SunWind Energy Lessons

Solar cell electricity is direct current (DC) electricity - it flows in one direction. When a solar panel is attached to a motor, the motor can be made to spin in the reverse direction by reversing the connections at the back of the motor.

No harm will result if the clips are "shorted" on a single solar panel. While electricity will flow, according to the amount of sunlight, no damage results to the cell, nor will the wires wear out. These solar panels will not harm each other if hooked together in any combination.

Solar cells and panels can be hooked up in series (positive to negative - adds voltages together) or parallel (positive to positive, negative to negative - adds amperages together) circuits.

The solar cell reaction has an electrical potential of approximately 0.5 volts. If we add two cells together in series, we get 1 volt. Higher voltages are obtained by linking many cells in series. Voltage is the measure of potential energy each electron has in the electrical field formed within the electrical circuit. Amperage is a gross measurement of how many electrons are flowing. Together they are like a waterfall, with voltage being like the height of the water fall, and amperage being like the amount of water flowing over the waterfall's edge. At the bottom, where the water splashes down, we have power according to how far the water fell into the gravity field, and how much of it fell each moment (time).

Normally we must turn an electromagnetic generator with physical force to obtain electrical energy. Or, discharge a chemical battery.

Solar-generated electricity is different - the power comes from light, and the reaction in the cells is not chemical, but electrical only. The atoms remain the same, and are not involved in chemical reactions. What are affected are the electron clouds of the silicon crystals, as photons of light energy are absorbed. When two layers of differently doped purified silicon are joined, immediately an electrostatic field with a potential of 0.5 volts is formed at their junction. Because it is rather tricky to achieve in our three-dimensional world - having a photon strike an electron on the P-side of the electrical junction of two layers of differently doped purified silicon - and very close to the junction to boot - solar cells are only about 12 - 15 % efficient in changing light energy into electrical energy. That is, only about 1/8 of the solar energy striking the panel gets converted to electricity.

The photovoltaic panels supplied by SunWind generate 1 volt 400 mAmp in full sun. They are comprised of two 400 mAmp cells wired in series (positive to negative) to make 1 volt. Increasing the voltage will generally increase the speed at which an attached motor will spin.

If cells, or panels, are wired in parallel, their amperages are added together. The amperage of a solar cell is determined by the cell quality and area of the cell, and the amount of sunlight striking the cell. If two of these 1 volt 400 mAmp panels are connected in parallel, 800 mAmps of 1 volt electricity could flow through a connected device, which might be useful if the device needs some low-end power. And, if it is a cloudy day, the motor would still be getting SOME electrons to run on. There is a generally direct relationship between the amount of sunlight (number of photons) striking the cell, and the amount of electricity (number of electrons) produced.

Try shading the panels in different ways and observe what sort of shading lets the motor run, and what stops it completely. Clue: if the voltage of one cell is brought to zero, can the voltage of the other cell pass through it?

In larger photolvoltaic panels, where many individual cells are added together to achieve voltages of 18 or more, what might happen if leaves shaded just some of the panels?