Utrik may be a model in miniature for the fate that might await the rest of the world in the United States, the main source of energy is fossil fuels —petroleum, natural gas, and coal fossil fuels contribute 85% of the energy that we need to light our homes, power our cars, and cook our meals. But we will eventually run out of fossil fuels. Also, many countries — including the United States — need to import fossil fuels because they are found only in certain parts of the world. Another problem with fossil fuels is that burning them releases carbon dioxide, a greenhouse gas that contributes to global climate change.
A promising alternative to fossil fuels is solar energy. The total human population on earth currently uses about 13 terawatts (1 terawatt equals one trillion watts) of energy. This is only 0.01% of the 120,000 terawatts of energy delivered by the sun to the surface of the earth. If we could only find a way to harness even a fraction of this solar energy, we could solve our energy problems.
Converting sunlight into electricity
To produce electricity from the sun, all that is needed is a small device called a solar cell, which converts solar energy directly into electricity. To power a house or a building, solar cells are combined into modules and arrays to form solar panels (Fig. 1a, 1b).