Summary: Conventional solar PV cell efficiency are in the range 10-22%, and module efficiency in the range 9-20%.
If only we had super high efficient solar cells, the whole world would only be using solar to power everything. So what indeed is the efficiency of solar cells all about, and how efficient indeed are the current solar cells and panels?
More efficient solar panels require less area to generate the same amount of electricity.
Solar panel efficiency is the ratio of the electrical output of a solar panel to the energy incident on it in the form of sunlight. Thus, if 10 kWh equivalent of sunlight is falling on a group of solar panels having an efficiency of 20%, the panel will generate 2 kWh of electricity.
Efficient solar panels require less area to generate the same amount of electricity than less efficient panels.
The amount of sunlight falling on solar panels is directly proportional to the area of the solar panels. Thus, you can easily see that to generate the same amount of electricity, more efficient solar panels will require lesser area than solar panels that are of lower efficiency. Put another way, for the same area, efficient solar panels will generate more electricity than not-so-efficient solar panels.
Crystalline panels more efficient than thin film solar panels
Overall, crystalline solar panels have higher efficiency than thin film panels, though that gap is shortening all the time. The best crystalline panels boast efficiencies of about 21% (cell efficiency 22%) as of 2014. The best thin film panels boast efficiences of about 16% as of 2014.
Monocrystalline panels more efficient than polycrystalline panels
Within crystalline cells, monocrystalline cells have a higher efficiency (upto about 22%) than polycrystalline cells (these have reached up to 18% in 2014).
Solar modules less efficient than the solar cells they contain
For crystalline solar cells, the panel or module efficiency is 1-2% less than the corresponding cell efficiency. Thus, if solar cells produced by Company A has 19% efficiency, their modules will have about 17%-18% efficiency. This reduction is because the module loses some efficiency owing to the presence of a glass layer and encapsulant layer that prevent some portions of sunlight energy from hitting the cells.
Questions from the curious cat
What are the highest cell and panel efficiencies we can expect by 2020?
Predicting the future is more an art than science, so we are not going to pretend we will be accurate.
But let us give a try: We expect crystalline solar cell efficiencies to be in the range 26-27%, and thin film solar cell efficiencies in the range 23-24%.
How does efficiency of panels increase if I use trackers?
Solar trackers allow the panels to be oriented normal (perpendicular) to the sunlight all the time, and as a result the solar panels are able to convert a larger part of the incoming energy into electricity.
Why are some cells more efficient than others, under similar conditions? What really contributes to efficiency?
A number of material parameters affect cell efficiency. Some of the aspects are the optimal use of anti-reflecting coatings, the way shunt and series resistance are used, and the quality of n-type and p-type layers.
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