It's a possibility, I don't know if it will be enough for much of anything. Also I thought I'd mention there is an area of the ditch that has fast flowing water. I don't know if I could use it though since it is on county property.
Holly say moving water make heap big electric current.
Seriously, if you have moving water then that is certainly the best way to generate power.
The web is just loaded with designs for homemade water powered generator systems.
You could lash up a simple dc motor to a paddle and get power.
Maybe a sealed system with generator and propeller (the kind with fins-not the Propeller we all know and love) placed beneath the water
would keep it out of sight of anyone that might object to it?
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
Make a sort of plastic scoop that can force the moving water from a large area to a propeller in front of the water outlet at the rear.
Hook the propeller to an ac generator or dc motor to generate current. You could attach this rig to a heavy weight like a concrete block or
something to keep it under water in the proper spot. Run the wires carrying the current under water so they won't be seen. Dig a small
trench from where the wires emerge to your device you want to power and bury the wires so it's all kept secret
I'd go to a scrap yard or flea market to see if some sort of ready made scoop could be found and pressed into service instead of
fabricating one from scrap.
There are some guys wanting to put generators under water in the Hudson river to power parts of New York..I saw it
on the Science Channel.
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
The water is drained for the winter so it can't stay hidden forever that way but there is a possibility of placing it in the section under the road. I would have to wait until it drains again to do this though. Anything to do for the winter months? And also maybe add to the power supply in the summer? I know many of you don't seem to think a peltier will work well but I still think it might be something I will attempt.
I could also try using these motors for a vertical windmill. I've never tried it before but I guess everything on this project is new to me. Also, If any of you know the best way to modify them for this purpose, please tell me.
Those fluttering wind generators look easier to construct.
If you have some old hard drives they have really strong magnets in them you might be able to use for building one.
We have some we use as refrigerator magnets...so strong I hung a sack of pecans
on the side of the fridge with one.
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
From the article I read a vertical windmill could generate 50 kilowatt hours of electricity, much higher than the flutter generator. I am thinking about using your idea for smaller projects, though. Right now I'm just figuring out how to get the ac motor to generate electricity before I start anything. I'm sure I will have to buy some magnets first, though.
HollyMinkowski said...
Those fluttering wind generators look easier to construct....
I vote for the fluttering generator, too. You don't see them around town just yet, so there's probably a lot of room for experimenting and improving upon them. Why mess around with proving old technology when you can work on the latest stuff?
If you want to generate serious power, wind beats heat engines every time. The exception to this would be if you had large amounts of heat and it really was free, eg you live over a small volcano, or next to an industrial plant. If you don't have heat and you want to collect it, the sun is the most practical source. But you need to concentrate it. Here is an extract from wikipedia:
"The maximum theoretical efficiency of a heat engine (which no engine ever obtains) is equal to the temperature difference between the hot and cold ends divided by the temperature at the hot end, all expressed in absolute temperature or kelvins."
This is one of those things where you think you understand thermodynamics until you read it again and suddenly it gets really complicated. It is the "absolute temperature" which is the key. So I might be sitting here on a pleasant 20C day and I have next to me a black metal plate sitting in the sun and it is 40C. Let's turn those temperatures into kelvins, ie 293 and 313K. The formula above says the max efficiency is 313-293/313. That is 6.4%. As Scotty quite rightly says, those are the laws of physics. You have 100W heat input and you can only ever get 6.4W out. But, and this is the catch, you still need to move 100W through your heat engine. You need to cool the cool side with 100W of cooling. That is quite a big fan and heatsink.
Here is the next catch, and that is that all materials have thermal resistance. Look up some of the values for common heatsinks and they are expressed in degrees per watt. A big heatsink might have 0.5C per watt, but a smaller one might be 10C per watt. The big one costs more money. Say we used a 0.5C/W watt heatsink on our 100W heat engine above, it would drop 50C. But we only had 20C to start with! So we need a bigger heatsink. As a ball park figure, you might want to drop 5C between your heat source and your engine, 10C across the engine, and 5C for the cold side for a total of 20C. Will it work? Yes, but it ends up big. Take 1 square metre in the sun and you can collect 1kw. But to cool this 1kw with natural cooling (no fan), for only a 5C drop, you need about 20 metres of area. So you need a big cooling system, or water. But it has to be flowing water or a big store, because you can't have the water getting warm otherwise the heat engine will stop working.
So low temperature heat engines need huge heatsinks. That adds to the cost and that is why you don't see them in use.
But some things work in your favour. As you make the hot side hotter, you get more energy out. Let's make the hot side 420C - hot enough to melt solder. The cold side is 20C. The max efficiency is 400/(273+420) = 57%. Now we are talking. And we can make the heat exchangers smaller too. Let's say we drop 100C from the hot side to the engine, and the engine runs on a 200C difference and there is 100C on the cold side. Ok, our engine now only works across 200C, but a 100C drop on a heat exchanger is much less metal because heat tranfer is proportional to temperature difference.
There was the small catch of the hot side melting solder. This is the problem that limits practical heat engines - the hotter you go the more efficient they are, but the harder the materials are to work with. The turbine blades at the hot end of a steam turbine run white hot.
Oh, and the other small catch that you can't get to the theoretical carnot efficiency. You might only get half or 1/3 of that.
Above, I mentioned the 100C loss on the cold side. As an aside, real steam engines might have 100C loss on the cold side because you expand the steam down to atmospheric pressure and 100C is the temperature water boils at at atmospheric pressure. So you throw away that steam in a nice big puff of white water vapour out the top of the steam engine. It isn't the most efficient way to do things though, and if you are happy to condense the steam in a vacuum chamber lower than atmospheric pressure, you could get it down to 50C or lower. But condensers are big and heavy and expensive and that is why you see them on power stations but not on steam trains.
At the end of the day everything is a tradeoff. Higher temps = harder materials handling. Bigger heatsinks = more efficiency = higher cost. Do you concentrate your sunlight to get a higher temperature to get higher efficiency but at a higher cost due to the tracking, or go for low temperature differentials?
And there is another big catch the solar industry fail to mention - the sun doesn't shine at night. Nor much when it is cloudy. Nor much in the early morning or late evening. And it might not get much over the horizon in winter. So your 100W solar panel might only average 20W over the entire year.
Wind turbine manufacturers are also a bit guilty of giving you power figures that were measured in a gale, but overall, wind works out more economical than solar or heat engines. There are some great homebrew designs on the web, and if you have the time to build it, a 100W wind turbine plus battery plus inverter probably represents the best chance of making that elusive piece of green powered toast.
@mark--I'll try both. I plan to try the virtical windmill first, though, since I think it will be able to create more power.
@Dr. Acula--I figured solar wasn't the best way to go. I've been curious about heat for a while, though, but from what you say and the fact that all systems are very complicated, it seems wind is by far the best option. I just hope it will blow enough here.
Dr_Acula said...
Wind turbine manufacturers are also a bit guilty of giving you power figures that were measured in a gale
HaHaHa! ... I laughed out loud...thanks for that
I wonder what could be done with an old huge surplus TV dish..you know, the really big ones.
Paste reflective mylar carefully all over it and mount a medium sized solar panel at the focus point or a little in front or back of
the focus point, whatever illuminates the panel best. Have the tracking motor follow the sun...should be easy since the adjustments are
there to enable tracking of an arc across the sky....would need minor adjusting maybe 3 times/yr as the seasons change.
Might give a lot of power from a smallish panel....could provide the small amount of juice needed to turn the rotor motor
every 10-15 minutes or so to track the sun. You would need welding goggles to protect your eyes while adjusting this as it
would focus a point of light that was unbelievably bright.
If you could find a defunct old rear-projection tv you could harvest the fresnel lens from it and do much the same thing...but you
would have to actually build a rotor for it.
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
Holly, mylar on a parabolic dish sounds very practical. As does a big fresnel. Then you just need the tracking motors/gearboxes. And the tracking problem is perfect for a Propeller.
Re Sandia, that is an interesting point. Sandia labs have always built the cool stuff - as a kid I was in awe of their vertical axis wind turbines. Stirling engines were around in the 1800s, but there are so many new technologies now that didn't exist back then. eg teflon for piston seals. I'll bet Sandia can come up with something new and innovative!
Well, given running water is available from your ditch; you can get "marine style" "run-of-the-river" generators that use the water flow to generate power. By default, these drag behind a sail boat and use this to charge the on-board batteries. Used in a static install; the water flow runs the blades in the same way. When your ditch is drained, add larger propeller blades (air style) and use it as a wind genny on a small mast/tower.
I've had a few 50W (rated) solar panels mounted (ad-hoc) on my workshop roof for several years - facing in different directions (because now-a-days I'm too scared to climb onto my 40 degree+ pitched roof and unless I clear some tree tops or move them I can't get optimal power. They run a simple 25W 2m amateur transceiver on receive (mostly 99 percent of the time) via two 12VDC 100AH tractor batteries [noparse][[/noparse]in parallel] and a charge controller for about 10 months per year for 24 hours a day. If I run out of power, I just turn off the rig for a few days (or a week or two - weather depending) and I'm good to go.
Problem really is the initial cost of the panels and charge controller but hey - I own them and they still have a 12ish year (from 20) warranty left
Also, a small 5W panel connected to the tractor battery keeps it "fresh" and ready to start the tractor due to internal battery discharge caused by infrequent use is handy too!
I can measure the current draw from the receiver if you like but I'd guess its around an amp or so (it's an old converted Taxi transceiver re-programmed for Amateur frequencies).
Solar/wind/hydro if you can - it's a good mix with at least 1 or 2 of the 3 available more often than not; again, its the up-front cost that'll get you ;-/
I like HollyMinkowski's idea of the old TV dish. Issue here is the mechatronics needed to move the disk while tracking or hold it on position; you _must_ allow for wind loading and the like else 1) the dish launches or 2) you strip the gear teeth - both potentially expensive (and possibly dangerous to you and/or others).
Only you are in the best position to determine what is best; you need to gather data on your environment; wind, sun, rate and volume of water flow in order to determine which is the best first investment.
What's the easiest? Solar, Wind or Water depending on location accessibility, distances and local regulations.
What's the best? Water, Solar or Wind depending on same.
The ideas just keep getting more and more complicated, don't they? I may try to build a ditch generator, but considering how much difficulty I'm having trying to create a vertical wind turbine I'm not sure if that's going to happen.
Just to get me going, do any of you know of a website that explains how to create a vertical wind turbine? The instructions I'm currently using are very confusing.
Also--I am currently trying to keep costs down on this. I can cut scrap metal and weld different things, but I don't want to have to go out of my way to spend 50+ bucks on something with low power output. I am willing to buy different parts such as magnets though if it is necessary.
I brainstormed these once with an engineer. There are lots of designs. Wing is symmetrical in cross section and the wings are fixed (and the airodynamics of that take some thinking about as it is counter intuitive, but it is the same mechanism that allows a sailing boat to sail into the wind). You can go egg-beater style or 'H' or other variants. Officially, they are not self starting, so you need a small darrieus rotor at the top to get the blades up to a bit faster than the prevailing wind speed. (Unofficially they do self start, and one of Sandia's blew itself to bits that way). Unlike horizonal axis windmills, they will get faster and faster so you need some way of limiting the speed - eg air brakes or change the angle of the blades or tilting blades. That could be a passive mechanical system, or actively (propeller?) controlled. Then you need a stiff tower. And guy ropes at the top and those guy ropes need to clear the whole rotating part so they may need to go out at 45 degrees. So you need a bit of space. Those guy ropes also need to be very taught to keep the tower from gyrating.
The big problem (which Sandia wrestled with) is vibration in the blades. Make them thin and light and they vibrate at certain frequencies, so you can't run the turbine at certain speeds. So you need to make the tower and the wings stiff but strong. Maybe moulded fibreglass. Maybe the balsa techniques that model plane builders use. I've even pondered two wings like a bi-plane design with cross bracing with wires etc. I've also pondered a construction method using aluminium sections - trusses etc with aluminium skin over the top. Join it all with pop rivets. Very expensive but it will never corrode. But wood/fibreglass is probably more practical. One day when I get some time I'm going to build one, and if I do I think the first person I'll seek out is a mate who builds model planes.
Then there is the drive system. The bigger you make it, the slower the speed so you need to gear it up if you want to generate electricity. At least the big advantage of vertical axis is all the gearing etc is at ground level. (I talked to a guy once who services the standard multiblade farm windmills and he said that they look very romantic on a farm slowly turning, but it is something else when you are standing at the top of the tower with those sharp metal blades whizzing past).
$50 bucks? Low power output? Have you got a ballpark figure for $ to spend and for power output?
In the UK having the magic words "wind turbine" attatched to any project ensures planning permissions, and usually funding.
Physical movement of wind and water will always be best for generating power. Solar cell outputs are quoted in the middle of a desert on a sunny day and wind generators in the middle of a gale on a windy day. Battery manurfactuers do not thouble you with their diminishing returns figures and solar cell makers do not either, three years later and both would warrent replacement.
My dad made a four foot, six bladed turbine for our garden back in the sixties (when neuclear power was to be too cheap to meter)
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Style and grace : Nil point
Re Toby, you know, a 4 foot 6 bladed turbine is exactly the sort of project that is likely to work. Not too expensive. Not too big. Lots of plans for similar sized designs. More practical than a homebrew nuclear plant too.
I was going for a 3 blade design, with the possibility of using halved pvc pipe for the upright blades, but that may not be the best material. For the bottom I was going to use an old ac motor and put magnets in it. I'm sure I'll have to buy some neodymium ones or something similar off the web. I'll get you a pic of the motor on the inside later when I feel like it (when it's not so cold outside).
Comments
www.youtube.com/watch?v=L1FzkY9qzCE
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
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PG
Seriously, if you have moving water then that is certainly the best way to generate power.
The web is just loaded with designs for homemade water powered generator systems.
You could lash up a simple dc motor to a paddle and get power.
Maybe a sealed system with generator and propeller (the kind with fins-not the Propeller we all know and love) placed beneath the water
would keep it out of sight of anyone that might object to it?
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
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PG
Make a sort of plastic scoop that can force the moving water from a large area to a propeller in front of the water outlet at the rear.
Hook the propeller to an ac generator or dc motor to generate current. You could attach this rig to a heavy weight like a concrete block or
something to keep it under water in the proper spot. Run the wires carrying the current under water so they won't be seen. Dig a small
trench from where the wires emerge to your device you want to power and bury the wires so it's all kept secret
I'd go to a scrap yard or flea market to see if some sort of ready made scoop could be found and pressed into service instead of
fabricating one from scrap.
There are some guys wanting to put generators under water in the Hudson river to power parts of New York..I saw it
on the Science Channel.
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
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PG
Sorry the picture is so dark.
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PG
If you have some old hard drives they have really strong magnets in them you might be able to use for building one.
We have some we use as refrigerator magnets...so strong I hung a sack of pecans
on the side of the fridge with one.
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
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PG
I vote for the fluttering generator, too. You don't see them around town just yet, so there's probably a lot of room for experimenting and improving upon them. Why mess around with proving old technology when you can work on the latest stuff?
"The maximum theoretical efficiency of a heat engine (which no engine ever obtains) is equal to the temperature difference between the hot and cold ends divided by the temperature at the hot end, all expressed in absolute temperature or kelvins."
This is one of those things where you think you understand thermodynamics until you read it again and suddenly it gets really complicated. It is the "absolute temperature" which is the key. So I might be sitting here on a pleasant 20C day and I have next to me a black metal plate sitting in the sun and it is 40C. Let's turn those temperatures into kelvins, ie 293 and 313K. The formula above says the max efficiency is 313-293/313. That is 6.4%. As Scotty quite rightly says, those are the laws of physics. You have 100W heat input and you can only ever get 6.4W out. But, and this is the catch, you still need to move 100W through your heat engine. You need to cool the cool side with 100W of cooling. That is quite a big fan and heatsink.
Here is the next catch, and that is that all materials have thermal resistance. Look up some of the values for common heatsinks and they are expressed in degrees per watt. A big heatsink might have 0.5C per watt, but a smaller one might be 10C per watt. The big one costs more money. Say we used a 0.5C/W watt heatsink on our 100W heat engine above, it would drop 50C. But we only had 20C to start with! So we need a bigger heatsink. As a ball park figure, you might want to drop 5C between your heat source and your engine, 10C across the engine, and 5C for the cold side for a total of 20C. Will it work? Yes, but it ends up big. Take 1 square metre in the sun and you can collect 1kw. But to cool this 1kw with natural cooling (no fan), for only a 5C drop, you need about 20 metres of area. So you need a big cooling system, or water. But it has to be flowing water or a big store, because you can't have the water getting warm otherwise the heat engine will stop working.
So low temperature heat engines need huge heatsinks. That adds to the cost and that is why you don't see them in use.
But some things work in your favour. As you make the hot side hotter, you get more energy out. Let's make the hot side 420C - hot enough to melt solder. The cold side is 20C. The max efficiency is 400/(273+420) = 57%. Now we are talking. And we can make the heat exchangers smaller too. Let's say we drop 100C from the hot side to the engine, and the engine runs on a 200C difference and there is 100C on the cold side. Ok, our engine now only works across 200C, but a 100C drop on a heat exchanger is much less metal because heat tranfer is proportional to temperature difference.
There was the small catch of the hot side melting solder. This is the problem that limits practical heat engines - the hotter you go the more efficient they are, but the harder the materials are to work with. The turbine blades at the hot end of a steam turbine run white hot.
Oh, and the other small catch that you can't get to the theoretical carnot efficiency. You might only get half or 1/3 of that.
Above, I mentioned the 100C loss on the cold side. As an aside, real steam engines might have 100C loss on the cold side because you expand the steam down to atmospheric pressure and 100C is the temperature water boils at at atmospheric pressure. So you throw away that steam in a nice big puff of white water vapour out the top of the steam engine. It isn't the most efficient way to do things though, and if you are happy to condense the steam in a vacuum chamber lower than atmospheric pressure, you could get it down to 50C or lower. But condensers are big and heavy and expensive and that is why you see them on power stations but not on steam trains.
At the end of the day everything is a tradeoff. Higher temps = harder materials handling. Bigger heatsinks = more efficiency = higher cost. Do you concentrate your sunlight to get a higher temperature to get higher efficiency but at a higher cost due to the tracking, or go for low temperature differentials?
And there is another big catch the solar industry fail to mention - the sun doesn't shine at night. Nor much when it is cloudy. Nor much in the early morning or late evening. And it might not get much over the horizon in winter. So your 100W solar panel might only average 20W over the entire year.
Wind turbine manufacturers are also a bit guilty of giving you power figures that were measured in a gale, but overall, wind works out more economical than solar or heat engines. There are some great homebrew designs on the web, and if you have the time to build it, a 100W wind turbine plus battery plus inverter probably represents the best chance of making that elusive piece of green powered toast.
@Dr. Acula--I figured solar wasn't the best way to go. I've been curious about heat for a while, though, but from what you say and the fact that all systems are very complicated, it seems wind is by far the best option. I just hope it will blow enough here.
-Derrick
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PG
HaHaHa! ... I laughed out loud...thanks for that
I wonder what could be done with an old huge surplus TV dish..you know, the really big ones.
Paste reflective mylar carefully all over it and mount a medium sized solar panel at the focus point or a little in front or back of
the focus point, whatever illuminates the panel best. Have the tracking motor follow the sun...should be easy since the adjustments are
there to enable tracking of an arc across the sky....would need minor adjusting maybe 3 times/yr as the seasons change.
Might give a lot of power from a smallish panel....could provide the small amount of juice needed to turn the rotor motor
every 10-15 minutes or so to track the sun. You would need welding goggles to protect your eyes while adjusting this as it
would focus a point of light that was unbelievably bright.
If you could find a defunct old rear-projection tv you could harvest the fresnel lens from it and do much the same thing...but you
would have to actually build a rotor for it.
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- Some mornings I wake up cranky.....but usually I just let him sleep in -
Re Sandia, that is an interesting point. Sandia labs have always built the cool stuff - as a kid I was in awe of their vertical axis wind turbines. Stirling engines were around in the 1800s, but there are so many new technologies now that didn't exist back then. eg teflon for piston seals. I'll bet Sandia can come up with something new and innovative!
Post Edited (Dr_Acula) : 8/18/2009 1:57:21 PM GMT
I've had a few 50W (rated) solar panels mounted (ad-hoc) on my workshop roof for several years - facing in different directions (because now-a-days I'm too scared to climb onto my 40 degree+ pitched roof
Problem really is the initial cost of the panels and charge controller but hey - I own them and they still have a 12ish year (from 20) warranty left
Also, a small 5W panel connected to the tractor battery keeps it "fresh" and ready to start the tractor due to internal battery discharge caused by infrequent use is handy too!
I can measure the current draw from the receiver if you like but I'd guess its around an amp or so (it's an old converted Taxi transceiver re-programmed for Amateur frequencies).
Solar/wind/hydro if you can - it's a good mix with at least 1 or 2 of the 3 available more often than not; again, its the up-front cost that'll get you ;-/
I like HollyMinkowski's idea of the old TV dish. Issue here is the mechatronics needed to move the disk while tracking or hold it on position; you _must_ allow for wind loading and the like else 1) the dish launches or 2) you strip the gear teeth - both potentially expensive (and possibly dangerous to you and/or others).
Only you are in the best position to determine what is best; you need to gather data on your environment; wind, sun, rate and volume of water flow in order to determine which is the best first investment.
What's the easiest? Solar, Wind or Water depending on location accessibility, distances and local regulations.
What's the best? Water, Solar or Wind depending on same.
I'm 42ish degress south if that helps
Cheers,
HarryE.
Just to get me going, do any of you know of a website that explains how to create a vertical wind turbine? The instructions I'm currently using are very confusing.
Also--I am currently trying to keep costs down on this. I can cut scrap metal and weld different things, but I don't want to have to go out of my way to spend 50+ bucks on something with low power output. I am willing to buy different parts such as magnets though if it is necessary.
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PG
I brainstormed these once with an engineer. There are lots of designs. Wing is symmetrical in cross section and the wings are fixed (and the airodynamics of that take some thinking about as it is counter intuitive, but it is the same mechanism that allows a sailing boat to sail into the wind). You can go egg-beater style or 'H' or other variants. Officially, they are not self starting, so you need a small darrieus rotor at the top to get the blades up to a bit faster than the prevailing wind speed. (Unofficially they do self start, and one of Sandia's blew itself to bits that way). Unlike horizonal axis windmills, they will get faster and faster so you need some way of limiting the speed - eg air brakes or change the angle of the blades or tilting blades. That could be a passive mechanical system, or actively (propeller?) controlled. Then you need a stiff tower. And guy ropes at the top and those guy ropes need to clear the whole rotating part so they may need to go out at 45 degrees. So you need a bit of space. Those guy ropes also need to be very taught to keep the tower from gyrating.
The big problem (which Sandia wrestled with) is vibration in the blades. Make them thin and light and they vibrate at certain frequencies, so you can't run the turbine at certain speeds. So you need to make the tower and the wings stiff but strong. Maybe moulded fibreglass. Maybe the balsa techniques that model plane builders use. I've even pondered two wings like a bi-plane design with cross bracing with wires etc. I've also pondered a construction method using aluminium sections - trusses etc with aluminium skin over the top. Join it all with pop rivets. Very expensive but it will never corrode. But wood/fibreglass is probably more practical. One day when I get some time I'm going to build one, and if I do I think the first person I'll seek out is a mate who builds model planes.
Then there is the drive system. The bigger you make it, the slower the speed so you need to gear it up if you want to generate electricity. At least the big advantage of vertical axis is all the gearing etc is at ground level. (I talked to a guy once who services the standard multiblade farm windmills and he said that they look very romantic on a farm slowly turning, but it is something else when you are standing at the top of the tower with those sharp metal blades whizzing past).
$50 bucks? Low power output? Have you got a ballpark figure for $ to spend and for power output?
Post Edited (Dr_Acula) : 8/19/2009 6:07:04 AM GMT
Physical movement of wind and water will always be best for generating power. Solar cell outputs are quoted in the middle of a desert on a sunny day and wind generators in the middle of a gale on a windy day. Battery manurfactuers do not thouble you with their diminishing returns figures and solar cell makers do not either, three years later and both would warrent replacement.
My dad made a four foot, six bladed turbine for our garden back in the sixties (when neuclear power was to be too cheap to meter)
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