Rockingham Photovoltaic Trough Concentrating System

What are Solar cells?

Solar cells are used to convert solar energy into electricity.

The most common form of solar cells are based on the photovoltaic (PV) effect in which light falling on a two layer semi-conductor device produces a photovoltage or potential difference between the layers.

The challenges for solar concentrating photovoltaic systems are: to utilise cheap mirrors (or lenses) which can concentrate the sun onto the solar cells; to reliably and accurately track the sun; and to adequately cool the solar cells to maintain a high power output.

The technology of the photovoltaic trough concentrator system uses parabolic mirrors (or troughs) and high efficiency PV cells was developed at the Australian National University.

The Rockingham Photovoltaic Trough Concentrator System

Verve Energy has a photovoltaic (PV) trough concentrator system at Rockingham.

This 20 KW system was connected to the main electricity grid in July 2000.

It has 40 pairs of mirrors (80 in total). Each PV receiver is rated at 250W and is air cooled. There are three inverters which take the DC power and convert it to AC. The AC (grid quality) power is fed into the main electricity grid.

Reliability of the tracking system is of particular interest. The effect of dust on the mirrors is monitored and a suitable cleaning method will be developed and implemented.

Safety

The system disconnects from the main grid if there is a grid outage and automatically re-connects when it is safe to do so. The power from the system goes via underground cabling to the electricity grid.

Technical details

Solar cells

These are made from high quality single crystal silicon. Individual cell efficiencies are around 22% under sunlight concentrated 30 times. The finned aluminium heatsink, bonded to the back of the solar cells, keeps them from overheating. Cell operating temperature will be around 70 degrees Celsius.

Tracking system

A microprocessor positions the troughs pointing towards the sun, even during cloudy weather. The troughs 'roll' from east to west each day and the long central support tilts the troughs to adjust for seasonal variation. This is called 'two-axis' tracking.

the Challenges

The challenges for solar concentrating photovoltaic systems are:

to utilise cheap mirrors (or lenses) which can concentrate the sun onto the solar cells;
to reliably and accurately track the sun; and
to adequately cool the solar cells to maintain a high power output.

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