Anybody know anything about Solar or Geothermal energy?

AirTech wrote:[
Nuclear power in mobile systems is possible - just not small ones (40kW (55Hp) seems to be as small as anyone got to work, and that was a hot water service (Canadian toy...).

That wasn't a toy, that was to make tea and coffee....

Zakharra wrote: Excepting wood and coal, which are more inefficient than oil, I don't see any fuel there could be to make heat for a moving (truck/ship) vehicle.

Oil also has the advantage of high energy density. We (at present) see some possibilities for high energy density batteries (lithium-air, fuel cells) which mainly use air as one reactant, thus reducing vehicle weight, but at present have no way of getting high enough energy density. Electric vehicles can easily have high power density - search on (electric AND "drag racer") but it doesn't last that long. Charging times are high also, but that is secondary.

There is a possibility the new single carbon layer material (name forgotten) will help with one or both. The technology for small amounts is easy - they used graphite and tape to peel off the first single layers. At present they can make much larger ones, but I've no information on the difficulty level. However, this is all still experimental.

There is a good chance Weird Harold is right, and it will be possible to skip steps. But at this time we don't know WHICH steps can be skipped with 24th century tech. Look how many nations are going directly to cell phones, instead of setting up land line grids. But he also may be wrong, and if so, it is likely because the basic tech needed has too many situations where you need to make the tools to make the tools to make the tools. Technology needs infrastructure. Which is one reason our back yard is mostly garden - low technology intensive gardening has been developed, search on (intensive gardening) and we can raise much locally with only a few hours a day. Hey, it gets me outside in good weather Farms still use automation for grains and others that can be easily machine harvested.

""how hot would you like your coffee?


" In degrees, or sieverts?

Keith_w wrote:

AirTech wrote:[
Nuclear power in mobile systems is possible - just not small ones (40kW (55Hp) seems to be as small as anyone got to work, and that was a hot water service (Canadian toy...).

That wasn't a toy, that was to make tea and coffee....

In a post elsewhere, I mentioned that by using water in the down flow pipe, it would be possible to get nearly isothermal compression, with its higher efficiency. There is a mine near a waterfall that does this and pays only maintenance for its compressed air.

If an underground CAES cavern could also have some way for the air in the cavern to absorb ground heat in a practical way, geothermal would provide a portion of the energy. BTW, liquified CO2 may make a better geothermal transfer fluid than water does. The article didn't state why. By putting this together with the waterfall trick, we could have a soda water geothermal system. CO2 absorbs better into cold water than into hot water. It would be interesting to see a set of calculations on this one.

DDHvi wrote:In a post elsewhere, I mentioned that by using water in the down flow pipe, it would be possible to get nearly isothermal compression, with its higher efficiency. There is a mine near a waterfall that does this and pays only maintenance for its compressed air.

If an underground CAES cavern could also have some way for the air in the cavern to absorb ground heat in a practical way, geothermal would provide a portion of the energy. BTW, liquified CO2 may make a better geothermal transfer fluid than water does. The article didn't state why. By putting this together with the waterfall trick, we could have a soda water geothermal system. CO2 absorbs better into cold water than into hot water. It would be interesting to see a set of calculations on this one.

Liquid CO2 is going to require high pressure and low temperatures, as at 1 atmosphere, CO2 sublimates directly from solid to gas, without an intervening liquid phase.

In fact, looking at the phase chart, you don't get liquid CO2 until above pressures at 5.1 atmospheres, and a temperature of about -57 degrees Celsius.

fallsfromtrees wrote:

DDHvi wrote:In a post elsewhere, I mentioned that by using water in the down flow pipe, it would be possible to get nearly isothermal compression, with its higher efficiency. There is a mine near a waterfall that does this and pays only maintenance for its compressed air.

If an underground CAES cavern could also have some way for the air in the cavern to absorb ground heat in a practical way, geothermal would provide a portion of the energy. BTW, liquified CO2 may make a better geothermal transfer fluid than water does. The article didn't state why. By putting this together with the waterfall trick, we could have a soda water geothermal system. CO2 absorbs better into cold water than into hot water. It would be interesting to see a set of calculations on this one.

Liquid CO2 is going to require high pressure and low temperatures, as at 1 atmosphere, CO2 sublimates directly from solid to gas, without an intervening liquid phase.

In fact, looking at the phase chart, you don't get liquid CO2 until above pressures at 5.1 atmospheres, and a temperature of about -57 degrees Celsius.

That is why I'm thinking of a soda water CAES. You would have lower compression costs due to the efficiency of near isothermal compression in the H2O/CO2 down leg, but could also operate at lower pressures at the top. Given even partial CO2/H2O separation in the cavern, you could have high pressure gas returns. You would need to supply a pressure difference between the H2O/CO2 up return leg and down input leg proportional to the density differences and leg height. You would have one absorbed down leg with high CO2 levels, one up leg with gas only, and one up leg with low CO2 levels.

I'm not saying this would be practical, just that someone should do the calculations needed to find out. The rock below would likely absorb some CO2 also.

PS, CO2 is being used in some oil fields to flush out extra petroleum.

PPS atmospheric CO2 is less than the weight of paper per square inch. Even a small improvement in agricultural practices too store more carbon in the soil would reduce the CO2 levels.

DDHvi wrote:

fallsfromtrees wrote:[
Liquid CO2 is going to require high pressure and low temperatures, as at 1 atmosphere, CO2 sublimates directly from solid to gas, without an intervening liquid phase.

In fact, looking at the phase chart, you don't get liquid CO2 until above pressures at 5.1 atmospheres, and a temperature of about -57 degrees Celsius.

That is why I'm thinking of a soda water CAES. You would have lower compression costs due to the efficiency of near isothermal compression in the H2O/CO2 down leg, but could also operate at lower pressures at the top. Given even partial CO2/H2O separation in the cavern, you could have high pressure gas returns. You would need to supply a pressure difference between the H2O/CO2 up return leg and down input leg proportional to the density differences and leg height. You would have one absorbed down leg with high CO2 levels, one up leg with gas only, and one up leg with low CO2 levels.

I'm not saying this would be practical, just that someone should do the calculations needed to find out. The rock below would likely absorb some CO2 also.

PS, CO2 is being used in some oil fields to flush out extra petroleum.

PPS atmospheric CO2 is less than the weight of paper per square inch. Even a small improvement in agricultural practices too store more carbon in the soil would reduce the CO2 levels.

Kalina Cycle works better at geothermal ranges (60C+) (ammonia water mix). The ammonia evaporates first and gives pressure to crank the turbine and is quite happy to condense in a flash condenser as it really likes water. (ammonia leaks are a little unpleasant however, but blindingly obvious (and containable with water sprays)). The key technology is deep well drilling (oil field technology)and fracking (ditto). Supercritical Liquid CO2 is also really good at stripping oil off oil shale and sand (but a little detergent helps too) (and then you strip it off and recycle it if you actually care).
As for isothermal compression, ICI were playing with deep well disposal of toxic hydrocarbon waste, a few years ago, by mixing it with water and oxygen and pumping it down a hole - it ignited on the way down and they got slightly grotty steam and CO2 on the return pipe.