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Old 25-04-2014, 04:29   #31
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Re: Are my Maths Correct?

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Originally Posted by poiu View Post
It is perfectly possible and is actually on my job list, item 102. In the Caribbean I haven't found it absolutely necessary, even in Summer. Greece in August can get horrid hot and I know where you are coming from. You can minimise start up current problems with a soft starter on the air con compressor - I bought one, but not fitted it yet. You can improve efficiency by running a DC water pump, ideally one per compressor or an AC pump on an inverter. The pumps are power pigs and need to be in your calcs.

To do this routinely, say every night at anchor for only an hour you only need 80A on your figures, which seem ok to work with. That's not so much. About 1.5m2 of good solar panels could do it. 1.5m2 x 18% efficiency x 1000W/m2. /12v x 4.5 hr charge per day =101A output. If you want to do this more than an hour then get a genset.
Your figures are in keeping with my thoughts. Fans have just been fitted and we are looking at a solar panel fit next week.

We only aim to run the AC on a minimal basis. As you correctly point out Greece in mid-summer can be overwhelming and if you can close the boat up and just knock the sting out of the cabin temp it makes a night of sleep possible.

I had hoped to fit the new style of solar panels that heat water as well as generate electricity. Apperently keeping the panels cool makes them more efficient and this new design does just that. I spoke to one manufacturer suggesting that he makes a marine unit but he thought the market too small even though there are tens of thousands of boats worldwide sitting in the sun that would prefer not to run an engine just to top up batteries and heat the water.

Going off topic and back to the Prius. The latest PIP version will do up 14 miles and 59mph before resorting to hybrid mode. I regularly do a 13 mile trip door to door in electric only. I can't get back without using the petrol hybrid side of things because charging points are too few and far between in public car parks. It is a totally different machine to my first Prius and great to see how this technlogy is coming along in leaps and bounds but will it ever trickle down to boats?

Alas, unless you are in the super yacht bracket getting any setup remotely out of the accepted rut is almost imposible.
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Old 25-04-2014, 10:38   #32
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Re: Are my Maths Correct?

A sailing boat is pretty green already. I can manage fine on 4 or 5 litres of diesel a day and that includes transport of me in my floating wind powered house with all the lighting and tv power I need. Try running a house and a car for the equivalent of that. Is surely possible to do better still with a lot of effort.
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Old 25-04-2014, 10:49   #33
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Re: Are my Maths Correct?

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Originally Posted by Alenka View Post
Going off topic and back to the Prius. The latest PIP version will do up 14 miles and 59mph before resorting to hybrid mode. I regularly do a 13 mile trip door to door in electric only. I can't get back without using the petrol hybrid side of things because charging points are too few and far between in public car parks. It is a totally different machine to my first Prius and great to see how this technlogy is coming along in leaps and bounds but will it ever trickle down to boats?



Alas, unless you are in the super yacht bracket getting any setup remotely out of the accepted rut is almost imposible.

I doubt the Hybrid boat is as viable as an automobile and the reason is a boat is usually operated in a steady state. A few reasons the hybrid concept works so well in cars is they are usually accelerating and decelerating frequently, Small engine offset for acceleration with battery assist, but regenerative braking gives some of the energy back on decelertion.
I feel certain that more efficient engines may one day find themselves in boats (Prius does not have an Otto cycle engine for example, it's an Atkinson cycle engine)
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