Playhouse lights panel

SystemSystem Posts: 2,511 admin
Hello, I'm really new to this and not very bright. All I want is to set up a small solar panel on my daughter's playhouse. I'm hoping to run the occasional flourescent light and maybe a radio or small appliance, not very often and not for more than a couple hours at a time. It's off grid, so anything I get will be a bonus.

From what I'm reading, a small 40 watt panel should do me, shouldn't it? Should I get one battery (I'm told a cheapie would work just fine) or hook up a pair?

Other than a regulator and converter (400W?), what else should I need?

I'm wanting to mount it on the roof of the playhouse -- it faces south, and I live in Cleveland.



  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Playhouse lights panel

    Welcome to the forum.

    What you really need to do is define exactly what you want to run and for how long. Otherwise you're just guessing, and the trouble with guessing is that you can be wrong 99% of the time.

    So the first question would be is this going to be DC only, or are you planning on powering an inverter for 120 VAC?

    The second question would be how many Watts at once would you need to supply? Related to that is how many Watt hours? For example, two 13 Watt CFL's would be 26 Watts total. If you leave them on for two hours that's 52 Watt hours.

    Once the amount of power needed is determined then you can pick a battery that can supply that and figure out what you'll need in solar panel and controller to recharge the battery.

    I'm going to guess that beyond providing some fun lights for kids, Dad wants to learn a bit more about solar electric systems. :D
  • System2System2 Posts: 6,290 admin
    Re: Playhouse lights panel

    Yes, I would like to learn more about these, and if this is a success, I can start prodding the wife into doing something with the main house -- way down the road.

    I cannot imagine them out there for more than 2 hours. I looked at the info on the back of their CD player, it says 14 watts, I have no idea if that is the real number I need or not. So let's say on the most usage days, I'll need 100 watt hours (Based on how much they actually use the playhouse, the lights won't be used much at all.)

    So I should pick up a battery that can handle that?

    Dumb Q: if a panel says "100 watts," does that mean it will/should pull in roughly 100 watts in a day? (at optimum conditions, I assume.)

    Thanks for the speedy reply.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Playhouse lights panel

    Panel ratings are the peak Watts they'll provide "at any one time" under ideal conditions. Since conditions are rarely ideal in the real world a certain amount of derating has to be factored in. The "typical" derating factor is 77%, but a large number of things can affect the actual output.
    So the "100 Watt" panel is likely to produce 77 Watts. If it gets 4 hours (again a "typical" number) of "equivalent good sun" it will produce 308 Watt hours per day. I can't stress enough the huge number of things that will affect panel power: temperature, humidity, angle of sun, pollution, elevation, et cetera. And that's before you start to lose that power to the wiring and components.
    For a "real house" application you should look in to any incentives offered in your area for a grid-tie installation. Solar power is very expensive. For off-grid applications the cost is roughly $1 per kW hour over the life of the equipment. For grid-tie applications (no batteries) it's about half that. As you can see it doesn't compare favourably with utility power rates.

    Now back to our regularly scheduled design plan. :D

    For 100 Watt hours per day on a 12 Volt system you need at least: 100 / 12 = 8.3 Amp hours. So you need at least twice that, 16.6 Amp hours, for 50% DOD. Again, that's without compensation for the losses inevitable in a system. Since that is a very, very small battery you might want to base your design around what size battery you can get/afford and let the power drop off where it may.
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Playhouse lights panel
    Dumb Q: if a panel says "100 watts," does that mean it will/should pull in roughly 100 watts in a day? (at optimum conditions, I assume.)
    No practically speaking a 100 watt panel charging a battery through a charge controller will only supply a little more than 50 watts per peak hour of output. If you are in a sunny climate you will get this output for 4 or 5 hours a day on average. So a 100 watt panel will put about 250 watt/hours into your battery bank in a day. Battery capacity is another topic you will need to understand.
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