What are solar panels made of?

 

Read a 2018 update to this story here. 

This description was contributed by REC Group

A crystalline silicon solar panel, or module, is a series of interconnected silicon cells joined together to form a circuit. In greater numbers the amount of power produced by these interconnected cells can be increased and used as an electricity production system.

Solar panels come in different sizes for different purposes. The current standard offering in the market is a 60-cell panel, with larger 72-cell panels being used for larger-scale installations. Smaller panels are also available and used in the off-grid market, where space is at a premium or for layouts where more flexibility is required.

Cell Production Techniques
At cell structure level, different kinds of panels exist, such as monosilicon, polysilicon or thin-film. Monosilicon cells are manufactured from a single crystal. Their higher production costs leads to them being more expensive than other types. Monosilicon cells often have a higher efficiency rating than other technologies. However, as they are cut from cylindrical ingots, they do not completely cover a panel without substantial waste, lessening the efficiency of the overall panel.

Poly-silicon cells are made from melting different silicon crystals together. These are less expensive to produce than monocrystalline, but less efficient. Recent times have seen much more investment in polysilicon technology and the best polysilicon panels now demonstrate a performance equal to or close to mono. This, coupled with the lower costs, has led polysilicon to emerge as the premier material for solar panels.

Thin film solar cells are created through a co-evaporation process of chemicals on a glass sheet. They have lower conversion efficiencies than silicon, but reduce the amount of material required in creating the cell.

Improvements In Cell Efficiency
In the current challenging market situation, substantial reductions in production costs are necessary to increase the attractiveness of solar and make it more affordable.

In the climate of oversupply and continuously falling prices, manufacturers are focusing on reducing production costs, while increasing performance. Among the major areas of focus for new developments are improved wafer crystallization, selective emitter technology, back surface passivation and metal-wrap through technology.

Panel performance is not only impacted by new technology but also by changes to assembly techniques, materials of construction and quality of the components. A standard panel consists of a glass layer on the front, with an insulating layer and a protective backsheet on the rear of the panel. This helps keep the manufacturing cost of a panel down and allows a better dissipation of heat from the panel. Some panels use a glass layer on the front and on the back. This increases panel strength and adds further protection from damage and humidity ingress to the cells but compromises the cell efficiency as heat is not dissipated so easily, in turn affecting panel output.

An aluminum frame usually surrounds a panel. This adds strength to the structure, allowing it to withstand more load and protects the edges of the glass from knocks and breakages as well as from humidity ingress. The use of a frame has the further advantage of allowing the mounting of the panel in a variety of ways, for example with mounting clamps, bolts or a slide-in system.

Outlook
Despite the current uncertainty in the industry caused by oversupply of panels, the future still looks bright for PV. Demand for renewable energy is growing, and potential applications of solar energy are expanding. At the same time, improvements in cell efficiency, assembly techniques and materials of construction are making solar power competitive.

Read a 2018 update to this story here.