2
$\begingroup$

I was looking into the Dobles of years past after watching videos of Jay Leno's Doble E-20 and was trying to imagine how one could make the steam car a viable competitor to EVs and obviously one of the problems is the pollution from coal or wood being used for the fire.

Well what if the boiler contained electric heating elements at the bottom of the tank (much like a stovetop), that were powered by a large reserve battery? Once the heating element superheated the water and steam began being produced there could be some sort of generator/alternator built in somewhere to convert some of the unused steam into electricity to recharge the battery, for self-renewing green energy.

Would this be feasible in a Doble-like application?

I am not planning on trying this, but I am interested in if it is possible.

My first concern is that heating elements may not be able to sufficiently heat the water or at least not in a timely manner. Unless maybe it was a series of stacked elements.

$\endgroup$
  • $\begingroup$ Welcome @Blake to World Building SE! Please take a visit to our tour, it only takes a minute! $\endgroup$ – Ender Look Sep 5 '18 at 22:10
  • 5
    $\begingroup$ What you describe sounds a lot like a perpetual motion machine. Regardless, if you are using steam, you are using a heat-engine, so you'll find that they suffer terribly from the losses associated with all heat-engines. It's going to be hard to keep up with a vehicle that doesn't have such limits. $\endgroup$ – Cort Ammon Sep 5 '18 at 22:32
  • 1
    $\begingroup$ Pardon me for asking, I'm not really familiar with steam engines, but does this relate to Worldbuilding as defined in the help menu? worldbuilding.stackexchange.com/help/on-topic $\endgroup$ – John Locke Sep 5 '18 at 22:35
  • 12
    $\begingroup$ Efficiency of using the battery to power an electric motor: about 75% to 85%. Efficiency of using the battery to boil water to make steam to push a piston: about 5%. Of course you can build an electric boiler; but using the same battery to power an electric motor will increase the efficiency fifteenfold, that is, it will give you 15 times more range. $\endgroup$ – AlexP Sep 5 '18 at 22:37
  • 4
    $\begingroup$ This is a bit like programming a robot to use a pocket calculator. Sure it's possible, it's actually super easy, you've just reinvented the electric stove. But it doesn't make a lot of sense. Btw, I'm ignoring your magical green energy because others have already addressed that issue $\endgroup$ – Raditz_35 Sep 6 '18 at 9:06
24
$\begingroup$

This wouldn't work, sorry.

What you are describing is a perpetual motion engine which violate the laws of thermodynamics and are impossible to build.

Basically you use electricity to heat the water, then use the water to generate electricity...but you lose energy at each step. Each time around the cycle you get less electricity, then less heat, then less electricity, etc until you run out. The rest escapes into the environment.

$\endgroup$
  • $\begingroup$ Nice, straight to the point answer. What if the vehicle in question was fitted with solar panels, and kinetic generators to absorb braking energy. And possibly even some small, pinwheel like wind turbines mounted to the body that will be turned with the car's motion? It would no doubt look goofy, but I suspect that would still not supply sufficient energy to keep the energy from spiraling down. $\endgroup$ – Blake Sep 6 '18 at 13:46
  • 2
    $\begingroup$ No matter what you do, you cannot create energy from nothing. Solar panels would help, and if you had enough you could power the car entirely from the solar panels (since the energy is not coming from the motion of the car, but instead coming from the sun). Kinetic generators would help, but cannot generate more energy during braking than it took to get the car moving in the first place. Those are only useful since you are wasting the energy by braking anyway. The wind turbines would not work as you lose more energy overcoming the increased air resistance than you gain from the wind turbine. $\endgroup$ – Steven Lowes Sep 6 '18 at 14:08
  • 3
    $\begingroup$ @Blake, Powering the car directly from the electricity is still a lot more efficient. $\endgroup$ – computercarguy Sep 6 '18 at 14:09
  • 1
    $\begingroup$ What Steven and computercarguy said :) Yes you can power a car using solar panels, but then you're using the solar panels to inject more energy...and it would still be more efficient to just use them to drive electric motors. $\endgroup$ – Tim B Sep 6 '18 at 15:09
  • $\begingroup$ Makes sense, thanks for the answers $\endgroup$ – Blake Sep 6 '18 at 20:12
11
$\begingroup$

No. It wouldn't be feasible as a competitor to Electronic Vehicles (EV)s, ever.

Normal EVs generally boil down to a battery and an electromotor. Electromotors are, in general, fairly simple — and most importantly, cheap — to make. The only thing you need for electromotor is basically some wire that you coil around an iron core. There's no special requirements, you could make one in your garage. In their most basic form, EVs are also simple to maintain, as there's not much things that could break.

Steam engine? There's the heater, there's the boiler, there's plenty of moving parts that could break, and to top things off: everything needs to be able to withstand high steam pressure. It's a fair bit more complex and expensive to make and to maintain, so feasibility already falls apart here.

That's not the only thing that makes electrically-powered steam engines uncompetitive with EVs. No matter how many heating elements you use, heating water sufficiently will take time. Even if you could heat up the water sufficiently in under 5 minutes (judging by my electric kettle, that's extremely unlikely), even those 5 minutes is far too long when the alternative is "press the pedal and go." Furthermore, steam cars require water. Standard EV doesn't.

And of course, last but not least, time to consider the efficiency. Electromotors are fairly efficient in converting electric energy into movement. Steam engines, on the other hand, are generally far less efficient at converting heat into energy. Back when steam locomotives were still relevant, the efficiency of a steam engine was 7-8%. This probably doesn't include the significant amount of energy that's needed for re-heating water every time you refill your tank or start your car after it's been parked for a few hours.

Below the line: steam engine — especially the one where water is heated with electricity — has major disadvantages and no advantages over EVs. So: not feasible.

$\endgroup$
  • $\begingroup$ One more thing to add to your excellent answer is that to have the steam engine work you need to carry the water with you so to move the same amount of payload you need to move more mass, since you have to add the mass of water. In other words it's another factor reducing energetic efficiency. $\endgroup$ – Ister Sep 6 '18 at 11:34
  • $\begingroup$ @ister The tyranny of the rocket equation is well known. This is sort of the same thing. $\endgroup$ – Tonny Sep 6 '18 at 11:54
5
$\begingroup$

What you propose would technically work, though it wouldn't really add much (if any noticeable) power to the system. In fact something similar is already done:

Closed cycle steam engines feed back the steam into the boiler, that is so they need less replenishing of their water supply. The decrease of water consumption between an open to a closed system is in the ballpark of 90-95%.

To be fed back to the boiler, the water needs to be sufficiently cooled down. This is done using a condenser or similar. The mechanism used to cool down the steam can be, and mostly is, used to generate mechanical work - which is normally used to drive a fan or pump to keep the cycle in motion.

You could presumably make this step more efficient and so generate some power in the side. This power could sensible be used to e.g. drive the headlights of the car. This power is most definitely not useful to add any non-negligible amounts of heat to the boiler - electrical heating is very inefficient[citation needed].

$\endgroup$
  • 3
    $\begingroup$ If nobody beats me to the punch I will pepper the answer with links once I get on a real computer. Using a phone right now and adding links from the phone is really nauseating.. $\endgroup$ – dot_Sp0T Sep 5 '18 at 23:38
  • 1
    $\begingroup$ I'd add that electric motors are pretty efficient. More than steam ones, usually. $\endgroup$ – Mołot Sep 6 '18 at 0:35
  • 2
    $\begingroup$ Electrical heating is 100% efficient, it's using the heat that is inefficient compared to using the electricity directly. $\endgroup$ – immibis Sep 6 '18 at 1:18
4
$\begingroup$

As noted, this is a violation of the laws of Thermodynamics. The other factor which would make this infeasable (and is also related to thermodynamics) is the issue of where the electrical energy comes from in the first place?

A common critique of EV's is they are "Coal Powered" cars. This is a reference to the fact that a large portion of the base electrical power generation in the United States is from thermal generating stations powered by burning coal. In essence you are taking heat energy from the coal, turning it into electrical energy, storing the electrical energy in a battery and then using to drive the EV.

Your system adds extra inefficiencies by taking the high quality electrical energy and converting it to heat (the resistance wires in the boiler), then converting the heat energy to mechanical energy. The highest level of efficiency would be to reduce the number of steps in any process to a minimum.

As an alternative, you could also consider using the waste heat energy from a conventional internal combustion motor as a source of energy. This is often called a "bottoming cycle", and can provide a useful amount of extra energy to increase the overall efficiency of the system. In late WWII, several aircraft engines were converted to "Turbo-Compound" engines, where the exhaust gasses drove a turbine (much like a turbocharger), but the turbine was coupled via gearing to the crankshaft to provide extra motive power. SAAB-Scania and some other companies are reviving the principle for modern truck engines for use on the road.

BMW has also experimented with using the heat from the exhaust to power a boiler for a small steam engine, which can be used to drive the accessories, or as an extra source of motive power.

So your best bet is to either go directly for electric drive, or harvest the heat energy rejected from a conventional motor to provide auxiliary power.

$\endgroup$
4
$\begingroup$

Yes, but...

This is feasible, but it would be an immensely inefficient thing to do. Electric cars consist of a battery/inverter combo which works at around 90% combined efficiency, and an electromotor which, too, has an efficiency upwards of 90% for converting electricity to motion, and which can collect some energy back when you brake (unluckily, far from 90%, which would be awesome, but still better than nothing). So, all in all, for the complete system you're in the "80+" efficiency realm, plus anything you recollect while braking. With recharging from braking included, you might get better than 85%. That's not so bad, even with the shitty little batteries that we can build today.

A steam engine operates, depending on how awesome your steam engine building skills are, at an efficiency of around 20-30% (or 10% if your skills are not so awesome) with a hard cap of 63% given by the Carnot limit. So you instead of slightly less than a fifth, you throw away two thirds of your energy. That's really, really bad in comparison.

Regaining electric energy from unused steam would, too, throw away two thirds of the energy first, and then operate at the generator's efficiency on the remaining third. So, yes, you can regain some, but not nearly enough to be significant or competitive. Also note that after you gained back a part of the third that remains (which is already not much), you again throw away two thirds of that energy when you next use it to heat again.

$\endgroup$
0
$\begingroup$

The water would make the car quite heavy, especially compared to normal EVs. However, it gives you one option: you can heat the water while the car is parked via an external power source. The water will be in a pressure tank, so the boiling temperature will rise (and you can store more energy in the same amount of water). When you allow the water to cook (by opening the valve to the piston engine), it will (obviously) generate steam which will (obviously) power the engine.

Oh, well, just look here: https://en.wikipedia.org/wiki/Fireless_locomotive

Your addition of the battery would turn this concept into a kind of Hybrid. The electrical heating might be marketed as "fireless" (even though battery and heater will still be a fire hazard if something goes wrong). However, marketing would need be really, really good, as the disadvantages outweigh the advantages by far (see the other answers for that). The Wikipedia article mentions Hybrid Fireless Locomotives, but these used classic fire to provide additional heat. It also mentions "None has been a success."

Regular Fireless Locomotives are, however, still in use today.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.