Wave and Tidal Power

[Airbrush]

Does anyone know about these methods of harnessing energy? I've seen "wigglers" that generate power from surface waves. How about these 2 ideas:

 

WAVE POWER - Standing on a pier at the beach looking down at the water, you see the waves surging towards shore and then the backwash flows back out. Suppose you built a pier-like structure parallel to the shoreline, maybe a mile or more long and about 50 feet wide. Suspend paddle turbines over the water just touching the water. As the water flows towards shore it spins the paddle turbines one way, and the water flowing out spins them the other way.

 

TIDAL POWER - If you build a wall along the shoreline to the height of the mean of high and low tides, as the tide goes from mean to high tide, water flows over the wall towards shore, which can spin paddle turbines placed along the top of the wall. Then as the tide falls, open valves in the wall to allow the water to flow back out to sea and spin paddle turbines flowing out.

[studiot]

 

Does anyone know about these methods of harnessing energy? I've seen "wigglers" that generate power from surface waves. How about these 2 ideas:

 

WAVE POWER - Standing on a pier at the beach looking down at the water, you see the waves surging towards shore and then the backwash flows back out. Suppose you built a pier-like structure parallel to the shoreline, maybe a mile or more long and about 50 feet wide. Suspend paddle turbines over the water just touching the water. As the water flows towards shore it spins the paddle turbines one way, and the water flowing out spins them the other way.

 

TIDAL POWER - If you build a wall along the shoreline to the height of the mean of high and low tides, as the tide goes from mean to high tide, water flows over the wall towards shore, which can spin paddle turbines placed along the top of the wall. Then as the tide falls, open valves in the wall to allow the water to flow back out to sea and spin paddle turbines flowing out.

 

 

Both of these are inherently inefficient.

 

It's all to do with timing.

 

Although the waves move more or less continuously for longish periods of time, they will only contact the periphery of the wheel for a short time since they are irregularly spaced out in time and distance.

It would be much more efficient if you could ge the paddles and the waves to mesh like a worm gear wheel.

 

The tides overtopping your wall will flow continuously but only for about 1/8 of any day, again making the process inefficient.

 

Further the process is capital (£, $) inefficient because you are proposing large structures that must be built before any £return can be made. This is actually what kills most hydro power schemes.

 

The most attractive from an engineering point of view, taking into account geographic, mechanical and financial considerations is to realise that tides not only go up and down the also flow backwards and forwards. And this is a relatively continuous movement 24/7.

So if we plant a single turbine generator on the seabed it will

 

1) Stay submerged and clear of traffic and other installations.

2) Produce continuous power from installation.

3) Not require massive investment in initial support works.

4) Can be added to with a second, third etc turbine as finances allow.

[Endy0816]

Second description is not too far off from a tidal barrage, though I think the power generation step is reversed. There's a whole slew of different types, easiest thing is to check the tidal/wave power pages on Wikipedia.

 

More modern methods work along the lines of what Studiot is describing though.

[J.C.MacSwell]

http://en.wikipedia.org/wiki/Tidal_power

[studiot]

This is a better link

 

http://www.power-technology.com/projects/strangford-lough/

[J.C.MacSwell]

This is a better link

 

http://www.power-technology.com/projects/strangford-lough/

Great...now I have link envy...

[Enthalpy]

The universal question about alternative energy is: how expensive ?

Because oil, gas are dirt-cheap, coal even more so. Basically, you obtain them from Earth and light them.

 

Wave energy is not concentrated, so it uses to cost much hardware to extract little power. Many (many!) setups have been proposed, you might check at the patent office. It boils down very much to the Ocean area where you can collect waves from and the necessary amount of material. My impression is that no design can compete up to now, not even against nuclear electricity - and coal is way cheaper.

 

Tidal energy looks better, because humans can exploit existing geographic features. With a thin and narrow dam, they have a huge reservoir, where all other sides pre-exist as an estuary. Adding a few bidirectional turbines is standard technology then. Existing demonstrators are old now, small and not proftable. More recent projects (Severn estuary in UK) wanted to be big and profitable, but I believe they're abandoned.

 

Hydraulic turbines on the seabed do exploit tides, sometimes in addition to permanent currents. I have doubts about their cost versus power, since the necessary area and strength is much worse than wind energy for the same power. The French EDF buys and operates demonstrators - possibly because they're sure this one will never outperform nuclear electricity.

[Acme]

Researchers to test Gulf Stream energy turbines off Florida's coast

 

MIAMI (Reuters) - Researchers at Florida Atlantic University plan to anchor turbines in the Gulf Stream's fast-moving waters off the state's east coast to test whether ocean currents can be converted into electricity.

 

The project will be carried out with the support of the Bureau of Ocean and Energy Management (BEOM), which for the first time has leased out federal waters as a test site.

...

Near the end of the summer, scientists will begin anchoring buoys equipped with a variety of sensors to the ocean floor, in about 900 feet (300 meters) of water some 12 nautical miles off the Florida coast near Fort Lauderdale.

 

The equipment will monitor the strength of the currents around the clock.

 

Scientists will then conduct additional testing with a prototype turbine to determine how much electricity could be produced by the currents, said Sue Skemp, executive director of FAU's Southeast National Marine Renewable Energy Center.

...

[Acme]

If'n y'all think this idea merits its own thread, I'm down with that. If'n ya think it belongs on the trash heap, I'm going down whining & crying like a petulant child until you accept and endorse it.

So my idea is to use coastal wave & tidal power not to generate electricity, but to generate clouds & rain. The generator devices offshore and/or onshore compress air on the power stroke and that compressed air drives misters fed by seawater. The mists [partially] evaporate, cool the air, and increase the humidity. Eventually clouds form -preferably over land- and rain falls.

Haters -or per se devil's advocates- and lovers to your places. Let the argumentation commence!

[Airbrush]

Which one of the following methods of renewable power generation is the cheapest, per total investment: wind, solar, tidal, or wave? My guess would be wind. If that is so, wind power beats those others, so build up the cheapest methods first.

So my idea is to use coastal wave & tidal power not to generate electricity, but to generate clouds & rain. The generator devices offshore and/or onshore compress air on the power stroke and that compressed air drives misters fed by seawater. The mists [partially] evaporate, cool the air, and increase the humidity. Eventually clouds form -preferably over land- and rain falls.

 

That sounds nice. You should see the last episode of "Cosmos" that deals with global warming. If you could irrigate deserts, by using renewable energy, that could save the planet.

Edited June 8, 2014 by Airbrush

[studiot]

 

Which one of the following methods of renewable power generation is the cheapest, per total investment: wind, solar, tidal, or wave?

 

Well surely that has also to depend upon where your place your generator?

 

solar is not much use at the North Pole, but then again wind is not much good in the doldrums nor is wave power in the Sahara.

[Acme]

Which one of the following methods of renewable power generation is the cheepest, per investment, wind, solar, tidal, or wave? My guess would be wind. If that is so, wind power beats those others, so build up the cheepest methods first.

I think there is too much variability of circumstance to make such a simple conclusion on economic value. Wind power makes sense in areas that have, well... wind but may be relatively cloudy or have limited space for solar arrays whether PV or solar ovens driving steam turbines. Solar may be more economical where there is area enough, more sunny days, and 'less' wind. By the same token, tidal & wave generators have to be situated where there are tides and waves. As with much of technology, the price tends to go down as production goes up.

 

 

 

...

So my idea is to use coastal wave & tidal power not to generate electricity, but to generate clouds & rain. The generator devices offshore and/or onshore compress air on the power stroke and that compressed air drives misters fed by seawater. The mists [partially] evaporate, cool the air, and increase the humidity. Eventually clouds form -preferably over land- and rain falls.

That sounds nice. You should see the last episode of "Cosmos" that deals with global warming. If you could irrigate deserts, by using renewable energy, that could save the planet.

 

Thanks. I was thinking that compressing air is an unnecessary complication to my scheme and that the devices could directly pump the sea water through spray nozzles. For a wave generator they could be double acting so that some nozzles spray on the up-stroke while others are recharging with water through a simple flap-valve, and then on the down-stroke the recharged nozzles spray and the discharged ones refill. Think simple cylinder pumps like a kid's squirt gun as illustrated below.

 

source

 

I'm thinking driven by this type of anchored wave generator. (I think this particular project may be stalled by a contractor default.) >>

 

source

[Enthalpy]

[...] my idea is to use coastal wave & tidal power not to generate electricity, but to generate clouds & rain. The generator devices offshore and/or onshore compress air on the power stroke and that compressed air drives misters fed by seawater. The mists [partially] evaporate, cool the air, and increase the humidity. Eventually clouds form -preferably over land- and rain falls. [...]

 

Random thoughts:

- What you need is mechanical power. Wind energy seems cheaper for that than tidal or wave power.

- The atmosphere is huge. Direct human influence has a worry of scale. You need huge and very efficient methods.

- Moving air needs unnecessary power. You better rotate many parallel disks, soaken in water at their bottom, swept by wind at the top. Room humidifiers work like that.

- Seek help from biology, it's cheap at a big scale. Just pump seawater to a plantation that accepts salty water and will evaporate a part.

- The Ocean surface is already a huge exchanger with air. Dry air (Namib, Atacama) occurs when the surface water is cold. If you can immobilize the shallow water and warm it over some km², you might save the active exchanger. A black plastic film 1m below the waves? Dark algae hold in place?

[Acme]

Random thoughts:

- What you need is mechanical power. Wind energy seems cheaper for that than tidal or wave power.

See my modifications/specifications in post #12. The wave power is there, so might as well use it. Keep in mind the waves are wind generated as well.

 

- The atmosphere is huge. Direct human influence has a worry of scale. You need huge and very efficient methods.

Acknowledged. I think I have proposed as efficient and simple a means of increasing humidity as practical. Small scale experimenting & theoretical calcs should give a decent idea of the necessary scale to form clouds & rain, and from that a decent idea of whether or not the bang would be worth the buck.

 

- Moving air needs unnecessary power. You better rotate many parallel disks, soaken in water at their bottom, swept by wind at the top. Room humidifiers work like that.

A good alternate scheme that's worthy of small scale testing to compare with spray nozzles. One potential of spraying is few moving parts and getting the water to a higher altitude with less material than the wheels. Moreover, strong winds might damage the overexposed wheels and shut the whole thing down.

 

- Seek help from biology, it's cheap at a big scale. Just pump seawater to a plantation that accepts salty water and will evaporate a part.

That requires a lot more material and land use as well as adding salt to the land. I was thinking though that my scheme may make the water around each of my humidifiers more salty. ??

 

- The Ocean surface is already a huge exchanger with air.

Yes. But the misting increase the surface area of water exposed to air and so generates humidity that otherwise would not be generated by normal evaporation at the surface.

 

Dry air (Namib, Atacama) occurs when the surface water is cold. If you can immobilize the shallow water and warm it over some km², you might save the active exchanger. A black plastic film 1m below the waves? Dark algae hold in place?

Mmmmmm...sounds problematic to stabilize such sheets, not to mention all the marine life, sediments, and assorted trash that would accumulate on the sheet. Thanks for thinking on it!

[Airbrush]

 

Well surely that has also to depend upon where your place your generator?

 

solar is not much use at the North Pole, but then again wind is not much good in the doldrums nor is wave power in the Sahara.

 

That is a good point. The solution to our energy problem should be "all of the above" methods. Different regions would use different methods. You could also have two or more methods working in the same area. Coastal areas always have plenty of wind, so you could have power generated by wind, solar (photoelectric and solar-heat), wave, and tide ALL in the same coastal mega-power-plant structure, and desalinate sea water also to be piped to the deserts for irrigation.

 

Geothermal would be used where the heat is close to the surface.

Edited June 9, 2014 by Airbrush

[studiot]

Airbrush, now your rocking! +1