How Does Solar Work?

Solar photovoltaic (PV) convert energy from the sun into direct current energy using semiconductors like silicon that generate a stream of electrons by means of the photovoltaic effect.

What is the photovoltaic effect? Scientists have observed that many metals will emit electrons when exposed to light. Indeed, Einstein won his Nobel Prize for his work on the photovoltaic effect, not for relativity. When photons hit metals with a sufficiently high atomic number the atoms line up in a crystallized fashion and electrons are released in a current.

What metals convert sunlight to electrons? A number of single elements and hybrid metals have proven to be effective including monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, copper indium gallium selenide/sulfide. These elements are deposited onto a glass substrate to form a “solar cell.”

Source: Solar Energy Industry Association. Illustration by Kurt Struve

How are the electrons transmitted? Copper wire is used to capture the current generated in the solar cell. A single solar cell generates approximately 4-5 watts of direct current per hour of direct sunlight.

What are solar panels? Solar cells are combined into modules. These generally contain an array of 6 x 10 cells and generate about 240-300 watts.

Source: Office of Energy Efficiency and Renewable Energy

What is a solar array? Solar modules are combined in a series to form a solar array. Modules are combined in a string.

How is Direct Current converted? U.S. electric grids and most building equipment and appliances use alternating current (AC). Direct current (or DC) is converted to AC in an inverter. Inverters may be used in a base station that converts all or some of the DC produced by a string of modules. Alternatively, micro-inverters may convert the electricity of each module separately. In addition to “inverting” DC to AC, inverters also help to monitor the energy flows from the panels to the grid.

How much power do solar panels produce? Power production is a function of the exposure of the solar cells to sunlight (insolation). The amount of insolation is influenced by a number of major factors:

  • Geography (i.e., latitude and altitude)
  • Time of day
  • Season (e.g., sun is lower in the winter)
  • Weather (e.g., cloud cover)
  • Presence of shade or obstructions
  • Orientation to sun
  • Angle to sun

Source: National Renewable Energy Laboratory

panels such as:

  • Water vapor
  • Dust
  • Pollutants
  • Forest fires, volcanoes, or other extraordinary events.