Photovoltaic Systems and NREL

Photovoltaic history

            How Do Photovoltaics Work?

Photovoltaics, made of a special semiconductor material, directly convert sunlight into electricity.

PV cells connected electrically to form modules (up to 100 watts).

Modules connected into arrays.  

            PV applications

1.      Water pumping, lighting, communications, utility grids, household appliances, etc.

2.      More cost effective: Decreasing cost of system and increasing number of manufacturers.  

            Benefits of PV systems

                      Photovoltaic systems are highly reliable, requiring little maintenance and low operating costs. Though some pollution is associated with their production, operation of photovoltaics is non-polluting.  PV systems provide a secure energy source whose modular capabilities allow it to be sized to the needs of the user.

Obstacles for photovoltaics

The largest obstacles currently facing photovoltaics are the relatively low prices of energy derived from coal, oil and natural gas, and poor conversion efficiencies with battery storage systems necessary for saving power for nighttime and cloudy days. 

PV potential

Production of photovoltaic modules has tripled in the last 7 years. In 1996, almost 90 MW of modules were manufactured worldwide.  

             National Renewable Energy Laboratory (NREL)

The goal at NREL is to make photovoltaics a major contributor to global energy portfolio.  They are developing prototype solar cells to improve cell efficiency, utilize less expensive manufacturing technologies, and test cell and module performance.

They are also conducting some cell and material research.  Currently, 95% of the modules are made from crystalline silicon cells.  The rest are made from a thin film technology that is not as efficient as crystalline silicon cells, but uses 30-100 times less semiconductor material and is easier and cheaper to produce.  

The NREL site contains an outdoor test facility where more than 3,500 tests are done annually.  More than 100 different modules are tested and evaluated for performance.  There is also an indoor test facility.  The High Bay Test Lab tests performance in varying weather conditions (heat, cold, humidity, moisture, UV-light) and uses an accurate hail simulator.  The Large Area Solar Simulator Lab determines the electrical output performance of PV cells and also measures module conversion efficiency.  The Exploratory Diagnostics and Failure Lab tests the performance in high voltage and wet conditions and verifies electrical insulation.

NREL has achieved several accomplishments:

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