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Ya cooling is required versus heating so I can see the short term no action much like the water situation when it's raining.
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This article discusses a community based cooking scheme in the Netherlands. The guiding idea is that cooking is more efficient when centralized, i.e. cooking for hundreds of people uses far less energy per capita than cooking for one person.
https://www.humanpowerplant.be/2020/06/the-fire.html
The Dutch concept burns biomass in a centralized community cooker to produce all of the cooked food for a community.
https://en.wikipedia.org/wiki/Low-temperature_cooking
The idea of low temperature cooking does not seem to have occurred to them. This involves slowly cooking at temperatures <100C, often over a period of days. Meats can be safely cooked at temperatures above 68C, which kills bacteria. Vegetables require temperatures of around 80C to soften. Temperatures in this range could be achieved using heat pumps with COP around 3. There are crystalline paraffin waxes that melt between 70-85C, which could function as phase change materials, storing large quantities of heat at specific temperatures.
A community equipped with a centralized low-temperature cooker could therefore cook using intermittent energy, provided by electricity, mechanical power or concentrated solar heat. A large cooker could be insulated by housing it in a deep pit, which would allow it to remain at constant temperature for many months without additional heating. This is definitely something that individual towns or city districts could build. But it requires that citizens cooperate and pool resources into developing community infrastructure.
If European countries lose access to natural gas and reliable electricity, low temperature community cooking is something we could use at a district level. The heat pump supplying the heat could be a positive displacement compressor, directly driven by a wind turbine shaft. Such a device could be mechanically very simple. It is even possible to imagine arrangements where a single heat pump provides cooling to a community freezer at -20C and heat to a low temperature cooker at 80C.
Last edited by Calliban (2023-06-28 06:13:49)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #127
Thanks for the link to the report on the Dutch community that is organized to use an ancient heating method in an efficient way.
The idea of operating bellows through an exercise program is quite interesting.
What must have seemed like drudgery to our ancestors is recast in the modern light as a way to stay in shape.
Obviously, (or at least I ** think ** it's obvious) this concept wouldn't work well on Mars.
What I think remains to be seen is whether the second generation are going to support this idea. The Amish (apparently) have a exit option for young folks raised in their system. Apparently a great number choose to keep the old traditions going, or at least ** enough ** do so to the population remains stable despite losses.
Your low temperature ideas are interesting as well, and it seems to me worth anyone noting the option. I am wary of the idea, and would never seriously consider it, having been raised in a time when safe cooking temperatures are drilled into the population. However, I'll be interested if you can find examples of individuals who have successfully employed the technique.
That said, I am ** very ** happy with all-day slow cooking, which produces savory results day after day, year after year, without a lot of attention needed.
All in all, I am in favor of organizing ourselves to enjoy an abundance of energy, and be able to forget about the bad old days of energy paucity.
In your writings, you seem (to my eye anyway) to swing between extremes of pessimism and optimism, with the mean toward the lower end of the scale.
(th)
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June 30th Earthside ...
for Terraformer...
It's been a while since I inquired about developments in your initiative with the government official.
Hopefully work is underway.
(th)
tahanson43206 wrote:For Terraformer re "Quick" response from government official....
http://newmars.com/forums/viewtopic.php … 76#p206676
A month has gone by .... I'm hoping you have time to follow up with your contact, to see what has happened.
I am doubtful anything is going to happen in your community unless you are there to poke and prod and move things along.
There appear to be generous allocations of national wealth available for communities to apply toward goals judged worthy.
For a goal to be judged worthy, it seems to me a presentation is required, and that requires a presenter, and a presenter needs a support team.
It seems to me that this forum is good for banter about possibilities, but for anything to happen in the Real Universe, it is necessary to apply pressure ON the Real Universe.
(th)
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Hmm. Barium Hydroxide has a melting point of 78c and a latent heat of 655MJ/m^3 (181 kWh). If that was connected to a heat sink at 10c, we might be able to extract about 14% of that as work (19.4% carnot efficiency; as far as I've been able to find out, our best heat engines achieve ~75% of theoretical maximum), so 25 kWh per cubic metre. 25 Wh per litre; ~10 Wh per kg. Worse than even nickel-iron, but hey, those temperatures are achievable with really simple solar collectors.
There may be better materials of course... lighter materials. This is roughly on par with hot water as far as energy density is concerned.
Other materials: paraffin wax can melt at 340K and store 200kJ (55 Wh) per kg. Of which we might extract 5 Wh... hmph. Far worse than hot water and more expensive. The advantage of phase change materials is constant temperature, but that isn't such an issue when the storage medium is liquid and you can take what you need and leave the rest at the same temperature. Water at 97c/370 with a heat sink at 300K could get 15% efficiency too and give us 12 Wh per kg with a simpler system. About a third of what lead-acid gives, but if you're after something that you can build and maintain yourself it's a better option, and with the solar collector being at least 3x as efficient as solar PV collectors it evens out.
(Yes, I know all these calculations have been done back in the thread, but I don't wish to search through them and I like working through things for myself.)
"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony
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If the waste heat can be used for something valuable, like district heating, then efficiency matters less. In a country like UK, we could build a solar thermal plant outside of a town. When it is sunny, it would generate steam at say 200°C, which would be dried and would enter an MP turbine, generating electric power. We could collect condenser water at 30-100°C and store it in a big, insulated tank. Come winter, we pump it around town in a district heating network.
Last edited by Calliban (2023-09-06 08:42:01)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #131
I don't know what "drying" steams means, in your post.
My choices are: Google or just ask you ...
Asking you has the distinct advantage of giving you feedback that your post was read by at least one person.
(th)
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For Calliban re #131
I don't know what "drying" steams means, in your post.
My choices are: Google or just ask you ...
Asking you has the distinct advantage of giving you feedback that your post was read by at least one person.
(th)
Unless the steam is superheated to a temperature above the critical temperature of water (374°C), it will consist of a mixture of water vapour (gas) and liquid droplets. This is wet steam. Dry steam is pure H2O gas. If you attempt to put wet steam into a turbine, whose blade tip speed is usually supersonic, collision with water droplets will destroy the blades. So boilers have steam dryers mounted on top of them. These introduce vorticity, creating centrifugal force which removes the water droplets from the steam. The dry steam can then enter the turbine. Most coal burning plants have superheaters that take the steam up 500°C. Steam at this temperature does not need to be dried, as it is above the critical point of water.
Last edited by Calliban (2023-09-06 10:20:41)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #133
Thank you for the explanation of the concept of "dry" steam.
SearchTerm:steam dry explanation of
This topic is "Thermal Energy Storage" so I am at risk of departing from the theme with this observation...
Mars is shy of water, but has an abundance of carbon dioxide ... I asked Google if there is such a thing as a turbine that runs on hot carbon dioxide gas, and it found a citation of Toshiba having developed such a device. I'll add to this post from the computer where I found the citation.
***
I asked Google if there is such a thing as a gas turbine that runs on hot carbon dioxide gas, and if found one ...
I note that Google is now including AI in their process...
Generative AI is experimental. Info quality may vary.
Yes, there are gas turbines that run on hot carbon dioxide gas. These turbines use supercritical carbon dioxide, which is kept at high pressure and temperature. The carbon dioxide is in a state between a gas and a liquid, allowing the turbine to generate power.
The Japanese company Toshiba developed a gas turbine that uses CO2 gas produced at 1150°C and 300 bar. Echogen Power Systems in Akron, Ohio designed an 8-MW generator that uses supercritical CO2 to turn waste heat into electricity. The process produces about 20% more power than a gas turbine alone.
Supercritical carbon dioxide is easier to compress than steam. This allows a generator to extract power from a turbine at higher temperatures. The result is a turbine that can be 10 times smaller than a steam turbine.
Back to Calliban ... given the above, it would appear (to me at least) as though a small nuclear reactor is the best choice for a heat source for Mars. There is plenty of CO2. The gas would have to be cleaned up for use in the system described above, but once it is ready for use, I would imagine it could be kept in a closed loop for an extended period.
There might be issues with valves and seals?
I note that the gas turbine using CO2 has come up in the forum previously.
(th)
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I think that multiple source is better than one unique energy source.
If the mission is just go and return, certainly a closed nuclear reactor, with minimal maintenance is probably the most practical. But if a minimal IRSU is gonna be developed, a nuclear reactor is too complex. Only some replacements, specially fuel, can be considered. The rest would be imported.
Solar thermal with parabolic mirrors should be easy enough to manufacture on Mars. The low temperature of the cold side of the thermodynamic extraction should be do it even more efficient than on Earth. Not very high temperature needed, even if the concentration allows it. I guess regular salt storage could be enough.
For long term storage, CO2 liquefaction could work well for cheap and easy manufacture.
The nuclear reactor should be enough for essential energy needs, while regular solar allows to boots to exceeded energy production.
Something like.
Essential.
Life support. CO2-O2 purification + Thermal regulation on "save energy" mode + basic systems (essential communication, greenhouse, etc.) + Minimal H2O extraction... etc.
Secondary
Vehicle recharge. Fuel generation. Thermal up to comfort level. H2O in regular use (not rationed like essential mode).
Extra
Generation excess. Safety margins. Extra storage in energy, fuel, water, etc.
It's only needed that nuclear cover the essential. Everything else could be covered using IRSU.
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Cryogenic energy involves the production of liquid nitrogen or liquid air in a shore side refrigeration plant. The LN2 or LAir is then pumped or drained into propellant tanks onboard the ship. The ship raises power by evaporating the liquefied N2 or air within a boiler and passing the high pressure gas through a turbine. At least a few researchers are looking into this idea.
https://maritime-executive.com/editoria … propulsion
The problem is energy density. One kg of diesel contains about 43MJ of thermal energy. About 20MJ of this can be extracted as work by diesel engines. By contrast, the amount of potential energy yielded by liquid nitrogen is 0.349MJ/kg. That is 57x lower per unit mass and 45x lower on a volume basis. So liquid air would take up much more volume than diesel.
https://en.m.wikipedia.org/wiki/Energy_ … ence_Table
I think the best approach would be a hybrid drive system. The ship would carry both diesel and liquid nitrogen engines. The ship would make use of the waste heat from the diesel engines to evaporate the LN2. This would boost the efficiency of energy recovery from the N2. The extra power from the N2 would cut the diesel consumption of the ship by as much as one half. This would allow freight ships to take more direct routes to their destinations, avoiding the need for refuelling stops. It also makes sea freight less sensitive to oil price spikes and shortages. Whilst LN2 would not eliminate marine fuel consumption, it could reduce fuel consumption considerably.
Last edited by Calliban (2023-09-07 08:54:00)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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