From Silicon to Photovoltaic Cells
The most common type of photovoltaic cell is made of crystalline silicon. The process used to make the cells requires skills as diverse as chemical engineering and microelectronics expertise.
There are several key steps in producing cells from raw silicon:
- The first is silicon purification, a chemical process. Metallurgical-grade silicon is converted to trichlorosilane gas, which contains silicon. The gas is reacted at high temperature to produce solar-grade silicon that is deposited on a pure silicon seed rod.
- Crystallization is also a chemical process. In this step, molten silicon is turned into a solid with a crystalline structure. The high-temperature molten silicon is grown into monocrystalline ingots that solidify as they cool. These cube-shaped blocks are metallic in appearance.
- Ingot slicing involves precision mechanics. Ingots are sawed into parallelepipeds, then into thin, 0.2-millimeter wafers.
- Isotropic etching of the wafer surface limits reflection and energy losses, increasing efficiency.
- A physicochemical treatment for wafers called doping turns the silicon into a semiconductor. The thermal diffusion of phosphorus and boron creates a p-n junction, allowing electrical current to flow.
- Wafer metallization involves microelectronics expertise. An electrical circuit is printed onto the wafers to capture the electrical current induced by the photoelectric effect.
SunPower Cells, Market-Leading Efficiency
SunPower cells capture more sunlight than other cells in the market because they are made of high quality monocrystalline silicon and because all contacts are located on the back. A copper base also makes them extremely resistant to cracking and exposure to the elements. As a result, our affiliate can guarantee energy production that exceeds industry standards by 9.1%.
From Photovoltaic Cells to Modules
Photovoltaic cells, produced earlier on in the process, are connected to one another to create modules. Manufacture is fully automated to reduce the risk of breakage. Production is located in France, Southeast Asia, Poland and Mexico.
The process takes place in four main steps:
- Connection: the cells are welded into "strings."
- Packaging: the system is encased to seal it from the elements.
- Finishing and assembly: the module is prepared for electrical hookup.
- Checking and testing: the module's performance is tested.
Quality Assurance, Thoroughness and Attention to Detail
Every aspect of quality control, from raw material selection through operating tests, exceeds industry standards. The quality assurance process ensures long-term system efficiency. That is why SunPower modules are fully warranted for 25 years. Total's affiliate is the only supplier to offer this type of integrated service.
A Proactive Recycling Process
Total has planned ahead for component recycling by joining PV Cycle, a European association tasked with developing recycling technologies. The materials used — glass, aluminum, copper, etc. — are easy to recycle and SunPower modules contain no lead or cadmium.
Photovoltaic System Design and Installation from A to Z
There is more to photovoltaics than just making cells and modules. We and our affiliates have over 30 years of experience developing systems. Tenesol, now merged with SunPower, brought its off-grid expertise, while SunPower shared its skills in the area of power plants generating more than 600 megawatts (MW) in United states.
Photovoltaic panels are designed to be incorporated into more complex arrays, or photovoltaic systems, to produce the power the customer needs, whether on-grid or off.
Building systems that are just right for each installation site requires cutting-edge skills and capabilities:
- Technical and financial design: Design engineering is the starting point of every project. It is a vital and complex step that determines whether a project makes sense, by comparing a site's potential with the customer's request.
- On-site installation of systems: Panel installation and connection must be adapted to the project's specific requirements.
- Solar system operation and maintenance: Systems require ongoing monitoring, to ensure that they are continuing to produce power efficiently.