Solar Energy

The possibilities for using solar energy are limitless.  At a basic level, solar energy can passively heat and provide light for buildings, distill water, and cook food.  Active strategies, incorporating photovoltaics, pumps, and fans to change energy outputs, generate electricity, heat water, heat and cool buildings, and power cars, boats, and even planes. 

Solar Electric:
Solar electric is one of the most common forms of solar energy.  Solar electricity is produced by converting sunlight into power using the photovoltaic effect where an electrical current flows though a solar cell when the cell is exposed to sunlight.1 A solar panel is a combination of many solar cells together into a unit.  A collection of these units makes a solar array, and multiple arrays make up a solar electric system.

Panels:
There are two types of solar panels: crystalline silicon and thin film.  Crystalline silicon photovoltaics are rigid panels that perform well in low light conditions and are very efficient.  Thin film, though less efficient, are also less expensive to produce than crystalline panels.   Thin film is a flexible, thin layer of silicon spread over a plate of glass or ceramic.  Film is ideal for building integrated photovoltaics such as solar tiles and shingles and PV glass.

Solar Electric Systems:
A solar electric system usually consists of solar panels, an inverter, a battery, a charge controller, and wiring.  The inverter is used to convert electricity produced from direct current (DC) to alternating current (AC) power.  A battery collects excess electricity and stores it for use during power outages, cloudy days, or night use and is protected from overcharging by the charge controller. 

Systems can be connected to the grid, connected to the grid with battery backup, or off-grid.  A grid-connected system is used to decrease the normal power supply from the utility company and does not include a battery to store excess power.  This system relies on a normal power supply for cloudy days, night use, and periods of high electricity use.  Excess electricity is not stored but can be sold back to the utility company for credit. 

A grid-connected system with battery backup is like the grid-connected system though an storage battery pack is included to store excess energy.  The stored electricity is used when the system is not generating enough electricity.  The system is still connected to the grid to supplement the system when additional power is needed.

Off-grid systems are usually found in remote areas where it is more expensive to connect to the utility grid.  These systems are completely independent from power lines and are often the main power source for the home.  Batteries are used to store excess power and are often supplemented by wind turbines, generators, and/or backup fuel sources.2

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1. US Department of Energy: Energy Efficiency and Renewable Energy, “Your Own Power: A Consumer Guide to Solar Electricity for the Home,” http://www1.eere.energy.gov/solar/pdfs/43844.pdf.
2. Ibid.

 

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