What drove James Watt to design the steam engine?

[CC]

I believe that there are many theories and explanations as to the causes of the industrial revolution. These posit economic, geographic and social circumstances that were precursors of the social changes we call the IR. But I can’t find anything that explains the motivation behind, for instance, Watt’s invention, aside from what appears to be natural curiousity and personal drive. Put another way, I don’t find anything (in an admittedly small and limited search from here) that provides insight into Watt’s REASONS for working on this machine. The machine is often cited as the real beginning of the IR, and conditions were right for it to appear. But what did Watt think? Did he see development of the steam engine as a significant event?

[yabob]

Watt didn’t actually invent the steam engine, he made significant improvements on an existing design (the Newcomen engine). Newcomen was interested in pumping water out of mines to keep them from flooding.

[yabob]

Note that Newcomen’s engine was in use commercially - he can be credited with coming up with the first practical steam engine for industrial use. Watt’s improved design replaced it, and made more uses possible.

[Lemur866]

The original purpose of the steam engine was to pump water out of the coal mines. The coal would then be sold. The advantage was that the steam engine would run on coal from the very same mine. The original market for coal was for heat, it was only later that the coal would be sold to be burned in other steam engines in factories, and transported via coal-burning steam locomotives and such.

[ElvisL1ves]

Its purpose was to stimulate the creation of the discipline of thermodynamics, in an attempt to explain how it worked.

Well, that wasn’t the purpose really, but it was an effect anyway.

[Colophon]

<blackadder>
“A fellow called George Stephenson has invented a moving kettle… wants someone to help with the marketing…”
</blackadder>

[CalMeacham]

What drove Watt to improve the Newcomen Engine was engineering geekiness – he was a lecture demonstrator who observed the inefficiencies of the Newcomen engine (it paradoxically required the cylinder to be both hot and cold – hot to keep the steam from condensing when you didn’t want it, cold to condense it at the end of the cycle). He was helped enormously by improvements in mechanical shaping of parts that allowed much tighter tolerances, without which Watt’s ideas might not have worked so well.
I learned all this from James Burke’s books. But you can read it on Wikipedia, too:

Four years after opening his shop, Watt began to experiment with steam after his friend, Professor John Robison, called his attention to it. At this point Watt had still never seen an operating steam engine, but he tried constructing a model. It failed to work satisfactorily, but he continued his experiments and began to read everything about it he could. He independently discovered the importance of latent heat in understanding the engine, which, unknown to him, Black had famously discovered some years before. He learned that the University owned a model Newcomen engine, but it was in London for repairs. Watt got the university to have it returned, and he made the repairs in 1763. It too just barely worked, and after much experimentation he showed that about 80% of the heat of the steam was consumed in heating the cylinder, because the steam in it was condensed by an injected stream of cold water. His critical insight, to cause the steam to condense in a separate chamber apart from the piston, and to maintain the temperature of the cylinder at the same temperature as the injected steam, came finally in 1765 and he soon had a working model.

James Watt

[Sage_Rat]

A somewhat more pertinent answer to the question:

@Wikipedia

Now came a long struggle to produce a full-scale engine. This required more capital, some of which came from Black. More substantial backing came from John Roebuck, the founder of the celebrated Carron Iron Works, near Falkirk, with whom he now formed a partnership. But the principal difficulty was in machining the piston and cylinder. Iron workers of the day were more like blacksmiths than machinists, so the results left much to be desired. Much capital was spent in pursuing the ground-breaking patent, which in those days required an act of parliament. Strapped for resources, Watt was forced to take up employment as a surveyor for eight years. Roebuck went bankrupt, and Matthew Boulton, who owned the Soho foundry works near Birmingham, acquired his patent rights. Watt and Boulton formed a hugely successful partnership (Boulton & Watt), which lasted for the next twenty-five years.

(bolding added)

1. Advance technology
2. Get it patented
3. Sell products
4. Profit!

Step 4 is of course the big one.