Solar-Powered Motor

[Rising Star]

I have a solar powered sailboat.

I use a single 48v 200 watt solar panel attached to one of my davits. It will recharge one of my banks in 2 sunny days.

Now this may not qualify as direct power but then neither is diesel power. After all, the diesel tank is a storage medium just as my batteries are.

I also power my refrigeration unit exclusively from the excess power generated by the panel using a DC converter to step down 48v to 12v.

[GordMay]

Originally Posted by SURV69

... I read a book(don't ask me which), that referred to "natural" speeds of boats...

I think you may be referring to a displacement boat’s theoretical “hull speed”, which is approximated by the square root of waterline length x 1.34.
➥ Ted Brewer Yacht Design

[SURV69]

I am not referring to the hull-speed, although the computations has some similarity to hull-speed. The natural speed involved similar parameters to the hull-speed computation(computation of friction), additionally with a computation involving the above water windage . . . not for windage purposes, but for "friction" purposes.

The computation eventually evolves into an intertia versus friction result, whereas the inertia is near-zero and the movement of the boat(topsides and bottomsides) also results in near-zero friction, resulting in a speed that is maintainable on calm waters, with no wind, using almost no energy.

The hull-speed(you speak of) of a boat appears to be multiple times more than the "natural" speed of a boat and the natural speed of a boat.

The "Natural" speed is a speed at which the energy needed to move is very minimal(it's a very minimal speed), beyond which the power curve to move the boat increases rapidly up to the power needed to reach hull-speed.

In fact, often the hull-speed of a sailboat could be increasing(given larger sailboats), while coincidentally, the "natural" speed would be decreasing. A much smaller boat generally has a greater "Natural" speed than a larger boat because of the initial force to move it and because of the amount of force need to move it at that low speed.

ANYWAY . . . the idea in general is that moving a boat at a vey slow speed(such as 1-2 knots), takes very little power and is still . . . nonetheless, considerably faster than 0.0 knots(dead wind).

This would mean continued headway on an electric motor at a greatly reduced wattage. If the boat moved within the limits of it's "Natural" speed, the wattage might be reduced so much so, that a person could(maybe), actually be "charging" a battery, while still moving forward . . . getting somewhere.

For me, on a dead-wind day, I could enjoy a 1-2 knot speed either until I got wind again or until I decide to tweak the speed a little higher . . . say about 2-3 knots.

I just don't understand why everyone is so focused on the maximum sustainable speed all the time(hull speed) when it comings to running under motor-power.

[David_Old_Jersey]

Originally Posted by sailtotrail.com

Jeez AtomicPhil, that's a ridiculous idea! Unless maybe you're the guy in this video who demos his sailboat navigating out of the harbor via electric propulsion that's recharged by regeneration, solar, wind, and/or shore power.

Since sailors got along with zero non-wind propulsion up until diesel engines (let's not get into steam) became available in the last 100-ish years, it doesn't seem that unreasonable to rely on wind 99.9% of the time and just using the electric motor to cozy up to the dock.

Interesting website. cheers.

Historically of course petrol / diesel engines came onto sailboats as auxilliaries - not intended (nor able) to power a sailboat for the entire passage. indeed it is only over the last 30 years that diesel engines have shrunk in size for the power to enable many yachts to become motorsailers in all but name.

So maybe if range under power is not an issue, then electric becomes an attractive option? that website talks of around a 10 mile range.

the battery array required is a definite negative, but I like the trade-off. And... *cough* I'm sure it isn't even close to cheap. (looks like the system in that video is either $3995 or $5494 without the batteries)

I don't see that cost as too wild, not in comparison to a re-engine with a different model, Batteries I guess would be budget for or actually replaced on a rolling basis (one a year?). My major hesitations would be on reliability within a Marine environment and cost of repair / replacement parts........and whether I had the boat, sailing skills and time to deal with a shift to 99% windpower.

But I like the idea though and I am someone who has no interest in any "green issues".

[sailtotrail.com]

Originally Posted by David_Old_Jersey

I don't see that cost as too wild, not in comparison to a re-engine with a different model

Agreed. I came back and added the parenthetical with the actual price after I'd written the rest, but failed to edit the context. That price does seem reasonable.

Originally Posted by David_Old_Jersey

Batteries I guess would be budget for or actually replaced on a rolling basis (one a year?).

Because battery charge/discharge rates change with age it's typically recommended that the entire bank be replaced at the same time. That said, budgeting one per year is different from replacing one per year, so with a bank of 5-8 batteries you might be right on.

[cal40john]

This is from the site you posted.

Solar panels or a wind generator can be added to supplement regeneration and shore power charging. This is especially useful for moored boats. Solar, wind and/or regenerative charging can allow the boat owner to be completely free of the power grid and fossil fuel power.


The OP was talking about a solar powered motor, not something supplemented by solar.

I agree completely that if all you want is something to get you out of the marina, solar with batteries will work.

John

Originally Posted by sailtotrail.com

Jeez AtomicPhil, that's a ridiculous idea! Unless maybe you're the guy in this video who demos his sailboat navigating out of the harbor via electric propulsion that's recharged by regeneration, solar, wind, and/or shore power.

Since sailors got along with zero non-wind propulsion up until diesel engines (let's not get into steam) became available in the last 100-ish years, it doesn't seem that unreasonable to rely on wind 99.9% of the time and just using the electric motor to cozy up to the dock. Granted, I'm not usually in a big hurry to get back to the office when the wind dies to begin with.

A quiet boat with one less fragrant, dirty-burning liquid on board sounds like nirvana to me. The battery array required is a definite negative, but I like the trade-off. And... *cough* I'm sure it isn't even close to cheap. (looks like the system in that video is either $3995 or $5494 without the batteries)

Okay, okay... maybe I'm defending AtomicPhil less than I am my own obsession with this technology. You got me.

Wow! That Yahoo group is nuts. Almost 12k posts with almost zero organization of the threads.

[cal40john]

Originally Posted by Rising Star

I have a solar powered sailboat.

I use a single 48v 200 watt solar panel attached to one of my davits. It will recharge one of my banks in 2 sunny days.

Now this may not qualify as direct power but then neither is diesel power. After all, the diesel tank is a storage medium just as my batteries are.

I also power my refrigeration unit exclusively from the excess power generated by the panel using a DC converter to step down 48v to 12v.

Crucial details are missing. How far and what what speed can you go?
Not saying you're wrong for going this route, if it works for you and how you use your boat great, but some might assume that you're doing an equal comparision to the 30 hours at just under hull speed that I get on my 20 gallons of diesel. Not that I like or want to spend my time motoring, but I have a minimum of 1.5 hours of canals and locks to motor through to sail on salt water (only 10 minutes the other way to the open waters of the lake). If I have a week to sail the San Juans, sometimes if the wind doesn't cooperate I'd prefer to get there and motor the 70 miles in order to actually have a vacation in the cruising grounds.

John

[Opie91]

Electric sounds like a good idea, but the technology needs to improve before it is practical for real world use. I know diesel is not the perfect fuel that can smell, but I would much rather have a little smell and noise in a gale.

It would be difficult to strap on a few extra batteries for a long trip compared to a 10 gallon diesel jug on deck.

I cannot find any new sail boats with electric auxiliary. Electric systems just don’t have enough reserve to get the job done (for now).

[Rising Star]

Originally Posted by cal40john

Crucial details are missing. How far and what what speed can you go?
Not saying you're wrong for going this route, if it works for you and how you use your boat great, but some might assume that you're doing an equal comparision to the 30 hours at just under hull speed that I get on my 20 gallons of diesel. Not that I like or want to spend my time motoring, but I have a minimum of 1.5 hours of canals and locks to motor through to sail on salt water (only 10 minutes the other way to the open waters of the lake). If I have a week to sail the San Juans, sometimes if the wind doesn't cooperate I'd prefer to get there and motor the 70 miles in order to actually have a vacation in the cruising grounds.

John

John,

Electric power is a geometrical progression of speed/distance, I can power at 3.8 knots for 3 hours on one battery bank or drive at hull speed for 45 minutes. I can also "cheat" using my Honda 2000i generator. My longest usage to date was 17 hours straight.

I am retired and cruising. If you have deadlines and schedules to keep then this auxiliary system may not suit your lifestyle.

I prefer electric over diesel because it's reliable, quiet, and much cheaper.

[sailtotrail.com]

Originally Posted by cal40john

The OP was talking about a solar powered motor, not something supplemented by solar.

The OP said "solar powered motor", and didn't provide details of a specific application that would preclude any of the discussion that followed. Rather than assume AtomicPhil was referring to a full-time propulsion system, I answered with a reasonable sailing application for what he may have been asking. The posts preceding my first were mostly dismissive (yes, also mostly of a joking nature which I enjoyed) of what I thought was a valid question.

Solar isn't a solution for full-time propulsion. Agreed. Is the combination of electric propulsion + good old fashioned wind power a valid and reasonable option for a sailing vessel? I think so.

[sailtotrail.com]

Originally Posted by Rising Star

I can power at 3.8 knots for 3 hours on one battery bank or drive at hull speed for 45 minutes.

Nice to have specifics. I love it. What are the basic stats on the battery bank you're using in this example?

[Rising Star]

Originally Posted by sailtotrail.com

Nice to have specifics. I love it. What are the basic stats on the battery bank you're using in this example?

I have 2 seperate banks. Each is composed of 4 AGM 100amp batteries. Switches control which bank powers the motor and which bank is charged.

I like to keep one bank fully charged and in reserve - just in case....

[David_Old_Jersey]

With the generator running does it keep pace with the battery drain? if not does it add a lot of range nonetheless, or only a bit? (I take your point on more speed = less range, but I am thinking 4/5 knots not full hull speed).

(as you can tell, am not very technical on electrickery )

[Rising Star]

Originally Posted by David_Old_Jersey

With the generator running does it keep pace with the battery drain? if not does it add a lot of range nonetheless, or only a bit? (I take your point on more speed = less range, but I am thinking 4/5 knots not full hull speed).

(as you can tell, am not very technical on electrickery )

The "bottleneck" in my system is the 18 amp Zivan battery charger. I could get a higher amp charger for another $500 and add another 2000i charger in series, but I have not yet felt the need to complicate my life.

With 18 amps I can cruise at 3.5 - 3.8 knots depending on wind and current (usually on the nose) until my 5 gal. gas can runs dry. With the 2000i that can take 20-25 hours. Of course you can do the math - running at say, 25 amps creates a 7 amp deficit per hour giving me 4 - 4.4 knots for 7-8 hours before the first of my two banks is depleted and must by recharged again.

[ARGold]

I am a senior electrical engineer and engineering manager.

I have been giving regenerative electrical propulsion a lot of thought lately. While the technology is still really in its infancy, there is a huge amount of work going on in this area in terms of other applications. - Not a big market for sailboats, but we could certainly ride along the coattails of what is going on elsewhere: Battery technology, Motor/generator control and efficiency, Battry charging and monitoring, photovoltaics (how about flexible photovoltaics laminated into your sails or how about photovoltaic paint/gelcoat?) - these technologies are on the near horizon.

Having said that: NOW is the time to get serious about product development. I dream of the day I can circumnavigate my sailboat free of fossil fuels and have power to get through the doldrums, in and out of port, out of trouble as it arises... The problem is, where is the money to develop these products for the boating community? Again sailboats are a small market and cruising boats (my interest) is even smaller. Having said that, I do have ideas about developing a product line towards this end - an these ideas have spin-off product opportunities in bigger markets... I'd also be interested in working on a one-off (someone who wants to develop his own boat into a fossil-free vessel).

If anyone out there is looking to get into this seriously, I'd be happy to work with them on a full-time or consulting situation. P.M. me.