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wind energy

energy harvest by sailboat
  (+3, -2)
(+3, -2)
  [vote for,

With data on wind patterns and ocean currents, a sailboat goes to the appropriate area, drops into the water a towed hydro electric generator, and optimal use of the air and ocean currents. The electric energy produced is used by onboard water electrolyzers to make hydrogen and oxygen. Of course hydrogen and oxygen are stored separately. The settings of sails and hydro generator are such to maximize efficiency. Water turbines are more efficient than wind (air) turbines whereas sails are less efficient than windmills in capturing air kinetic energy; so the sailboat efficiency should be about the same as for windmills.

The tallest windturbine has a rotor diameter of 413 feet; a rotor tip can reach as high as 600 feet. Most windturbines have a rotor diameter of 270 feet; a rotor tip can reach as high as 450 feet. The tallest sailboat mast is about 290 feet. So energy generating capacity of a large sailboat is not that smaller than a commercial wind turbine. A different setup has a partially filled balloon hoisted up to, say, 1000 feet; the wrinkles in the balloon giving it wind resistance.

cecil0132, Sep 07 2009


       [+] except for the dumb parts... something wrong with batteries ?
FlyingToaster, Sep 07 2009

       Well, yes. On the other hand, it would be grotesquely uneconominic compared to either a wind turbine or, say, a solar-powered hamster furnace.
MaxwellBuchanan, Sep 07 2009

       [MB] how ? for energy you have wind in the sails (which is orders of magnitude more than a wind turbine) minus the water drag of the ship... could even have regenerative electric-paddlewheel /sailboats.
FlyingToaster, Sep 07 2009

       batteries are heavy and, more importantly, expensive. Given the harsh conditions of ocean travel, the battery's lifetime will be shorter than when used on land. One wants to set up something that will be commercially feasible.   

       There are a lot more sailboats than there are windmills. Building sailboats are a lot cheaper than windmills. windmills are stationary whereas the sailboats can follow wind patterns.   

       Sailboats cruise at about 20 knots. With the hydroturbine in the water, they may cruise at, say, 7 knots. The difference in the kinetic energy is the energy collected.
cecil0132, Sep 07 2009

       decent motor and battery pack will get you 80-85% efficiency in and out. Electrolysis on the other hand you'll be lucky to get 40% from turbine to tank.   

       change the title to something a bit more descriptive please and thankyou.
FlyingToaster, Sep 07 2009

       The issue is not so much efficiency but commercial possibility. Electrolyzers and its attending high pressure tanks are at least 10 times cheaper than the batteries and the attending electronics. And the electrolyzers last longer than the batteries. The viewpoints of scientists and engineers are different. Scientists look for proof of concept, damn the costs. Engineers look for practicability, ease of manufacture, maintainability,and commercial feasibility.
cecil0132, Sep 07 2009

       //[MB] how ? for energy you have wind in the sails (which is orders of magnitude more than a wind turbine) minus the water drag of the ship... could even have regenerative electric-paddlewheel /sailboats.//   

       The wind in the sails will not be 'orders of magnitude' (>100 fold) more than a wind turbine. Plus you are converting electrickery to hydrogen and ultimately back again. Plus the cost (in all respects) of building, installing and running a land-based wind-turbine are a lot less (probably one order of magnitude) than that of building and operating this schnazzy ship.   

       Cecil says it's cheaper to build a sailboat than a wind turbine. But, for the same energy capture, I just don't believe this. Anyone have any figures?
MaxwellBuchanan, Sep 07 2009

       The largest windmill that I mentioned costed more than $10,000,000.   

       from www. windustry. org/ how-much- do-wind-turbines- cost:   

       Most of the commercial-scale turbines installed today are 2 MW in size and cost roughly $3.5 Million installed.   

       I can assure you that an ordinary sailboat does not cost $3.5 million. Some people cannot resist "gold-plating" certain systems.   

       As I mentioned before, the wind in the sails will not be as much as a commercial windmill. But the windmill has about 35% efficiency whereas the efficiency of a hydroturbine is much greater (> 65%). So things balance out, efficiency-wise.   

       The oxygen can be sold to high-value markets (hospitals), medium-value markets (manufacturing), and low-value (power plants). The hydrogen can be sold to high-value markets (fuel cells of hospitals, of police stations, etc.), medium-value market (oil refineries), low-value market (power plants). One may revisit the range of specialty chemicals which can be produced electrochemically so to make these trips more profitable.
cecil0132, Sep 07 2009

       OK, a couple of problems here. First the wind energy is modified by wind velocity and swept area. Even if a windmill and sailboat had the same mast height, the windmill would have roughly 8 times the swept area, but even more the sail will be closer to the ground so much of it's swept area is wasted on the slower speed winds at very low altitudes. Windmills are usually placed at high altitudes to start, but the sailboat will always be roughly at sea level. You could tip the scales back a bit if you dumped the idea of normal sails and went with large parasails which could be flown to real altitudes and have HUGE sail area.
MisterQED, Sep 07 2009

       On the issue of parasails, I agree.   

       I was not about to write a dissertation on this setup. In my description above, I said "The settings of sails and hydro generator are such.." Which means -among other possibilities- that extra sails (parasails, for example), or change from a common sail to another sail out of Mylar (with perforations), or a partially inflated balloon. Of course, one needs to watch out for the weight of cable, electrostatic effects, etc..   

       "Windmills are usually placed at high altitudes to start,"   

       That is why the description begins with "With data on wind patterns and ocean currents,..". The sailor will have wind and current info from radio/satellite, and go to the favorable wind areas and ocean current areas. At some time the sailboat may be automated, with webcams and all that jazz. So the "up" time for sailboats will be much greater than that of windmills.   

       Where windmills are stationary, the sailboats are mobile. Where windmills have one purpose, the sailboats have other uses. Where, for off-shore windmills, one has to setup underwater cables (a big expense and a ecological perturbation), no need for cables in this setup. One needs a mechanical facility at ports to transfer automatically either the gas cylinders or the gas(es) itself.
cecil0132, Sep 07 2009

       Also this setup combines both wind energy and ocean current energy. If air velocity is opposite to ocean current velocity, then that is great. Windmills can only exploit wind energy. There are projects relating to ocean currents, large underwater turbines or large buoys (wave energy): they too need underwater cables with the attending costs and ecological perturbations and they cannot exploit wind energy.
cecil0132, Sep 07 2009

       As a rough rule of thumb, the length of a sailboat is about 1.1 to 1.5 times the height of the mast. Suppose one has a 60 m (180 feet) sailboat and that, port and starboard, one has two (60 m x 2m^2) cylinders. At 1000 atm h2, at 280 K, a cylinder contains an equivalent of more than 2000 liters of gasoline. Volume-wise, that is 15 times the energy density of Lithium-ion batteries. If the pressure is, say, 300 atm, it is still 5 times the energy density of Lithium-ion batteries. One can vent off some (or all) of the oxygen produced but that depends on the market (want to make a profit).   

       As one commentator said, the drag on a ship is large. Precisely. And the drag varies as the square of the speed. Cut the speed in half and the drag decreases 4 fold. This tells you that, even with ordinary sails, there is a fair amount of force exerting on the sail. With the hydro-generator in the water, the speed decreases (say, by half) and the force on the sails increases (albeit slightly).   

       Suppose that the force on the sail is N newtons. With the sailboat going at a constant speed S, the drag on the ship is also N newton (but in opposite direction. Decreasing the boat speed in half - to S/2 - the drag on the ship is now N/4. Meanwhile - since the force on the sail is a function of the RELATIVE boat-wind speed - the force on the sail is slightly greater, say, 1.05 N. With the turbine put into the water and the setup going at constant speed S/2, the force exerted on the turbine is N (1.05 - 0.25) = 0.8 N. The maximum energy collected by the turbine is N*L*(0.8), where L is the distance travelled by the boat.   

       Because air density is low and quite inviscid, turbulence happens very easily. And turbulence is the sapper of energy extraction. That is why windmill efficiency is usually around 20%, occasionally up to 35%. And, since water is high density and high viscosity, with low boat speed, turbulence does not occur that often (the design of the hydrogenerator is such to minimize cavitation). So the efficiency of hydrogenerator is about 65%, often up to 80%.   

       The key cost issue is one of human manpower. Already one sees transfer of industry going from the US to China because of labor costs. I do not envisage American or European unionized sailors doing this work.   

       This setup can be ideal for small island communities, with low population and isolated from large countries.
cecil0132, Sep 08 2009

       //difference in the kinetic energy is the energy collected// - this is true for the setup: accelerate to 20kt, drop turbine, decelerate. It is not true for the long run.   

       //I can assure you that an ordinary sailboat does not cost $3.5 million// And i can assure you an ordinary sailboat does not produce 2MW electrical energy, much less store it as hydrogen.   

       As [Flying_Toaster] said: //[+] except for the dumb parts//
loonquawl, Sep 08 2009

       Of course if you were *that* set on making H2 for whatever reason, you could bring along a bunch of inflatable balloons then head back to shore trailing a mile or so of your "catch" behind you. (add water if extra buoyancy is contraindicated).
FlyingToaster, Sep 08 2009

       Quantum Sphere Inc (Santa Ana, CA) has produced nano-tech related electrodes (QSI-nano II) which has 80% and 60% conversion efficiency at 0.1 A/(cm^2) and 1.0 A/(cm^2) respectively. The efficiency for platinum at 0.1 A/(cm^2) and 1.0 A/(cm^2) is 70% and 40% respectively. The efficiency for nickel at 0.1 A/(cm^2) and 1.0 A/(cm^2) is 45% and 20% respectively. The new generation of electrodes makes water hydrolysis competitive with battery charging.   

       Carrying hydrogen in balloons is problematic since one is in a windy area. There is also the issue of membrane porosity which allows some o2 diffusing in and h2 diffusing out.   

       There are commercial tankers carrying natural gas either in compressed or liquid (most often) form. For them to carry methane in balloons is absurd.   

       Hydrogen storage technology in cylinders is a mature one. As I stated in a previous comment, at 300 atm, h2 has 5 times the energy density of Lithium-ion batteries. I know many people are stuck on batteries: once the batteries are fully charged, you have to return to port. Space is at a premium on a ship and compressed h2 carries a much bigger punch than batteries.   

       Suppose the specifications were for 300 atm with the cylinders being able to withstand, say, 1500 atms. The boat has the opportunity to harvest more energy up to, say, 600 atm or 1000 atm. Cannot do that with a battery system. The extra EMF to produce hydrogen at high pressures is small. In fact a cryogenic setup - where electrolytic production of high pressure (> 1000 atm) hydrogen gas at room temperature which is then expanded to produce liquid hydrogen - has been commercialized.   

       Keeping the system dumb is the point for commercial feasibility. No need to gold-plate it.   

       Same for size of sailboats, there is no need for sailboat to collect at 2 MW to gain competitive advantage. A fisherman may get into a h2 or o2 contract when fishing ( or tourism) season is over. And retrofitting the sailboat should be cheap.   

       " - this is true for the setup: accelerate to 20kt, drop turbine, decelerate. It is not true for the long run." Incorrect. Read a previous comment of mine.
cecil0132, Sep 08 2009


       Or just use it to produce electricity, and either fill up batteries,   

       or create desalinated water in giant plastic bags, using reverse osmosis,   

       or run water sprinklers to get salt and minerals, and at the same time create a misty environment where crops can be grown,   

       or, and this is the best one, use the energy to clean up the ocean and create a thriving marine environment by aerating the water. This will bring large amounts of fish to the area, and you can then, together with Greenpeace decide how to catch some of the fish, without hurting the environment.   

       On the other hand, at the end of the tour, it could use some of the hydrogen for a blimp, and sail in the air, quickly, to wherever it needs to go.
pashute, Jul 09 2013

       As far as cost, I can't see the cost of a wind turbine's structure being greater than the cost of a sailboat's hull, and that's the only practical difference between the two.   

       Both require a large generator. Both require propeller blades (wind turbine vs marine prop/turbine, the former is larger, but the latter is more expensive/unit area due to a harsher environment). The turbine requires a pillar, the ship requires a hull, mast, and sails.
MechE, Jul 09 2013


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