Bi Directional Water Driven Generator

Interesting idea. Would there be a need to turn the impellers to catch the outgoing tide? I to am interested from a intellectual stand point of can it be done feasibly.

The concept is pretty simple. Think of a wind speed guage or a childs pinwheel. On one side the flowing water is caught and imposes a force on the rotating hub and on the other side the water slips by allowing the hub to turn. it doesn't matter what direction the water is flowing, the hub always turns in the same direction.

The water flow has quite a large amount of force behind it, but regretably it moves fairly slowly. I am trying to make a mechanism that is as simple as possible. I could add gears or pullys to change some of the torque into additional speed, but I would be sacrificing some of the energy in the form of friction and increasing the amount of maintenance for the system.

The real challenge is going to be designing the system to change the current flow into as high RPM as possible on the hub. I guess we will see how effective we are.

-Doug

Perhaps look at verticle axis wind turbine design; lay it over, sink it and you have horizontal axis water turbine.

This means you can have one long impeller that goes all the way across the harbour opening (or multiple impellors coulped with universal joints), only need one gearbox to get your speed/torque optimised for power generator, has a low profile but has alot of water moving over it.

I guess there is a question about the turbine design to get good work out of both tidal flow directions...

<interesting opportunity.>?

I should reword: " You are sitting on a gold mine--Use it"

Get an Axial flow Propeller Pump from an asset management auction.

Get the Axial pump installed at bottom of incoming channel.

Make a 90 degree bevel gear coupling +propeller Shaft to take the Torque up to a barge-mounted(keep dry) floating Generator set .

Restrict the incoming tide through this Axial Flow Propeller--as much as possible.

See what RPM'S/Power you can get(short-time rating).

Get an electronic wizard to optimize Power generation FOR as long/as many KW-possible during the incoming/outgoing tIdes as DC into an accumulator battery .

Use accumulated Battery Power through Inverter--and plan the big time investment for a bigger industrialized version power plant to sell to Supply Company Grid

Reverse Flow?

That will be taken care of by the Electronic Circuit.Axial flow output shaft will rotate reverse--GENSET will not mind!

well, you can only tap a tide that has a long term flow rate where a large volum of water comes in and goes out. A tide on a dock that rises and falls 4 feet cannot be tapped by these turbines.

A rising tide can be tapped by a large float. Say a boat 10 feet wide and 4 feet deep and 30 feet long weighing 1000 tons. That going up 4 feet in ~7 hours(25,200 seconds) and down 4 feet in the next ~7 hours.

2,000,000 pounds x 4 feet = 8,000,000 foot pounds or ~300 foot pounds per second or about 1/2 horsepower. Now a large 20 acre lagoon with a choke point in which you can place a dam is where the real power lies.

20 acres - 804,000 square feet x 4 feet = 3.2 million cubic feet x 62.4 = 200,000,000 foot pounds/25,200 = 7900 HP, so there is big power in large volumetric flows if you can harness them.

Tides have been notoriously hard to harness effectively.

Canada has notoriously high tides in places. like 28ft ?

If you had a 100 ft length of 72" dia, pipe laid parallel to the 2 knot tide flow, and you fitted a large flap valve which closed automatically every four seconds, stopping the 100 ft column of water dead,

Would that provide enough power to run a small generator, say 10kw?

It would probably enter the Guinness book of records as being the largest Montgolfier ram in the world.

Of course, as a tidal pump it could be designed as a double action and double ended to accommodate reverse flow. thus initialising a completely new branch to the alternative energy industry. I calculate there would be 28,000 ft pounds available.

High pressure water is an attractive prime mover, and could be easily used ashore.

GF

Have a look at "Tidal power generation" or "Wave power generation"

Modify the above propeller pump to allow for "Variable pitch" on the rotor blades, this will also help you control the max speed as the pitch could be less aggressive at higher speeds.

also reversing the pitch will fix your problem with reverse flow

Some of the tidal/wave power turbines run a impeller that will flop back and forth with the direction of the flow of air/water so there is no problem with trying to devise a way to automatically move the impeller blades.

The University of Victoria in BC is at this time doing exactly that kind of project study. If you are in the BC west coast area contact them.

As for impeller my first inclination is to use a savornius rotor style. Many years ago I worked at calibrating current meters for Ontario Hydro as part of their pre-construction study for their nuclear power stations. They wanted to understand the underwater circulation flow where they planned the intake and outflow of cooling water. All these current meters had a savornius style rotors because it could detect and rotate with even slight current movement. It follows you can get maximu power extraction. Plus these are not direction sensitive. Infow and outflow direction of tidal water is not always 180 degrees apart.

People are believing this fudgy question? Amazing.

You need bi directional water driven generator.

Bi directional water driven generator is not available in my knowledge, but I can understand your problem you want to use backward and forward kinetic energy of tide by using simple rotor. This is not possible. I am also doing some of my work, personally in this direction. Variable lows speed generator with special mechanical attachment can solve bi directional problem. But you will loose energy due to dirction change. I have also the solution of that. If you need assistance in this direction you may contact.

ritooza@yahoo.com

K. K. Verma

Hi Kumar.

Your statment is not true, look at what the French did in the 1970s at a location on a river mouth where there was a huge tidal difference. The french model shows that you can extract huge amounts of energy in both directions of flow!

Here in the UK we are designing a much larger similar scheme on our river severn. The severn estury has a tidal difference of 12 meters, twice a day there is a huge bore going up the river, so the idea is to build a sea barrier accross the estury ( 17km long), to capture this tidal difference. Into this barrier will be built several large radial turbines coupled to generators, it has been calculated that the power produced will supply enough electricity to several southern counties!

This type of power generation has been tried out on a small scale in parts of Norway with great success.

Also, this type of power generation is not without it's environmental impact, larger, wider esturies like the severn will have a huge impact on wildlife in the area, such as it's salt marshes which are home to several thousand wading birds and water fowl?

Spencer.

What about the possibility of using a concept such as a "weather vane" to direct the blades of the water turbine (or whatever) always into the flow direction.

harnessing the speed of the flow wouldn't require any blocking of watercourse.

Perhaps a modified paddle wheel arrangement under a dock, width of the dock would be economical and unimpeded by regulations. i think you could get some real torque from there. no problem about gearing up, use a chain & sprocket or belt & sheaves for very high efficiancy. gears lose much more power.

fancy gears and impellers not neccesary, a long shaft can bring the torque to a conveinient place [200' of 2'' steel pipe with good bearing mounts] = cheap shaft.

i'm kinda jelous of the natural resource :) cool idea

the less you interfere with the flow the less power you get. The most efficient tidal power stations wait until near high tide and then allow the tide to enter an area. At the start you get max gradient. As it fills and the tide goes out this falls. Then you close it off just as high tide is reached and the basin is filled. Then you wait for near low tide and allow egress.

Since the inrush volume is limited to the basin the gradient will drop faster than on egress to the open sea. The basin size and tides are known so the optimum can be calculated.

This is not base load. it has a number of peaks and declines, but can be used to shut off fuel using generators for a time.

paddle wheels that dip into the tide as it goes in/out capture only a small fraction of the energy.

Marine navigation complicates the use in some areas. In others not. There are many tidal power operations that block the flow to maximize power this way

Hi all,

first, i'm not sure Drobeston's idea that the hub will spin the same direction, whatever the flow direction, is right. anybody can check it with a common fan. however, the regular incoming and outgoing of such a tremendous volume of water is an opportunity that any undertaker should insist to exploit. the whole setup should be able to swing 180.o horizontally around a vertical pivot. second, the very existence of a marina implies that the region is inhabited and so it is out of question to think of building a dam or any structure to control the flow of water. one of the safe options available is the use of horizontal or near-horizontal shaft reaction turbine and chose from AC or DC, which type of current to generate. rotation transmission can be through shaft with universal joints or beveled gears, chains and sprockets, or any other means

The hub did spin in the same direction whatever the flow direction in the current meters I serviced. Simply scaling up the instrument would derive considerable force (energy) Did yo usee my original comment that these current meters used a vertical shaft savornius rotor design. Somebody much smarter than me evidently figured out it was a good configuration. Looks to me it is a good starting point. With a maximum current of about 2 knots water velicity is not so fast as to cause a problem. Its not liek a wind mill.

The Savonius rotor looks like an easy to build and solid design. We have a prototype that is similar to this that we are looking to test. I may tweak it to be closer to the Savonius design.

Does anyone have a web site that compares rotor designs of this style. I am looking for a way to compare the pros and cons of different rotor designs. Specificly I am trying to figure out the efficiency of the design and the output torque/RPM will be on the rotor for different styles.

Thanks,

Doug

Good day,

Using tidal currents has always interested me. I saw a fantastic show called ECO-Tech where a college was designing gulf stream watermills. Many considerations were used for their design including temperature, sea life, current deviation, storms, weather patterns. Since your project is a bit smaller I would research this college and possible ask them some questions. I know they were projecting implementation in 2016 and was planned for the energy hungry air conditioners in Florida. Their goal was to fulfill 33% of Florida's demand for power. I hope this helps. I may be able to offer some design suggestions as I work at a Solidworks reseller that has a plethora of design knowledge and many diverse clientele. Good luck and keep me posted.

Hi mainmacman.

Harnessing the Gulf stream will endanger the environment!

You cannot take energy from a natural system and expect the same amount of flow and heat energy to carry on further north?

For example; if the gulf stream contains xxxxx amount of energy at it's southern end, and you extract xx amount near Florida, then the energy in the gulf stream after passing through the turbines will be xxxxx - xx = xxx!

I have witnessed vast areas of land that have changed their environment for the worst because man has extracted natural energy that kept the land in a state of balance!!!?

Wind, wave and tidal energy extraction creates havoc with the environment, the only natural energy source that can be utilised without upsetting this natural balance is Solar energy!

Spencer.

Spencer, you are right that every use of energy for human purposes has consequences. The question is one of scale and impact. The fact is that even solar PV has an envirionemental impact. Light that would have been converted to heat or reflected into space is being converted to electricity. This electricity is being used in other locations and that generates heat. This has an impact, it is just significantly smaller than the impact of burning fossil fuels.

Harnessing energy from the gulf stream has an impact also, but it is trivially small. Think of it as a river that is roughly 20 miles wide, 3000 to 5000 ft deep and flowing at a rate of 2.5 knots. Some of the math guys should be able to calc the energy in that. Anything we harvest from this would be trivially small compared to the total flow of the gulf stream itself. The question then becomes what is the negative impact of taking that energy out of the gulf stream compared to the positive impact of replacing the dirtier and finite fossil fuels we currently use for generating energy. The finance guys always seem to want to know how much it will cost also.

None of these problems are simple and there isn't one simple solution. I am a huge proponent of solar energy, but sometime there are better solutions we should think of.

-Doug

We are actually right off the gulf stream in the Bahamas. Currently we are prototyping some designs and will be testing them in the water soon. Our goal is to measure what kind of RPMs and torque we can generate between the different designs. Right now ideas for different impeller or turbine designs would be the biggest help to us. Links to examples would be great.

To give the engineers out there something to work with here are some numbers about our location.

1. We are in the Bahamas so our tides are very small 2-3ft

2. The harbor area that gets filled/drained by the tides is roughly 10 sqr miles and about 5 ft deep at high tide.

3. Down one side of the harbor, along the main island area is a channel that was dredged to roughly 20 ft deep and about 200 ft wide. This is where the water flows in and out during the day.

4. Our Marina is right along side that channel. Peak water flow by the marina 4 times a day is about 2 knots. During storms and large tides this can get higher.

5. Water depth in the marina is between 12 and 16 ft under the docks.

Some design constraints;

1. The system must fit completely under the docks and not impede the docks use by boats. There can also be no ugly mechanisms sticking out of the water or hanging off the docks.

2. The design for the underwater portion of this must be simple and low maintenance. It can't rely on constant maintenance by a sophisticated technician. Periodic maintenance and upkeep is obviously going to be needed, but we need to keep it to a minimum.

3. Low envirionmental impact. High speed blades chopping up and spitting out fish will not make me or the marina guests happy.

4. Resilient to major storm surges and the periodic thrust put out by the props on 100+ ft boats.

I am more than happy to share any more info that could get ideas flowing. Let me know what you think.

-Doug

Note - As for the guest entry above asking if anyone believes this question. This is a real project that we are working on now. It is sad the amount of naysayers that are in the world. We would be a lot further along if people were just willing to try things.

Dear Sir please look at these web sites as our company has developed a hydrogen system that would fit the scenerio you are talking about.

www.camelwatersystems.5u.com

www.whisperglide.5u.com

Hi Guest.

Very interesting thank you, but have these systems been constructed and tried over many years?

I repeat, you cannot take away from the environment without upsetting the natural balance!!!

Also, if the system does not need refueling, then you have created perpetual motion?

My advice to you is to read Newtons laws, you will soon find out that the perpetual motion motor is so much pie in the sky!

Spencer.

You might try thinking out side the box just a little and dispense with most of the moving parts which are under water,

Why not use the hydraulic energy of a moving body of water and bring it "land side"

Where you can use it for any purpose you like?

"Mongolfier" invented a RAM pump, the principle of which you might consider?

You could lay a concrete pipe in line with the tidal flow and and fit a Mongufier type pump at each end.

This will give you several hundred PSI while the tide flows.

The efficiency of such a system will not exceed single digits but who cares?

just make it big, after all, 40 tons of water moving at 2 knots will give you plenty of foot pounds even at 5%.

The high pressure water can drive all sorts of devices even an electric water pump used as an induction generator.?

Easy maintenance. just one moving part at each end of the concrete play pipe.

GF

Hi, Google the Gorlov turbine, it is omnidirectional - the guy won the Edison award a couple of years ago. The latest/greatest in hydropower. Also, Fieldstone Energy can harness wave energy. Good luck.

Thanks

The Gorlov Turbine design is just about perfect for what we are doing. It also fits in nicely with my origional thoughts on the project.

I found this link that has a pretty good article on the design of the turbine and its uses.

http://www.commondreams.org/headlines01/0517-05.htm

Thanks for the input.

-Doug

Havings started about 15 hydro-electric plants in the early 1980's and followed the technology. Low-head is no power and is not economical. Three foot high, half mile long dams could not justify putting in turbines.

Thus a bladder system driving the pressurized liquid thru a high efficiency turbine into a high energy recovery draft tube arrangement. The turbine is driving a generator with the power plant itself at the bottom of the bay. The reason is a liquid pressure drops about 2 psi per foot (if I remember right) and velocity losses are also a problem, which reduces potential power and electricity doesn't have significant loss versus distance.

So anchor a bladder to the bottom of the bay, have the wave action and tide levels create pressure on the bladder, run the pressurized fluid thru a turbine into another bladder in a dry caisson. As mentioned in earlier posts maximum power would be generated at high tide, the bladder versus turbine capacity would determine run time.

To refill the bladder (at low tide) also use the pump-turbine, run the generator as a motor using a reversing contactor.

A savvy structural engineer may be able to re-inforce the pier supports so it could become a dry caisson for the bladder or for a low-tide level reservoir. The length of the pier determines stored capacity, and only operate the turbine at peak differential water levels. The action will be similar to canal locks.

The "Bay of Fundy" in Canada has a reversible flow turbine to generate electricity from tidal flows of 18 meters if I remember right.

Corona cameraman wrote: Low-head is no power and is not economical. Three foot high, half mile long dams could not justify putting in turbines.

REPLY: perhaps not, if you only consider turbines for power generation. But there have been many instances of low head waterwheel (undershot) installations powering various mills.

"run of the stream" designs that do not dam, impound, or impede the flow of the stream can be successful. Maybe these old time waterwheel driven mills got built becaue no one told the builder it wasn't cost effective. If the only flowing water is low head then that's what you use.

Hey guys,

So I am not an Engineer or anything special like that, nor do I know a whole lot about electrical power generation. I read through this entire thread and must say that I have been thinking of ideas of the same system utilizing a rivers edge. If you took a 20' drop and ran a 10 foot impeller off the power of the river then you could drive a electical generator from the force of the river and would have the perpetual motion of the river for consistancy of power generation. the river I am looking at has a mean flow of 24400 cfs. Anyone have any ideas on what type of power generation I could produce with that amount of flow? I would love to talk to someone interested in helping email: casper@newworldreps.com

Also on a side note thought to go along with the thread. If you were to use the system I just stated above using a 20ft tall by 10ft long impeller and having it center on a curve semi slanted to the flow then you could harness the energy coming in and out of the harbor and the impeller would not change direction of rotation. Though you may get a little bit of reverse directional resistance. Perhaps using the method stated you could figure out a way to rotate the reverse directional fans into a flat plane to reduce the back flow resistance.