APPENDIX F
PHOTOVOLTAICS ( SILICON SOLAR CELLS & PANELS)
Solar cells are solid-state semiconductor devices which convert light energy directly into
electrical energy. Their construction is basically similar to transistors and other solid state
devices, in that they are predominantly silicon doped with small quantities of different
material to create the semi-conductor effect.
There are several different types of cells, amorphous, mono-crystalline and poly-
crystalline.
Let us consider a polycrystalline cell (a very common type) the base material is silicon
doped with boron to give it positive or p-type characteristics , a thin layer on the front of
the cell is doped with phosphorous to give it negative or n-type characteristics. We have
now created an n-p junction where these two layers join. When photons (light) hit the cell
and are absorbed in the junction region, their energy (if sufficient) will free electrons in
the silicon crystal giving them sufficient energy to break free of the electric field at the
junction and travel through the silicon crystal to be conducted away by wires connected
to the silicon so they can then perform useful work as electricity.
A solar cell is a low voltage device typically about 0.45 Volts per cell , cells are
connected in series to increase voltage.
Similarly if larger currents are required more surface area is required in the cell, this may
be a larger cell or smaller cells in parallel
As with most solid state devices output will vary with temperature.
Typical variations are in the order of
-80 mV per deg C on open circuit volts.
+0.065% per deg C on short circuit current
-0.5% per deg C on power
POWER TESTING OF SOLAR PANELS
You need to know the maximum power output of your Solar Panel in order to prepare
any ballast required before the race day.
Your Panel may have the maximum power it can produce on it’s label otherwise testing
the power output will be required. In Victoria the official panel testing during
scrutineering is performed on a calibrated light box using a micro processor based power
measuring meter. (NOTE: this power measuring meter was designed and constructed by
Mr Tony Bazouni specifically for power measuring of solar panels, these meters are in
limited production see Buying guide for contact details for Mr. Bazouni.)
ENGELEC has a similar meter, again in limited production. Refer to buying guide for
contact details.