Basics Modules
How Solar Cells Work
Sunlight is composed of many tiny particles called photons. When a photons strikes certain types of atoms, electrons are set free from the atomic bonds. A solar cell is made of two types of material, N-type and P-type. The boundary between the two types is called the junction. The two types of materials set up a strong electrostatic field which moves the electrons across the junction to the N-type. The electrons are then collected by the metal on the front surface of the cell, travel out the wires, through the load, and back to the P-type side of the cell through the metal on the rear of the cell.
Solar Modules
Solar modules have one or more solar cells, usually 36 cells or more. The cells are usually laminated to a sheet of glass to make an environmentally protected package. The modules usually have an aluminum frame around them to protect the glass and provide a place to mount them. The glass is usually tempered to make it strong and safe. If it breaks, it will break in tiny harmless pieces rather than long knife-like shrouds. The back is protected with a special sheet of plastic which keeps out moisture, air, and is abrasion resistant. You cannot take a module apart without ruining it.
Read more about solar modules
Concentrator Modules
Concentrator modules use optics to concentrate the sunlight onto the solar cells. The optics can be mirrors or lenses. The solar cells produce current in proportion to the amount of light, up to the limit of the cell physics. So a 10 to 1 concentration would theoretically produce ten times the amount of current. Optical and other losses reduce the effective concentration ratio. Also, concentrators mostly use only the sunlight coming directly from the sun (direct radiation), which is only about 80% of the total. The heat is also concentrated which raises the issue of thermal management.
Read more about concentrators
IV Curves
IV curves are plots of the current versus voltage for solar cells, solar modules, solar panels, or solar arrays. The IV curve can tell a lot about how the system is operating. Where the voltage is zero, the current is called short circuit current (Isc). This is the current you get if you short the wires together. Where the current is zero, the voltage is called open circuit voltage (Voc). This is the voltage when the wires are not connected to any load. Between these two points is the maximum power point (Pmp). The current and voltage at the maximum power point are called the peak power current (Ipp) and the peak power voltage (Vpp).