If you have ever used mirrors and a magnifying glass to start a fire, you have a pretty good idea of how concentrated photovoltaic systems operate. Using these elements, sunlight is concentrated, amplified and focused onto concentrated photovoltaic solar panels or a transfer fluid duct, creating the heat needed to power an electrical generator.

Although the use of magnifying glasses to intensify solar rays may go back 2200 years and parabolic troughs were first used to boil water was in 1866, it wasn’t until the late 1960s that these two elements were combined. Built in northern Italy near the city of Genoa, this early attempt to concentrate solar energy produced 1 megawatt of electrical energy by heating steam to over 1,000 degrees Fahrenheit.

Today, the largest concentrated photovoltaic solar power facility is located in Southern California. Generating over thirty-five times the amount of energy supplied by the Genoa plant, the Solar Energy Generating System (SEGS) puts out 354 megawatts and is still one of the largest solar power stations in the world.

These facilities are constructed in a number of different ways; parabolic troughs are only one of them. There are also dish systems, which use solar heat more directly and make heat transfer unnecessary. This heat is used to power what is known as a Stirling Engine, which operates by the expansion of gas or fluid as it is heated. Fresnel lenses, similar to those used in video projectors, may also be used to concentrate sunlight into a small area.

However, the heart of the most efficient systems is the concentrated photovoltaic panel onto which this sunlight is directed. Rather than using the sun’s energy indirectly to boil water or run a Stirling Engine, concentrated photovoltaic systems generate electrical energy directly. This essentially cuts out a step, creating much greater efficiency, since when heat must be transferred, some is inevitably lost in the process.

The only drawback is that concentrated photovoltaic solar panels must be mounted on some type of tracking device so that the sun’s rays remain focused on the panels’ surfaces over the course of the day. Currently, new alloys are allowing for efficiencies beyond 40%; it is projected that further advances in solar energy technology will eventually allow an efficiency rating of up to 50% within the next few years.