On 2/26/2012 9:47 AM, seansullivanjobs wrote:
Sean
so 120kw? single or 3 phase 415v or 220v? That's a of a lot of power.
Yanmar 3YM30 's consume 1.7 litres per hour at rated continuous power (27+ hp), according to Yanmar's data sheets
The mass of that system for a 2250 mi trip SF to Hawaii would be motors & boxes 360lb+ fuel 3000lb = 3360lb + pros and shafts.
Diesel electrics require about 60kw input, to be able to power two 20.1kw obs i.e. equiv to the 3YM30s. This is due to losses in the electric motor and 2nd to a safety margin to allow output to be continuous. Handy if you can switch voltages say 220 to 415 because at lower speed you can use the lower voltage and full throttle (part throttle brushless controllers are inefficient)
Then there is the weight of the motors/leg. Two options present themselves a single leg with contra-rotating props with 60kw Prius motor or the early Prius 30kw C1 motor. Prius equipment can be be easily marinised and the wrecked Prius brings motor, battery, controller, a cvt transmission (perfect for electric propulsion) electronic controls and a host of self locking security and other devices with it which are easily serviced by Toyota dealers.
2nd don't write off batteries in electric systems they give you a good cushion for peak loadings which tend to be short term, e.g. bars or tidal or local current, or low power silent running like sail assist or docking or allowing people to get off to sleep and most importantly picking up unused power current when running the gensets at an efficient but under utilised rate, plus at 220v they can do backup on other electrics.
Testing of 10 yo Prius NiMh suggests they wear very very little over that period. Also the sub-assemblies for the pack can be bought allowing a defective part of it to be replaced. And the mass isn't enormous.
With genset at 2500 lbs + fuel 3000lbs+leg and motor etc 470lbs (Yamaha vmax 150 stock) all up that is close to 6000 lbs.
Yanmar D27/D36 outboards are simple have a huge rap on reliability, spare parts through Yanmar dealers and run on bio, kerosene and diesel fuels. They don't whine like gas obs and with a little better soundproofing in the cowl could be just the tick. A pair of 27's pushed a 35' cat from sf to Hawaii on 385 gals. Other users report fuel use at 1.5 gals per hour at full throttle. This suggests the 35 footer was moving at more than 15 knots. Another user motored 3000 miles on a single D27 when his 180hp main failed.
All up weight pair of outboards 360lb plus fuel 3000lbs = 2260 for trip SF to Hawaii trip (2250 mi)
At around a 40kw output level the diesel outboards are lightest and simplest - as they are made to order prices are available from Yanmar. However there are also new in box supplies available on the web. start at $8k per side
The diesel electric is heaviest of all options unless you have redundant gen capacity already on board (3 tns seems to equate to very high high power). However but its also self build and a single OB leg would be a very easy fit and stock say Yamaha parts easy to get.
Along with what others have said here I have data logged a lot of model boats from scale 3 knot models to 80 mph racers and electrics go faster for about half the power use claim by ICE makers. So that ratio seems pretty consistent.
I cannot be sure but the most likely reason seems to be the fit of each system to the load to be dealt with.
ICE's make power by the rpm rather than the load on them. The output rarely matches the load and equalklky often does not with the engines most efficient operating range.
Electric output is load dependent. Also with cvt you can ensure a much better fit between the load, output and the high efficiency operation of the motor. I have a feeling a Prius/(Merc/GMC/Yam) leg combo would provide a reliable unique and more economical solution that it first appears to be.
I can email a more detailed appraisal of the 3 system with web references
regards Andrew
Andrew:
The onboard HVAC needs to be 3-4 tons. I estimated 4 tons, but have had others suggest a smaller, 3 ton system.
James: The Aquawatt is propped and geared for planing boats. This is a displacement craft, so it's of no use. You need a good, low gear ratio and large diameter prop to use an outboard on a displacement boat. Also, I hate to make waves on both points, but I was looking into a diesel/electric system. There is still an ICE to maintain (or two) that generate all the power to drive the boat. No escaping the maintenance. More maintenance than straight ICE, in fact since it's ICE + all the electric components.
Jerry: Not a bad idea. I've talked to the guy at Beta about putting a big AC generator on one of the Betas and he was open to it. Pricing was a little high, but he was very flexible and wanted to work with me. I wonder if they have a larger unit? One priority is to have the props leave the water when sailing (no junk below the waterline), so the Beta would involve a lot of extra engineering. I'm not sure about that, but I would prefer to run on diesel if possible. Just have better luck with all my diesels than all my outboards.. :)
-- AJ Gilchrist Fastelectrics 0419 429 201
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