Tidal Turbines

There are several designs for using the energy of the sea to create electric power. Here's another design.

It's a very good idea. Not very intrusive to wildlife either. Really the biggest hazard is going to come from fishing, but proper navigation data can prevent the majority of accidents.

Again, way cool.

They've had one in France for a good few years now.
My understanding is that it has big maintenance problems because of the sand carried by the tide eroding the turbines.

Cool idea. It'll take lots of time to develop to a production level. And it still faces the same problems as other wind, wave and tidal supplies in that it's hard to control output. One has to wonder at the cost/benefit on them. If it's like wind turbines, then each one will take 30 years to make enough power to pay off the construction of one unit. Being in the sea, these won't last that long though. Hopefully, they'll be able to figure all of that out.

The wave effect generators are online now, off the Pacific Northwest coast.

Hallen said:

And it still faces the same problems as other wind, wave and tidal supplies in that it's hard to control output.

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Unlike wind and waves, tidal output should be quite predictable. I'd say the more likely problem would be expensive and regular maintenance requirements.

The bigger limitation of the tidal turbines comes more from the geography of a given area. In some places where you've got extreme tides, then I could see them producing a fairly large amount of power.

The real problem with these is on the maintenance end. They'd be a bastard to maintain and take care of.

movieman said:

Unlike wind and waves, tidal output should be quite predictable. I'd say the more likely problem would be expensive and regular maintenance requirements.

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Of course. But, are the tides going to be most active when you need the most power? Probably not. Not on a regular basis anyway. We can't control the tides. We can control opening the gates on the dam. Electricity in large quantities cannot be stored, only routed. If your tidal generators produce 1.21 gigawatts when the grid only needs 1 megawatt, then it's useless. Conversely, you can't step it up when you need to. Tides and waves have the advantage over wind in that they don't ever complete quit moving, but how big the wave or how fast the tide, there's still no control there.

Hallen said:

Of course. But, are the tides going to be most active when you need the most power? Probably not.

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No, but if you know you're going to have 10GW of tidal power at tea-time on Tuesday you know you can shut down or idle a dozen other power stations at that time. With wind, for example, you have only a vague idea of how much power you're going to get three days from now and it can go from lots of power to none over the course of a few minutes.

Movieman is correct: tides are uber-predictable, giving them an advantage over wind.

But even beyond that, depending on the design, tide power can be put on tap, almost literally. Floodgates controlling the in- out-flow of seawater can be used to modulate the power output. This also increases your maximum power output. By keeping the floodgates closed from high-tide to low-tide (or low-tide to high-tide), you maximize the difference in potential energy (or levels) between your flood tanks and the ocean. Open the floodgates at this maximum potential difference, and you get a burst of power (albeit for a shorter period of time) that far exceeds what would be possible without floodgate throttling.

While tides are convenient, using ocean currents is as easy and they keep going nearly all the time.Simply anchor a power station/ship in a place with a good current and drop a turbine into the current. The amount of electricity would depend on the speed of the current and the size of the turbine.There are currents that run at several knots all of the time.

waylander said:

They've had one in France for a good few years now.
My understanding is that it has big maintenance problems because of the sand carried by the tide eroding the turbines.

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I would think that corrosion from seawater would also represent a significant maintenance factor.

The sea is a harsh mistress.

Hey, am I the first person to say that?

Some engineers way better than I am have worked on tidal generator projects.

I think the company went bankrupt before they got put in place, but this was at least 5 years before oil spiked.

Tidal power dates back to before the early modern age. mostly water wheels in estuary mouths.

The real problem with renewable and intermittent power systems is power conditioning. I run a four megawatt backup plant and it cost about a million dollars a megawatt for conditioning the power to reliable levels. More if you can not provide continuous power. Grin, my UPSs (we have five of them) weigh about seven tons each, without the batteries, (198 ea @ $3,000.00 per battery)

Regards,
Kevin

+1 To Hallen's Back to the Future reference.

Hallen said:

Of course. But, are the tides going to be most active when you need the most power? Probably not. Not on a regular basis anyway. We can't control the tides. We can control opening the gates on the dam. Electricity in large quantities cannot be stored, only routed. If your tidal generators produce 1.21 gigawatts when the grid only needs 1 megawatt, then it's useless. Conversely, you can't step it up when you need to. Tides and waves have the advantage over wind in that they don't ever complete quit moving, but how big the wave or how fast the tide, there's still no control there.

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As noted, tides are predictable -- but, still, it's not ideal. Some recent papers have made a good case that wind turbines and solar plants hardly provide enough energy advantage to be worth building -- IF (I rarely use caps, but I wanted to be sure of this point) if, that is, they're simply hooked into the grid, to pour energy into it as it's produced.

Maybe if we really overhaul and modernize the grid, it'd be flexible enough to take maximum advantage of solar, wind or tidal power whenever it's generated -- but another possibility is to use an energy storage medium, and have those energy sources not directly part of the electric power grid. I like the idea of using the power to make synthetic liquid fuel, using water and carbon dioxide from the air. This would be carbon-neutral, and if you could take extra CO2 from the air in the process and sequester it, so much the better.

One of the reasons it's hard to get past fossil fuels is that, let's face it, they work just great (except for all the unfortunate consequences). I can spend five minutes filling my car's gas tank and then drive hundreds of miles. You can fill the tanks on a jetliner and fly hundreds of people halfway around the planet at 500 mph. Amazing.