Power from Trees

[ghurd]

Hi John,

I think the power is there (at least with big enough trees), just no good way to get at it.

Same problems stepper motors have would show up.  I think.

G-

[jomoco]

Hey Craig,

I hope you don't give up on your approach to get useful power from trees, and I have a few suggestions that might help you succeed.

You want to take advantage of the bone shattering torque of these giant conifers as they move, be it a little or alot. your approach seems well suited to do that. I suggest you incorporate an extremely large flywheel in your setup and use a oneway sprague assembly to connect it to your chain drive. A one way sprague is far superior to either a oneway clutch or any pawl assembly because it has little or no drag when it is free wheeling. Try going to a junkyard and looking through torn apart automatic transmissions such as ford c6 and c4 trannies or even toyota camry.

You may have to use more than one depending on the weight of your flywheel. With a large enough flywheel and some good step up gearing you should be able to generate some useful power.

By the way your weight estimate of 3000 lbs for an eighty foot pine seems way low to me. Of course it varies by species and each trees individual structure, but I think you could probably triple your number. All conifers are particularly well suited for your project because of their excurrent growth patterns ( they usually grow straight up ) and their ability to bend in the wind without breaking.

I hope this info helps you and good luck with your project.

jomoco

[Ungrounded Lightning Rod]

My guess:

 - Some of it goes into pumping water up the tree.  (Tree veins have valves in them like those in your leg that help pump blood back up when you walk - which is why it pools and may clot if you sit still for hours at a time, or make you pass out if you stand still without occasionally flexing your legs.)

 - A bit does go into heating the tree.

 - Most of it goes back into shoving air around.

Trees are massive and springy with a lot of wind resistance (though leaves typically fold up into low-resistance cone shapes in high winds).  Set them swinging and they keep swinging until the energy is lost - but most of it is lost to wind resistance.

[Ungrounded Lightning Rod]

IMHO the power in tree swaying has a mechanical impedence problem.  It's high force and low speed.  Gennies like high speed and low force.  You'll probably do better using it for things like pumping water rather than generating electricity.

The other problem is that a tree is a TERRIBLY inefficient turbine.  (Makes up for it by being a LARGE one, though.  B-)  )

[craig110]

I agree that the 3000 pound figure is likely conservative.  I couldn't find a good figure to use, so I just took the density of wet pine (40 pounds per cubic foot), calculated the weight of a cone 1.5 feet in diameter and 80 feet high, added 20% since the trunk isn't a nice cone but tapers slower in the bottom half, and then added 50% for the estimated amount of mass in the branches compared to the trunk.  I wasn't shooting for a perfect number, but rather just a ballpark number of the number of foot-pounds of energy to see if this was worth going after.

As to the sprague, I'd rather not root through the junkyard due to time issues.  Do you know of any good online places that sell them?

Jomoco, if you'd like to go more offline with this, how about emailing me at craig_y@pobox.com?  Thanks.

Craig

 

[craig110]

The trees might be in the "TERRIBLY inefficient turbine" category, but aren't they more efficient than not having any windmill?  Comparing efficiencies requires comparing options that are viable and I'm in the situation of not being able to raise a windmill.  Not everyone lives on many acres out in the middle of nowhere.  I have a quarter acre lot, close neighbors, live under the approach path of an airport and have trees that sway.  I can wish I lived somewhere else where a windmill is practical or I can make use of the trees. ;-)

As to the high force and low speed issue, this can be overcome by the g word that I hesitate to use since some folks will jump up and down claiming a loss of efficiency.  They would be right, but this is again a case where a less efficient tapping of a high power source is better than watching the trees sway in the wind and getting nothing out of it.  Besides, if my approach to slaving multiple trees together works well, I won't have to sweat a loss of efficiency somewhere since I can overcome it by adding more trees to my generator.

Craig

[craig110]

"It assumes that 2 folks can't possibly come up with the same idea independently. Obviously that is not true."

At the risk of going down the patent pros or cons issue, I just want to point out one issue with the quoted comment.  One of the requirements for getting a patent is that the invention has to be non-obvious to people involved in that particular field.  If two people come up with a particular idea at about the same time and apply for patents, they'd both likely run into the problem of proving to the USPTO that the idea isn't obvious to people in that field even though two of those people came up with the same idea at about the same time.  It isn't guaranteed, but quite likely, the uspto would rule that the two applications show that the state of the art in that area had progressed to the point where the invention was now obvious to people in that field and would give neither the patent.

Craig

[ADMIN]

OK, I'm not understanding the physics here, of either the tree or the 'pendulating gravity sail.'

The distance that a tree moves in the wind is dependant on how much of the power available in the wind pushes it against the elasticity of the structure, after the Betz limit is applied. 100 percent of the wind force, reduced to >59.26% (Betz) and reduced further by whatever the tree's efficiency is in catching the wind, is making the tree move X feet.

Attach the tree to your alternator/generator with your cables, and you have in effect guyed the top of the tree in place, with the amount of your guy wire force against this deflection dependent on the power that your alternator can extract. The more you load the alternator, the less distance the tree will deflect.

As I see it, the weight and height of the tree are completely irrelevant. The only force involved is that of the wind...you MUST have a power source, and the wind is it. Build your generator to extract only a little power from the wind, and you'll get low output with the tree deflecting a bit less than what it did before being hooked up to the cables. Build your generator to extract lots of the power available, and the tree will no longer sway very much, it's effectively guyed in place. If your generator can extract both power from the wind pushing, and power from the tree springing back, you will salvage a slight amount of wasted energy, since the elasticity of the tree stored some potential energy.

You folks need to get back to the basic physics here -- the ONLY power available here is from the wind. Bending the tree or the sail X amount is taking up 100% of the power available in the wind, after all losses ranging from Betz to 'sail' and generator efficiency are factored in. The more resistance to movement you place on the tree from the generator's extraction of available energy, the less the tree will move-- a decreasing spiral of math that will land you firmly on the physics of "how much power is available in the wind, and how much can we extract?" THERE IS NO EXTRA ENERGY HERE. The wind is the only source. The more you try to extract, the less the tree will bend.

I'm not even slightly impressed by patents -- thousands of unworkable ideas have been  patented. This sounds like yet another.

This topic is pretty marginal for this discussion board -- but we left it up since it's becoming 'hot' with lots of replies.

ADMIN

[ADMIN]

I should add that you could get SOME power this way, but it will be a tiny fraction of what's available in the wind. The typical cP of small wind turbines is around 0.30, and this being technically a 'drag' machine, the cP will be much lower. The big question is, what does this machine produce in 10-20 mph winds? High winds are almost irrelevant, since they occur so infrequntly. Of course the power available in wind goes up by a factor of 8 when windspeed is doubled -- but when you factor in the dismal efficiency of such a tree-swaying drag design, I can't see any useful power being produced--enough to power a flashlight in a high wind, maybe.

It's all fun to think about and brainstorm, but physics are getting in the way of this speculation. Sorry you can't put up a wind turbine on your land, but maybe try solar? You'll spend less money and get more power.

ADMIN

[jimovonz]

You might also consider that you can only possibly recover energy from a change in wind speed with this method. W=FxD. The tree can only move so much. If the wind is constant then the tree will maintain pretty much a steady state and there will be no movement from which to extract energy. Given this, I think your Cp will be dismal. Why limit yourself to such a small proportion of the energy?

[Kwazai]

the 'pulley' you've drawn for the power out put could probably be a rear bicycle wheel with derailleur(sp?). not sure how you'd get any rpm out of it though.

just a thought.

Mike

[craig110]

I'm not sure who you are directing the physics reminders to, Admin.  If to me as the original poster, of course the tree swaying is caused by wind and, of course, the trees face the same Betz limit as do windmills.  And yes, the more power we try to extract from the comparative swayings, the more the swayings are dampened.  I don't believe I ever said otherwise to any of these.

Craig

[whatsnext]

This is just me talking out loud but I think he's suggesting that your idea doesn't have much merit and that the whole point of this site is sharing practical ideas and applications that people can use now not pie in the sky dreamings. I'm really suprised this thread has not been tossed into the same free energy basket that many before have been. You, of course, could prove the doubters wrong by building a funtional unit that actually produces usable amounts of power instead of insisting this will work before you do.

John..

[craig110]

Hi John,

Yes, I'll keep this site updated with the results, whether it is a lot of power or just enough to light a flashlight, as was suggested a few replies ago.  Please recall, though, that my original post was asking for other peoples' input before I started putting it up which is what this board is for.  I've never insisted that it will work.  The only replies I've pushed back on are those that dismiss it out of hand or were telling me to forget it and just put up a windmill.

I've gotten good input from the replies, and I thank everyone.

Craig