Rudder Hydropower Generator & Solar Panels

Discussion in 'OnBoard Electronics & Controls' started by Bahama, Jul 9, 2010.

  1. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    Rudders accomplish their work using friction, so why not harness the lost energy and generate some power with it. All day long we must allow a certain amount of friction to run past our rudders, it seems like this is a huge wasted opportunity to gain some of that energy without slowing the boat down.

    For example, cut a hole or holes into the rudder and insert a multiblade turbine designed to capture the moving water; the rudder would have to be designed a bit larger since water is flow through part of it.

    This same principal could also be done in the lower keel area too.

    What is curious to me is if something like this could have a dual purpose as well. A blade can collect energy while sailing and then used as a bow and stern thruster for docking.

    Keeping it from clogging is key, but I think that having it capable of being powered as a thruster would dislodge most anything. It's certainly possible for a motor to be designed as both motor and generator, and so I think this idea has some merit.

    Sailing uses a lot of friction laterally, harnessing just some of it would really be a nice bump in power generation without slowing the boat down--I sure hate seeing all that energy go to waste.

    Also, since I'm talking about power generation, I LOVE solar panels, but I hate how they look. I saw on youtube how to make your own solar panels and it didn't seem all that hard. It made me think that it would be nice to solder my own solar panel into long (several feet long) strips 4" wide and then seal them up completely into a polyurethane resin with rounded edges; then embed this into a nice decorative teak wood so that only the top part of the panel is showing; you could lay several of these on deck so that they can be walked on. Much more stylish than what I see available right now.

    I'm curious as to any comments, critiques, and suggestions.
     
  2. CDK
    Joined: Aug 2007
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    CDK retired engineer

    I think it has none.
    A rudder should have minimal friction and no hole, that would reduce efficiency. A submerged electric motor is asking for trouble because sooner or later the seals will leak due to differential pressure.
    To be effective as a thruster it should at least deliver 400 Watts, that is quite a big lump to attach to a rudder. And as a generator it only works when the rudder has a substantial angle vs the keel.

    Decorative: yes, functional:no.
    Solar cells become inefficient when the temperature rises. Sealed in resin and embedded in teak they generate next to nothing and on a bright summer day will be irreversibly damaged.
     
  3. mark775

    mark775 Guest

    It is not free energy. You stated yourself "make a bigger rudder", create more drag...
     
  4. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    So air cooling would need to be top and bottom like what is done with regular panels; e.g. aluminum bottom (for heat transfer) raised up for air space; teak strips on the sides; and sealed up.

    It would be easy and cheap to experiment with before actually doing it in mass.
     
  5. apex1

    apex1 Guest

    There will be no mass production doing it that way, be sure.

    And you should rethink the PV panel in general!
    On a dock sitter there is plenty of unused space for this installation, on a passagemaker you don´t have that space.

    The "fuel" output of a PV on a sailing vessel is so lean, it is hard to call it sensible by any means. It will have some merits while at anchor and when brought into the right position, but even in perfect conditions it is not much more than you need to keep your starter battery alive. It does never fill a house bank.

    To the rudder idea I have to concur with CDK and Mark, don´t waste another thought on that.

    Regards
    Richard
     
  6. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Even free energy isn't always what one wants Mark.

    The solar collector is working overtime here, the panels supply current for the pump and electronics, the solar boiler does what the name implies: It boils and nobody needs hot water.
    So I opened the bathroom radiator and opened the window to get rid of some "free energy".
    There is no escape, if I shut down the system there will be steam within minutes, then the glass shatters and the safety valve starts spilling anti-freeze in the garden.

    Like always, the problem is storage.
     
  7. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    I've been thinking about both of these lately; for the rudder idea, what CDK said still doesn't make math sense to me unless a rubber works primarily by lift rather than friction; speaking totally from a friction standpoint, I mentioned that they rudder would have to be a bit larger, but only because the holes and blades offer less friction than a flat surface, so the larger rudder is only compensating for less friction just to bring the total friction up to what it was in the first place; so there would not be more friction, it would be the same... and so whatever rate the blades turn, that would be free energy that was otherwise lost to friction. That was my original point. The main reason that I mentioned occassionally using the blades as a motor was primarily to be used as a way to free itself from anygunk that held onto it--the idea being, if it got clogged a bit, it could free itself for many things. When I mentioned using the turbo thruster it was mainly to express what I was talking about (e.g. turbo thrustors don't clog all the time either... they do, but not all the time). I concur that they would make a lousy thruster on the rudder. If lift is the primary factor then this is all blone away as an idea for the rudder, but not for the lower hull area.

    Also, since we're talking about friction, what is wrong with having something flare out from the hull toward the prop to reduce prop friction? Truckers use this principal with that aerodynamic wind guard that they put on top of their cabs. Why not direct the flow of water around the props completely or partially while the prop is idle? There would be many simple ways to do it.

    And regarding the solar panel idea, I've been doing some looking around and it seems that you could embed each of the mono or plycrystalline cells in epoxy resin to waterproof them, place them on top of aluminum for heat transfer, lay teak wood strips alone the sides for a nice look, and then lay this out as a raised deck so that air and water can flow freely underneath to provide cooling; this air space also keeps problems from occuring below the teak deck and the watertight deck below it.

    It could be made with a nice artistic look, and will pick up as much sun as any other normal panels do because a boat is constantly moving about. You could lay it out as a long strip that outlines the perimeter of the boat. It would look good and provide a lot of solar cells out there. It's just one very long and skinny solar panel, well 2, one for each side.
     
  8. Bglad
    Joined: May 2010
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    Bglad Senior Member

    Forget about all the stuff above and design PV sail plan:)
     
  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Rudders don't work on friction at all. They deflect water flow and creat lateral resistance. Any hole in a foil will degrade performance and create enourmous drag. Study basic hydrodynamics. It is not too complicated.
     
  10. apex1

    apex1 Guest

    Think again about your rudder idea.

    You need a undisturbed flow to your prop to produce a propulsion force and not foam.
    The same is valid for your rudder, the better the laminar flow, the less drag. Every vortex is counterproductive and has to be avoided.
    When under motor, your rudder angle is just straight zero at, say 90% of the time.*
    Under sail that will be different of course, but we try to sail with the least angle of attack to avoid drag.
    Now you try to get some "fuel" out of this vortex. That would require a permanent vortex which is not welcome. You would gain less than you loose.
    Say you gain 1kW of El. power but your drag equals to 2 or 3kW.
    The same principle you have when dragging a "tow generator".

    *watch your autopilot, it will act 2 to 4 times in a minute for about 1 second each time.

    I can see where you want to go with your PV panels. Having a stripe on the hull sounds nice but you wou´nt get much bang for the buck.
    Covering the deck sounds much less attractive. Walking barefoot on it, will be impossible, walking with shoes on it will make it soon blind.
    The wiring will be a nightmare, cost - benefit calculation too.
    Installing it above deck level (as you mentioned), makes the most vulnerable area inaccessible, all through hull, through deck points have to remain permanently accessible.

    Regards
    Richard
     
  11. FAST FRED
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    FAST FRED Senior Member

    The premise is wrong , a rudder deflection creates pressure on the bow that caused the bow to move.

    The better the "lift" the less rudder deflection is required to cause steering , so the boat is faster.

    Unless a boat is in a fixed position a small fully loaded gas or diesel DC noisemaker is still the best (in terms of charge quality and rapidity) for most cruisers.

    Only thing better is less DC demands.

    FF
     
  12. Bahama
    Joined: Jun 2010
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    Bahama Junior Member

    I don't find myself agreeing with you on this. The deflection is caused by friction. There are only two forces at work in the water, lift and friction. I has to be one or the other. Friction on the rudder, causes lateral force on the boat, and because it's located in the back, that's a lever, giving a rudder more leverage. Leverage is what allows the rudder to be so small, and placing it directly behind the prop allows it to grab friction from the water flowing past, including all that energy from the prop to propel the boat. That's also why an offset rudder that leads forward a bit is more efficient, because its able to get more than half of the energy from the prop rather than simply half as a normal rudder would.
     
  13. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The proper word is drag, not friction. Any object moving through a liquid causes drag in the direction of travel if it is symmetrical. If it is not, i.e. an angled rudder, there is also a force perpendicular to the direction of travel.

    Draw a box in which the rudder is a diagonal. Two adjacent sides show the ratio of forces acting on the rudder.
     
  14. DaveJ
    Joined: Jun 2009
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    DaveJ Senior Member

    Bahama: there are two types of fiction, parasitic and induced (they are also know under defferent names, but in reallity they amount to the same) and all friction is refered to as drag.
    Parasitic drag is the force required to push any object through the water for a particular speed, a symmetrical rudder will require less force to push it through than lets say a broom stick even though from frontal view they will have the same thickness. Because the rudder is more streamlined than the broom stick, the rudder will upset the state of rest water less than the broom stick. The water is moved apart but comes back to the same spot, and is has moved an equal amount both sides and at an easier rate than what the broom stick will do.

    Induced drag is added on top of parasitic drag and is cause when the rudder is angled off its streamline position, as its angle of attack is increased, it causes a side force which is called lift but in doing so causes increase in drag, this drag is a function of the foil shape, angle of attack and speed through the water. Same as before the water is pushed apart but this time it will not return back to its previous position because the water on one side has to move further that the water on the otherside, its this upsetting of the water that causes the induced drag.
    The angle of attack can be increase until a particular angle to where the water accually seperates from the rudder and causes cavitation. At this point the rudder has lost nearlly all of its lifting fource but maintains all of its drag plus more from the cavitation. Never want to be at this state.

    On sail boats, good sailors will balance up their sails to take loads off the rudder which allows the rudder to reduce it angle of attack bringing it back to a streamline position, thus reducing drag.

    Hope this helps you to understand whats going on with your rudder.
     

  15. Bahama
    Joined: Jun 2010
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    Bahama Junior Member


    Thanks, it does help. I like trying to figure out how to grab energy that is often lost to friction (in this case drag)... it's just my way. For example, all these hybrid cars are grabbing elecricity from the starts and stops, but I don't see them going after the up and down motions as the vehicle bounces up and down. I've seen some shock absorbers try to do this by using a magnet and coil to generate the current from the movement--but this is so dumb, they are simply grabbing the basic linear movment NOT capturing the real power, which is the actual mass of the car associated with the up and down movement. Were into boats here so I won't go further, but my quest to capture power lead me to think of all the friction (drag) that is associated with sailing--there is a lot of drag this is required to make sailing work... if we're able to capture any of this without losing it in other places due to eddies, or lost momentum, etc., then that's free energy. So I'm just keeping my eyes open for it.

    On this same thought, I find it curious to be able to lower a water turbine at night while moored to capture any current movement.

    And finally, as a side note, I have drawn up some sketches to capture energy from people who are walking on the streets or alone skyway systems. It's similar to what you see in this bed design, and the energy from walking is capture via hydraulics. I thought of a way to store the energy from hundreds of these walkway collectors so that they can collectively turn a turbine efficiently. I have 4 or 8 groups of these collectors that capture the energy by building up pressure, and then each of these groups are fired off at a turbine one after the other, similar to the way that pistons in an engine work. so while others are storing up energy, a couple of them are finally releasing their energy. I just through that out there because I think this same concept would work with those devices that try to capture the wave energy from tide waves. It's wrong to simply capture the physical movement... this is only a fraction of the real energy, which is the mass with the movement. Using hydraulics is an efficient way to capture some of that mass/movement rather than simply capturing movement.
     
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