Big solar versus distributed solar has become a major issue in the environmental community—large solar plants require grading and other disturbances to the ecology of the area while rooftop solar presents none of these problems.
Steven Strong, a pioneering solar architect and longtime advocate of distributed solar, described the added expense incurred in putting up a field of photovoltaic modules for large-scale electrical generation: “You’ve got to buy land,” he pointed out, dig lots of holes, pour lots of concrete, dig trenches, bury conduits, build foundations and support structures, buy a large inverter to change the photovoltaic-generated DC current into AC, construct a building in which the inverter is placed, construct a building in which the inverter is placed, [and] purchase switch gear and a switchyard and transformer. And because your station is usually far away from where people live, you have to spend money on transmission lines to get the electricity where the need is.” In contrast, none of the outlay in time, money, or effort is necessary if the solar modules are placed where the electricity will be used.
In the mid-1970s and early 1980s, when the governments of developed countries began to fund solar-energy programs, they tended to favor large-scale, centralized photovoltaic plants over small, autonomous, individual rooftop units. After all, that was how electricity had been produced with other power sources. “The vision was huge solar farms—gigawatts of solar cells,” a participant in the design of these large-scale photovoltaic installations attested.
The American Association for the Advancement of Science took issue with the megaplant approach. “Despite the diffuse nature of the [solar] resource, the research program has emphasized large central stations to produce solar electricity in some distant future,” the scientific organization complained in a 1978 article in its magazine Science, “and has ignored small solar devices for producing on-site power—an approach one critic describes as ‘creating solar technologies in the image of nuclear power.’”
On-site photovoltaic- generated electricity also makes renewable energy economically more attractive than power generated by a large solar electric plant, because it “competes at the retail level rather than at the wholesale level” with other producers of electricity.
The government took that approach, according to America's most prestigious science body, because of “twin assumptions that traditional” methods of producing power “should determine the shape of new energy systems and that ‘big is better.’” Solar cells, in contrast, owing to their modular nature, can be placed on-site where the electricity is needed, and tailored to meet the exact needs of the consumer.
As early as the 1870s, solar pioneer John Ericsson (already famous for inventing the Civil War ironclad ship USS Monitor) articulated this special aspect of solar power by observing that the sun's energy falling on the roofs of houses of Philadelphia could operate “more than 5,000 steam engines each of 20 horsepower,” leading him to conclude that “one precious virtue of this new energy source is that it can be gathered without occupying useful space.”
Photovoltaic pioneer Charles Fritts came to a similar conclusion, that photovoltaic systems are better suited for point-of-service placement. When Fritts boldly predicted in 1885 that his selenium solar panels might soon compete with Thomas Edison’s coal-fired power plants, he had no intention of constructing large-scale generating stations. Rather, he said, solar arrays were “intended principally for what is known as ‘isolated’ working, i.e., for each building to have its own plant.” (One hundred and twenty-eight years later, a different kind of energy concern, the Shell Oil Company, came to the same conclusion: “In our opinion, the dispersed generation of [photovoltaic] energy—in shopping centers, small manufacturing plants, homes, and apartment complexes—affords the earliest opportunity for photovoltaics to contribute to our [America’s] growing energy needs.”)
A century later the debate over how to situate photovoltaics intensified when, at the end of 1982, a California utility built, with government funding, a megawatt photovoltaic plant. That led engineer Markus Real to demonstrate that dispersed photovoltaic units on already-built structures could be an alternative to centralized photovoltaic stations. He formed Alpha Real, a small company that installed photovoltaic systems. The company became well-known in Real’s native Switzerland after it won the world’s first solar-car race, staged in Europe in June 1985. Almost every Swiss had seen the "Mercedes Benz powered by Alpha Real" devastate the competition.
Capitalizing on its name recognition at home, Alpha Real continued making milestones in photovoltaic applications. For example, the company built the world’s first photovoltaic-powered tunnel-lighting system high in the Alps.
As Real and his company gained experience, they made an important discovery about the centralization of solar power production. In a traditional power plant, each incremental enlargement of its turbo generator results in a threefold increase in power. Therefore, size is a major factor in the cost of generating electricity, and it encourages the building of bigger power plants, which centralizes power production for a large area.
The same rule, however, does not apply to electricity generated by solar cells. The price of energy produced by photovoltaics decreases only as the cost of the production drops, which happens as the number of modules manufactured rises.
To prove to skeptics the value of placing photovoltaic units on rooftops instead of installing them in large, faraway generating plants, Alpha Real initiated its revolutionary Project Megawatt. Real called the program “the answer to [the] large multi-megawatt installations” that had gained favor throughout the world. Alpha Real advertised over Switzerland’s airwaves and through the nation’s newspapers in 1987 for “333 power-station owners.... Having a rooftop exposed to the sun is the only prerequisite.” People responded enthusiastically. Soon three kilowatts of photovoltaics went up on each of the 333 rooftops for a total of one megawatt of dispersed power. A special electronic device called an inverter changed the direct current from the panels to the alternating current used on power lines.
The device used by Alpha Real allowed ratepayers and a utility company to interact in the production of electricity: not only did the electricity derived from the sun power the houses, but when people had more than they could use they sent it to a utility company through the power lines and received payment for it. At night or during bad weather, when the panels did not generate sufficient power, the homeowners bought electricity from the utility. Electrical generation became a two-way street.
Alpha Real’s 333 installations constituted at that time the largest demonstration of photovoltaic systems on buildings. People saw the logic: rooftops in Switzerland had the slope optimal for solar-energy harvesting, and these power plants were located right next to the buildings’ electrical connections.
Project Megawatt also helped to revolutionize the buying and selling of electricity between mini-producers and utilities. When participants in Project Megawatt produced more electricity than they needed, they sold it to the local utility for an amount equivalent to two cents per kilowatt-hour. But when they needed electricity—for example, at night—the local utility charged them six times as much. Real attributed the imbalance to a flaw in the utility company’s thinking: “The idea that electricity doesn’t flow solely from the central power station to the consumer, but had become a two-way street with each consumer also becoming a producer, was, of course, something new for utilities to chew on.”
None of the outlay in time, money, or effort is necessary if the solar modules are placed on the buildings where the electricity will be used. “It makes sense, absolute sense,” argued Real. “The roof is there. The roof is free. The electrical connections are there.”
Donald Osborn, formerly director of alternative-energy programs at the Sacramento Municipal Utility District in California, outlined other advantages of on-site photovoltaic electrical generation, for both the consumer and the utilities. “You reduce the electricity lost through long-distance transmission,” which runs about 30 percent on the best-maintained lines. Structures with their own photovoltaic plants decrease the flow of electricity through distribution lines at substation transformers, “thereby extending the transformers’ lives. And for a summer-daytime-peaking utility,” Osborn added, “you can offset the load on these systems when the demand for electricity would be greatest,” helping to eliminate “brownouts in the summer and early fall.” On-site photovoltaic-generated electricity also makes renewable energy economically more attractive than power generated by a large solar electric plant, because it “competes at the retail level rather than at the wholesale level” with other producers of electricity.
The dreams of 19th-century solar pioneers John Ericsson and Charles Fritts—of solar panels covering the rooftops of the world—seem to be becoming a reality with their price dramatically dropping, producing electricity from the sun cheaper than centralized power plants in many parts of America and the rest of the world. As a consequence, “residential solar has tremendous potential for growth and will become a preferred energy choice for mainstream consumers,” according to Lori Neuman, spokesperson for the large independent utility, NRG. Its CEO, David Crane, foresees the time when customers will not “need the power industry at all,” a scenario he said “is ultimately where big parts of the country [will] go.”
Realizing these forecasts will be a major victory for the consumer and the nation. It will enhance national security in light of the increased threat of terrorism. “It wouldn’t take that much to take the bulk of the power system down,” according to the chairman of the U.S. Federal Energy Regulatory Commission, Jon Wellinghoff. “If you took down the transformers and substations so they’re out permanently, we could be out for a long, long time. ... A more distributed system [such as rooftop solar] is much more resilient. Millions of distributed generators can’t be taken down at once.” Even the utilities themselves recognize what’s ahead. A report by the Edison Electric Institute, the association of investor-owned utilities, flatly recognized the threat rooftop photovoltaics presents to the current utility model, stating, “One prominent example is in the area of distributed solar PV, where threats to the centralized utility business have accelerated.”
As solar becomes dominant, the role of utilities will inevitably change. “The electricity network company could essentially be an insurance company against not having sunshine when you need power,” said Laszlo Varro, an economist for the International Energy Agency. Or they can enter the photovoltaic rooftop business themselves, as Southern California Edison has, helping to lead the transition from centralized to distributed generation of electricity in much the same way as large telecommunication companies have evolved from being owners of landlines to also being purveyors of cellular services.
From the book Let It Shine. Copyright © 2013 by John Perlin. Reprinted with permission from New World Library.