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True, at least some of the time, but you might be drawing heat out of the Parrifin reservoir at times, and that may receive heat from the compression of air, off peak power, and if you have solar panels from those to some extent. So, you may not be drawing winter heat from outside air all the time.
Done.
Last edited by Void (2023-09-28 12:50:42)
I am starting to ask seriously "Why do I do this?"
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Put the tank into a tank of sand and the heat will be retained even longer.
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If we're going into a future with less energy, then we need vehicles that require less extreme up-front energy consumption, not more. It's good to see that the idea of a low-cost / short-range vehicle (suitable for 95% of real world driving) has at least some interest within academia, because electronic vehicles that have extreme energy / labor / materials inputs are not long-term viable. If I had to guess, everyone thought that there was no upper limit to emerging battery technology, without having done their homework about how much metal is required to make the batteries and electronics, as well as where that metal could be sourced from.
The average trip duration globally is 15 minutes long. The average trip distance globally is 15 Kilometers / 9.3 miles. The average speed globally is 30 km/h (or) 18.6 mph. On average, a person spends 4.5 years in a vehicle over their lifetime.
US DoE says 59.4% of trips were 6 miles or less.
Compressed air and hot water can easily provide that kind of range.
If we're going to have gas stations every 50 feet, then why not power them with compressed air and hot water?
We're in no danger of ever running out.
Even if you have to fill the tank up once per day, if the cost of the "gas" (air or water) is limited to the cost of the machinery providing the input energy, I'm pretty sure we can swing that. It's steel that can last a human lifetime. The lubricants are limited to bearing surfaces. The tires contain more oil than anything else. Let's say we charge people $2 to "fill up" and a car can go 75 miles. This implies they're driving 27,375 miles per year, and they pay $730/year. This provides $146B in revenue per year for 200M drivers "taking a trip to the moon" every 10 years, or $1.46T over 10 years. Recall how much metal my proposed solar thermal solution required to provide equivalent energy. $1.46T was a multiple of all material costs. Which means even when we include labor / transport / maintenance costs, people who can spare $2 per day can drive anywhere they please, we don't need to bash them over the head for requiring energy, and the "fuel" costs (air and hot water vs gasoline vs electricity) are the simplest / easiest to provide and least environmentally damaging of all possible fuels. If the car and its fuel supply are cheap enough, always available, and maintainable forever, then people will buy them.
This is the most puzzling aspect of "green energy". All the machines being touted as such consume quantities of fossil fuels equivalent to driving a gasoline powered car for 4 to 6 years, but the car makers want people to buy a new car every 2 to 3 years. The only way to make that work is to make each individual vehicle very cheap in terms of energy / materials / labor. That's the exact opposite of what we've been building, though, which is why there are now tens of thousands of EVs that haven't been sold- too much cost and not enough value proposition to the buyer.
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An interesting video on the Ragged Chute air plant in Ontario.
https://m.youtube.com/watch?v=yvgNqIuz2GM&pp
The plant is a trompe air compressor, probably the largest ever made. Like all trompes, it compresses air using flowing water and has no moving parts. The device was built in the early 20th century and produced compressedair to run mine tools.
Without any moving parts, a trompe has nothing that can wear out. The Ragged Chute plant ceased operations because the local mines were depleted. But had there remained a demand for compressed air, it could have gone on operating for centuries with little maintenance.
This presents an interesting opportunity if large numbers of compressed air vehicles are to be used in the future. Compressed air can be stored at high pressure beneath the sea or in underground caverns. Trompe compressors could generate air on land or at sea, and air could be distributed through steel pipes.
"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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One idea that I had that I was really quite fond of, but now realise would not work well: Low pressure compressed air energy storage.
My initial idea was to store air at low pressure ~0.5 bar(g) in trenches within the ground, covered with about 2.5m of compacted soil. The weight of the soil above the trench would balance air pressure within. The trench would be charged using a compressor like a trompe and energy would be recovered by venting the compressed air through a turbine. Because the compression ratio is so low 1.5:1, the cycle would be virtually isothermal. This really does simplify the charging and recovery steps. The energy stored in the compressed air has a low volumetric energy density of about 40KJ/m3. But the trenches are easy to dig and the system should last practically forever. So energy return on investment appears reasonable.
What is the big problem with this idea? The problem is the energy recovery turbine. With a pressure ratio across the turbine of 1.5:1 max (less as the store discharges and pressure declines) the turbine must be very large for the amount of power produced. This makes the turbine a high capital cost component. Whilst the air store is cheap, provided you have the space, the energy recovery step ends up being expensive because of the low power density of the turbine. If we have a direct use for the compressed air, such as feeding a blast furnace, the low energy density isn't such a big problem. But for energy storage, this doesn't look promissing.
"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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This topic by Terraformer seems (to me at least) like a suitable second home for this long post by kbd512 in the Fixing Cars topic.
https://newmars.com/forums/viewtopic.ph … 32#p224732
SearchTerm:Compressed Air Transportation systems (over 100 years of history)
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We keep putting topic information in as off topic responses that have nothing to do with where it is posted for the, most part.
In KBD512's case it is related to making a better fuel-efficient vehicle that is not a battery in the true sense.
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Application of Phase Change Material to Improve Adiabatic Compressed Air Energy Storage System
The advantages of CAES include high energy density and quality, but the efficiency is relatively low (about 50%) since a significant amount of the compression energy is lost as heat. Additionally, in the expansion process, this technology would require a non-renewable source of energy for heating the air to prevent frosting. To overcome this drawback, an adiabatic CAES (ACAES) system has been proposed by applying methods of storing the generated heat during compression. The generated heat during compression is stored in the specific thermal storage system and is utilised to heat up the air during the expansion process. This method eliminates or limits the use of extra energy to heat the expanded air, usually needed in CAES system, which enhances the efficiency of the system by up to 70%.
For the phase change material, perhaps salt hydrates would be best? Sodium carbonate hydrate melts at 33c. Though given the previously mentioned issues with humidity, ice does have a benefit here. Hmm.
Sodium carbonate and steel are cheap though (of course, so is water). And at temperatures that low we could scavenge heat from the environment to make up losses. Could we get to £20/kWh?
Use what is abundant and build to last
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For Terraformer .... in reading post #33, I remembered work done by Calliban and kbd512.
They spent some time thinking (and writing) about a system for transportation.
To my recollection, most of that work assumed pulling thermal energy from the air at run time.
Can the idea you've just described work for a car? I am concerned about mass needed for the thermal store, but if a solution can be found, then the package would not depend upon the external environment.
I am reminded (in thinking about this concept) how similar it feels to an electric battery, or a capacitor based system. In these systems we are moving electrons into a storage location and we are leaving an absence of electrons (holes) behind. The result is a strong desire of the moved electrons to return to their home bases.
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th,
Calliban posted a link to a car using phase change materials (I think?) in the fixing America's car industry thread.
Tbh I think water has been overlooked as a phase change material. Getting to 0c is most of the heat lost, and the ice would make precooling the air straightforward. Plus thermal energy lost will be lost at low temperatures -- perhaps a geothermal borehole could make up this loss, or even waste heat from somewhere. If we can effectively eliminate heat loss as an inefficiency we should be able to get up to the 80% round trip efficiency that other storage (batteries and pumped hydro) achieves.
Use what is abundant and build to last
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For Terraformer re #35
My recollection could be in error, and if so I'd welcome a correction. However, that recollection is that neither Calliban or kbd512 wrote about a full cycle energy storage system as you have done. My recollection is that each depended upon the external environment to supply energy to balance the stored energy. If the stored energy was heat then the balance came as cold sunk to the external environment. If the stored energy was cold, then the external environment was enlisted to provide thermal energy to enliven the stored material.
I'm hoping your discovery will inspire our members to try again, to achieve a full cycle in a single transport system.
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A use once system for the compressed air and water heated is about the same as driving an EV that the battery pack is made up of the common AA dry cells,
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Thinking about the thermodynamics of the proposed system some more... it's essentially an isothermal system where we're altering the environment to make heat transfer and storage far more effective. Compression would have to go slow enough that the temperature rise is small in order to achieve high efficiencies, though I still wonder if we can recover that energy so long as the maximum temperature the air reaches is less than ambient? E.g. if the compressed air reaches 20c and it's 25c outside, can we recover that in expansion using the heat from outside?
Use what is abundant and build to last
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For Terraformer ...
Can you design a self contained system?
I don't know the answer, but suspect from all of Calliban's writings that the answer is no....
Compressed air represents stored mechanical energy which is also elevated in temperature.
Normal practice is to remove the thermal energy by radiating or conveying it to the external environment.
Is it possible to just cut out the middle man? Just leave the thermal energy in the store, so that the air is "normal" when it is released?
Again from previous discussion my guess is the answer is no.
Update later... There is a scenario where the hot compressed air container might prove useful.... in a cold climate, the hot store might heat a cabin of a vehicle. I was thinking of a bus but perhaps the idea could extend to a car? The idea would be to pump air into containers that are then able to supply heat for the cabin for some period of time.
This idea might even work on Mars, where the working fluid is CO2....
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The great object lesson of Hurricane Beryl has been how laughably unreliable both electric power from a public utility and a home solar system are for providing power. We were without power for almost a week. If photovoltaics and laptop batteries are the sort of ridiculous nonsense we go to Mars with, then everyone reliant upon that power will be dead shortly after a sandstorm blots out the Sun. We need better solutions. Electricity is not the answer.
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For kbd512 .... since this is the "Compressed Air" topic, and since you have reported being without utility power for a week, I am offering you this opportunity to evaluate compressed air as a possible emergency power supply.
In the region where I live, natural gas is abundant, so folks use gas powered generators as backup for electricity, and gas grills or ranges plus gas water heaters and furnaces.
In your location, I understand that natural gas must be imported.
An air compressed energy storage system to sustain a home for a week would need to generate electric power and perhaps some pneumatic power. I would imagine electric power would be the major need.
Please compute the requirements for an air storage system that would have met all your family's needs during the recent outage.
The storage system would be located underground, so there is an investment in excavation, and the tank (or tanks) would be extremely strong. This (hypothetical) installation would not be as cheap as SpaceNut's pallets.
On the other hand, such an energy storage system should be able to wait patiently for years on end, before being called upon to deliver power at 2 kw levels for a week or more.
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For Terraformer .... I asked ChatGPT to ** think ** about the use of compressed air to supply 2 Kw to the kbd512 family for a week...
Compressed Air Energy Storage for Continuous Power Delivery
Hello everyone,
Given the recent impact of Hurricane Beryl in Houston, Texas, and the week-long power outage experienced by one of our members, I thought it would be useful to explore the potential of Compressed Air Energy Storage (CAES) for continuous power delivery. Specifically, let's look into what it would take to deliver 2 kW of power continuously from a CAES system.
Energy Requirement
We need 2 kW of power continuously.
Power is the rate of energy consumption. Therefore, 2 kW means 2 kilowatt-hours (kWh) of energy per hour.
Over a 24-hour period, this amounts to 48 kWh of energy.
Energy Storage in Compressed Air
The energy stored in compressed air can be estimated using the formula for the energy of an ideal gas: E = P × V × ln(P / P0), where P is the pressure of the compressed air, V is the volume of the storage tank, and P0 is the ambient pressure.
For practical purposes, this formula can be simplified, but it still depends on specific pressures and volumes.
Tank Size and Pressure
Let's assume we use standard high-pressure tanks that can handle 200 bar (about 2900 psi).
The energy content of air at 200 bar in a 1 m³ tank can be roughly calculated. At 200 bar, approximately 1 m³ of compressed air can store about 0.16 kWh of energy.
Number of Tanks
If each 1 m³ tank at 200 bar stores 0.16 kWh, you would need 48 kWh / 0.16 kWh/tank ≈ 300 tanks to store 48 kWh of energy.
This is an impractically large number, suggesting that either the tank pressure needs to be higher, the tanks need to be larger, or the system needs to be more efficient.
System Efficiency
The efficiency of CAES systems can vary, but let's assume an optimistic efficiency of 50%. This means you would need twice the stored energy to deliver the required output, so you would need 96 kWh of stored energy.
Therefore, you would need 96 kWh / 0.16 kWh/tank = 600 tanks under these assumptions.
Alternative Approaches
To reduce the number of tanks, you could increase the pressure or volume of each tank.
You could also use a hybrid approach, combining CAES with other energy storage methods (e.g., batteries) to smooth out demand and reduce storage requirements.
Summary
To continuously deliver 2 kW of power using compressed air energy storage, you would need to store 48 kWh of energy, factoring in efficiency losses, potentially up to 96 kWh. This could require approximately 600 standard high-pressure tanks at 200 bar, assuming an efficiency of 50%.This estimate demonstrates the scale of storage required for continuous power delivery. It also highlights the need for either very high-pressure systems or alternative strategies to make CAES more feasible for such applications. If you have specific parameters (e.g., tank size, maximum pressure, efficiency), we can refine these calculations further.
Looking forward to your thoughts and discussions on this topic!
Best regards,
ChatGPT4o (supervised by tahanson43206)
There may be better ways of doing this and there probably are, but this seems to me like a good starting point.
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th,
I'm pretty sure those figures are way off. A low pressure system 5-7 bars can get 0.6kWh per cubic meter -- https://solar.lowtechmagazine.com/2018/ … y-storage/. 70 bar systems get far more than that.
Use what is abundant and build to last
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For Terraformer re #43
Thanks for your observation about the potential of compressed air storage systems to perform at a higher level than the example in the post to which you are responding. That post was intended to start a process that would (hopefully) lead to a useful result that can be implemented by a home owner at a reasonable cost.
Please see if you can find a more attractive configuration and post it in this topic.
The post #42 shows a possible format for the alternative you may be able to find.
I've offered a goal to achieve: 2 Kw for a week. That would be an average. Actual consumption of stored energy would vary as the home owner consumes more or less power.
I'm hoping that NewMars members can find actual, existing equipment that can be assembled into a working package. My understanding is that there are already commercial scale compressed air storage systems. At least one has been reported in the forum, and the post(s) should be available for lookup
The home system would be much smaller than those, but considerably larger than what might be found in an automobile using compressed air.
Update: In reading over ChatGPT's work, I found this appears to be a crucial element:
Tank Size and Pressure
Let's assume we use standard high-pressure tanks that can handle 200 bar (about 2900 psi).
The energy content of air at 200 bar in a 1 m³ tank can be roughly calculated. At 200 bar, approximately 1 m³ of compressed air can store about 0.16 kWh of energy.
Is that estimate for stored energy in that 1 cubic meter tank high? Low? About right?
Does equipment exist that can meter the flow of compressed air through an air motor to generate that 2 Kw I'm asking for?
I assume the answer must be yes, because pneumatic tools use such regulators.
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This may be of use.
https://tribology-abc.com/abc/thermodynamics.htm
At 200bar(g), 1m3 of air will release 106.6MJ (29.6kWh), if expanded isothermally.
At 6bar(g) (0.7MPa(a)), 1m3 of air will release 1.36MJ (0.38kWh) if expanded isothermally.
Last edited by Calliban (2024-07-14 07:35:15)
"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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Thanks to Calliban for post #45....
I am unclear on the significance of the difference between isothermal discharge and adiabatic modes.0
In actual practice, it is my understanding that compressed air is allowed to cool before it is used, which means (to me at least) that it will enter the discharge stream colder than the surrounding air.
In any case, here is ChatGPTro's response to the updated information from Calliban:
Compressed Air Energy Storage for Continuous Power Delivery: Revised Estimates
Hello everyone,
Thanks to the input from our members in England and Scotland, we've revisited the calculations for Compressed Air Energy Storage (CAES) to deliver 2 kW of power continuously. Let's review the updated figures and understand the differences.
Energy Requirement
We need 2 kW of power continuously.
Over a 24-hour period, this amounts to 48 kWh of energy.
Considering an efficiency of 50%, we need 96 kWh of stored energy.
Revised Energy Storage in Compressed Air
According to new data, at 200 bar(g), 1 m³ of air can release 106.6 MJ (29.6 kWh) if expanded isothermally.
This is significantly higher than the initial estimate of 0.16 kWh per 1 m³ tank at 200 bar.
Revised Number of Tanks
With the revised value, the energy stored per tank is 29.6 kWh.
Therefore, the number of tanks required is 96 kWh / 29.6 kWh/tank ≈ 4 tanks.
Reason for the Difference
The initial estimate may have assumed adiabatic expansion, which is less efficient than isothermal expansion.
Isothermal expansion assumes constant temperature, maximizing energy extraction, while adiabatic expansion assumes no heat exchange, leading to lower efficiency.
Different assumptions or calculation methods regarding pressure units and energy content could also account for the discrepancy.
Summary
With the revised figures, it appears that to continuously deliver 2 kW of power using compressed air energy storage, only about 4 standard high-pressure tanks at 200 bar would be required, assuming isothermal expansion. This is a significant reduction from the initial estimate and highlights the importance of accurate assumptions in such calculations.Looking forward to your thoughts and further discussions!
Best regards,
ChatGPT supervised by tahanson43206
>>> space reserved for text on the difference in the modes of expansion
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in this session, I asked ChatGPT to clarify the expansion modes, in light of the difference between it's initial response and that of Calliban. Along the way, I clarified that I am considering an air motor driving a generator, and I get the impression that adiabatic expansion is more likely. However, Calliban will have the opportunity to clarify his vision of an isothermal configuration of equipment.
Understanding Isothermal and Adiabatic Expansion in Air Motors
Hello everyone,
Following our recent discussions on Compressed Air Energy Storage (CAES), we've delved deeper into the modes of expansion – isothermal and adiabatic. Here’s a summary of the key points to help clarify the differences and their implications for our project.
Isothermal Expansion
**Definition**: Expansion occurs with a constant temperature. Heat is exchanged with the surroundings to maintain this temperature.
**Characteristics**:
- Continuous heat transfer with the environment.
- More efficient in terms of energy extraction because the gas stays at a higher pressure for a longer period during expansion.**Example**: Slow expansion in a piston where heat can be transferred to/from the surroundings.
**Application**: Less common in typical air motors unless specific design measures (e.g., heat exchangers) are implemented.
Adiabatic Expansion
**Definition**: Expansion occurs without heat exchange with the surroundings. The process is insulated, so the temperature of the gas changes.
**Characteristics**:
- No heat transfer, leading to a temperature drop during expansion.
- Generally less efficient because the gas cools down, resulting in lower pressure and less work done.**Example**: Rapid expansion in pneumatic tools where air cools as it does work.
**Application**: Typical in air motors driving generators due to the rapid expansion process.
Application to Air Motors Driving Generators
**Adiabatic Expansion**:
- **Typical Scenario**: Air expands rapidly as it enters the motor, performing work on the motor's components. The rapid expansion usually does not allow sufficient time for heat exchange, causing the air to cool down significantly.
- **Efficiency**: Lower compared to isothermal expansion.**Isothermal Expansion**:
- **Possible with Design Adjustments**: Achieved if the air motor allows for heat exchange with the surroundings through heat exchangers or slow expansion.
- **Efficiency**: Higher due to constant temperature, but requires more complex and potentially costly designs.Summary
Understanding the difference between isothermal and adiabatic expansion is crucial for optimizing the efficiency and performance of CAES systems. In most practical applications, including air motors driving generators, **adiabatic expansion** occurs due to the rapid nature of the expansion process. However, with specific design modifications like heat exchangers, **isothermal expansion** can be achieved, leading to higher efficiency.It’s important to clarify the configuration and design assumptions in our discussions to ensure we're all on the same page and can effectively compare and improve our systems.
Looking forward to your thoughts and further discussions!
Best regards,
ChatGPT4o supervised by tahanson43206
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I pressed ChatGPT4o a bit further.... this time it came up with 49.6 MJ for the adiabatic case, and it seems to think one tank of 1 cubic meter at 200 bar can meet the requested output of 2 Kw for one hour.
Adiabatic Expansion and Tank Requirement for Compressed Air Energy Storage (CAES)
Hello everyone,
Following our recent discussions, we’ve verified the energy release for adiabatic expansion and found it to be approximately 49.6 MJ for 1 cubic meter of air at 200 bar. Now, let's calculate the tank requirement to deliver 2 kW of power continuously from a compressed air energy storage system using adiabatic expansion, taking into account the efficiencies of the air motor and generator.
Power and Energy Requirements
Desired power output: 2 kW (2000 W)
Continuous operation time: 1 hour
Total energy required: 2 kW × 3600 seconds = 7.2 MJ
Adjusted for efficiencies (air motor 70%, generator 90%): 7.2 MJ / (0.70 × 0.90) ≈ 11.4 MJ
Energy Released per Tank
Energy released per cubic meter of air at 200 bar (adiabatic expansion): 49.6 MJ
Tank Requirement Calculation
Energy per tank: 49.6 MJ
Adjusted energy required: 11.4 MJ
Number of tanks needed: Total Energy Required / Energy per Tank
Number of tanks needed: 11.4 MJ / 49.6 MJ ≈ 0.23 tanks
Since we can't have a fraction of a tank, we'll need at least 1 tank to deliver 2 kW of power continuously for 1 hour using adiabatic expansion. This single tank is more than sufficient to meet the adjusted energy requirement, providing extra capacity even when accounting for system losses.
Summary
To deliver 2 kW of power continuously for 1 hour using adiabatic expansion in a compressed air energy storage system:
We need at least 1 tank of 1 cubic meter of air at 200 bar.
Each tank releases approximately 49.6 MJ of energy under adiabatic conditions.
The adjusted energy requirement, accounting for typical system efficiencies, is approximately 11.4 MJ, which is well within the capacity of a single tank.
This calculation assumes typical efficiencies for the air motor and generator, providing a more realistic assessment of the system’s performance.
Looking forward to your thoughts and further discussions!
Best regards,
ChatGPT4o supervised by tahanson43206
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By extrapolation from the series so far, I deduce that a backup for kbd512's family might have consisted of 7*24 or 168 tanks of 1 cubic meter each.
In actual practice, a home owner would (most likely) install tanks with greater capacity, but at this point, I am trying to confirm (with input from the NewMars membership) if the estimate of one such tank would provide 2 Kw for an hour is anywhere close to the mark.
Calliban has an opportunity to show how an isothermal design might work in practice. I deduce that for this design to work, heat must be supplied from the external environment. In Texas in June, that seems do-able.
In Alaska in deep winter I'm less sure.
In either case, a mechanism is needed to provide for thermal flow, and that implies equipment.
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Calliban,
Is the difference in energy between isothermal and adiabetic expansion equal to the amount of energy that would need to be supplied as heat to achieve isothermal expansion? Presumably that's where the missing energy is lost.
Obviously in a home setting you'd start by minimising the amount of electricity you need to provide anyway... your hot water is going to be coming from a far cheaper and simpler hot water tank. Your actual electrical need is lights, devices, fans/pumps, and appliances (bearing in mind the washing machine isn't going to be heating the water, not when you can simply use the hot water you already have). Kettles, microwaves, hair dryers, air fryers, hobs, ovens are your big draws, lights and devices are not. Refridgerators can store cold easily enough. I suppose you could reengineer the kitchen appliances to make use of your hot water storage... inbuilt steam kettle running a heatpump off your hot water? Hot air fans for drying clothes/hair/anything else that operate likewise?
Costs are unlikely to scale linearly. The economics for a home system might not work out, whilst it could for a large user such as a school or hotel. That does limit the size of individual tanks however, since they'd have to be small enough to fit on a truck. Still, a 2m wide 5m long cylinder has a volume of ~15m^3, and if the air is isothermally compressed to 70 bar that will store 7kWh/m^3. Maybe 5kWh/m^3 accounting for inefficiencies. 75kWh per tank, could be buried. Incentivised by the ability for arbritage between fluctuating energy prices. Possibly a cheaper alternative to grid upgrades for an energy intensive industry... could also add one to an apartment block if treating it as its own grid.
(Yes I am thinking again about energy redoubts. A useful thing to add to the inventory.)
Last edited by Terraformer (2024-07-14 09:35:26)
Use what is abundant and build to last
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