Is it a bad idea to be ENTIRELY dependant on renewable energy on my 45' trimaran?

[a64pilot]

General question,

Are AC motors more efficient? If so, enough to offset the efficiency loss of an invertor, or can they be run on pulsed DC?

Either way at motors this big, aren't high voltages more efficient, as in hundreds of volts?

Do BIG DC generators even exist?
Would it be better from an Engineering perspective to run a boat like this on AC?

Where has Sailor Chic been, I've seen mor than one post I figured she would be all over, but no word?

[44'cruisingcat]

Originally Posted by FloatingDutchMn

First, let me provide some context. I'm considering having a customised Neel 45 built for my future long distance cruising, which should eventually include Europe to West coast US via the Northwest Passage. The choice of boat is not the point of this post.

I'm seriously considering having an electric saildrive engine (15 kW Oceanvolt) instead of a diesel engine (not too radical so far), but also not to have a diesel generator at all. Thus, I will be entirely reliant on energy being generated by the 2x wind generators, 2kW solar panels and 2x hydro generator.

The weight saving by not having a diesel engine (200kg), diesel generator (100kg) or diesel & tank (350kg) allows me to have 400ah 48Vdedicated battery bank for the propulsion and a 1000 aH 12V battery bank for the household items and still be 200kg lighter. With an inverter, I can run AC, dive compressor, etc.

With this set up, the only time I can not generate power to recharge batteries is on windless nights, foggy days, either at anchor or if the vessel can not go at least 3 knots (which a trimaran will easily do in a 6kt wind).

A slightly less radical approach would be to have a diesel generator to have instant power if needed, but negates the objectives, or to have a methanol fuel cell as an option.

The up front cost is considerably higher, mainly due to the cost of Lithium batteries, which are not coming down as fast as predicted. But, for being totally energy independent, and thus avoiding very expensive marina fees just to plug in to recharge, as well as hardly any maintenance costs (compared to diesel), this in the long term should reduce the total cost difference.

So, the feedback I'm looking for from the forum members, especially the experienced long distance cruisers, is the pros/cons/challenges that will come with this type of system.

Thanks,
Floating Dutchman

You need far more than 2 kW of solar. If you're also planning on using solar/wind for cooking and hot water, your 2 kW solar and wind generators will barely cover your house needs.

JMO, but to me the best way of having a vessel that is truly entirely powered by renewable energy is to build an extremely efficient sailing boat, one that can sail in virtually no wind.

[Cadence]

Originally Posted by a64pilot

General question,

Are AC motors more efficient? If so, enough to offset the efficiency loss of an invertor, or can they be run on pulsed DC?

Either way at motors this big, aren't high voltages more efficient, as in hundreds of volts?

Do BIG DC generators even exist?
Would it be better from an Engineering perspective to run a boat like this on AC?

Where has Sailor Chic been, I've seen mor than one post I figured she would be all over, but no word?

Ac motors have on and off. Deisel electric is DC, giving infinite speed control. Elevators are probably
still using a Ward Lenard system. The whole discussion doesn't seen relevant to the OP?

[a64pilot]

AC motors are easily speed controlled, relevance is I think at some point AC power becomes more efficient, high voltage smaller wires etc. All bigger aircraft run pretty much everything off of 115VAC, three phase and 400Hz, because weight matters in an aircraft as I assume it does here.
My Prius traction battery is a little over 200V and it's motors are AC, both I believe to increase efficiency, been safer to stay low voltage DC
I assume the OP is after both light weight and efficiency, will probably need a BIG genset to provide direct motive power if and when necessary and I assume BIG AC gensets are far more available than DC.

So at what point does a high voltage AC boat become more feasible and efficient than a low voltage DC boat, or does it?

[Arthur Garfield]

You could easily go 100% renewable for getting on/off ball or in/out of a marina with DC motor powerred by batt. bank. The real trick is a sizable electric motorring distance off shore.The lith/ion batts may show some light over time.

"Serial hybrid" system comes closest now.

There are custom made diesel gensets in DC of the permanant magnet flavor up to around 80kw DC.Spendy,Very.

Upside is these diesel gennys are "variable speed" and produce FULL prop thrust at very low RPMs with highly efficient DC prop turning motors.Very Very efficeint.
Additionally,these DC propulsion prop turning motors easily double as generator(s) when under sail.These not entirely efficient but eliminate upwards of %90 prop drag also !

The custom controllers quite spendy to make genset variable speed run in the $5k range.This tech has not been entirely proven.


All the Best

[Cadence]

Originally Posted by a64pilot

AC motors are easily speed controlled, relevance is I think at some point AC power becomes more efficient, high voltage smaller wires etc. All bigger aircraft run pretty much everything off of 115VAC, three phase and 400Hz, because weight matters in an aircraft as I assume it does here.
My Prius traction battery is a little over 200V and it's motors are AC, both I believe to increase efficiency, been safer to stay low voltage DC
I assume the OP is after both light weight and efficiency, will probably need a BIG genset to provide direct motive power if and when necessary and I assume BIG AC gensets are far more available than DC.

So at what point does a high voltage AC boat become more feasible and efficient than a low voltage DC boat, or does it?

Whoa! I quit 400HZ three phase? Not saying your wrong and apparently you have an aircraft background but I still can't see the relevance to the OP. Personally I see it as folly but we all have our dreams.
I wish him well and safety.

[snort]

I finished this book a couple of months ago: Amazon.com: The Other Side of the Ice: One Family's Treacherous Journey Negotiating the Northwest Passage eBook: Sprague Theobald, Allan Kreda: Kindle Store

Personally, I'd want every possible energy source and redundancy to get me out of harm's way when the weather gets rough, especially in those waters.

Not to mention getting trapped in sea ice:
Mariner trying to sail Northwest Passage rescued by Coast Guard after sailboat gets stuck in sea ice near Barrow | Alaska Dispatch

[sanibel sailor]

Is it a bad idea to be ENTIRELY dependant on renewable energy on my 45' trimaran?

YES.

Do I get a prize for being the first to answer the question directly?

[dannc]

Originally Posted by sanibel sailor

Is it a bad idea to be ENTIRELY dependant on renewable energy on my 45' trimaran?

YES.

Do I get a prize for being the first to answer the question directly?

And here is your prize....



But if we directly answer the OP's question, how would that be fun?

Later,
Dan

[downunder]

I would be very surprised if you could run a scuba compressor from batteries and inverter.

Small surface supplied compressor yes.

Cheers

[SV THIRD DAY]

Originally Posted by sanibel sailor

Is it a bad idea to be ENTIRELY dependant on renewable energy on my 45' trimaran?

YES.

Do I get a prize for being the first to answer the question directly?

Hey...5 posts in I called it a "crazy idea" and I also accurately predicted that the chat room experts would soon show up to tell him how he could do it...but like My Wife always says...shut up about being right! Now if I can just predict the Horse Races like I can the Chat Rooms!

Originally Posted by SV THIRD DAY

I would like to know this piece of info to help us understand your thinking. Have you cruised before? Have you made extended trips off shore or coastal? Because if you haven't then that helps explain your crazy idea of setting up a cruising boat of that size to just run off wind/solar and luck.

All it would take is one dark and stormy night with dead batteries, no way to power off the lee shore and you would understand why I'm calling it crazy, but then it could be too late.

These type of ideas are often floated by folks without the experience to know just how bad of an idea they really are and in a chat room filled with "I have a better way to do things folks" they will always give you support for crazy ideas just because it sounds cool. But Amigo...unless you want to go cruising on a Science Project then have a diesel generator aboard.

[FloatingDutchMn]

Originally Posted by SV THIRD DAY

I would like to know this piece of info to help us understand your thinking. Have you cruised before? Have you made extended trips off shore or coastal? Because if you haven't then that helps explain your crazy idea of setting up a cruising boat of that size to just run off wind/solar and luck.

All it would take is one dark and stormy night with dead batteries, no way to power off the lee shore and you would understand why I'm calling it crazy, but then it could be too late.

These type of ideas are often floated by folks without the experience to know just how bad of an idea they really are and in a chat room filled with "I have a better way to do things folks" they will always give you support for crazy ideas just because it sounds cool. But Amigo...unless you want to go cruising on a Science Project then have a diesel generator aboard.

Perhaps this is a crazy idea, perhaps not. Until the system design is analyzed and the pros and cons are evaluated and put into context of the risks and quantified, then it is an idea, no more, no less. It is very easy to shoot from the hip and label something as crazy. I'm in the process of doing a lot of homework, this forum is just a small part of it. I value the eloquent and intelligent contirbutions, irrespective of the content being in support of my idea or writing it off as crazy.

The contributions so far have underlined my own personal reservations. An electric propulsion system without a generator is just not a sensible thing to do, even for "normal" cruising, let alone for the NWP.

And the NWP is what is driving my thought process. A steel or aluminium monohull is the most sensible thing to do, diesel engine, 1000L tank, plus solar/wind/hydro for the house battery bank. Trying to do it in a GRP trimaran starts to raise a lot of questions. The obvious one is the suitability of the width in negotiating ice floes, but that is a discussion for another post. As has been pointed out, a lot of motoring is required through the NWP. A diesel engine's range is limited by the amount of diesel the boat carries. So, more range, more diesel, more weight. more weight is always an issue on yachts, but more so for catamarans and trimarans, as their speed performance dramatically goes down if they are overloaded.

So, lets say a range of at least 1000miles on engine only is desired for a NWP attempt. Between engine and diesel, thats at least 1,300 kg. Within this weight range, I'm looking for a system that can achieve the same range but at less weight if possible, hence an electric engine, or some hybrid system.

It is easy to call an idea crazy. But I'm not crazy, the psych ward that released me said so.

[downunder]

Torquedo has developed a whole system that it is currently running on a Gunboat catamaran.

Worth a look.

Deep Blue Hybrid, hybrid propulsion system, sailing catamarans

http://www.moonwave-systems.com/

Cheers

[FloatingDutchMn]

Originally Posted by 44'cruisingcat

You need far more than 2 kW of solar. If you're also planning on using solar/wind for cooking and hot water, your 2 kW solar and wind generators will barely cover your house needs.

JMO, but to me the best way of having a vessel that is truly entirely powered by renewable energy is to build an extremely efficient sailing boat, one that can sail in virtually no wind.

The size of the solar system is just an estimate at the moment. The Neel 45 has an enormous roof for solar panels, which is one of the reasons I'm considering this boat.

2kW may not be enough, but here is my calculation. 2kW solar array. Lets say that due to shading, wrong orientation we only get 50% efficiency (question: too optimistic) and to be conservative, we only get 3 hrs of useful sun in a day, so that means we generate 3000kWh in a day, which for 12V bank is 250aH... That is the low end of the system, also assuming no contribution from wind or hydro, which I agree, just about covers daily consumption of household, not including hot water or cooking. However, if this is on the low end, then on long sunny days the total energy creating can be significantly higher.

[downunder]

The moonvave hybrid system now owned by Torquedo seems closest to your needs.

Electric hybrid propulsion system for catamarans and sailboats

If you can afford a new Neel should be able to handle the cost of this system.

The beauty of it is its a fully integrated system including solar, genset ,battery banks and controllers and motors.

cheers