Tuesday, August 2, 2016

Re: [Electric Boats] AC vs DC motors - new EC cat

 


Hannu,

Great information. Thank you.

I'm still trying to get my head around the power requirements though.

There isn't a lot of information on the net regarding solar /. electric powered boats of larger size.

So far, the only two I've managed to dig up any info on are SUN21 and Turanor.

Here are the specs I have on SUN21

Solar panel area 65 m2   
520 Ah 48V DC Lead accumulators in each hull   
Solar Modules 10kw 2 x 5kw Solar Modules  
Electric motors 2 motors 8kw each  
Max speed 7 knots
Average speed 5 knots  (24/7) 
Draft 1.000 m Maximum with full load  
Total Beam 6.600 m   
LWL 14.000 m (46')
Displacement 12000 kg  (26,400lb)

And Turanor

Solar panel area 512 m2  
Solar efficiency 22.6 %  
Solar Output About 100 kW
Lithuim Ion Batteries 8500 kg  
    
Electric motors 90 Kw each at full load.  
Propellors 2   
Blades per propellor 5 tapered surface piercing props  
Propellor diameter 810mm  
Propellor Max RPM 600rpm  
Max speed 14 knots  
Average speed 5 knots  
    
Height above water 6.300m  
Draft 1.500m  
Total Beam 23.000m With panels extended 
LOA 35.000 m With panels extended 
LWL 31.000m  
Beam 16.000m  
Displacement 90 - 100 Tons  
    
Average electrical consumption 20Kw 17kw for the motors and 3kw for the crew.

So, it looks like Turanor uses about 8.5kW per motor to cruise at 5 knots.

But....It's got ultra efficient wave piercing hulls with minimal friction.

And it needs the whole 180kW to push it through the water at 14knots. And that's with a hull speed of about 10knots.

So, Hannu, it looks like you're right on the money with your estimate of 10-15kw per side to push an 80'cat at 8kn or so.
But if I want to put the hammer down to escape a storm or some other emergency, I'm still going to need a lot of power to get the boat up to anywhere near 15kn max speed.
If Turanor needs 90kW a side, I don't see how I would be able to do it with less?

Does anyone have an opinion on reliability / quality of motors like these?

On the second link, the dual motor provides 189ft lb of torque at 5000rpm.

That would roughly convert to 1000 ft lb of tourque at about 800rpm man that's a lot of tourqe....and a lot of Amps.

Sorry for all the basic questions, I'm just trying to get a broad idea of what I'll need to achieve the goal.

Once again, thank you for all the input everyone.

Regards

Dave



On Sat, Jul 30, 2016 at 4:00 PM, Hannu Venermo gcode.fi@gmail.com [electricboats] <electricboats@yahoogroups.com> wrote:
 


You only need about 10-15 kw per side of power for 8 knots from a 80
feet hull.
This 50% variance can change another 50% based on windage, mass, or hull
shape.

Current best solar panels are about 21% efficient => 330 W / panel, or
210 W / sq meter of hull area.
You might get, at best (imho), 12 kW of direct PV input.
Forget 70 kW, totally unrealistic.

12 kW / 0.21 (W/sq m) => 57 sq m.
Panel array between the hulls.

You need a light, strong, frame for the panels.
Spaceframe from commercial stuff would be best - something alu or carbon
fiber.
You need to start with
1. how to arrange the panels, and where.
2. size of same
3. Then power control electronics for 12 kW, with potentially 50 kw (?)
power runs.

Note spaceframe is lightest suitable structure, and even then it likely
to be 1-5 metric tons in mass.
500% variance based on how the open space is constructed, and what the
span is.
Rigidity is cube of span.

Note wracking stresses (huge, enormous) in widely spaced structure,
where the hulls want to twist and bend about 30-40 cm, wrt each other,
continuously.
Thus, mounting of frame and panels is a critical item.
Soft mount (ie non- structural) is an option, with it´s own issues.

Parts 1., 2., 3. are all critical.
Hulls are trivial.
Motors etc are trivial. Cots, easy and cheap.

There are no cheap large cats in the recreation market.
Use current cats for inspiration, and look at howto/where mount panels
on them.
Use current costs for estimation.

If you build in alu, estimated cost about 1-1.5M U$D, and 20.000+ work
hours.
Thats for a bareboat, no electronics and entertainment.

Note difficulty of making hull, almost no professional work being done
in this size, ie it´s very expensive due to practically no competition.
The pro yards don´t and wont want to do a cheap-ass build (liability,
lack of profits).

It is not, technically, hard to do alu hulls.
It´s just that there is almost no-one doing them to this size, and they
charge $$$.

A semi-pro approach would/could be to have 2 alu hulls made by those
doing large alu sailboats.
Again, the next step up is a major undertaking.

Examples:
Alu will need, for example, insulation, as its a huge heatsink.
Cost of insulation, perhaps 30-50k.
(About 20-25k per hull.).

Major power wiring.
Cost of same, perhaps 30k.
(15 k per hull, with suitable mandatory marine isolators etc.)

My point.
Running 50-100 kW power wiring, long distances in complex structures, is
a major cost.

Project management is a major cost.
Who will do this ?

I could think of 5 ways to drop 100-200 k each out of total build costs ..
but all will need significant specialist skills from someone.

CNC cutting the major elements in a cheap location (could be asia, or
anywhere, with a huge router) is one way.
Shipping the pieces is only 10k vs easily 100k+ extra cost delta to
getting them cut in the USA, for example.
Who will check them ? and how ? and authorise payment.

Example:
Who will build the 3D model, and with what sw ?
Note correct sw can easily cost 100-200k in extra work, vs "better" sw.
Ie cheap Rhino 3D can easily make pretty models, but wont drive
manufacturing processes, today, as-is.

Thus revisions in Rhino are not a manufacturing solution.
IE you cannot derive manufacturing prints from a single model- and thus
every hull revision costs 1000+ work hours extra in other stuff.

Cost of panels.
Sunpower panels are more efficient (21% vs 16%) but twice the cost at
say 1.2$/W shipped vs 0.6$ for containerload.
Thus Sunpower panels might be 14 k$ for 12 kW, vs 6 k for china panels.
Add 100% for bos, and a 12 kW system might be 24 k $.
Relatively low cost, in context.

The range is huge in terms of $$, mostly due to how the marine industry
works, in terms of business.
Thus, getting 2 hulls built and a cat based from them, is relatively
easy in engineering terms, and could potentially be not-expensive.
But based on economics, it will cost 3-5x more than it "should".

So technically, if I needed no certifications, I could probably get a
cat done for 200k in alu.
But, practically, a cat with "marine" stuff would cost around 800-1M$.
(These costs with no engineering or systems).

The same could be done, in a marine yard, for under 200 k in steel.
Steel is about the same in terms of mass (yachts over 15 m), but 1/3 -
1/4 the cost.

--

-hanermo (cnc designs)


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Posted by: David Adams <lonzim.adams@gmail.com>
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