Solar Photovoltaics 

Topic outline:

Overview:

Solar Photovoltaic (PV) Panels take advantage of the photoelectric effect to generate electricity.  This page gives a background of photovoltaics development.  For a detailed explanation of the physics involved, please see photovoltaic physics. For a systems view and economics of photovoltaics, please see photovoltaic systems.

Types of PV Cells: 

1st Generation (monocrystalline silicon)

Monocrystalline silicon cells can be made by growing crystals and cutting them into wafers. These are very efficient, but expensive!

2nd Generation (hybrids)

Second generation PV materials can absorb multiple frequencies of photons in order to excite more electrons and make more electricity, thus increasing the efficiency of the PV system. Other second generation materials, such as amorphous silicon, are less efficient (4-8% in the field), but much cheaper. Production of inexpensive materials (at the expense of efficiency) could be a key to making solar PV technology more widespread and affordable. 

3rd Generation (fine tuning Nanoscales)

Includes improvements in crystalline structures and materials to better harness light photons and funnel it to excite the more electrons more efficiently. PV cells have continued to improve since 1975.

The following graph shows the progression of material efficiencies over the past several decades. Note that Boeing has achieved efficiencies greater than 40% in the lab.

Solar PV - Historic Growth:

Figure - Solar PV growth. 

Prior to 2000, most PV installation was driven by off-grid rural applications where grid power was not accessible.  After 2000, the majority of the growth has been in on-grid systems.  Additionally, the cost ($/watt) has been fairly constant since 1987 with production ramping up precipitously since 1997.  In order to make solar competitive with wind, the cost needs to be reduced from $4/watt to $1/watt.

PV by Country

The big three in PV production are Japan, the U.S. and Germany in that order.  Although China is not a dominant producer of PV panels, it is the primary producer of the rare metals used in PV cells.

References:

PV Picture: http://www.boatownersworld.com/lake_lite/images/solar-panels-sun.jpg

Wikipedia: http://en.wikipedia.org/wiki/Photovoltaics

Solar Cell Materials: http://en.wikipedia.org/wiki/Solar_cell

Text Book: Renewable Energy: Power for a Sustainable Future, by G Boyle