Posted 25 March 2009 - 02:04 AM
Maybe I'm pushing expectations for my little GEK unit but these are the end uses I have in mind:
I want to run the homestead we are just beginning to build. Eventually I'd like to power with electricity a tractor, truck, car, run maybe two houses, barn, and workshop with the normal array of power tools, freezers, fridges, lights, computers, and cell phone chargers. (I don't think I'll ever be able to run a chain saw on either batteries or wood gas though.)
I'm thinking a 7-10 kw genset and a big battery bank will do it. Seven kw run four hours a day produces 28 kwh (say 30); times 300 days a year makes 9,000 kwh per year. I suspect your average Macmansion consumes more but I can skip the pool heater.
Continuing a discussion I started with Steve on another thread, say it costs two kilograms of wood to produce one kwhe (twice what Steven began his estimate with). That's 4.4 pounds of wood times 9,000 equals not quite 40,000 pounds of wood a year which is 20 tons which is about ten cords of wood. (wet wood would weigh more, some species weigh more than others per unit volume, but roughly speaking.) It has cost me about seven cords to heat my house this year so far (inefficient old wood furnace in a drafty 100 year old house).
I figure the whole business could be done for considerably less than the cost of a PV solar set up a quarter the size.
We own a 300 acre hard and soft wood forest. Ten cords removed from a tenth of that for purely sound management purposes wouldn't touch the principle and it could be done, should be done, essentially forever.
Am I a dreamer or what?
Posted 25 March 2009 - 03:11 AM
I don't see a practical route to running your tractor, truck and car electrically. All your other ideas seem eminently doable.
9000 kWh/year is 750kWh/month, which is an easily achievable low-consumption household (have a look at your present electric bills to see how much you are using now). This is probably a very good working estimate.
You are looking at 1200-1500 hours per year of operation for your gasifier and your engine. After the novelty wears off, you'll probably want something you can fuel up, start, and walk away from (it ought to tend to itself, and gracefully shut down when it runs out of fuel).
Cross-checking your fuel consumption: You really ought to be able to achieve 75% cold gas efficiency, and 20% engine+generator efficiency, which gives an overall wood-to-kWhe efficiency of 15%. This is 2.67lb or 1.2 kg of 0%mc wood per kWhe. Your 9000kWhe should consume about 24,000 lbs of 0%mc wood, or 48,000 lbs of 50% mc wet wood (which is ~ 10 cords).
One thing you don't mention is combining your heating requirements with your power requirements. Like me, you have a good 100 days per year in which you have a substantial need for heat (which you presently get by burning 7 cords of wood per year). One thing you could do with your gasifier is that you can capture some of the 80% heat loss that the engine produces and use that to heat your house. You would have to examine the cost of this "free" heat (it's not actually free, since you have to build and operate equipment to capture it), versus just burning more wood in a furnace. If your wood is cheap enough, the "less efficient" option may well end up being more cost effective.
Not to throw a wet blanket on things, but while what you are talking about is possible technically, it might not be justifiable economically. That's not to say that you shouldn't do it, just that you might need other reasons to justify the project (e.g. independence, interest, etc). Two things that are working against you economically:
- commercial power and energy rates aren't terribly high today. They seem high when you are paying the bill, but 9000kWh of electricity is only worth (ballpark) $1000, which doesn't seem like a lot of money to use to fund your own utility operation.
- small scale installations have powerful leverage working against you. For example, if you need to change your oil every 100 hours at a cost of $25, that is 3.5c/kWh just for oil changes - ugh!
Posted 25 March 2009 - 03:58 AM
I agree with Daniel all of your ideas are feasible except the electrified vehicles. I broke my heart out on that for 16 years in the 70's and 80's. Still a huge matter of battery energy/density/cost. But hey, you could as others have, and are now doing, power those all by wood gas. The GEK you now have (that you think is too small) after it has trained you would work fine on the car or tractor. Jim M. has a larger gasifier he hints to release for larger applications.
Such as the 20 hp engine you will need to spin a 10kw gen head.
And two of my five chain saws ARE electric: an AC continuos duty commercial Stilh and an intermittent duty 12 vdc camping saw from my auto electric days. I will if needed be using the woodgas to supply the electricity to power these and be upgrading the DC motor to an air cooled 24 or 36 volt. The AC Stilh WILL work as is on a 120 volt DC battery bank. I currently process 30 cord of firewood for 5 houses a year now. My warmer,faster growing Douglas Firs on my 20 acres would max out at 50 cords a year.
That was the main point on the other thread I was trying to make to Lee; "Are you willing to source and able to handle this much weight and volume?"
Chuck, you know, you are. 'Nuff said.
Posted 25 March 2009 - 03:33 PM
I still have my hopes for electric vehicles. Not too excited about dragging around a tin can full of smoking wood as well as a regular engine. There's a guy around here who does run an electric tractor, a much modified old Gravely. He'll talk about it down at the farmer's market where he is a major veggie seller. The main problem, of course, is batteries. Electric motors are great for traction. Maybe the new batch of lithium ion batteries will make a difference. Maybe I'd need another GEK sized unit to charge batteries.
I have an electric chain saw too, a little one I use for carpentry sometimes. Somehow I can't see dragging a long extension cord into the woods. I've got a couple of Stihs for that.
You are certainly right. Grid power would be a lot cheaper. The problem is that the grid connection is nearly a mile from my homestead site. I wouldn't be surprised if it cost me something like $50,000 to make a grid hook up. I'm going to get the exact number this summer. Costs $250 just to have them do a survey and give you a price. I might still go for that if I could work out some kind of net metering deal with the power company. I could supply a little juice on peak and use more off peak and get paid for it. That kind of thing would help with the battery-storage problem
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