With the sun and a few simple components, you too can make "green" projects.
Alternative energy sources and "green jobs" have been in the news and are often cited by President Obama as becoming the wave of the future. If alternative energy sources like solar power are a mystery to you, there is a simple way to take the mystery out of the concept. Using readily available hobbyist equipment, you can make a solar-powered fan; you will see how a simple solar power system works and learn its advantages and weaknesses.
What Is a Solar Panel?
Solar panels power electronic devices in locations where other electricity may not be available.
Solar panels are semiconductor devices which convert sunlight into electrical current. In a way, they operate like small batteries, in that each individual cell puts out a small amount of direct current (DC) at a low voltage. Like battery cells, these solar cells are stacked to give a useful current at a low voltage.
Also like batteries, these cells may be connected in series to give a higher effective voltage, connected in parallel to give greater current at the same voltage or connected into an array to boost both voltage and current.
What Can You Do with Solar Electricity?
Again, think of the output of your solar cells just as you would the output of a battery. The main difference is that your battery will supply power when exposed to sunlight and will do so again the next day.
You can wire the output of your solar panel to any electric or electronic device (such as a fan motor) that you could run with a battery. In the case of this project, you will connect the positive output of your solar panel (+, or sometimes a red post of your solar panel power output) to the + input post on your low-voltage DC fan motor, and the negative (--, or black post of your panel output to the motor's -- post) to your fan motor. When the face of your panel is fully exposed to sunlight, the motor will turn and the fan blade you put on the motor will drive air.
When you choose a solar panel, be certain that the panel's output voltage is equal to or greater than the minimum DC voltage needed to drive your DC fan motor. Small DC motors often come with an effective voltage range, such as 3 to 12 VDC. You may have to use two or three of the low-priced hobby solar panels to meet the minimum voltage needs of your fan.
What Comes Next?
Having assembled your solar panel and fan, try a few experiments. These will show you some of the uses and limitations of solar power.
Expose your solar panel to full, direct sunlight and note how fast the fan runs. Now partially shade the panel. If your solar panel is an amorphous type (made from a silicon "paste" spread on a metal panel), the fan will run more slowly. If your panel is a mono-crystal or poly-crystal (usually the higher-voltage types--either single piece or "shattered glass"-looking silicon panels), completely shading a full row of cells will cause the fan motor to stop completely, even if the rest of the panel is in full sunlight.
The next step is to add a small DC battery (such as used in riding lawn mowers). Use enough solar panels to deliver the battery's rated voltage (6 VDC should be enough to start with) and connect the panel directly to the battery. Then connect the battery to the fan. The solar panel will drive the fan and charge the battery during the day and continue to run after sundown until the battery is completely discharged. If the fan is running too slowly or the battery discharges too soon after sundown, add more solar panels (in parallel) to increase your current production during the day and give your battery more of a charge.
A popular way to use solar-powered fans is to mount the fan in an attic vent and mount the solar panel on the roof for full sun exposure during the day. This system will drive the attic fan to expel hot air from the attic during the day and will turn itself off around sundown.
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