The Roots of Progress

James Watt's steam engine

April 8, 2017

The Newcomen engine was a great invention, but it was inefficient.

As I mentioned in the previous post, the engine works by letting steam into a chamber, then spraying a bit of cold water into the chamber to condense the steam, creating a vacuum.

My understanding of this is rough, but I think the main inefficiency is that in this process the chamber is being repeatedly heated and cooled—one cycle of that for each stroke of the piston. The repeated heating and cooling wastes a lot of energy and consumes a lot of fuel.

Further, the machine is losing heat proportional to the surface area of the chamber, but generating power proportional to the volume, so the way to make it decently efficient was to make it large. So Newcomen engines were generally big and heavy. They were stationary, in fact I think they generally had a small house/shed constructed to house them on one spot.

If the steam engine had stopped there, we would never have gotten trains or steamships, let alone automobiles.

Enter James Watt. Watt’s key innovation was a separate condenser. Again, my understanding here is rough, but basically there were two chambers—a hot one and a cold one. The water/steam cycled through them. This greatly improved the efficiency of the engine and allowed it to be made smaller and lighter.

It was with Watt’s engine, I believe, that the use of steam power really took off.