Solar Energy

You may have noticed those shiny panels on rooftops, calculators, and even on some watches - but how do solar photovoltaic panels work?

A solar panel consists of a collection of photovoltaic (PV) cells. The PV cels are made of crystals of silicon, a non-metallic chemical element, and the second most abundant element is the earth's crust. The silicon is extracted from sand.

Large silicon crystals are then cut into thin wafers, and fused together. However, the two separate wafers are composed of two different materials, with distinctive properties - so, when sunlight hits the solar cells, photons dislodge electrons that travel from one layer to the other. Silicon, in its pure state, is a poor electrical conductor, but during the manufacturing process an impurity is added so that when the photons (light) lands on the wafer, electrons are released and create electrical current. This movement, the flow of electrons - is electricity!

The electrical output is affected by many things including: the angle of the PV panels to the sun, the time of the day, the time of the year, weather conditions, and the atmospheric content. The electricty that is generated by the PV panels is then sent to a charging unit, which in turn keeps a battery pack fully charged. The battery pack then sends the electricity into your house!

If you link many PV panels together - you can create a great amount of electricty! Enough to power your home, or an office building, or even a car. And PV panels are continuing to drop in cost - the price has dropped 200% over the last 30 years!

Solar thermal uses technology to harness infrared energy from sunlight to capture and store heat. This stored heat is released later to warm water and air, or on an even larger scale, to generate steam which in turn powers a turbine.

While solar thermal electric power isn't as well known photovoltaic (PV) technology, it has great benefits and we may be hearing much more about it very soon. What makes solar thermal different than solar PV is that it uses technology to harness energy from the sun in the form of heat. It works on the basic principle of concentrating the sun's rays to capture and store the most amount of heat possible. It's the same theory behind using a magnifying glass to ignite a blade of grass, just on a much larger scale!

Many people use solar thermal energy at home - whether directly, as a means to heat their swimming pools or the air in their homes, or indirectly by using solar collector plates. The indirect process is a little more complicated:

• First, a solar collector plate catches and absorbs the sun's light. The solar collector plate has a transparent cover and a heat insulating backing.
• Then a fluid, either water or glycol, flows through the collector, usually in tubes.
• Finally, heat is transferred and water is collected in an insulated tank to be used in your home.

The solar heat captured by the collector and stored in a water tank can be used for hot water or circulated in radiant floor tubing or baseboard radiators. And even existing homes can be converted to use radiant floor heating.

Worldwide, solar thermal power plants are most popular in the United States. The largest solar power plant of any kind is located in the Mojave Desert, and can produce the same energy equivalent of a mid-sized coal plant.

These facilities typically use mirrors to focus the sun's rays on a focal point, which is designed to absorb a high degree of heat. This intense heat is then used to boil water to create steam which is used to turn turbines and generate electricity. The theory is just like power plants that use fossil fuels as a heat source to boil the water - instead, they just use the sun!