Solar sails and the future of hybrid cats

[44'cruisingcat]

Originally Posted by ssmoot

Nobody suggested that. Just that if you're only going to use 20hp on your 57hp motor because you keep it at 2,000RPM or less because it's silly to burn twice the fuel for 15% extra boat speed, it's not unreasonable to suggest you should be looking at a 20hp electric motor.

But if you're not willing to entertain that idea, then there's really nothing to discuss. Stick with diesel, this particular electric setup isn't for you clearly.

Maybe you'd be interested in a much larger one, but I'm sure Oceanvolt's pricing would be exorbitant, so unless you're willing to DIY (where you could easily get a 120hp electric motor for a few thousand dollars, but then you need a high voltage battery pack for $5K to $15K as well), you're probably going to be waiting for another 5 to 10 years at least I imagine.

The OP STATED exactly that. A 15kw electric is equivalent to a 45 HP (33kw) diesel.

But if you want to compare running an electric motor at full power to running a diesel at some arbitrary (but low ) throttle setting, then such comparisons are meaningless.

A 200 HP diesel probably only makes about 15 kw at idle....

[44'cruisingcat]

Originally Posted by ZULU40

look you want to try that **** do it with someone else
be advised
Im not easily humoured by nonsense or the moronic

Ooh scary.

Perhaps you'd need to be moronic to believe oceanvolts nonsense?

[seandepagnier]

Originally Posted by Paul Elliott

Electric motor efficiency is about 90%
Diesel engine efficiency is about 45% (best-case, not allowing for transmission losses. Perhaps 25% overall, at cruising speed?)

Thank you for the apple and orange comparison. It means very little.

The typical diesel is maybe 25% efficient at converting fuel into kinetic energy. ok

The electric is 90% (sometimes better, sometimes much worse) efficient at converting electrical energy to kinetic energy. Not fuel. The diesel engine can't use electric energy. This efficiency comparison is not the same thing at all.


Let's make an actually fair comparison by looking at the primary energy source the sun.

1) The solar panels are 15% electric motor can be 90% = 13.5% efficient
2) using optimistic (maybe possible in future) 10,000 gallons fuel per acre production (corn is around 450) is 3.2% efficient and engine 25% = 0.8% efficient


It's not even close. There is really no reason to discuss using diesel at all unless you like to be wasteful and selfish and spoil everything. In fact it was proven since ancient times you don't need it at all.

This doesn't even include losses transporting the fuel.

If you use ancient fossil fuels the efficiency is _much_ less, as there is extensive cost in drilling, and refining, the overall efficiency (from the sunlight) is below 0.01%

3) The sculling oar is 85% efficient and the human 20% efficient = 17% efficient, even better than electric. no wonder I don't use electric anymore.

[ZULU40]

Originally Posted by Thalas

You actually bring up an interesting idea. Just as the electrification of cars will accelerate the increased production and lower cost of lithium storage solutions, I wonder if electric motors and controllers will see similar benefits. Marine diesel design is significantly different than its land based cousin, but how different is a Tesla Model 3 electric motor from an Oceanvolt? Probably not much.

electric cars certainly
where the power requirements will be similar, and the systems designs are already well known. And where 3rd string suppliers are keynote to the efficiency of the auto industry.

but also in defence
virtually all of Europe use diesel electric submarines, whom by no coincidence are the largest manufacturers of same. Any new submersible will be looking for the advantages new battery tech will bring, not the least of which in improved submerged range, and the higher energy release for the prized 'dash speed'. The same industries have been into air independent engines like Stirlings for 30 years.

Dash speed is the maximum speed a sub can endure in expending its entire battery in one hour. The promise (which is most secret everywhere) new tech offers is speeds exceeding that of the surface vessels attempting to pursue it.

DE subs are the hidden killers of nuclear submarines, and their presence replaces 10 or more vulnerable warships and all they cost. When it comes to nuke subs, their (DE subs) value is inestimable.

[ZULU40]

Originally Posted by boat_alexandra

Thank you for the apple and orange comparison. It means very little.

The typical diesel is maybe 25% efficient at converting fuel into kinetic energy. ok

The electric is 90% (sometimes better, sometimes much worse) efficient at converting electrical energy to kinetic energy. Not fuel. The diesel engine can't use electric energy. This efficiency comparison is not the same thing at all.


Let's make an actually fair comparison by looking at the primary energy source the sun.

1) The solar panels are 15% electric motor can be 90% = 13.5% efficient
2) using optimistic (maybe possible in future) 10,000 gallons fuel per acre production (corn is around 450) is 3.2% efficient and engine 25% = 0.8% efficient


It's not even close. There is really no reason to discuss using diesel at all unless you like to be wasteful and selfish and spoil everything. In fact it was proven since ancient times you don't need it at all.

This doesn't even include losses transporting the fuel.

If you use ancient fossil fuels the efficiency is _much_ less, as there is extensive cost in drilling, and refining, the overall efficiency (from the sunlight) is below 0.01%

3) The sculling oar is 85% efficient and the human 20% efficient = 17% efficient, even better than electric. no wonder I don't use electric anymore.

I can make this simpler
The goal is travelling to a destination point to point for much reduced costs vs whatever the combined fuel/maintenance costs you right now.

Add to that manufacturers will welcome yet another division in the coming sailing fleets, for which power boats are most closely disposed. Now think of the charter market, from which most cats are designed to dispose.

BTW I think solar panels are within a few years of making a leap to 33% efficient

[Dave_S]

Originally Posted by ZULU40

I think we aren't there yet, but technological advances in solar generation and air independent engines appear to be such that, I am expecting that somewhere in the not to far distant future there will be boats with a 100% reliance on electric generation. It is simply a matter of time.

Sadly I don't think we can get there. Even extracting 100% of the sun's energy and electric motors at 100% efficiency we won't be able to travel 24hrs a day without additional power.

[Thalas]

Originally Posted by Dave_S

Sadly I don't think we can get there. Even extracting 100% of the sun's energy and electric motors at 100% efficiency we won't be able to travel 24hrs a day without additional power.

You're absolutely right. This will never be a solution for sailors who motor most of the time. But how many potential miles could be added to an appropriately scaled battery bank each day with 3kw of solar input? Many sailors use the wind most of the time and are at anchor for days between travel where a bank could be recharged. If I knew that I could add 200 miles of potential travel to the bank each day I was charging for 8 hours, it would be very attractive. That doesn't even factor in hyrdogeneration while under strong wind sailing or actually using the 11KW genny to recharge the bank in a pinch.

People keep arguing about electric vs diesel HP when the only real metrics should be travel speed and duration under motor. Tesla owners don't argue about HP conversions when their cars do 3 second 0-60. Say for Caribbean and Med cruising, what would the range need to be at 6kts of speed where people would feel safe going all electric?

edit: to be fair, the potential 3kw solar input would only be viable when the 2kw solar sail were raised while sailing. At anchor, one would be much more limited to the 1kw input of a more traditional hard solar array. Though maybe a solar fabric sunshade covering the tramps and front recreation area would make up the difference.

[StuM]

Originally Posted by ZULU40

Add to that, you wouldn't have an IC engine which you intended to run flat out all the time, the useful torque the engine is required to extract is a long way from zero RPM, but for electric motors this is closer to normal operation.

If I understand you correctly, you are saying that an electric motor on a boat is generally operated at very low RPM. Is that correct?

[44'cruisingcat]

[QUOTE=Thalas;2493128

People keep arguing about electric vs diesel HP when the only real metrics should be travel speed and duration under motor. Tesla owners don't argue about HP conversions when their cars do 3 second 0-60. [/QUOTE]

They don't need to. Their cars have around 500 kw motors and 4 wheel drive. They're not fast because of magical electric superhorses.

[picklesandjesse]

This being said, I got rid of electric power for practical reasons. It still makes a hum noise, and it's makes you lazy. I found the sculling oar is a true solution offering speed of 2 knots plus current. It makes you more fit and strong so you can live long. So, electric is dumb, and so are propellers.[/QUOTE]

So do you scull your 27ft boat ??? I might be interested in having a go. Like the idea of staying fit. I always row even though I have a 2hp motor.

[Thalas]

Originally Posted by StuM

If I understand you correctly, you are saying that an electric motor on a boat is generally operated at very low RPM. Is that correct?

Looks like RPM is roughly 2200 on the electric motors though not sure if that's cruise or max.

Side note, two electrics would weigh 188lbs vs 912lbs for 2 Yanmar Diesels (724lb difference). Curious what the weight difference would be between 250 gallons of diesel (7lb/gal = 1,750lbs) and an appropriately scaled battery bank. ReLiOn makes marine grade steel case 48V 300AH LiOn packs that weigh 375lbs each. So 1200AH 48V would weigh 1,500lbs. Granted, that's not enough and diesel tanks aren't always full meaning the weight fluctuates, but interesting to look at.

[ssmoot]

Originally Posted by 44'cruisingcat

The OP STATED exactly that. A 15kw electric is equivalent to a 45 HP (33kw) diesel.

But if you want to compare running an electric motor at full power to running a diesel at some arbitrary (but low ) throttle setting, then such comparisons are meaningless.

A 200 HP diesel probably only makes about 15 kw at idle....

If what you want to claim is that for you, WOT performance is your primary motivator when sizing diesel propulsion that's great. For you.

I think Oceanvolt's claims are a lot closer to the mark for me than yours though if that's the case.

In general, I think they're overpriced, and may be overstating a bit in their marketing, but I do think the cruising-speed load number is a lot closer to 20hp than 45hp as a rule of thumb.

Regardless, I'm not sure what your point is except to insinuate you don't think 20hp is good enough. If that's the case, don't buy it? If other people are motivated more by finding the system that provides a comparable cruising speed minus the noise and vibration, but with the much bigger battery, why is that a problem for you?

[Dave_S]

Hi Thalas

I'm above my pay grade here - so happy to be corrected.

Looking at a V-LFP-48-50R battery - first one I found, there will be better ones - Fusion AGM Batteries > Products > Product List

it has 2.4kwh capacity.

You need 365kwh total for 33hrs travel
Less - 48kwh from your sails and panels assuming you get 2 x better than perfect 8hr periods in your 33hrs travel

= 317kwh of power storage needed to travel 200nm at 6kn means you need 132 batteries at 33kgs each this equates to a little over 4.5t and 3 cubic meters of space with the cabling housing etc.

It will take 13 perfect days to recharge on solar or 28hrs on your generator.

None of this takes into account your house power usage.

[Dave_S]

Originally Posted by Thalas

ReLiOn makes marine grade steel case 48V 300AH LiOn packs that weigh 375lbs each. So 1200AH 48V would weigh 1,500lbs. Granted, that's not enough and diesel tanks aren't always full meaning the weight fluctuates, but interesting to look at.

A much better battery than the one I found but still probably 4t You will need 22 of those packs 8250lbs

AND nearly $300,000.00

https://carolina-energy-distributors...-ion-batteries


EDIT: I forgot to mention in the previous post that with your sails down you will need nearly 40 perfect days to re-charge on solar.


The batteries you mention will also need over 3 cubic meters of space.

[foufou]

What I haven't seen is the calculation of replacement of batteries az part of the fuel costs. It's not a trivial number in all likelihood