I am not sure this is the right forum but any way.....

I am a little puzzled by the lack of use of old fashioned water wheels using tidal flows ( narrow outlets) aren't being used to generate electricity.

Near where I live is a bay that tides flow in and out of at about 4 knots or more at peak times. And I was wondering if there is a simple reason why this renewable energy source is not commonly being utilized.

Possibly it comes down to pure ecconomics or is more to do with efficiencies etc.

I am sure if the tidal wheels were geared properly a substantial power output could be achieved from a generator.

Apart from maintenance it would produce relatively free electricity not unlike hydro electric power stations.

As I said there is probably a really simple reason but as yet this escapes me.

Any one?

The old paddlewheel effect isn't that efficient, current understanding is that to utilise tides to generate power the very turbines "paddles" have to be submerged at depth, this means that the force of the water retreating is greater than that of anything using the surface.

The main problem there is have you ever tried building anything underwater? Admittedly they could probably create a kind of submarinal vessel that could be anchored to generate the energy, but it's never done because of the main factors of cost. (Afterall haven't you seen coastlines erode with the power of the sea? Obviously a man made structure thats suppose to supply power to the populous would have to withstand it's full force.)

thanks...

I am however refering to bays that are calm due to shape, say an inlet or estuary.

The paddles wouldn't have to be fully submerged. as the surface would be calm but flowing swiftly....

rusting and erosion of course would be a problem but I'm sure we could solve that issue if we wanted to.

Maybe it has been tried and failed.......just wanting to know why that is all.

I am sure theres somewhere in Holland and possibly an example in russia, but I cant remember. A modern idea is big propellers placed on the seabed at places where the tidal flow is very strong, but I dont think they are off the drawing board yet.

Then I suggest you go to:
www.wavegen.com
a wave power company that has operated a prototype on Islay for years now.

1. Water from tidal force rushes into and out of a bay by placing turbins and force a significant amounts of that water through the turbines electricity can be generated. This produce electricty and variable amounts at different times depending on where the moon is in the sky.
2. Water in the deep ocean moves in currents that can be feed off by turbines like wind mill do with wind in air. This requires placing turbine in the deep ocean, power is sporadic.
3. Water at the surface and water deep at the bottom has different temperatures, this temperature difference can be feed off to power a generator by pumping a liquid/vapor changing fluid down to the depths and back up in a cycle, power is continues but requires massive infrastructure.
4. Waves can push against say a linear motor and provide electicity, again sporadic power, and advance infrastructure.

Wave power, well, the wavegen installation on islay didnt require advaned infrastructure, it was built on the cheap with concrete, but i am sure with some thought the use of concrete can be reduced. As for large turbines in deep ocean, and thermal gradient stuff, i woudl hesitate to try them because of potential effects on ocean circulation. Or maybe im being too paranoid here.
I think also that there are ideas for nearly flat, possibly piezoelectric panels for sea walls that would get energy from the waves hitting them, but I am not sure that is actually being pursued.

advanced infrastructure is need to take the pulsing sporadic electricity produce by the wave generated and turn it into usable current.

Speaking about tidal power, I can see a method using a wind mill idea I'm working on which could be floated in tide channels, anchored to opposing walls. The generating unit could be a stepper motor mounted on top which if done properly should keep it out of the water. I wonder about the vanes being fouled by seaweed which can be both long and tough. Big units might suffer less from such a problem but they would be harder to haul out and service. If the blades were sharp enough to slice through seaweed that might work but whoa to the fish or seal or otter. Enclosing the thing in a cage would require cleaning the cage but that might be the way, perhaps a very smooth plastic large mesh cage. The vanes themselves could be made of plastic.

it is obvous though is it not that there is enourmous amounts of "free" energy we can "get" from the moons orbit.

I'm just curious I guess why this is not a popular source of energy. May be it is too obvious....?

Havr you considered onvironmental impact?

Yes I have actually and I think environemental concerns are always important...but here in Australia conventional power generation ( in the main) is with the burning of brown coal and I might add, huge quanities of it. So I would hazzard a guess and suggest that tidal generators would by consideralbly more envioro friendly.

Also the energy achieved is only using energy already expended ( or force expended) to wit the moons orbit. Where as nuclear or other is more synthetic ( man made)energy creation.

Like comparing Hydro electric (use of rivers) with brown coal fired generators.

Both are using natural energy this is true but one already exists where as the other needs to be made to exist ( as useable energy)

If you catch my drift......so to speak..

All I know is that if i had the R & D budget I would run some experiments. To find out exactly why we aren't using this seemingly obvious re-newable energy resource.

I have sent of a letter and link to this forum to the people at www.wavegen.com
asking for assistance with this question......and with a little luck we may get a response.

I have received a response from Wavegen P/L and the basic statement as why tidal generation is not in use is simlpy stated as "Environmental"

The foolowing link takes you to a page that describes the issue reasonably well.

I get the impression that the main problem is that possibly we are thinking "too big" or in other words we only want big instalations and not smaller more environmentally friendly instalations.

http://www.acre.murdoch.edu.au/refiles/tidal/text.html

For example I wouldn't recommend blocking an estuary or other but only utilise it in a way that would be unintrusive. Small output generators rather than larger units.

For example,

If you were living in a house next to an estuary the what would stop you from installing a generator that serviced just you home. What sort of dynamic would be involved here?

Say you are in a small town that is next to an estuary. What would stop you adding to the towns energy grid etc etc if not supplying the whole town with nonintrusive small, compact tidal generators. ( say no bigger than the size of a medium sized camper trailer ( caravan )

Cool. Thanks for pursuing that. I can see relatively small units, light enough for a couple people to move around that would essentially float on the surface and be relatively easy to remove in case of storms or need for maintenance.

I think the same thing applies to small hydroelectric plants and small windmills, that is, they can be more environmental than large scale units. I'm working on a plan for a windmill that should be easy enough to hang from buildings or between them and trees that I believe could also be adapted to work as tidal generators. Got to get to that right quick. I hope to convert an ACAD drawing I've got of the basic idea into a gif or jpg and post it here soon. I tried to describe it at http://www.sciforums.com/showthread.php?t=35884 as I do believe the patent has expired and I'm free to share it.

sounds really good Mr Chips. I look forward to seeing your drawings

Tidal Power is in Development stage in Europe and proposed at several locations in the US. They are using various types of generators as you are thinking of. See one example at http://www.smdhydrovision.com/products/?id=27. Other companies include Underwater Electric Kite company in Maryland, Marine Current Turbines in England. Plus some others,,,

Hope this helps.

That's cool. I like the idea of mooring it to the bottom so big waves pass overhead. I see the conventional propeller is used. Appears for the device to orient itself, the over all presentation of the assembly acts as a wing to reorient itself to the direction of the flow, lots of energy is lost then in just the reorientation. I do believe I know of a design that feathers much better than propellers and is ready with minimal energy to accept the flow from any direction and turn it into rotary motion.

The ACAD drawings I have of the Hotine rotor are not advanced enough to show anything. Hold your right hand palm down at eye level and then hold your other hand with the pointer fingers touching with the palm towards you. Imagine your arms not there and that is the basic vane of the Hotine design. It's got one more tricky part, within the vertical axis that vane can rotate only ninety degrees. Now imagine blowing on your hands. Your left should be ready to accept the wind. Start rotating it about the imaginary vertical access at where your pointer fingers touch. See how the wind simultaneously causes the vane to have almost 100% feathering while it reorients your left hand into the proper angle to catch the wind? I made a model out of tinker toys using just some pegs to limit the rotation of the vanes to 90 degrees. I hung it from a low hanging branch of a Douglas Fir tree and with very little spurious gusts in various directions the thing took off to about 120 RPM. I'll draw a picture and post it. I notice the samaras of the Heliathis tree, or tree of heaven, have similarities to the design.

I was talking to a well heeled friend the other day about putting together a really simple to build and economical paddle generator.

by using a second hand automotive gearbox and a portable 240volt generator, a 8 foot diameter paddle ( say 8 paddles sharing a common centre) on a tidal flow at peak of 6 knotts. ( there is no wave or swell problems at this position.)
Just to see if a cheap generator fixed to a jetty or pier could provide a cost effective supply.

Total outlay should be less that 100 USAD for the experiment.

mmm, I figure about 21 rpm at your peak speed for the paddle wheel. What kind of RPM does that generator require? Why not use an alternator? Does your state allow selling power back to the utility? I find that a lot of auto gear boxes do a step up of maybe 6 times, 126 RPM. Those figures are common for wind mills too. 126 RPM is pretty low for most generators. Though it means a much smaller unit, stepper motors are pretty efficient at those speeds. That paddle is going to require a bit of energy to move and so will the gear box and the generator. You are also going to need to be in pretty good shape and/or get some friendly muscle to help and some pulleys probably to install, maintain etc. What kind of current at what voltage will that generator produce at that RPM? I picked up a couple of stepper motors for about $20 that should allow me to produce 20 to thirty watts per unit at around that RPM (100 watt stepper motors are more expensive but available and should still work with the same assembly but I'll be happy with anything to start just to prove the idea. I found an old bicycle and I'm going to use a wheel and it's bearing assembly, at least, for my vertical axis. If I put metal or wood in the center of the wheel, the wind should keep it upright though I'll also try to weight it to stay vertical. Then I hang it out a window or from a branch of a tree or between a couple of trees. I should be able to lift and handle an entire unit easily by myself, stepper motor fixed to the wheel on top and covered with a UV resistant plastic bottle or something.

After browsing hardware stores for a few days I think I see how to build the entire unit for about $45 in parts.

If you are near the ocean, I bet you have a lot of wind.

mr chips, I qm not qualified enough to go in to details but......

Because the tidal flow has enourmous strength and with the appropriate gearing a portable ( petrol driven 240 vlt ) generator could easilly be hooked up to the paddles via an appropriate gearing mechanism.

From what I have researched portable generators offer around 4500 watts and although they fail to mention RPM the engines would run around a constant 3500rpm ( I would think ). Whiulst there may be gearing betwen the motor and the generator this is irrelevant. AS the paddle and it's gearbox become the engine.

To convert 21 Rpm into at least 4500 Rpm may take a bit of gearing or belts however if the outer circumference of the paddle wheel was geared to a smaller driven wheel and worked through a gear box I reckon the 3500 RPM could be a goer.
the output would be around 4500 watts.
The amount of torque on the paddle if 1/3 submerged would be tremendous and I would think more thatn enough to produce the output needed to drive a generator input at 3500 rpm.
The engine I was looking at has a horsepower rating of only 11 hp

if some one new the math maybe they can calculate how much hp a paddle will produce. I would think it would be well in excess of 11 hp. ( depending on it's depth )

Also here we can sell power back to the grid.....

What is the normal average cost per watt hour do you know?

As far as I can tell with a quick search, you sell your electricity back to the utility at the same rate you buy it for as long as you are not producing a surplus (in California). If you produce more than you consume then the rate is a small fraction of the cost charged by the utilities (looks like some regulation of the public to protect the corporations, as usual). The cost of the "net-metering" equipment that allows you to do this is high, I've seen some units for $9000 USD. You also need to have code expertise to install the net-metering and that might require a hefty labor charge.

In time the costs will decrease to install net-metering but I bet there is a healthy monopoly protecting lobbying force that will challenge it every step of the way, unless, we figure out a better way to organize and become able to leave behind business as usual. Fat chance? I'm one of those who feels predominant human social experiments are basically failing and we will need something that really begins to work if we are to survive. I think others have and will come to such a perspective so the motivation and desire should grow. Science is rich with new options and getting more so every day. Will come a time when kinow-how and desire meet, me thinks/hopes

I think you are quite correct in your appraisal of the human experiment.And I agree that if humanity os to survive things will have to change.

To me the philosophy of tidal generators is quite simple.

Even if the unit cost was higher than standard by even 10% or more it is still cheaper.

The reasons are simple. Tidal generators do not pollute or have the potential to pollute the environment.

The cost of current greenhouse gasses, not to mention future green house gasses has yet to be fully paid.

Nuclear waste, unbeliveably costly. Coal fired powerstations.....ask your asthmatic child how much it costs.

and so on.

If utilising the existing energy such as "Moon energy" means a reduction in the costs overall then I am all for it.

I just look around and I see so much free energy potential, wind, tide, magnetic etc etc, and it is some times sadening to know that people seem to confortable with current systems to bother trying to find a better way.

If we were able to convert only >1% of all free energy to our needs the planet would be free of human created global energy related problems.

( including some of the turmoil in the middle east. )

But first we have to get of our arses and go look for a solution....

BTW the reason I tend to focus on tidal energy is that by nature water is not compressable where as air or wind can be.....tidal only because it is easier I guess.

Also tidal is predictable where as wind is not as much so.

But this in no way implies that wind power is not just as useful it just means that with wind there are considerably more variables to consider.