Alternative engines?

A question from Askville:

Are real viable alternatives to the combustion engine being paid off/covered up by the oil industry for obvious reasons?

No. And please define “viable”…

There are Wankel engines, but so far, only Mazda figured out how to make them so that they are reliable (and they still are not as fuel-efficient as piston engines; Mazda RX-8 burns 15-20% more gasoline than BMW 325).

There are Stirling engines (those are actually external combustion engines and were first implemented as steam engines), but they are not particularly useful for transportation applications, because they have to have a heater, which requires time to reach working temperature, so if you had a car with a Stirling engine, you could be looking at 10-15 minutes between the time you turn the engine on and the time the car is ready to move. They are great for small-scale power generation though, precisely because in this application they are always on.

There are steam and gas turbines, but they work best when they are large (thousands of horsepower) and operate at near-capacity. In the stop-and-go traffic, turbines suck (there were enough experiments with automotive and locomotive turbines in the 1960s to figure that out). Plus, they are usually supercritical (meaning, the operating RPM is above the critical RPM, which is the RPM that causes severe vibrations), so every time you start or stop a turbine, it goes through a severe shakeup. It’s not a big deal for a power station turbine, which is stopped for maintenance once or twice a year, but for a car, which you start/stop several times a day, it’s a killer.

There are fuel cells, but so far, only Honda figured out how to make a limited-release, sort-of-production car with them. Additionally, Honda’s car runs on hydrogen, which is still an exotic fuel, hard to store and transport (not to mention that most of commercially produced hydrogen is made from oil or natural gas). There are potentially interesting experiments where concentrated sunlight is used to break water down into hydrogen and oxygen (the chemists call it “photolysis”), but the chemical breakdown occurs at about 2,500°C (4,500°F), and there are currently no materials that could last at those temperatures.

There are fuel cells that run on natural gas, but those are still bulky; a company called FuelCell Energy makes a state-of-the-art 300 kilowatt (420 horsepower) power generator, which weighs 77,000 pounds and has a footprint of 28 by 20 feet.

There are alternative fuels, such as ethanol and biodiesel, but their environmental impact is uncertain; they burn no cleaner than gasoline, it takes energy to produce them, and, if produced on a large scale, they could greatly increase the need for irrigation water.

So you can see that there are many avenues that are currently being explored, but a major breakthrough in terms of developing an alternative engine and/or fuel fit for transportation has not yet occurred for reasons that have nothing to do with oil companies…

2 thoughts on “Alternative engines?

  1. Isaac

    There are also hydrogen internal combustion engines. How about using wind power to electrolyse water. You could perhaps think of hydrogen as a liquid battery – you use it to store the energy produced from wind power (or any other renewable source for that matter) and burn it to release that energy.

    I believe that hydrogen produces up to 10% more power than petrol (aka. gasoline), but I can’t remember where – Top Gear maybe?.

    We must stop using oil soon for 3 reasons:

    -It causes dependance on countries such as Iran and Russia
    -It causes climate change (an unarguable fact)
    -It will run out. No-one can be sure when, but it will.

    This leaves us with 2 choices:

    -Give up all the luxuries that oil gives us (not just cars – electricity, plastics, heating, to name a few)
    -Find alternatives to using oil.

    I think that the second option must be what we concentrate on (who could manage without electricity?). These energy sources are fast becoming viable, and hindrance from oil companies will not help this process of research.


  2. NC

    Internal combustion engines (including hydrogen-powered internal combustion engines) are much less efficient compared to hydrogen-powered fuel cells; if memory serves, NEDC (New European Driving Cycle) tests of cars powered by fuel cells show average tank-to-wheel efficiency of 36%, whereas conventional diesel-powered cars show about 22% (gasoline-powered cars are worse).

    The problem with thinking of hydrogen as a battery, however, is that it’s a “leaky” battery. At room temperature and atmospheric pressure, hydrogen is a light gas capable of escaping through smallest openings. At high pressures, this capability gets even worse; a tank perfectly capable of containing compressed air may leak if you try storing hydrogen in it. Since hydrogen is extremely flammable, this is a big problem. This is why some experimental car designers opt for storing hydrogen in a chemically bound form.

    As to using wind power to electrolyze water, there are two problems with it. One is storing hydrogen (see above). The other is that there simply isn’t enough usable wind energy in the world. Solar power is potentially more abundant, but so far it is more expensive…

Leave a Reply

Your email address will not be published. Required fields are marked *