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#11
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Perpetuated Motion
Electric propulsion for boats: A century-old technology may just be the wave of the future LINK: http://www.cruisingworld.com/article...ID=396&catID=0 " Advocates for diesel-electric propulsion list among its virtues that it's clean, quiet, efficient, and requires very little maintenance. Another advantage frequently noted in connection with the STI system is the ability to make electricity--to "regenerate"--when the boat is under sail." "While internal-combustion engines are typically described by their horsepower rating, STI's motors are named for the torque they develop. An ST 37 puts out 37 foot-pounds of torque or 6 horsepower; Tether recommends using it on monohulls up to 32 feet and 10 tons or to replace diesel engines of up to 24 horsepower. An ST 74 puts out 74 foot-pounds of torque or 12 horsepower; Tether recommends using it on monohulls up to 50 feet and 16 tons or to replace diesel engines of up to 48 horsepower." |
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#13
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On Thu, 02 Jun 2005 10:13:43 -0400, rhys wrote:
On Thu, 02 Jun 2005 12:43:35 GMT, (Mic) wrote: Perpetuated Motion Electric propulsion for boats: A century-old technology may just be the wave of the future LINK: http://www.cruisingworld.com/article...ID=396&catID=0 " Advocates for diesel-electric propulsion list among its virtues that it's clean, quiet, efficient, and requires very little maintenance. Another advantage frequently noted in connection with the STI system is the ability to make electricity--to "regenerate"--when the boat is under sail." "While internal-combustion engines are typically described by their horsepower rating, STI's motors are named for the torque they develop. An ST 37 puts out 37 foot-pounds of torque or 6 horsepower; Tether recommends using it on monohulls up to 32 feet and 10 tons or to replace diesel engines of up to 24 horsepower. An ST 74 puts out 74 foot-pounds of torque or 12 horsepower; Tether recommends using it on monohulls up to 50 feet and 16 tons or to replace diesel engines of up to 48 horsepower." The ST37 is right in the range for my current light cruiser, and the ganged ST74 is appropriate for my anticipated next boat, which would be a modified full-keeler. I'm watching this technology like a hawk. It makes a lot of sense on a number of levels, but of course, it isn't for everyone. In the meantime, I'm replacing the exhaust end of my old Atomic 4.... R. The problem with the STI system is the size of the battery pack required for the 144 volt system. It takes up a lot of space and adds a lot of weight. There are a lot of advantages to their system as well, especially as was already noted the regeneration under sail appeals for long passagemaking. Hopefully as the technology evolves a better and lighter battery system will be brought online. As a lover of multihulls, the current battery system takes their system off the table for me. Weebles Wobble (but they don't fall down) |
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#14
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I look for the 'pertinent omission' in marketing data and hype.
Sure one can argue the 'green' attributes of such a system; but, one surely HAS to look at the all that additional weight for the batteries and control systems. With such a boat much deeper in the water and dragging a three bladed fixed prop .... it HAS to take MORE overall energy to move such a boat. The boat is now much deeper in the water and freewheeling a gigantic prop ...... of course you now need a bigger boat that goes slower. As far that the 'energy balance' ..... I'll bet its a 'wash' thus no clear advantage. Batteries dont last forever and I wouldnt want the replacement bill for such 'monsters' added to my cruising kitty. I'm more keen on the Pardeys 'engine' choice when it comes down to 'efficiency'. In article , Mic wrote: Perpetuated Motion Electric propulsion for boats: A century-old technology may just be the wave of the future LINK: http://www.cruisingworld.com/article...ID=396&catID=0 " Advocates for diesel-electric propulsion list among its virtues that it's clean, quiet, efficient, and requires very little maintenance. Another advantage frequently noted in connection with the STI system is the ability to make electricity--to "regenerate"--when the boat is under sail." "While internal-combustion engines are typically described by their horsepower rating, STI's motors are named for the torque they develop. An ST 37 puts out 37 foot-pounds of torque or 6 horsepower; Tether recommends using it on monohulls up to 32 feet and 10 tons or to replace diesel engines of up to 24 horsepower. An ST 74 puts out 74 foot-pounds of torque or 12 horsepower; Tether recommends using it on monohulls up to 50 feet and 16 tons or to replace diesel engines of up to 48 horsepower." |
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#15
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On Thu, 02 Jun 2005 10:13:43 -0400, rhys wrote:
On Thu, 02 Jun 2005 12:43:35 GMT, (Mic) wrote: Perpetuated Motion Electric propulsion for boats: A century-old technology may just be the wave of the future LINK: http://www.cruisingworld.com/article...ID=396&catID=0 " Advocates for diesel-electric propulsion list among its virtues that it's clean, quiet, efficient, and requires very little maintenance. Another advantage frequently noted in connection with the STI system is the ability to make electricity--to "regenerate"--when the boat is under sail." "While internal-combustion engines are typically described by their horsepower rating, STI's motors are named for the torque they develop. An ST 37 puts out 37 foot-pounds of torque or 6 horsepower; Tether recommends using it on monohulls up to 32 feet and 10 tons or to replace diesel engines of up to 24 horsepower. An ST 74 puts out 74 foot-pounds of torque or 12 horsepower; Tether recommends using it on monohulls up to 50 feet and 16 tons or to replace diesel engines of up to 48 horsepower." The ST37 is right in the range for my current light cruiser, and the ganged ST74 is appropriate for my anticipated next boat, which would be a modified full-keeler. I'm watching this technology like a hawk. It makes a lot of sense on a number of levels, but of course, it isn't for everyone. In the meantime, I'm replacing the exhaust end of my old Atomic 4.... http://www.soundingsonline.com/stories.html?story=2 "Waypoint carries twin 12-hp Solomons Technology ST 74 electric motors powered by a dozen batteries. The batteries' charge is renewed by leaving the power plants running when the boat is sailing so the props turn in the water, transforming the electric motors into an electric generator. If there's no wind, a 15-kw diesel generator recharges the batteries, says Mike Stevens, Catamaran Company's Annapolis salesman. Stevens says Waypoint can run four hours at 8 knots on batteries, or 6 to 10 hours at 5 or 6 knots. He says the electric-powered cat appeals to the company's most environmentally conscious customers. "They want to sail with a green wake," he says." R. |
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#16
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Mic wrote:
.... http://www.soundingsonline.com/stories.html?story=2 "Waypoint carries twin 12-hp Solomons Technology ST 74 electric motors powered by a dozen batteries. The batteries' charge is renewed by leaving the power plants running when the boat is sailing so the props turn in the water, transforming the electric motors into an electric generator. If there's no wind, a 15-kw diesel generator recharges the batteries, says Mike Stevens, Catamaran Company's Annapolis salesman. Stevens says Waypoint can run four hours at 8 knots on batteries, or 6 to 10 hours at 5 or 6 knots. He says the electric-powered cat appeals to the company's most environmentally conscious customers. "They want to sail with a green wake," he says." R. This isn't a bad setup for a charter boat that takes short hops, but a 32 mile range on the battery charge is a bit limiting. I'm guessing that the genset doesn't come close to keeping up with the drain, so this really isn't a "diesel electric." However, on a lighter catamaran, the number might workout better. |
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#17
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Rich Hampel wrote in
: Batteries dont last forever and I wouldnt want the replacement bill for such 'monsters' added to my cruising kitty. Although they are VERY quick to point out to you that a Toyota Prius battery pack is still under a long warranty to sell the cars....If you wander back into the parts department and ask, you'll find out WHY they are VERY quick to point out to you that a Toyota Prius battery pack is still under a long warranty....................to sell the cars...... Bring out SEVERAL other thousand! Waste Marine and your local brokers must be very jealous....The markup on Ni-MH battery packs must be MOST impressive.... If you factor in battery pack replacement, operating cost is about the same as a Cadillac Escalade with a Northstar Beastie. |
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#18
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Mic wrote:
Perpetuated Motion Electric propulsion for boats: A century-old technology may just be the wave of the future LINK: http://www.cruisingworld.com/article...ID=396&catID=0 " Advocates for diesel-electric propulsion list among its virtues that it's clean, quiet, efficient, and requires very little maintenance. Another advantage frequently noted in connection with the STI system is the ability to make electricity--to "regenerate"--when the boat is under sail." "While internal-combustion engines are typically described by their horsepower rating, STI's motors are named for the torque they develop. An ST 37 puts out 37 foot-pounds of torque or 6 horsepower; Tether recommends using it on monohulls up to 32 feet and 10 tons or to replace diesel engines of up to 24 horsepower. An ST 74 puts out 74 foot-pounds of torque or 12 horsepower; Tether recommends using it on monohulls up to 50 feet and 16 tons or to replace diesel engines of up to 48 horsepower." This is cool. But, lead acid batteries and high voltage DC and salt water are like rocket fuel, deadly as chlorine. A Canadian (British) submarines had a fire recently that seems to point to the biggest drawback. Lithium iron batteries are way dear, yet. The steam idea; now what if, when you made hydrogen electrically from water, instead of throwing away the pure oxygen, you stored it and then introduced it into an I.C. engine that burned hydrogen? Would that be a steam engine? How efficient and how large or small could such an engine be? I know, we haven't figured out how to corral big lumps of H2, yet, but who knows what will come along. Isn' it unfortunate that we cannot yet efficiently derive electrolyzed O2 as a liquid? Can hydrolysis occur at very cold temperatures, under pressure? Seems to me it shouldn't matter too much, as the atomic bond of water might not be bothered much by ambient considerations. The nicest thing about all that is that if you spring a leak in the system, the water around the boat might get cold enough to walk on. 'Gorra, If gasoline is dangerous on boats, how about pressurised supercold O2? Oh, and sails inflated with H2? On subject, the balance in such a subj. electrical system, it seems to me, would be a 5 hp charger and a 20 hp, 20 minute battery drive, or about that. In a blow at sea, no self respecting sailor would prefer to rely much on the engine, when the wind is so free, if wild. Any sailboat that cannot sail might never expect to be able to power out of a storm. I still want to know how an engine would work if it dispensed cold instead of heat. Liquid nitrogen is more benine than gasoline, and could be used to suck heat through an engine if the heat source is, let's say, relatively infinite, being represented by the enormous heat stored in the liquid water of the sea. It's heat would vapourize the LN2, providing gas volume to be harnessed in an "external combustion" steam type engine, leaving in it's wake only cold water, perhaps even ice, and still cool nitrogen gas. Just think, free air conditioning as a side effect! All that is lacking is a cold temperature LN2 low volume injection pump of some sort, to introduce LN2 to a heat exchanger, boiling the LN2, providing overpressure and volume to drive a piston. A small bore, cold environment injection pump could generate a large volume of cold gas in a heat exchanger which would gain power from being warmed by the sea. A leaking LN2 tank (dewar) could asphixyate cabin occupants, so must vent overboard. Anyone being asphixyated by evaporated liquid nitrogen would likely wake up from the increasing cold before expiring. If half of the nitrogen and oxygen in a cabin were replaced by pure cold nitrogen, the ambient temperature would freeze the nose and the water in the exhalations passing through your nose. When it gets that cold, all your nasal hairs freeze together and pull on one another, causing pain, and that should wake you up before more than half of the oxygen is displaced from the room. Ask any musher about that cold effect. You can make your own liquid nitrogen. All you need is a good compressor and a heat exchanger, which stores potential energy in the form of a temperature differential, in the environment and an insulated cold tank until you want it back. Using a windmill to pump air to provide storable LN2 might even work. Terry K |
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#19
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This post presents an interesting concept illustrated in diesel locomotive
drive train description. There multiple methods of converting and transmitting energy but they all have one thing in common you never get out as much energy as you put in. The difference between energy in and energy our is energy converted to some other form that is not useable by the system (such as heat from friction). System efficiency is a mathematical description of the amount of lost energy compared to input energy. The object of any sailboat drive is to move it through the water without the use of the sails and wind. The typical drive system converts chemical energy (in the form of fuel) into rotary motion to spin the propeller. The most efficient drive system is a direct drive (such as directly attaching the propeller to the rotary motive device's output shaft). Unfortunately, most motive devices such as diesel engines do not produce an output a form of energy that is directly useable by a propeller and also they do not operate well when submerged. Hence the need/existence of some type of transmission and shafting which introduce drive system losses. A gear box type transmission has the least amount of losses. a hydraulic transmission (either in a single case [like found in modern automobiles] or separate pump/motor drive) have greater losses. The electric drive systems have more losses that a gear box but depending upon design can be more or less efficient that a hydraulic drive. Electric drive losses come from wire line losses expressed as voltage drop, battery losses in both charging and discharging, electric energy generation be it through a solar cell or engine, wind, water driven generator, motor losses converting all that electricity into rotary motion to spin the propeller, and depending upon the size and style of electric motor used, shafting and associated bearing, coupling and seal losses. My bottom line is that there are many ways to move the boat but none are perfect with no losses. The final design for each individual is a compromise based upon how much the owner/builder is willing to spend and how much energy loss "he" is willing to accept. Done right each design has its good points and its bad points but none give a free ride. Two pluses in favor of an electric drive are; 1. the electric power can be derived from both combustion (such as a diesel gen-set) and non-combustion (such as solar panels or wind mills) sources. 2. The stored electrical energy can be used for "hotel" related boat uses freeing up space and the cost of a second generator set. "Ted" tedwilliams@nospam wrote in message ... On Fri, 03 Jun 2005 14:33:22 -0300, Terry Spragg wrote: Mic wrote: Perpetuated Motion Electric propulsion for boats: A century-old technology may just be the wave of the future LINK: http://www.cruisingworld.com/article...ID=396&catID=0 " Advocates for diesel-electric propulsion list among its virtues that it's clean, quiet, efficient, and requires very little maintenance. Another advantage frequently noted in connection with the STI system is the ability to make electricity--to "regenerate"--when the boat is under sail." "While internal-combustion engines are typically described by their horsepower rating, STI's motors are named for the torque they develop. An ST 37 puts out 37 foot-pounds of torque or 6 horsepower; Tether recommends using it on monohulls up to 32 feet and 10 tons or to replace diesel engines of up to 24 horsepower. An ST 74 puts out 74 foot-pounds of torque or 12 horsepower; Tether recommends using it on monohulls up to 50 feet and 16 tons or to replace diesel engines of up to 48 horsepower." The statement above "STI's motors are named for the torque they develop" is absolutely meaningless without rotational speed. Torque is force at zero speed and is measured in foot pounds or inch pounds. Torgue is simply the force exerted in pounds at a given distance from the center of the motor shaft. For example: 12 lbs-in of torque means that imagining a lever arm connected to the shaft, at 1 inch up on the lever shaft you would measure 12 lbs of force. At 12 inches up, you would measure 1 lb of force. No rotational speed is considered. To propel a boat, the propellor has to turn. A million lbs-ft with no propellor speed won't move a toy boat. I could take a toy motor that produces .001 lbs-ft of torque and connect it through a reducer of say 10,000:1. At the output shaft of the reducer (assuming no losses) I would measure 10 lbs-ft of torque. If my toy motor top speed was 1,000 rpm, the rpm at the output shaft of the reducer would be 0.1 rpm. So, bearing that in mind, I could tell people that my electric motor and gear combination that runs on a common D cell can produce 10 lbs-ft of torque and I wouldn't be lying. In essence, torque produced by a motor without factoring in speed and time is meaningless. It cannot be equated to horsepower. The following formuala is used to convert a known (speed in rpm) and (torque in lbs-ft) into HP. HP = (rpm x T(torque))/(( 5252(constant)) For the example of my toy motor and gear combination I can easily calculate the HP. HP = (.1x10)/5252 HP = 0.000190403655750 Not much HP is it? But I get 10 lbs-ft of torque! Thrust is similar. Assume no boat or other losses have an effect on the motor/prop combination. . For an example we'll use a trolling motor rated at 40 lbs of thrust at .25 mph at the motor's maximum speed. Changing the prop to get 1 mph for the motor maximum speed, the thrust would be 10 pounds. Change the prop again to get 2 mph at the motor maximum speed would result in 5 pounds of thrust. Once again, thrust like torque must be related to speed to be meaningfull. I am well aware of electric motors being used on submarines and such. I have worked on a submarine motor that was salvaged and is in use today on a cold rolling mill. The motor is rated at 2500 hp at 600 volts at 2650 amps. That would take a lot of battery power to operate it in a submarine. The diesal powered locomotives you see are not driven directly by the engine as in an automobile. There is no gear train to the wheels. The diesal engine turns a generator. The diesal engine is known as the Prime Mover and runs at a constant speed. The field of the generator is electrically excited producing flux in the generator fields. That in turn produces volts at the output of the generature. The generator is wired to electric traction motors that turn the wheels. To change the speed, the amount of generator field excitation is varied and thus the generator output volts going to the traction motors. There is a lot more to motors, thrust, torque, hp, and batteries than I can possibly describe here. I just wanted to throw this in so nobody gets confused and thinks they are getting something for nothing. Oh, and by the way, if you had an electric trolling motor on your sailboat, and the you were sailing faster than the trolling motor's theoretical maximum speed with the given prop, the motor would turn faster and regenerate putting power back into the battery. Of course you are converting the energy produced by the wind in the sails and thus motion into electrical energy so unfortunately no perpetual motion. grin Ted |
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#20
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Linear Mode
