Although the traditional concentrators can reduce the amount of solar cell

they need high accurately tracking system. On the other hand

the spectrum of solar is very wide

while the absorbing spectrum of photovoltaic is narrow. So a lot of energy will be lost. In order to overcome these drawbacks

the later non-imaging optical system was studied. The concentrators with large accept angle and splitting characteristic was designed. This kind of concentrators can form high efficiency

non-tracing and portable PV modules

combined with solar cell. They can used as power of some special devices such as portable computer

imaging and measuring system

and so on.