Wetdream solar 100% electric Catamaran

[IGBT]

On a monohull, the sail and keel are not only used for propulsion but they help the stability of the boat in seas. I don't really have any experience with cats without sails. I am gonna guess though that they are not self righting if they ever get flipped

 

[Kaz]

I really dig the indigo lady.
I also dig the lightleaf ridged rail mounted solar panels
A person could mount a rail down both sides of any boat and swing the panels up for docking, adjust them for maximum production, or down to be out of the wind as much as possible in a storm.
Theres a tone of refraction out on the water. I think putting panels dead on top is not nearly as important as on land. This thought is purely based on many a day fishing offshore in the Gulf of Mexico, and still getting brown as a biscuit despite being under a large t top all day.

 

[BobR]

Hi
Based on some tests I did during the last weeks with our 38' Beneteau sailboat, I remarked two main things:
-Cruiser sailboat are slow.
-Cruising at low speed require really low power (I've tested 1 kW at 3 knot).

Clearly, instead of beating to windward at an average of 4-5 knot, why not simply go in strait line with a solar Catamaran?
That our conclusion and here is a potential plan:
40-45 ft Catamaran without sails and mast, add 10-12 kW of solar, add 120-170 kWh of battery and there you go.
Everything in 48V to access typical component's.
Here two good examples:

Indigo Lady

I am a retired educator married to a retired chemist/engineer/educator. We will be living aboard our solar electric catamaran for as long as possible.

lisamarchi.com

L

Thread '100% Solar Electric Catamaran'

Jun 4, 2024

I've built a solar catamaran out of a 2000 Gemini 105M sailing cat. Some basic specs:

- 2x ePropulsion Navy 6.0 motors, 6000w each max.
- 16x BlueSun Bifacial 575w solar panels, max output 9200w.
- 2x EG4 100amp MPPT solar charge controllers
- 4x 48v 160ah LiFePO4 batteries
- 2x EG4 5000w shore chargers 120v/240v
- 5000w Inverter
- Starlink Internet
- Openplotter navigation with AIS

I've got two independent setups, motor, battery, chargers and panels. No fossil fuels of any kind on the boat.

Sweet spot is 5.3 knots @ 3200w, max speed is around 7.3 knots @12,000w. You pay dearly for that...

• lborkey
• Replies: 43
• Forum: Marine

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Questions about design:

1-Solar panel qty: I can start with 400W to 600W solar panels and there is place for 16-30 panel on a frame. I think it's a good plan to have a space in the center to let exit the wind and also to have access to clean the panel (see pictures).

2-MPPT qty: From 2 MPPT up to 12 MPPT (or more) what can be the sweet spot? It highly depend of the panels and I thought about a configuration of 3 panels with around 45V Voc for each Victron 150/35 MPPT... or 12 Victron 100/20 for 24 panels or 2 EG4 MPPT for 20 panels or even one Boost MPPT for each panel... There is many choice. What is a the best one?

3-Lightning: What to do about lightning with this kind of giant aluminum antenna over the boat?

4-Power requirement: Based on searches and tests, this kind of 15 000 - 20 000 lbs boat will cruise at 4 to 7 knot with as low than 3-4 kW and up to 10-20 kW. So the power requirement is low. I will still be able to output 40-50 kW, but this is not cruising speed power requirement.

5-Range expect: 100 to 200 nautical miles, not more. Still 100 miles can take 24 hours

6-Expect production: Based on 10kW installed and no shade, I think this will produce between 25 kWh to 60 kWh per day. Right? Let say in Caribbean. Flat orientation is not awesome in winter, but is this realistic?

Below is a rough 3D of a 40' boat with 20 panels of 500W.
Please share your inputs!
View attachment 242721
View attachment 242722

You might enjoy reading this: https://www.proboat.com/2023/05/electric-philosophy/

 

[Bop]

I really dig the indigo lady.
I also dig the lightleaf ridged rail mounted solar panels
A person could mount a rail down both sides of any boat and swing the panels up for docking, adjust them for maximum production, or down to be out of the wind as much as possible in a storm.
Theres a tone of refraction out on the water. I think putting panels dead on top is not nearly as important as on land. This thought is purely based on many a day fishing offshore in the Gulf of Mexico, and still getting brown as a biscuit despite being under a large t top all day. View attachment 243593

Its quite common with Australian yachts (monohull and cats) to have bifacial panels now, mounted out over the water on the arch out over the water between the rear of the hulls to get more generating power than conventional panels- boats (like RVs), are the exception to the 'best cost per watt' rule, you want 'best power generated per square metre' ie high efficiency, even if it costs more...

And to the neighsayers, this isn't exactly a new idea, there are literally dozens of different solar powered cats out there already (including some that are regular ocean going ones), hell, if you got the money, you can buy them straight from the manufacturers, in various sizes...
Sunpower here in Australia has been making them since 2021 (shame about the owner, he's gone crazy, caught the yankee sovcit disease shame, the idea is good...)

Like self charging RV's, they aren't meant to be fast, but comfortable cruisers although the Sunpower 44 can do over 10 knots

Didn't get to go onboard, but I saw it at the Gold Coast boating show where it was on display (three of my favs in the one package- solar, EV and boats lol)


Quite frankly, it's no different to a standard motor cat in windage (oh noes- the roofline is a whole 25mm higher- 'its gunna flip'!!!)

 

[OffGridForGood]

Nordkyn Design - Marine Design and Engineering

Nordkyn Design sits at the confluence of yacht design, marine engineering and seamanship. The site features boat plans and resources in the fields of seamanship, heavy-weather dynamics, design for seaworthiness, marine engineering and marine electrical engineering. It is the home of the...

nordkyndesign.com

 

[yabert]

You might enjoy reading this: https://www.proboat.com/2023/05/electric-philosophy/

Lot of good information and another clear proof that idea isn't preposterous. Thanks to shared.
But, man! Those unprotect/unseal battery box in a boat
The battery box I plan will be clearly sealed.

 

[OffGridForGood]

Plan a generator for back up charging power...

 

[wpns]

The battery box I plan will be clearly sealed.

and vented.

 

[yabert]

Plan a generator for back up charging power...

Not at the moment.
This decision will depend on more consumption tests and the kWh on board.
I mean, if I have battery to move the boat for 24h-48h and 100-200 nautical miles non-stop, why put a generator?

 

[yabert]

and vented.

Absolutely!
Such an evidence that I didn't think about wrote it.

 

[OffGridForGood]

why put a generator?

because things can go bad,
two is one,
and one is none.
need a back-up just in case things go bad.

 

[Bop]

The thing is that the generator doesn't even need to be that big anyway (electric motors higher efficiency means that even a relatively small one will be capable of being a 'backup' power source if required) and would be a good 'safety backup' (same as you see almost all sailing boats having an 'emergency outboat' mount on them...)
'belt and braces' is ALWAYS a good approach when it comes to water vessels...

 

[yabert]

need a back-up just in case things go bad.

'belt and braces' is ALWAYS a good approach when it comes to water vessels...

I admit. I will look at that.
Still, despite no generator, I consider I have ''kind'' of back up:
-Large 10-12 kW array can power the boat. This one in build from 4 to 8 smaller array with 4 to 8 MPPT.
-Two larges batteries (something like 65-80 kWh each).
-Two motors + two drives.

So if a propulsion system is in trouble, I still have one system working.
As I plan this boat to cruise around 100 nautical miles or less at time, I should never be far from continent/islands.

To add, the outboard electric motor of our dinghy should push the Cat few miles.
And I look at catamaran kite sail system who are lightweight and can at least pull the Cat in the wind direction.

 

[Bop]

The biggest issue for me with the 'dual' drive system you are envisioning is it comes back to a single power source- which can have its output severely restricted by bad weather...
The sun...

I would suggest adding a wind genny to the power mix, but having repaired installed on ocean going vessels, they can be a nightmare on boats (especially in salt conditions) with their 'direction' slipring suffering from corrosion issues, and you REALLY need to have one that has both electric AND a mechanical brake on them (not common in the smaller sized ones)- there is nothing worse than the vibration echoing through the hull when you are trying to sleep with no way of turning it off, according to several owners I have dealt with over the years lol

 

[mooresolar]

Good Morning
I am looking to do something like the video below

I may have gas outboard or generator to back it up

 

[yabert]

I have hard time to figured out what is the best efficiency of Victron MPPT.
I mean, what will be the most efficient set up?

24 panels with 4 Victron 150/45?
24 panels with 8 Victron 150/35?
20 panels with 10 Victron 100/20?
16 panels with 8 Victron 150/35?

All data sheet are mark as 98% efficiency peak who let us know nothing about half load or full load efficiency.
About the consumption, each MPPT consume 0.6W to 0.9W. So it's nothing and it's why I would like to learn more about efficiency.
Any input?

 

[yabert]

I have hard time to figured out what is the best efficiency of Victron MPPT

No one have clue about this?

I realize that I first design the 10 kW array on the picture on a 40ft Cat.
Here, on the right, is the same 10 kW array on a 45ft Cat. There is some extra places.



So.... why not 12.5 kW
Same thing in mind, the outer 5 panels, each side, should be able to flip or slide over/under the near panels to reduce drag in a storm.
25x 500W panel is not ideal to connect to X number of mppt.

 

[wpns]

No one have clue about this?

I realize that I first design the 10 kW array on the picture on a 40ft Cat.
Here, on the right, is the same 10 kW array on a 45ft Cat. There is some extra places.

View attachment 245316

So.... why not 12.5 kW
Same thing in mind, the outer 5 panels, each side, should be able to flip or slide over/under the near panels to reduce drag in a storm.
25x 500W panel is not ideal to connect to X number of mppt.

View attachment 245317

There are lots of Victron fans around, probably depends exactly what panels you are talking about, remind us of the details again?

 

[yabert]

There are lots of Victron fans around, probably depends exactly what panels you are talking about, remind us of the details again?

Many details are variable. It's exactly what I try to figure out.
What can be the best set up?
I can start with 16 to 30 solar panels in the range of 400-600W each.
Connect them to 4 to 10 MPPT.

The fix detail are:
16S LFP of NMC battery, so 52V or 58V nominal.
I would prefer to have ''low voltage'' solar set up in the range of 70-100V. So, more MPPT and less panels in series.

 

[Kaz]

Caught the video about solar only fishing boat..

 

[yabert]

Nice! Thanks to shared. Another good example despite his tiny 45 kWh battery.
Clearly, it make a lot of sense to build a solar Catamaran.

 

[yabert]

Now, our big question is we build a custom aluminum catamaran from scratch or we modify an existing catamaran

 

[ULR]

Another data from 40' Soel Yachts.
2.4 kW at 5.0 knot
9.1 kW at 6.8 knot

From Silent Yachts 55 (32 tons Cat)
5 kW at 4.4 knot

6.8 knot sound ''crazy fast'' for me as most cruising sailboat average lower than that... and rarely in straight line.

Look up "hull speed".

Surface waves travel at a speed proportional to the square root of their length.

Displacement hulls create a wave by pushing up water in front of them and pulling it down behind, thus pushing backward on the boat. Your speed is the equilibrium where the backward force from the water matches the forward force of the propultion. When you approach the speed where the length of the wave is twice the length of the hull, adding more power just builds the wave higher and increases the back pressure. You never quite reach this "hull speed" and definitely don't exceed it.

Except:

Planing hulls (e.g. power speedboats) use a LOT of power to climb up the wave and "skip" along the top of it. (You can see this when watching the really fast racing boats, where the stone-skipping effect is obvious - and very dangerous. Some sailboats with lots of sail have semi-planing hulls that can beat "hull speed" by getting a little into planing mode.

Long thin hulls (like some catamarans and trimarans) are narrow and sharp enough to "cut through" the wave somewhat, mostly pushing the water aside and achieving speeds somewhat higher than hull speed. Still, it takes a lot of power to fight this self-generated wave, so you still get a big bump in power requirement as you approach the transition.

====

The most stable orientation of a multihull is upside down. Getting it flipped back over is tough - so tough that some trimarans have hatches on the bottom as an arrangement for living while waiting for rescue - or clear enough weather to try to right it. Righting a capsized multhull with a mast for a lever is doable, and the rigging and stuff survives immersion, so once you're back upright you're back in business (except for any soaked stuff like maps, electronics, ...) RIghting one WITHOUT a mast and rigging for a lever is a job for cranes. Meanwhile, how will your panels work upside down and submerged in salt water, your batteries and electronics maybe ditto, and your props up in the air?

=========

Monohull owner: "The most stable orientation of a multihull is upside down."
Multihull owner: "Yeah. But the most stable position of a monohull is on the bottom."

Multihulls have a VERY good record of bringing people back from ocean disasters alive. (You have to sink ALL the hulls to end up swimming with sharks in the middle of nowhere.) But taking off the mast and sail and installing technology similar to that of the flooding-makes-big-fires EVs looks like a removal of some of of the factors that drive this safety record.

By the way: Electric currents in in the water attract sharks - which have electric sensors to detect muscle potentials and "wound currents" from prey animals. So an upside-down electric boat seems likely to have company for dinner.

 

[ULR]

No one have clue about this?

I realize that I first design the 10 kW array on the picture on a 40ft Cat.
Here, on the right, is the same 10 kW array on a 45ft Cat. There is some extra places.

So.... why not 12.5 kW
Same thing in mind, the outer 5 panels, each side, should be able to flip or slide over/under the near panels to reduce drag in a storm.

Or fold down the sides to an angle, to deflect the wind over the others rather than catch it under them.

This sort of "raised horizontal airfoil" arrangement strikes me as a machine for flipping the boat over in wind and waves.

The wind will typically be at about right angles to the waves, with the waves moving downwind. As a wave crest passes under the boat, he windward side of the boat is lifted as the hull follows the water surface contour, while the wind is concentrated at the wave crest. It gets under the panel assembly and blows it upward. If it is strong enough to significantly lift that side of the boat, the area exposed is increased, in a positive feedback that ends in a flip-over.

 

[yabert]

Long thin hulls (like some catamarans and trimarans) are narrow and sharp...

Yes, it's our plan. We find a 45' Cat with ''performance'' hulls who are only 32-33'' wide at waterline.
Seem really narrow as I compare with performance cat like Mumby 48' who is 46'' wide (pic).

Thanks for all other comments. They will be precious for final design.