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Solar powered motoryacht cruising?

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    Solar powered motoryacht cruising?

    As promised I'm now going to begin a slow barrage of questions that might seem silly to veteran boaters but I'm totally new to this and I'm pretty excited about learning how to set up my new boat as best I can. I've been browsing through the site of a company called Torqeedo that sells electric marine engines. Seriously thinking about getting one of their outboards for my tender so I don't have to bother with gasoline on board. Torqeedo also sells what they call pod drives that are essentially little electric auxiliary motors that can be bolted to the bottom of a boat. I can't help wondering if two of those pod drives bolted to the bottom of a motoryacht might give it a somewhat renewable source of long range cruising power. If you connect some solar panels to the system and maybe also use your genset to charge, do you think you could get maybe 7 knots of straight line travelling? It would be pretty cool if a system like that in conjunction with the primary diesels could extend the range of a motoryacht to allow for longer passages like San Diego to Hawaii, etc. Not something I'll entertain right away, but if $20,000 could get it done maybe five years from now (after technology improves a bit and prices come down) that is something that would really appeal to me. Is this idea pie in the sky? I don't have the knowledge to determine if the Torqeedo pods would generate enough thrust to move a big heavy boat. I do know that some forms of electric conversions have been done on motoryachts but I don't really know how successful they have been.

    #2
    Have you contacted Torqueedo? They may have data that will help you decide. Also, I suggest that you read these articles. While the propulsion system they tested is different from what you are thinking, the principles are the same:
    https://www.passagemaker.com/technic...e-great-debate
    https://www.passagemaker.com/technic...science-part-1
    https://www.passagemaker.com/technic...pulsion-part-2

    1999 3788, Cummins 270 "Freedom"
    2013 Boston Whaler 130 SS
    Anacortes, WA

    Comment


      #3
      I think this is a topic for "I was just day dreaming!". The amount of power that is needed to move a boat, at any speed, is so much that you would need a very large capacity battery storage plus an efficient means of charging that, Consider, 1HP = 735 watts, in other words, at 12.5 volts, you need about 60 amps to keep furnishing just 1HP of power from the batteries. This is less than current needed to keep your starter continuously cranking! Solar power may be a great addition to add to a boat to augment battery charging and, maybe, just may be, in short spurts running it quietly and slowly for short periods. Present technology does not allow for a purely electrical propulsion for a motor boat.

      Good luck.
      Retired, computer expert / executive
      Bayliner 285 Cruiser / Mercruiser QSD 4.2L 320 HP Diesel
      Live in the Bay Area, CA, USA, boat in Turkey
      D-Marin @ Turgutreis in Bodrum/Turkey
      bdervisoglu8@gmail.com
      bulent@pacbell.net

      Comment


        #4
        It actually takes very little power to move a boat to hull speed. Without getting into a whole ton of math, roughly 1hp/foot will get you close to hull speed. This of course is with no wind current etc. The shape of the hull, clean bottom etc will all be factors. A 40 foot hull will need 40 hp to get it to hull speed. This is if the engine/prop etc are optimized for this speed.
        I could get my 31 Uniflite to 3.5 knots with my 9.9 Yamaha high thrust.
        The Torqueedo cruise 10 is a 20 hp gas equivalent, so two of these would be enough to get a 38 close to hull speed. They also have other direct drive versions that offer highly levels of performance.
        The Greenline hybrid yacht offers up 20nm of range on electric, which for many people is a day on the water. There are many times when we do not even go 20nm in a day.
        Very interesting ideas. Cost is still what is holding some of these systems back.
        http://www.mby.com/reviews/wheelhous...-hybrid-review
        Joel
        1987 3818 Hino 175
        "Knotty Girl"
        Prince Rupert B.C.

        Comment


          #5
          Electric propulsion takes huge batteries, and a generally impractical amount of solar to recharge in a short period of time.

          There have been a few global solar proof-of-conept cruisers - and they are extremely exotic and expensive one-off designs.

          But hybrid systems can be pretty interesting if designed into the boat from scratch.

          Look into Greenline Yachts for an example: http://www.greenlinehybrid.si

          I do imagine that re-powering any Bayliner model to be a hybrid will currently cost more than the boat itself might be worth though.

          Cheers,

          - Chris
          Chris & Cherie - www.technomadia.com
          "Y-Not" - 1999 Bayliner 4788
          "Zephyr" - 1961 GM PD4106 Vintage Bus RV Conversion

          Full-Time nomads since 2006.
          Now spending half of each year slowly doing the Great Loop in our 4788!

          Comment


            #6
            There was an article in one of the recent BoatUS member magazines discussing one member that is building a hybrid diesel/electric recreational boat. From memory ( we all know how accurate that can be ) it was located some where in the mid west, was a 36 plus foot express Carver cruiser. I believe he was using twin sealed ELCO 20 HP drives. He was designing with a 60 NM range on electric power alone. He included solar collection panels and a 20KW generator on board. His hybrid range at 6 Knts was estimated at 200 NM. Interesting read but I don't believe BoatUS has their quarterly publication available online. You might send an email to them and request a copy.

            RB Cooper

            Comment


              #7
              Originally posted by MonteVista View Post
              Consider, 1HP = 735 watts, in other words, at 12.5 volts, you need about 60 amps to keep furnishing just 1HP of power from the batteries.
              It's actually 745.7 Watts per horsepower. In fourteen hundred and ninety two, Columbus sailed the ocean blue. Divide the year of his voyage by two, and you get the number of Watts in a horsepower.

              Originally posted by canoel View Post
              It actually takes very little power to move a boat to hull speed. Without getting into a whole ton of math, roughly 1hp/foot will get you close to hull speed. This of course is with no wind current etc. The shape of the hull, clean bottom etc will all be factors. A 40 foot hull will need 40 hp to get it to hull speed. This is if the engine/prop etc are optimized for this speed.
              I could get my 31 Uniflite to 3.5 knots with my 9.9 Yamaha high thrust.
              The Torqueedo cruise 10 is a 20 hp gas equivalent, so two of these would be enough to get a 38 close to hull speed. They also have other direct drive versions that offer highly levels of performance.
              The Greenline hybrid yacht offers up 20nm of range on electric, which for many people is a day on the water. There are many times when we do not even go 20nm in a day.
              This is all good if you're charging up batteries with shore power overnight before you leave the dock. Totally different story if you're trying to charge them with solar panels as OP wants to do. People vastly overestimate how much energy solar panels generate.

              Commercial PV panels have a nominal power generation of about 160 Watts per square meter. But they'll hit that wattage only on a sunny day at noon with the panel tilted and oriented so it's perpendicular to the sun. To calculate real (average) power generation, you need to multiply by something called capacity factor. That takes into account night, weather, angle of the sun changing throughout the day, angle of the sun changing throughout the year. For solar in the continental U.S., it's about 0.145. In the desert southwest it can hit as high as 0.19. Northern states are closer to 0.10. You can look up capacity factor for your region at the PWatts site (just put in your zip code and random values - one of the result figures will be capacity factor for that location.)

              http://pvwatts.nrel.gov/

              Using the 0.145 average as an example, a 160 Watt panel will produce only (160 Watts)*(0.145) = 23.2 Watts on average. Multiply by 24 hours (remember, capacity factor takes into account night) and you get an underwhelming production of 556.8 watt-hours in a day.

              Unfortunately, that's for panels fixed on land. It's actually worse for boats because you can't tilt the panels at your latitude (so the sun on average hits the panel close to perpendicular). Unless you only ever steer your boat in one direction, panels that are tilited south will no longer be tilted south the moment your boat turns. So the optimal orientation for a boat is flat (no tilt). Which means your generation is further reduced by the cosine of your latitude. Going with about the centerline of the U.S. (40 degrees latitude), this results in a further reduction by 0.766. So your 1 square meter panel on your boat is producing (556.8 Wh)*(0.766) = 426.5 Wh per day on average.

              Say you're running the 4kW Torqeedo Cruise (which they say produces about as much thrust as a 9.9 HP gas engine). Your 1 m^2 of panels will on average gather enough solar power every 24 hours to operate that unit for (60 min/hour)*(426.5 Watt-hours)/(4000 Watts) = 6.4 minutes. If you figure this motor will push your boat at 3.5 knots as stated above, that will get you a whopping (3.5 nautical miles/hour)*(6076 ft/naultical mile)*(6.4 minutes)/(60 min/hour) = 2268 feet.

              If you figure you manage to squeeze a generous 3 m^2 of panels on your boat, they would generate enough power in 24 hours to run the Torqeedo for 19.2 minutes and push your boat 1.29 statute miles. Mind you, this is an average for the country and the year. If you're in Florida or Southern California, and you're doing this in summer, you'll get more out of it, possibly as much as 3-5 miles. But overall the results are going to be very underwhelming unless you connect to shore power to top off your batteries, or you cover every horizontal surface of your boat with solar panels.

              The only way to get this to work for long-range cruising is to build an extremely lightweight and low-drag ship, cover it with a massive amount of solar panels, and spend a lot of days docked at port while the panels recharge your batteries.

              https://en.wikipedia.org/wiki/T%C3%BBranor_PlanetSolar
              1994 2556, 350 MAG MPI Horizon, Bravo 2

              Comment


                #8
                The OP wanted to use a combination of shore power(assumed), generator,solar and conventional engines to extend cruising range. Many of the hybrid systems are just that. Run the first 20 miles on electric after charging via shore power, the solar panels and or generator will give you an extra boost. Start engines and cruise under power while charging.
                These are not perfect systems, but these are the ideas that foster change.
                Joel
                1987 3818 Hino 175
                "Knotty Girl"
                Prince Rupert B.C.

                Comment

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