Photovoltaics: How we do it – and why SolarWorld. And EveryDay is a SunDay www.solarworld-usa.com RETURNNING TO THE SUN “Environmental ills and climate ENERGY CRISIS LIFE’S POWER PLANT change pose glo- Over the past two centuries, humans learned Perpetually renewing power from the sun has to harness fossil fuels on a vast scale to power fueled life on Earth since its first spark. bal crises for our an industrial revolution. This quantum advance From cellular to mammalian in machine automation, mass production and planet. Any answer forms, the sun has supplied a labor division drove unparalleled improvements critical ingredient in the recipe to these problems in the health, economics and comforts of citi- for living beings. More practi- zens of industrialized nations. must be powerful. cally, humans have relied on Fortunately, we But today, the solar power – to warm water, dry benefits come at clothes and prepare food – as far need only tap the great, unpaid as history’s record reaches. environmental The sun emits so much energy that solar power source of costs. Fossil fuels experts compete to put the output in terms cannot continue to be life’s history for an- we can grasp. Here’s just one: Earth receives humanity’s primary enough solar radiation in an hour to supply the swers: the sun and source of energy. planet’s electrical needs for a year. its ample energy.” It’s time for an energy foundation in harmony with the planet. It’s time for a solar revolution. Frank H. Asbeck SolarWorld chairman and CEO PV POINTER Of the 92 elements, silicon (Si) is the Earth’s most prevalent semiconductor – and second most common element of any kind, after oxygen. Appearing in silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper LIFE’S POWER PLANT GATHERING THE SUN’S BOUNTY and opal, silicon makes up about a quarter, by weight, of Now people are re-tapping their roots in a solar world by using panels of the Earth’s crust. Photovoltaic photovoltaic (PV) cells to generate power from the sun’s rays. manufacturing starts with As reliable as the sun itself, the technology is simple and clean. Cells are built polysilicon, a refinement of silicon materials. on wafers of silicon made from ordinary sand and quartz. Assembled into modules and exposed to the sun, the cells directly convert light into electricity – without polluting emissions, resource depletion or moving parts. SolarWorld, extraordinary because it undertakes all phases of PV manufac- WORD TO KNOW turing and makes no other products, builds modules in four steps, starting with sand and ending with sun. Photon: A photon is neither Turn the page to begin the story behind SolarWorld’s core mission to put the a wave nor a particle, but technology to work for homes and businesses around the world. instead a packet of light energy. Solar radiation arrives on the surface of photo- voltaic cells in the form of photons, providing the main energy that activates cells to produce electricity. ROOTS OF A RENEWABLE The history of 1954 Bell Labs announces 1960 Hoffman Electronics invention of the first modern creates a 14%-efficient solar cell. the solar industry silicon solar cells, with energy- conversion efficiency of about 6 1961 United Nations stages and SolarWorld “Solar Energy in the Developing 1973 Solar cells power percent. Skylab, the first U.S. space are intermixed, World” conference. 1955 Western Electric licences station. each with one commercial solar cell 1962 The Telstar communica- technologies. tions satellite is powered by 1974 A home in New foot squarely solar cells. Mexico is the world’s positioned in the 1957 AT&T employees Gerald first to be powered L. Pearson, Daryl M. Chapin and 1963 Viable photovoltaic only by solar and United States Calvin S. Fuller receive patent module is produced out of wind energy. silicon solar cells. and the other in US2780765, “Solar Energy Converting Apparatus.” 1977 Engineer and entre- Germany – the 1964 Yale preneur Bill Yerkes sells two markets that 1958 Hoffman University startup Solar Technology Electronics- Press publishes International to Atlantic have led the in- Semiconductor Division Farrington Richfield Co., forming ARCO Solar. dustry’s develop- creates 9%-efficient Daniels’ landmark solar cells. book, “Direct Use of the Sun’s 1979 In Camarillo, Calif., ment. In the U.S., Vanguard 1, the first Energy.” ARCO Solar dedicates world’s SolarWorld began solar-powered satellite, largest PV factory to making is launched with .1 watt as ARCO Solar. silicon crystal ingots, wafers, solar panel. photovoltaic cells and Siemens and Shell 1967 Soyuz 1 becomes first modules. manned spacecraft using solar. then owned the World annual PV unit before Solar- array production World bought it. MWp 1950s 1960s 1970s 10,000 PV POINTER Pioneering relativity theorist Albert Einstein won the Nobel Prize in 1921 – but not for his ROOTS OF A RENEWABLE renowned relativity equa- tion E=mc2. The prize actually 1990 Siemens acquires celebrated his 1905 discovery ARCO Solar, forming of exactly how light caused 1,000 what was then called the Siemens Solar. photoelectric effect – essen- tially, photovoltaics. Today, SolarWorld issues its annual 2002 Royal Dutch Einstein Awards to honor PV 1996 Siemens Solar cele- Shell acquires Siemens researchers. brates 100 MW of installed Solar, creating Shell Solar. power from modules made in Camarillo. 2006 SolarWorld aquires Shell Solar. 100 1980 ARCO Solar becomes 2007 Investors begin first company to produce offering free installation more than 1 megawatt in return for long-term of PV modules in 1997 Siemens becomes first power purchase agree- one year. company to offer 25-year ments (PPAs), which be- warranty. come common financing arrangements. 1998 Solar- 1982 ARCO Solar commissions world’s World forms as ORD TO NOW startup business, 2008 Solar- W K first 1 MW grid-con- World opens 10 nected PV installation. entering Germa- ny’s burgeoning 480,000- solar market. square-foot Photovoltaic. The word 1985 Australia’s University plant in photovoltaic comes from the of New South Wales creates 1999 Germany Hillsboro, words photo, meaning light, silicon cells with 20% ef- investing $500 million and volt, meaning electricity. requires utilities to pay “feed-in In short, the term PV means ficiency in laboratory. tariffs” at fixed premium rates to establish 500 MW of electricity from light. to owners of solar systems for annual capacity and power contributed into grid. 1,000 employees there. 0 1980s 1990s 2000s CONJURING CRYSTAL FROM ROCK SolarWorld heats and melts poly- CHARGING MELTING silicon rock until The magic starts with about 250 pounds of As the crystal-growing furnace heats up to tem- polysilicon rocks carefully stacked in a quartz peratures ranging around 2,500 degrees Fahren- it forms a white- crucible. The only other ingredient is a silicon heit, its silicon contents melt into a shimmering hot liquid, then disk impregnated with a tiny amount of slurry. Once computerized monitors register the boron. The addition of the boron dopant en- right temperature and atmospheric conditions, re-fuses the mol- sures that the resulting crystal will bear a posi- the alchemy begins. A silicon seed crystal, ten silicon into tive potential electrical orientation. The cruci- hung from a narrow ble is encased within thick walls of insulating cable attached to a a single giant graphite and rotary device crystal in which locked inside atop the a cylindrical furnace, is slowly all atoms are per- furnace. lowered into fectly aligned in a the melt. Polysilicon desired structure Polysilicon rock and orientation. with boron- Seed impregnated silicon disk Quartz crucible Steel furnace encasement enveloping graphite insulation PV POINTER The method that SolarWorld uses in the United States to grow silicon crystal is known CONJURING CRYSTAL FROM ROCK as “Cz” (pronounced cee-zEE). Cz is an abbreviation for the Czochrolski process, named after Polish scientist Jan Czochrolski, who discovered ROWING OOLING the method in 1916 as he re- G C searched crystallization rates The crucible starts to Flash forward about 21/2 of metals. turn, and the seed crystal days since the crucible was begins to rotate in the op- charged with polysilicon: posite direction. The silicon After hours of cooling to melt freezes onto the about 300 degrees Fahr- seed crystal, matching the enheit, the furnace hood seed’s crystalline structure. and shaft lift away from The crystal grows, the the crucible encasement, cable and seed slowly as- slowly swing to one side cend, and the crystal elon- and reveal a completed gates at a controlled cylindrical crystal, ready to width. As the growth move to the second step depletes the silicon and next production room. slurry, the crucible WORD TO KNOW also rises. Crystal measuring Crystal emerging 8 inches wide and 1 A crystal is a solid about 5 /2 feet long Crystal: from melt with molecular building blocks, such as atoms or ions, that have arranged themselves in an identically repeating pattern along all three spatial dimensions. CUTTING WAFERS INTO CELLS A silicon crystal must change CUTTING SQUARING shape several First, a saw cuts off the crystal’s so-called top Mounted ingots are placed standing on end in a and tail, so that a crystal of uniform width rack bearing 16 at a time inside another wire- times before it remains. Typically, wafering saws draw thin wire slicing machine. There, wire running in a lattice winds up as the bearing a liquid abrasive across the crystal’s configuration descends on the ingots to shear surface. (Below, a machine mounted with a gi- off four rounded segments, leaving flat sides. precisely calibrat- ant donutlike steel blade does the cutting.) Wire The result: The ingots now have a square cross- ed wafers that saws also cut the crystal into ingots measuring section, except for still-rounded corners.