Windmills and Mechanical Energy Storage

I know very little about electricity-generating windmills, so my comments here may seem naive to those who do. However, I know that some very smart scientists sometimes read my web page, and I thought perhaps my comments might prompt their more-knowledgeable replies. I started thinking about this during the recent Colorado wind storms, when I noted to my wife that it’s too bad we can’t harness some of that violent air flow.

As far as I can tell, there are two big problems with windmills. First, they work only at certain wind speeds. If the wind is too slow, they don’t work. If the wind is too fast, they either break or don’t work. Second, they directly turn a generator which in turn charges batteries. (At least this is how the windmill worked that I’ve seen close-up.) Batteries are expensive, limited in capacity, limited in life span, and inefficient in that they leak energy. (If they’re not hooked up to batteries, you’ve got to somehow get that energy to someplace it can be used, which creates a new set of thorny problems.)

It occurred to me this morning that it might be possible for a clever engineer to solve some of these problems with an old-school approach: mechanical energy storage. Basically what I have in mind is a big spring-loading system, or maybe a flywheel.

It seems to me that if somebody could get a windmill to do two things at once, it might work pretty well. The first thing is to capture energy at all different wind speeds. Maybe the traditional propeller mill can accomplish this, or maybe what’s needed is something more cylindrically shaped attached at two points. The big key is a geared system so that the mill can always spin (above a certain minimal wind speed) within a reasonable range. The second thing is to store the energy locally in some sort of mechanical-storage device. (Hell, it could just slowly lift a giant boulder in the air or something.) This mechanical storage system in turn runs the generator as needed. Also, you could hook up other moving things to charge this device.

I think part of what made me think of this are the giant mechanical clocks in Neal Stephenson’s Anathem. That book also makes me sensitive to two points: most ideas are wrong (including most of the ones in that book), and the good ones are hardly ever original. I suspect one or the other is the case here, but nevertheless I thought I’d give it a go to see what more “praxic”-minded people have to say about it.

10 thoughts on “Windmills and Mechanical Energy Storage”

  1. I’ve read a bit on this — not a lot, but I got somewhat interested reading about Savoinius turbines. Vertical Axis Wind Turbines (just web search for VAWT) have tradeoffs, but some designs are more forgiving of variances in conditions. From what I’ve read, the Gorlov types tend to perform over a wider range of wind speeds. But a Savonius is very easy to build yourself.

    Lots of things suggest themselves for mechanical storage of energy potential. I suspect the practicality of them makes them less useful than chemical storage. But, suppose you could pump water uphill into a reservoir, to be metered through a hydro generator based on demand. Yeah, you’d need to live near a large enough water source, to which you had some usage rights, in order to do that.

  2. I was just thinking about this as a potential solution to the problem of storing the intermittent energy provided by solar and wind power. Specifically raising a very heavy weight as a means of storing energy and then lowering it very slowly as a means to turn a generator. I’m no engineer so I’d have to defer to others as to it’s viability. There isn’t much out there as to whether or not it has been considered.

  3. Fly wheel energy is for a short period for few minutes. I dont think it can be used as alternative to battery storage. But it can defnaitly boost up the generator instantly.

  4. As I have since noted, small-scale mechanical energy storage devices don’t seem to be practical. However, my same scientist-friend noted, batteries can store much more energy in a small area with relatively little loss. If battery technology continues to improve, they could store not only back-yard electricity but, perhaps, run our cars. I think it would really take advances in both solar cells and battery storage to make local energy production worthwhile. For large-scale production, nuclear looks like the obvious choice.

  5. I’ve also been imagining the spring-storage idea, which led me to find this blog, and realize that others out there are thinking along the same lines. It seems to me that storing energy from a rotating turbine by winding-up or compressing springs would be relatively easy to achieve, and could fit a lot of energy into a reasonably small space. Also, when you think of the millions of scrap cars, trucks, etc., piling up every year, all with springs attached, the base spring-steel material is available to use directly, or to be recycled into springs designed specifically for this task.

  6. I too thought of just about all these things (gears lifting wieght,pumping water, springs) but i also learned on discovery channels distroyed in seconds that windmills have breaks so they can keep from spinning out of control and distroying themselfs, as in the case of the one in they episode with the faulty breaks. Then i was wondering the least we can do is make those breaks regenerative breaking like the hybrid cars.. not sure if they are designed with regenerative breaking in todays models or not.

  7. In a subsequent post we established that relying on gravity wouldn’t work. However, it might be possible to compress heavy-duty springs. I don’t know why a windmill couldn’t simply be geared to accommodate different wind speeds. Converting wind energy to outdoor heating hardly strikes me as sensible.

  8. Storing energy in weights is not practical. Let’s say you had an elevator shaft in a 400 ft. tall building. You could lift 50,000 lbs. to the top with a motor/generator. If you needed the energy and reversed the weight it would generate only 9.6 KWH, enough to keep the hallway lights on for 2 minutes.

    Pumping water and using that potential energy requires incredible space. There is one on the Great Lakes that uses 1,000 acres for storage.

    There isn’t enough potential energy in “weight” to make its use practical. It’s Grandfather-Clock thinking.

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