Alternative & Renewable Energy Blog

The problem with steam is not steam itself, but how the steam is produced. Burning fossil fuels cause pollution. In a motor vehicle how will you generate steam without burning a fossil fuel? The most efficient means of driving a motor vehicle or locomotive is with an electric motor. You need a means of generating electricity. Steam won't do it because another fuel is needed to generate steam. The conversion from one means of energy to the final driving force has to be kept to a minimum as losses will quickly add up. Hydroelectric to electric motor is the shortest energy path. This is the ideal situation.

There is no question that fossil fuels will need to be burned, but the conditions under which that takes place will be completely different. In a compression engine, combustion takes place at high pressure and temperature, with a constant volume of gas in the cylinder. It is impossible for the fuel to completely combust, and the high temperatures also promote the creation of various other poisonous byproduct gases. But if you use a burner similar to one found in an oil furnace or gas stove, there is more than enough ambient oxygen to complete the combustion. I have heard that when a flame is blue, that is a near perfect conversion of the fuel to heat, carbon dioxide, and water vapor.

Also, I agree that hydroelectric, wind, and solar power are the future, but I am not convinced that there is enough raw material available to electrify every single car on the planet, so i am simply exploring other options.

Check out the Tesla turbine. Amazing efficiency, high power to weight ratio, and nearly indestructible.

Regards Dragon

mm, I love the design, but the gear reduction necessay to put the powerband in a usable range for, say, a car is just....scary. I'm not skilled enough to try to design a safe gearbox to handle those rpm's yet.

Just run the power output shaft through a reduction transmission and you can drop the speed to whatever you wish. The engine need only run at 3600 rpm to run a large alternator driving electric motors. The transmission is only for higher horsepower demands.

Regards Dragon

Old School - This is a very neat project you've started. I hope you can carry it through to a working prototype.

Are you thinking of an automotive application? If so have you given your thinking toward how to do the boiler to match it for that application?

Don't let the current enthusiasm for electric vehicles discourage you. You really don't know where this steam engine interest is going to take you.

Keep us posted........ Ed Weldon

Ever hear the song "Casey Jones"? Ever listen to the words? I am refering to the line, "Well they found him in the wreck with his hand on the throttle, scalded to death by the steam." Good luck and be careful...

You should take a look at the Doble Steam car firetube boilers from the 1920's. There was maybe a gallon of water being boiled at any given moment, and since it was contained inside pipes, and the pipes themselves were within a steel shell, if anything ruptured it would just kill the fire and exit through the exhaust. But yeah, your warning is duly noted, i intend to keep it very small scale and over-engineer the hell out of every part to reduce the risk of an explosion.

Old School - I haven't seen a comment yet on the subject of the boiler. I figure either that's not an issue at this point because you are well versed in that area and can readily plan for a boiler to fit your requirements when the time comes ....... or ...... This is an issue you figure you can learn about later.

In the event that your situation is the latter I'd suggest you explore the hobby world of live steam. Aside from the little steam powered toys that were popular among affluent families that could afford them 50-100 years ago and are collectors items today there is a subculture of hobbyists that build and operate live steam scale model locomotives of a size that can actually pull trains carrying real people. There is even a much smaller group that build and operate small pleasure boats that are steam powered. Google "live steam" and you will find many links to this world. Most builders of these things do all their own machining in their construction efforts and are full of tricks and techniques that should interest you as you are faced with turning your new ideas into real hardware. There are also available commercially built small auxiliary hardware such as safety valves, injectors, feed pumps, etc. that can save you a lot of work if your intention is to start with relatively small test models.

One thing you may want to know about is that within the live steam subculture there are a few competent builders of small boilers that are safe and certifiable (the laws on boiler licensing vary from state to state). They are mostly small one man shops so you must be prepared to do business with such a supplier. These folks have a pretty clear idea of what is needed without totally over designing the equipment for your application.

In the event that your interest is in the direction of an automotive application, even if just for testing purposes, there is a nascent interest in steam powered vehicles in the world of amateur land speed racing. There are two landspeed racing venues within a reasonable driving distance of New York state. One well established at Maxton NC. (East Coast Timing Association) The other is a group from New England that has run their first meet this year at the inactive Loring Air Force Base in Eastern Maine. I can envision a steam driven sidecar motorcycle with a propane fired boiler mounted in the sidecar. An engine of this size would lend itself to nice affordable dynamometer test setup for development.

Ed Weldon

Yeah, you basically hit it right on the nose. i haven't given alot of thought to the boile yet, because I am planning to finish a test vehicle first and use it as an evaluation platform for different boiler designs. Thanks for your information though, i will try looking into some of those things you mentioned. Its funny you mention that motorcycle idea, you'll see why in my later posts :-D

While people tend to concentrate their efforts on the boiler, the biggest limitation on automotive steam use is the condenser.

Because the steam in the condenser is at low pressure (below atmospheric), it's specific volume is high so large flow cross section is needed. This makes the condenser very bulky, and a potential hazard as any fracture will dump quantities of hot water/steam over everything and everyone.

When Howard Hughes tried his hand at a steam car in the 1930's the designers wound up incorporating bonnet, front radiator and doors as part of the condenser. Hughes immediately saw that if someone ran into him from the side, he would run a big risk of being badly scalded, so he killed the project.

This was one reason why steam locos rarely used condensers, but simply replaced the lost water when needed.

Because the boilers of the locos were usually stoked by hand, fire tube boilers were used to store steam when the stoker needed a rest.

Mono-tube boilers have little water as steam at any one time, the tube is a much better pressure vessel than the big boiler of the fire tube type and they can be cheaper to make and certify.

The choice of engine is not a difficult one.

Piston engines are robust and can be made so that only minor gear reduction is needed. There is a small sacrifice in efficiency because you cannot take full advantage of the steam expansion.

Turbines need big gear reductions but are efficient and light.

Unfortunately, inertia can be a problem, both from the turbine wheel and the gearbox.

One solution is to use the turbine to spin up a flywheel which in turn runs a generator, which drives an electric motor. This is not as inefficient as it sounds as the losses in most transmissions is quite high by the time the power gets to the wheels.

This arrangement allows you to remove the gearbox and recover braking energy.

I understand that condensers are usually designed, at least in power generation, to operate at pressures below atmospheric to increase the efficiency of the system and condense the water, but is this absoultely necessary? If the steam is allowed to fully expand and reach near-ambient pressure before entering the condenser, and a suction pump was provided to create water flow out of it, couldn't you basically repurpose an automotive radiator, assuming that it had a large enough surface area to condense most of the steam to liquid?

Agreed, you could run at atmospheric pressure with only minor efficiency loss.

Problem of the specific volume of steam still remains.

A car radiator circulates water at roughly 1 liter/kg. Steam at the same temp has about 1600 times this volume.(1.04341E-3 cu.m/kg for water, 1.67364 for steam). This means that you need about 1600 times the size "radiator" to use as a condenser.

In practice, you can allow much higher velocities of steam within the condenser, but it still needs to be very much bigger than for a water heat exchanger. (I'm not sure how much below the 1600x you can reduce it. My guess is that it could be workable at 10 to 30x, but that is only a guess. You will need to crunch the numbers).

The fundamental problem with steam power is wasted energy (heat). It takes a lot of heat to convert water from a liquid to steam at the same temperature, "latent heat of vaporization." The exhaust of the steam engine must be a gas, so if it exhausts to the atmosphere the steam carries off the latent heat of vaporization, wasting it. If you use a condenser, that heat can be recovered (used to warm a greenhouse, perhaps, and to preheat the water going to the boiler) and the engine can exhaust at lower pressure, getting more mechanical energy out of the steam. As noted, condensers aren't likely to be practical for wheeled vehicles, though they are standard on steamships.

While the idea is controversial, mixing air and steam may have merit. (US Patent 5,832,728, which has expired) If compressed air is mixed with the steam, as the air expands (in the cylinder or turbine) and cools, the steam condenses, reheating the air with the recovered heat of vaporization. The exhaust, instead of being hot steam, is air with droplets of condensed steam. Of course, some power would be tapped off to run the air compressor. Pumping hot compressed air into the boiler can help heat the water. In some cases, the fuel can be inside the boiler, oxidizing (O2 from the air) "wet". That's a whole other subject; it allows using (toxic) waste as fuel.

The steam electric drive for ships is not new. The original aircraft carriers Lexington and Saratoga (origianlly designed as battlecruisers) used steam turbines, generators, and electric motors to drive the propellers. Of course, while it worked well, we did not continue with that design.

Recently, a new land speed record for steam-powered cars (139.843 MPH) was set at Edwards AFB. The previous record dated from 1906, a Stanley Steamer (you could buy one at your local dealer) which went 127 MPH at Daytona Beach.

Vast sums were spent to raise the speed record about 10 per cent. This illustrates the old engineering maxim (attributed to Rutherford) that it is seldom advisable to spend a lot to get a small improvement in performance. There are three exceptions: fast horses, fast yachts, and fast women.