Posted: 11/19/2008 1:48:04 PM EDT
| I'm trying to get a accurate picture in my mind of how much solar cell is needed to charge a battery to power X amount of stuff at night. For example, how much solar cell capacity would be needed to charge a battery to have enough power to run something that uses 100 watts of 120 volt AC for 10 hours every night ? What if I wanted 300 watts of 120 volt AC for 4 hours ? Is there a formula or calculator to figure this out ? |
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Quoted:
I'm trying to get a accurate picture in my mind of how much solar cell is needed to charge a battery to power X amount of stuff at night. For example, how much solar cell capacity would be needed to charge a battery to have enough power to run something that uses 100 watts of 120 volt AC for 10 hours every night ? What if I wanted 300 watts of 120 volt AC for 4 hours ? Is there a formula or calculator to figure this out ? Well, 100 watts for 10 hours is 1000 watt hours or 1KWh. If you charge for 10 hours (amount of sunlight) and there are no losses (there will be, figure at least a 20% loss just to be safe), you'll need a 100 W panel. But if you're charging a battery there will be losses, you better just go with a 200 W, same thing for the 300 W load for 4 hours. Disclaimer, I don't know much about solar panels, I just did those simple figures in my head to get you close. |
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Check here, they might have a way to calculate it.
Home Power Mag. |
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Quoted: As previously mentioned, 100 watts x 10 hours = 1000 watt-hours.how much solar cell capacity would be needed to charge a battery to have enough power to run something that uses 100 watts of 120 volt AC for 10 hours every night ? In most parts of the U.S., you're lucky to get 6 hours of useful sunlight in a day's time. So, 1000 watt-hours/6 hours = 166 watts, which is the absolute minimum solar panel size required to do the job in one day's time (or 83 watts in 2 day's time, or 55 watts over 3 day's time, etc.) What if I wanted 300 watts of 120 volt AC for 4 hours ? Is there a formula or calculator to figure this out ? 300 watts x 4 hours = 1200 watt-hours.So, 1200 watt-hours/6 hours = 200 watts, which is the absolute minimum solar panel size required to do the job in one day's time. |
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Compared to their 120VAC counterparts, 12VDC appliances have several disadvantages:
1. They're more expensive, 2. They aren't available in nearly as wide a variety of models, features, etc., 3. They require much thicker power wires. In the case of high-power appliances, this makes them impractical (ever seen a 12VDC microwave oven or air conditioner?  )
Even though the use of an inverter adds some expense and inefficiency, it's usually more than made up by the other advantages of using 120VAC appliances. |
| That may be true, but at least he's not giving up 10-15% of his watts in to loss in an AC inverter. You're saving on one end and paying on the other in the form of a larger, more expensive panel to do the same things. This will matter more when your storage batteries get old and weak.. |