The basic idea here is to essentially take a large collecting area and focus it on a smaller area, thus concentrating the energy. This means that less PV material will be required to produce a given amount of energy and this, potentially, saves expenses.

Projected Expense savings are large:

• 100 MW year regular PV facility is 150-300 Million dollars capital cost
• Using Concentrating PV (CPV) that costs lowers to 30-50 Million dollars

And its catching on

The issue then becomes the reliability of the CPV components over time. Also CPV systems function best under clear sky, direct-sun conditions. Early installations were made in Saudi Arabia, Arizona and at Alice Springs, Australia.

The primary potential problem here is heat load and subsquent failure of the PV material.

Additional considerations:

Several advantages of concentrator PV systems, as compared to flat-plate systems, can be enumerated. Concentrator systems increase the power output while reducing the size or number of cells needed. An additional advantage is that a solar cell's efficiency increases under concentrated light. How much that efficiency increases depends largely on the design of the solar cell and the material used to make it. Another advantage is that a concentrator can be made of small individual cells. This is an advantage because it is harder to produce large-area, high-efficiency solar cells than it is to produce small-area cells.

However, several challenges exist to using concentrators. For example, the required concentrating optics are significantly more expensive than the simple covers needed for flat-plate solar systems, and most concentrators must track the sun throughout the day and year to be effective. Thus, achieving higher concentration ratios means using not only expensive tracking mechanisms, but also, more precise controls than those of flat-plate systems with stationary structures.

Various Designs:

Linear Reflector:

Solar Thermal Towers uses these arrays.

Linear Fresnel Lens:

Can be made Large

Point Focus Array:

Most Expensive but can track the sun.

Solar concentrator technologies potential offers significantly higher efficiiencies (again these are all measured in the Lab at 0 degrees C).

Many commercial systems now use something called a parabolic trough: , Here the focus point of the parabolic trough is a receiver pipe. The pipe is filled with oil (not crude oil) and is heated to about 400 C. This heat energy is then used to generate electricity in a conventional steam generator.

35 KW module

A real promising hybrid solution:

The New Shopping Mall:

And These guys hype this technology to the max. But 2500 Suns is a very high concentration ratio and likely will produce large scale failures over time.

Within CPV systems, the concentration rato can have high variance.

If light that falls on 100 sq. cm of reflector surface is focussed onto a 1 sq. cm surface of PV material, then the concentration ratio is 100. Current commercial design concentration ratios are in the range 200-300 suns.