Hi there,
I rarely run at full throttle and the Torqeedo will soon show an over temperature warning at full throttle and automatically reduces power down to about 4kw. But even at that your estimate of range is about right for full speed operation.
But my usual power setting is around 1000 watts, which gives me say 3 to 4 knots. And at three knots for 8 hours, I'd have 24 miles range (thats 80% discharge). Most of the time I only use it for say 10 to 20 minutes before getting the sails up and no longer need the motor.
When the wind is contrary and the channel narrow, requiring lots of short tacks, it is useful to have the motor running at a low throttle setting, even just a few hundred watts, to help her to tack easily and to maintain way when the wind knocks. I find this to be a nice compromise - it doesn't use much power but makes the sailing much easier, and gets me to the destination much quicker than sail power alone.
Oh man, I envy your budget! 100 kwh would suit me just nicely. But alas, I couldn't afford the weight penalty of such a pack. (1200kg).
In my limited experience I find that getting out into the ocean means that I use little or no power for the motor. My recent trip from Brisbane to Sydney took a couple of days and the motor was only used while still landlocked. The motor was needed for getting out of the Caboolture river, and then navigating some channels in Moreton Bay and then crossing the bar at Gold Coast Seaway. I think that used maybe 6 or 7 kwh. And getting into port at Broken Bay required running the motor only for a few minutes to pick up a mooring.
The advantage that I have is that my boat is an ex racer and sails really well, and so doesn't taunt me to run the motor even in light conditions. My last couple of small adventures from Broken Bay to Sydney Harbour were sailed all the way in light winds (5 to 10 knots) and the handful of other sailboats at sea at that time were all motoring or motor-sailing. From what I've seen those Bavaria's sail really nicely and I'd expect the lure of motoring would also be limited.
It could be that the success of your conversion may hang on the mindset of your client and the kind of sailing he/she does. Is he inclined to want to motor at the least opportunity? Or does he love to sail, and will not even be wishing to run the motor except when nosing up to the dock? Will it be only used at weekends, or sailed around the world?
Another source of power you'll want to consider is the power of the boat through the water when sailing. Regen from the motor when under sail has been discussed here quite a lot and there's not a clear consensus on it. For some it has proved successful and others have rarely seen it. A search of the archives will turn up some interesting reading. A towing generator or a wind generator that converts to water turbine is another option as a power source especially if ocean passages under sail are likely.
It will be a challenge finding a way to fit the panels and wind generators on board. Could it be that you could approach it from the opposite direction? That is, figure out what solar and wind power you can reasonably fit on the boat, and from that estimate speed and range capability and whether that would that satisfy your client.
I hope you have fun with your designing...
Cheers
Chris
On 06/05/2010, at 4:38 PM, r1ck_r0ck_4_ever wrote:
Thanks everyone for your expertise. I still have a lot of research to do.
Chris, How long does your 10kwh lithium propulsion pack last? The graph of your energy consumption shows that you need 5kw to go 5kt, so you can only go about 8miles max motoring?
I was looking at putting in 100kwh of lithium for the main drive pack into the bavaria, but I feel this is still useless unless I can top it off with solar and wind if the owner decides to take it out for a long cruise out in the ocean for a few days.
My thinking is the only way for the boat to match the same 210L of diesel's capability is to have a lot of solar and wind energy generation. I estimated about 3000W of solar panels and 2000W of wind will be needed, but it'll be very difficult to install everything in a nice package.
Only if he could trade his boat for a 50' Catamaran... Then I'll have plenty of room for solar panels.
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