History of Solar Energy (Part 2)

During the height of Mouchout's experimentation, William Adams, the deputy registrar for the English Crown in Bombay, India, wrote an award-winning book entitled Solar Heat: A Substitute for Fuel in Tropical Countries. Adams noted that he was intrigued with Mouchout's solar steam engine after reading an account of the Tours demonstration, but that the invention was impractical, since "it would be impossible to construct [a dish-shaped reflector] of much greater dimensions" to generate more than Mouchout's one-half horsepower. The problem, he felt, was that the polished metal reflector would tarnish too easily, and would be too costly to build and too unwieldy to efficiently track the sun.

Fortunately for the infant solar discipline, the English registrar did not spend all his time finding faults in the French inventor's efforts, but offered some creative solutions. For example, Adams was convinced that a reflector of flat silvered mirrors arranged in a semicircle would be cheaper to construct and easier to maintain. His plan was to build a large rack of many small mirrors and adjust each one to reflect sunlight in a specific direction. To track the sun's movement, the entire rack could be rolled around a semicircular track, projecting the concentrated radiation onto a stationary boiler. The rack could be attended by a laborer and would have to be moved only "three or four times during the day," Adams noted, or more frequently to improve performance.

Confident of his innovative arrangement, Adams began construction in late 1878. By gradually adding 17-by-10-inch flat mirrors and measuring the rising temperatures, he calculated that to generate the 1,200û F necessary to produce steam pressures high enough to operate conventional engines, the reflector would require 72 mirrors. To demonstrate the power of the concentrated radiation, Adams placed a piece of wood in the focus of the mirrored panes where, he noted, "it ignited immediately." He then arranged the collectors around a boiler, retaining Mouchout's enclosed cauldron configuration, and connected it to a 2.5-horsepower steam engine that operated during daylight hours "for a fortnight in the compound of [his] bungalow."

Eager to display his invention, Adams notified newspapers and invited his important friends--including the Army's commander in chief, a colonel from the Royal Engineers, the secretary of public works, various justices, and principal mill owners--to a demonstration. Adams wrote that all were impressed, even the local engineers who, while doubtful that solar power could compete directly with coal and wood, thought it could be a practical supplemental energy source.

Adams's experimentation ended soon after the demonstration, though, perhaps because he had achieved his goal of proving the feasibility of his basic design, but more likely because, as some say, he lacked sufficient entrepreneurial drive. Even so, his legacy of producing a powerful and versatile way to harness and convert solar heat survives. Engineers today know this design as the Power Tower concept, which is one of the best configurations for large scale, centralized solar plants. In fact, most of the modern tower-type solar plants follow Adams's basic configuration: flat or slightly curved mirrors that remain stationary or travel on a semicircular track and either reflect light upward to a boiler in a receiver tower or downward to a boiler at ground level, thereby generating steam to drive an accompanying heat engine.

Even with Mouchout's abandonment and the apparent disenchantment of England's sole participant, Europe continued to advance the practical application of solar heat, as the torch returned to France and engineer Charles Tellier. Considered by many the father of refrigeration, Tellier actually began his work in refrigeration as a result of his solar experimentation, which led to the design of the first nonconcentrating, or non-reflecting, solar motor.

In 1885, Tellier installed a solar collector on his roof similar to the flat-plate collectors placed atop many homes today for heating domestic water. The collector was composed of ten plates, each consisting of two iron sheets riveted together to form a watertight seal, and connected by tubes to form a single unit. Instead of filling the plates with water to produce steam, Tellier chose ammonia as a working fluid because of its significantly lower boiling point. After solar exposure, the containers emitted enough pressurized ammonia gas to power a water pump he had placed in his well at the rate of some 300 gallons per hour during daylight. Tellier considered his solar water pump practical for anyone with a south-facing roof. He also thought that simply adding plates, thereby increasing the size of the system, would make industrial applications possible.

By 1889 Tellier had increased the efficiency of the collectors by enclosing the top with glass and insulating the bottom. He published the results in The Elevation of Water with the Solar Atmosphere, which included details on his intentions to use the sun to manufacture ice. Like his countryman Mouchout, Tellier envisioned that the large expanses of the African plains could become industrially and agriculturally productive through the implementation of solar power.

In The Peaceful Conquest of West Africa, Tellier argued that a consistent and readily available supply of energy would be required to power the machinery of industry before the French holdings in Africa could be properly developed. He also pointed out that even though the price of coal had fallen since Mouchout's experiments, fuel continued to be a significant expense in French operations in Africa. He therefore concluded that the construction costs of his low-temperature, non-concentrating solar motor were low enough to justify its implementation. He also noted that his machine was far less costly than Mouchout's device, with its dish-shaped reflector and complicated tracking mechanism.

Yet despite this potential, Tellier evidently decided to pursue his refrigeration interests instead, and do so without the aid of solar heat. Most likely the profits from conventionally operated refrigerators proved irresistible. Also, much of the demand for the new cooling technology now stemmed from the desire to transport beef to Europe from North and South America. The rolling motion of the ships combined with space limitations precluded the use of solar power altogether. And as Tellier redirected his focus, France saw the last major development of solar mechanical power on her soil until well into the twentieth century. Most experimentation in the fledgling discipline crossed the Atlantic to that new bastion of mechanical ingenuity, the United States.

Though Swedish by birth, John Ericsson was one of the most influential and controversial U.S. engineers of the nineteenth century. While he spent his most productive years designing machines of war--his most celebrated accomplishment was the Civil War battleship the Monitor--he dedicated the last 20 years of his life largely to more peaceful pursuits such as solar power. This work was inspired by a fear shared by virtually all of his fellow solar inventors that coal supplies would someday end. In 1868 he wrote, "A couple of thousand years dropped in the ocean of time will completely exhaust the coal fields of Europe, unless, in the meantime, the heat of the sun be employed."

Thus by 1870 Ericsson had developed what he claimed to be the first solar-powered steam engine, dismissing Mouchout's machine as "a mere toy." In truth, Ericsson's first designs greatly resembled Mouchout's devices, employing a conical, dish-shaped reflector that concentrated solar radiation onto a boiler and a tracking mechanism that kept the reflector directed toward the sun.

Though unjustified in claiming his design original, Ericsson soon did invent a novel method for collecting solar rays--the parabolic trough. Unlike a true parabola, which focuses solar radiation onto a single, relatively small area, or focal point, like a satellite television dish, a parabolic trough is more akin to an oil drum cut in half lengthwise that focuses solar rays in a line across the open side of the reflector. This type of reflector offered many advantages over its circular (dish-shaped) counterparts: it was comparatively simple, less expensive to construct, and, unlike a circular reflector, had only to track the sun in a single direction (up and down, if lying horizontal, or east to west if standing on end), thus eliminating the need for complex tracking machinery. The downside was that the device's temperatures and efficiencies were not as high as with a dish-shaped reflector, since the configuration spread radiation over a wider area--a line rather than a point. Still, when Ericsson constructed a single linear boiler (essentially a pipe), placed it in the focus of the trough, positioned the new arrangement toward the sun, and connected it to a conventional steam engine, he claimed the machine ran successfully, though he declined to provide power ratings.

The new collection system became popular with later experimenters and eventually became a standard for modern plants. In fact, the largest solar systems in the last decade have opted for Ericsson's parabolic troughreflector because it strikes a good engineering compromise between efficiency and ease of operation.

For the next decade, Ericsson continued to refine his invention, trying lighter materials for the reflector and simplifying its construction. By 1888, he was so confident of his design's practical performance that he planned to mass-produce and supply the apparatus to the "owners of the sunburnt lands on the Pacific coast" for agricultural irrigation.

Unfortunately for the struggling discipline, Ericsson died the following year. And because he was a suspicious and, some said, paranoid man who kept his designs to himself until he filed patent applications, the detailed plans for his improved sun motor died with him. Nevertheless, the search for a practical solar motor was not abandoned. In fact, the experimentation and development of large-scale solar technology was just beginning.

Boston resident Aubrey Eneas began his solar motor experimentation in 1892, formed the first solar power company (The Solar Motor Co.) in 1900, and continued his work until 1905. One of his first efforts resulted in a reflector much like Ericsson's early parabolic trough. But Eneas found that it could not attain sufficiently high temperatures, and, unable to unlock his predecessor's secrets, decided to scrap the concept altogether and return to Mouchout's truncated-cone reflector. Unfortunately, while Mouchout's approach resulted in higher temperatures, Eneas was still dissatisfied with the machine's performance. His solution was to make the bottom of the reflector's truncated cone-shaped dish larger by designing its sides to be more upright to focus radiation onto a boiler that was 50 percent larger.

Finally satisfied with the results, he decided to advertise his design by exhibiting it in sunny Pasadena, Calif., at Edwin Cawston's ostrich farm, a popular tourist attraction. The monstrous machine did not fail to attract attention. Its reflector, which spanned 33 feet in diameter, contained 1,788 individual mirrors. And its boiler, which was about 13 feet in length and a foot wide, held 100 gallons of water. After exposure to the sun, Eneas's device boiled the water and transferred steam through a flexible pipe to an engine that pumped 1,400 gallons of water per minute from a well onto the arid California landscape.

Not everyone grasped the concept. In fact, one man thought the solar machine had something to do with the incubation of ostrich eggs. But Eneas's marketing savvy eventually paid off. Despite the occasional misconceptions, thousands who visited the farm left convinced that the sun machine would soon be a fixture in the sunny Southwest. Moreover, many regional newspapers and popular-science journals sent reporters to the farm to cover the spectacle. To Frank Millard, a reporter for the brand new magazine World's Work, the potential of solar motors placed in quantity across the land inspired futuristic visions of a region "where oranges may be growing, lemons yellowing, and grapes purpling, under the glare of the sun which, while it ripens the fruits it will also water and nourish them." He also predicted that the potential for this novel machine was not limited to irrigation: "If the sun motor will pump water, it will also grind grain and saw lumber and run electric cars."

The future, like the machine itself, looked bright and shiny. In 1903 Eneas, ready to market his solar motor, moved his Boston-based company to Los Angeles, closer to potential customers. By early the following year he had sold his first complete system for $2,160 to Dr. A. J. Chandler of Mesa, Ariz. Unfortunately, after less than a week, the rigging supporting the heavy boiler weakened during a windstorm and collapsed, sending it tumbling into the reflector and damaging the machine beyond repair.

But Eneas, accustomed to setbacks, decided to push onward and constructed another solar pump near Tempe, Ariz. Seven long months later, in the fall of 1904, John May, a rancher in Wilcox, Ariz., bought another machine for $2,500. Unfortunately, shortly afterward, it was destroyed by a hailstorm. This second weather-related incident all but proved that the massive parabolic reflector was too susceptible to the turbulent climactic conditions of the desert southwest. And unable to survive on such measly sales, the company soon folded.

Though the machine did not become a fixture as Eneas had hoped, the inventor contributed a great deal of scientific and technical data about solar heat conversion and initiated more than his share of public exposure. Despite his business failure, the lure of limitless fuel was strong, and while Eneas and the Solar Motor Company were suspending their operations, another solar pioneer was just beginning his.

Henry E. Willsie began his solar motor construction a year before Eneas's company folded. In his opinion, the lessons of Mouchout, Adams, Ericsson, and Eneas proved the cost inefficiency of high-temperature, concentrating machines. He was convinced that a nonreflective, lower-temperature collection system similar to Tellier's invention was the best method for directly utilizing solar heat. The inventor also felt that a solar motor would never be practical unless it could operate around the clock. Thus thermal storage, a practice that lent itself to low-temperature operation, was the focus of his experimentation.

To store the sun's energy, Willsie built large flat-plate collectors that heated hundreds of gallons of water, which he kept warm all night in a huge insulated basin. He then submerged a series of tubes, or vaporizing pipes, inside the basin to serve as boilers. When the acting medium--Willsie preferred sulfur dioxide to Tellier's ammonia--passed through the pipes, it transformed into a high-pressure vapor, which passed to the engine, operated it, and exhausted into a condensing tube, where it cooled, returned to a liquid state, and was reused.

In 1904, confident that his design would produce continuous power, he built two plants, a 6-horsepower facility in St. Louis, Mo., and a 15-horsepower operation in Needles, Calif. And after several power trials, Willsie decided to test the storage capacity of the larger system. After darkness had fallen, he opened a valve that "allowed the solar-heated water to flow over the exchanger pipes and thus start up the engine." Willsie had created the first solar device that could operate at night using the heat gathered during the day. He also announced that the 15-horsepower machine was the most powerful arrangement constructed up to that time. Beside offering a way to provide continuous solar power production, Willsie also furnished detailed cost comparisons to justify his efforts: the solar plant exacted a two-year payback period, he claimed, an exceptional value even when compared with today's standards for alternative energy technology.

Originally, like Ericsson and Eneas before him, Willsie planned to market his device for desert irrigation. But in his later patents Willsie wrote that the invention was "designed for furnishing power for electric light and power, refrigerating and ice making, for milling and pumping at mines, and for other purposes where large amounts of power are required."

Willsie determined all that was left to do was to offer his futurist invention for sale. Unfortunately, no buyers emerged. Despite the favorable long-term cost analysis, potential customers were suspicious of the machine's durability, deterred by the high ratio of machine size to power output, and fearful of the initial investment cost of Willsie's ingenious solar power plant. His company, like others before it, disintegrated.

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