Converting Solar Energy to Electricity

How Solar Cells and Solar Thermal Plants Turn Sunlight into Power

Feb 25, 2009

The sun provides plentiful and free energy. This article outlines the two principal methods used today to turn this energy into electrical power.

Solar energy is captured through two main methods: photovoltaic cells and solar thermal installations. Here is an overview of each method.

Photovoltaic Cells

Photovoltaic cells, also called solar or PV cells, directly convert the sun's rays to electricity. A single solar cell produces a small amount of electricity, generally in the order of 1 to 2 watts. For that reason, it is used to power devices in close proximity to the cell. In many cases, solar cells are an integral part of the device. Examples include solar-powered calculators and yard lights.

To provide energy to large devices such as lamps and appliances, several solar cells are connected together in a module. The modules are placed side-by-side in an array or panel, and finally the panels themselves are connected to one another to generate sufficient power for the device.

Generating enough electricity to power a house requires several hundred square feet of solar panels. As each house must be custom-fitted with panels, the cost of materials and labor can run to tens of thousands of dollars.

Solar cells are relatively inefficient sources of power. Only 12%-15% of the energy that falls on a cell in the form of sunlight gets converted to electricity. By contrast, modern hydroelectric power plants have efficiencies of 90% or more.

Many corporations, universities and institutions around the world are studying ways to increase the efficiencies of solar cells. There have been occasional breakthroughs in raising efficiencies to the 25% or higher range. However, these discoveries have mostly remained at the experimental stage, and have not proven to be commercially viable.

In a solar thermal plant, the sun's energy is first collected via curved or flat mirrors. The mirrors direct the sunlight to a central spot, which may be a tube containing oil, a tower filled with molten salt, or any kind of engine that stores heat. The heated medium then directly or indirectly drives a conventional generator that produces electricity.

Solar thermal plants can generate electricity in amounts as high as hundreds of megawatts. And because solar thermal plants produce electricity through heat, they can generate electricity even when there is no sunlight. This gives such installations an advantage over solar cells, which can only create small quantities of power in the presence of sufficient sunlight.

Another advantage of solar thermal plants over solar cells is that the power can be produced in one location and then spread over a large area. This leads to cost-efficiencies in both production and distribution.

Solar cells and solar thermal plants have their unique advantages and disadvantages. However, both technologies can, in their own ways, help meet the planet's energy demands and reduce dependence on fossil fuels. Both will undoubtedly be widely deployed in the future.

The copyright of the article Converting Solar Energy to Electricity in Energy Conservation is owned by Arun Sinha. Permission to republish Converting Solar Energy to Electricity in print or online must be granted by the author in writing.