I'm told the steam engine is the most mechanically efficient engine ever made

[enwar3]

I was at a science museum talking to one of the volunteers/employees there about the steam engine they had on display. It was a double action something something engine and it runs off the steam from evaporating water by burning something (oil, wood, etc.).

It seemed to me, and this was his thought too, that a steam engine would be an efficient alternative-fuel engine. I can't remember the statistics but somebody drove across the country using a steam engine for cents on the dollar or some ridiculous amount. The engine can reach speeds high enough for today's use, can accelerate and decelerate much faster than gasoline engines in cars today, and can burn something plentiful like kerosene.

He also told me the only reason the steam engine hasn't taken off is because 1. oil companies and 2. you have to carry fuel.

So is the steam engine a good idea? Or do I have some facts wrong?

 

[hanoverphist]

what about the emissions of whatever youre burning to get that steam? i bet a freeway full of wood burning cars would pollute way more than the current strategy.

 

[tasmanian]

Well steam engines are very dangerous. Also can you imagine getting in a wreck and having steam explode into your car, not fun.

 

[KB]

I am not sure about its efficiency, but I can tell you why steam engines aren't in cars - for the same reason we don't have nuclear powered cars - if the water level gets too low then BOOOMMMMM!

 

[SirStev0]

Originally posted by: tasmanian
Well steam engines are very dangerous. Also can you imagine getting in a wreck and having steam explode into your car, not fun.

 

[Lonyo]

We used to use steam engines on trains, then switched to diesel and then electric.
See a pattern?

 

[xanis]

Something has to be burned to heat the water and produce steam to power the car. If you use oil that kind of defeats the purpose of having a steam engine, doesn't it? Also, anything else would just weigh the car down... imagine lugging around coal or wood for your car.

 

[IronWing]

Steam engines are large and heavy. Also, the steam needs to be kept hot. Not very good for running around town where you drive five minutes, park twenty minutes, drive ten minutes, park five minutes. OTOH, imagine to sound of forty steam engine powered cars pulling away from a traffic light.

 

[LOFBenson]

Steam engines take very high heat and very high pressure to be efficient. Steam engines are far too dangerous for the average driver. It'd be like driving around with a scuba tank between your legs.

 

[DisgruntledVirus]

Uhhh 3 they are generally impractical for vehicles. Generally to get powerful enough engines they are bigger and heavier (due to having to hold high pressures they are very solid to say the least).

 

[SagaLore]

Because internal combustion engines are more compact, less dangerous, and more convenient to refuel. Steam engines are very large, can blow up under too much pressure, and require a constant supply of water for steam production. It also takes longer to build up the heat just to go anywhere.

 

[Baked]

Can you imagine shoveling coal into your glove compartment/furnace while driving?! Awesome!

 

[bobross419]

Couldn't you just store up methane... maybe by a clever adapter in your car seat and power it off of the burnt gas?

 

[JohnOfSheffield]

Originally posted by: JohnOfSheffield
It's not even close to the efficiency of a normal ICE.

The most effective motor to date is the electrical engines.

You could build yourself a CO engine burning wood and using the CO in a combustion motor with some adjustments, that would be more efficient than any steam engine.

Originally posted by: JohnOfSheffield
Hydrogen is a better alternative and it's been in production for a few years by now, we need better production methods and storage for it though.

The Hindenburg somehow still lingers in the minds of some idiots.

Everything I've read to date, isn't even close to what you said. You have any links to back up the efficiency of ICE versus Steam? Did you know that hydrogen has the least amount of energy capability than any other fuel alternative, creating major disadvantages in storing enough for it to be useful?

 

[JohnOfSheffield]

Originally posted by: bobross419
Couldn't you just store up methane... maybe by a clever adapter in your car seat and power it off of the burnt gas?

Hydrogen is a better alternative and it's been in production for a few years by now, we need better production methods and storage for it though.

The Hindenburg somehow still lingers in the minds of some idiots.

 

[Mark R]

Steam engines are hellishly inefficient. Even a medium sized static steam engine will only get around 15% efficiency - and massive steam engines (power stations) get mid 30s%. Higher efficiency power plants, use different technologies (e.g. supercritical water, or combined cycles).

One of the major determinants of efficiency is the temperature difference between hot and cold phases in the engine operation. Steam engines only operate on a narrow temperature differential - e.g. 150 C for steam and 50 C for the heatsink, which translates into a terrible efficiency. Internal combustion engines go from ambient air temp to peak combustion temperature (about 1000 C), allowing drastically improved efficency.

Internal combusion is so more more efficient there's no comparison. There is a reason why freight ships use internal combusion diesel engines, rather than any other technology - it's by far the most efficient propulsion technology available. You'd think liquid nat gas tankers might run gas turbine engines from the methane that boil-offs during the trip - Nope. Way too expensive. Those few tankers that did get built with turbine engines, are now being refitted with diesel engines because they're so much more efficient - even when the diesel engine has to power heavy cryo plant to condense the boiled off gas.

 

[CatchPhrase]

the cryengine 2 is not that bad

 

[FlashG]

Nuclear powered boats, subs and power plants are steam powered generators. The only problem is that steam boilers don?t scale down efficiently.

 

[JohnOfSheffield]

Originally posted by: FlashG
Nuclear powered boats, subs and power plants are steam powered generators. The only problem is that steam boilers don?t scale down efficiently.

They don't even scale UP efficiently.

They work because the energy input is great enough to allow them to work but they are in no way efficient.

A direct power output from nuclear power to electricity would mean the end to all dependancy to foreign oil in every nation that has a nuclear power plant.

 

[Lonyo]

Originally posted by: FlashG
Nuclear powered boats, subs and power plants are steam powered generators. The only problem is that steam boilers don?t scale down efficiently.

But do we have any other way of utilising nuclear energy apart from using it to produce steam which then produces power?
IOW, do we make nuclear generators steam due to efficiency, or out of necessity?

 

[geno]

Watch this to see why living with a steam engine won't work for everyday use. It takes too much prep time to get up and running.

This is also a great vid for anyone who's unfamiliar with steam engines.

 

[91TTZ]

Originally posted by: enwar3
The engine can reach speeds high enough for today's use, can accelerate and decelerate much faster than gasoline engines in cars today, and can burn something plentiful like kerosene.

He also told me the only reason the steam engine hasn't taken off is because 1. oil companies and 2. you have to carry fuel.

So is the steam engine a good idea? Or do I have some facts wrong?

You have some facts wrong. They do not put out much power compared to gasoline engines of the same size and they don't accelerate and decelerate nearly as fast as gasoline engines.

 

[Mark R]

Originally posted by: Lonyo
But do we have any other way of utilising nuclear energy apart from using it to produce steam which then produces power?
IOW, do we make nuclear generators steam due to efficiency, or out of necessity?

Nuclear power via steam generation is done for practicality.

Most reactors use a water cooled core which is used to produce steam. For reasons of material strength and corrosion, the maximum temperatures are limited - as a result, steam is the simplest way of using the heat.

Some nuclear plants, notably those in the UK, use gas cooled reactors. These are able to operate at a much higher temperature, although even in those reactors, the hot gas is used to produce steam (albeit much hotter steam). The old 1970s UK AGR reactors, have the highest thermal efficiency of all nuke plants - about 39% compared the 36% for the latest designs under construction.

However, in that case, steam was used for convenience - there is considerable experience in designing, building and operating steam plants, and that was more important than any marginal gain in efficiency.

However, future nuclear plant concepts are trying to do away with steam for a number of reasons - notably efficiency, reliability and safety. In order to boost efficiency further, you need higher temperatures and pressures, and you start running into problems with steam. There are 2 major new technologies being investigated:
1. Direct Brayton Turbines. This is basically a gas turbine, as would be used in a nat gas plant. Coolant gas is compressed, heated in the reactor, allowed to drive a turbine, cooled and recompressed. Use of extreme reactor temperatures, and multistage intercooled compressors and multistage regenerated turbines, should allow efficiencies much better than simple cycle gas turbine (aiming for 45% -50% or so). At the same time, corrosion issues are avoided - CO2 or He coolants are pretty inert (Steam is actually a real bitch on turbine blades). Additionally, there is no liquid phase. With water/steam cycles, a steam leak or other failure can result in flash boiling of the water and a steam explosion - in a pure gas system, there is far less energy available for explosive release.

2. Supercritical water. At extreme pressures and temperatures, steam becomes so dense, and water becomes so volatile, that the 2 become indistinguishable and just called 'supercritical water'. The much higher temperatures and pressures allow better efficiency than simple steam, and because you don't have separate water and steam, you drastically simplify the plant - no need for complex steam generators, condensors, steam driers, complex multi-stage, multi-pressure turbines, etc. You simply have reactor, turbine, heatsink, pump. The enormous energy density of SCW means that turbines can be a fraction of the size of steam turbines.
SCW is widely used in the latest generation of coal plants, where it gives efficiency of about 45%. The biggest problem is that SCW is wickedly corrosive, and very special pipe and turbine materials are needed in coal plants. Considerable research is still required to find materials that are both nuclear and SCW compatible.

 

[marvdmartian]

....and let's not forget the soon to appear Mr Fusion device!

 

[JDub02]

Originally posted by: Lonyo

Originally posted by: FlashG
Nuclear powered boats, subs and power plants are steam powered generators. The only problem is that steam boilers don?t scale down efficiently.

But do we have any other way of utilising nuclear energy apart from using it to produce steam which then produces power?
IOW, do we make nuclear generators steam due to efficiency, or out of necessity?

In a pressurized water reactor (PWR), the steam process is very efficient. The turbines are something like 97% efficient. The problem is nuclear->steam conversion. That's around 30% efficient or so. Alot of neutrons are lost without fissioning. And when they do smack into something to cause fission (and heat), alot of heat is lost before it can be converted in the steam generators.