Date:         Sun, 17 Jun 2007 17:24:13 -0300
Reply-To:     David Etter <detter@MAIL.AURACOM.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Etter <detter@MAIL.AURACOM.COM>
Subject:      Solar panel basics
In-Reply-To:  <d0c.128354cc.33a672e8@aol.com>
Content-Type: text/plain; charset=us-ascii; format=flowed

This (in part) is from a now defunct web-site a few years ago but
although dated, is still somewhat helpful.
                                                David(dsl82westy)

Solar Panels

                How do they work?
        To be brief, energy from the sun's light strikes the solar
panels crystals knocking some electrons loose and creating
electricity. Each solar cell in a panel creates a potential of about
.45 volts. To create a voltage sufficient to charge a 12 volt
battery, 34 to 36 cells are connected in series to produce 15 to 17
volts. The current a panel is capable of producing is porportional to
the area of each cell. Larger cells produce more electricity.


How much output can I expect from a solar panel?
        We use a basic design rule that a solar panel will
contributer about 30% to 35% of its wattage in amphours each day if
the panel is directed toward the sun.  This means that an 80 watt
solar panel can be expected to produce approximately 24 to 28
amphours per day when aimed at the sun.


What type panel is best?
        There are three main types of solar panels: Monocrystalline
(Siemens), Polycrystalline (Kyocera, Solarex, PowerValue), and Thin
Film or amorphous (Uni-Solar).
        Monocrystalline panels have uniform dark gray cells and have
the highest output per cell area and tend to be the most expensive.
        Polycrystalline cells look somewhat like shattered glass and
tend to be less expensive and only slightly less efficient per cell
area. These cells are usually square and result in a slightly smaller
solar panel than solar panels constructed using the more efficient
monocrystalline which tend to be rounder.
        Monocrystalline and polycrysalline solar panels are rigid and
have a glass cover. Thin Film type panels are made by depositing the
active silicon on either a stainles plate or a flexible backing.
        Thin film type panels are about half as efficient per cell
area but are consided unbreakable and shadow protected.

Do solar panels require regulation?
        As a general rule, very small solar panels that put out 5
watts or less can get by without a regulator but a regulator should
be used on all solar panels. The self-regulating panels produce less
voltage and theoretically will not overcharge your batteries. We
would rather use higher voltage solar panels and use a regulator
which is quite inexpensive to buy and it can save your batteries.