Initial System Design Presentation I

Power systems

Presentation topics

Solar energy How solar cells work Different types of solar cells available

Solar Energy

Solar Constant : Integrated energy under the Air mass Zero ( outside the Earth’s atmosphere ) curve.

Accepted value till 1990s = 135.3 mW/cm^2

Recent measurements shows it is 136.6 mW/cm^2

The difference in Earth-sun distance between perihelion and aphelion results in solar constant variation of +- 3.5% of 136.6 mW/cm^2

When a solar cell gets illuminated , electron – hole pairs are produced throughout the base region below the junction to a depth that is dependent on light’s wavelength.

Longer wavelengths have more penetrating power.

Back Surface field ( BSF) layer is introduced to reflect back minority carriers that are diffusing away from the junction.

Back Surface Reflector (BSR) layer is there to reflect protons.

BSFR cells are better.

Multijunction cells

Such cells have reached efficiencies of around 35% under concentrated sunlight.

The first spacecraft to use solar panels was the Vanguard 1 satellite, launched by the US in 1958. This was largely because of the influence of Dr.Hans Ziegler, who can be regarded as the father of spacecraft solar power.

http://s1.zetaboards.com/UTD_Cube_Satellite