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Old 24-04-2006, 01:11   #61
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We have some busses here in NZ that have a very cool energy harnessing device. It is a large flywhell incased in a housing. There are no breaking devices on the wheels. When the driver applise the brakes, the energy is transfered into spinning up this flywheel. It spins at a frightning speed. In fact is is so fast, the housing provides a total vacum around the wheel as the wheels surface is traveling so fast it would actually heat up. OK, so the Bus has come to a stop and now the driver wants to go again. Now all that kinetic energy is trnasfered back to the wheels and accelerates the bus upto road speed where the engine then takes over and keeps it moving till the brakes are once again applied. Very cool and very energy efficient.
Hmmmm, I wonder if we can do the same surfing downt he face of a wave, winding up the propeller so the energy can then be unleashed to thrust the boat up the face of the next wave.
OK so yeah that's stupid and I am just joking, but I do propose that we have to start thinking that far outside the box. Radicle ideas that are beyond the conventional engines we have now. We can only go so far with efficiency. There is a point were X amount of fuel produces X amount of power. Or in otherwords, the calorific value of the fuel. Some engines are coming close to that theoreticle limit. So we have to come up with a compleatly new way of doing the job.
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Old 24-04-2006, 12:57   #62
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alternative to the diesel

Kai Nui I agree with you in everything you say here except that corporate America has failed. It has in fact succeeded in snuffing many good ideas for getting away from the need for petroleum.

Hint: I understand that solar (photovoltaic) panels are in fact manufactured by the big oil companies...

Regarding alternative power, however, on a ship we always have the sea moving us about.
This is not anywhere near a full proposal but could we not have some column of liquid or even a solid mass moved by its inertia relative to the ship and convert this motion to maybe electricity?
Effectively I'm talking of harnessing the sea waves like this.
I could even imagine some kind of float outside the boat on an arm swinging about a shaft geared up to a generator.
Think about it before you choke yourself laughing at my suggestion.
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Old 24-04-2006, 13:11   #63
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skipperaris

Your idea sounds more true!! And more realistic!!

That maybe one way we could harness our energy needs. Have to modify our boats to accommodate that technology.

But, I believe it can be done with present technology?
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Old 24-04-2006, 13:15   #64
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Been done. It is a float arrangment that fits to the side of the boat. The float gos up and down in the swell and generates electricity.
But the quantities we need for propulsion are huge and waaay beyond the capabilities of any natural force to generate in a limited time of say 24hrs, let alone the storage of power to get us any great distance.
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Old 24-04-2006, 13:28   #65
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Man. What a major bummer!!

I was hoping the findings would be a simple approach. Since I know the oil companies hid some technological findings from the public? Evil. Evil I say!!

But, there has to be an answer there somewhere under our noses?
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Old 24-04-2006, 14:23   #66
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Nahhh, look guy's your all watching to many scifi movies with conspiracy theories. Oil companies are not "hiding" technology. In fact, in many instances, it is other people that are doing the R&D and oil companies are supplying the dollars by way of share investment. You would be surprised at what is going on in the background and you will be very surprised at what is going to start being released onto the market in the next few years. There are major reasons why we are not seeing stuff marketed right now. Firstly, many design concepts are being kept under wraps. Why? because of the millions and sometimes billions of dollars being put into the R&D, you DO NOT want any other possible opposition finding out about them. You want to be first to the market and have everyone else play catch up. Second, technology is still growing hugely in these games. Sometimes something needs to be invented so as some part can be produced so as some product can be made. It isn't overnight. Here's a wee side story. Miribella V, the largest single masted sailing yacht in the world, could not have been built just three years earlier than it did. Only three years. That is because we simply didn't have the techniology available to solve some of the massive engineering feats that were involved. Maybe we put man on the moon nearly 40yrs ago, maybe we had a technilogical marvel such as concord back in the early 60's, but we are still a long way from being able to do some of the amasing things happening at the mo. Mostly it is developing specialist materials. Kinda like the ceramic tiles that were developed for the shuttle all those years back now. But the ceramic simply never existed beofre then. A material had to be developed, a technique to make the stuff had to be engineered and then the tile had to be made and then thye found out it didn't work, so more research, manufacturing, testing and back through the process till out popped a tile that could handle the job. I have a personal freind that was involved in developing the things and even today, he can't tell me too much about the process, it is still to secret.
Back to the oil companies. They don't squish ideas so as they can make a buck from what they are presently selling. They want to make a buck, whether it be oil or pink pokadot spagette. They put money into development of new technology, because it takes years to get it to the consumer level. And it has to be perfect if it is goign to work. I think to many companies are rushing into the frenzy right now, trying to produce energy efficient vehicles. What's the result? Expensive vehicles that have no where near the performance and no where near the economy that the consumer expected. The result has happend before. The consumer is disappointed and the market dies and without the consumer buying, there is no return, so there is no money put into develpoment.
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Old 24-04-2006, 15:25   #67
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Another idea

How about a Savonius rotor instead of a mast and sails?
It could drive a prop directly and you could even sail against the wind!
Or it could generate electricity and store it to be used later.

Can someone do the sums?
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Old 24-04-2006, 18:18   #68
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Quote:
Originally Posted by Alan Wheeler
Hmmmm, I wonder if we can do the same surfing downt he face of a wave, winding up the propeller so the energy can then be unleashed to thrust the boat up the face of the next wave.
OK so yeah that's stupid and I am just joking, but I do propose that we have to start thinking that far outside the box.
If I remember correctly, the control system used with Solomon's Electric Wheel does exactly that. It recharges the battery rather than storing the energy mechanically, but it is the same idea. Of course, you have to be surfing down the wave FASTER than you are asking the motor to push you. If you are going slower than you wanted to, the engine just doesn't consume as much to keep you going.

There is no free energy here, though. If you want forward motion, you have to expend some energy. If you want to just go up and down on the waves, you don't need an engine.

I think one key feature we would like in electric drive systems would be to recharge at very low speeds. For example, if you can recharge the batteries just by dragging the propeller at 0.5 knots, then you can also recharge at anchor if you find a place with that amount of tidal flow. It wouldn't be so useful in the upper Chesapeake, but it would really help in South Carolina. I thought it was really cool to watch the wakes coming off docked and anchored boats in Charleston.
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Old 24-04-2006, 18:29   #69
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Skipperaris, good points all (including tongue and cheek) A savonius rotor would be an intersting thing, but I do not think it could match the efficiency of traditional sails. I like the flywheel idea, and Wheels, it is not that crazy. Using an electric motor/generater to power the boat, and adding a substantial flywheel could improve the efficiency of the motor, and allow it to charge when going down the wave faces.
I agree that the energy in sea water should be able to be harnessed to produce mechanical power, but how?
So, I proposed some ideas to improve the diesel engine, how about this? An electric motor/generater using magnetic bearings to eliminate friction. Oil filled bearings around the shaft, and a large flywheel. Could the efficiency of such a set up be increased to the point where solar or wind supplementation would keep the system charged? Adding to that the charging ability of the motor and prop while under sail?
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Old 24-04-2006, 18:56   #70
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Quote:
Originally Posted by Kai Nui
coot, second try here. I just deleted a long post darn! THe efficiency of hydrogyn was discussed in depth on this link posted earlier in this thread
http://www.rmi.org/sitepages/pid985.php
That is where I got my comparitive numbers.
Combustion engine technology is improving, and IMO the rotary diesel shows great promise.
Various sources I've seen claim about 28% thermal efficiency for gasoline engines, and about 32% for diesel. That is, about 1/3 of the energy in the fuel is turned into motion and the rest is lost as waste heat. But it is lost in a way that is a necessary part of how the engine operates.

The question, then is how much can we expect from a rotary engine? If it can get to 30-35%, then it is a reasonable alternative to existing engines, but not a stunning improvement. To a small user, a 5% improvement may just be a few dollars a week. Of course, we shouldn't overlook the significance of 5% of national consumption, which is a very large pool of oil.

You mentioned improving efficiency all along the drive train, which is a good idea no matter what engine you use.

Quote:
I am fine with using fossil fuels. I would just like to have a substantially greater range on the fuel I have. I would love to see that 125ml per hour number. This would provide about 30 hours per gallon or potentialy 8600 miles on my current fuel capacity.
The thing about fossil fuels was a comment on the first post by Kai Nui, who mentioned getting away from them.

My boat uses about 1/3 gallon per hour. If I did the math right, thats about 1.2 liter / hour, so I would be looking for roughly a 10 times improvement to get there. Just improvements in a diesel engine (even to 100% efficient) can't get me to 125 ml / hr, though a 3 times improvement in the engine and a 3 times improvement in converting the rotation into forward motion would come close.
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Old 24-04-2006, 19:15   #71
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Boat propulsion.

Just reviewing all these posts. I use sails to propel my boat and that seems to work pretty good. I use a diesel engine to get my in and out of my moorage and that works really nifty. If I wanted to go faster I would get a lighter boat, but I am happy with this one. The 2.2 liter Ecotech engine in my car is a masterpiece, nothing is being hidden. Maybe some of you guys need to drive some of the old junk to appreciate how good the new stuff is. The tyres run better, the gearboxes and rear ends have less drag, there is less wind drag. The US has coal comming out its ears, and has the technology to burn it clean. The sooner it changes the better. But clean electricity will cost more than dirty electricity and the masses may not like that. It was a Kiwi that split the first atom. The US lacks refineries, George W talked about that a few months ago. Chindia is having a huge demand on the supply side. Canada is currently making money on the sale of raw materials. I know a guy who put an auto matic gearbox in his boat, it worked like charm. We could grow enough ethanol in Canada, in fact one company already sells ethanol mixes.
The Wisdom of Crowds sounds like a good book. An example of crowds at work. After the space shuttle blew up the shares of the four major component providers went down dramatically, with Morton Thiokol dropping by far the most. The crowds took one day to figure that out, the commission took six months.
Europe has been dealing with these high gas prices for a long time. Is it a case of we don't care unless it happens to us ? I got 38 mpg on my last tank of gas, that is city and highway combined, the sail boat does about 20mpg.
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Old 24-04-2006, 19:15   #72
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Coot, all good points, the efficiency measures were tracked from raw materieals to power to the wheels, so energy needed to refine the oil or produce the hydrogyn were considered in these figures. That is where our numbers vary. 1.2 liters per hour is pretty impressive. Is that at hull speed? I would certainly support getting away from fossil fuels, and the environmental side of this discussion is certainly important, but I do not want to limit the ideas by making that the main objective. Efficiency and economy to increase cruising range, and decrease the cost of cruising is the primary motivation. decreased use of fossil fuels will be a result rather than the goal.
I had forgotten about flywheel technology. It is probably one of the oldest technologies applied to mechanical propulsion, but has been replaced in the search for lighter, faster spinning engines. For a sailing vessel, it is very logical technology. The rapid acceleration and decelleration of a boat due to wave action could be benefitted a great deal by a large flywheel. The relatively consistant RPM, also would benefit from a large flywheel.
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Old 24-04-2006, 19:43   #73
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Having no friction at all, doesn't actually solve the problem. Friction only adds a small percentage of the overall "oppositon" to the movement. For the engine, you have inertia and compression as the two main area's of robbing power. Inertia is the opposing force to acceleration. Lets say you have no friction at all. The engine is on magnetic mearings and in a vacum chamber. So if you got the engine to say 1000RPM and turned off the fuel, it would continue to run at 1000RPM with no load. but it takes power to acclerate the engine to say 2000RPM. F=MxA. (force equals mass x acceleration) Unless you can build the internals all out of carbon fibre, you will have a certain amount of mass to move. The next is the fact that the engine has to actually "pump" air. It's surprising how much power it takes. There is a lot of air ramming down the intake of a diesel at full noise. If there is a turbo or blower, then more power required to do that job as well. Then there is the compression. This is the other major power hungry area. It takes a lot of force to compress the cyclinder and is a major opposition to the motion. That's what the flywhell is there for. The mass of the flywheel keeps the engine "smooth" during each compression stroke. So you still need a certain amount of mass to act as the flywheel. the flywheel is greatly opposed to wanting to slow down, but it is also greatly opposed to wanting to speed up. So to accelerate, you need power.

OK, so lets say we have a very economical engine. Really good oil and good bearings and a vacum. so we are wasting very little energy. We would save about 10%. Yep, all that heat from combustion and friction is about 15-20% of the energy used to in total to keep the engine running with no load. So we area actually using an enormouse amount of calories in total to run the engine, but even so, the fule is atually producing an enormouse amount of calories for such a small amount. And it is going to be why the Diesel is going to so hard to replace. There is only one other thing in the world that has a more efficient way of burning fuel. That's an animal, including humans. Now to the next step. The fact is, the waste saving is going to be small in regards to over all power developed under full load. You see, apart from a very small percentage of friction being saved in our theoreticle frictionless engine, most all the energy is being transfered to movement. Movement through the entire drive train to the water and thus the boat.

So lets say we are trying to reduce losses.
At full revs and boat speed, we have approx 10% prop slip in the water so we are loosing a bit of economy. It also takes a lot of energy to spin the prop in the water. This is based on surface area of metal in the water. Hard to put a number on that one, but it is a lot. Infact it is a very high percentage. How much depends on No. blades, the shape of the blade the speed of rotation and so on.
Depending on the shaft size and seal type, We loose a small percentage in the seal friction. Can be low in some designs and very high in others and very very high if there is a fault.
Then you have the gearbox. Most all of us has some sort of box. They can rob power ranging from 10 through to 30% just to turn the box. So there are a lot of areas where some big wastes are. But are they fixable? It is one main reason why a directly connected variable speed electric motor doesn't have to be so big. There are very little in the way of losses apart from the seal and the prop.
Now here is a nifty one idea. I just thought of this from a job I did a long time ago. I was on a Mussle barge fitting an autopilot. The drive was a hydraulic motor. But get this. The motor had the prop fitted directly to it and the entire thing was in the water and could be swiveld 350degree for stearing. Imagine an electric motor that could be placed under water and the prop fitted directly to it. The only energy loss would be prop and inefficiences of the motor. Then you have a Diesel electric to drive the electric prop.
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Old 24-04-2006, 20:02   #74
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Very good points Wheels. THe hydraulic drive was my idea to solve the gear box issue. A hydraulic drive unit placed outside the hull and directly connected to a variable pitch prop could be very efficient. Drive this with a low or zero friction electric motor, and the electrical requirememnts would be very low. Your points about wasted heat energy, and power required to get a flywheel turning are well taken, but on a boat, with a hydraulic drive, the motor or engine would not have to change speed to any great degree, so the power lost in accelleration would be negligable. A low friction motor connected directly to a very efficient prop would be a great way to propell a boat, and the shaft could be sealed with oil filled bearings as noted before. This would eliminate virtually all drivetrain friction. A prop with sufficient diameter and weight to act as a flywheel would add even more to this efficiency and, again, reduce power loss due to changing loads in wave action, while providing charging characteristics when sliding down a wave.
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Old 24-04-2006, 23:11   #75
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Hydraulic is very inefficinet. It takes a lot of energy to move a very viscouse fluid around through all sorts of little pathways inside pumps and motors and through valves and checks and reliefs and so on. It amounts to so much fristion, the oil will get really hot and has to be cooled. A lot of hp is simply lost in running the system, before the work gets to the prop.
Also to add to the big prop idea as a flywheel. Actually and flywheel effect is NOT what you want. It's once again a case of, you can't get energy from nothing. It takes energy to swing the flywheel upto speed, some kinetic energy maybe used to keep the prop spinning without too much loss, but it will loose. The same amount of energy, plus frictional loses, must be restored to the prop to bring it back to speed again. So you don't save a thing. So it is actually better to have as lighter prop as possible. Then it takes very little energy to swing the prop and when it slows, it takes very little energy to get it back to full RPM again. All the energy is expended into thrust, not swinging mass.
Then the next issue is prop. A large diameter is harder to swing in the water. Large diameter is designed for very slow RPM. Small diameter will spind faster. So it really depends on what RPM range the motor is going to turn at. Remember, more blade area means more friction in the water which means more effort for nothing. Small diameter means easier to turn, but also means more slip at low RPM. Small props are designed to bite at higher RPMS.
It's never simple.
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