Let It Shine: The 6,000-Year Story of Solar Energy

_Let It Shine:  The 6,000-Year Story of Solar Energy_ by John Perlin

Novato, CA:  New World Library, 2013

ISBN 978-1-60868-132-7

(xi)  The authoritative global network REN21 (Renewable Energy Policy Network for the 21st Century) reports that in 2012, one-fifth of the world’s electricity and one-sixth of the world’s total delivered energy was renewable.  Half the world’s new electricity-generating capacity added each year since 2008 has been renewable, and so is one-fourth of global and one-third of European generating capacity.  Excluding big hydroelectric dams, modern renewable power (chiefly wind and solar) adds more than 80 billion watts of capacity each year and receives a quarter trillion dollars of annual private investment, and in 2011 invested its trillionth dollar since 2004 - all despite subsidies generally smaller than what its nonrenewable competitors get.

(xix)  Twenty-five hundred years ago, for example, the sun heated every house in most Greek cities.  

(xx)  And as electricity began to power cities, the first photovoltaic array was installed on a New York City rooftop in 1884.

(5) The first account of the use of the gnomon for building comes from the Zhou dynasty, which was established sometime before the twelfth century BCE.  Zhou government officials considered proper orientation too important to be left to chance, and so they instructed builders to establish the cardinal points of the compass for exact siting.  The book _Zhouli_, which contained the rituals and rules established by the dynasty, explained how this would be accomplished.  Builders first had to determine when the equinoxes and solstices occurred, which could be pinpointed by studying the shadows cast by the gnomon.  The longest and shortest shadows of the year would mark the winter solstice and summer solstice, respectively.  When the shadow cast was half as long as the two solstice shadows, the observer would know that one of the two equinoxes had arrived.  At either equinox, the shadow cast by the rising sun would point west, and the shadow cast by the setting sun would point east.  Taking note of where the noon shadow fell, the observer would learn where true north and south lay.

(13)  Socrates according to Xenophon in the Memorabilia:  “Now in houses with a southern orientation, the sun’s rays penetrate into the porticoes [covered porches,] but in summer the path of the sun is right over our heads and above the roof, so we have shade…  To put it succinctly, the house in which the owner can find a pleasant retreat in all seasons… is at once the most useful and the most beautiful.”

[Soc:  "Do you admit that any one purposing to build a perfect house will plan to make it at once as pleasant and as useful to live in as possible?" and that point being admitted, the next question would be:

"It is pleasant to have one's house cool in summer and warm in winter, is it not?" and this proposition also having obtained assent, "Now, supposing a house to have a southern aspect, sunshine during winter will steal in under the verandah, but in summer, when the sun traverses a path right over our heads, the roof will afford an agreeable shade, will it not? If, then, such an arrangement is desirable, the southern side of a house should be built higher to catch the rays of the winter sun, and the northern side lower to prevent the cold winds finding ingress; in a word, it is reasonable to suppose that the pleasantest and most beautiful dwelling place will be one in which the owner can at all seasons of the year find the pleasantest retreat, and stow away his goods with the greatest security."

(http://www.gutenberg.org/files/1177/1177-h/1177-h.htm)]

(13-14)  Aristotle:  “What type of housing are we to build for slaves and freemen, for women and men, for foreigners and citizens?… For well-being and health, the homestead should be airy in summer and sunny in winter.  A homestead possessing these qualities would be longer than it is deep:  and its main front would face south.”

(14)  People from neighboring towns participating in the break with Athens in 432 BCE moved to Olynthus for protection against Athenian retribution.  The increase in population forced the Olynthians to establish a new district, which its excavators called North Hill.  The latitude was approximately that of New York City and Chicago, and the temperature often dropped below freezing in winter.  Approximately twenty-five hundred people lived there.

North Hill was a planned community from the beginning.  starting from scratch, the settlers could more easily implement the principal ideas of solar architecture.  The town planners situated the new district of Olynthus atop a sweeping plateau and built the streets perpendicular to each other, just as the Chinese had, with the main streets running east-west.  In this way, all the houses on a street could be built with a southern exposure, assuring solar heating and cooling for all residents - in keeping with the democratic ethos of the period.

(15-16)  Olynthian builders usually constructed houses in a blocklong row simultaneously.  The typical dwelling had six or more rooms on the ground floor and probably as many on the upper floor.  These houses were usually a standard square shape and shared a common foundation, roof, and walls with the other houses of the block.  The north wall was made of adobe bricks, which kept out the cold north winds of winter.  If this wall had any window openings, they were few in number and were kept tightly shuttered during cold weather.

The main living rooms of a house faced a portico supported by wooden pillars running parallel to the south side of the building.  The portico led to an open-air courtyard averaging 320 square feet, which was separated from the street by a low wall.  The courtyard provided a place where the occupants could enjoy the outdoors with maximum privacy;  and sunlight, the home’s primary source of illumination and winter heat, entered the house through the courtyard.

The house’s earthen floors and adobe walls absorbed and retained much of the solar energy that came in through its window openings facing the courtyard.  In the evening, when the indoor air began to cool, the floors and walls released the stored solar heat and helped warm the house.  To prevent cold drafts from coming through the open portico into the house, some builders constructed a low above wall between the pillars of the portico, parallel to the south wall of the house, allowing for the warming rays of sun in winter, while shutting out the cold drafts below.

The Olynthian solar house design worked well in summer and winter.  When the summer sun was almost directly overhead - from about ten in the morning until two in the afternoon - the portico’s eave shaded the openings of the main rooms of the house from the sun’s harsh rays.  In addition, the closed walls and contiguous dwelling barred the entrance of the morning and afternoon sun into the east and west sides of the homes.

(20)  The Architect Edwin D Thatcher studied the solar-heating capability of rooms facing south to determine the feasibility of indoor nude sunbathing during the winter.  To simulate actual conditions, Thatcher relied on weather data for a climate similar to that of ancient Greece and western Turkey.  He found that a naked person sitting in the sunny part of such a room would be relatively comfortable on 67 percent of the days during the colder months of November through March. The room used for this study was not as well protected as an average Greek living room, however - and of course the residents of the latter would have been clothed most of the time.  It seems safe to say that for most of the winter the sun would have adequately heated the main rooms of a Greek solar-oriented home during the daytime.  When solar heat was insufficient, charcoal braziers could be lit.

(26)  Windows of glass or transparent stone were a radical innovation.  Colored glass had been used for decorative items for almost three thousand years, but the Romans were the first - in the first century CE - to use transparent materials to make windows that would let in light but keep out rain, snow, and cold.

(34)  Faventius and Palladius recommended an ingenious way to make the floor of a sun-heated winter dining room an ideal absorber of solar energy.  The technique had been invented earlier by the Greeks and passed on in the writing of Vitruvius.  A shallow pit was to be dug under the floor and filled with broken earthenware or other rubble, and atop this a mixture of dark sand, ashes, and lime was spread.  This formed a black floor covering that easily absorbed solar heat, especially during the afternoon.  The mass of rubble underneath stored large amounts of heat and released it later in the evening when the room temperature cooled.  Faventius assured village owners that such floors would stay warm during the dining hour and “will please your servants, even those who go barefoot."

(37)  Confucius, writing of life three thousand years ago, stated that every son who lived at home attached a bronze burning mirror (a fu-sui, later called a yang-sui) to his belt when he dressed for the day.  He would also attach a fire plow, a wooden tool that relied on friction to generate sparks for ignition.  On days when the sun shone, the boy would focus the solar rays onto wood and start the family fire;  on overcast days he would take out his fire plow and rub its wood stick back and forth in a wooden groove to do the same.  The yang-sui was as ubiquitous in early China as are matches or lighters today.

(39)  The Greeks used burning mirrors to light the flame that marked the beginning of their Olympic games.  Plutarch, the famous Greek biographer who wrote in the second century CE, stated that when barbarians sacked the Temple of Vesta - the temple tended by the Vestal Virgins at Delphi - and extinguished their sacred flame it had to be relit with the “pure unpolluted flame from the sun.”  With “concave vessels of brass” the holy women directed the rays of the sun onto “light and dry matter,” which was immediately ignited, and their flame burned anew.

(100)  The Flemish salt manufacturers, Cecil’s [Queen Elizabeth I’s chief economic adviser] men explained, built long, shallow, watertight troughs that opened to the sea.  When operators wanted to fill them, windmills opened the floodgates to let in the incoming tide.  Once enough seawater had run in, the gates were shut.  Then solar heat went to work on the water, which evaporated after several days in the sun.  Only salt remained.  Workers shoveled the salt out and more water was let in to repeat the process.  The English praised the solar saltworks as “a great help for the sparing of firewood."

(103)  In 1887, the amount of sun-made salt surpassed the quantity manufactured with coal.  Solar manufacture of salt had grown to the point that visitors to Syracuse [NY], looking down from a hill in the city, could see a wide and shallow valley all covered with brown wooden troughs open to the sun.

(108)  Many had warned of an impending fuel crisis - warnings largely ignored by the public.  But the devastating effects of a series of coal strikes around the turn of the century, culminating in a massive strike in the winter of 1902, threw “a new and lurid light on [these predictions,]… for many a home has been fireless and many a factory has closed its doors,” according to Harper’s Weekly.  Charles Pope, author of Solar Heat, one of the first books on solar energy, agreed:  “The year of 1902 has added an awful chapter to the history of our need of a new source of heat and power,” he wrote.

(124)  [St Louis’ Willsie Sun Power Company solar power plant in 1904] As the sun warmed the water it traveled to a boiler, where ammonia was heated to produce a high-pressure vapor that drove a 6-horsepower engine.  Through condensation the ammonia returned to its liquid state and flowed back to the boiler.  The water circulated back to the collectors in a separate cycle.

The plant ran on sunless days and at night as well, when an auxiliary boiler powered by conventional fuel took over.  Newspapers in Saint Louis and New York announced the success of this twenty-four-hours-a-day solar-powered generator.

(125)  The solar-heated water produced during daytime operation [of Needles, CA in 1908] flowed from the collectors into an insulated tank.  The amount of water needed at the time went on to the boiler;  the rest was held in reserve.  After dark, when a valve to the storage tank was opened, hot water flowed out and passed over the pipes containing sulfur dioxide, and the engine could continue working.  Willsie could rightly claim, "This is the first sun power plant… ever operated at night with solar heat collected during the day."

(130)  He [Frank Shuman] first built a 1-foot-square hot box with blackened tubes inside that held ether, a low-boiling-point liquid.  The solar-heated ether vapor drove a tiny engine, the kind that was commonly sold in toy stores at the time for a dollar.  Shuman tried using a similar collector to run an engine somewhat larger than the first and was able to produce 1/8 horsepower.

NB:  1/8 hp is about the power a person can put out.

(139)  The Meadi plant could operate twenty-four hours a day.  A large insulated tank, similar to the one used by Willsie and Boyle, held excess hot water for use at night or during overcast or rainy days.  This enabled the engine to drive a conventional irrigation pump at all hours and in all weather, further increasing the efficiency of the plant.

Shuman set up a public demonstration of his sun-driven engine in late 1912.  But the boiler reached temperatures too close to the melting point of the zinc pipes.  Consequently the metal began to sag until, according to one observer, the pipes “finally hung down limply like wet rags.”  The trial run and to be postponed while the zinc pipes were replaced with cast iron.

(139-141)  Shuman’s solar engine compared very favorably to a conventional coal-fed plant.  True, the solar plant still had an enormous ratio of collecting surface to horsepower produced - exceeding 200 square feet per horsepower.  And the purchase price, at eighty-two hundred dollars, was double that of a conventional plant [but had a payback period of 4 years with coal at $15-40/ton]

NB:  25 square feet for 1/8 horsepower

(189)  Estimates of the total number of installations made in the Miami area between 1935 and 1941 vary widely - from twenty-five thousand to sixty thousand.  More than half the Miami population used solar-heated water by 1941 and 80 percent of the new homes built in Miami between 1937 and 1941 were solar equipped.

(190)  The federal government purchased some of the largest solar-heating systems, putting them in the officers’ quarters at the giant naval air station in Opa-Loka, outside of Miami, as well as in the Edison and Dixie Court housing projects, which had a combined population of 530.  In 1941, solar water heaters outsold conventional units in Miami by two to one.

(221)  All houses should be directed toward the sun, all of humanity should live in sunlight - Bernhard Christoph Faust [1824]

(223)  All Buildings of Men Should Face towards the Midday Sun (Zur Sonne nach Mittag sollten alle Haüser der Menschen gerichtet seyn) [book title]

(223-224)  “The sole aim of life is the correct orientation of buildings to the midday sun.  Everything else fades compared to the sun and its benefits - to receive the sun in its greatest abundance, the most important gift that God gave to man and animal."

(229)  [1826] Bavaria’s most respected technologist, Anton Camerloher, the royal Bavarian engineer first class, learned of Faust’s solar building principles through [Gustav] Vorherr [state architect for Bavaria, head of the state-run school of building arts, and publisher of the Monthly Journal for Building and Land Improvement].  After submitting these strategies to rigorous scientific analysis, he declared them “well founded” and enthusiastically joined Vorherr in his fight for their implementation in construction throughout the region.  Camerloher’s opinion on the Faustian doctrine greatly influenced King Joseph Maximilian to mandate implementation of Faust’s teaching in the construction of all new public and communal buildings in Upper Bavaria.  Several years later the Bavarian government published the basics of Faust’s solar building principles with the intent of guaranteeing that “all districts, police, and building departments in the Isarkreis [Upper Bavaria] will give these architectural ideas special attention and support.”  Other German States, such as Hessen and Prussia, followed suit.

(231)  Two municipalities lost to fire were reconstructed in line with Faust’s tenets - Schwaboisen in Bavaria and Palotsay in Hungary.

(235)  In 2009 the United Nations chose La Chau-de-Fonds as a World Heritage site.  The selection was made, according to the World Heritage Site web page, because of the “‘rationalist’ principles… adopted[,] which addressed the relationship between living conditions and ‘health.’  A town plan was developed in 1835 designed by one of Pestalozzi’s pupils (Charles-Henri Junod) and inspired by an ideal town called ‘Sonnenstadt,’ planned in 1824 by a Dr. Bernhard Christoph Faust.  Features included having most houses facing onto small gardens receiving the midday sun.”

This monument to Faust’s dream resonates with his exclamation written more than 150 years before the city’s selection as a World Heritage Site:  “Oh people, face your houses toward the midday sun to give yourselves and your children and their children until the tenth generation the warmth, life, power, joy and blessings of the sun."

(248)  One study cited by the panel [of the League of Nations] showed that a building which opened to the north needed 17 percent more heat during the winter than did a similar structure facing south.  Such findings led to the conclusion that proper siting could go a long way to holding down heating and ventilating costs for householders.

(248-249)  One of the largest and most sophisticated examples was the Swiss community of Neubuhl, now a district of Zurich.  Seven young architects organized Neubuhl as a cooperative housing project.  The two hundred apartments ranged from small bachelor residences to family dwellings with six rooms.  These units were apportioned among thirty-three separate structures perched on a mountain slope. Almost all the buildings faced south or slightly southeast and were spread far enough apart so that no building blocked another’s solar access during winter.  every unit received the same number of hours of sunlight in winter. [1930s?]

(266)  His [Keck] opportunity came in 1940, when he designed a house for an old friend, Howard Sloan, a Chicago real estate developer….  [Sloan] “The house was opened to the public in September as the Solar House.  On one Sunday we had 1,700 visitors.  The demand of the public was such that I subdivided 10 acres into 38 lots and opened it in April, 1941.  [Although] Hitler was overrunning countries in Europe, customers were becoming jittery, [and] prices were going up, houses sold faster than we could build them."

(296)  A solar-heating system there [Tucson, Arizona] could be expected to carry a much higher percentage of the heating load - especially if heating at night were not required.  Such was the case in the first solar-heated public building, Rose Elementary School, which was designed by Arthur Brown and built in 1948.

(299)  George Löf used another solar hot-air system, similar to the one he had developed in Boulder, to heat his newly built, ranch-style home in Denver, Colorado.  In Albuquerque, New Mexico, the engineering firm of Bridgers and Paxton built the first solar-heated office building in 1956.  This system cooled the building in summer.

(303)  [1873 - discovery of photovoltaic effect on selenium by Willoughby Smith]

(305-306)  [Charles Fritts] He spread a wide, thin layer of selenium onto a metal plate and covered it with a thin, semitransparent gold-leaf film.  This selenium module, Fritts reported, produced a current “that is continuous, constant, and of considerable force[,]… not only by exposure to sunlight, but also to dim diffuse daylight, and even to lamplight."

(330)  The photovoltaics industry also got its first significant opportunity to power land operations with the oil and gas industry during the mid-1970s.  Underground aquifers frequently contain salt water, which corrodes well casings and pipelines.

NB:  First non space applications for oil and gas warning bouys at sea, anti-corrosion on land.

(334)  In the fall of 1976, Hunts Mesa became the first solar-powered microwave repeater site in North America and one of the first in the world.

(354)  By 1977, fully 60 percent of California’s 250,000 pools were solar heated.

(386-387)  That Village Homes has not been replicated may be a result of timing.  As that neighborhood really started to take off, Ronald Reagan took office, and his administration’s dim view of solar energy still haunts us today.  An example of that administration’s anti solar bias is its reception of the document _Review of the Demonstration Program of Solar Heating and Cooling Technologies_, which arrived at the White House during Reagan’s inauguration.  The Department of Energy had paid the highly reputable consulting firm Arthur D. Little a quarter of a million dollars to complete the study.  The lead author did not consider the study controversial.  It outlined high expectations for what solar energy could accomplish if properly funded.  “The following day,” one of the members of the staff that produced the report recalled, “word came from the Reagan team:  ‘Do not release this report… copies are to be destroyed… no secret printings… no discussions.’”  And this was accompanied by a threat:  “If any word gets out, Arthur D. Little will not be compensated.”  The staff member added, “I had never witnessed anything so brutal.  There were no pretensions of free speech.  It was swift and ruthless.  One of the chilliest moments of my life.”  Under the Reagan administration, “solar bodies got decimated,” recalled Edgar DeMeo, director of photovoltaic research at the Electric Power Research Institute in the 1980s.  “Reagan dealt the renewable movement a crippling blow,” he added.  Doug Balcomb summed up the destruction brought about by Reagan:  “The president said in the 1980s, ‘The energy crisis, it’s been solved;  there wasn’t any problem left.’  So people weren’t concerned about it anymore, [since] people tend to follow that kind of a lead.  The few of us left working in the solar field in the 1980s were pretty lonely.  The momentum had evaporated."

(396)  In fact, the heat that such solar-energy systems [pool heaters and passive solar houses] harvest is far more compatible with house and pool heating than the energy that fossil fuels and nuclear power plants supply.  Very little energy is wasted, since the collection occurs on-site, doing away with the huge infrastructure required for supplying fossil-fuel and nuclear energy.  And when solar heating takes the place of electrical heating, it does away with the need to initially raise temperatures hundreds of degrees to run turbines, and the need to transport the resulting electricity hundreds, if not thousands, of miles in order to deliver the power to homes - which require a temperature increase of only 30 or 40 degrees, if not less, for household comfort.

Solar pool heating and solar architecture also demonstrate the power of aggregation.  each solar pool-heating system is small, but the combined heat produced by all such systems as of 2013 is equivalent to that produced by approximately five nuclear power plants.

(377)  “The highest average heat value of sunlight occurs about [the time of day] when it is most needed - at mid-day on the winter solstice,” and “a south wall receives almost _five_ times as much heat from the sun in winter as it does in summer” [Tod Neubauer’s emphasis in a study of natural heating and cooling of buildings from UC Davis]

(381)  He [Tod Neubauer] came up with one simple equation for success, a simple formula that Neubauer called the two-percent rule for finding the length of the required overhang on the south face:  multiply by .02 the height of the south-facing window(s) by the latitude.

(381-382)  The data collected and interpreted were translated into America’s first solar-energy ordinance, a reflection of Neubauer’s design ideas.  Journalist James Ridgeway succinctly explained the new ordinance:  “the basic idea… is that new housing built in Davis shall not experience an excessive heat gain in summer nor excessive heat loss in winter.”  It allowed builders two choices.  The first was a prescriptive path that stipulated a south orientation;  the majority of windows would be on the south side, and a minimum of windows would be on the east and west sides and shaded either by eaves, drapery, or vegetation.  The second path permitted more leeway as long as the building conformed to the designated heating and cooling loads set by the city.

(389)  Only subsidies in the form of tax credits, and the big jumps in oil prices in 1973 and 1979, kept the solar water-heater industry growing.  It grew from only twenty thousand solar water heaters installed during 1978 to nearly a million total by the end of 1983.

(390)  When the price of oil dropped in the mid-1980s, the Israeli government did not want people backsliding, as had happened in other parts of the world.  And so it required citizens to continue heating their water with the sun, by mandating the use of solar water heaters in buildings with more than four stories - in which the majority of Israelis live.  At the time of this writing, more than 90 percent of Israeli households own solar water heaters, making Israel the second-largest per capita user of such heaters.

(392)  Barbados is the third-largest per capita consumer of solar hot water.  In the 1930s, Florida solar water-heater companies exported their products to the Caribbean.  Some of these were sold in Barbados, but the Barbados solar water-heater story didn’t really get started until 1964….

Solar Dynamics’ new entry became the first solar water heater in the world to guarantee temperature performance adequate for all domestic-hot-water needs.

(395)  [Austria]  From the self-build groups emerged a national grassroots movement called the Renewable Energy Working Group (Arbeitsgemeinschaft Erneuerbare Energie).  The working group set up information centers and workshops to inform the public about, and to teach them to build, solar water heaters.

Michael Ornetzeder, “Old Technology and Social Innovations.  Inside the Austrian Success Story on Solar Water Heaters,” Technology Analysis and Strategic Management 15, no 1 (2001)

Michael Ornetzeder and Harald Rohracher, “User Led Innovations and Participation Processes:  Lessons for Sustainable Energy Technologies,” Energy Policy 34, no 2 (2006)

(397-398)  The success of Ærø Island [Denmark] so impressed all of Europe that the European Union decided to fund the doubling of the collector area of the Marstal solar farm, add to it a boiler that would be heated by locally grown willow chips, and a reservoir to hold the excess solar heat collected in summer for winter use.  It would demonstrate to the world the efficacy of district heating solely with renewable energy.

(402)  The use of photovoltaics for individual remote homes in the developing world was pioneered by the French in Tahiti.  Ironically, it was the French Atomic Energy Commission that initiated the program in 1978.  The agency’s nuclear testing in Polynesia had not endeared it or the French government to the Polynesian people.  Public opinion had to be shored up.

(405)  With 2 percent of its rural populace relying on solar power for their electricity, Kenya became the first country where more people plug into the sun than into the national rural electrification program.  What is more amazing is that photovoltaics’ ascendency occurred without government help.

(411)  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,” Osborn stated, 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.

(440)  Few realize the value of solar energy today.  The value of the global photovoltaic market alone climbed to over $82 billion in 2010.

(442)  Oil received thirty times more in subsidies from the federal government than solar between 1950 and 2010.  The International Energy Agency Agency reported that in 2012 alone thirty-seven governments spent more than $523 billion subsidizing fossil fuels while assisting renewables with almost one-sixth the funding.

(446)  In California, the state’s revised Title 24 building standards for 2013 will also move solar further into the mainstream.  The new code requires that by 2020 all new residential housing and by 2030 all commercial buildings produce as much energy as they consume, a designation called net-zero energy.  The new building rules require photovoltaics on all rooftops.

To meet the demand for net-zero energy, many architects are combining older solar technologies - solar architecture and solar water heaters - with the newest, photovoltaics.  Solar  pioneer Steve Strong built the first net-zero-energy house back in 1979 by using such a strategy.  Back then, people called this type of structure “an energy independent house.”

(449)  But a new German program provides incentives for homeowners to combine photovoltaics with electricity storage, allowing homes to actually cut themselves from the grid.  The program will reduce the twenty-year cost of a PV system with storage to 10 percent less than one without.  Once again, Germany leads the way in photovoltaics, this time toward autonomous living with solar electricity.

(458)  Robert James Forbes, _Studies in Ancient Technologies_ (Leiden, Holland:  Brill, 1964)

James Ring, “Windows, Baths, and Solar Energy,” American Journal of Archaeology, no 4 (1996)

(487)  Michael Ornetzeder, “Old Technology and Social Innovations.  Inside the Austrian Success Story on Solar Water Heaters,”  Technology Analysis and Strategic Management 15, no 1 (2001)

Michael Ornetzeder and Harold Rohracher, “User Led Innovations and Participation Processes:  Lessons for Sustainable Energy Technologies,”  Energy Policy 34, no 2 (2006)