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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go. More efficient and it burns cleaner than a wood stove, so I doubt there would be any risk of them being banned.
Was thinking that too, but that seems more complex as well, ex: still requires a special type of combustion engine and so on, but it may very well make the most sense in a residential setting.
But either way it would not require a big tower or anything of that sort so the equipement could be tucked away somewhere out of sight. The generator could probably be put indoors if exhaust is vented properly. Idealy if I setup a wood stove I'd want an outside intake too. Make it a closed system. Would only need to run in winter as in the 2-3 summer months we have, solar would probably be enough to produce power due to longer days. I'm thinking since either way I need a battery bank, inverters etc, I'd probably be best to look at solar first and see how that fairs out. Then add a second energy source for winter.
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#51 Reply
Posted by
uncle_bob
on 06 Aug, 2016 16:24
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go. More efficient and it burns cleaner than a wood stove, so I doubt there would be any risk of them being banned.
Was thinking that too, but that seems more complex as well, ex: still requires a special type of combustion engine and so on, but it may very well make the most sense in a residential setting.
But either way it would not require a big tower or anything of that sort so the equipement could be tucked away somewhere out of sight. The generator could probably be put indoors if exhaust is vented properly. Idealy if I setup a wood stove I'd want an outside intake too. Make it a closed system. Would only need to run in winter as in the 2-3 summer months we have, solar would probably be enough to produce power due to longer days. I'm thinking since either way I need a battery bank, inverters etc, I'd probably be best to look at solar first and see how that fairs out. Then add a second energy source for winter.
Hi
As soon as you have system big enough to do you some good, you are right back to licensing and inspections. Boiler explosions were once a very big deal. Centuries later we all still live with the regulation process that they brought on.
Bob
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#52 Reply
Posted by
mtdoc
on 06 Aug, 2016 17:43
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go. More efficient and it burns cleaner than a wood stove, so I doubt there would be any risk of them being banned.
Was thinking that too, but that seems more complex as well, ex: still requires a special type of combustion engine and so on, but it may very well make the most sense in a residential setting.
But either way it would not require a big tower or anything of that sort so the equipement could be tucked away somewhere out of sight. The generator could probably be put indoors if exhaust is vented properly. Idealy if I setup a wood stove I'd want an outside intake too. Make it a closed system. Would only need to run in winter as in the 2-3 summer months we have, solar would probably be enough to produce power due to longer days. I'm thinking since either way I need a battery bank, inverters etc, I'd probably be best to look at solar first and see how that fairs out. Then add a second energy source for winter.
Hi
As soon as you have system big enough to do you some good, you are right back to licensing and inspections. Boiler explosions were once a very big deal. Centuries later we all still live with the regulation process that they brought on.
Bob
No boiler with a wood gasifier. The generator head is driven by a standard IC engine. The wood gasification process provides the fuel and does not involve a boiler of any high pressure chamber.
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#53 Reply
Posted by
uncle_bob
on 06 Aug, 2016 22:54
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go. More efficient and it burns cleaner than a wood stove, so I doubt there would be any risk of them being banned.
Was thinking that too, but that seems more complex as well, ex: still requires a special type of combustion engine and so on, but it may very well make the most sense in a residential setting.
But either way it would not require a big tower or anything of that sort so the equipement could be tucked away somewhere out of sight. The generator could probably be put indoors if exhaust is vented properly. Idealy if I setup a wood stove I'd want an outside intake too. Make it a closed system. Would only need to run in winter as in the 2-3 summer months we have, solar would probably be enough to produce power due to longer days. I'm thinking since either way I need a battery bank, inverters etc, I'd probably be best to look at solar first and see how that fairs out. Then add a second energy source for winter.
Hi
As soon as you have system big enough to do you some good, you are right back to licensing and inspections. Boiler explosions were once a very big deal. Centuries later we all still live with the regulation process that they brought on.
Bob
No boiler with a wood gasifier. The generator head is driven by a standard IC engine. The wood gasification process provides the fuel and does not involve a boiler of any high pressure chamber.
Hi
Go down to city hall and see the book they open up for the regulations on your permit. It all started with boilers. If it's got enough power to take you off the grid (we already went over that part of it), you have a pretty big machine.
Bob
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#54 Reply
Posted by
mtdoc
on 07 Aug, 2016 00:42
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go. More efficient and it burns cleaner than a wood stove, so I doubt there would be any risk of them being banned.
Was thinking that too, but that seems more complex as well, ex: still requires a special type of combustion engine and so on, but it may very well make the most sense in a residential setting.
But either way it would not require a big tower or anything of that sort so the equipement could be tucked away somewhere out of sight. The generator could probably be put indoors if exhaust is vented properly. Idealy if I setup a wood stove I'd want an outside intake too. Make it a closed system. Would only need to run in winter as in the 2-3 summer months we have, solar would probably be enough to produce power due to longer days. I'm thinking since either way I need a battery bank, inverters etc, I'd probably be best to look at solar first and see how that fairs out. Then add a second energy source for winter.
Hi
As soon as you have system big enough to do you some good, you are right back to licensing and inspections. Boiler explosions were once a very big deal. Centuries later we all still live with the regulation process that they brought on.
Bob
No boiler with a wood gasifier. The generator head is driven by a standard IC engine. The wood gasification process provides the fuel and does not involve a boiler of any high pressure chamber.
Hi
Go down to city hall and see the book they open up for the regulations on your permit. It all started with boilers. If it's got enough power to take you off the grid (we already went over that part of it), you have a pretty big machine.
Bob
I'm not sure what you are trying to say here. A generator fueled by a wood gasifier does not require a permit here. Neither do wood stoves.
How much power generation one needs to be off grid depends entirely on ones loads. For our modern 3000 sq. ft. Home, I can be totally off grid with a 2000 watt genset as long as I use only the wood stove for heat. I know people who live off grid full time in smaller energy efficient homes with only a small solar array and a 1000 watt generator providing their electricity.
The wood gasifier fueled generators i linked to earlier are big 15k -18k watt beasts that could fully run our home including our heat punp yet even that would not require a permit.
The transfer switch for generator input i installed several years ago did require an electrical permit but as far as the AHJ goes, it makes no difference what fuels the generator I plug into it - gas, diesel, propane or wood.
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Wood stoves DO require a permit in many parts of the US. Just like gas and electric heating systems. Part of the public and private safety requirements. During a permited wood stove installation things are verified like adequate separation from flammable materials, proper height of the smokestack above the roof, existence of a spark arrestor on the smokestack, safe construction and condition of the stove and so on. In addition, many areas of the US regulate operation of wood stoves to maintain air quality. They may be required to have certified low emissions, and may not be allowed to operate on days when weather conditions don't allow smoke dissipation.
Of course if you buy your stove and install it yourself so no one knows you have the stove you won't need a permit (until you sell the property).
There may or may not be requirements for permitting a wood gasifier. If not it would be because they are unusual enough that the regulations haven't caught up with them. Even then they would probably be covered under general provisions of local building codes and air quality regulation.
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#56 Reply
Posted by
mtdoc
on 07 Aug, 2016 02:17
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Yes, it's true about wood stove permits in some locations. In fact, i believe they are outright banned in some urban areas.
I also think it's true that the lack of any permits needed for wood gasifiers ( that i am aware of) is likely because they are very rare. I suspect that if they became more widespread they would require EPA certification as do modern wood stoves.
It's interesting about wood gasifiers. AFAIK they are not even regulated by CARB in California.
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#57 Reply
Posted by
tautech
on 07 Aug, 2016 02:30
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I remember 35+ years ago one of the locals had a gassification unit on the deck of his old Ford flat head V8 truck. He laughed at us all for buying gas and through the 70's fuel crisis and our car less days he just kept on trucking. Cold start times was his biggest curse IIRC ~30 minutes.
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#58 Reply
Posted by
uncle_bob
on 07 Aug, 2016 02:49
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What seems like the most realistic thing would be a wood stove powered steam turbine
Hi
If you go back a ways in this thread, the power need to take things off grid is in the >10KW range in this case....
Bob
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go. More efficient and it burns cleaner than a wood stove, so I doubt there would be any risk of them being banned.
Was thinking that too, but that seems more complex as well, ex: still requires a special type of combustion engine and so on, but it may very well make the most sense in a residential setting.
But either way it would not require a big tower or anything of that sort so the equipement could be tucked away somewhere out of sight. The generator could probably be put indoors if exhaust is vented properly. Idealy if I setup a wood stove I'd want an outside intake too. Make it a closed system. Would only need to run in winter as in the 2-3 summer months we have, solar would probably be enough to produce power due to longer days. I'm thinking since either way I need a battery bank, inverters etc, I'd probably be best to look at solar first and see how that fairs out. Then add a second energy source for winter.
Hi
As soon as you have system big enough to do you some good, you are right back to licensing and inspections. Boiler explosions were once a very big deal. Centuries later we all still live with the regulation process that they brought on.
Bob
No boiler with a wood gasifier. The generator head is driven by a standard IC engine. The wood gasification process provides the fuel and does not involve a boiler of any high pressure chamber.
Hi
Go down to city hall and see the book they open up for the regulations on your permit. It all started with boilers. If it's got enough power to take you off the grid (we already went over that part of it), you have a pretty big machine.
Bob
I'm not sure what you are trying to say here. A generator fueled by a wood gasifier does not require a permit here. Neither do wood stoves.
How much power generation one needs to be off grid depends entirely on ones loads. For our modern 3000 sq. ft. Home, I can be totally off grid with a 2000 watt genset as long as I use only the wood stove for heat. I know people who live off grid full time in smaller energy efficient homes with only a small solar array and a 1000 watt generator providing their electricity.
The wood gasifier fueled generators i linked to earlier are big 15k -18k watt beasts that could fully run our home including our heat punp yet even that would not require a permit.
The transfer switch for generator input i installed several years ago did require an electrical permit but as far as the AHJ goes, it makes no difference what fuels the generator I plug into it - gas, diesel, propane or wood.
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That's part of the issue too, government does not like people who go off grid, so they will do everything they can to give you trouble about it.
I doubt I could truly go off grid at this current house, but I'm thinking my best bet is to start with wood stove and solar, and try to be off grid for say, the 3 summer months, when we get 16+ hours of sun per day, and use wood stove as supplementary heat. If that works out, I could possibly suspend my hydro service and save the ~100/mo delivery fee... though knowing how crooked they are, you probably can't do that, or there is probably some huge fee to suspend. So possibly would not be worth it. Almost have to fully cancel it.
But could then look into the gassifier too, just need to find somewhere that sells those, not even sure how much they cost, can't seem to find them anywhere other than DIY guides, but this is something I'd probably want to get from a proper company with warranty/support etc.
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#60 Reply
Posted by
uncle_bob
on 07 Aug, 2016 18:06
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That's part of the issue too, government does not like people who go off grid, so they will do everything they can to give you trouble about it.
I doubt I could truly go off grid at this current house, but I'm thinking my best bet is to start with wood stove and solar, and try to be off grid for say, the 3 summer months, when we get 16+ hours of sun per day, and use wood stove as supplementary heat. If that works out, I could possibly suspend my hydro service and save the ~100/mo delivery fee... though knowing how crooked they are, you probably can't do that, or there is probably some huge fee to suspend. So possibly would not be worth it. Almost have to fully cancel it.
But could then look into the gassifier too, just need to find somewhere that sells those, not even sure how much they cost, can't seem to find them anywhere other than DIY guides, but this is something I'd probably want to get from a proper company with warranty/support etc.
Hi
I believe we hashed out the fact that as long as you are still connected to the grid, the "connection fee" eats you alive. Your variable rate isn't all that bad, it's the "tax" that comes along with it that is the issue.
Bob
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Yeah that's why to really save you need to be able to go fully off grid. One thing I have been pondering on though that WOULD work, is a natural gas generator. Cancel hydro, keep gas. At least you're only paying one delivery fee, not two. Have the genset fire up whenever the voltage hits a certain threshold, for example. Need to them monitor how much current is being drawn to charge the batteries, and when it hits a certain value (trickle charge) it could turn off.
The gassifier idea sounds interesting though, the more I think about it. I'll be paying $3,240/year in hydro, and gas is about $1,680, so $4,920 total per year for both utilities. So say I want something that will pay for itself in 10 years, I can afford to buy 50k worth of equipment (solar, gassifier etc) but that's kind an unrealistic amount of money to pay in one shot, so idealy I'd want something in the 20k range, that would pay for itself in 5ish years. Either way I seriously need to start saving up. At some point the rates will be higher than what I can afford to pay. I need to come up with something before that point happens.
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#62 Reply
Posted by
uncle_bob
on 07 Aug, 2016 19:48
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Yeah that's why to really save you need to be able to go fully off grid. One thing I have been pondering on though that WOULD work, is a natural gas generator. Cancel hydro, keep gas. At least you're only paying one delivery fee, not two. Have the genset fire up whenever the voltage hits a certain threshold, for example. Need to them monitor how much current is being drawn to charge the batteries, and when it hits a certain value (trickle charge) it could turn off.
The gassifier idea sounds interesting though, the more I think about it. I'll be paying $3,240/year in hydro, and gas is about $1,680, so $4,920 total per year for both utilities. So say I want something that will pay for itself in 10 years, I can afford to buy 50k worth of equipment (solar, gassifier etc) but that's kind an unrealistic amount of money to pay in one shot, so idealy I'd want something in the 20k range, that would pay for itself in 5ish years. Either way I seriously need to start saving up. At some point the rates will be higher than what I can afford to pay. I need to come up with something before that point happens.
Hi
Unless the equipment its self pays off in under 5 years, you have no real chance of getting ahead. None of this stuff runs forever without maintenance / replacement. There are also secondary costs that you don't figure in right up front. You have fuel cost, even for wood (we're talking a *lot* of wood). There's a "load / unload" process with wood that can get a bit tedious when the wood pile is under a few feet of snow
I have empirical data on that one....
Bob
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Yeah natural gas generator would be the "guaranteed" way out but the problem as you say is Wynne. In fact she wants to BAN natural gas by 2030. She is completely insane. Maybe slash the hydro prices to 1/10th of what they are, then let's talk about heating with hydro.
I think I will probably have to eventually accept that I will have to move out of province or on a much larger lot with more options at some point but it's nice to dream.
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#64 Reply
Posted by
LabSpokane
on 10 Aug, 2016 02:16
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go.
Sorry, but no. They will work for a very little while and then the engine will plug up with tar.
From what I've heard, every genset the company you linked sold has failed in the field with no resolution forthcoming (edit: I see new updates and claims of a "new version" but nothing I saw in the video is really convincing that the core problem has been solved.) I've seen the unit you linked at PowerGen and I just don't see how it could work on a long term basis. These generators are expensive curiosities and little more.
And, yes, I watched the videos. Tar cracking? Show me a calibrated thermocouple and a residence time, because I don't believe it. If that thing was cracking tar, the piping would glow cherry red like a set of headers on a dragster.
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#65 Reply
Posted by
mtdoc
on 10 Aug, 2016 05:38
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go.
Sorry, but no. They will work for a very little while and then the engine will plug up with tar.
From what I've heard, every genset the company you linked sold has failed in the field with no resolution forthcoming (edit: I see new updates and claims of a "new version" but nothing I saw in the video is really convincing that the core problem has been solved.) I've seen the unit you linked at PowerGen and I just don't see how it could work on a long term basis. These generators are expensive curiosities and little more.
And, yes, I watched the videos. Tar cracking? Show me a calibrated thermocouple and a residence time, because I don't believe it. If that thing was cracking tar, the piping would glow cherry red like a set of headers on a dragster.
I can't vouch for that company. Just something that came up in a search. But - wood gasification is not a new technology - it's been around for at least 70 years and is tried and true. It has its limitations but it does work. I do know one person who successfully built one which he uses to fuel his off-grid genset. My main point was that from what I've learned from others - it's a better solution for wood fired electricity production on a small scale than a boiler/steam turbine. I have no personal experience with them. If I wanted to be completely off grid - I'd supplement my PV generation with microhydro from the stream on my property.
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#66 Reply
Posted by
LabSpokane
on 10 Aug, 2016 06:20
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go.
Sorry, but no. They will work for a very little while and then the engine will plug up with tar.
From what I've heard, every genset the company you linked sold has failed in the field with no resolution forthcoming (edit: I see new updates and claims of a "new version" but nothing I saw in the video is really convincing that the core problem has been solved.) I've seen the unit you linked at PowerGen and I just don't see how it could work on a long term basis. These generators are expensive curiosities and little more.
And, yes, I watched the videos. Tar cracking? Show me a calibrated thermocouple and a residence time, because I don't believe it. If that thing was cracking tar, the piping would glow cherry red like a set of headers on a dragster.
I can't vouch for that company. Just something that came up in a search. But - wood gasification is not a new technology - it's been around for at least 70 years and is tried and true. It has its limitations but it does work. I do know one person who successfully built one which he uses to fuel his off-grid genset. My main point was that from what I've learned from others - it's a better solution for wood fired electricity production on a small scale than a boiler/steam turbine. I have no personal experience with them. If I wanted to be completely off grid - I'd supplement my PV generation with microhydro from the stream on my property.
FWIW, I do this for a living and we know the only people that have made gasifier gensets which come close to "working" commercially. They will not be building more. They only get about 50% uptime and are looking at conventional boiler technology for the future.
PV and hydro are solid choices. Leave the gasification stuff to folks who build utility-scale power plants.
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What seems like the most realistic thing would be a wood stove powered steam turbine
Nah. If you want wood-powered electricity production, a wood gasification powered generator is the way to go.
Sorry, but no. They will work for a very little while and then the engine will plug up with tar.
From what I've heard, every genset the company you linked sold has failed in the field with no resolution forthcoming (edit: I see new updates and claims of a "new version" but nothing I saw in the video is really convincing that the core problem has been solved.) I've seen the unit you linked at PowerGen and I just don't see how it could work on a long term basis. These generators are expensive curiosities and little more.
And, yes, I watched the videos. Tar cracking? Show me a calibrated thermocouple and a residence time, because I don't believe it. If that thing was cracking tar, the piping would glow cherry red like a set of headers on a dragster.
I think you need something to filter out the tar first, and I imagine that would require lot of maintenance too. Definitely an interesting concept, but I personally like steam idea, because it's simpler. You could still use gasification but just for extra heat within the stove to get more out of the wood. Simple is good, when wanting to go off grid. I'm even wondering how well tesla turbines would fair out. They arn't the most efficient, but could you like daisy chain a whole bunch together? They would be easier to build than a steam turbine too.
Another option might be sterling engine, but that's not exactly simple to build either. Of course this would be combined with solar, as you'd still get SOME output in winter, and in summer when you don't want to use the wood stove, you'd get a lot of output. You'd be running off batteries all the time, the wood stove and solar would simply be keeping them topped up.
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#68 Reply
Posted by
langwadt
on 11 Aug, 2016 23:55
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wind turbines are noisy and ugly and when ever it is in the path of the sun you have a strobe light.
and small turbine are not nearly as cost efficient as the big ones, so for anyone wanting wind power the smart thing to do is buy a part of one of the big ones
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#69 Reply
Posted by
mtdoc
on 12 Aug, 2016 00:14
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Another option might be sterling engine, but that's not exactly simple to build either. Of course this would be combined with solar, as you'd still get SOME output in winter, and in summer when you don't want to use the wood stove, you'd get a lot of output. You'd be running off batteries all the time, the wood stove and solar would simply be keeping them topped up.
The reality is that almost all of the many people who live off grid, the best solution is solar PV combined with a traditional generator burning either gasoline, diesel or propane.
Microhydro or wind power is great if you have the appropriate resource available at your location- but very few do.
Wood burning for heat (space or water) is common and useful.
Wood burning to produce electricity - whether by steam turbine or wood gas fueled generator is really only something to consider if one is looking at being fully independent of the fossil fuel industry (for either philosophical reasons or SHTF apocalypse prepping). Both have their shortcomings but both are being employed by small scale DIY'ers. I have yet to hear of either a sterling engine or thermoelectric generator being used in that scenario for anything other than very small amounts of power generation.
LabSpokane's points about the pitfall of wood gas are well taken but his experience relating to commercial power generation does not necessarily transfer to the small scale DIY off gridder who is willing to do the regular maintenance needed to burn wood gas.
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The idea is indeed to perhaps be independent of fossil fuel, for cost and renewable reasons. That and you are producing the heat either way, so may as well try to find a way to harvest it for electricity. PV would only work well enough in the summer months, when the wood stove is not needed for heat. Though I suppose the most realistic off grid way would be a propane generator that kicks on when battery voltage is too low. PV would still produce SOME power in winter, just not for very long due to the short days. Could maybe generate enough power with the wood stove using peltiers to charge a small battery that is used to power any pump/fans that are used by the wood stove to distribute the heat around the house though.
Also I never really understood the noisy part of wind turbines, they are noisy in what way? Any one that I've seen don't really put off any kind of noticeable noise. The wind in your ears is louder than the noise they may put off. I guess a DIY one would maybe be more noisy though due to not being as well engineered as a commercialy made one.
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Large scale commercial wind turbines generate their noise below human hearing range, down in the fractional Hz range. Some feel that this noise affect some animals negatively, but I have no solid information on that. There is no meaningful sound for human listeners, except possibly things like transformer hum and other similar sounds from very near the base of the tower.
Many home scale wind turbines operate at far higher frequencies and blade slap and other noises can get pretty high both in frequency and intensity. Less expertise in balance, maintenance and other similar factors can also make home wind much noisier than the large commercial installations. Add to this a neighbor or two who resent the impact on their pristine view and so are willing to complain about things that might otherwise be overlooked and you see where the problems come in.
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#72 Reply
Posted by
LabSpokane
on 12 Aug, 2016 02:28
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LabSpokane's points about the pitfall of wood gas are well taken but his experience relating to commercial power generation does not necessarily transfer to the small scale DIY off gridder who is willing to do the regular maintenance needed to burn wood gas.
As long as folks know what they're getting into with gasification, I'm OK with it. What I'm not OK with is a lot of the sunshine and daffodils that gets bandied about with it. It's capital intensive, and there will maintenance problems. Lots of expensive maintenance problems.
I'll do a rundown on the numbers sometime. I think folks will be surprised at the amount of biomass that it takes to operate one of these gensets and the net efficiency.
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It may also be a point of view problem. People who have never operating a wood stove for heat have no idea of the amount of work. Even a pelletized wood burner requires surprisingly frequent refills of the hopper, purchase and storage of large quantities of pellets, and some fairly intense and messy annual maintenance.
For those of us who cut, split and cure our own wood and operate a less automated stove the work is even greater. For someone in that situation gasification may not be as daunting.
This nation once operated nearly totally on wood power. Their are some very obvious reasons why most switched to other methods when they became available. There is a great appeal to only having to deal with utilities like heat and power once a month by writing a check, and then once every few years for repair/replacement.
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#74 Reply
Posted by
uncle_bob
on 12 Aug, 2016 03:18
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It may also be a point of view problem. People who have never operating a wood stove for heat have no idea of the amount of work. Even a pelletized wood burner requires surprisingly frequent refills of the hopper, purchase and storage of large quantities of pellets, and some fairly intense and messy annual maintenance.
For those of us who cut, split and cure our own wood and operate a less automated stove the work is even greater. For someone in that situation gasification may not be as daunting.
This nation once operated nearly totally on wood power. Their are some very obvious reasons why most switched to other methods when they became available. There is a great appeal to only having to deal with utilities like heat and power once a month by writing a check, and then once every few years for repair/replacement.
Hi
I've heated a house fully on wood not all that far south of the boarder with Canada. We did it 100% with split logs running in multiple systems. Yes, that's a *lot* of wood. It's also a commitment to never be away from home for an extended period .....If it's your trees, your chain saw, your log splitter and your labor, it all is technically "free". There is the minor issue of the cost of the chain saw, log splitter, stoves, and Tylenol. Assuming that you have a few weeks of the summer with nothing to do and an hour or two a day in the winter .... it's all free. Not really sure that the tractor and wagon for hauling the trees after they are cut figures as free on upkeep.
If you go the pellet route around here or up north where I used to be, they seem to sell them to you. That is not free and you are swapping the cost of one fuel for another fuel. Without a lot of math ... not at all clear that you come out ahead *unless* you do a full disconnect.
Bob