CHAPTER TWOThe Workings of a Modern Solar Energy System
In order to understand how a solar energy system works, I need to show you how a typical solar cell turns the sun's rays into an electrical current. The radiation emanating from the sun consists of photons. They travel to the earth at the speed of light. When photons hit a solar cell that's part of a solar panel, the silicon in the cell absorbs them. This causes electrons that were happily spinning around on their atomic orbit to get excited. Once a photon strike excites an electron, one of two things happens: The electron can dissipate the energy caused by the strike in the form of heat and return to its orbit, or the electron can move through the cell until it strikes an electrode. That strike generates an electric current. This current flows through the cell layers.
The vital part of the process is the chemical bonds of the various layers. There are usually two layers of silicon, one bonded with phosphorus and the other with boron. The two layers have different electrical charges, one positive and one negative. This difference allows electricity to flow between them as photons strike the surface of the cell. Solar cells create direct current (DC) electricity. Later in this chapter I'll discuss how DC electricity is converted to the alternating current (AC) electricity that we use at home and at work.
HOW POLYCRYSTALLINE SILICON SOLAR CELLS WORK
Scientists used silicon wafers to make the first generation of solar cells. ...