I want to get power from my river using tidal flow

[riverpower]

Looking for a little help here. I've been searching micro hydro setups, but most seem to focus on streams with heads. I recently purchased a place on the Sheepscot river in Maine. It has tidal flow, up to 2 ft/sec when the tide is running, and goes to zero at ebb tides. My dock shows 17 ft of water depth at low tide, and probably sits 10-15 feet from shore.

I don't expect my dock will hold a turbine, but I think I've got plenty of flow, here but very low velocity. (If I can make this work, I'd mount the turbine to the rocky shore or river bottom.

I'd like to generate at least partial power for my home. I'd like to hope to get at least 500 watts peak, or preferably up to 2kw peak

My primary question is: what kind of turbine would be best in this environment.  Would I need a venturi type device to get higher velocities? Do any companies make turbines I could use here?

I've not been able to find companies that develop a turbine for this application. Can anyone help?

I'd like to try to purchase whatever components are available, and then do the fabrication/construction of what I cannot purchase.

If I've got enough water power here to harness, using an available technology, then I can research the electrical side of things, and of course the regulations (I have read of a couple of tidal hydro power experiments being worked on at the commercial level to investigate powering cities in the Maine/NH area)

Thanks,

Dave

[willib]

hi riverpower,

question .. are you saying that the tidal drop in your area is over 17 feet?

i have read of underwater turbines that use river currents for power, but that won't help you , i don't think

[riverpower]

Hi,

  Sorry for the confusion.  No, I want the tide current to spin a turbine, not the rise and fall.  The tide does rise and fall around 11 feet, but I'm not sure there is alot of energy available for me from that.

   I think I can get alot of flow.  I could, in theory, use the large area, let's say below my dock, to direct the flow to a turbine.  This area, again in theory, could be as large as 10 ft by 15 ft. While I'm not sure that would be practical, it does give an idea of the amount of flow available.

   Does that clarify things, or just add to the confusion?

Dave

[willib]

there is a company that tried it or is trying it in the east river,NY , sorry dont know the name , these were very large units, not for general public ,

how fast is the water flowing?

[domwild]

Like your other contributor I have seen an Aussie engineer build a large turbine (on TV), it looked like a uni project. The inrushing current turns the turbine and generator, then the impellers on the turbine flip to the other side on the turbine hub when the "outrushing" current is reversing the direction.

The waves are funneled into the turbine chamber a la venturi.

The turbine is anchored offshore (and therefore floats!). Marine hazard - can see you getting into more strife than Flash Gordon fighting the moonlanders!

Another idea is to use the wind rushing through "blowholes" at some stretches on the coast to drive turbines. I am not too sure if there are implementations as those places are tourist attractions. Waves come into natural chambers, compress the air which then escapes through chimneys to spray and amuse the tourists. Can you blast something like that without the police noticing it?? More problems!

[12AX7]

Hello Riverpower

I've been looking 'into' river power for sometime.

Found this site to have the most info.

You may want to take a look at ...

http://www.verdantpower.com/tech/lowimpact.html

Also try googling    Gorlov Helical Turbine.

x7

[pepa]

you can get a lot of energy from the rise and fall of a heavy weight with 11' of tide movement. A cable looped through a pulley that is anchored to the bottom and making a complete circuit by a few raps on a drum type pulley that is suspended over head (on piling) and attached to floating dock. As the dock raises or is lowered with the tide the drum pulley, geared up or down to suit, would turn, giving almost constant torque for a power system. pepa

[whatsnext]

That verdant site claims that the Hudson River site is going to be installed this month so it's odd I can't find any other news about it. Maybe I'm not looking hard enough.

JG

[riverpower]

Thanks for the replies so far.   I think the verdant webpage (East river, NYC) is a little larger :-) than I was looking for.

   I've started researching the Gorlov helical turbine.  Seems like one or two other people are studying this in the Maine area (one is hoping to power a small motel with one).

   Has anyone tried to calculate the power available by the lifting and falling tide?  I'm sure it must be a function of the 'heavy weight' that is being raised or lowered. Also, I have to assume that a dock float would have to be capable of holding up the weight (make it 'float'). If the tide gives me 11 feet of elevation, would it be possible to generate a few kW-hours of electricity in a day?

   I think the helical turbine must be the best choice.  I just have to see if any company is selling these that are a reasonable size.

[srnoth]

"The tide does rise and fall around 11 feet, but I'm not sure there is a lot of energy available for me from that."

Not a lot of energy? That tide difference has enough energy to lift ships weighing many tonnes. Seems to me there is plenty of power available in that rise and fall. Right now I can picture large pieces of Styrofoam in the water with weights on them that somehow pull a rope up and down as the tide rises and falls. This rope then connected to pulleys and gears and voila! You have some sort of power.

I know that might sound kinda absurd but there is definitely power available in that rise and fall. In fact, this 'tidal flow' that you want to harness power from is actually the result of the rise and fall of the tide. I would definitely look into this.

Cheers,

Stephen.

[GaryGary]

Hi,

One way to  make use of the tidal rise and fall is to capture some of the water at high tide in a basin or pond.  Then let that water drive a turbine when the tide drops.  The turbine would be placed near the low tide level.

The stored energy in the basin is:

Stored Energy = (Height of basin)(weight of water in basin)

So, if you had a 10 ft drop from the basin's average depth to the turbine, and your basin was 20 ft by 20 ft by 2 ft deep:

Stored energy = (10ft)(20ft*20ft*2ft)(62 lb/ft^3) = 500K ft-lb

500K ft-lb is about 0.2 KWH

Not a lot -- but, it does grow quickly as you increase the pond size.  If you did a 100 ft by 100 ft by 4 ft deep pond, it comes out about 9.3 KWH.

You would only get part of this, as your turbine might only be about 80% efficient.

Gary

[riverpower]

Thanks for all of your inputs.  I've actually found a guy in Maine who is looking into tidal power, and will make some flow measurements.  I did some rough measurements and found speeds up to 4 ft/sec, so that seems a bit better (since the energy produced is proportional to the cube of the speed).  I'll let you know what I end up deciding.