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Old 02-09-2009, 10:09   #1
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Alternative Propulsion Thread

I would like to open a new forum thread dedicated to discussions around alternative sailboat propulsion to include newer, and emerging, technologies that offer a glimmer of promise for the cruiser. Possible seed topics in this category will include electric motor retrovit, hydrogen and other fuels, and engine design improvements. I would prefer to exclude the debate of conventional vs saildrive type comments to that forum thread. I want to direct discussion around both bleeding edge and lateral-thinking on the propulsion methods.
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Old 02-09-2009, 10:27   #2
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Sorry I can't resist - how about the sails as propulsion?
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Old 02-09-2009, 11:44   #3
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Welcome aboard sasec!

If you check the search engine, you will find we have had numerous threads on this topic. Not to discourage this thread at all, but just to let you know.
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Old 02-09-2009, 12:25   #4
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Welcome sascec (from one newbie to another).

The problems with alternative propulsion systems are many. The cost of implementation, including battery banks and/or fuel cells is prohibitive. In the case of electric motor/battery systems you also have limited range and slow refuelling (recharging) times. Fuel cells still require fuel... Given present technology the internal combustion engine is still No. 1. In five/ten years time maybe things will change. Who knows.
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Old 02-09-2009, 13:21   #5
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With the newer batteries it seems absolutely viable to have a (cat?) light and easily driven hull driven by electric motor/s. Solar panels and wind generators would provide the juice and a small gen could be used as a back-up when the 'tank' empty.

One limitation is the power of available marine electric motors, the other is the price of the whole kit. I mean PRICE. Probably 3-4 times over what a diesel costs with 10 year's worth of fuel and spare parts.

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Old 02-09-2009, 13:32   #6
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With the newer batteries it seems absolutely viable to have a (cat?) light and easily driven hull driven by electric motor/s.
It's just not possible to generate the electricity to recharge them. Take 16 group 4 batteries and run them dead. How long does it take to recharge them? It's not the batteries. It only works if you sneak into port once every day or so to use a shore power cord.
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Old 02-09-2009, 16:00   #7
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Small lightweight boats like catamarans are subject to the same laws of physics as an airplane in the sense that the total weight of the propulsion plant and the power to weight ratio of the fuel itself must be minimal in order maximize the propulsion efficiency of the craft.

Its why we do not see jumbo jets loaded up with batteries and solar cells making transcontinental flights. Kerosene and jet engines or diesel and internal combustion engines make for a total propulsion package that has a very high power to weight ratio.

It works fine for larger vessels where the ratio of speed desired to displacement of the vessel is much lower...such as a battery powered submarine, where you would have those desired speed economies of scale because of the longer water line length. In proportion to their displacement, larger vessels do not need to move as fast or as close to hull speed. Additionally, in order to double a boats speed through the water you almost need to cube the horsepower.

So basically, unless there is a radical change in technology where there is an alternative power plant with a very high power to weight ratio, including the weight of the stored energy, such a plant for a small boat is not going to happen...unless you don't mind going real slow.

Small boats just aren't big enough.
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Old 03-09-2009, 12:04   #8
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Small boats just aren't big enough.
How true.

That just about sums up the whole discussion.
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Old 03-09-2009, 13:10   #9
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For general leisure use, you still cant beat the internal combustion engine. Its low tech enough to be serviced by anyone, cost effective to produce, spares available world wide, fuel available anywhere. Maybe adjusting a diesel engine to run on bio diesel is the best thing, and then reduce the demand on it by suplimenting electric supply with wind and solar
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Old 03-09-2009, 14:19   #10
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I agree with most of what has been said. Just please note that there has recently been that (Swiss) cat that crossed the Pond exclusively by electric propulsion. I have seen that boat in Cadiz and I bet if you just added a stick and sails, it would be a proper cruising boat.

Is generating the electricity an issue as Pblais wants? Well, to this I can only suggest that there are always two ways to respond to this question - by generating more or by using less. I am aware that there is big difference in seeing this issue by different civilisations - just compare American cars to Eurpean ones. (Said this I would still prefer to be in the Dodge car if it were to crash with a Fiat). I believe the future civilisation will be an energy-saving one, not the energy-consumingone we are living in.

I also think that charging the batteries may not be always required - even today, using the 'old' silicone, solar panels will deliver enough juice to run an electric engine (on a cat, more difficult with a mono). If there is wind then the turbines like Air-x will do the job by night (while charging the batteries by day) - and at the same time scare any pirates to death by suggesting we are sailing an aircraft carrier. And with the new silicone I believe a major breakthrough will be made, same as it has been happening with LED lights right now.

We have to be aware that the cruising market is too small to offer any incentive to big companies involved in the change (for those who doubt this statement I suggest looking at failure rate of marine instruments and comparing them to failure rates of equally priced household equipment). What will move things forward will be the car market going the electric way (if ever). After all - the dirty alternative - the diesel beast - that we will take for granted as THE alternative propulsion on most sailing boats, it is, at best, a slightly modified version of the units used in cars, tractors and trucks.

The issue of weight is also something that can be dealt with - let's not forget that weight for weight an electric motor is way more efficient than a diesel engine that relies on its physical strenth and weight to withstand the explosions and vibrations. But it is true that the weight of batteries remains an unsolved issue - the newest batteries charge and discharge extremely efficiently but they still weigh a lot. So I strongly agree on the observation that to keep the whole set a viable alternative we have to look towards new technologies in power-storage industry. (Or can we perhaps just replace our lead keels with a couple of nicely designed batteries and forget about the whole issue ? ;-)))

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Old 03-09-2009, 16:14   #11
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Is generating the electricity an issue as Pblais wants? Well, to this I can only suggest that there are always two ways to respond to this question - by generating more or by using less.
With boats the answer has always been to use less. It's the only answer. I've been working this summer removing all the halogen bulbs we use for lighting and switching to LED's. It's easy even if not exactly dirt cheap. That works for lighting! Folks can do this and it also saves the heat of the bulbs and August here it matters. Just do it. I have also converted the outdoor lighting here at the house too. It's what I call the dumb stuff.

OK, lighting is easy. No, really easy. Propulsion is NOT easy. It's the laws of thermodynamics and the associated Newtonian physics F = ma. Petroleum engines flat out work. For alternative energy it's already invented. It's called sails!

Electric engines are not easy, not cheap, and don't really address the problem. The energy has to come from some place. You can make magic batteries to store a lot but they have to be renewed - sometime. A super large battery could work for a while but becomes discharged at some point. Ignoring that fact ignores the only real issue. One needs to make a much as one consumes. To do so in real time would be perfection. A petroleum engine consumes exactly what it produces in real time. It has a lot of waste as a side bar. electric engines produce no energy but consume only. It's easy to ignore the fact that it makes no energy. Oh, gee I didn't think it mattered.

So tell me how you use less energy with an electric engine given it makes none?
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Old 03-09-2009, 17:17   #12
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So tell me how you use less energy with an electric engine given it makes none?
For starters, it's cheaper (and uses less foreign oil) to recharge the batteries using shoreside generated electricity than using a boats diesel generator or alternator on the propulsion engine.

As for the time, the new lithium batteries can be charged at 3 times the rate as lead acid for a given amp-hour capacity. I see an awful lot of cruisers who go to docks every night when travelling, and we all know that most boats rarely spend a night away from the dock. Sure, the long distance cruiser wouldn't benefit from an electric motor, but the day sailer/average boater does.

Enough people are converting cars to electric power, the motors and controllers are affordable. Batteries, motor, controller, and accesories are about the same cost as an equivalent horsepower diesel.

The drawbacks are range, without a means to charge you can only get a couple to a few hours. And as David mentioned, speed, you can only efficiently get about 80% of hull speed.

All the doubters of electric propulsion need to check out the Tesla Roadster. http://www.teslamotors.com/ 0-60 mph in 3.9 seconds, 12.4 second quarter miles at 120 mph, 240 mile range, and they can be recharged in 4 hours. Why think that boats will be so far behind?
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Old 03-09-2009, 17:22   #13
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Now I am really discouraged!!!

To find out that what I did 2 years ago - before setting out cruising was far too expensive, too hard to power, and at least 5 to 10 years from being viable.

Now if I can just find that new diesel engine, transmission, fuel tank, assorted hoses and exhaust (purchase & install) for under $7,000 (the cost of my electric system) I will switch back.
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Old 03-09-2009, 18:02   #14
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Great Replies, but lets think outside the box!

Thanks all, I want to keep the dialog active and I want to refresh some threads that appeared in this forum over the last several years. Keep your ideas coming!

Here is an article in Popular Science that caught my eye. Radical concept and not exactly marketable but it does get you thinking.

The Sun-Powered Sailboat | Popular Science
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Old 03-09-2009, 21:44   #15
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The drawbacks are range, without a means to charge you can only get a couple to a few hours.
You can require motoring at least 10 hours. I also want the fridge to run another 48 hours.That means by morning I want a full load to do it all over again. So for all the hoopla they are at the end of the day - done before mid morning snack.

It still leaves all the issues of where the energy that charges them comes from! The new Volt cars are interesting until you find out what they cost. Affordable motors are a joke. They were affordable 10 years ago. It's the operational issues that make them functionally worthless.

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For starters, it's cheaper (and uses less foreign oil) to recharge the batteries using shoreside generated electricity
I can't afford the extension cord.
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