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Old 07-23-2007, 11:03 PM   #15
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Back in the seventies, I was involved in communications systems R&D activities at a location where two groups formed - proponents of X21 (circuit switching) and X25 (packet switching ) standards as the way forward. Not much talk of either these days but both served to move communication thinking forward until actual transmission technologies supporting really high data rates were developed - speeds which we could only dream about in the seventies.

Would I be right in thinking that the future of marine cruising power lies not so much in more efficient and effective variants of what we now know and love/hate but rather with some technological advance about which we can currently(sorry!) only dream?
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Old 07-23-2007, 11:22 PM   #16
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Direct Current is much more efficiant then AC hands down.
Daytrader...I will always be able to produce a stronger magnetic field with an electromagnet having higher field line density at far less cost than you will ever get with even the highest strength rare earth permanent magnet. In doing so, I get greater voltage and current for a given input power i.e., higher efficiency. The most efficient motor in the world is a 3-phase Ac motor at 98% efficiency.

The AC motor has the advantage of being the lowest cost motor for applications requiring more than about 1/2 hp (325 watts) of power. This is due to the simple design of the motor. For this reason, AC motors are overwhelmingly preferred for fixed speed industrial and for commercial and domestic applications where AC line power can be easily attached. Over 90% of all motors are AC induction motors. They are found in air conditioners, washers, dryers, industrial machinery, fans, blowers, vacuum cleaners, and many, many other applications.

The simple design of the AC motor results in extremely reliable, low maintenance operation. Unlike the DC motor, there are no brushes to replace. If run in the appropriate environment for its enclosure, the AC motor can expect to need new bearings after several years of operation. If the application is well designed, an AC motor may not need new bearings for more than a decade.

The wide use of the AC motor has resulted in easily found replacements. Many manufacturers adhere to either European (metric) or American (NEMA) standards. MEaning they can be purchased at any harware store anywhere in the world. Having to replace a DC motor will take you more than a month at some locations on the planet. So, which would you prefer to have driving your watermaker, refrig and econ?

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Old 07-23-2007, 11:24 PM   #17
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http://en.wikipedia.org/wiki/Diesel-electric

I never knew boats used it. I did know locamotives did. Seems lie it has been around a bit.
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Old 07-24-2007, 12:04 AM   #18
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Would I be right in thinking that the future of marine cruising power lies not so much in more efficient and effective variants of what we now know and love/hate but rather with some technological advance about which we can currently(sorry!) only dream?
This is a very good point....that disruptive technology is the one we are always trying to find and at the same time look out for in case our competition finds it first. A lot of new things are being discovered in electrochemistry everyday, so who knows what the future of power generation holds.

I still think the ultimate solution involves extracting hydrogen from the water that we sail upon. The challenge is always cost, efficiency and reliability.
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Old 07-24-2007, 03:04 AM   #19
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from what I am hearing electric propulsion would be more efficient with a 3 phase AC motor than a magnetic DC drive as currently proposed by people such as Panda (who makes hybrid AC DC gensets with their AGT range),

I don't see the need for torque (no tire to tear the tar),

Having to invert DC bank to AC drive might not be unfavorable (ie reference technautics),

I guess there would be the loss of propeller generation when under sail:

why is everyone gone DC?
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Old 07-24-2007, 03:55 AM   #20
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from what I am hearing electric propulsion would be more efficient with a 3 phase AC motor than a magnetic DC drive as currently proposed by people such as Panda (who makes hybrid AC DC gensets with their AGT range),

I don't see the need for torque (no tire to tear the tar),

Having to invert DC bank to AC drive might not be unfavorable (ie reference technautics),

I guess there would be the loss of propeller generation when under sail:

why is everyone gone DC?
DC power is much cheaper to generate then AC power.

In the production side it is kinda differant. It takes much larger armatures and windings to produce AC then it dose DC.

3 phase AC is a better choice then Single phase AC. The equipment is much cheaper and smaller. You then have the problems of everythign else on board needing to be 3 phase or converted down.
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Old 07-24-2007, 04:21 AM   #21
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OK, now things get complicated. There are applications in which various types of DC motors have advantages over simple AC motors. In fact, many of these DC motors replicate the waveform of the AC power source through drive electronics to produce asynchronous drives or generators. These systems are optimized for the anticipated rpm or torque of the application. So, for regenerative power from the prop, certain types of elecrtonically modified DC motor-generators are more efficient than standard AC generators.Something to keep in mind is that no matter how much power your DC genset produces, your batteries can only accept a certain charge rate depending on the chemistry of the battery. As such, you will still need a power manager to properly charge your batteries to prevent cooking them. Most of these power manager/battery charging systems are AC-based programmable rectifiers.http://www.interq.or.jp/japan/se-inoue/e_car2_3.htmTherfore, just because you are producing 4kW, doesn't mean that your batteries will accept 4kW. In fact, it is very unlikely that your batteries will accept more than a fraction of the power. So what are you going to do with all that extra power? Make water, chill the freezer. Well, the most efficient method to do this is AC...therefore why not just use an AC genset to begin with and power a nice sophisticated battery charger.
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DC power is much cheaper to generate then AC power.
I'm sorry, this simply is not true.
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Old 07-24-2007, 05:30 AM   #22
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OK, now things get complicated. There are applications in which various types of DC motors have advantages over simple AC motors. In fact, many of these DC motors replicate the waveform of the AC power source through drive electronics to produce asynchronous drives or generators. These systems are optimized for the anticipated rpm or torque of the application. So, for regenerative power from the prop, certain types of elecrtonically modified DC motor-generators are more efficient than standard AC generators.Something to keep in mind is that no matter how much power your DC genset produces, your batteries can only accept a certain charge rate depending on the chemistry of the battery. As such, you will still need a power manager to properly charge your batteries to prevent cooking them. Most of these power manager/battery charging systems are AC-based programmable rectifiers.http://www.interq.or.jp/japan/se-inoue/e_car2_3.htmTherfore, just because you are producing 4kW, doesn't mean that your batteries will accept 4kW. In fact, it is very unlikely that your batteries will accept more than a fraction of the power. So what are you going to do with all that extra power? Make water, chill the freezer. Well, the most efficient method to do this is AC...therefore why not just use an AC genset to begin with and power a nice sophisticated battery charger.I'm sorry, this simply is not true.
How is it not true?

I can only speak from what I have seen and delt with. I am a green energy nut. Always have been.

When I tour the Coal fired power plant in Baldwin Illinois. I was shocked to find that that huge power plant produced DC power. That is then converted to AC.

The Breese Illinois, Mascoutah Illinois and Scott Air force Base all have their own oil fired/natural gas plants. Each produces. DC power that is converted to AC.

Many of you Wind Power plants are DC some are AC. Both have to be rectofied.

Much of the world uses DC power. Here in the USA we use mostly AC power and Gasoline. While the rest of the world sips DC power and Diesal fuel.

I think we will just have to agree to disagree on this issue.

Like I said, I am kinda a green energy nut. I do not pay a power bill on my home. I get paid to use power in my home. When the power was out here for 5 days last summer due to 5 tornadoes hitting out town. I had power. So did my grocery store. All the big coolers/freezers and such. No problem running them. The only thing we had problems with were the lights as we never integraded them to the converters.
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Old 07-24-2007, 10:13 AM   #23
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On a recent visit to the States, I picked up the July edition of Cruising World which has an article comparing the implementation of hybrid systems on a Lagoon 420 and a Moorings 4200. Interesting for me cos it had nice coloured component diagrams and fairly simple explanations of what's actually going on; possibly of interest to the more technically able here because the Lagoon system is AC driven while the Moorings implementatrion is DC based.

I guess that both represent the diesel electric approach which seems good to me in that they both isolate the power generation component (diesel) from the rest of the system and open the door to its replacement by equivalent more efficient, effective, cleaner sources; it would also allows others to focus on the more efficient use of the power generated.

Mad thought for the day but has anyone considered how conventional petrol engines might be applied as generators possibly using propane/butane which, much as I hate/fear it, is on board anyway and relatively clean; in the same vein, why can't the ever present outboard or variant thereof be put to use when at sea. Loopy? Maybe but quite possibly not half as loopy as the solution that will inevitably appear!
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Old 07-24-2007, 03:53 PM   #24
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haveblue is (or was) trying to do a similar project.
Yes, I am good friends with Craig Schmitdman who founded HaveBlue. It is very unfortunate about what happened with his company. He certainly was doing the right thing.

I've talked with him about buying the rights to his patents.
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Old 07-24-2007, 04:02 PM   #25
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How is it not true?

I can only speak from what I have seen and delt with. I am a green energy nut. Always have been.

When I tour the Coal fired power plant in Baldwin Illinois. I was shocked to find that that huge power plant produced DC power. That is then converted to AC.

The Breese Illinois, Mascoutah Illinois and Scott Air force Base all have their own oil fired/natural gas plants. Each produces. DC power that is converted to AC.

Many of you Wind Power plants are DC some are AC. Both have to be rectofied.

Much of the world uses DC power. Here in the USA we use mostly AC power and Gasoline. While the rest of the world sips DC power and Diesal fuel.

I think we will just have to agree to disagree on this issue.
Daytrader -

The reason some power plants generate electricity using DC rather than AC is most likely due to turbine RPM rather than ease or cost.

The main generators in nearly all electric power plants are AC generators. This is because a simple electromagnetic device called a transformer makes it easy to increase or decrease the voltage of alternating current. Engineers build AC generators that produce current with only a certain voltage. For many large generators, this voltage is 18,000 or 22,000 volts. By means of a step-up transformer, the voltage can be increased as high as 345,000 or 765,000 volts to force the current over long distances. In the area where the current is finally used, a series of step-down transformers lowers the voltage to a usable level. Most household appliances, for example, operate on 115 volts. Some office buildings and factories use voltages ranging from 480 to over 4,000.

If DC was used for transport of electricity, we would have electrical generating stations every couple of miles because transmission line losses would be too high for the electric company to make money (This was Edison's approach, Westinghouse with the help of Tesla educated Edison on this subject. So, when you say that most Europeans use DC, you are very mistaken.

Many DC generators are driven by AC motors in combinations called motor-generator sets. This is one way of changing alternating current to direct current. Factories that do electroplating and those that produce aluminum, chlorine, and some other industrial materials need large amounts of direct current and use DC generators. So do locomotives and ships driven by diesel-electric motors. Because commutators are complex and costly, many DC generators are being replaced by AC generators combined with electronic rectifiers. Rectifiers are devices that let current flow in one direction only. They permit use of simpler, more rugged AC generators, even when DC is required.
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Old 07-24-2007, 09:14 PM   #26
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From the Lagoon web site:

Q: 2 x 8kw available power seems to be weak for a catamaran of this size and windage, especially since it isn't always possible to have calm seas for anchoring or for leaving/entering harbours. Plus, taking into account the variables in electric power, it is conceivable that only half of the power is actually available from the theoretical amount.

A,: Based on measure taken from the Lagoon 440 : 5 knots speed under power in 25-30 knots of wind in moderate seas. (Consistent readings with the 17.5kw genset). There is a lot of power loss in diesel engine configurations (propeller with imperfect pitch or diameter, vibrations, transmission loss, etc.); and when one looks at the hull drag curves, on can see that as a matter of fact the theoretical kilowatts needed to attain target speeds are very similar to the values of electrical propulsion. In addition, we purposely limit the target speed, because the power needed to pass the 8 knot level is exponential: you need twice as much power to go from 8 to 9 knots!

I think Lagoon will have a lot of warranty issues in the upcoming years. I can't imagine this sophisticated system working in a robust manner. This is just my opinion of course.
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Old 07-25-2007, 09:31 AM   #27
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If DC was used for transport of electricity, we would have electrical generating stations every couple of miles because transmission line losses would be too high for the electric company to make money
I am finding this debate interesting, amusing, and educational. I spent my career, working for first General Electric (an offshoot of Edison Electric), than Power Machine Works, back to GE, than I had to cross the street and work for Westinghouse, which later became Eastern Electric, and later Grand Eagle. All companies except GE, no longer exist.

The "Current Wars" fought between Thomas Edison and George Westinghouse are no secret. They are history; old history. I did not know the debate continued.

During my employment with the above companies, I probably serviced, or remanufactured every part on every possible size, type, style, and brand of AC and DC motor and generator in virtually every application, and industry, from Billings Montana to Salt Lake City Utah, to Little Rock Arkansas, to Schenectady New York (Zip Code 12345), and back, and everywhere in between.

My home was in Bismarck North Dakota at the time, and sometimes I almost passed myself in the airport, coming and going. One of our major customers was the Falkirk Mine, another was Coal Creek Station.

Power transmission via DC is not an if, and it does not have a generating station every couple of miles. It in fact exists, and has been in operation since the 70's and transmits power from central North Dakota to central Minnesota, a distance of 436 miles. It is economical and profitable, although rare, and very unique; not the common, ordinary, "household" AC high voltage transmission system.

Check it out. Here

Google Coal Creek Station for more information.

Jeff

Although George Westinghouse was most noted for inventing the air brake; I was more fond of Thomas Edison. ......I never got along very well with the guys at Westinghouse INC.

....well we became good friends in time, but coming from arch rival GE, it was an uphill battle.

....I bought more beer than they did.
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Old 07-25-2007, 06:14 PM   #28
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I find it difficult to place Edison on a pedestal considering how he cheated Tesla. Just my opinion of course.

HVDC is statistically insignificant with only 0.05% world wide power transmission (not necessarily DC generation) and it has only very recently become “truly” competitive with AC transmission for distances greater than 700km…for general distribution, it still makes no sense. Europeans are not getting their power at home in DC form. In a few situations power is being distributed between dissimilar AC transmissions. Just for comparison, nuclear power plants represent 12% of the world wide power generation.

In Edison's time it would have required generation plants to be closely located because they didn't have HVDC or an economical way to step down voltage.
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