Can Solar Power Solve the Coal Problem?
A New York Times article discusses the need to transition from a coal-based economy to a solar energy future
I recently read a New York Times article on the coal problem. In the future, the article notes, we won’t be able to burn coal at our current rate, so there is an obvious need to make a transition to alternative sources of energy. According to the Times article, the most likely replacement for coal is solar energy.
Because most industrial economies currently depend heavily on coal, the Times notes that the economic effects of this transition will be perilous. On the bright side, the article cites recent “revolutionary” technical improvements in solar technology that will ease our transition to a solar future, noting that engineers have developed solar power plants that can produce over 7 watts per square foot of collector. “The new power is as exhaustless as the sun itself,” the Times gushed.
Oh — I forgot to check the newspaper’s date
Here’s the kicker: the article was published on September 10, 1868. That’s right — over 145 years ago. I came across the article by chance, when I entered the word “solar” into the search box on the New York Times web site, and then (on a whim) clicked “oldest to newest.”
The article (“The Coal Problem and Solar Engines”) is so interesting that I have reprinted a good chunk of it on this page (see the sidebar below).
“The Coal Problem and Solar Engines”
[Editor's note: The following article appeared in the September 10, 1868 issue of The New York Times.]
About two years ago, a very earnest discussion, as our readers will remember, sprang up in England on the prospective exhaustion of the coal-beds of Great Britain and Europe. Not only the scientific Press, but the literary and social — the Saturday Review, the Spectator, the Times, the magazines — took it up. Sir Wm. Armstrong and other scientific men attempted estimates of the duration of the present supply; Jevons, an English geologist, published an elaborate work on the subject; and Mr. Gladstone thought it of sufficient importance to discuss it at length, when Parliamentary attention had been directed upon it. If we reflect that the supply of coal governs also the working of iron, and how much in modern civilization depends on these substances, we can appreciate the importance of this controversy. Any considerable increase in the cost of producing coal, by reason of greater scarcity, would at once unsettle or ruin the commercial interests of the coal-producing country; and the national greatness of England, at least, has been largely due, thus far, to the proximity of her coal and iron.
This discussion, of course, at once gave rise to speculations on possible economy in the use of coal — a problem, however, as old as the invention of the steam engine. But it has been reserved for the distinguished engineer, Capt. Ericsson, to supply a new fuel in the place of coal, and a new motor in the place of steam. His device is as novel in conception as it promises to be astounding in result. In brief, his scheme is to collect and concentrate the radiating heat of the sun, and to use it for the production of motive power. He feeds his furnace, so to speak, from the sun. This motor he calls the Solar Engine.
The first public announcement of the success of this extraordinary device — for “solar engines,” kept in motion solely by the sun’s radiant heat, have been actually constructed by him and successfully operated — was made by Capt. Ericsson to the Swedish University of Lund, at its late centennial celebration. From his communication to that body it appears that for several years this engineer has been experimenting with the view of so concentrating the sun’s heat as to obtain from it a practical motive power. At length, at the beginning of the present year, he was able to construct three “solar engines,” of which the first was driven by steam formed by the concentration of the heat of the solar rays, and the other two by the expansion of atmospheric air, heated directly by concentrated radiant heat. … And, without going into the process, we may briefly say that Capt. Ericsson’s experiments show that the concentration of solar heat on ten feet square (or 100 square feet of surface) develops a power exceeding one horsepower. If, therefore, he adds, a Swedish square mile were covered with these solar engines, “64,800 engines, each of 100 horsepower” could be kept in motion by the radiant heat of the sun thus collected.
The audacity of this enterprise and the incalculable reach of its results are alike bewildering; but it is already, as we have said, a practical success, insomuch that Mr. Delamater, proprietor of the well-known Delamater iron-works, declares in a late scientific publication that “before the termination of the present season, bread will be prepared from flour ground by the power of the solar engine!”
The exact nature of the concentrating mechanism invented by Capt. Ericsson is not yet apparently made public; but the result, in general terms, is, as has been said, to collect a force equal to a horsepower from the sun’s heat on every 100 square feet of surface. To introduce a new motor into mechanism marks a new era in civilization. We call this the “age of steam” — but what shall we style the coming age? And, independent of the new force thus obtained, we must reflect on the economy effected in old forces. Not only will coal fields, whose capacity is now so anxiously discussed by political economists, receive an unexpected and all-potent ally, but in many ways the question of the cost of fuel would be affected — every economy in the use of coal for machinery leaving more for other purposes. Meanwhile, the new power is as exhaustless as the sun itself. It may be objected that this is not a “cloudy-day” force. If true, this would not be an important objection. But a brain great enough to master main results may be usually trusted to remove mechanical impediments in details. To store up fuel in the sky is a trifle to a man who makes his coal-pit of the sun.
There are many other obvious points for reflection connected with this extraordinary new motor. For example, the economy of cost in using the sun’s heat for fuel, the comparative ease of regulating the mechanism, compared with the management of steam machinery, which latter is an art in itself, and the safety of the apparatus. But all these will better appear when more is known of what promises to be a revolutionary agent in science, in industry, and in commerce.
The article’s predictions were prescient, and the challenges that the article identified are still with us.
We can’t keep burning coal at this rate forever
Back in 1868, scientists had an imperfect understanding of the connection between CO2 emissions and global warming. (Svante Arrhenius’s now-famous calculations — showing that doubling the CO2 concentration in the earth’s atmosphere would lead to an increase in surface temperatures of between 5 and 6 Celsius degrees — weren’t published until 1896, 28 years after this Times article was published.)
The “coal problem” referred to in the 1868 article was the worry that coal supplies would run out. The article cited warnings published by “Jevons, an English geologist,” who noted that coal supplies are finite. (William Stanley Jevons is best known as the eponymous originator of the mechanism known as the Jevons Paradox, whereby efficiency improvements lead to an increase rather than a decrease in energy consumption. Jevons outlined the features of the paradox in his 1865 book, The Coal Question.)
Unfortunately for our atmosphere, 19th-century worries over the finite nature of coal supplies were premature; in fact, the planet’s coal reserves are huge. To avoid the catastrophic effects of rapid climate change, we’ll either need to enact strict laws or develop the self-restraint to prevent us from burning all of the planet's accessible coal.
Solar energy can replace coal
These days, most educated Americans know that power plants can generate electricity from photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) arrays or from steam turbines fed by solar thermal collectors, and that solar energy plays an important role in our renewable-energy portfolio. But in 1868, only a few visionaries imagined that utility-scale solar power would ever be possible.
The Times article focused on solar thermal engines developed by a Swedish-American engineer named John Ericsson. In the 1860s, Ericsson developed at least three solar thermal engines, all of which used parabolic reflectors to focus solar energy. One of his inventions focused solar energy on a cylindrical boiler that produced enough steam to drive a steam engine. His two other devices focused solar energy on an empty cylinder, causing the air in the cylinder to expand and drive a piston.
The Times called Ericsson’s inventions “astounding,” and reported that Ericsson’s “scheme is to collect and concentrate the radiating heat of the sun, and to use it for the production of motive power. He feeds his furnace, so to speak, from the sun. This motor he calls the Solar Engine.”
The article reported that “Capt. Ericsson’s experiments show that the concentration of solar heat on ten feet square (or 100 square feet of surface) develops a power exceeding one horsepower.” Converting the units, this amounts to 7.6 watts per square foot. These days, photovoltaic modules do a little better than Ericcson’s inventions; in full sunlight, most PV arrays produce between 10 and 12 watts per square foot. (The Times article is unfortunately marred by an unresolved mathematical inconsistency, since it reports that one square mile of solar collectors could produce 178 watts per square foot — an output that is unlikely. Let’s assume that the math error was made by the Times reporter, not Ericsson.)
The article anticipated utility-scale solar plants
What is most remarkable about the reference to a square mile of solar collectors is not whether the predicted power output was accurate, but that such a bold prediction was made at all in 1868.
Solar thermal plants on the scale envisioned by John Ericsson are now a reality; for example, in October 2013, Abengoa Solar launched its 280-megawatt Solana solar thermal plant near Gila Bend, Arizona. The plant occupies 3 square miles and has a power output of about 10 watts per square foot. Like Erricson's solar thermal engines, the plant uses parabolic reflectors to heat liquid.
Ericsson also anticipated a day when solar panels would commonly be installed on rooftops. According to Let It Shine, a new book by John Perlin, Ericsson calculated that the usable amount of solar power “falling on the roofs of [the] houses of Philadelphia” equals 100,000 horsepower, or 74.6 megawatts.
What happens on cloudy days?
The specificity of the Times’ analysis was remarkable. The article not only provided an accurate prediction of the likely power output per square foot of future solar thermal plants; it also discussed the limitations of solar power. Anticipating naysayers’ skepticism, the Times story noted, “It may be objected that this is not a ‘cloudy-day’ force.”
While not ignoring the problem of solar storage, the Times article anticipated that the problem would eventually be solved. The article noted that the “cloudy-day” problem “would not be an important objection,” since “a brain great enough to master main results may be usually trusted to remove mechanical impediments in details. To store up fuel in the sky is a trifle to a man who makes his coal-pit of the sun.”
As it turns out, the recently opened Solana power plant has managed “to remove mechanical impediments” and “store up fuel” delivered from the sky. During the day, the plant heats up molten salt; at night, the hot salt is used to generate steam for the turbines.
The coal problem is still with us
The Times reporter who wrote “The Coal Problem and Solar Engines” in 1868 could not have imagined that in 2013, Americans would still be wrestling with the issues discussed in the article. More than a century later, we are still looking to solar energy as a necessary part of any solution to our ongoing coal problem.
Although it is remarkable that the predictions made in the 1868 article — that future solar thermal plants would cover more than a square mile, and that engineers would eventually solve solar’s “cloudy day” problem — have come true, some energy experts now predict that inexpensive PV modules will eventually make solar thermal plants obsolete. No matter which technology prevails in the end — PV or solar thermal — we are all in debt to John Ericsson for his pioneering work on solar thermal engines.
So — can solar power solve the coal problem?
Solar power is likely to be an essential component of our efforts to phase out coal burning. While the future of large solar thermal generating stations is uncertain, the use of PV is growing by leaps and bounds in almost every country in the world. Of course, solar energy can't directly replace coal, but buttressed by other sources of renewable energy, including wind energy and tidal energy, solar can be depended on to supply a large fraction of our future energy needs.
As astutely noted by the New York Times in 1868, the “cloudy day” problem is a significant challenge. Existing solutions to the problem are expensive, and it will be difficult (perhaps impossible) to satisfy 100% of our country's huge demand for baseload power with renewable sources of energy. As industrial economies struggle to make the transition from coal to renewable energy sources, one thing is clear: our biggest hurdles are political, not technical.
If we're willing to make the necessary investment, we can transition away from coal. All we need is the political will.
Martin Holladay’s previous blog: “Monitoring Moisture Levels in Double-Stud Walls.”
- M.W. Ridley (1871)
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