The manufacturing and power industry
The manufacturing of photovoltaic cells is diverse in the photovoltaic power industry. Many participants have developed their own proprietary manufacturing processes to construct their own proprietary technology. Several technologies of manufacturing photovoltaic systems exist in the industry. These technologies arguably represent the past and future of the photovoltaic manufacturing industry. Methods used in the industry include: 1. Monocrystalline and multicrystalline production, 2. String Ribbon Technology, 3. Copper Indium Gallium Selenide (CIGS), and 4. Thin-film Technology.
The ability of a company to utilize the most cost effective manufacturing method will lead to a competitive advantage. Being the low cost manufacturer is essential to success in the photovoltaic manufacturing industry. Regardless of the technology used in the manufacturing process, there exist uniform manufacturing steps for all companies within the industry. These steps include silicon crystal growing or casting plants, photovoltaic cell manufacturing, module assembly, and systems assembly. Silicon crystal growing or casting plants refers to producing the silicon for photovoltaics.
This involves converting sand into silicon bricks and finally into wafers. Photovoltaic plant assemblies take the finished silicon wafers through a high technology semiconductor process to create working photovoltaic cells. Module Assembly refers to combining the silicon wafers into a laminated photovoltaic module. The final step, Systems Assembly, refers to the mechanical and electrical component of the finished product. Although some companies have vertically integrated all steps, typically, companies specialize in one or two steps.
This analysis is focused on companies involved in the second and third steps of the manufacturing process. The most important material for making photovoltaic cells is silicon. Although there are other photovoltaic technologies that rely on other semiconductors, like amorphous silicon, cadmium telluride, copper indium diselenide, and organic cells, silicon remains the dominant raw material used within the industry. Crystalline silicon technology is the earliest form of manufacturing and continues to be the dominant technique in the market, representing approximately 94% of solar market sales in 2005 (Fast Solar Energy Facts).
Conventional crystalline silicon technology involves sawing thin wafers from solid crystalline silicon blocks. Crystalline silicon products are known for their reliability, performance and longevity. However, factors such as high waste from wafer cutting, complex processing procedures, high energy requirements, and high initial capital expenditures have limited the ability of these manufacturers to decrease costs and maximize outputs. Monocrystalline production requires taking a seed of single-crystal silicon and placing it in contact with the top surface of molten silicon.
Atoms of the molten silicon solidify in the pattern of the seed and extend the single-crystal structure. The final product is a thin monocrystalline wafer (How BP Makes Solar). The complementary silicon production technique is multicrystalline production. This is a casting method where pieces of silicon are melted in large ceramic crucibles to form an ingot, or brick of silicon. Each ingot is cut into smaller bricks, which are cut into wafers. The wafers go through a series of chemical coatings and metallization processes to complete the assembly.
Ultimately, both methods produce silicon wafers that are consolidated to form a photovoltaic cell (How BP Makes Solar). Companies using these techniques include BP Solar, Kyocera, Solar Power Industries, GE, Sanyo, Sharp, Shell Solar, and SunPower. Another manufacturing technique in the industry is String Ribbon technology developed by Evergreen Solar. Conventional silicon techniques such as monocrystalline and multicrystalline manufacturing are based on energy intensive processes used to melt the silicon into ingots and then cut the ingots into silicon wafers.
String Ribbon technology uses surface tension to form silicon wafers. The making of a string ribbon wafer is like making a soap bubble. Instead of a ring forming the bubble, this technology uses two parallel wires to form a thin-film of silicon. With this proprietary technique, two heat-resistant wires are pulled vertically through a silicon melt, and the molten silicon ps and solidifies between the strings (String Ribbon). This technique creates a thin silicon wafer and minimizes the typically energy intensive process.
A fourth manufacturing technology is Copper Indium Gallium Selenide (CIGS). This technology represents a competitive advantage for the main developer of this technique, HelioVolt. Copper Indium Gallium Selenide (CIGS) is the best solar-absorbing material (Thin Film). With high yields from their substrate, HelioVolt is able to claim higher watts per cost when manufacturing this technique. In addition, this technique allows solar film to be applied to many different materials, such as glass, steel, metal, composites and some polymers.
This places them in a good position for the emerging building integrated photovoltaic (BIPV) products market, where photovoltaic cells are incorporated into building materials. The final method for photovoltaic cell manufacturing is thin-film technology. While most major photovoltaic power manufacturers currently rely on crystalline silicon technology for their photovoltaic cell production, thin-film technology allows for decreased costs due to less consumption of raw materials.
Thin-film technology involves depositing several thin layers of silicon on a substrate to make a photovoltaic cell. Although thin-film techniques generally use materials more efficiently than traditional crystalline manufacturing techniques, the high capital costs, low manufacturing yields, lower conversion efficiency, and reduced product performance and reliability have hindered the adoption of this technology. Despite these obstacles, thin-film technology manufacturing represents a potential method for the production of photovoltaic cells in the photovoltaic manufacturing industry.
Companies in the industry using this technology include Energy Conversion Devices (ECD), EPVSolar, and PowerFilm Technologies. Despite these manufacturing technique differences, general trends in the industry have emerged to facilitate manufacturing. The ability to produce photovoltaic cells cheaply is integral to success in this industry. The strategies used in the industry include cost reductions enabled by increased line efficiencies, vertical integration, improved economies of scale, and expansion of manufacturing capacity to low-cost manufacturing locations.
Companies use lean manufacturing and other continuous improvement strategies to streamline their manufacturing. Because this is an emerging industry, plants are engineered with state-of-the-art technology to increase efficiencies and eliminate waste. This forward thinking strategy is aligned with the technology and industry mission. Vertical integration is accomplished by producing wafers, cells and panels in one location. These silicon products can be sold individually or integrated into a finished photovoltaic module or customized system.
Although some industry members purchase silicon ingots from outside manufacturers, the optimum situation is to perform all the necessary steps of producing photovoltaic cells at one location and within one company. Economies of scale and low-cost manufacturing are achieved through reproducing identical plants throughout the world in order to meet the rising demand. Participants in the industry have assembled plants around the world, not only to be in close proximity to demand, but also to seek competitive edge through low-cost manufacturing.