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  #41  
Old 03-01-2012
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Quote:
Originally Posted by klem View Post
...

In my opinion, a hybrid system can almost never be justified for a sailboat based on efficiency alone. ....
Great post.

We all know that almost all ships have diesel electric propulsion and that many changed their traditional diesel engines for economy sake. So diesel- electric can be more efficient.

Regarding small sailboats I agree with you, not based on knowing as much as you seem to know about the subject but by simple observation of the market:

Six years ago I was really interested in Diesel-electrics for sail boats and some of the major boat manufacturers were too: Bavaria and Benetau were conducted extensive research on that area and it seemed that the future was there. Fisher Panda was also investing a lot on that area. But it was a flop. I guess that the costs of a system for a small sailboat could not compensate any gain in lesser costs in fuel, and there was also the aggravated weight problem that a big battery bank represents for a sailboat.

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Paulo

Last edited by PCP; 03-01-2012 at 01:54 PM.
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Old 03-01-2012
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The above reply is well thought out and quite true. There are many scenarios that by the type of use by the operator your efficiency goes up. Example, your boat is inland on a narrow waterway and you always have to motor to get to the good sailing area, so say 10 miles motoring for a nice full day of sailing and then returning those 10 miles to your slip. Total, 20 miles using the motor but zero fuel consumption because during the first part of sailing you were regen, letting the energy captured in the sails top off the charge of the batteries. At the end of the day your on shore power.

Now for the cruiser, you let the low pressure system pass before starting on your next passage, so the winds have abated but the sea state still has those huge swells. Your not a fan of deploying a drogue, and with electric propulsion you don't have to. With the wind speed and direction, you figure to average say 8.5 kts (you have a light cat), so you set motor revs for that speed. As you climb a swell, instead of losing speed, energy is pulled from the batteries and you maintain speed. On the back side of the swell, instead of picking up speed with the chance of pitch poling, your speed is kept in check and your returning electrons back into the battery. My friends that have this system silently motor-sail most the time, allowing predictable ETAs to anchorage.

While on the hook, your solar is adequate to provide your needs even with an electric galley, but for two weeks you have been a very social animal (again, your on a cat) and have entertained guests most every night. The batteries are at 70% DOD, and you decide instead of running the gen-set, you'll just enjoy a day sail instead and top off the batteries.

So, I admit, with the up and down conversions, efficiency is lower, but the flexibilty of the system allows you to reclaim lost efficiency and then some.
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Last edited by deckofficer; 03-01-2012 at 11:57 AM.
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  #43  
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deckofficer,

I agree with what you are saying but I would argue that you are really making an electric drive system as opposed to a hybrid. It could technically be called a series hybrid but it isn't really used that way. I guess that we need to agree on a definition of efficiency to work with. You could define efficiency in terms of gallons of diesel used, joules of energy used, tons of CO2 emitted, total lifecycle CO2, cost of fuel, total lifetime cost, etc.

The drive system that I specifically responded to made a distance claim that to me looked like there only fuel source was diesel and that they did not plug into shore power. If the only fuel source is diesel, for a system of this size I would argue that the straight diesel propulsion system will actually get better fuel economy if both are optimized. If they did plug into shore power, then it is not a fair comparison at all. In terms of diesel consumed, yes you would get a big difference but if you rank by total emissions or cost, the difference won't be nearly that large.

Electric drive systems will typically be on the order of 70% efficient in this size range including the charger, batteries, controller, motor. The power plant that will power them will be on the order of 50% efficient with a 5% transmission loss giving an overall efficiency from fuel to propulsion of 33%. A diesel engine in this size range will be on the order of 30% efficient at a typical operating point. This is not a fair comparison though because the fuel sources are almost always different. Another way to look at it is that electric cars are given an mpge rating which shows them to be roughly twice as efficient as gas powered ones. Regardless, straight electric propulsion systems tend to be more efficient in large part because the power plants convert the energy from the fuel at a much higher rate than an engine which loses it as heat out of the radiator and exhaust.

Figuring out how hybrids do from an environmental standpoint is incredibly difficult and has way too many assumptions. Using power generated by powerplants tends to be good because it is easier to put pollution control devices on these large plants and you have a selection of fuel sources. The extra components necessary is bad because of the embodied energy that went into making them and the energy required to recycle them. Straight electric cars can stack up quite well depending on the batteries and how they are recycled but hybrids don't do as well because of their shear complexity.

Have you done calculations on how much solar you would need and the sort? The reason that I ask is that if you do significant motoring, I doubt that solar or regen or anything like that is going to be able to keep up with your demands for charging. Taking a 30' sailboat that wants to motor at close to hull speed, I would guess that 5KWe would be required from the batteries. Motoring for 10 hours, you would discharge your battery bank by 50KWhrs (this is a big bank). If you had 5X100W (I don't quite know where you would fit all of these) panels without tracking and you assume 8 hours of full output equivalent in the middle of summer in southern new england, you get 4KWhrs of charging each day. That means that your 10 hour run would take 12.5 days to recharge from at 100% charging efficiency. Even plugged into shore power, it would take 20 hours at 100% charging efficiency on a 30A circuit.

I am intrigued by your comments in regards to using the motor in a seaway. I would assume that the system controls on constant voltage so that prop speed is constant? Also, this would require a propeller with very little slip or the speed difference of the boat would need to be very high. If the slip was higher, then the motor would just output less as it went down the face of a wave. Unfortunately, it is still always going to take more energy to move in these conditions rather than on calm water due to the hull being less efficient through the water.

I am certainly not trying to talk you out of your conversion, I just was pointing out that the numbers in the article linked were simply not fair regardless of how they got them. Hybrid cars have shown some improvement in mileage over their gasoline counterparts but I refuse to believe that boats will see large mileage improvements unless there are large amounts of energy going into the system other than that contained by the liquid fuel. Since solar and wind have such low output compared to a drive system, either the system needs to be used only occasionally or shore power must be used. The way that I use my boat, it wouldn't work for me.
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klem,

I don't think I gave a link that had high claims, maybe someone else did. My goal is to cruise on a minimum carbon footprint and not have gas or propane on board. To do this, the galley needs to be all electric, from efficient induction stove top all the way to the 1500 watt BBQ on the railing. The dinghy needs to be electric (and I know this works very well), and everything needs to be tied into a high storage, combination propulsion/house bank of lithium batteries. I have built a number of off grid systems for remote homes and prefer a battery bank above the common 12 volt system to reduce current on the DC side. That single 1500 watt BBQ, powered by an inverter at 12 volts would pull 125 amps on the DC side. Combine that with any other appliance that might be on at the same wattage and now the draw is 250 amps. Short, heavy cables can handle that load, but you always have to make sure connections are torqued correctly and with the constant expansion from heat at that current draw, it is a constant maintenance issue. Folks still do this on their boats because they want to stay with a 12 volt DC system powering the inverter. If you go to 48 volts, which IMHO is the minimum voltage for a propulsion bank to power a <10,000 lb boat, then all your DC inverter currents are 1/4 of that of the 12 volt inverter system. The above 250 amp, wire and connector heating current has been reduced to 62.5 amps, and no more connection maintenance issues.
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deckofficer,

The claims that I was referring to were the ones in the link in knothead's post which made a range claim of 350 miles with a normal diesel and 1100 with a hybrid. I probably shouldn't have addressed the post directly to you, it was more general.

Agreed on getting the voltage up to increase efficiency and decrease cable size. I actually have melted a few battery terminals and they have gone through the case despite the cables being up to the task and all connections clean and torqued. Like you, I have done a few solar systems as well as well as building 3 all electric vehicles and 2 hybrid racecars. I also used to work as an R&D engineer designing reciprocating air compressors which are essentially diesel engines without a fuel system.

Good luck with your project.
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To answer the 2nd part of your question, yes I have calculated solar requirements. The off-grid homes I've done in the past was before China entered the solar market and I was paying over $5 per watt for the panels. Today, that has dropped to $1.13 per watt. The dinghy davit/arch would never be used to hold the dinghy on any passage, as I always strap it to the deck except for short hops in good conditions. This leaves it as the prime spot (no shadows) for the solar array and can support (4) 245 watt, 24 volt (30.8 volt output) panels. At the close to 6Kw/hr per day output, it should allow for most all house loads during the day and night except for AC, which could still be run but would require running the diesel DC gen-set for a couple of hours every other day. This is the link you might have missed, and that is the efficient and light weight DC output only gen sets. How does 8Kw of charging (at 60.8 volts and 132 amps) and weighing less than 300 lbs sound? That is lighter by over 200+ lbs than a 8 Kw AC gen-set. 8 KW Polar DC Marine Generator | Propulsion Marine
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Quote:
Originally Posted by klem View Post
deckofficer,

The claims that I was referring to were the ones in the link in knothead's post which made a range claim of 350 miles with a normal diesel and 1100 with a hybrid. I probably shouldn't have addressed the post directly to you, it was more general.

Agreed on getting the voltage up to increase efficiency and decrease cable size. I actually have melted a few battery terminals and they have gone through the case despite the cables being up to the task and all connections clean and torqued. Like you, I have done a few solar systems as well as well as building 3 all electric vehicles and 2 hybrid racecars. I also used to work as an R&D engineer designing reciprocating air compressors which are essentially diesel engines without a fuel system.

Good luck with your project.
We are birds of a feather, I also have (3) EVs, one is a stake bed truck that I converted, the other was for racing, and the third was built in China, and is a Smart Car knockoff, fully electric. My vehicles are on the EV forum.



I almost forgot my dinghy transportable, land vehicle. 0~40 mph in less than 2 seconds, 6.5 mile range.


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Last edited by deckofficer; 03-01-2012 at 02:49 PM.
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Old 03-02-2012
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Those look like great projects. Your dinghy transportable sure sounds quick. The ones that I have done are a ford ranger, old chevy 1500 and an electrathon scratch built. The hybrids were formula style open wheel racers.
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knothead has a spectacular aura about knothead has a spectacular aura about knothead has a spectacular aura about
I'm glad there are some experts here.
I am seriously thinking about something like this.



I would like to build my own, but I don't know enough about it to know where to start.
Are there any companies that you know of that make a good four wheel, solar powered electric bike?
The website for the one pictured here has disappeared in the last week.
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You can roll your own
Cloud Electric, LLC
or go store bought
Electric Bikes, Ex-Bike, E-Ride, Quadricycles, Folding Electric Bikes.
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