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Chapter 2: How Solar Panels Work

A photovoltaic module or solar panel captures light energy in the form of photons from the sun and releases that energy through the emission of electrons. A basic system is comprised of the solar paneling module, an inverter, interconnecting wires and a battery. The solar panels capture light and transmit it through conductive wiring to the inverter. The function of the inverter is to change the current from direct current (DC) to alternating current (AC).

Direct current is the type of current that flows through battery-powered devices. It is characterized by a continual flow of electrons in one direction. With alternating current, the electron flow periodically changes directions at regular intervals or cycles. Standard electrical power through power lines and into homes and businesses is alternating current. One of the advantages of alternating current in these capacities is that the current may be propagated for longer distances without losing power. Additionally, its voltage is more readily adjustable than that produced by direct current; this adjustment utilizes a device called a transformer.

After current generated in solar panels is adjusted by the inverter from DC to AC, it is transmitted further along conductive wires. It may be used immediately or it may be stored in a battery until needed (where it again becomes accessible as direct current).

Newer models also employ the use of concentrators, which are traditionally systems of mirrors and tracking devices that focus the incoming sunlight onto a specific area in order to intensify the energy generated. This creates a concentrating photovoltaic cell (CPV), which is more energy efficient and more cost effective than a traditional photovoltaic cell (PV). Lens-based CPV technology is most efficient in sunny weather, as cloudy and overcast conditions produce diffuse light which is more difficult to concentrate.

An alternative concentrating method, still in development, is the luminescent concentrator. Luminescent solar panels are characterized with plastic components painted with a mixture of dyes. The dyes absorb sunlight and redirect it within the glass at different wavelengths. An advantage of this technology is that it does not require that the solar concentrator be pointed directly at the sunlight.

Solar panels may be connected either in series or in parallel. With parallel wiring, positive terminals are connected to positive terminals and negative to negative. Parallel circuits generate constant voltage but additive amperage; in other words, the total amps produced by the system are the sum of amps produced by individual solar panels.

In series solar circuits, the solar panel terminals are connected positive to negative. In contrast to parallel circuits, series circuits produce constant amperage but additive voltages. Because solar panel systems are modular, different numbers of solar panels may be selected and wired in series, in parallel, or a combination of the two. This enables the installer to optimize the total number of volts and amps generated for the specific system. It is also critical to select the appropriate wire type and size; this ensures maximal efficiency and safety of the system. Wiring choices are mandated by current electrical codes, and all new solar power systems installed residentially or commercially are required to be electrical code compliant.