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Old 26-04-2010, 10:15   #1
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100% Solar-Powered Boat - How Would You Build it ?

We are in the very early stages of a project to help bring more awareness about the benefits of solar power (to Thailand and the world). We're wanting to see if it's possible to power a boat, around the world, non-stop, on just PV modules (no sails or wind generators).

If you were converting an already built 36'-40' cruiser (monohull or catamaran) into a completely electrical powered cruiser, how would you do it? Would you suggest a monohull or a catamaran? (All my experience is monohull but if a cat works better for this application then I can adapt.) Would you build the solar array above the boat (ala SolarWave) or attach the modules to the deck and where the trampoline is located? Which electrical engine(s) should we be considering for a 23,000nm endurance marathon like this? Any other suggestions (weather-proofing the PVs, batteries, etc.)?

To help get the brainstorming started, here are pics of the solar powered cat that recently crossed the Atlantic.




Using our connections here in Thailand we are 100% certain the necessary PV panels (24x210w panels, for a 5kw generator) will be donated along with most of the electrical equipment (batteries, converters, etc.) needed. After this project is completed, the entire array will be removed and moved to our Learning Center in northeastern Thailand, where it will help power our school and recycling center. The boat will be refitted for sailing and sold (if possible).

Thank you for any input and advice you can provide us.
Kirk
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Old 26-04-2010, 11:54   #2
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With a 5KW maximum solar power generating ability you will see something like 20KWH of power in a day. If you are cruising 24 hours a day while at sea, that gives you...an averaged maximum of 833WH of power to run all systems in any given hour of the day. Assuming you power all day and night, rather than lying ahull at night. Ignoring an electrical budget, nav lights versus refrigeration (or not) and all the intermittent power loads, maybe that means 750WH, maybe 700WH are charging inefficiencies...

So, how many pounds of what hull can you propel with what electric motors at what speed, given the amount of power you will have available? Will that much power allow you a vessel that can physically carry that many panels? And survive ocean storms?

(And don't rely on my numbers, I'm not licensed to practice math on the web.)
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Old 26-04-2010, 21:07   #3
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Thanks, hellosailor. I really appreciate the reply. The questions you asked are the ones I've been trying to figure out on my own and haven't had much luck. (I'm not licensed to do math online or offline.)

:-)

We estimated that a 5kw solar array is the minimum amount we could obtain at this moment. If it requires an 8kw generator and 2x8kw engines to propel a boat large enough to handle the array then that's our target. I'm hoping there's an engineer (or two) out there who can help us do some more of this math so we know what to look for when proceeding.

The other solar projects I've been monitoring (link 1, link 2) were all custom built (not conversions of existing boats) and are able to propel a much larger/heavier boat with an 8-10kw generating ability and 8-10kw engines. So I figured if we have a smaller/lighter boat, with a smaller crew, we could get by with a smaller array and engines. Then again, I don't know a lot about the structural engineering involved or if converting an existing monohull or cat is even an option. Maybe that's why all the other solar projects were custom built. ...Or maybe they had the extra money to spend.

Thanks again.
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Old 26-04-2010, 21:45   #4
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hmmm.

Quote:
Originally Posted by hellosailor View Post
Ignoring an electrical budget, nav lights versus refrigeration (or not) and all the intermittent power loads, maybe that means 750WH, maybe 700WH are charging inefficiencies...
So, assuming twin screws on a catamaran, that would mean two 350 watt motors working 24/7.

Hmmm. Don't think I'll be volunteering to crew on that boat. It's going to have to be ultra-light, fully loaded, especially considering the weight of 5kw worth of solar panels and at least 1/2 ton of batteries. No place on this boat for books, musical instruments or toothbrushes.

I don't see how you could make this work with an existing production hull.
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Old 26-04-2010, 21:58   #5
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The weight of the 5kw solar array (just panels) will be about 800lbs. The batteries are definitely the elephant on the boat. It's going to be difficult to compensate for that added weight.

The engines will most likely not be running 24/7. Maybe 22/7.
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Old 26-04-2010, 22:08   #6
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consider the frame

Quote:
Originally Posted by Isara View Post
The weight of the 5kw solar array (just panels) will be about 800lbs. The batteries are definitely the elephant on the boat. It's going to be difficult to compensate for that added weight.

The engines will most likely not be running 24/7. Maybe 22/7.
The frame for those panels is going to weigh as much as the panels themselves. Easily.

And honestly, I would not EVER venture offshore in a boat that had to lay ahull two hours a day. That's totally dangerous. Especially for a multihull.

In my opinion, and I'm not an engineer, there's not enough economy of scale at 5kw to make such a system work.
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Old 27-04-2010, 00:03   #7
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Thanks for the input, Bash.

The 22/7 was a way of saying that there's no way we expect the engines to operate for the entire time, without a break. So they wouldn't necessarily be a consecutive 2 hours/day and definitely wouldn't be done if the conditions outside were not optimal. But giving the engines some idle or down time for maintenance seems like it would be a requirement on a journey this long. I could be wrong since the only electric engine I've ever owned was a golf cart. :-)

The electrical equipment needed is not our biggest concern. Fortunately, our foundation has a lot of support here in Thailand and one PV module manufacturer has already said they will provide us with what we need. We just gave them a preliminary estimate of 5kw and the response was good. So, without knowing for sure, 8kw is "probably" doable. If not, we can maybe find other sponsors who will help take care of the added costs for the 3kw difference.

I'll be the first to admit, what we eventually end up with might not be the most practical, efficient, or safest solution of getting from Point A to Point B (or, in this case, back to Point A), but neither is the motorcycle I get on everyday.

I'm certain there are things we haven't even considered. But, eventually, we will find a solution to each problem and we'll have the right vessel to take us on our journey. Just hoping it doesn't require this much upper-body strength.


Amazing! :thumbsup:

Thanks for all the input provided so far. Please keep it coming.
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Old 27-04-2010, 01:00   #8
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The original question was whether a mono or multi-hull would be more suitable for the task. I'd have to say that a multihull would provide more area for attaching a large array of PV panels. As most replies have stated, lighter is better for your concept craft.

With that said, strictly going electric instead of harnessing all of nature's propulsion methods (think wind as the most economical) is going in the wrong direction, so to speak. Evenings will have you banking on... well, batteries for stored energy. They aren't very green. If you plan on strictly solar power with no bank of storage cells then you will not get far fighting winds and currents at night.

Whatever the case I hope you have fun and maybe develop some alternate energy efficiencies.
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Old 27-04-2010, 01:14   #9
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Making that is going to entail a lot of toxic metals and CO² released..
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Old 27-04-2010, 01:33   #10
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Quote:
Originally Posted by kmason View Post
The original question was whether a mono or multi-hull would be more suitable for the task. I'd have to say that a multihull would provide more area for attaching a large array of PV panels. As most replies have stated, lighter is better for your concept craft.

With that said, strictly going electric instead of harnessing all of nature's propulsion methods (think wind as the most economical) is going in the wrong direction, so to speak. Evenings will have you banking on... well, batteries for stored energy. They aren't very green. If you plan on strictly solar power with no bank of storage cells then you will not get far fighting winds and currents at night.

Whatever the case I hope you have fun and maybe develop some alternate energy efficiencies.
All of the solar/electric boats I am supplying lithium batteries for are multi-hulls. Not sure what that is saying about mono hull boats?

Lithium Iron Phosphate batteries (LiFePO4) are very green. You can't buy a more environmentally friendly battery. No nasties like sulphuric acid or toxic heavy metals like lead, cadmium, etc.
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Old 27-04-2010, 01:41   #11
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kmason - I really do appreciate your reply.

Wind is definitely the way to go.

For now, we are going to see if a completely solar powered boat is possible. Much like how Katie rowed across the Atlantic using only her arms, we want to use only one source of energy to propel us. We might consider using a wind generator for some equipment, but the engines must be powered by the Sun.

If there's a way we can cut down on the amount of batteries used then we'll do it. Most likely we'll create a system in which the engines only run at half power during the night and all electrical equipment are on a priority switchbox to save power. We'll figure these things out as we go.

idpnd - Sure. PV is not the cleanest way to produce energy (wind is our friend) but every alternative fuel has their harmful side-effects. Even the Earth friendly boat, Plastiki, has some not so friendly parts.

It's our hopes that as more unusual solar projects are made, more innovations into the development of better (and cleaner) PV research will occur. Or maybe someone will come up with a completely new solar alternative that hasn't even been considered. Some vampires sparkle in the Sun, maybe that's something to look into. lol

LifeTech - Thank you for the info. I will check out the batteries you mentioned.
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Old 27-04-2010, 02:30   #12
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Be sure to check out the thread on LiFePO4 batteries which has lots of information which will be of interest to you-
LiFePO4 Batteries - Okay Tear Me Apart ;-)

If you want the solar boat to be as light weight and as efficient as possible you will need to use lithium batteries since they weight less than half the weight of lead acid batteries for the same battery capacity.
In addition they are more than 95% charge efficient compared to lead acid batteries which are typically 70% to 80% charge efficient which means with lithium batteries you can use smaller solar panels to charge any given size battery.
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Old 27-04-2010, 05:30   #13
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Very interesting regarding the Lithium Iron Phosphate batteries (LiFePO4). Is this the type of battery that to the lay person is generally referred to as Lithium batteries, similar to what is in my camera and cell phone? If so I wasn't aware that this type was being offered in traditional sizes and shapes that are utilized in marine applications? If this is the case would you be able to provide some comparison data as to how this technology stacks up against the other types lead acid, gel cell, AGM? I.E. cost, life expectancy, ammount of deep discharge/ recharge cycles you can expect, etc.? Also maybe the names of some manufacturers of these types.
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Old 27-04-2010, 05:37   #14
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Thanks for the info, LiFeTech. Some VERY informative posts within that topic. I might be contacting you soon with some questions.

cburger - The link LiFeTech posted has some great information and comparisons (costs, suppliers, cycles, etc). Here is the first page of the topic.

LiFePO4 Batteries - Okay Tear Me Apart ;-)
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Old 27-04-2010, 06:50   #15
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Very interesting regarding the Lithium Iron Phosphate batteries (LiFePO4). Is this the type of battery that to the lay person is generally referred to as Lithium batteries, similar to what is in my camera and cell phone? If so I wasn't aware that this type was being offered in traditional sizes and shapes that are utilized in marine applications? If this is the case would you be able to provide some comparison data as to how this technology stacks up against the other types lead acid, gel cell, AGM? I.E. cost, life expectancy, ammount of deep discharge/ recharge cycles you can expect, etc.? Also maybe the names of some manufacturers of these types.
Where do I start! LiFePO4 batteries are simply superior to lead acid batteries in all the major performance categories. For example
1) Less than half the weight of an equivalent capacity lead acid (LA) battery
2) Can be re-charged from dead flat to more than 90% capacity in only 15 minutes
3) Much much longer cycle life compared with LA batteries. LiFeTech LiFePO4 batteries come with a minimum factory backed warranty of 3 years / 3000 cycles (100% DOD) which ever comes first.
4) Charging efficiency of greater than 95% compared with 70-80% for LA
5) Since LiFePO4 batteries do not contain any nasty chemicals or corrosive acids and they do not produce any flammable hydrogen gas while charging they can safely be built into confined or otherwise unused spaces on a boat.
6) Extremely narrow compact LiFePO4 batteries can be supplied (less than 2 inches in thickness).
7) No such distinction between a "house power" battery and an "engine cranking" battery. High power quality LiFePO4 batteries are equally suited for both applications so the same battery can be used for multiple applications.

Below is the photo of a LiFePO4 battery bank which will power a 55ft racing catamaran which is being converted to electric drive. The battery bank will provide propulsive power for the three electric motors (from Torqeedo Germany) which will power this vessel as well as provide all the house power aboard the boat.
Battery charging will be via solar panels and backup genset.

The data cables connecting the batteries are for battery monitoring/diagnosis from a remote location by computer. Since the batteries will be fitted into quite an enclosed space on the boat they won't allow easy access to check the voltages of the batteries via the battery terminals (batteries will be stacked on top of each other to save space).
Instead a "battery data" outlet will be fitted to the instrument panel and the owner of the boat plugs his laptop computer in to check his batteries. He can connect to each individual battery since they are all programmed with unique ID addresses. The information available shows-
1) The internal cell voltages of every cell inside each battery pack
2) Number of total battery cycles accumulated
3) Number of over charge occurrences
4) Number of over discharge occurrences
5) Number of over temperature occurrences
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