A diode is almost always put in series at some point in the electrical output from a solar panel, or solar energy system, such as before any battery storage. The diode will only allow the current to flow in one direction. This is good for battery energy storage systems being charged up by a solar panel, so as to prevent current from going from the battery to back through the solar panel, wasting energy and draining your charged up battery, during night time or cloudy conditions. The diode needs to have a large enough current rating of higher than the current output of your solar panel, and a high enough “reverse applied voltage” rating, typically greater than that of the battery system. The diode is therefore often called a “power diode” since it can withstand high currents greater than 1 amp. There is a power loss in a diode. It does contain some internal resistance due to the semiconductor (usually silicon) metal in it, and due to it’s action. There will typically be a 0.7 voltage drop or loss due to it, and if you multiply that by the current you will have the total power loss due to the diode.
Pwatts =voltage x current = VI = 0.7v x Iamps
Ex. For a 2A system, P=0.7(2.0)=1.4 Watts
Hence, more reason to increase the available voltage and power of a solar cell from the theoretical/ideal 12v system to have an 18v voltage source/solar panel which takes into account some losses that will take place in the entire solar energy system.
On average, for a 2A solar panel, you can expect about 1W of power loss due to the diode. With some special low loss diodes called Schottky diodes, there may be lower losses, but it oddly depends on the current going through the diode. For example at 100ma or 0.1A of current, there will be 0.2V voltage drop-loss, which is ideal for small solar panels, etc, but that loss value will change/increase as current increases, and that diode won’t be much different than a standard diode at about 1A of current. or so.
Post time: Jan-18-2017