SEGS and gas

November 10th, 2008, Published in Articles: Energize

by CM Meyer, technical journalist

The title of this article is not a misprint. It is not “Sex and gas”, but indeed SEGS (Solar Energy Generating Systems) and gas.  But as we shall see, SEGS is indeed the way the way solar energy generation can and has been made “more sexy”.

“Altogether, nine trough power plants, also called solar energy generating systems (SEGS), were built in the 1980s in the Mojave Desert near Barstow, California.  These plants have a combined capacity of 354 megawatts (MW), the world’s largest generating capacity of solar electricity, and today generate enough electricity to meet the needs of approximately 500,000 people” (Ref.14;1).

SEGS, or trough technology as it is also known, is far older and more established than power towers, as we shall soon see. Its ancestry can be traced back to the original burning mirrors and hot boxes, used by the very first pioneers investigating concentrating solar power. Huge solar power developments are currently planned for Spain and the Mojave Desert, where a solar park of more than 500 MW is surprisingly close to reality. Enormous solar farms using SEGS technology are also planned for North Africa, where the power will be carried beneath the Mediterranean to Europe by submerged HVDC cables. An even bigger plan is for just about all the entire energy in the United States to be generated from solar power, particularly SEGS power.

This is not science fiction, but science fact.  Strangely, SEGS, which is often touted as the means to replace the world’s dependency on fossil fuels, actually depends on natural gas to produce viable deliverable electrical energy on demand. And the story soon gets a lot stranger, for the economics of building SEGS plants, in fact, the economics of building all solar energy plants, is crucially dependant on the going price of fossil fuels.

In fact, the company that built the first SEGS plants went bankrupt because fuel prices plunged in the late 1980s and early 1990s. But, despite this, the plants they built have continued to generate 354 MW of electricity at a profit. Like much of solar power, there is quite literally nothing new under the sun. To understand SEGS, we first need to understand something of Frank Shuman, who developed and pioneered many of the key principles nearly a century ago. Like much of solar energy, we need to go back in time to understand the future.

Desert dreams
“He [Shuman] hoped to build 20 250 square miles of reflectors in the Sahara, giving the world  in perpetuity the 270 million horsepower per year to equal all the [coal] fuel mined in 1909” (Ref.1;110) .

When you look at them, Frank Shuman’s dreams are very similar to those currently published in Scientific American nearly a century later. His vision of building  20 250 square miles of  reflectors in the Sahara is uncannily close to the 16 000 square miles of solar concentrators in the USA proposed in “A Solar grand plan” by Zweibel et al in a recent issue of Scientific American.

There are many differences between the two visions.  Shuman was not thinking of generating electricity but of pumping water for irrigation, by using steam power generated by the heat of the sun. And, although he included the Southwest USA in his plans and built several demonstration plants in the USA (in the Philadelphia suburb of Tacony, as we shall see), his main success was building the what was then the world’s largest solar powered pumping plant in Africa. In Meadi, Egypt, to be precise.

But there are some surprising similarities in the two visions. Shuman’s proposals and actual achievements, now largely forgotten, were also published in Scientific American. And the magazine, initially skeptical, soon realized that solar power was something real and practical. A short summary of who Frank Shuman was, what he achieved, and why the world turned its back on solar power after such a promising start had been made will help us to understand the next logical step in the solar saga, the building of SEGS. 

An immensely practical man
“When a sky light would break [in the USA before 1892], anyone standing underneath would be seriously injured or even killed.  In many cases, aesthetically unappealing nets would be suspended below skylights to prevent any tragic occurrences.  By the age of twenty-eight, Shuman had patented a process for the manufacture of wire glass using a regenerative furnace to melt the glass, annealing ovens and sets of specially designed rollers to roll the glass into sheets”(Ref.3;1).

Not bad going for a man who, although possessing s strong desire to learn and practice science, left public school after only three years.  The success of this invention enabled Frank Shuman to leave the Tacony Iron and Metal Company and begin a career as an independent inventor in 1892. And what an inventor!  In 1903, he had invented and patented a process for concrete building foundations making concrete piles with a hollow metal pole at the center. This eliminated the need for massive excavations for foundations. 

 In 1908, Shuman invented and patented a machine that effectively removed oil from wool. And, in 1914, the same year that World War One broke out, he invented the most durable safety glass to date, experimenting with and improving upon gas masks of his day.

Today, these inventions of Frank Shuman are largely forgotten: even though his pioneering work on concrete piles quite literally supports most large buildings today. The foundations of Shuman’s work came not from academic learning, but from practical work experience, first as a chemist in a dye factory, and then working in his uncle’s firm, the Tacony Iron and Metal Company, where he taught himself much about engineering.

Also largely forgotten is how close Frank Shuman came to getting the world to use solar power on a practical, commercial scale just before World War One. Few people today know or care that the key technology for the huge SEGS solar power plants planned for tomorrow, the trough-shaped reflectors that concentrate the sun’s heat onto a pipe in their centre, did not really come from  research programmes in Israel and the USA that involved millions of dollars, many Ph.Ds and years of work.

The Boys-Shuman concentrator, the basis of the more efficient concentrator in today’s SEGS plants, came from the hard work of a humble and most likable man who never even completed high school. Indeed, when later offered an honorary masters degree by Cornell University for his pioneering work on solar energy, Frank Shuman declined it, saying that he could not accept such an honor because he never completed any educational degree.

Back to the box
“With the high temperatures involved, the losses by conduction and convection are so great that the power produced was of no commercial value.  Where…mirrors are used, the primary cost…and the apparatus necessary to continuously present them to the sun, have rendered them impracticable” (Ref.1;101).

One of the first things Shuman did when he began work on solar energy in 1906 was to apply his common sense and practical business experience to what others had achieved in the field. He quickly realised something that other pioneers in the field (Mouchot, Ericsson and Eneas) had learned the hard way: the big solar concentrators that had been built, and were still being built in the USA in the first decade of the twentieth century, were as impractical as the medieval plans to build huge burning mirrors. 

The contraptions made by Eneas between 1898 and 1904 were gigantic. They resembled huge, dish-shaped radio receivers, made of thousands of silvered glass mirrors on a heavy, metal frame, and usually worked quite well. That is, until hailstorms smashed the mirrors or storm strength winds toppled the massive structures. Eventually, they were toppled by something else: costs. These big machines were simply too expensive to produce at a profit, something Eneas was eventually forced to realise. Even today, plans to built smaller dish-shaped receivers (to heat air to drive specially designed Stirling engines) remain the most expensive of all the solar power options, costing (per m2) 5 times what parabolic troughs and 6,5 times what power tower technology, respectively, would.  

 Shuman went right back to basics, the simple glass lined “hot box” that had been discovered more than a century earlier by de Saussure in 1767. More recently(1904-1908), it was being developed by other inventors (Boyle and Willsie) to heat low-boiling fluids to drive engines to pump water for irrigation. At that time, all solar motors were focused on driving engines to pump water for irrigation, and generating electricity was not yet a priority.

Shuman turned to the hot box in a big way. After developing his first hot-box power plant in 1907, he made simple but important changes that eclipsed the huge, impractical sun motors of the day.     

Shuman added mirrors to either side of each hot box, and then arranged them into rows. Through each row of these collectors ran a metal pipe containing cold water.  Heated by the concentrated power from the sun, very hot water left each pipe and emptied into a main duct leading to a specially designed motor that run on low pressure steam.  After leaving the motor, a condenser converted the steam back into water that returned to the collectors.

Besides being a gifted inventor, Shuman was good at persuading investors to finance his experiments in solar technology. Many of them had already benefited handsomely from his other inventions, and were keen to make more money. Soon, he had attracted enough investors to tackle the building of what would be the largest solar power plant in the world, in Meadi, Egypt . 

The world’s largest solar power plant: 1913
“Solar power is now a fact and no longer in the “beautiful possibility”stage.  [It will have] a history something like aerial navigation. Up to twelve years ago it was a mere possibility and no practical man took it seriously.  The Wrights made an “actual record” flight and thereafter developments were more rapid.  We have made an “actual record” in sun power, and we hope for quick developments”(Ref.1;109).

Writing in February 1914, Frank Shuman had every reason to hope for quick developments by the world in adopting solar power. The Meadi plant was a spectacular success, having been built from scratch in Egypt. A critical change was the redesign of the solar concentrators by Prof. CV Boys, resulting in the trough-shaped solar collectors (also called concentrators or reflectors) that proved so efficient that they were used, albeit modernised seventy years later, as the basis of the SEGS plants.

Ever practical and aiming to keep costs down, Shuman had used construction materials that were readily obtainable in the industrialized world, even in Egypt in 1912, when the plant was built. Although the initial zinc pipes carrying the water later had to be replaced by cast iron, there were remarkably few other problems.

The collectors, all seven rows of them, could withstand gale force winds, and rested on reinforced concrete. The sections of silvered glass in each trough-shaped reflector were held in place by small brass springs that absorbed the stress of expansion and contraction due to temperature changes in the hot Egyptian sun. And a simple but effective system kept the collectors facing the sun as it moved across the sky, enabling them to use 40% of the available solar energy to generate more than 55 horsepower.  Excess hot water was stored in a large insulated tank, enabling the plant to operate 24 hours a day, and on overcast or rainy days.

The grand opening of the plant in July 1913 had gone well, very well.  And the European colonial powers of the day had been impressed. Lord Kitchener, then Consul-General of Egypt, had offered Shuman’s Sun Power company a 30 000 acre cotton plantation in the British Sudan on which to test solar-powered irrigation. And Germany had offered Shuman $ 200 000 to pay for a similar plant in what was then German Southwest Africa (now, Namibia). 

In February, 1914, Shuman was surely justified in thinking that solar power, like the aeroplanes that the Wright Brothers had first flown twelve years earlier, was about to take off in a big way. But five years later, Shuman was dead, the Meadi plant was in ruins, and solar power had crashed, instead of taking off. What had gone wrong?  Essentially, two words that even today affect the viability of solar power: war and oil.

The high price of cheap oil
“Gone was the driving force behind large-scale solar development.  Moreover, with the Germans in defeat and their African colonies taken over by the Allies, the promises made to the Sun Power Company were as worthless as the Deutschmarks offered it. And the British, too, had lost interest in solar power.  They began to turn towards a new form of energy to replace coal- oil” (Ref.1,111).

On 4 August 1914, Great Britain declared war on Germany, and Egypt, then a key British possession, also became involved. As millions of soldiers in Europe began to learn the horrors of trench warfare, a less known tragedy began: the world lost the chance Shuman had given it to implement solar power commercially. 

First, the engineers running the Meadi plant returned to their home countries to do war-related work. Frank Shuman too returned home. But he never returned to Meadi, because by the end of the war he was dead.  With him died the Sun Power company, and the driving force behind commercialising solar power.

Solar power just might have survived the chaos of World War One but for a three-letter word, oil. Specifically, the lure of cheap oil and gas to replace coal. And as oil, then cheap and plentiful from new discoveries, replaced coal in the years after World War One, solar power’s prospects dimmed. For it was in sun-drenched areas that most new discoveries of oil and gas were made; the same few areas where coal was very expensive to transport to, and solar power had been cost-effective to use. As mentioned in another article, after 1920, cheap natural gas effectively killed off the promising solar water heating industry in California, established there in 1892.

Oil and gas were soon discovered in Southern California, Iraq, Venezuela and Iran, and, in 1938, in Saudi Arabia. Oil prices basically remained low for years until another war, the Arab-Israeli Yom Kippur war of 1973, changed things. Suddenly, many Arab nations were no longer keen to supply the West with cheap oil, and oil prices increased[fourfold] from approximately $3.00/barrel (bbl) to $12.00/bbl.  And, in 1979, oil prices again increased sharply, to a level approaching $40.00/bbl.

It was only in 1978, nearly sixty years after Shuman’s death, that urgent attempts were made to resuscitate solar power. But, although these efforts resulted in SEGS, they still lacked the sustained commitment to produce a reliable solar power industry. And, like Shuman’s Meadi plant, the sudden availability of cheap oil was, nearly eighty years later, to destroy the company building the world’s largest solar power plant.

For a list of references, see the end of the next article.