Solar Technology Math

SOLAR panels are made up of silicon cells. When sunlight strikes the silicon, a flow of electricity results within each cell. The electricity, measured in amperes (or amps), can theoretically be used to run appliances directly. But it is more efficient to collect it in deep-cycle storage batteries. You can estimate the number of solar panels needed for your recreational use by determining the average power consumption per hour (in amperes) for the appliances you wish to run. You will also need to estimate approximately how long you expect to run each appliance.

Here are some ratings of popular 12-volt appliances:

Appliance Amps Used Per Hour

15-to-20 watt flourescent light 1.0 12-inch black-and-white TV 1.5 9-inch color TV 4.0 tape recorder .5 refrigerator 5.0 8-inch fan 2.0 blender 8.0

Use this list to solve the following problem:

Question: You plan to camp out using panels that generate 3 amps per hour. In your locale, these panels will receive four hours of direct sunlight per day. If you run the tape recorder two hours a day, the light six hours, the black-and-white TV two hours, and the blender 15 minutes, how many panels do you need?

Solution: You can set up your problem in this way:

Item Load Consumption x Hours Used = Amps

Amps/Hour Per Day Per Day

tape recorder .5 x 2.0 = 1.0 15-watt light 1.0 x 6.0 = 6.0 TV (B&W) 1.5 x 2.0 = 3.0 blender 8.0 x 0.25 = 2.0

Total = 12.0 Amps

When you know the total amps you will use per day - in this case 12 - divide that figure by the number of amps generated by one panel in your location. For this problem, you were camping in an area with four hours of sunlight, so your panel that generated 3 amps per hour gave a total of 12 amps per day. Thus, the 12 amps drawn per day for all appliances divided by the 12 amps generated per panel = 1 panel.

Answer: You need one panel.

If your problem is more complex, you can always pick up the telephone, dial (916) 265-8441, and ask for Jon Hill, a mechanical engineer who is one of the top solar experts in the United States.

Mr. Hill puts out an 88-page publication, ``The 1989 Electrical Independence Guidebook and Catalogue,'' which gives an idea of the array of products available for travelers interested in solar vacations. To receive a copy, send $4 to Integral Energy Systems, 105 Argall Way, Nevada City, CA 95959.

Hill suggests that travelers control the start-up costs of a solar array by limiting the number of appliances they take. ``Vacationing with solar panels offers travelers independence, peace, quiet, and convenience,'' says Hill. ``But they should still remember to keep it simple. After all, if you want a real vacation, don't take every gadget you own with you.''