History of Solar Energy

John Perlin

Author, Lecturer, Consultant — Solar Energy & Forest Preservation

Phone: 805.569 2740 • eMail: johnperlin@physics.ucsb.edu

John Perlin

Let It Shine:
The 6000 Year Story of Solar Energy

By John Perlin

With a Foreword by Amory Lovins

The New and Expanded Edition

© Copyright 2013 John Perlin

Chapter Descriptions

I. Early Use of the Sun

Chapter 1: Solar Architecture in Ancient China (6000 BC -)

Six thousand years ago Neolithic Chinese villagers had the sole opening of their homes face south. They did this to catch the rays of the low winter sun to help warm the interior. The overhanging thatched roof kept the high summer sun off the houses throughout the day so those inside would stay cool. Two thousand years later the Chinese began to formally study the movement of the sun throughout the year in relationship to the earth. Knowledge gained from these studies stimulated Chinese urban planners to construct the main streets of towns to run east to west to allow every house to look to the south to catch the winter sun for supplementary heating. Over the millennia Chinese cities followed such planning and still today the Chinese favor a south-facing home.

Chapter 2: Solar Architecture in Ancient Greece (500 BC-100 BC)

Socrates was outspoken about the value of building with the sun in mind for the comfort of the occupants. Aristotle also taught his students the value of designing houses to make maximum use of the winter sun and to keep the house in shade during the hotter months. Archaeological digs have confirmed that the ancient Greek builders followed the advice of these sages. Retrofits in Athens followed by whole cities such as Olynthus, Priene, Delos and many others, as well as rural dwellings, show that solar architecture became ubiquitous in Greece and its surroundings for centuries.

Chapter 3: Roman Solar Architecture (100 BC-500 AD)

Rome’s greatest architect Vitruvius saw solar houses while on duty as a military engineer in recently conquered Greece. When writing his great work On Architecture, he emphasized proper solar orientation for buildings and bath houses. From literature of the time it appears many followed Vitruvius’ instructions. Baths were especially popular among the Romans but demanded a great amount of heat. From the times of the early empire onward, most faced the afternoon sun in wintertime when they had maximum use. They also had their large windows covered with either transparent stone like mica or clear glass, a Roman invention of the 1st century ACE, one of the great breakthroughs in building and solar technology. Transparent materials like mica or glass, the Romans discovered, acts as a solar heat trap, admitting sunlight into the desired space and holding in the heat so it accumulates inside. Facing structures to the winter sun became so popular in Roman times that sun-right laws were passed, making it a civil offense to block one’s access to the south.

Chapter 4: Burning Mirrors (1000 BC-1800)

Three thousand years ago the Chinese discovered how to make concave reflectors to turn sunlight into fire. Many centuries later, around the 5th century BCE, the Greeks independently developed such solar devices. Both used them to kindle wood for cooking. When natural scientists of the renaissance learned of these inventions, many envisioned using them as the ultimate weapon, burning whole armies and fleets with concentrated power of the sun. The sketch books of Leonardo show that the great Italian technologist had great solar ambitions to use concave mirrors for industrial heating. People from London to Paris watched in awe as experimenters concentrated rays of the sun to melt metals and vitrify glass in seconds.

Chapter 5: Heat for Horticulture (1500s-1800s)

With the decline of the Roman Empire, the use of transparent glass all but disappeared. Glass was not used again to trap solar heat until the wealthy citizens of the Age of Discovery wanted to enjoy oranges and other fruits from Asia and the New World. South-facing greenhouses became popular to trap solar heat to encourage the growth of such exotic plants in the colder climate of Europe, unduly frigid due to the advent of the “Little Ice-Age.” Sometimes a greenhouse was attached to the south-side of home’s living room or library, transforming the “dull interior” into a “vibrant” and warm space where people would congregate. On sunny winter days the doors separating the greenhouse from the home were opened to allow sun-warmed air to circulate freely into the formerly chilly interior.

Chapter 6: Solar Hot Boxes (1767-1800s)

The increased use of glass during the seventeenth and eighteenth centuries reawakened the awareness of its ability to trap solar heat. In 1767, the Swiss polymath Horace B. de Saussure set out to determine how effectively glass could trap solar heat. Saussure built a rectangular box from wood, insulated with black cork and its top covered with glass. He placed a similar but smaller glass-covered box inside. When he tilted the box toward the sun, the inner box rose above the boiling point of water. Because of the large amount of solar heat the device retained, it became known as a Hot Box. The hot box became the prototype for solar thermal collectors used to heat water and homes. Saussure’s hot boxes also modeled with amazing precision the dynamics of global-warming with the glass acting as an atmosphere soaked with excess carbon dioxide stopping solar heat absorbed by the earth from re-radiating into the sky.

II. Power From The Sun

Chapter 7: The First Solar Motors (1860-1880)

Alarmed by the prodigious amount of coal consumed as the industrial revolution moved forward, a French mathematics professor, Augustine Mouchot, warned that “Eventually industry will no longer find in Europe the resources to satisfy its prodigious expansion.” He then asked, “What will industry do then?” It must “reap the rays of the sun,” the French professor concluded. Mouchot first studied what had already been done in times past to put solar energy to use. His research led him to decide to build a concave mirror with a glass-covered boiler at its focus. Exposed to the sun, it vaporized enough water to run the world’s first solar-powered steam engine. He went on to construct even larger sun machines. In one experiment, he produced electricity, used it to separate hydrogen and oxygen from water, and then store the hydrogen for fuel when the sun did not shine.

Chapter 8: Two American Pioneers (1872-1904)

The nineteenth-century Swedish-American engineer John Ericsson, well-known for inventing the iron-clad battleship the Monitor which helped turn the tide of the Civil War in the Union’s favor, believed that the sunny areas of the world were the place for sun-driven motors. “The application of the solar engine in these regions is almost beyond computation while the source of its power is boundless.” Ericsson wrote. In contrast, he feared that “the time will come when Europe must stop her mills for want of coal.” The specter of collapse due to fuel shortages gave the inventor such a sense of urgency that he devoted the last two decades of his life to pursuing the development of solar engines.

Aubrey Eneas actually installed three sun machines that ran irrigation pumps, all of them eventually in Arizona. The state had no indigenous fuel like wood or coal but it did have lots of sun so ranchers who needed to run pumps looked seriously to solar as an alternative. Eneas recognized the market for his sun machine whose height measured six stories and weighed four tons. Eneas exhibited his prototype at an ostrich farm in Pasadena, California where it pumped 1500 gallons of water per minute. One reporter predicted, “If the sun motor will pump water, it will also grind grain, saw lumber, and run electric cars.”

Chapter 9: Low-Temperature Solar Motors (1885 - 1915)

Others interested in commercializing solar motors shied away from those concentrating the sun’s energy as too complex and expensive to ever succeed. Charles Tellier, in 1885, came up with a very simple design. He angled ten metal solar collectors against the outer wall of his workshop near Paris. He didn’t try to produce steam from water. Rather, he passed ammonia through them because of its lower boiling point. Even in a temperate climate like France, the system worked well. Reading about Tellier’s work in the scientific journal Nature led two American engineers Henry Willsie and John Boyle to try to run a solar plant in Needles, California with another fluid – sulfur dioxide – which also had a lower boiling point than water. To run their plant twenty-four hours a day the engineers stored excess heated water in an insulated tank.

Chapter 10: The First Practical Solar Engine (1906-1914)

Frank Shuman, an entrepreneurial inventor, came up with an even more efficient design of a solar-concentrating plant in 1912, consisting of long trough-shaped reflectors which focused sunlight onto glass-covered heat absorbers through which water passed. For around seventy years the Shuman’s installation ranked as the largest solar power station ever constructed. Scientific American hailed it as “thoroughly practical in every way.”

III. Solar Water Heating

Chapter 11: The First Commercial Solar Water Heaters (1891-1911)

The first solar water heaters were just metal tanks left out in the sun. By late afternoon during summertime, they held enough hot water with which people could shower. Clarence Kemp, a Baltimore manufacturer of heating equipment, came up in 1891 with the idea of putting several cylindrical water tanks inside a hot box in 1891. As solar heat accumulated in the box, water inside the tanks heated and remained hot longer than bare tanks exposed to the sun. Kemp called his invention the “Climax.” It has the distinction of being the first solar water sold commercially. Its biggest success occurred in California during the end of the nineteenth century.

Chapter 12: Hot Water – Day and Night (1909-1941)

Although the Climax Solar Water Heaters’ improved performance made them superior to bare tanks, people still had to wait for the sun-heated water to warm up in the morning as they cooled down at night with nothing more than a sheet of glass between the heated tanks and the night air. William J. Bailey, an inventor living in a sunny suburb of Los Angeles, noticed the problem. He solved it in 1909 by dividing the solar water heater into two separate units – the solar heat collector and hot water storage tank. Bailey’s solar heat collector, not that different from those used today, consisting of a shallow hot box containing water pipes soldered to a metal plate painted black connected to a separate insulated storage vessel. Bailey called his product the Day and Night Solar Water Heater as it provided consumers with steaming sun-heated water day and night. Between 1909 and the early 1920s thousands were sold.

Chapter 13: A Flourishing Solar Industry – 1923-1950

The solar water heater industry saw even greater success in Florida. Its expansion went hand-in-hand with the building boom of the early twenties. By 1941, as many Miamians relied on the sun to heat their water as did those using electricity, the only alternative. But war came, the government froze the non-military use of copper, the metal used for the piping and the heat absorber. Consequently, the industry came to an abrupt halt. After the war, Florida Power and Light, the local utility, lured solar water heater owners to electric ones by offering them large discounts and temporary reduced rates.

Chapter 14: Solar Water Heating Worldwide – Part 1 (1930s-1960s)

Not every country had easy access to fuels like America. Israel in the 1950s had to ration electricity because it did not have enough generating capacity. Energy police enforced a ban on electric water heating – the way most Israelis heated their water - during the day and evening so industry could continue to function. Levi Yissar, an Israeli engineer, realized that solar water heaters much like those in Florida but adapted to the Israel climate would allow people to have hot water twenty-four hours a day. The Israeli public bought tens of thousands. The Japanese have always loved their hot baths. Those living in the low lands had little fuel. The Japanese saw the sun as their answer. By 1969 Japan had almost 4 million solar water heaters installed.

Chapter 15: Saving Airmen with the Sun (1943-)

The downing and rescue in 1943 of Ace Eddie Rickenbacker, America’s top pilot during World War I, led to the invention of the first practical emergency solar desalinator. “It was the experience of Eddie Rickenbacker drifting on his little life raft, almost dying of thirst,” solar scientist Dr. Maria Telkes recalled, that made her “realize the necessity of a source of fresh water for those men.” She developed a practical compact solar desalinating kit so future airman cast adrift would go without fresh water. The design Dr. Telkes came up with adhered to the principles discovered by Saussure. The Navy and Coast Guard made the Telkes’ solar desalinator standard fare, “since,” in the words of the military, “drinking water is the most essential thing” for those stranded in Pacific waters.

IV. Solar House Heating

Chapter 16: Solar Building during the Enlightenment (1807-1850)

Dr. Bernhard Christoph Faust, the man responsible for reviving solar architecture in Europe in the early 19th century, lived in a passive solar house built in 1649 in the tiny German town of Bueckeburg. After twenty years there, he suddenly latched onto the idea in 1807 that all houses in Europe should open up to the midday sun as his did. For the next forty years until his death Faust devoted his life to studying and proselytizing such building principles. In 1817 he finished the manuscript to the first book entirely focused on a solar topic, entitled, All Men Should Build Their Homes to the Midday Sun. His ideas would not have had much effect on the world had they not piqued the interest of the very influential Bavarian state architect Gustav Vorherr. Thanks to Vorherr’s relentless efforts, Bavarian and Prussian kings became the acolytes of Faust, mandating their subjects to build schools and new homes according to the teachings of Faust. Urban planners reconstructing the burnt to the ground city of Swiss city of La Chaux-de-Fonds based the work on a circular put out in 1834 by King Wilhelm Fredrick of Prussia containing a blueprint for realizing a solar city according to Faust’s idealized Sonnenstadt [Solar City] plan drawn up in 1807. The city’s solar oriented streets and houses remain intact.

Chapter 17: Solar Architecture in Europe after Faust and Vorherr (1850-1939)

The slums of nineteenth-century industrial cities showed, in Fredrich Engels words, “how little space a human being can move, how little air – and such air! – he can breathe, how little civilization he may share and yet live.” For Engels only the overthrow of the capitalist class could change this horrid situation. Reformists in the late nineteenth and early twentieth century had another answer - provide to the masses structures naturally warm, healthy, and illuminated based on solar building principles. No nation between the two world wars took on the task more seriously than did the Germans. Functional building relying on the ideas of social justice and solar orientation resulted in multiple apartment complexes oriented to take advantage of the sun in winter throughout the urban centers of Germany. Similar housing spread to Holland, Sweden, and other northern European countries. The rise of Hitler ended the solar architectural renaissance in Europe.

Chapter 18: Solar Heating in Early America (1200-1912)

Native Americans in the southwest built, in many instances, according to solar design principles. North America’s oldest continuously inhabited city – Acoma – serves as an excellent example with each unit tiered so every dwelling could catch the winter sun. William Atkinson, an early twentieth-century architect and urban planner, confirmed through scientific studies the wisdom of the builders of Acoma. By researching the apparent motion of the sun and variations in the angles of sunlight at different seasons, Atkinson produced diagrams that demonstrated the amount solar penetration of building through differently oriented windows. He judged south windows as the best fenestration. Atkinson went further than his predecessors by measuring how much solar heat each window orientation might trap in summer and winter. He did this by building a device he called a "sun box'' similar to de Saussure’s hot box—except that Atkinson’s box was constructed to simulate a window and room.The summer tests confirmed his hypothesis that east and west windows admitted too much summer sunlight. The most spectacular results, however, occurred on December 22. The temperature of the south-facing box rose to 1I4°F, when it was only 24°F outside, leading Atkinson to conclude, that if houses are properly situated, "the sun's rays are not of indifferent value in the heating of our houses."

Chapter 19: An American Revival (1931-1950s)

The solar accomplishments in Germany and other European countries verified the value of building with the sun in mind. These studies began appearing in American architectural journals as well. Well-known Chicago architect George Fred Keck was the first in America to apply their results in his design of homes in the Windy city and its adjoining suburbs. In the late 1930s a Keck solar house warmed up so quickly one winter morning when the outdoor temperature rose to only -5 degrees F that the thermostat shut the furnace down by 8 am and it didn’t start up until the early evening. The media caught wind of the story. Newsreels and national magazines spread the word about the house that needed very little heating fuel even in subzero weather. One newspaperman called the house a “solar home.” The name stuck. By 1941 Keck had designed the first completely solar-oriented community to be built in modern America. After the war, a nation-wide construction firm, hired Keck as its architect and advertised solar house as “The most talked about home in America.” While interest in solar homes peaked in the early 1950s, those built did not fall apart or stop working. The family occupying one of Keck’s solar houses, for example, reported in 1979, according to the Chicago Sun Times, “The temperature can dip to zero, but if the sun is shining, the family turns off their furnace as soon as they get out of bed in the morning. Otherwise the house gets too warm.” The Sun Times reporter later visited the house “on one of the most stiflingly hot days of August. Sitting in the living room, she found the interior “pleasant although none of the air conditioners was operating.”

Chapter 20: Solar Collectors for House Heating (1882-1962)

The earliest instance of putting to work the solar hot box for house heating dates back to the early 1880s when Edward S. Morse, a self-taught world renowned botanist and ethnologist, attached a device closely resembling a large hot box to the south wall of a building with vents that permitted outdoor air to enter the box and naturally flow up as it heated eventually heating the interior rooms. Scientific American called the invention “an ingenious arrangement for utilizing the sun’s rays in warming our houses. It is so simple and self-contained that one wonders that it has not always been in use.”

Godfrey Lowell, a wealthy Bostonian, decided to fund research at M.I.T for finding ways to economically heat houses with the sun. For the first house, engineers covered the roof with solar water heater collectors similar to ones built by Day and Night. Instead of using the hot water for bathing or washing the dishes, it went into a 17,000 gallon storage tank. Air blown over the tank warmed and circulated hot air into the house when it cooled down..

To develop a more cost-effective system, M.I.T. workers combined the functions of collecting, storing, and distributing solar heat into a single unit. They stacked water cans behind a south-facing glass façade of a long and narrow laboratory consisting of ten cubicles. During the day solar energy heated the water in the cans. Insulating curtains separated the interior of the cubicles from the warming water cans when the interior got too hot and opened when any of the cubicles needed heat. Insulating shades between the heated cans and the glass were shut at night to keep their heat from radiating back into the night sky. These simple water walls supplied up to 48% of a cubicle’s heating needs throughout the very cold New England winter.

The third M.I.T. House combined solar architectural strategies with solar heat collectors. In its three years of operation between 1949 and 1952 the south-facing windows supplied between 33 and 39% of the heat to the house while the collectors provided 36% to 49% of the house’s heating needs. Body heat and waste heat from appliances contributed another 16%. The free heat from the sun and activities inside left a very small amount needed from an electric heater.

V. Photovoltaics

Chapter 21: From Selenium to Silicon (1876-)

Willoughby Smith, an English electrical engineer, reported in 1872 the light sensitivity of selenium. Exposure to sunlight increased the material’s conductivity. The discovery intrigued European physicists. In 1876 two British scientists, William Grylls Adams and Richard Evans Day, discovered that light shone on these bars produced something never seen before: light, not heat, generating a flow of electricity in a solid material. Adams and Day called current produced this way, “photoelectric.” Today, it is known as the photovoltaic effect. American inventor Charles Fritts put together selenium modules and placed a test array on a New York rooftop in the mid 1880s. He optimistically predicted that soon his modules would compete on the market place with the new electric power plants established by Thomas Edison. Many envisioned Fritts invention as entirely superseding the steam engine and ending all the pollution endemic to them. But try as they may, no one could increase selenium’s low conversion of sunlight into electricity and scientists concluded that to realize the vision of photovoltaics powering the world would require finding a new photovoltaic material.

While working on the newly-discovered silicon transistor, Daryl Chapin, Calvin Fuller and Gerald Pearson of Bell Laboratories came up with a solar cell that could convert enough solar energy into electricity to run everyday electrical equipment. The New York Times praised the discovery “as the beginning of a new era, leading eventually to the realization of one of mankind’s most cherished dreams - the harnessing of the almost limitless energy of the sun for the uses of civilization.”

Chapter 22: Saved by the Space Race (1958-)

Despite grandiose praise for the new solar cell from the media suggesting the new device would one day “provide more power than all the world’s coal, oil and uranium,” for the first years after its discovery applications remained elusive. The military though showed intense interest. Both the Air Force and the Army viewed the Bell invention as vital for its top-secret satellite program. Thanks to its semiconductor twin – the transistor – the power draw of the electronics onboard was so reduced that solar cells would suffice to run them. The successful launch of America’s Vanguard, the world’s first satellite relying on silicon solar cells for powering the instruments on board, proved the value of the Bell invention. Their longevity made photovoltaics a critical component for the growing American and Russian space programs. Prior satellites, including the first two sputniks, powered solely by batteries died after only several weeks in orbit compared with solar-powered satellites that lasted for years. Their new found life span has revolutionized life on Earth. It turned Space into a battlefield giving the Americans a birds-eye view of their adversary and providing pin-point accuracy of its missiles. Telecommunication satellites made world-wide telephony ubiquitous and cheap. Global news became instantaneous. Dish TV has brought television to millions. Cellular would be unthinkable. The unexpected and relatively large demand for solar cells for space proved crucial for the photovoltaics’ commercialization, development and future successes.

Chapter 23: The First Large-Scale Photovoltaic Applications on Earth (1968 -)

The success of photovoltaics in Space gave those a vision of how solar cells might benefit activities down on Earth, especially for remote terrestrial electrical demand where power lines do not reach. The first commercial use of photovoltaics on Earth powered navigation horns and lights on offshore oil rigs previously run by huge batteries. Coast Guards throughout the world adopted photovoltaics to run their buoys and lighthouses. Photovoltaic-powered microwave repeaters connected remote towns and homesteads to the telecommunication grid, allowing them to access the same radio, telephone and television services that their urban neighbors had to long enjoyed. By the mid 1980s, photovoltaics had become the energy source of choice worldwide for remote industrial power needs.

VI – The Post-Oil Embargo Era

Chapter 24: Prelude to the Embargo (1945-1973)

During the first three decades after World War 11, few people in the United States and most other western countries made use of solar energy. Oil, gas, and electricity were cheap and getting cheaper. Active promotion by utilities resulted in a much more fuel-intensive life-style. Electric consumption alone increased fourteen fold. The gas companies also succeeded in selling record amounts. A few far-sighted individuals at the time warned of an impending energy crisis. As early as 1952 the President’s Materials Commission appointed by Harry S. Truman came out with a report predicting that America and its allies would be short of fossil fuels by 1975. The report urged that solar energy be developed as a replacement.

What the country didn’t know was that it had an oil shortage going on for many years before. In 1947 America’s domestic production slipped below its consumption and the country had become a net importer of oil. As long as the supply stayed cheap and kept flowing, no one cared. When the oil embargo hit in October 1973, the United States and much of the rest of the world woke up high energy prices and long gas lines at the pumps. The United States government did have one energy alternative in mind – nuclear power. It wasn’t really an energy choice though but a Cold War solution to a very sticky problem. In 1954 the Americans were the only possessors of the hydrogen bomb and such a weapon had scared the world out of its wits. To counter these fears, the United States government presented the Good Atom, the Peaceful Atom, by supporting of the development of nuclear power through its Atoms for Peace program. Although the President’s Materials Commission had proposed an equally weighted research effort for solar and nuclear, the American government under the incoming Eisenhower Administration and until Obama took office remained biased towards the nuclear option. The discovery of previously unseen documents reveal the strong support for solar, especially solar photovoltaics, by expert advisory groups to various presidential administrations from Eisenhower to Reagan, only to be rejected and suppressed by them to perpetuate support for fossil fuels and nuclear energy.

Chapter 25: Solar Successes in the 1970s and 1980s

In response to the oil crisis of 1973, people took a new look at the potential of solar energy to replace fossil fuels and nuclear energy. Many embraced solar energy because it seemed to offer an environmental, political and social alternative to the old corporate structure running oil, coal and nuclear power. These attributes especially appealed to those who had formerly opposed the Vietnam War and had been involved in the counterculture of the 1960s. It is therefore not without irony that swimming pools, associated with wealth and social decadence, became the first success story of solar in America during the 1970s and 1980s. Inexpensive plastic solar-pool heaters dominated the solar market for almost a decade. The other solar success story came from opposite spectrum with hippies applying solar ideas to drop out from Korporate America in comfort. Their inspiration came from indigenous architecture that had made maximal use of the resources surrounding them, especially the sun, with minimal reliance on technology and capital, just had the Chinese, Greeks and Romans had done, too. Open minded engineers analyzed these new approaches and concluded that they worked, and in many situations, even better, than ever increasing sophisticated heating and ventilating equipment. Those building with nature, rather than fighting it as had been the case in the construction industry, gained increasing popularity among architects, engineers, scientists, bureaucrats and the public. Raymond Bliss, for example, a physicist, writing for the prestigious Bulletin of the Atomic Scientists, demonstrated more energy could be saved through the massive building of well designed solar homes than all the oil drilled on the Alaskan slope compared to oil drilled from Alaska’s North Slope.

Chapter 26: America’s First Solar City (1920s-)

Davis, California has had a rich solar legacy. Studies of early solar water heaters began in the late 1920s took place there at the University of California’s Agriculture Experimental Station. By the 1940s the work of George Fred Keck and MIT helped introduce ideas of solar architecture at the local university. Work on solar orienting animal enclosures for healthier poultry and livestock commenced at the Davis campus during the 1950s, as did the study of microclimates for better crop management. Interest also developed in using vegetation for climate control of farm workers’ housing. All of these issues became the core curriculum for many. Applying what they learned at the university to the local setting became imperative for students turned activists during the 1970s. With the support of a newly elected city council sympathetic to such ideas, the Davis Solar Ordinance became law. Its passage inspired at the far end of the city the development of Village Homes, the largest planned aggregation of passive sun-oriented living spaces since the construction of Olynthus.

Chapter 27: Solar Water Heating Worldwide Part II (1973-)

The oil shocks of 1973, 1979, and 1980 brought renewed interest in using the sun to heat water and buildings and generate power for industry. A million solar water heaters were installed in the United State between 1973 and 1986. Seven million were put up in Japan. Declining oil prices and increasing supplies in the mid 1980s eclipsed interest in the solar alternative in these two large markets. Solar water heating did not die though. It just spread to other countries in need of a good option to fossil fuels, giving rise to an even more vibrant and international solar water industry. Government intervention combined with high energy costs in Cyprus and Israel has resulted in these two Mediterranean countries being highest per capita users of solar water heating in the world. Today, more than 90% of all Cypriot and Israeli households rely on the sun for hot water. Austria and Barbados rank third and fourth. In Austria, one out of eight households heats their water with solar and many of them have combined solar water heating with house heating. The people of Barbados have seen the island’s solar water heater industry grow from a few hundred in 1974 to make up 50% of the water heaters now, reducing the country’s dependence on imported oil. That the largest solar water heating installation resides on Aero Island off the west coast of Denmark might surely comes as a surprise to many. China though dominates the international solar water heating market with nearly 80% of all installations. Currently more than 50,000,000 solar water heaters worldwide produce an energy equivalent of 124 million barrels of oil on an annual basis.

Chapter 28: Photovoltaics for the World (1978-)

For many years rural electrification experts planned to power the developing world’s towns and villages the same way that Western countries had – by building centralized generating plants and stringing wires to individual homes. Running transmission lines in this way has proven very costly with little chance of return on the investment. As a consequence they bypass most of those living outside urban areas, leaving billions without access electricity and relying on ad hoc solutions such as generators, kerosene lamps, candles and fire. Kerosene lamps, candles and fire provide poor lighting, emit suffocating smoke and always entail the danger of burning consumers and their homes. All of these options also require imported fuel not always available but always expensive. In contrast, if properly installed and maintained, a solar module will generate electricity for decades. Photovoltaics, combined with storage, offers complete energy autonomy. France led the way in solar rural electrification by deciding in 1978 to put panels on all huts in the outlying islands of the South Pacific. Middle-class Kenyans living outside of the larger cities purchase their own electrical power stations by buying modules at the local general store. More rural Kenyans have plugged into the sun than into the national grid. The experiences in French Tahiti and Kenya suggest that the principal power source in the non-electrified world will be solar.

When Charles Fritts boldly predicted 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 believed, the selenium modules would enable “each building to have its own plant.” Shell oil came to the same conclusion a hundred years later, stating, “In our opinion, the dispersed generation of photovoltaic energy affords the earliest opportunity for photovoltaics to contribute to America’s growing energy needs.” Markus Real, a Swiss engineer, put the vision of Fritts and Shell Oil to the test when he installed 3 kilowatt solar power stations on three hundred rooftops in Zurich. As Real logically put it, “It makes sense, absolute sense. The roof is there. The roof is free. The electrical connections are there.” The avoidance of transmission, Real brilliantly realized, allows solar to compete against the retail cost of electricity which far exceeds the wholesale price at the point of generation. The Zurich experience led to many nationally supported rooftop programs, culminating in Germany in 1999 with the national feed-in-tariff which generously rewarded those who chose the sun as their energy source. The German feed-in-tariff, combined with the mass production of photovoltaics in China and its subsequent low price, grew installations from less than a gigawatt worldwide in 1999 to more than a hundred as of today.

Chapter 29: Better Cells, Cheaper Cells (1956-)

To realize the dream of solar cells covering the world's rooftops and powering utilities, their price must continue to drop. Presently crystalline silicon remains the dominant photovoltaic mate¬rial, basically the same substance that was discovered at Bell Laboratories in the early 1950s. Its continued widespread use rests on the fact that, as one expert explained, "It works and it works for a long. Automation, economies of scale and better use of the incoming light has brought the price down of silicon solar cells from almost $300 per watt to under a dollar. Another avenue for bringing down the cost involves depositing a small amount of a photovoltaically active sub¬stance onto an inexpensive supporting ma¬terial, such as glass or plastic. Solar cells made in this fashion are called thin films. It has long been believed that this process would consume much less of the expen¬sive photovoltaic ingredients and that it would also lend itself to automation. Despite many attempts, thin films have not reached efficiencies comparable to silicon, leaving silicon solar cells to continue their reign as the work horse of the industry. In the 1980s, people argued whether the price of phototovoltaics would get down being competitive with electricity from transmission lines, which those in the industry call¬¬ grid parity. Coming to the end of the first decade of the 21st century, everyone agrees grid parity has already been reached at some sunny regions of the world where the price of electricity is extremely high and will soon extend to the rest of the globe in the next few years, depending on the amount of solar radiation received and the cost of electricity arriving at the point of demand.


When I tell people that I have published a book on a history of solar energy book, everyone comments, “It must be very thin.” To their surprise, Let It Shine: The 6000-Year Story of Solar Energy, has 451 pages! Great progress has been made in the solar field. When the first silicon-solar array was built in 1954, it consisted of less than a watt. Since then, one hundred billion watts have been installed. Over the last decade the heating capacity of the solar water heater industry has grown six fold. Solar concentrators have grown from a few kilowatts in 1980 to several million today. No one reading the mainstream media could know that solar has made such progress. It is my hope that my new book will bring new light to the progress of solar energy. The disasters of Fukushima and Hurricane Sandy have given to momentum to solar. By combining the oldest and the newest solar technologies – architecture and photovoltaics – the autonomous house becomes possible. Its development could do away with power lines altogether, just as cell phones have gone wireless and in the process diminished the importance of land lines. The increasing use of solar energy will reduce our dependence on nuclear and fossil fuels, reducing the danger of radioactive fallout and global warming and their consequences that threaten the well-being of all things both big and small including us. As energy expert Amory Lovins pointed out, “Rediscovering our solar rootstocks, and grafting modern efficiency technologies to them, offers good news indeed – for all people, and for the earth.”

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