A Certain Technical Maturity
Despite solar power's dismal commercial failures, some proponents continued to believe that if they could only find the right combination of solar technologies, the vision of a free and unlimited power source would come true. Frank Shuman was one who shared that dream. But unlike most dreamers, Shuman did not have his head in the clouds. In fact, his hardheaded approach to business and his persistent search for practical solar power led him and his colleagues to construct the largest and most cost-effective machine prior to the space age.
Shuman's first effort in 1906 was similar to Willsie's flat-plate collector design except that it employed ether as a working fluid instead of sulfur dioxide. The machine performed poorly, however, because even at respectable pressures, the steam--or more accurately, the vapor--exerted comparatively little force to drive a motor because of its low specific gravity.
Shuman knew he needed more heat to produce steam, but felt that using complicated reflectors and tracking devices would be too costly and prone to mechanical failure. He decided that rather than trying to generate more heat, the answer was to better conserve the heat already being absorbed.
In 1910, to improve the collector's insulation properties, Shuman enclosed the absorption plates not with a single sheet of glass but with dual panes separated by a one-inch air space. He also replaced the boiler pipes with a thin, flat metal container similar to Tellier's original greenhouse design. The apparatus could now consistently boil water rather than ether. Unfortunately, however, the pressure was still insufficient to drive industrial-size steam engines, which were designed to operate under pressures produced by hotter-burning coal or wood.
After determining that the cost of building a larger absorber would be prohibitive, Shuman reluctantly conceded that the additional heat would have to be provided through some form of concentration. He thus devised a low-cost reflector stringing together two rows of ordinary mirrors to double the amount of radiation intercepted. And in 1911, after forming the Sun Power Co., he constructed the largest solar conversion system ever built. In fact, the new plant, located near his home in Talcony, Penn., intercepted more than 10,000 square feet of solar radiation. The new arrangement increased the amount of steam produced, but still did not provide the pressure he expected.
Not easily defeated, Shuman figured that if he couldn't raise the pressure of the steam to run a conventional steam engine, he would have to redesign the engine to operate at lower pressures. So he teamed up with E.P. Haines, an engineer who suggested that more precise milling, closer tolerances in the moving components, and lighter-weight materials would do the trick. Haines was right. When the reworked engine was connected to the solar collectors, it developed 33 horsepower and drove a water pump that gushed 3,000 gallons per minute onto the Talcony soil.
Shuman calculated that the Talcony plant cost $200 per horsepower compared with the $80 of a conventionally operated coal system--a respectable figure, he pointed out, considering that the additional investment would be recouped in a few years because the fuel was free. Moreover, the fact that this figure was not initially competitive with coal or oil-fired engines in the industrial Northeast did not concern him because, like the French entrepreneurs before him, he was planning to ship the machine to the vast sunburnt regions in North Africa.
To buy property and move the machine there, new investors were solicited from England and the Sun Power Co. Ltd. was created. But with the additional financial support came stipulations. Shuman was required to let British physicist C. V. Boys review the workings of the machine and suggest possible improvements. In fact, the physicist recommended a radical change. Instead of flat mirrors reflecting the sun onto a flat-plate configuration, Boys thought that a parabolic trough focusing on a glass-encased tube would perform much better. Shuman's technical consultant A.S.E. Ackermann agreed, but added that to be effective, the trough would need to track the sun continuously. Shuman felt that his conception of a simple system was rapidly disintegrating.
Fortunately, when the machine was completed just outside of Cairo, Egypt, in 1912, Shuman's fears that the increased complexity would render the device impractical proved unfounded. The Cairo plant outperformed the Talcony model by a large margin--the machine produced 33 percent more steam and generated more than 55 horsepower--which more than offset the higher costs. Sun Power Co.'s solar pumping station offered an excellent value of $150 per horsepower, significantly reducing the payback period for solar-driven irrigation in the region. It looked as if solar mechanical power had finally developed the technical sophistication it needed to compete with coal and oil.
Unfortunately, the beginning was also the end. Two months after the final Cairo trials, Archduke Ferdinand was assassinated in the Balkans, igniting the Great War. The fighting quickly spread to Europe's colonial holdings, and the upper regions of Africa were soon engulfed. Shuman's solar irrigation plant was destroyed, the engineers associated with the project returned to their respective countries to perform war-related tasks, and Frank Shuman died before the armistice was signed.
Whether or not Shuman's device would have initiated the commercial success that solar power desperately needed, we will never know. However, the Sun Power Co. can boast a certain technical maturity by effectively synthesizing the ideas of its predecessors from the previous 50 years. The company used an absorber (though in linear form) of Tellier and Willsie, a reflector similar to Ericsson's, simple tracking mechanisms first used by Mouchout and later employed by Eneas, and combined them to operate an engine specially designed to run with solar-generated steam. In effect, Shuman and his colleagues set the standard for many of the most popular modern solar systems 50 to 60 years before the fact.
The Most Rational Source
The aforementioned solar pioneers were only the most notable inventors involved in the development of solar thermal power from 1860 to 1914. Many others contributed to the more than 50 patents and the scores of books and articles on the subject. With all this sophistication, why couldn't solar mechanical technology blossom into a viable industry? Why did the discipline take a 50-year dive before again gaining a measure of popular interest and technical attention?
First, despite the rapid advances in solar mechanical technology, the industry's future was rendered problematic by a revolution in the use and transport of fossil fuels. Oil and coal companies had established a massive infrastructure, stable markets, and ample supplies. Also, besides trying to perfect the technology, solar pioneers had the difficult task of convincing skeptics to see solar energy as something more than a curiosity. Visionary rhetoric without readily tangible results was not well received by a population accustomed to immediate gratification. Improving and adapting existing power technology, deemed less risky and more controlled, seemed to make far more sense.
Finally, the ability to implement radically new hardware requires either massive commitment or the failure of existing technology to get the job done. Solar mechanical power production in the late nineteenth and early twentieth centuries did not meet either criterion. Despite warnings from noted scientists and engineers, alternatives to what seemed like an inexhaustible fuel supply did not fit into the U.S. agenda. Unfortunately, in many ways, these antiquated sentiments remain with us today. During the 1970s, while the OPEC nations exercised their economic power and as the environmental and "no-nuke" movements gained momentum, Americans plotted an industrial coup whose slogans were energy efficiency and renewable resources. Consequently, mechanical solar power--along with its space-age, electricity-producing sibling photovoltaics, as well as other renewable sources such as wind power--underwent a revival. And during the next two decades, solar engineers tried myriad techniques to satisfy society's need for power.
They discovered that dish-shaped reflectors akin to Mouchout's and Eneas's designs were the most efficient but also the most expensive and difficult to maintain. Low-temperature, nonconcentrating systems like Willsie's and Tellier's, though simple and less sensitive to climatic conditions, were among the least powerful and therefore suited only to small, specific tasks. Stationary reflectors like those used in Adams's device, now called Power Tower systems, offered a better solution but were still pricey and damage prone.
By the mid-1980s, contemporary solar engineers, like their industrial-revolution counterparts Ericsson and Shuman, determined that for sunny areas, tracking parabolic troughs were the best compromise because they exhibited superior cost-to-power ratios in most locations. Such efforts led engineers at the Los Angeles-based Luz Co. to construct an 80-megawatt electric power plant using parabolic trough collectors to drive steam-powered turbines. The company had already used similar designs to build nine other solar electric generation facilities, providing a total of 275 megawatts of power. In the process, Luz engineers steadily lowered the initial costs by optimizing construction techniques and taking advantage of economies of buying material in bulk to build ever-larger plants until the price dropped from 24 to 12 cents per kilowatt hour. The next, even larger plant--a 300-megawatt facility--scheduled for completion last year, promised to provide 6 to 7 cents per kilowatt hour, near the price of electricity produced by coal, oil, or nuclear technology.
Once again, as with Shuman and his team, the gap was closing. But once again these facilities would not be built. Luz, producer of more than 95 percent of the world's solar-based electricity, filed for bankruptcy in 1991. According to Newton Becker, Luz's chairman of the board, and other investors, the demise of the already meager tax credits, declining fossil fuel prices, and the bleak prospects for future assistance from both federal and state governments drove investors to withdraw from the project. As Becker concluded, "The failure of the world's largest solar electric company was not due to technological or business judgment failures but rather to failures of government regulatory bodies to recognize the economic and environmental benefits of solar thermal generating plants."
Other solar projects met with similar financial failure. For example, two plants that employed the tower power concept, Edison's 10-megawatt plant in Daggett, Calif., and a 30-megawatt facility built in Jordan performed well despite operating on a much smaller scale and without Luz's advantages of heavy initial capital investment and a lengthy trial-and-error process to improve efficiency. Still they were assessed as too costly to compete in the intense conventional fuel market.
Although some of our brightest engineers have produced some exemplary solar power designs during the past 25 years, their work reflects a disjointed solar energy policy. Had the findings of the early solar pioneers and the evolution of their machinery been more closely scrutinized, perhaps by Department of Energy officials or some other oversight committee, contemporary efforts might have focused on building a new infrastructure when social and political attitudes were more receptive to solar technology. Rather than rediscovering the technical merits of the various systems, we might have been better served by reviewing history, selecting a relatively small number of promising systems, and combining them with contemporary materials and construction techniques. Reinventing the wheel when only the direction of the cart seems suspect is certainly not the best way to reach one's destination.
While the best period to make our energy transition may have passed and though our energy future appears stable, the problems that initiated the energy crisis of the 1970s have not disappeared. Indeed, the instability of OPEC and the recent success in the Gulf War merely created an artificial sense of security about petroleum supplies. While we should continue to develop clean, efficient petroleum and coal technology while our present supplies are plentiful, this approach should not dominate our efforts. Alternative, renewable energy technologies must eventually be implemented in tandem with their fossil-fuel counterparts. Not doing so would simply provide an excuse for maintaining the status quo and beg for economic disruption when reserves run low or political instability again erupts in oil-rich regions.
Toward that end, we must change the prevailing attitude that solar power is an infant field born out of the oil shocks and the environmental movement of the past 25 years. Such misconceptions lead many to assert that before solar power can become a viable alternative, the industry must first pay its dues with a fair share of technological evolution.
Solar technology already boasts a century of R&D, requires no toxic fuel and relatively little maintenance, is inexhaustible, and, with adequate financial support, is capable of becoming directly competitive with conventional technologies in many locations. These attributes make solar energy one of the most promising sources for many current and future energy needs. As Frank Shuman declared more than 80 years ago, it is "the most rational source of power."
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