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Wind power is getting cheaper and mass-produced consumer solutions have made independent wind power a reality. The problem for non-grid users is that the wind doesn't blow equally strongly at all times.
Existing stand-by power systems are not wonderful: Generators are costly to buy and maintain
and have a start-up lag. Batteries are expensive too and the conversion-reconversion inefficiency is taxing. Fuel cells are expensive and have the same inefficiencies as batteries. Pumped storage is about the worst in all categories above.
I propose mounting a large flywheel at the base of the turbine tower, where torque and precession won't affect the operation and stability tower and systems. The generator and gearig will be moved down to the base too, reducing head-weight and tower construction cost. The flywheel will be driven directly off the drive shaft via a continuous gear.
The generator/start-motor is spun by(/ spins the) flywheel. An electronic governor controls the delivery of electricity from the flywheel to the generator and prevents over-speeding. The start motor can be de-rated from what is notmally needed because the flywheel can store enough energy to quickly spin the blades up to efficient speed.
This solution minimises energy conversion efficiencies, ensures continuous- on demand power and cuts capital costs.
Seprate wind-flywheel systems are baked in grid applications, but not AFAIK on non-grid homestead systems.
JET Flywheel
http://www.jet.efda...004power/index.html
A 700 Ton flywheel, used to store energy. [ssam, Jun 20 2007]
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Easier to store spare wind in batteries, no? Maybe not, as capacities may top out too quickly. |
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So you say that this setup already exists, it's just not used off-grid... that doesn't seem like much of a change to my mind, uneducated as it is about such matters. |
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If I could bun this twice and get rid
of your surfeit of bonyfishiness, I
would. Kudos for original,
creative, and why-didn't-i-think-
of-it first lateral thinking. |
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The fewer energy conversions the
better. There's energy lost both
on the way into and out of
batteries. Store rotational
momentum as rotational
momentum, and only convert to
electricity when you require it. |
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So instead of going
'mill -> current -> motor ->
flywheel -> generator -> current
with losses at each stage, you're
going
'mill -> flywheel -> generator ->
current. |
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Flywheels are already economically
on par with, or better than,
medium to large sized battery
banks. A quick search of the
Wired Magazine website will turn
up their excellent article from a
couple of years back (essential
reading in the art of 'baking) |
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Vertical axis wind turbines such as
Savonius or Darreus would
simplify things mechanically. |
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The interesting part would be
reliably dealing with the efficient
transfer of power between the
flywheel and the windmill, with the
extremely wide range of relative
speeds involved. Some kind of
robust CVT - continuously variable
transmission - perhaps. Which
would itself incur efficiency losses,
and that's where a better
mathematician than I comes in... |
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But I can add (-2 +1) :-) |
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Does generator -> battery generate losses? Are you sure they exceed the losses sail -> flywheel? There will have to be a lot of stepping in there... |
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This idea is as baked as a 2 week old manatee washed up on the river bank having been run over by some petrol power boat freek. |
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[BunsenHoneydew] doesn't seem to have read your description as you even admit it has been grid baked. |
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The losses are still huge and fly wheels are best for short charge-recharge and have bearings which wear out unless you use that magnetic vaccum mumbo jumbo. |
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Simile pedantry: surely the aformentioned manatee would be soaked rather than baked. |
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Woah, guys.... this is how it is baked: Grid systems, which cover several states or even whole countries include systems for energy balancing, including pumped storage, hydroelectric power, gas-fired power stations and to a very very small extent - flywheel systems. The Grid uses these technologies to balance systems demand and unpredictable electricity sources, like renewables. |
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What I am proposing is an integral unit with a direct kinetic coupling of a flywheel to a wind turbine. That is entirely different and also new. |
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[phoenix] Yes, there is some gearing complexity, but not much more that in a conventional wind turbine. In fact, the flywheel solution suffers less losses in converting the energy but stores it less efficiently over longer periods than a battery. You also save energy on the spin up, as I have said. Fixed installations can also be cheaper than batteries of the same power output. The reason why they are not more widely used in consumer applications if weight and torque reaction. This is not an issue in a fixed installation. |
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An advantage to this approach is wind gusts are absorbed by the flywheel, eliminating the need to brake the windmill. |
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A big flywheel will need to be on the same axis as the earths rotation. Otherwise, two counter rotating, gimbal mounted flywheels. |
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[Stephen92082] Fortunately that's not true - big flywheels can be mounted in any orientation you like relative to the Earth, as long as the bearings are strong enough to transmit the gyroscopic turning moment - not a big requirement, the forces involved are small in comparison to the weight of the flywheel which the bearings have to withstand anyway. |
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[JET flywheel] is an example of a flywheel for a very different purpose, and a fine demonstration of what's wrong with flywheels: they're fearfully expensive (and heavy, and large) for the amount of energy they contain. JET needs them for a special reason: it needs a very high output from its energy store, for very short periods. Only capacitors and flywheels can do that. |
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But the total amount of energy stored is remarkably small, considering what a huge expensive installation they've got. |
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For domestic wind turbines, a flywheel might be used to even out brief spikes in supply from gusts, or to supply brief spikes of demand - but one that could fill in for calm days would be ridiculously big and expensive. |
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Finally, most of the load on a turbine tower isn't the weight of gearing, generator, flywheel (if any) or anything like that: it's wind loading. There's no sense adding to the complexity and expense of the system by moving any of those things to the bottom of the tower. |
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cost efficient and eco-friendly. |
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// cost efficient and eco-friendly // Wind turbines? Certainly. Flywheels? Much less so: they store very little energy for their size and weight, so if you're trying to store quite a few kilowatt hours they consume a lot of raw materials. The raw materials aren't particularly eco-nasty, but the sheer quantity of them needed is so much greater than the quantity needed for other technologies that it more than makes up for it. |
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They do have the advantage that if well engineered, they give you a high round-trip energy efficiency compared with other technologies - for short storage times. It's very difficult to engineer them to give you long storage times though. |
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I know I'm years late, but flywheel energy density is comparable to or exceeds many battery types, significantly better than the lead acid batteries commonly used for off grid power storage. That means they are not heavier (if you've hauled around mass quantities of lead acid batteries, this is intuitively obious). |
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Likewise, if you spend a little bit more up front for magnetic bearings, the energy efficiency (output/input) can greatly exceed these batteries, and these bearings can keep the wheels spinning for extremely extended periods without significant losses. The one factor that does make flywheels difficuly is the heavy shielding required to reduce damage in case of catastrophic failure, but this could be designed into the base of the mast/concrete footing without adding significant extra cost to the wind turbine tower. |
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