The term photovoltaics derives from the Greek word ‘phos’ meaning light and the word ‘volt’, unit for electrical voltage named by Alessandro Volta. Photovoltaics is a science, which examines light-electricity conversion, respectively, photon energy-electric current conversion. In other words it stands for light-current conversion. The light to current conversion takes place within solar cells, which can be thin-film, polycrystalline or monocrystalline, according to their structure. In most cases they are made of silicon. Solar-module consists of many solar cells, which are electrically connected and placed between glass and tedlar plate, and framed by an (usualy) aluminium frame. A number of solar-modules and other components (batteries, charge regulators, inverters…) can form large photovoltaic systems.
In photovoltaic (solar) module light energy converts into electricity. A photovoltaic module is the basic element of each photovoltaic system. It consists of many jointly connected solar cells. According to the solar cell technology we distinguish monocrystalline, polycrystalline and thin-film modules. Most commercial crystalline modules consist of 36, of 60 or of 72 cells. Solar cells are connected and placed between a tedlar plate on the bottom and a tempered glass on the top. Placed between the solar cells and the glass there is a thin usually EVA foil. Solar cells are interconnected with thin contacts on the upper side of the semiconductor material, which can be seen as a metal net on the solar cells. The net must be as thin as possible allowing a disturbance free incidence photon stream. Usually a module is framed with an aluminium frame, occasionally with a stainless steel or with a plastic frame. Special flexible modules are designed for use on boats that can be walked upon without causing any damage to the modules. The typical crystalline modules power ranges from several W to up to 300 W/module. Some producers produce preassembled panels with several 100 Wp. Over its estimated life a photovoltaic module will produce much more electricity than used in its production and a 100 W module will prevent the emission of over two tones of CO2.
Commercial crystalline photovoltaic modules efficiency typically ranges from 12 to 17%. However, you must be aware, that the solar cell efficiency doesn’t equal the module efficiency. The module efficiency is usually 1 to 3 % lower than the solar cell efficiency due to glass reflection, frame shadowing, higher temperatures etc. Thin-film modules have the lowest price, yet their lifetime is shorter and their efficiency is up to 12 % only.
Monocrystalline Solar Panels
Monocrystalline photovoltaic electric solar energy panels have been the go-to choice for many years. They are among the oldest, most efficient and most dependable ways to produce electricity from the sun.
Each module is made from a single silicon crystal, and is more efficient, though more expensive, than the newer and cheaper polycrystalline and thin-film PV panel technologies. You can typically recognize them by their colour which is typically black or iridescent blue.
Efficiency of commercial monocrystalline solar panels reaches up to 22.5%. According to various researchers, it is not theoretically possible to convert more than 29 percent of the light into energy using crystalline solar cells. Realistically, the limit for a PV panel is likely closer to 24 to 25 percent because of factors like heat.
Polycrystalline Solar Panels
Polycrystalline solar panels are the most common because they are often the least expensive. They are the middle choice in the marketplace … almost as good as single cell silicon panels but generally with a better efficiency than thin film solar panels.
Polycrystalline cells can be recognized by a visible grain, a “metal flake effect”. The solar cells are generally square in shape, and may have a surface that looks somewhat like a mosaic. That’s because of all the different crystals that make up the module.
Efficiency of commercial polycrystalline solar panels goes up to 19.3%. In general polycrystalline panels have an efficiency that is about 70% to 80% of a comparable monocrystalline solar panel.
Thin-film Solar Panels
The term “Thin film solar panels” refers to the fact that these types of solar panels use a much thinner level of photovoltaic material then mono-crystalline or polycrystalline solar panels.The primary objective of manufacturers of these solar panels is to reduce the overall price per watt. While these thin-film modules are much lower in price, they also have lower module efficiency up to 12%.