Question!? need a large flat horizontal surface area for solar panels

Discussion in 'Boat Design' started by Val567, Aug 26, 2012.

  1. ub3r l33t dud3
    Joined: Sep 2012
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    Location: capac michigan

    ub3r l33t dud3 Junior Member

    the plus side to hydrogen over batteries would probably be the weight difference. with the only notable weight being from the storage tanks themselves it would keep weight down and be easy to refill.
    and yes you could use the extra volume of space to store the hydrogen at a lower/safer psi. as far as the fuel cell, if you dont have a need for high amperage then a smaller cell wouldn't take up much space at all. :)

    i would have to ask my mom for some numbers on the energy storage part, she designs and operates hydrogen fueling stations for cars.
     
  2. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    Hey slim again..about the voltage.I'm not an electrical engineer,but when the diesel electric fad came around a few years ago promising better fuel economy and such I boned up on the basics.
    As I thought,it was BS.

    Watts= amps x volts. He says he has 30kw of storage =30,000 watts.

    Batteries should not be discharged much under half,they don't last.
    Batteries also should not be discharged with too many amps-they don't last and they lose a lot of efficiency.

    The reason I asked for volts,is to see actually how much he has in storage.
    So between 24 volts and 48 volts,I can tell if he's counting the entire battery to empty,or to half. I can also tell how many amps he's using and basically what rate of discharge.
    And if he actually has 30kw or if it's only really 15 kw thats useable.

    For a coastal boat with few miles it'd work in the right areas,but on a cloudy day and a storm coming up fighting wind and waves and currents and the batteries are dead....you are done for.

    Like I said a good used sailing cat can be bought for a fraction.
     
  3. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    I just wanted to permanently fix your statistics for the moment. Do you have a lottery in Sweden?

     
  4. erik818
    Joined: Feb 2007
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    erik818 Senior Member

    Yes we have lotteries. There might be a way to use the digits 2 and 7 to represent the cost for joining. 0 is what I win when I gamble.

    Erik
     
  5. bpw
    Joined: May 2012
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    Location: Cruising

    bpw Senior Member

    Jonathan,

    How does one use regenerative braking on a boat?

    And also curious how you plan to build a luxury cat for $250,000 that can sell for $500,000? There is a high end sailing cat builder a little bit away from where I am living right now and there boats go for an even million in base model trim. And they are built in Chile with reasonable labor costs from production molds. I highly doubt there profit margin is anywhere near 50%.

    And $2 billion projected 10 year profit? Has any boat builder ever made this kind of money?
     
  6. kerosene
    Joined: Jul 2006
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    Location: finland

    kerosene Senior Member

    That train of thought is near impossible to follow as wrong units are being used but if I read it right you have major misunderstandings.

    First kw is NEVER a unit of storage. It is a unit of power just like horsepower. Very small storage capacity can create 30kw of power for a very short time. This is not nitpicking it is a major issue in these discussions that wrong units get used. So I am assuming the storage capacity in example is 30kWh (big but reasonably sized battery pack, will drive a decent sized car at 60mph for an hour = 30kW * 1h = 30kWh).

    secondly, Formula P=U*I, power equals voltage (or potential) times current or units wise as you expressed W=V*A is correct. But you used the Watts as if they were unit of storage. Going from 48v to 24V in no way indicates half storage capacity used or anything like that. You can create a battery pack of almost any voltage that can have either huge or tiny storage capacity. You can have 24V or 48V pack which both have equal storage capacity as kWh.

    24V * 100Ah = 48V * 50Ah. So you could have 2 different kinds of 2.4kWh packs one of which is 24V 100Ah battery and the other one is 48V but only 50Ah.
    Both can do same amount of work assuming they operate equally efficient systems.

    Relevant to this and the voltage drop is that a typical battery stays at relatively flat voltage through most of its capacity. So a full battery cell might be 4.4V, 50% discharged 4.2V and 95% discharged might be 3.8V.
    I pulled the numbers out of air but real batteries act sort of like that - especially the modern ones have very flat voltage curve.
     
  7. WestVanHan
    Joined: Aug 2009
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    Location: Vancouver

    WestVanHan Not a Senior Member

    Thanks kerosene-I know it's kwh-my abbreviations,my bad.

    Yes-total amount of work/energy (kwh) is the same whether it 12/24/or 48 volt but it's the rate of discharge in a/h.

    Typically the useable total a/hr between 20 hour discharge and say 2 hour discharge is less than half IIRC.
    So in using it up quickly- half your energy is lost.
    And that's not even counting the drag in speeding up-he may go only 20% the distance at full power as opposed to slow-who knows?

    So if we know the volts,we can quickly do a series/parallel battery pack and get his useable a/h for 3 hours or whatever hours by looking at the battery specs.

    If he's running 24 volts or 96-it makes a difference in his a/h discharge rates,and therefore his useable kw and range..

    Anyways,that's how it was all explained me years ago by someone involved in electric vehicles-if he told me wrong then I'm wrong.
    I'm a market trader,not an electrician.

    But at the end of the day,there's 500 used cats for sale for cheaper...
     

  8. erik818
    Joined: Feb 2007
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    erik818 Senior Member

    The voltage you work with doesn't make much of a different when it comes to discharge rate. If you have eight 12 V batteries you can couple them in parallel or series to get 12 V or 96 V. A 12 V system will have to provide eight times the current of a 96 V system for the same power, but each 12 V battery still needs to provide the same number of amps in both systems (for the same output power).

    The system voltage doesn't really matter for the motor either. A 12 V motor will have few windings with thick wires and a 96 V motor will have eight times as many windings, but thinner wires. With the same fill factor in the motor you get the same efficiency.

    The reason to go for higher voltage is that you can reduce losses in the power electronics and in the wires between batteries and motors. For a 19.2 kW power stage it's much easier to design power electronics for 200 amps and 96 V than for 1600 amps and 12 V. Modern power electronics are getting better and better to handle high voltages, so something like 600 V would be a nice voltage to work with for high power electronics. It's just to connect fifty 12 V batteries in series.....

    Erik
     
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