Power requirements for solar-electric sheepwagon?

  1. Hi,
    First off, let me say that I failed physics in high school and got myself a C- in basic calc. so I don't understand much of the math language (although I can understand its meaning). Further, I'm not an electrical engineer; however the practical applications of math, engineering, and physics is what makes me happy!

    So, here's my idea:
    I want to build a solar powered sheepwagon/tiny house on wheels!

    So here's the details:
    The wagon will weigh about 6,000 lbs. (including batteries)
    Operational speed should be about 3-5 mph.
    I'd like it to run completely on solar. I'm thinking to use amorphous silicon solar cells, as they are flexible and seem to be more efficient than wafer silicon cells.
    On board electrical consumption requirements (e.g. radio, water pumps, lights, laptop, cell phone) should operate on a 12 volt system through a different electrical system than the main propulsion. So don't figure these...

    I would like to know only what power is required to get this sheepwagon moving, what energy is required to keep it moving, if I would be able to climb any hills, and how long a sustained trip could last given an 12 hour period of full sun.

    I know it's a longshot, but I don't know the math or the physics. Any help would be appreciated!

  2. jcsd
  3. Baluncore

    Baluncore 3,203
    Science Advisor

    What you can do is determined by the energy available. Energy is measured in joules. Energy is the physics equivalent of money in our economy.

    The rate you can do things is determined by the “power” of your equipment. Power is measured in watts. Equipment with a power of one watt can convert or process a maximum of one joule of energy per second.

    You can gather more energy per hour of sunlight by investing in more solar panels.
    You can climb hills quicker by having more powerful motors, or lighter batteries.
    You buy batteries and store energy in them over a period of time. The amount of energy storage in batteries you need is determined by the highest jump you need to be able to do in the dark.
    The power rating in watts of your traction motors decides the maximum rate you can climb hills.

    Without batteries you can run only when sunlight is available, and your speed will then be determined by the energy your panels can generate from the available light.

    The cost of the panels, batteries and motors must be invested up front. Now you should play with the numbers to work out how best to invest your money in those three pieces of equipment based on the performance you feel you can justify.
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