An engineer goes back in time to attempt to rewrite history: since global warming has wiped out all but a few living species at his home timeline, he wants to prevent it without preventing an industrial revolution.

To do this he plans to introduce photovoltaic cells, light bulbs and dc motors early as an inventor.

What resources and processes would he need to educate people about?

Side note: I already figured out how to explain the time travel and how things are gonna go south.

  • $\begingroup$ I am not sure one can answer a time travel question with hard science. Anyway, I gave it a try. $\endgroup$ – L.Dutch May 11 '19 at 9:21
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    $\begingroup$ Are you sure about the hard science tag? That makes this a tricky question to answer as there aren’t many academic papers that can easily be turned to an answer. $\endgroup$ – Joe Bloggs May 11 '19 at 9:22
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    $\begingroup$ Is the starting point the future? The reason I ask is that in theory dye-sensitized solar cells might be better fit for you but our current technology for them is not good enough. If your starting point is few decades in the future and you are already assuming a time machine, a version that can be built from materials available pre-industrial might be available. He might even have gene-engineered bacteria that produces the electrolytes, dyes, and catalysts needed. $\endgroup$ – Ville Niemi May 11 '19 at 9:37
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    $\begingroup$ Wait... you want to solve global warming by moving the Industrial Revolution back to the Renaissance (exactly what year is that?) People seem to forget that solar panels aren't magic. They must be manufactured and that requires the industrial base. There are more kinds of global-warming/hurt-the-earth kinds of waste than just coal smoke. $\endgroup$ – JBH May 11 '19 at 15:20
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    $\begingroup$ Also, the technology pyramid is massive. Any one advancement stands atop millennia of scientific discovery, experience, innovation, experimentation, etc. in many different disciplines. You can't send one guy back with all the info he'd need to do this. He couldn't make that much of a change in lifetimes. You need factories to build the solar panels, to build the solar cells themselves, to build those factories, right down to factories to build screwdrivers and hammers. The industrial base is huge. $\endgroup$ – JBH May 11 '19 at 15:31

I am afraid your plan is bound to fail.

What you need to teach:

Chemistry and chemical engineering

You will need to teach them how to extract and purify the elements you need: silicon and its dopants, the various metals and all the materials needed to process them.

You will also need to invent the Czochralski process

The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors. [...] The most important application may be the growth of large cylindrical ingots, or boules, of single crystal silicon used in the electronics industry to make semiconductor devices like integrated circuits.


If you want to grow monocrystals, you need an automated way to control the process. This means electronic and computers.


You need to find the places where the ores can be extracted. Silicon and its dopants don't grow on trees.

Mind that just for smelting silicon you need to take it at 1425 C. That means an awful lot of energy, plus the one needed to power the entire production line and related control.

And since you don't have any "green" source, guess what you have to use? Yes, coal/wood. This means that you will have to teach them also mining engineering, but since they will have a bonanza of easily accessible coal, why would they bother chasing your dream of solar energy, with all the hassle it bears along?

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    $\begingroup$ @Yanis: See, this is a good answer, but it’s science based instead of hard science as there’s never been a study done on the potential of Renaissance scholars to dope silicon... I +1’d it, because I think it’s right, but it’s really hard to back this up with academic references. $\endgroup$ – Joe Bloggs May 11 '19 at 9:27
  • $\begingroup$ Solar furnaces have been around since Archimedes' time. 1425 C is nothing. $\endgroup$ – nzaman May 11 '19 at 13:22
  • $\begingroup$ @nzaman, from the very same link you provide: An experiment to test this theory was carried out by a group at the Massachusetts Institute of Technology in 2005. It concluded that although the theory was sound for stationary objects, the mirrors would not likely have been able to concentrate sufficient solar energy to set a ship on fire under battle conditions. $\endgroup$ – L.Dutch May 11 '19 at 13:29
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    $\begingroup$ @nzaman, also, it's not enough so simply be "that hot" (I'm an EE with fabrication experience). You must have incredibly well controlled temperatures - and pressure, and contaminant filtration, and photo lithography (optics to micron clarity!), and electron beam tech, and a thousand more frankly unbelievable things. $\endgroup$ – JBH May 11 '19 at 15:25
  • $\begingroup$ @L.Dutch The issue was getting high enough temperatures to melt pure silicon. I pointed out that that is doable using a solar furnace, as the target is essentially immobile. Do note that I wasn't planning on sinking any ships with it, so whether Archimedes was a poor shot at moving targets is immaterial. He possibly simply had a target ship at a fixed mooring, which he sank as a warning to the Roman ships.@JBH Doping comes afterwards, and wasn't addressed as part of the thermal issue above $\endgroup$ – nzaman May 11 '19 at 16:14

Wind turbines might be a better idea than photovoltaic cells - they require less chemical ability.

Storing electricity will be a greater issue. The first practical rechargable battery was the lead-acid battery, invented in 1859, but it should be possible to reproduce it with Renaissance chemistry. Lead-acid batteries were used in the late 19th century for electric cars, and a smart guy from the future should be able to built one a lot earlier.

Light bulbs should be fairly easy to reproduce, as well, once you know to use a tungsten filament and filling the bulb with an inert gas like argon or nitrogen. Early light bulbs used carbon filaments like bamboo, which might be easier to obtain than tungsten.


Because of hard science tag I would say they he would ditch the photovoltaic cells as they are too hard to make without tools like computers and technology developed in early XX century.

So the process he would need to introduce it to how to make long lasting, with high capacity, energy cells. There were XIX century electric cars. The problem with them was that a canister of fuel could sit for months and be usable in an engine while energy cell in the E-carriage was good for days (weeks if properly stored). If he introduced that WAY ahead of gasoline engine he would get the upper hand of availability and maintenance that could compete with price of gasoline engine.
Lightbulb wouldn't change much (in term of slowing down the CC) it could rather speed up the need to create more cheap sources of electricy to power that bulbs. You need to keep in mind that Lightbulb is described as one of the pillars of Industrial Revolution as it allowed working 24 hours in well light places to work on products created by lathes.

So the point would be to show the potential of harness the free energy of nature. Wind and water. Electric generators were known as a curiosity in ancient Greece (you take wool, you take amber, stick one on a small wheel that smudge the other and tunr it to create sparkling thing.

Now to the point - Processes and resources he would need are - materials and smithing industry capable of creating long wires of various diameter to create coils for generators/engines, relay stations and amp.
So good quality cooper and aluminium sources, some kind of dielectric coating. For the magnets he would either need to introduce and "discover" nickel and cobalt or craete way of using electromagnets from iron core and copper wiring.


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