# Could solar power be utilized and substitute coal in the 19th century?

Would it be possible for a nation with 19th century to very early 20th century technology and history and hot desert climate to utilize solar power for electrical generation as a substitute for coal or replace the use of coal in any other way?

There is not an abundance of national coal, however, rivers and ocean could allow for importation of coal.

• Not in the way you asked the question, absolutely not. If it wasn't done back then, it can't be done with 19th century technology, that would be a paradox. But I assume you dont mean literally 19th century technology but something else? Perhaps instead of asking this question, describe what you want to do first and then tell us the exact part, details are king here, that you are unsure about or don't know how to do. – Raditz_35 Mar 24 '19 at 21:17
• "If it wasn't done back then, it can't be done" it might or it might not be possible, but this alone is not enough to decide. Many things are possible but aren't done because cheaper alternatives exist. – vsz Mar 25 '19 at 7:17
• @Eth By that logic, isn't basically all energy from the sun in some way? Your point is interesting on its own but is not salient or relevant to this question in any way... – user91988 Mar 25 '19 at 17:20
• @AlexP: The first battery was actually created in 1794, so 19th century people could have stored the solar power to use at night. – Keven M Mar 25 '19 at 18:32
• That's getting into grammar and English though, or maybe alien theory. Who's to say that alien races don't coincidentally call their star Sol also? Besides, in any translation dictionary between Earth language and Alien language, whatever the alien word it would still translate into Sun or Earth in human language. Isn't semantics fun? 😋 – Keven M Mar 26 '19 at 14:05

Yes, they could. You "just" need a large mirror to concentrate sunlight on a boiler to produce the steam. Power plants that use this principle are in use today: Ivanpah Solar Power Facility

The first problem you have is with economy. Burning coal is just way too cheap if you have it available, and it's much easier to get a few megawatts of heat out of burning coal than it is to get the same amount of heat from mirrors. Simply because you need about one square meter of mirror for each kilowatt of sunlight you want to collect, and the mirror needs to be continuously adjusted to the sun. A single man shoveling coal into an engine produces much, much more than just a single kilowatt of heat...

You can offset the economy problem by making coal hard-to-get in your country.

However, the second problem remains: Efficiency. Early steam engines were brutally inefficient, turning only 1% or 2% (Watt's optimized version!) of the heat into actual mechanical work. So, if you have a giant 10x10 m mirror ($$100\ m^2$$), you only get 1 kW or 2 kW of usable power output. Anything that requires more energy than that quickly becomes infeasible to power with the many, enormous mirrors you need, which all require man-power to adjust to the sun continuously.

Of course, you can offset this by a) allowing close to modern steam turbines, and b) fancy clockworks that automagically adjust the mirrors. Nevertheless, it remains difficult to get the power from the power plants to where it's actually needed.

• Comments are not for extended discussion; this conversation about solar power at night, lights, other power needs, storing power, and more has been moved to chat. – Monica Cellio Mar 26 '19 at 2:00

If they have a lot of desert space, perhaps they could build solar updrift towers? It's basically a large area covered by a greenhouse roof and a high chimney in the middle. The energy output is proportional to the area times the chimney height.

They were invented in 1896, so they use only technology available at that time.

• Solar updraft towers were proposed in 1896 (and 1931, and the late 1400s, and probably many other times). In 1896, they could certainly build the tower, but the turbine to extract power from the air movement would need to wait until about the 1910s, when aerodynamic research started producing reasonably efficient propellers. – Mark Mar 25 '19 at 20:11

Egypt 1912

It actually happened:

Shuman built the world’s first solar thermal power station in Maadi, Egypt (1912-1913). Shuman’s plant used parabolic troughs to power a 60-70 horsepower engine that pumped 6,000 gallons of water per minute from the Nile River to adjacent cotton fields. His system included a number of technological improvements, including absorption plates with dual panes separated by a one-inch air space. Although the outbreak of World War I and the discovery of cheap oil in the 1930s discouraged the advancement of solar energy, Shuman’s vision and basic design were resurrected in the 1970s with a new wave of interest in solar thermal energy

https://en.wikipedia.org/wiki/Frank_Shuman

• I'd upvote this ten times if I could! – nigel222 Mar 26 '19 at 9:16
• They tried that setup again in the early noughties, it has the advantage of simplicity but there are better options now. – Separatrix Mar 26 '19 at 10:04

You can run a generator on an open-cycle hot air engine. This is a heat engine that gets energy from the expansion of air when it heats up.

The major issue is getting cold intake air. You can use a ground-coupled heat exchanger for that. Specifically a thermal labyrinth. The air is drawn thru a long path underground and cools in the process, basically.

Heating up the air is depressingly simple in a desert. Just have some some structure made of metal above ground where sun can shine on it and it can change heat with the local air. If you have mirrors you can focus the sunlight for much higher temperatures. Solar cooking ovens are a thing so the mirror and design wouldn't need to be that good. For a more serious design you can use a parabolic through.

For the viability of all this the best comparison is probably ocean thermal energy conversion.

The very good news is that the conception and early tests are pretty much in the desired time frame, so somebody coming up with the idea of adapting it to a desert would be viable. Thermal labyrinths are ancient technology and heat engines were largely invented during the 19th century, so that all works as well.

The good news is that OTEC has been tested and it does actually work, so the desert version would probably as well. How well is bit hard to say since the working fluids and many other details differ. The differences kind of balance out but you'd have to do actual numbers to know how well and that would require an actual design. Maybe an actual physical experiment at significant scale even.

The bad news is that OTEC never has made a breakthrough. It never really succeeded in competing with coal and oil. And the desert version would probably be more problematic. While this proposal basically uses the entire desert for capturing the solar energy and so solves some of the density problems of other types of solar power, it still cannot compete with coal on density and thermal labyrinth would be more upfront work than pumping up cold sea water as in OTEC. So the economic potential would be limited.

That said in this time frame cheap labor might be more accessible than imported fuels. Or the government might simply worry about being dependent on imported coal in case of a war. Or about maintaining the logistics of transporting the fuel.

And there are uses other than electricity where this might work better. This system already pumps both cold and hot air, so it would only need some valves and thermostats to give you a self powered air conditioning system. In a hot desert that is not nothing.

Likewise something like irrigation by pumping up ground water would be better fit than electricity generation. A farmer might be happier with spending time to build a thermal labyrinth than with spending money to buy coal or oil and intermittent and low density works fine for irrigation.

So the actual answer would be split. Utilize, yes. Replace coal, no.

• OTEC has never made a breakthrough because it's trying to extract energy from an extremely diffuse heat source with a very low temperature gradient. It might be possible with modern technology. With the lower efficiency of 1800s technology, there's not a chance it would work. – Mark Mar 25 '19 at 20:16
• @Mark It has been possible since the beginning, competitive with coal (or oil or nuclear or solar or wind or...) not so much. The problem is not being able to produce energy, it is being able to produce energy cheap enough to be of any value. That is where the low gradient really hurts as it directly cuts down watts per dollar. But you are right about 1880s. First OTEC mentioned that produced energy was from 1930. So this would definitely be early 1900s option. Or probably, there is no mention of anyone trying before either. – Ville Niemi Mar 26 '19 at 6:57

No. Coal works as power source because it is solar energy, concentrated, in a convenient form (rocks). Solar power is simply too disperse to be a power source to early, inefficient, steam machines

• In steel smelting we still haven't managed to replace coal, and it will take a while until we can do so at scale. The technology is known for quite some time, yet at industrial scale, you can't beat coal respectively coke when it comes to steel production. – Dohn Joe Mar 25 '19 at 16:47
• @DohnJoe: That's not just an energy thing as a chemistry thing. Steel is chiefly made from iron, but it contains a sizable amount of carbon from the coke. And the iron ore smelting needs to remove the oxygen from iron oxide, which is done by turning it into carbon oxide - again, with the carbon supplied by coal. – MSalters Mar 25 '19 at 16:51
• Yes, you can strip the oxygen from the iron ore using hydrogen, or provide the carbon by alternative sources, e.g. methane from natural gas. Yet, on industrial scale, coke is the dominant reduction agent. So, in the country the OP is building, steel, or the coal used for making steel, needs to be imported. – Dohn Joe Mar 25 '19 at 16:56
• For iron you can use charcoal. You need a lot less if your energy production uses solar already. Also, it's a (slowly) renewable resource. An added benefit would be some resistance to rusting. – Nyos Mar 25 '19 at 18:30
• Wood burning locomotives prove it was done. – Brian Drummond Mar 25 '19 at 21:06

A Frenchman named Augustan Mouchot demonstrated solar powered steam engines in 1866.

Augustin Mouchot taught secondary school mathematics from 1852-1871, during which time he embarked on a series of experiments in the conversion of solar energy into useful work. His proof-of-concept designs were so successful that he obtained support from the French government to pursue the research full-time. His work was inspired and informed by that of Horace-Bénédict de Saussure (who had constructed the first successful solar oven in 1767) and Claude Pouillet (who invented the Pyrheliometer in 1838).

Augustin Mouchot’s Solar Concentrator at the Universal Exhibition in Paris, 1878. (source)

Mouchot worked on his most ambitious device in the sunny conditions of French Algeria and brought it back for demonstration at the Universal Exhibition in Paris of 1878. There he won the Gold Medal, impressing the judges with the production of ice from the power of the sun.

Sadly for the inventor, coal was and is far cheaper especially since it can be burned 24/7 for power when you need it.

There is another viable alternative for coal which was in use during the 19th Century which you've already confirmed exists within your question; rivers.

Many machines of this period were powered by water wheels. If they have rivers and an ocean, there is no need to reinvent the wheel by creating some sort of elaborate solar powered system. This would meet the second part of your question; replace coal in some other way.

Your people could use wood gas.

https://en.wikipedia.org/wiki/Wood_gas

Wood gas is a syngas fuel which can be used as a fuel for furnaces, stoves and vehicles in place of gasoline, diesel or other fuels. During the production process biomass or other carbon-containing materials are gasified within the oxygen-limited environment of a wood gas generator to produce hydrogen and carbon monoxide. These gases can then be burnt as a fuel within an oxygen rich environment to produce carbon dioxide, water and heat.

Your people would be using solar power (as per OP) because they would grow crops to use as feedstock for the gasifier - maybe canary grass or tamarisks or whatever hardy plant they can grow in the harsh lands where they live. Or maybe they have ag waste from whatever they grow as food. Or river weeds.

Wood gasifiers are actually quite omnivorous - wood is fine and so is grass, rubber, dung, dead fish or anything with carbon in it. Anything you can do with natural gas you can do with wood gas.

• So should we be considering wind, water or bicycles/handcranks with this question? Wind is solar and humans and animals use chemical stores from possibly variable plants. – Echo61505 Mar 26 '19 at 0:24
• @Echo62505 - I like your hand cranks scheme but you could spruce it up some. Possibly hip cranks, powered by pelvic motions? Post it and you have my vote! – Willk Mar 26 '19 at 0:39

I'm not even going to try to compete with Chuck Ramirez's superbly researched answer, but nobody has yet mentioned the Stirling Engine which dates back to the early 1800s and was far more efficient than primitive steam turbines. It's also a perfect match to concentrated solar power: just use that to heat the "hot end".

The problems with tracking the sun using clockwork and cams mentioned in other answers would remain to be solved.

There was a company trying to develop Stirling engines mounted at the focus of parabolic dishes for direct generation of power (IIRC in the 1990s). There were problems getting the oil lubrication of the engine to work at all possible orientations, and then the whole concept got overtaken by solid-state solar panels. Although it might still be more efficient, area-for-area. Sterling engines can be over 40% efficient, a mirror better than 90%.

You already have some good ideas of things they could have used. Optics with big lens or mirror to boil water and connect steam engine to electric generator for example.

Modern solar power In terms of PhotoVoltaics (PV panels as we have on houses, camper vans et.c.) it would probably not have been possible as the photoelectric effect was understood just at start of 1900s. In fact in the very same famous paper that gave Einstein the Nobel prize.

• Solar panels use the photovoltaic effect (discovered in 1839) rather than the photoelectric effect (discovered in 1887). Still wouldn't work, because the materials for making a practical solar panel didn't become available until the 1950s. – Mark Mar 25 '19 at 23:22
• @Mark Yep. We needed semiconductors. That is a better point. – mathreadler Mar 26 '19 at 11:16