Dry-Ice Heat Engines For Martian Colonists

LeadSongDog writes: Heat engines using the "Leidenfrost effect" can exploit the gas expansion as CO2 sublimates to drive turbines. "The technique has exciting implications for working in extreme and alien environments, such as outer space, where it could be used to make long-term exploration and colonisation sustainable by using naturally occurring solid carbon dioxide as a resource rather than a waste product. If this could be realised, then future missions to Mars, such as those in the news recently, may not need to be ‘one-way’ after all.

Dry ice may not be abundant on Earth, but increasing evidence from NASA’s Mars Reconnaissance Orbiter (MRO) suggests it may be a naturally occurring resource on Mars as suggested by the seasonal appearance of gullies on the surface of the red planet. If utilised in a Leidenfrost-based engine dry-ice deposits could provide the means to create future power stations on the surface of Mars. " The research was published in Nature Communications, and one of the researchers published an explanatory article at The Conversation.

Comments

Energy costs of transport

[wierd_w]

I wonder over the costs of energy transport..

Let's say we have an industry on Mars, that is powered by dry ice evaporation turbines.

In the middle latitudes, dry ice is unstable on the marian surface. It sublimes, and turns into gas. This means that ambient temperatures there are able to turn the ice into useful energy.

Now, if these power plants shipped energy, in the form of electricity on power lines (burried, probably) to the polar region where dry ice can be efficiently mined, what is the feasibility in terms of energy cost for extraction and transport?

Energy

[itzly]

You still need energy to heat up the CO2. And if the energy is available in electric form, which is most likely, why not simply drive an electric motor instead ?

Re:Energy

[wierd_w]

less practical. Insolation is a tiny fraction of that of the earth. Conversely, the amount of expansion (and pressure) that heated dry ice turning into gas produces is very high, enabling high efficiency power generation.

The question is if the costs of harvesting and transporting the dry ice are sufficiently low to enable this as a viable solution.

"High Temperature" superconductors exist now that would be superconductive at the polar latitudes.

Re:Energy

[wierd_w]

Indeed, but as a "mature" energy infrastructure, it has many benefits that straight solar or nuclear simply dont have.

1) It's pretty damned low tech, meaning you need need the same amount of energy hungry industrial infrastructure to maintain or build it out.

2) Approx 40% of polar ice on mars is actually water ice, according to spectroscopic analysis from orbit. This means that the turbine generation process would leave behind pretty damned pure water ice in the turbine pressure generators. Useful for a colony.

3) The temperature difference between the polar region and the equitorial region is astounding. In the summer months, mars equator can reach up to 70F in the daytime. Conversely, the pole is -200F. There is also powerful day/night temperature variation at the equator that a heat-engine could capitalize on. Even in the summer, when the daylight surface temp can possibly reach 70F, the night time temperature drops to -150F rapidly. This means that simple mirror concentrators and molten salt tech could be used to drive INSANELY efficient stirling power generators at night.