Part Two: Making Electricity Directly from Sunlight

Growing markets for photovoltaics on Earth brought new companies into the business and with them came fresh ideas for building better modules and improving production procedures. The first ones had only a coat of silicon between the cells and their surroundings. Out in the ocean, seawater and salty air corroded the wired connections between cells. Hot daytime temperatures in the desert softened the silicon, making the material prone to absorb sand whipped into the panels by winds. And the Australians discovered that cockatoos and parrots considered silicon a delicacy and would tear such modules to pieces as they feasted

Early Innovation Growing markets for photovoltaics on Earth brought new companies into the business and with them came fresh ideas for building better modules and improving production procedures. The first ones had only a coat of silicon between the cells and their surroundings. Out in the ocean, seawater and salty air corroded the wired connections between cells. Hot daytime temperatures in the desert softened the silicon, making the material prone to absorb sand whipped into the panels by winds. And the Australians discovered that cockatoos and parrots consider silicon a delicacy and would tear such modules to pieces as they feasted. The early experiences in the field demanded more robust modules. Bill Yerkes, the man who probably did more than anyone to put the terrestrial photovoltaics industry on a solid footing, did away with silicon as the top cover. He replaced it with tempered glass. Its strength, ability to self-clean after a rain and availability influenced Yerkes’ decision. He also streamlined production by screen-printing the contacts onto the cells. The materials and methods introduced by Yerkes in the late 1970s became standard for the entire industry. Cheaper and better solar products have made electricity available to many in rural areas not connected to power lines. Their portability delivers electricity where utilities cannot or will not go. Camels, donkeys, porters or vehicles can bring them in. Solar modules connected to batteries provide better lighting and power electronic devices less expensively, more cleanly and reliably than other alternatives offered to the 1.5 billion people who live beyond the grid. Financing About 2.5 million families in the developing world use solar electricity in the home. The pricing of solar modules presents the chief obstacle to more widespread use. When purchasing solar modules, the customer buys 25 to 30 years of electricity. At least 100 million people could afford solar electric systems if they could spread their payments out over time. To serve this market, companies have sprung up establishing photovoltaic utilities. Customers pay a monthly fee – usually the amount they would otherwise have to spend on lower quality energy sources such as kerosene and batteries – and in return the provider wires the house, installs the modules as well as lights and maintains the system. Providing credit at reasonable rates also helps in bringing photovoltaics to more households in the developing world. Even in wealthy countries few can afford to pay the full price for relatively high-priced items in one payment. How many cars would Detroit sell without financing? In the developing world, there would be virtually no end to customers for solar electric systems with low enough monthly payments. Photovoltaics also ranks as the best way to power pumps for bringing drinking water to villages. Thirst increases with the intensity of sunshine making a perfect fit between need and availability. Cisterns hold solar-pumped water for use during sunless periods. They eliminate the added expense of batteries usually required for solar systems to work at night and during inclement weather. Lacking a power source for water pumping forces many villagers to fetch water from lakes or streams full of water borne diseases. Photovoltaics insures a clean and reliable supply. As with electrical service, the expense of stringing telephone wires above or underground keeps over half of the world’s population without telephone service. As photovoltaics has become the technology of choice for remote communications, solar offers the only way to connect those without phone service to the rest of the world. Because photovoltaics does so much to better the lives of rural people in the poorer parts of the world, The Times of India regards solar energy “as the common man’s friend.” Further Reducing Cost The cost of solar cells remains too high for photovoltaic electricity to compete with electricity from overhead utility lines in wealthy countries. Its continuing decrease in price, though, accounts for photovoltaics’ burgeoning presence in the developed world. Mobile road signs placed to alert motorists about temporary changes in roadway conditions and use now run solely on photovoltaics. Less than ten years ago they relied on generators for their power. The change from fluorescent flood lighting to light-emitting diodes has lowered the power needs so dramatically that a small solar panel can feed enough electricity into accompanying batteries to keep the signage illuminated indefinitely. When running on fossil fuels, mobile road signs required refueling every third day as well as periodic servicing. With photovoltaics they can remain unattended for as long as needed. Not having to pay someone to come out to fuel and service them has saved construction companies and highway departments great sums of money. Solar modules have sprouted in state-of-the-art railroad yards. They run switching equipment. Before, when switching cars to assemble trains, railroad workers had to physically throw a lever to change tracks. Now, from a central tower, a single person can move by remote control the switches for an entire yard with photovoltaics providing the “muscle”. Wherever America’s Navy fleet docks, people can see photovoltaics helping to protect our ships. Since the 2001 attack on the USS Cole, the Navy sets-up protective barriers while in port in the water. Solar powered light emitting diode lanterns demarcate the boundaries of the netting to prevent friendly craft from inadvertently getting tangled up. Those traveling on toll roads have begun using photovoltaics. Resembling an automatic garage door opener in shape and size, a little piece of electronics attached to windshields lets drivers pay tolls yet zip through tollgates without stopping for an attendant or to deposit cash. The device’s microprocessor communicates with the tollbooth deducting fees from prepaid accounts. Adding a strip of photovoltaic material to the device enhances its longevity. Increasingly Competitive Anywhere power lines have to go underground photovoltaics has become the better choice. In such cases, cost effectiveness for photovoltaics comes not from the energy saved but from avoiding the expense of digging up asphalt and concrete. Solar electricity powers the 30,000 emergency call boxes standing along California’s highways. Just in the city of Anaheim, taxpayers have saved US$6 million dollars by powering more than 1000 call boxes with photovoltaics rather than trenching in utility power. Likewise, Carrolton, Texas officials discovered that when considering the installation of flashing lights above speed limit signs near schools the city would cut expenditures in half by choosing solar modules instead of excavating to connect to the nearest source of utility-generated electricity. The same economics applies when considering the placement of new street lights, the installation of illuminated bus shelters, or the addition of electricity in neighborhoods where utilities can only deliver the power by cabling underground. Photovoltaic materials doubling as curtain wall, overhangs, or roofing turns solar cells into a cost- effective supplementary energy option for commercial structures. Building with photovoltaics changes the calculation of the technology’s economics as the application does not compete against the cost of utility power but contends with the price of other building material. Marble or granite, for example, cost more and yet neither can produce one watt of electricity. The availability of solar fuel also matches the electrical needs of buildings since consumption primarily occurs between 9 a.m. and 5 p.m. Demand for electricity soars on summer afternoons when the sun pours down solar fuel. Since architects can configure photovoltaics into building material however they wish, using solar material in building can serve a third use – to block out or let in as much sunlight as wished, helping to contribute to inside lighting while lowering air-conditioning and heating loads and in the process reducing the energy buildings consume. The Final Frontier To compete with the price of electricity delivered in overhead wires throughout America, Europe and Japan, the price of modules and their installation has to drop another 200 to 500 percent, depending on electric tariffs and the amount of solar fuel available. Presently, most photovoltaic material comes from silicon grown as large cylindrically shaped single crystals or cast in sizable blocks in multiple crystal form. Transforming cells only 300 or 400 microns thick from such bulky materials demands lots of sawing. As a result, half of the very expensive silicon starting material ends up on the floor as unusable dust. Less costly and wasteful ways of manufacturing solar cells now coming on-line promise much lower prices. A number of companies, for example, produce cells directly from molten silicon. A laser then simply cuts them to fit into modules. Another manufacturer instantly crystallizes molten silicon to an inexpensive supporting material. Later, a laser slices the strip into usable dimensions. Others have developed processes to spray photovoltaic material onto supporting material. All share compatibility with highly automated assembly line techniques suitable for low-cost, mass production. Some though maintain that the materials used presently, even by streamlining their production, will never reach a price compatible for mass-use in the developed world. These researchers have chosen to work with organic compounds that can absorb light and change it directly into electricity. They envision depositing the compounds on film-like material that would easily adhere to awnings, roofs or windows. Commercialization remains at least a decade away. Solar cells have the advantage of producing the most power when other forms of electricity become scarce and most dear in price – on sunny summer afternoons as everyone’s air conditioners go on. The relatively high price solar electricity can command at such times will open the door to its large-scale debut in the utility market of the developed world as a supplier of electricity during peak periods of demand. Distributed Generation Most, however, do not expect photovoltaics to supply electricity to the developed world in the same way as other fuel sources have. Solar’s modularity lets each building become its own power plant. It therefore does away with having to buy land to site a generating station as well as the large capital outlay to construct the plant and the purchase of switching gear and transformers along with the placement up huge pylons to get the electricity to substations and then send it out to individual buildings and factories via power lines. On site, generated electricity can cost much more than that produced at a distant generating plant and still stay competitive since it contends with the much higher price of delivered electricity. The ability of solar home systems to interact with centralized utilities also furthers the economic attractiveness of photovoltaics to those owning homes and buildings. Using presently available power conditioning equipment, each building can intelligently participate in the electrical market. When the photovoltaic system produces more electricity than needed, it sells the electricity to the utility, helping to pay for the installation. During nighttime or inclement weather, photovoltaic systems buy back utility-generated electricity, removing the specter of doing without electricity when the sun doesn’t shine. In situations where security of supply dominates, photovoltaics combined with another on-site micro-power generator guarantees uninterruptible service. Producing electricity on site also reduces or avoids the necessity to build new transmission and distribution lines or upgrade older ones. Making electricity where people use it also cuts down the electron traffic on already clogged transmission lines, helping to avoid electrical gridlock. On site power production also does away with power losses incurred when centrally generated electricity passes through transmission and distribution lines to the end user. In the most efficient utility systems such losses run at about 33 percent – in the developing world, the percentage of electricity lost between power plant and final destination can reach 65 percent. When people use air-conditioning, sun generated electricity can help avoid brownouts and blackouts. Putting modules up building-by-building reduces turn-around time of construction to generation. Rooftop systems take a week at most to install while years pass before a large power plant goes up. More importantly, a modular technology such as photovoltaics enables scaling to the actual electrical need, bringing greater precision to supplying electricity. The increased use of photovotaics decreases air pollution and greenhouse gas emissions by replacing dirtier ways of making electricity. Energy Security Onsite production of electricity from a secure energy source like the sun reduces our reliance on energy sources vulnerable to terrorism. One hole in a pipeline or a downed transmission pylon can disrupt millions of lives. A faulty panel only affects one user. A plane hitting an atomic reactor could set off a nuclear disaster. If a module breaks, there’s no catastrophic consequences. Sand composes silicon modules and there’s plenty of that material in our country as well as sunlight and neither of these two resources will run out as long as the Earth stays habitable. Photovoltaics also simplifies power production. It dissolves the many steps now necessary for generating electricity which begin with extracting, processing and transporting fuel to run a power plant that then sends the electricity through many miles of wires before doing any useful work. For these reasons Science magazine regards solar cells as “a space-age electronic marvel at once the most sophisticated solar technology and the simplest, most environmentally benign source of electricity yet conceived.” A Sunny Future True, solar electricity at the moment generates less than .01 percent of the world’s power. Keep in mind though when Colonel Drake drilled the first successful oil well in 1859, he had in mind selling the petroleum solely for medicinal purposes. No one ever dreamed that one day oil would reign as “King of Fuels.” Rather, it slowly went on to gain economic clout as it successfully satisfied niche markets as a lubricant and as a lighting fuel. The story of photovoltaics follows the same pattern. Twenty years ago one megawatt of solar cells existed worldwide. Since then, cumulative production has exceeded a gigawatt. By 2003, annual output will equal what took twenty years to achieve. Each niche solar cells fill nourishes further growth. Credit the semiconductor revolution beginning at Bell Laboratories for the ever-increasing use of photovoltaics. The ability of transistors to operate electronic devices on very low power has opened many opportunities for its twin – the solar cell – to operate. Already the world has seen the tandem use of transistors and solar cells in satellites, navigation aids, telecommunications, and televisions, radios, and cassette players in the developed world and a myriad of other electronic devices. It takes no wild leap of imagination to see the same happening in most offices and homes throughout the world. © John Perlin 2002 Used with Permission. About the Author The article is a synopsis of John Perlin’s book, “From Space to Earth: The Story of Solar Electricity,” which describes the step-by-step development of photovoltaics. The Oregon Museum of Science and Industry has agreed to produce a traveling outdoor exhibit based on the book. For more information on the book and/or exhibit, please contact John by email.


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