.

All other system stuff is just details of getting from point A to B.

Shortcut to real world doing this calculation is to rent a generator set with a Kohler V-twin gas engine. Fuel this for a few days waking hours to bedding down as the sole AC power used source.
Right away the low base loads of 2kW/hr will bump you against versus 6 kW/hr peaks. Size as a BIG fuel consumption hog for peaks? Or smaller, fuel sipper? Then how to load demand share out meals cooking, cloths washing, kids washing ALL often grid spoiled done unthinking at the same time??
Turns into immediately a low \$'s buy-in, high sweating Humans management problem. Or; a very high \$'s and sweating/design investment PROJECT, to be a low human interaction project.
Gen-set dino fueling you can determined this before you would have to energy power supply BALANCE decided.

Look in Mr Wayne’s pictures that the family is helping him to wood fuel make for daily woodgas fuel using driving.
Those who do not have this co-operative all family support drive a lot less.
SAME with home wood fuel based power generation.
Why I still grid feed for the houses and others here.
Out building; barely woodgas for just for myself. I am honest enough to say just ain’t enough woodchopping SteveU to go around for all of my wood fueling desires.
Again honestly except for a very few here willing to scale back down their daily power needs to bachelor/old-maid levels every woodgas home power system here that I’ve seen here the engine gets sooner or later propane fueled. The woodgas novelty wears off.

So back to the beginning. How much fuel wood can you reliably source to charcoal make up; or gasifier size and dry down into useable.
You have to determine this and design your power use and supplying around this.
Full engine fueling for your electric power here that’d be 30,000 to 60,000 pounds of wood you’d need. That’s a bunch. Especially IF you have only part year to solar dry it; and then protected store it for a whole years annual use out.
Grim supply maths here. No formal engineering training needed when actual using DIY.

Regards
Steve Unruh

Apologies. Edited down as I see was a specified charcoal fueling power goal with this topic’s transfer. S.U.

Hello Alex in Waco, TX. Are you planning to go off-grid near Waco? Your monthly KWH usage from previous co-op bills would help you the most, especially if you live in the same house, and live approximately the same life style. Unless you want a large PV array, solar hot water heating will save lots of money. Your outdoor kitchen will cut electrical and gas usage. (We do almost all cooking in an outdoor kitchen using TLUD stoves that just happens to create lots of premium char. We also have a solar oven.) Switch to LED lighting, or keep using CFL´s. Can you supplement the PV and Thermal with Wind? Once you implement all methods of energy conservation, you will arrive at a minimum, and then you can calculate the size of system for off-grid. Last month, I purchased \$12 worth of electricity, which included charging my electric car. I live about 100 miles South of Waco.

Ha! Ha! Yep you are correct RayM.
Things indeed different in Texas versus my temperate rainforest.
Makes me shiver cold reading all of that heat you guys having to shed off get rid of.
Had to have heating fires the last three nights with coolish raining. STILL waiting for wood drying weather.
Very nice portable power supply bank on wheels you have in your Leaf car.
Smart.
Real Smart.
I hope more look at these available portable power supply banks now available in a different light. You are setting quite the example.
No more 1700 to 3000 pounds of lead acid battery banks needed anymore.
Best Regards
Steve Unruh

Some easy ways to figure this are to take your monthly usage in kilowatt hours divided by the days in the month, then you need to set up a solar system that can provide this amount of kilowatt hours per day, their are tables online that you can use to calculate this. Here in western North Carolina where I live we get 4.3 hours of solar producing sun per day, and we have about 220 days of sun per year. So the way that we have figured it is you size a solar system a little above your daily usage figuring on the hours of solar producing sun that you get, and then use a generator for the days that you do not have sun. The battery backup we sized for three days worth of power usage with no input power when fully charged. At my father’s place this equated to a battery pack of about 7000 pounds of lead acid batteries, it’s a 24 V battery system and if he was going to do it again he would do with the 48 V system. So basically the system looks like about 4K worth of solar, 2 outback solar chargers , 2 outback solar inverters, a Kabota 15 K generator and about 7000 pounds lead acid battery pack. Or basically to two of the large forklift battery packs.

I love the idea of using a electric powered car battery pack,I have never calculated the amount of amp hours they produce but it’s got to be very high.

Also if you have wind or water these are great supplements to generator.

But the main thing before you start the system is get your usage as low as possible, do something different for your hot water, for your cooking, change all your lights, get a much more efficient heating and cooling system and then start from there.

Also grid tie is about 1/5 the price you just do solar and then use a Sonny boy inverter and you come up with a net low payment per month.

My father’s daily usage is about 14 KWh per day

So the biggest point to the whole game is get your usage as low as possible.

Hi Alex,welcome. Look long and hard at solar water heating as a source for energy. I live in WV not very solar friendly,but years ago I built a solar water heater from an old refridge. worked very well for several yrs. I would think in texas you could do a lot more with solar heat. You also have to look at your initial investment how many yrs till pay back. just some thoughts . Al

Hi Alex, we went the off grid route ourselves and that is what originally sparked my charcoal awakening. 6 1/2years later with 2 kids and a small business I finally caved and installed a grid connection. Our house is now an odd hybrid with critical circuits running on solar on a backup generator sub panel and the rest on utility power. Off grid is fully possible but it takes work or crazy money to live the life that most of us take as a given. You are starting with a huge advantage with your location due to large amounts of sunny days and less of a seasonal difference in daylight hours. So here are my generic pointers and a few things you could try as a way of getting the most of your investment.
Negawatts: a watt you don’t have to generate is the cheapest watt of your system. This can include led lights, programmable thermostats, extra insulation, triple pane windows;in short everything the conventional world tells you to do to save energy.
Peaks and valleys: What people don’t tell you about off grid living is how you have to become different than the average household to succeed at it. Anyone can work it with endless batteries and panels but it takes a smart human to make it work on a reasonable budget. My advice is you start thinking about everything as a flood or a drought and you adjust accordingly. Your batteries are always your primary reservoir they come first for charge, that is a given, but the sizing of the bank is a factor of budget so there are other ways to “store” your power in times of plenty. Here we stored surplus power as laundry, electric chainsaw usage, power tool usage, dishwasher, greenhouse irrigation. At 1 pm on a sunny day my bank topped out and it would otherwise go to waste so we used it straight from the panels for greatest efficiency; don’t burn it off as heat on a charge controller as is the norm.
Buy the best battery bank you can afford
buy as much panels as your space can handle and then some; Panels are cheap now and there is always another energy sink to dump the excess into. for your situation of excessive heat I would probably rely on a programmable thermostat set for the coldest air conditioning to match my highest production that would suck up all the excess generation. Your house will be too cold for those few hours but then your ac coasts in the evening as your production fades; heat, or cold in your case, as a battery replacement. If it got too cold during that time I would say invest is some thermal mass to slow down the cooling/warming cycle; ceramics with concrete board underlay, double layered drywall, tanked water etc.
Finally unless you have a love of machinery if a grid connection is available… put it in. Even if it goes to a shed at the edge of the property and is used only in times of emergency whatever the cost it will be cheaper then the cheapest backup generator and will give you peace of mind. That was a painful lesson; using a backup generator by choice is fun and exciting, as your only option; expensive, nerve racking, frustrating.
Be smart, have fun,
best regards, David Baillie

before converting to solar PV, i did two things to reduce our 17 KW per day down to about 10 KW:

i replaced the conventional flush toilet with a SunMar compost chamber with the RV 1 pint flush toilets. this is a route i don’t recommend in hindsight, but the dramatic reduction in pumping water uphill was a big factor in the decision. too many learning curve surprises involved, and still some issues not entirely worked out. at least we’ll never have to replace the leach field…

the other thing i did was replace the conventional refrig/freezer with a Sunfrost 16 cu ft. model which uses 80% less energy than the conventional. was very fortunate to have a friend notice one in a local used swap/ for sale magazine and i picked one up for 10% of the original price. have been very pleased with the operation of it.
i have 48 golf cart batteries on a 48 volt system, with an inverter that converts that to 240 AC. i no longer use distilled water to top off the batteries, but use 3% hydrogen peroxide instead based on some information i came by (a .pdf file of a lab experiment done with 50% hydrogen peroxide on lead acid batteries, and when the experiment was over, they cracked open a few batteries and they looked brand new.).

i am in maine, and i paid \$4 a watt for the panels. 5 years ago. just passed up a chance on a group buy for some at \$0.34 a watt… we have a 2.6 kw/hour system and have another 1 kw of panels yet to tie up to it. our cooking stoves and hot water currently is from propane but hope to convert the hot water over to solar and co-generation from the wood gasifier. eventually, will run the stoves off wood or methane from manure.

i still use about 20% of our year round electricity from the grid. hoping at some point that wood or charcoal gas in our generator will make up the difference.