Hydroectricity from the sea

I saw something on the boob tube last year showing something similar to this being developed in Europe for use in the English channel...

Cheers

It seems like your hydro head would be very low, and power would be intermittent as the rising and falling water level at the discharge would cause generation to be intermittent, at best.

There has been an enormous amount of research done into using ocean waves as a source of power. See, for example:Wave Power (Wikipedia)

One of my favorites is the Islay LIMPET project, a 0.5 MW plant built by WaveGen on the Isle of Islay.LIMPET Publishable Report. One nice thing about LIMPET is that all the equipment is onshore, and relatively easy to maintain.

There are also small or pilot projects planned in India and Germany.

Hydroelectric power is successful because of the high pressures. You will only ever get tiny pressures and hence power from the proposed system. If the turbine is at the bottom of the tank then it will not be venting to atmosphere and will lose more of it's already tiny pressure battling against the pressure of the external seawater.

Suggest you employ somebody to do some serious calculations for you as this just isn't going to provide much energy.

There are many inventions to harness sea power. See freeenergynews.com to survey the state of the art. Check the categories on the left column.

The Electric Power Research Institute (EPRI) has a significant amount of information on studies and test programs for both wave-generated and tidal generated power, including cost analysis. Quite informative. Unfortunately, I do not have a link available right now...

George

Try Calculating Flow And Necessary Storage In Order To Get A Good Flow rate for an extended period of time.

Just guessing a 5 Mw turbine would need say 10-15 cfs each, were talking maybe 5 feet of head in the south or 20 in the north.

a cfs is if i recall 550 gpm times 15 cfs, cubic feet per second or approx, 8,000 gps, gallons per second. ok, if you wanted to make power for 3 hours, for peek demand, you would use for one generator 8k x 10 = 80,000 for 10 seconds x 6 = 480,000 gallons for a minute x 60 = 28,800,000 gallons per hour x 3 hours or 86,400,000 of storage. now, you know the tanks on the hills in the western united states there allot of times 1 million gallons, if its an elevated tower tank in the midwest there only 2-300,000 gallons. at these midwest tower standpipe tank sizes you would need approx. 75-80 tanks for each generator, or 28 one million gallon tanks. made out of cement, you can build each million gallon tank for $400,000.00 dollars or $11,000,000.00, eleven million dollars for the tanks, plus site prep, roads, pipe, labor, generators, and one way valves, that are already designed, by george.

im sure i have made some mistakes on flows, or costs, but the costs are prohibitive using tanks, if you could use tidal pools in the north, then you have a good idea that has been, and is now being worked on now.

Your numbers are off by a few orders of magnitude:

To get power in watts, multiply:

Watts = (head in feet) x (flow in GPM) x 0.18 x (turbine efficiency)

30% or 0.3 is a good ballpark number to use for turbine efficiency.
Thus, to get 5 MW of power from a 5 foot head, you'll need:

5 x 10⁶/(5 * 0.18 * 0.3) ≈ 18 x 10⁶ or 18 million gallons per minute of flow.

Which equates to about 41,000 cubic ft./s (449 GPM ~ 1 CFS).

So its even more uneconomical than you thought :-)

"...about 41,000 cubic ft./s..."

That's almost an acre-foot per second, for those who are more used to dealing with drinking water, by the way... Those tanks will be a LOT bigger than you'll probably want!

Hey Environman ... Nice tag line!

Of course a head of 5ft would be uneconomic but the tanks would provide a head of around 5m or 15ft in typical sea conditions and rise up to around 25m or 75ft in the very roughest seas.

Waves provide a very variable source of energy which can vary between around 40kw per metre in typical seas but rise up to 1000kw per metre in very rough seas. There is also a lot of variation in any sequence of waves.

Most suggested wave power devices have little or no storage and simply capture a proportion of the energy of the passing wave while allowing big waves to pass over the top with little energy extracted.

By using storage tanks, the maximum amount of energy can be captured and stored from the biggest waves but the power output can still be controlled by adjustment to the flow rate. The size of the head of water will vary much less than the sizes of the incoming waves and so the power output will be smoothed.

The costs of the tanks could be reduced with the use of plastics.

A lot of information can be found by searching-

HYDRO WORKSHOP PROCEEDINGS

reports put out by DOE. I have found they very interesting.

Regards JD.

You will find lots of ocean power inventions, some that are in use, at freeenergynews.com. A nice thing about a lot of them is that there is little or no land footprint. They are mostly underwater, so wouldn't be seen from shore. There is work underway, at least studies, to harness the tidal power of the Bay of Fundy. A huge potential power source.

Hi GEORGEB

I have thought along the same lines but with a bit of reverse logic? The object being to have a system that creates an environment with the minimum of moving parts, or no moving parts at all, and power being available on demand. Power on demand being the hard part? The ocean offers a number energy sources, tidal variation, waves, sea current and thermal differences. The reverse logic is, systems relying on tidal variation to create a head pressure, can be reversed and waves and currents used to reduce an area such as a tank or inland area below the normal sea level, then that area can be refilled on demand? Or so the theory goes? Waves and current can be utilised in a venturi system that has no moving parts to evacuate the potential area. This would be a modular system with venturi pumps spread over a vary large area. Just some of my thoughts.

Regards JD.

There is a scheme under discussion at the moment to harness tidal energy in the River Severn estuary, which has one of the highest fluctuations in level anywhere on the globe. Check this:

http://uk.ask.com/web?qsrc=167&o=312&l=dir&siteid=&q=Severn+tidal+barrage&search=&dm=ctry

Hi PWSlack,

The Severn tidal barrage has been on and off for about the last thirty years, seems the politicians cant make there minds up, cost too much, same old story? The Bristol channel is my old stamping ground, grow up there at a place called Barry, a little sea side resort out side Cardiff, a place where all the welsh coal miners came during the summer.

Regards JD.

Producing electricity has been published in ASME journals. Floating water turbines are lowered in deep sea where steady water currents have been studied. These causes the water turbines to rotate and run generator to produce electricity. The problem is on material that would resist harsh conditions in the deep sea.

Good luck