Photovoltaic Energy: CPV vs. CST

You might think that every solar power plant is about the same as every other one. You’d be wrong.

A solar power plant works most efficiently when sunlight is concentrated. A solar power plant system may be a concentrated  solar thermal type (CST), use concentrated photovoltaic cells (CPV), or operate with a combination of the two (CPT).

You may be surprised to learn that the principles of concentrated photovoltaic solar energy goes back a long way; in fact, the Chinese were experimenting with solar power some 2000 years ago. According to legend, the Greek scientist Archimedes actually caused the ships of an invading Roman fleet to catch fire using the principles of concentrated solar energy – something that was actually recreated by a Greek scientist in the early 1970s. Solar collectors have been used to generate power since the late 19th Century, but it wasn’t until the late 1960s that technology had advanced to the point that such methods of generating power were made practical.

A CST plant uses a variety of parabolic mirrors and focusing lenses in order to concentrate solar energy and direct it into a small area, generating enough thermal heat to boil water. This boiling water in turn runs a turbine that operates an electrical generator, much in the same way a coal or oil-fired plant does.

A concentrated photovoltaic solar energy plant concentrates sunlights onto photovoltaic cells, thus generating electricity directly rather than using the energy to heat water. Because of the unique properties of the silicon compounds that are used as semiconductors in photovoltaic panels and because the electricity is being generated directly, the CPV is actually more efficient under most conditions.

However, most solar plants employ both types, and each has distinct advantages. CST is better for the production of hot water and direct climate control (heating as well as cooling). CPV is more efficient at producing direct electrical energy that can be stored for later use.

Expense has been the most immediate barrier to the expansion of the CPV and CST type of solar generation; in 2009, the price tag of constructing such a facility generating 250 megawatts would require an initial investment of between $600 million and $1 billion. Currently, this would cost consumers between .12 and .18 cents a kilowatt hour. However, as solar technology continues to advance, this cost is expected to fall to under .05 cents per kilowatt hour within the near future – possibly as soon as 2015.


Post time: 05-06-2017