As we transition from spring into summer in this era of renewable energy, the exuberant warmth of the sun brings with it many benefits, including solar energy. Sunlight is the most abundant energy resource on earth, and it has been used by humans for thousands of years for staying warm and drying foods to preserve them. The sun’s rays are so plentiful that 173,000 terawatts of solar energy, which is greater than 10,000 times the world’s total energy use, strike the earth continuously.
What Is Solar Energy and How Does It Work?
Photovoltaic (PV) cells, also known as solar cells, collect and then change sunlight directly into electricity. The cells can be tiny enough to power a single watch or other small electronic device. Several cells in PV panels and arrangements of PV panel arrays can produce enough electricity for an entire house. Or a power plant spanning several acres with large arrays of PV panels is capable of powering entire communities.
Photons are the particles of solar energy that make up sunlight. They have varying amounts of energy related to the different wavelengths of the solar spectrum. When photons encounter PV cells, they either reflect off the cell, pass through it, or are absorbed into semiconductor material contained in it. The absorbed photons provide the energy to generate electricity. When enough sunlight is absorbed, electrons are dislodged from the material’s atoms.
The movement of electrons carrying a negative charge toward the front surface of the solar cell creates an electrical charge imbalance between the front and the back of the cell, which fosters a voltage potential much like that of the negative and positive terminals in a battery. Electrons on the cell are absorbed by electrical conductors. When the conductors are connected in an electrical circuit to an external load, electricity flows in the circuit.
Although there is an abundance of sunlight, the percentage of conversion to electricity via commercially available PV cell modules is generally between 5% and 15%. There is still much research to be done to achieve higher efficiencies.
We’ve Been Using Solar Power for How Long?
The solar oven, used in the 1830s by British astronomer John Herschel to cook food while on expedition in Africa, is one of the earliest examples of a solar collection device. Since then, a variety of solar collection devices have been developed for multiple uses.
Solar power’s unprecedented growth has made it an increasingly popular source of renewable energy. In fact, the first silicon solar cell, which was the precursor of all modern solar-powered devices harnessing the almost limitless energy of the sun and propelling technology into the renewable energy era, was built in 1954 by Bell Laboratories.
Another early use of solar energy which also served as proof of the viability and reliability of the source, is the Vangard 1. Powered by solar cells, it is the oldest manmade satellite still orbiting the earth today.
Technological advances, government policies, financial incentives and decreased cost have helped to expand solar energy use significantly since the 1990s. Hundreds of thousands of PV systems are now installed in the United States and the U.S. Energy information Administration (EIA) estimates that electricity generated in PV power plants increased from 76 million kilowatt hours (kWh) in 2008 to 63 billion kWh in 2018.
The Good and the Bad
Aside from being a plentiful and ongoing resource, there are other benefits to solar energy. Solar energy systems don’t produce air pollution, nor do they produce carbon dioxide, and the systems attached to buildings have very minimal effects on the environment.
However, despite being a very clean energy source, solar energy has its downfalls. The amount of sunlight hitting the earth varies significantly depending on location, time of day, time of year, and weather conditions. And the amount of sunlight that touches a square foot is small, thus a large surface area is required to collect a useful amount of energy.