Your daily dose of photovoltaic technology developments and solar news

Owing to the huge demand for photovoltaic products, the market is still very attractive for investments in production facilities. Nevertheless, the increasing number of competing photovoltaic manufacturers and the decrease in governmental subsidies require substantial and continuous cost reductions.

The PV industry has seen some incredible growth in the last five to eight years. This growth is essential in order to fulfill the challenging targets this industry has set itself to ensure it becomes an economical viable alternative energy source. A negative result of this growth, however, is the inefficient supply chain, where there is a lack of balance between demand and supply. The industry is going from one bottleneck to another.

This review is based on primary research of global solar cell and thin-film manufacturing companies that are currently manufacturing, expanding manufacturing, building facilities for manufacturing or progressing towards establishment of manufacturing facilities. The study looks at historical, present and future name-plate capacities for the global continental regions and also for specific countries with large existing capacity or rapid capacity growth and is based on approximately 600 companies and manufacturing facilities throughout the world.

Materials innovation in solar photovoltaic manufacturing has long played a key role in efforts to raise cell and module conversion efficiencies, improve overall device performance and reliability, and lower the overall cost per manufactured watt. Research and development in areas such as ultrathin-silicon wafering and replacement films for thin-film PV transparent conductive oxides often garner much of the industry’s attention.

Glass plays an increasingly important role in photovoltaics. The rising demand for solar modules is pushing the glass industry to the fore. As a result, mechanical engineering companies around the world are working to meet the demands of the solar industry, with the tremendous potential of glass, especially in the thin-film sector, at the epicentre of this effort.

Invented in their high efficiency version in the early 1990s, dye-sensitised solar cells (DSCs) entered the global market in 2007 with the first commercial modules based on this versatile, hybrid (organic-inorganic) technology. The 6-7% efficiency of the first modules is a result of their good performance in diffuse light conditions, allowing for the production of electricity both under cloudy conditions and indoors.

Formation of the pn-junction for charge carrier separation is one of the key processes of a modern high-volume solar cell production. In silicon wafer-based solar cell technology this is achieved by diffusion of phosphorus atoms in boron pre-doped wafers forming a sub-micron shallow n-type emitter in a 200μm-thick p-type base.

Crystalline silicon solar cell fabrication involves many wet chemical process steps. Like most processes in solar cell manufacturing, many of these wet chemical processes were transferred from the semiconductor industry. In contrast to microchip fabrication with maximum throughputs of 100 wafers/hour, state-of-the-art solar cell equipment relies on several 1,000 wafers/hour. Furthermore, specific processes have been developed for the texturisation of the wafer surface. Therefore, there is a need for dedicated methods of characterization of these wet chemical processes.

In any solar cell process, the metallization step is critical as it often sets conditions and limitations for the other process steps. The main metallization technique used today in Si solar cell production is screen-printing of metallic pastes; namely, Ag pastes for the front side, Al pastes for most of the rear side, and Ag or Ag-Al pastes for the solder pads at the rear. While these techniques are clearly robust and convenient, they have limitations. Therefore, alternatives are being investigated. A technique that is presently finding its way into production is two-step metallization with Ag plating. Another more radical approach is to avoid printing altogether, instead using some kind of ablation followed by plating.

Transparent conducting oxides (TCOs) are a special class of materials that can simultaneously be both optically transparent and electrically conducting and, as such, are a critical component in most thin-film photovoltaics. TCOs are generally based on a limited class of metal oxide semiconductors such In₂O₃, ZnO and SnO₂, which are transparent due to their large band gap energy and can also tolerate very high electronic doping concentrations to yield conductivities of 1000S/cm or higher.

In recent years, a new generation of solar electric products has emerged from the lab into the global market: thin-film technologies that employ approximately 1% of the active, expensive photovoltaic material used by standard crystalline-silicon cells. Through a combination of cost advantages and new product applications, cadmium telluride (CdTe), amorphous silicon, and copper-indium-gallium-selenide (CIGS) thin-film PV have the potential to foster a paradigm shift toward distributed electricity generation at cost parity with other forms of energy.

Laser-based tools have become increasingly visible within R&D labs, pilot production lines, and as the preferred technology used by many turnkey suppliers. As equipment types however, relatively little is known about the differences in the laser-based tools used for solar applications within each of the c-Si and thin-film segments.

The rapid expansion of high volume manufacturing to meet growing demand in recent years has highlighted the development of increasingly higher throughput machines. This is particularly true in the critical bottleneck process of module assembly, specifically characterised by tabbing and stringing steps. Significant productivity improvements have come about with the development of integrated, highly-automated tabbers and stringers from a range of equipment vendors. However, module assembly remains the most expensive step in conventional c-Si cell production.

Photovoltaic modules and components, due to the nature of their employment, must be designed to withstand the most diverse of environments. The large spectrum of climatic conditions and mechanical stresses that these components must weather merit the application of some standards by which they can be tested for durability, reliability and safety. TÜV Rheinland operates several ISO 17025-accredited laboratories worldwide for type approval testing of flat plate as well as concentrating PV modules, PV components and solar thermal systems.

Solar enterprises will each be faced with the occasional surplus or lack of solar modules in their lifetimes. In these instances, it is useful to adjust these stock levels at short notice, thus creating a spot market.

 The past year was characterised by the realisation of many MW-range solar power plants as well as the highest ever market growth related to large-scale photovoltaic systems. These systems were constructed in several regions, some of which saw significant increases in cumulative installed power. In the European Union, progress was observed among countries such as Italy, Czech Republic and France; the German market, however, decreased slightly.

Power generation is a rapidly changing process. Owing to evolutions in power electronics, sustainable electricity generation and consumption came to the fore and now it is nearly impossible for photovoltaics to operate without this technology. This holds true for efficient consumption such as plug-in electric and hybrid vehicles or compact efficient lighting. Power electronics need to be taken into account in relation to grids, for example in novel voltage-source HVDC connections. Photovoltaic energy conversion requires power electronics in order to adapt the floating DC-output to a fixed DC-level and typically further to a grid-compatible AC electricity. These converter (mainly inverter) technologies have evolved considerably over the past few years, in much the same way as has PV cell technology, but in a much less apparent fashion.

The U.S. residential solar market is poised for growth. For solar companies seeking to capitalize on the growth potential of this market, the keys to success will be sales volume and operating efficiency. Solar employee purchase programs (solar EPPs), which have been initiated by companies as diverse as SunPower, REC Solar, and SolarCity, represent a new and potentially important channel for increasing sales and improving sales efficiency. Driving these programs are increasing corporate sustainability initiatives and growth in voluntary employee benefit offerings, especially employee purchase programs and green benefits.

In the few years since the PV cell and module manufacturing industry first hit the radar, the identities of the winners and losers in the race to supply equipment have started to emerge. While some companies can genuinely claim to have been involved in the solar industry for some time, the majority are relatively new on the scene. This is hardly surprising, as the explosive growth in demand spurred any company with matching competences into action.

The American Recovery and Reinvestment Act has now been passed, and there is much talk about what this will actually mean for the solar industry. The final version of the stimulus bill amounts to US$789, which will be the government’s most expansive economic rescue package since The Great Depression, even after the cuts.

News of credit crunch woes filtering down the lines over the past few months has instilled a sense of frugality in all industry sectors. While the credit crisis has indeed affected the PV industry, German banks, investors and creditors have claimed that the financing of small PV systems in the private sector seems not to be endangered.