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About Photovoltaics

The subject of Photovoltaics (PV) is also commonly referred to as "solar power" or "solar electric," but for simplicity's sake, we will refer to solar power as PV in this article.

Solar Module Basics

A solar panel or module is compromised of PV cells arranged in different series and/or parallel configurations to provide different voltage and current outputs. These cells form modules, commonly referred to as panels. The modules are typically rigid, but thin-film modules can be incorporated into flexible designs. The front of the module uses glass or another composite to protect the precious cells from the elements. The back of the module can be plastic, wood, metal, glass or composite. The frame can be composed of metal, plastic, composite, wood and there are even some frameless designs. PV modules can be arranged together to form PV arrays. These arrays are usually mounted to rooftops, ground mount systems, the tops of poles, orbiting satellites, or anywhere else they can receive precious photons.

 

Types of PV

 

Monocrystalline solar cell module

Mono-Crystalline is the granddaddy of solar cell technology, and has been making usable electricity since the 1950s with ever increasing efficiency and production. In 1958 the NASA Vanguard satellite (Luque and Hegedus 3) was launched into orbit with a monocrystalline backup PV array. The use of photovoltaics on satellites would push crystalline and all other PV technology forward. To this day, monocrystalline solar panels still boast the highest efficiency in the mainstream PV market.

polycrystalline solar cell

Polycrystalline solar modules were an important advance in PV science. Instead of relying on larger, harder to manufacture slices of solid silicon crystals, polycrystalline uses small flakes of PV silicon. The resulting cells are cheaper to manufacture though slightly less efficient (polycrystalline does, however, have better power output in partial shade than monocrystalline). An easy way to identify polycrystalline cells or modules is to look for cells with randomized, multiple shimmering flakes.

Amorphous thin film solar module

Thin Film and Amorphous cell technology came along in the late 1970s and had many people in the solar field quite excited. It promised and delivered much lower production costs, lower energy input to produce, the possibility of much larger cells, and an ability to work in more varied light conditions such as low light. But there is an important catch; the thin film panels are much less efficient than crystalline, meaning that the panels need to be larger to achieve the same Watt output. Therefore if space is an issue, thin film panels are not ideal. The technology typically utilizes amorphous silicon as the photovoltaic layer, although other types do exist. Flexible thin film is one of the newest PV marvels, and these flexible modules can be installed in a variety of places, built into roofs, or even laminated onto cars or planes. The flexible thin film is available commercially in many forms, but it is still an infant technology, prices are high and efficiencies are ever improving. Look for thin film technology to gain much more market share in the next 5-10 years.

 

Works Cited

Antonio Luque (Editor), Steven Hegedus. June 2003. Handbook of Photovoltaic Science and Engineering