The heart of a solar electric system is the solar panel itself. The PV market is expanding rapidly, and manufacturers are constantly introducing new and emerging technologies. The end result of all these technologies is the same: You place the solar panels in the sun, and they produce power. The more powerful the sun’s energy, the more power you get, although solar panels continue to generate small amounts of electricity in the shade.
Most solar panels are made up of individual solar cells connected together. A typical solar cell will only produce around 0.55 volt, so by connecting them together in series inside the panel, a more useful voltage is achieved.
Most small solar panels – rated 200Wp or below – are rated as 12-volt solar panels, while larger solar panels usually have higher voltages. A 12-volt solar panel produces around 14-18 volts when put under load. This allows a single solar panel to charge up a 12-volt battery. Incidentally, if you connect a voltmeter up to a solar panel when it is not under load, you may well see voltage readings of up to 26 volts. This is normal in an ‘open circuit’ on a solar panel. As soon as you connect the solar panel into a circuit, this voltage level will drop to around 14-18 volts.
Solar panels can be linked together to create a solar array. Connecting multiple PV panels together allows you to produce a higher current or to run at a higher voltage:
Connecting solar photovoltaic panels in series makes an array run at higher voltages. Typically, 12, 24, or 48 volts in a stand-alone solar system (off-grid PV system), several hundred volts in a grid-tie solar system (on-grid PV system).
Connecting the panels in parallel allows a solar array to produce more power while maintaining the same voltage as the individual panels. When you connect multiple PV panels together, the power of the overall system increases, irrespective of whether they are connected in series or in parallel.
In a solar array where the solar panels are connected in series, you add the voltages of each panel together and add the wattage of each panel together to calculate the maximum amount of power and voltage the solar array will generate.
In a solar array where the photovoltaic panels are connected in parallel, you take the average voltage of all the solar panels and you add the wattage of each panel to calculate the maximum amount of power the solar array will generate.
Checking out Crystalline Solar Panels
Crystalline PV panels, which are made by grouping a number of individual solar cells together, are currently the most common panel type for residential and commercial applications. One of the main reasons why crystalline panels are used so frequently is that they’re more efficient than other PV technologies.
The Monocrystalline Kind
Monocrystalline PV panels are typically more efficient than their multi-crystalline counterparts on the cell level because the molecular structure of the ingot is uniform from top to bottom. This characteristic allows the photons to move the greatest number of electrons when in sunlight because the cells are all lined up and facing the exact same direction. In a multi-crystalline cell, the crystals have various shapes and point in different directions, slightly reducing efficiency.
The Multicrystalline Kind
The efficiency of multi-crystalline PV modules is reduced due to the many crystal structures in the cubes. When the photons strike the cells, they have a more difficult time knocking the electrons free, thanks to the many different surfaces present. On the plus side, the cells can be made into squares or rectangles very easily, a fact that allows the multi-crystalline modules to have their cells packed one next to the other with very little space between them. The end result is that multi-crystalline modules have power ratings per unit area that are similar to that of their monocrystalline counterparts even though they’re less efficient on the cell level.