The rise of electric Boats

[Chotu]

Specification
LOA: 14 m
Beam: 7.5 m
Minimum Draft: 0.65 m
Displacement: 8-10 tons
Electric motors: 2 x 20 kW
Battery bank: 80kW Lithium-ion
Solar panel area: 60 sqm
Range: Unlimited at 4 knots
Max Speed: 9-10 knots
Guest cabins: 4-5 x double
Crew cabins: 2 x single
Complete systems installed: navigation, electrical, air conditioning, entertainment, water etc.
​

These are specs from one of the pages for that 40 footer in Malaysia described earlier. 15kw motors in this setup.

Displacement numbers vs what I saw on the site look pretty optimistic. They talk about every toy and system under the sun on this boat, flybridges, etc. 8-10 tons. I doubt it.

[Simon.Sails]

Silent Yacht does it - but with only an electric engine (plus generator ofc) range is a bit limited. I'm sure SY are terrific for people who don't like to sail and still move around from port to port in silence and comfort. But I'd feel much more constrained than on a sailboat that I mostly sail when there's wind.

[Tupaia]

Originally Posted by Pete7

There are certainly some issues, not least as you point out what happens on day 3 when its been raining and blowing a hooley. Our solution when it happened in August last year was to run up the estuary in Fowey and plug in to the marina and that's with a diesel engine. Propulsion isn't the only problem, heating and cooking are two more.

I agree with your comment of appropriate technology and perhaps we could manage with say a 20hp petrol or bluegas outboard on the stern or a built in bluegas genny to run the boat and electric drive.

I think diesel will be around for a while yet. Whether we can afford to buy it for leisure use after it has been heavily taxed to discourage its use is another question.

Once you introduce cost and taxation diesel wins hands down assuming of course you have an efficient boat in the first place.

The cost of diesel for me over a year tops out at 300 litres (US$300) some years it has been 50 litres. Take 10 years at maximum that's $3000 which doesn't even pay for a lithium house house bank let alone a propulsion bank. $10 a litre is $30000 maybe getting close.

Now I have seen "sailing" boats, multis included filling up with 1000's of litres diesel.

I looked at the ARC results and was astounded by the amount of engine hours to cross the Atlantic.
1 mono and several multis used zero hours but are included in the following averages.

Multis 39.25 hours
Monos A 58.5, monos B 47.61, monos C 54.5 hrs

In terms of fuel used monos typically have larger engines so hours alone don't tell the whole story.

A Swan 66 used 127.5 hours (163hp @ avg 6l/h = 765 l) for 1 crossing!!!
An FP Liapari 129.5 hours (20hp @ 1.4l/h = 180 l)

I like having engines for safety and security but more effort designing "sailing" boats that can sail rather than motor would go a whole lot further in saving the planet than alternative propulsion.

So I am with Sean on this we already have the solution "sails".

[Chotu]

I agree with Sean also. Sails are the answer here. That’s how to have a no or low emission boat

But I still put the capability for carrying 570 liters of fuel in my boat to account for different use cases.

If I wanted to do the great loop, like posted above, or want to stay at anchor and run the generators for a month to have air conditioning, or run heat in the winter without refilling often, I have the capability to fill those tanks up.

If I want great sailing performance, I can just fill 1/3. But when the sails are put away, I can top off and have the leisure of 570 liters of fuel to supply HVAC or even extended motoring.

[Pete7]

Originally Posted by Tupaia

Once you introduce cost and taxation diesel wins hands down assuming of course you have an efficient boat in the first place.

At todays taxation rates sure, but I have a feeling tax will be the weapon of choice for Governments. It's a bit like One Man and His Dog ('Mericans won't understand so here is a linky)

Governments are going to herd and corral us into choosing environmental green options over fossil fuels, because caring for the environment makes them look good and wins votes. Boris and Gove in our own current Government and possibly the new US administration.

Like you we only use a tiny amount, about 90 litres last year 1/3rd of which was used for heating. I do wonder if buying a new small diesel now and getting 20 years of benefit would be a good idea allowing time for the alternatives to sort themselves out. I just don't want to be the first mouse to the trap.

Pete

[harlem24]

Originally Posted by Adelie

Methanol run thru a fuel cell produces CO2.

Sure, that's why why I stated to use methanol from renewable sources. So the Co2 released is only the one that was used in the production.
If you use fossil sources it's not viable for sure.

[Narfi]

Originally Posted by Chotu

Basically, you need to go through this exercise yourself and start a thread on it. It’s not as easy as asking the question here.

Fair enough
A simpler question perhaps so I can do the exercise myself.
Fully loaded for cruising, how much power do you need to push your boat 5kts? How much power to push your boat 8kts?

[Chotu]

Originally Posted by Narfi

Fair enough
A simpler question perhaps so I can do the exercise myself.
Fully loaded for cruising, how much power do you need to push your boat 5kts? How much power to push your boat 8kts?

30hp for 8 knots with a HUGE but:

The props on a 30hp outboard are not of sufficient diameter to put all 30hp to the water and slip for me as I am approaching 8 knots. It’s 8 knots WOT.

I don’t know what pushes my boat 5 knots. I’ve been fixated on understanding why I can only get 8 knots when the motors clearly have more to give. After a long discussion on here, it was determined that the prop is slipping and unable to put all the power into the water to get me going more than 8 knots.

So, I’m probably not going to bother changing the props for a long time. Too many other things to do. I’ll live with the 8 knots WOT on one 30hp engine and recalibrate with different props sometime in the future.

Oh wait. You said fully loaded for cruising. I don’t have an answer to that. I’ve never been fully loaded for cruising. This is new boat construction.

Engine stuff is basically a dark art. It’s about other boats’ experiences, rules of thumb, trial and error.

[GoneDiving]

Originally Posted by Adelie

Reasonable is in the eye of the beholder. It seems like you are saying your expectations are reasonable which implies that anybody with different expectations are unreasonable.

There are people sailing completely engineless and are quite happy with it. Are they being unreasonable or are their expectations and needs are different than yours?

6kt or whatever your expected cruising speed may be a majority expectation but that doesn’t mean it is reasonable or unreasonable.

I used reasonable to mean satisfactory rather than a moral judgement. There will always be outliers in people's acceptable speeds. Just as some may be happy at 2kn others will regard 20kn as a minimum. However, it would be rare to find people prepared to motor at 2kn continuously (emphasis on continuously)

Of course there are sail only vessels. If we are only discussing speed then it should be recognised that they will likely be travelling faster than a solar powered vessel anyway. Certainly so during overcast or dark conditions (again remember my 'continuous' condition).

My post was not anti-electric. A solar powered vessel makes a lot of sense for those looking to motor short and/or slow steps perhaps with daily recharge capabilities. For those looking to go faster or further, I don't think we are there yet. The numbers simply dont stack up for solar only power supply and adding a generator adds efficiency loss, weight and complexity. I don't think we are too far off having a generator running at constant load with electric drive being more efficient than a direct drive diesel running at variable loads. A Prius if the sea if you will

Cheers

[Adelie]

Originally Posted by Narfi

Fair enough
A simpler question perhaps so I can do the exercise myself.
Fully loaded for cruising, how much power do you need to push your boat 5kts? How much power to push your boat 8kts?

What boat? LWL and lightship displacement?

The Uma folks make 3.0-3.2kt using 1.2kW.
Pearson 36, 13,500lb, 29.16’lwl

A good approximation of HP requirements can be obtained from knowing speed for RPM of the motor you have and the HP curves for you motor.
What motor do you have?

[valhalla360]

Originally Posted by danstanford

2017 J/88 from J Boats with an Oceanvolt system from the factory.

Any chance you could share some specs on the boat along with range at various speeds?

[valhalla360]

Originally Posted by Simon.Sails

I still don't understand why a feasible system needs to be able to do that. Batteries work just fine today. You simply need more than sufficient energy generation, either through a hydrogenerator while sailing or solar. I just don't see the need to be able to motor non-stop, without any regeneration for hundreds of sea miles for most people. It's a sail boat, it's got unlimited range. A bit of sun or wind will recharge even a modest electric motor setup.
A generator for emergencies should be enough for emergencies, no?

Fact is probably 99% of new boats aren't and never will do an open ocean crossing so hydrogenation is very much a niche product.

Even on a big cat, enough solar to do anything meaningful in terms or propulsion isn't reasonable...plus it kills the sailing performance to squeeze 2-3kw of solar panels.

[valhalla360]

Originally Posted by Adelie

With 1500W solar and an appropriately sized battery bank you could motor indefinitely in sunny calm low latitudes at 2.5kt. That’s 60nm/d free and quiet.

Somethings not adding up. 1500w might get a small cat in calm conditions doing 2.5kt but 1500w of solar panels isn't going to put out 1500w for 24hr. Plus there are house loads to consider.

If you get 5nm/d out of it you would be doing well on a small cat. A big cat, overcast, waves or even a modest head wind ...and that likely dwindles to nothing.

[Adelie]

Originally Posted by GoneDiving

I used reasonable to mean satisfactory rather than a moral judgement. There will always be outliers in people's acceptable speeds. Just as some may be happy at 2kn others will regard 20kn as a minimum. However, it would be rare to find people prepared to motor at 2kn continuously (emphasis on continuously)



Of course there are sail only vessels. If we are only discussing speed then it should be recognised that they will likely be travelling faster than a solar powered vessel anyway. Certainly so during overcast or dark conditions (again remember my 'continuous' condition).



My post was not anti-electric. A solar powered vessel makes a lot of sense for those looking to motor short and/or slow steps perhaps with daily recharge capabilities. For those looking to go faster or further, I don't think we are there yet. The numbers simply dont stack up for solar only power supply and adding a generator adds efficiency loss, weight and complexity. I don't think we are too far off having a generator running at constant load with electric drive being more efficient than a direct drive diesel running at variable loads. A Prius if the sea if you will



Cheers

There are plenty of folks here who disparage those who’s expectations are different than their own. Some of those folks are very open about it, others do it more subtly using word choice.

Currently the is a builder in Malaysia that is producing a 40’ power cat that can run continuously at 4kt on solar providing solar conditions are good during the day and sea state is low.

Starting with a full battery I believe it can go 6kt for 24h, or 36hr if you get underway about dawn.

For cruising applications, any use where you regularly expect to use ICE in a hybrid application it will need to be direct drive (parallel hybrid) the efficiency penalty is too high for series hybrid (all ice power converted to electricity which drives a motor or recharges a battery bank.

The EU put a lot of money into researching this for their commercial fishing and coastwise transport industries. They set out to show how series hybrid would work and were unhappy to determine that generally parallel hybrid is much better. Project was called HyMar.

Where generator use is only very occasional then series is the better choice. Somewhere close to that is the point where parallel becomes the better choice.

[valhalla360]

Originally Posted by Narfi

Here is a theoretical question for you,

Using your boat, you take the mast off and spend a year doing the great loop. You travel 50 mile legs, stop and 'tourist' for 2 days, then go another 50.

So battery+ solar needs to get you at least 50 miles, and you should be able to fill an empty battery bank in 2 days at anchor.

How would you size an electric/solar system to cover that in perfect conditions and what size generator would you use for anything less than perfect?

Solar array size?
Brand and size/model of electric motors,
Battery bank size,
anything else?

Can you do it?
If not could you do it with a larger roof?

Having done the Great Loop on a 34ft cat, a 50mile run is going to need around 10kw to maintain 6miles/hour for just over 8hr...so 80kwh of battery bank...round up to 100kwh as you don't want to run them down to 0% charge. Probably around 1400lb of batteries on an 8,000lb boat.

To recharge 80kwh with solar, you would need around 20kw of solar panels (they don't put out power 24/7). Pretty hard to find the space for that on a 34ft cat.

If you reduce the speed, you can reduce the daily draw and battery bank size but now you start to run into some practical issues. On the river system, it's strongly discouraged to run at night because there's a lot of floating debris (including hole trees). If you are going to limit your speed to say 4mph, that's a 13-14hr day...in the fall when days are getting short, you may not have that many hours of daylight.

Also, what happens when you turn up the Ohio River and are fighting a 2mph current for 60miles doing only 4mph? Now you are looking at probably 3-4 days to make it to Kentucky Lake.

This isn't to say you can't do it but solar wouldn't be the primary source of power. Stopping at marinas and plugging in and adding a generator to supplement power generation on the longer stretches really is needed from a practical point of view.