Converting Solar Energy to Electricity

How Solar Cells and Solar Thermal Plants Turn Sunlight into Power

The sun provides plentiful and free energy. It is a renewable energy source, because it comes from a resource that will not deplete or run out, unlike oil or coal. Solar panels do not produce carbon dioxide or other harmful emissions. They also do not require water to generate electricity, which can save water resources.

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

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 1 to 2 watts. For that reason, they are used to power devices close to the cell. In many cases, solar cells are an integral part of the device. Examples include solar-powered calculators and garden lights.

Several solar cells are connected in a module to provide energy to large devices such as lamps and appliances. The modules are placed side-by-side in an array or panel, and finally, the panels 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 labour vary greatly depending on the array’s size and the home’s energy demands.

Solar cells are an efficient source of power. Around 23% of the energy that falls on a cell in the form of sunlight gets converted to electricity.

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 30% or higher range. However, these discoveries have mostly remained at the experimental stage, and have yet to prove to be commercially viable.

Solar Thermal Plants

The sun’s energy is first collected via curved or flat mirrors in a solar thermal plant. 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 ever-growing energy demands and reduce dependence on fossil fuels. Both will undoubtedly be more widely deployed in the future.