Being a keen caver, I've often experienced the drafts within caves. At night the rock can be warmer than the outside air, so the draft rises and leaves through the top entrances while in the day the rock is cooler so it falls.
The drafts are often helped along by the falling spray from waterfalls too. Though harnessing the power of falling water this way would be rather inefficient.
For a small scale power plant, a drafting cave is a drafting cave all year round and so an ideal place to put a small turbine.
If most of the drafting action is coming from waterfalls dragging air downwards, the draft will generally be going in the same direction all the time.
Thus putting a small wind turbine in a cave could be a light an elegant way of turning an unpleasant draft into a permanent source of power for charging batteries or making a cup of tea – slowly.
On the other hand, this could be a useful source of power for remote places with access to a handy cave of course.
Phil-- PGL, Jul 06 2008 Cave Energy Storage http://www.sandia.g...l/NR2001/norton.htmCompressed air in a cave to store energy [csea, Jul 20 2008] The draught is a function of differential temperature - use a Seebeck-effect array to generate power ?-- 8th of 7, Jul 06 2008 To do that, you'd need something close that has a different temperature rather than just a flow. Anyhow, the temperature difference isn't very large. Could use a large copper stake buried deep into the earth as a source of heat?-- PGL, Jul 06 2008 What about harnessing cave-dwelling hamsters somehow?-- Texticle, Jul 06 2008 I think a turbine would be much simpler than a seebeck array.
Not much power, but what is there is good. Bun-- Bad Jim, Jul 06 2008 I was told that one way to discover a cave was to wait for a storm or weather front to pass by, and look for the ejection of humid air into the low pressure weather region: a cloud of vapour comes out(I think it was a cave guide near Orange, Australia, who told me).
This effect could be used with large cave systems, to generate power from small changes in barometric pressure.-- Ling, Jul 06 2008 Should hook it up to a lamp, duh.
S'cuse me is there any chance your name stands for poly (glycolide-co-lactide)?-- daseva, Jul 07 2008 //What about harnessing cave-dwelling hamsters somehow?//
"The - winged - kind, should do Robin." "Alfred!" "Begin breeding - mosquito larvae - in isolated pools and release the grown ones into the various airstreams at night. The bats will be forced to fight the air currents in - order - to - feed thus generating more wind and - increase the Bat-cave power potential ... exponentially." <+>-- 2 fries shy of a happy meal, Jul 07 2008 //-//What about harnessing cave-dwelling hamsters somehow?//
burn them... , would be a good power source for hermits (the turbines and the burnt cave dwelling hamsters)[+]
question is how do you get out of the cave with a turbine in the way?-- xxobot, Jul 07 2008 // how do you get out of the cave with a turbine in the way //
In very thin slices ......-- 8th of 7, Jul 07 2008 I am surprised that a ‘keen caver’ would interfere with the evolutionary growth of a cave. This would severely impact the temperature differentials. External barometric changes will cause some slight airflow as a sealed cave compresses or decompresses, and a slight breeze over caves with multiple openings will cause a differential but most of the breathing comes from expansion and contraction air (also barometric) due to temperature changes.
The described mechanism has a strong diminishing return associated with it because it restricts the caves breathing stagnating the air. Significant flow reduction would kill the cave and likely derive little energy.
One might recommend this concept for old salt or coal mines or perhaps other major tunnels that have been abandoned but it would make them even more dangerous for spelunking at the expense of perhaps dubious gains.
Instead, just mine the bat guano. I hear it is a great fertilizer, grows mushrooms, and can be harnessed for methane.-- CwP, Jul 07 2008 Stomp that misplaced sense of accomplishment, [21]! Yea!
'Cave Windmills' will be posted around the year 2028. By that time 50cent won't have too many questions left, but plenty of bones to give. ;)-- daseva, Jul 09 2008 Presently, when on expedition, we use solar cells at the surface camp. Though with subterranean camps being in place for a month or more, a power source to recharge batteries would be great.
However, the total power consumption of all the lamps is pretty low. So it would only be needed if there was a constant drain.
Cave radios which can transmit through over 500m of rock need to be turned off to conserve batteries - therefore the surface can't reach the subterranean radio all of the time.
This leads to a use... I might have to bake this idea (sorry about that).
- daseva, "PGL" is not a single chemical element. Rather a mixed bag of numerous hydrocarbons and a bit of lime-scale.-- PGL, Jul 19 2008 See [link] for where to store your cave-wind energy for those windless times...-- csea, Jul 20 2008 If there is a waterfall, I would think it would be more benificial to turbine the waterflow instead of the air.-- Zimmy, Jul 22 2008 Cave water may have cave creatures living in it.
These are all great ideas for dead caves and mines. Howver, even breathing in a living cave impacts its environment, growth, and evolution. Drawing or adding energy in any form has an impact. Thus changing water flow, air flow, contents (plus or minus), has an impact.
Living caves can withstand visitors to a degree but a stream of visitors can cause all sorts of issues. Newer public caves are now installing alternate entrances and air locks, special walkways and lighting, etc. They estimate the number of humans that have entered and how long they were there. They use this to estimate the amount of water (evaporation), carbon dioxide, noise, light, heat, etc and attempt to counter these impacts.
In extreme cases, even air re-breathers are used by explorers. New low impact inventions, like LED flashlights/torches last a long time, generate very little heat, and last a long time. Similar care taken by everyone leaves cave pristine for any present or future inhabitants and future visitors. So we should modify some of these ideas to resolve the initial problems yet preserve the cave itself.-- CwP, Jul 24 2008 random, halfbakery