Page 1 of 2 12 LastLast
Results 1 to 20 of 29

Thread: Solar electric cat

  1. #1

    Default Solar electric cat

    I am taking my 2002 Voyage 440 cat and making her into a live-aboard Caribbean solar electric boat. I am removing the sailing rig and the Yanmar diesels. I am building an 18 foot by 32 foot roof over the boat with 20 solar panels generating 7200 watts of power. I am using Oceanvolt SD15 electric sail drives, 15 KW each, my battery bank is 8 SuperB 12 volt, 2 KWH LiFePO4 batteries for a total of 16 KWH storage at 48 VDC. I have two DC Polar diesel gensets; each is a 40 HP Volvo direct coupled to a 17 KW 48 VDC generator. Everything goes through the battery bank, solar in, genset in, electric drives out, house 12 VDC out.

    The big solar roof will make the interior much cooler for the Caribbean, and we should be able to cruise at 5-6 knots just on incoming sunlight alone, 20-30 NM on just battery, or round-the-clock passages using the Gensets at night. Everything is duplicated; the solar array is split into two arrays, 2 MPPT controllers, 2 electric sail drives, 2 gensets. Each hull is a separate system for redundancy at sea.

    If anyone else is going electric and wants to share, please reply to this thread. If anyone is interested in the removed hardware, I posted that in the classified section thread.

    Happy quiet boating!

  2. #2
    Join Date
    Dec 2008
    Location
    Now cruising in the SUN! On my way to Malta.
    Posts
    1,058

    Default Re: Solar electric cat

    Very interesting and unique concept! Would it not be practical to add one / two water generators to your cockpit transom which would be producing incoming electric power when you're moving along under power?
    Roger

    ------------------
    I look to the future, because that's where I am going to spend the rest of my life - George Burns

  3. #3

    Default Re: Solar electric cat

    Quote Originally Posted by multihullsailor6 View Post
    Very interesting and unique concept! Would it not be practical to add one / two water generators to your cockpit transom which would be producing incoming electric power when you're moving along under power?
    I am removing the sailing rig to make this a power cat powered by the sun. Using a water generator would reduce efficiency as I would be using electricity to move the boat to generate electricity. I may add a wind generator, though.

  4. #4
    Join Date
    Oct 2008
    Location
    Port Canaveral Florida
    Posts
    708

    Default Re: Solar electric cat

    Wait, you are removing an ecologically friendly method of powering the boat, day or night more than 100nm per day ... then you are spending a small fortune to replace this ecologically friendly method of powering the boat, with a different ecologically friendly method of powering the boat so you may travel just 20nm per day?

    Why?

  5. #5
    Join Date
    Dec 2008
    Location
    Now cruising in the SUN! On my way to Malta.
    Posts
    1,058

    Default Re: Solar electric cat

    Quote Originally Posted by Parker View Post
    I am removing the sailing rig to make this a power cat powered by the sun. Using a water generator would reduce efficiency as I would be using electricity to move the boat to generate electricity. I may add a wind generator, though.
    Hi Parker,
    I see it differently:
    - You are using your battery power to move the boat at say 7 kts which uses for example 10 Amps of battery power.
    - By utilising a water generator you could at the speed of 7 kts put back 5 Amps into the batteries.
    In my mind this means you are now only using 5 Amps net to move the boat. Am I missing something?
    Roger

    ------------------
    I look to the future, because that's where I am going to spend the rest of my life - George Burns

  6. #6

    Default Re: Solar electric cat

    Hi Tropic Cat,

    I know that it is hard for pure sailors to think about removing a perfectly fine sail from a perfectly fine sailboat, but yes, that is what I am doing. As you may know, many sailors as they age switch from sailboats to power trawlers despite the loud, ecologically unfriendly diesel, just because they can no longer reliably handle the sails in a blow.

    This is my retirement boat, and I am using my engineering skills to be proactive and create my own power cruiser that IS ecologically friendly. The last thing I want is for my wife to grab the wrong line under tension and throw her back out, and proclaim that our cruising days are over! I love the layout and accommodations of the Voyage 440, and she provides the area for a large solar array.

    As to using a water regenerator, there is no such thing as free energy. By dragging a water regenerator, I would be increasing my drag and therefore increasing my power demand. With the solar panels at full power, 7200 watts, and the motors running, that is 48v at 100-150 amps. Batteries will power the system when the array is not at full power, or when I need more power. The genset will only be needed for overnight passages or extended day cruises.

  7. #7

    Default Re: Solar electric cat

    Quote Originally Posted by multihullsailor6 View Post
    Hi Parker,
    I see it differently:
    - You are using your battery power to move the boat at say 7 kts which uses for example 10 Amps of battery power.
    - By utilising a water generator you could at the speed of 7 kts put back 5 Amps into the batteries.
    In my mind this means you are now only using 5 Amps net to move the boat. Am I missing something?
    Yes. you're definitely missing something! Using the water gen to make 5 amps would slow the boat down. To get the boat back to the speed it was doing before you started generating would require more than the 5 amps being generated.

  8. #8
    Join Date
    Dec 2008
    Location
    Now cruising in the SUN! On my way to Malta.
    Posts
    1,058

    Default Re: Solar electric cat

    Whilst I see this point I was thinking of the latest generation of water generators like the French-built Watt & Sea or the German Sail N Sea. In fact the 8 Volvo Ocean Race yachts are now all being fitted with the Watt & Sea water generators as the VOR guys have found in testing that there is no discernable effect on the boat speed.
    Roger

    ------------------
    I look to the future, because that's where I am going to spend the rest of my life - George Burns

  9. #9

    Default Re: Solar electric cat

    Discernible or not, there has to be an effect on boat speed. You're removing energy from a system, it must have an impact.

    Otherwise, why not have 50 water generators producing more power than the motor is using? Or a hundred? You could motor round in circles, and feed power to the grid!

  10. #10
    Join Date
    Jul 2009
    Location
    currently Columbia/Panama
    Posts
    330

    Default Re: Solar electric cat

    A water generator is essentially an electric motor in reverse. Think of it being similar to an inverter/charger transformer. For a sailing boat, the impact of a water generator is offset because no electrical power is being used to drive the boat, so the electrical power is stored in exchange for power from the wind. For an electric motor boat, any power produced by a water generator will be consumed by the propulsion system to generate it. It is zero-sum, or very close to being so.

    There is no free lunch here - the first law of thermodynamics still holds.

    Mark
    Mark Cole
    Manta 40 "Reach"
    www.svreach.com

  11. #11

    Default Re: Solar electric cat

    Wow. Interesting project for sure. I would hope there will be some pictures as you progress?!?

  12. #12

    Default Re: Solar electric cat

    Quote Originally Posted by colemj View Post
    A water generator is essentially an electric motor in reverse. Think of it being similar to an inverter/charger transformer. For a sailing boat, the impact of a water generator is offset because no electrical power is being used to drive the boat, so the electrical power is stored in exchange for power from the wind. For an electric motor boat, any power produced by a water generator will be consumed by the propulsion system to generate it. It is zero-sum, or very close to being so.

    There is no free lunch here - the first law of thermodynamics still holds.

    Mark
    If it were zero sum, you'd have perpetual motion. It's less than zero sum. The power generated will be less than the power required to produce it.

  13. #13

    Default Re: Solar electric cat

    As a former Physics teacher and mechanical engineer, it is nice to see the "no free lunch", need to obey the laws of thermodynamics discussion around the negative gains of dragging a water generator. Wile E Coyote could power a sailboat with a fan blowing on the sail, but putting current into a wind generator and aiming it at a sail would be a similarly frustrating endeavor.

    I am sharing my work on my Facebook page, https://www.facebook.com/profile.php?id=100012560735968

    Search for daveonindigolady@gmail.com

  14. #14

    Default Re: Solar electric cat

    Amazing thing is, some otherwise sensible people really do seem to think there's some kind of magic to electric motors. People seriously claim that having one motor generating with the other producing propulsion while under sail, will result in a boat sailing faster..

  15. #15
    Join Date
    Jul 2009
    Location
    currently Columbia/Panama
    Posts
    330

    Default Re: Solar electric cat

    Quote Originally Posted by 44C View Post
    If it were zero sum, you'd have perpetual motion. It's less than zero sum. The power generated will be less than the power required to produce it.
    It wouldn't be perpetual motion because two independent sources are involved - just perfect efficiency from the sources. I was ignoring the inefficiencies to make the general point that there can never be a gain - only a wash at best.

    Mark
    Mark Cole
    Manta 40 "Reach"
    www.svreach.com

  16. #16
    Join Date
    Oct 2008
    Location
    Port Canaveral Florida
    Posts
    708

    Default Re: Solar electric cat

    Quote Originally Posted by Parker View Post
    Hi Tropic Cat,

    ..... This is my retirement boat, and I am using my engineering skills to be proactive and create my own power cruiser that IS ecologically friendly. The last thing I want is for my wife to grab the wrong line under tension and throw her back out, and proclaim that our cruising days are over! I love the layout and accommodations of the Voyage 440, and she provides the area for a large solar array.

    ...... With the solar panels at full power, 7200 watts, and the motors running, that is 48v at 100-150 amps. Batteries will power the system when the array is not at full power, or when I need more power. The genset will only be needed for overnight passages or extended day cruises.
    Ahhhh, understood. An admirable objective. How would one go about mounting the equivalent of 30 x 250 watt panels on a Voyage 440? And would that be enough to power her?

    Was it the Lagoon 420 that had the electric drive? After struggling with it for a couple of years Lagoon gave up, but your approach with Kilowatts of solar is much different.

  17. #17

    Default Re: Solar electric cat

    7200 Watts is only going to provide enough power to motor slowly. It's about 10hp. And that would be if you used all 7200 Watts, (assuming your solar array actually achieved that, which would be infrequent) and would leave nothing to put in the batteries.

    IMO a better plan for a "geriatric boat" (no offence) would be to get rid of the mainsail and boom, but keep the headsail on a furler. There will be times when there's a nice following breeze, where just a headsail would allow easy miles, and allow the solar array to charge the batteries instead of producing a barely adequate amount of propulsive power.

  18. #18

    Default Re: Solar electric cat

    Hi 44C,

    Yes, the solar array will be a low-power cruising source, but that is why I have invested in a 16 KWH battery bank to supplement day cruising. The gensets are for extended runs or adverse conditions. I did consider keeping the genoa, as that is easily handled, but opted for the no-mast approach. These cats slide through the water nicely at 5-6 knots with very little power, and as a retiree, slow is OK.

  19. #19

    Default Re: Solar electric cat

    I'm with Parker on this. A mast and head sail will provide some extra push occasionally when conditions are right but it will always shadow some part of the solar array that will compromise the output.

  20. #20

    Default Re: Solar electric cat

    At times, pretty often, a headsail can provide all the push you need. Sometimes more than you need. Far more push than 7 kW can provide. And even a headsail alone can get you upwind reasonably well. 7 kW is going to struggle to push a boat that big into any kind of breeze.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •