I accidentally found this interesting discussion. I think that it started with someone wanting to burn wood and make electricity in the back yard and then the conversation drifted on to automobiles and trains. Almost all of the common themes came up in this discussion and thus it is worthwhile to address some of them first. Leno has done a lot to popularize steam vehicles. He is a car collector and thus, by definition, what he owns are historic steam vehicles, both Whites, Stanleys, and Dobles, that were designed at the turn of the last century and manufactured when cars were just starting. Thus it is a valuable service that Leno does to educate the public, however, one should not draw conclusions from 100+ year old technology.
People have been working on steam since that time and that is one of the reasons for my postings. Stanleys did not have a condenser. Whites and Dobles did. Thus what one sees is steam being exhausted into the atmosphere from the engine. All modern steam power plants have condensers. It is not a major invention to do so. There is discussion about the difficulty of controlling steam production when using solid fuel. That is true, it is difficult as the fire continues making heat even after combustion air is cut off, however there are a great many solutions to that problem. It is not a deal stopper. At the least, a sliding plate can protect the boiler/steam generator from heat while stopped at stoplights and vent the heat to the atmosphere. This will happen during only a small amount of time. Or, one can design a heat buffer that absorbs heat from the fire while slowing or stopped to be used while accelerating. That is exactly the principle of a hybrid car except energy is stored as electricity, a much more convulated and inefficient system than storing heat.
When discussing steam engines the subject of the Stirling Cycle always comes up as it is theoretically more thermally efficient; also purportedly safer. An efficient Stirling power plant uses exotic metals as the temperatures are 3,000 degrees F and there are not enough of those metals in the world to make enough Stirling engines to make a difference. Then, the working fluid is hydrogen at 5,000 psi and one may want to reflect on that subject before making claims about relative safety. Stirling engines are difficult to start and run at only one speed and have limited torque, making them further more impractical.
Mention was made about a condenser making a steam engine more efficient. That is true for a large power plant as a cold body of water helps with pulling a vacuum by condensing the steam. For practical purposes this is not going to make much of a difference in a small power plant or in a car. As an example the old coal fired locomotives ran at 6% thermal efficiency. That was because they needed to make a lot of power in a small volume, so much heat went up the smoke stack and because the railroads owned the coal mines so coal was so cheap as to disincentive quests for more thermal efficiency. Modern steam power plants for cars are already in the 20% range and with a lot of engineering development work can get to 30%. Also a lot of money.
It is true that Howard Hughes and Bill Lear worked on steam vehicles; each with their own eccentricities. It is a long story and one little known. They both used mono-tube steam generators and so making a light vehicular power plant did not make anything more liable to exploding. The vehicles started from cold in less than one minute. It is very easy to have either a pilot light burning to keep the equipment hot or to have a plug-in such as diesel trucks do in the winter to keep things hot until needed. Thus it is very easy to have instant start-up. These days with remote starting clickers, one can easily get the fire started while lacing up one’s shoes. Therefore the slight delay in starting can be overcome and it is not a deal breaker. Only bank robbers need instant getaway anyhow.
Always when steam power is discussed and such issues as explosions are discussed and then the wonders of Stirling engines there is the mention of a conspiracy of the oil moguls putting steam vehicles out of business. That topic is both a straw man and a red herring, besides being nonsense as steam power needs some fuel to make heat. Try to not spend too much time on that topic and instead spend it on developing a good modern steam power plant. We all need one. Tom Kimmel
Wood Burning Hybrid Steam Car discussion on Cosmo Quest Forums