Recuperation of energy while sailing

Discussion in 'Propulsion' started by lausl, Oct 4, 2012.

  1. lausl
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    lausl carpe diem yacht design

    Is there anybody out there who knows about the efficiency of using the prop/shaft to extract energy for the trolling prop while sailing. The ship is
    sailing 5-6 hrs a day at say 8 knots,
    Best regards,
    Klaus
     
  2. FAST FRED
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    FAST FRED Senior Member

    "Is there anybody out there who knows about the efficiency of using the prop/shaft to extract energy for the trolling prop while sailing."

    The efficiency of free wheeling a shaft would depend on how close it comes to having low drag. Roller bearings and lipped seal would help.

    When loaded to produce energy the drag goes WAY up as a prop requires power to create the energy.

    AS a minimum tow a pail or flat board with the same diameter as your prop to see the speed loss due to drag.

    With a multi blades prop (4 or 5 not 2 ) the towed pail should be at least 50% larger to simulate the drag.

    There are special alternators that are built to operate a very low RPM , perhaps 200-300 RPM charging underway.

    Yes it works , but you may not like the cruising speed loss , however once you get to hull speed , if the wind is strong enough , no speed loss will be noticed.
     
  3. philSweet
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    philSweet Senior Member

    Don't waste your time. Lock the shaft (or feather or fold the prop) and save the wear and tear. If you must try this, use a stand alone setup that you can haul in. A prop wasn't meant to be a turbine. Solar panels and little generators actually work. If you want to be more efficient, install a folding/feathering prop and just sail faster. The time you save will lower your maintenance cost enough to buy 100 times the amount of fuel you would save with the regen system.
     
  4. bartnordwest
    Joined: Jun 2013
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    bartnordwest Junior Member

    i am looking for the same thing ,what i know is that they sell torpedolike things that drag behind the boat with a generator in them,and further the ideal would be an adjustable prop,but tose are not made that small as we want them
    keep searching!
     
  5. alan white
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    alan white Senior Member

    Use of a prop to generate electricity is viable or not depending on many conditions. To begin with, it matters what amount of stored energy is required.
    Ideally, the conditions during generation would allow the boat to travel at the same speed as when not generating, meaning at or near hull speed. Once at hull speed, the boat is then using up the extra energy available that would otherwise be wasted trying to push the boat out of its own wave train.
    However, usually the boat is not going that fast. That means most of the time you'll be robbing precious energy from the wind and speed will be comprimised a bit, which is cumulative over time and distance.
    I think the use of a wind turbine would be far better because it will have (if placed properly) no impact on sailing speed. It can work at the dock if need be whereas a trailing or prop-driven device would usually only work when sailing (sometimes mooring in a river or current will turn a prop).
    That said, an offshore boat sailing in heavier conditions for days on end could do well to store electrical prop energy for various uses IF it can be done practically. All depends on how you sail.
    I gather it isn't a big boat if you intend to use a troller. And there is a handiness to being able to motor a boat for short distances like through a crowded harbor when there's no wind or to supplement sail power in bad (or windless) conditions or evading a lee shore or a storm.
    The bigger problem is battery storage. You need to calculate how much storage in amp hours is required. Batteries are heavy and take up room. Whether wind or prop power, you need enough battery storage to make the system pay for itself.
    Again, wind power is maybe a better choice. Especially with a following wind. These units already exist though you may only need a small turbine. And the fact that they can work on a mooring is really a big plus since most small sailboats are sitting most of the time.
     
  6. FAST FRED
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    FAST FRED Senior Member

    Wind power is great ,

    however most folks spend 90% of a cruise in a harbor ,
    and most harbors are selected to be protected (from wind, and the seas it generates).

    In harbor you also may get static from other anchored boats as many air fans are quite noisy.
     
  7. michael pierzga
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    michael pierzga Senior Member

    A free wheeling prop shaft ,with an alternator belted off it, is an effective battery charger. It also charges when you are motoring.

    Ive sailed several motorsailors built in the Netherlands by Jongert who used this system.

    A low friction oil lubricated shaft was used.

    Some boats even has a hydrualic pump belted off the free wheeling or driven shaft to supply hydralic pressure for the autopiolt when the shaft was free wheeling

    I like the setup and would definately use it again.

    The extra alternator on the rear end of the engine frees up precious space on the front end of the main engine.

    Perhaps 15 to 30 amps of dc available when sailing. The boatspeed loss is only noticable in light wind...when sailing fully powered it wasnt an issue
     
  8. bartnordwest
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    bartnordwest Junior Member

    i am talking compressed aire

    thank you for giving it a thougt ,my boat is not very small;30 ton,15 meter,and i am trying to cut down on emissions ,inspired by the airstart systems on oldfashioned shipsengines ,so much more reliable than batteries,and no chemicals whatsoever! so i think that what would start a 1000hp,would be enough to give me propulsion for half an hour or so ,and i,m willing to give up half of my living space,i m thinking 4airbottles of 6meter long and about70cm diameter ,30bar is the max pressure on these systems.
    so what i am trying to find is small 30barcompressors for a trolling prop,a windmill,or even pedalling (i ve seen handpumps,it took the man 3/4hour to pump 16bar and start a 80hp deutz)
    the other thing is the prop,how to combine trolling,not trolling,and propulsion?
    and then an airmotor,or just use a adapted fuelengine and run it on aire?
    anyway this is a long term project and i realize that most people find it silly to care for global warming
     
  9. FAST FRED
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    FAST FRED Senior Member

    i realize that most people find it silly to care for global warming


    True a HOAX is a HOAX and after 16 years with NO global warming , most folks have learned the truth.
     
  10. powerabout
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    powerabout Senior Member

    maybe or maybe not BUT the price of fuel keeps going up
    I have sailed on 2 cats lately that can run the aircon when sailing of regen
    ( when the wind blows)
     
  11. Petros
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    Petros Senior Member

    when you put a turbine in the water or a windmill in the air you increase the drag of the boat, whether sailing or motoring, that drag reduces your speed and makes it take longer to get to your destination. There will be a "cost" to using something that draws power from your forward motion, reducing our overall efficiency.

    Solar panels on the other hand do not detract from your speed, and would result in less impact on efficiency if they are installed so not to increase the air drag over the hull, and presuming they do not add much weight. I have wondered if there was a way to treat or interweave into the sail fabric to make them act like solar panels, this way every time your sails are up you are also capturing solar power along with the power of the wind.
     
  12. powerabout
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    powerabout Senior Member

    all true but can you get 4-5KW output on a 60' boat to put back the battery power you used when you ran the aircon all night on the batterys
     

  13. alan white
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    alan white Senior Member

    With such a small requirement I think a small wind turbine would still be a better choice than a prop driven generator. This has been the sailor's choice for decades and no technology has replaced it yet. I personally would prefer the better access for repair (assuming a typical sailboat layout). The connection of turbine to generator is direct. No gears or extra shafts to turn.
    Also can be purchased assembled and ready to go. Probably far cheaper considering labor especially.
     
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