Lagoon 420 hybrid + modern tech

[visscher]

So what you are telling me is that you didn't spend $4850 on 12,000 w of solar panels and take your home in town off the grid but you looked into it for a cabin out of town and what works for others is considered kool-aid?





Interesting note. I will actually be in Matthews Ridge Guyana this spring. The town outside of Georgetown where Jim Jones and his followers drank the kool-aid at their compound.

[44'cruisingcat]

Originally Posted by visscher

Unless someone brilliant came up with 14kwh batteries that weighed 200lbs each. All you need then is enough batteries to power motors for 24 hrs and enough solar panels to fill those batteries between 10-3. .
.

Yep that's right. So to run a 14 kW motor for 24 hours we only need 4800 lbs of batteries. If you're happy to cycle them through 100%.

Then to fill them back up in the daytime we only need to harvest 336 kWh in 5 hours, so 67.2 kW of solar panels.

If solar panels were 100% efficient we'd only need ~68m2 of them. But since they're more like 20% efficient, we need 336 m2.

So, 4800 lbs of batteries (5760 lbs would be better) plus 336m2 of solar panels...


Piece of cake on a boat, right?

[StuM]

Oh boy, we've just got another idealistic EP evangelist on board.
Where do they keep coming from?

Hang on while I get the...
Visscher, you may like to do a forum search here on electric propulsion. All the pros/cons have been debated here ad nauseum over the last couple of years.

[cwjohm]

No problems with a factory provided there is plenty of space.

Little problem however, that the cost per Kwh only works when government subsidies apply, and then there is the slight problem of a week of very bad weather when very little solar input takes place - as any South Australian will attest.

I suspect Musk may have a problem with DT gets in and all of the government handouts cease.

The Powerwall is another step in a very long journey to getting the storage cost per Kwh to a level where costs are justifiable on a standalone basis. In the meantime baseline load be it via coal/gas/nuclear on land and diesel on boat will remain key.

[StuM]

Originally Posted by visscher

How many 2170 cells do you need now to run a boat for a day? Does it weigh more than 400 lbs?

Since you ask a specific question (albeit with a lot of implied assumption) which hasn't been specifically answered here before:

A 2170 cell supposedly is about 5.75Ah at around 3.7V which means it stores approximately 21Wh.

It's hard to get a weight figure, but based on a comparison with the 18650, it should be around 65g.

Now, since we are talking about propulsion, I assume by "run", we are talking about motoring at a reasonable cruising speed and by "day" you mean 24 hours.

If I am prepared to take it slow, I can go about 5 knots in calm conditions on about 10 HP, so lets go with that. Let's make that 7500W in round figures.

So for 1 day, I need 180,000Wh. Which is about 8,570 of those 2170 cells; they will weigh about 557,000 grams or about 1,200 lbs.

So the answers to your question are:
8570 and Yes, about 3 times more.

[cwjohm]

Since you ask a specific question (albeit with a lot of implied assumption) which hasn't been specifically answered here before:

A 2170 cell supposedly is about 5.75Ah at around 3.7V which means it stores approximately 21Wh.

It's hard to get a weight figure, but based on a comparison with the 18650, it should be around 65g.

Now, since we are talking about propulsion, I assume by "run", we are talking about motoring at a reasonable cruising speed and by "day" you mean 24 hours.

If I am prepared to take it slow, I can go about 5 knots in calm conditions on about 10 HP, so lets go with that. Let's make that 7500W in round figures.

So for 1 day, I need 180,000Wh. Which is about 8,570 of those 2170 cells; they will weigh about 557,000 grams or about 1,200 lbs.

So the answers to your question are:
8570 and Yes, about 3 times more.

You need to allow for packaging of the 2170 cells. A better way to look at it is to equip powerwall 2 units with peak capacity of 14Kwh, so working your math you would need 13 units (oops, you can only run 9). This would mean about 5 times more weight.

Not that anyone would be happy to puddle along at 5 knots in perfect conditions, and in imperfect conditions you may go backwards.

[visscher]

Sweet! My grandpa makes the same arguments about things that have evolved in his old age. First guy makes an argument based on redlining a motor which would propel you 4x faster than a sailboat averages, and another makes an argument which is basically nothing new can come under the sun Instead of understanding the tech, it's limitations and the areas of efficiency needed to get performance to where it would match what you already have. Good for you folks!

[44'cruisingcat]

Well yes. When they can fit 10kW hours into a 1kg battery, and solar panels are 1,000% efficient, using oil will be stupid.


Today, it's not.

[cwjohm]

Instead of understanding the tech, it's limitations and the areas of efficiency needed to get performance to where it would match what you already have. Good for you folks!

Given that you have not made one technical argument in favour of the tech this statement is illogical. Perhaps your grandpa know the technology better than you do.

[Stumble]

Originally Posted by visscher

Sweet! My grandpa makes the same arguments about things that have evolved in his old age. First guy makes an argument based on redlining a motor which would propel you 4x faster than a sailboat averages, and another makes an argument which is basically nothing new can come under the sun Instead of understanding the tech, it's limitations and the areas of efficiency needed to get performance to where it would match what you already have. Good for you folks!

You really don't understand physics do you? Current battery technology is about 2% as energy dense as diesel when you account for efficiency and heat loss. Current battery technology is at roughly 30% of the maximum theoretical capability, at which point every atomically slot for electrons would be filled and you can't physically add anymore.

So even if you could build a battery with today's technology that is at the very maximum of the physical limit it would only be 6% as energy dense as diesel fuel.

You simply cannot stack enough solar panels on a sailboat to substantially add to the cruising speed under power. There are thread after thread dealing with this, but basically for every three hours of motoring it takes a day to recharge the batteries, given a reasonable size solar system.

The physics simply do not work. And compounding this is the fact that sailboats burn minimal amounts of fuel even over their lifetimes. It simply isn't cost effective to spend a massive amount on a solar system to offset a minimal amount of cost.

But I would be happy to be proven wrong, just please show your work and reference material.

[StuM]

Hey visscher,

Since you seem so sure that it is feasible, how about giving us the suggested specs and projected performance figures for say a 40ft cruising sailboat.

Or maybe just describe what you see as the tech, it's limitations and the areas of efficiency needed to get performance to where it would match what such a sailboat currently has with an average sized diesel auxiliary.

[adoxograph]

Look at this baby: https://phys.org/news/2016-09-green-...ld-voyage.html

They are not stuck in their paradigms.

Or this one: It has already been done in 2012:

"MS TÛRANOR PlanetSolar (Switzerland) circumnavigated the world in a westward direction from Monaco in 1 year 7 months and 7 days from 27 September 2010 to 4 May 2012 on solar power only. The boat had accumulated 32,410 nautical miles (60,023 km; 37,296 miles) on its arrival in Monaco".

Here some specs

"The MS TÛRANOR PlanetSolar, a 31-metre-long and 15-metre-wide catamaran, is powered by a 537 m² (5,780 ft²) photovoltaic solar generator. Batteries are charging during the day and discharging during the night through the propulsion that is composed of 2 semi-submerged propellers driven by 4 engines. Only solar energy is used during the world tour."

ok this one is not what I would call a beauty



PS: Is there a tongue in cheek emoti somewhere?

[StuM]

Some other specs:
93kW of solar panels
8.5 tons of lithium-ion batteries
€15 million cost.

[Stumble]

Originally Posted by StuM

Some other specs:
93kW of solar panels
8.5 tons of lithium-ion batteries
€15 million cost.

And in her 'record breaking' trans-Atlantic crossing she averaged 5.11kn, or about 122nm/day. So for just $15m you too can cross an ocean at about the same speed as a 35' sailboat.

The course record for their route on a sailboat is a little over 8 day.

[Vander Woestijn]

The back and forth on here has been informative but confusing as well. I am a couple of years away from getting me own cat hopefully; most probably a Lagoon 40-50 range. I am really trying to consider the hybrid option, but it has not been a convincing argument thus far.

Found this impressive 24 hour simulation video of the so called "tesla of the sea" cat, running continuously while using some appliances. It looks great on the graphic, but the propulsion power is not up there.. forget about windy conditions or waves above 3 feet.. and hence the compromises everyone here has been talking about.. not to mention this cat's Eur 2.5 mil price tag!

https://youtu.be/PBwLVvll-lk