Half right. If you compress the air it gets hot, but not because of friction. Instead it gets hot because the kinetic energy of the gas goes up. If you then cool this compressed air to outside temperature, and finally expand it it will get cold. So yes, you can store cool in compressed air, but in fact you are storing far more energy this way, which can do work later as cooling power!
Interestingly, if you pressurize the air, then let the compressed air cool to ambient and store it, then finally expand it out into the office, you have invented a gas-cycle heat pump, i.e. a simple air conditioner. Expanding compressed air quietly is a difficult problem, perhaps the air could be expanded through air motors which could then provide cool and power at each desk. Just make sure you wear hearing protection.
I suspect that such a scheme would be significantly less efficient than a phase change heat pump.
I doubt that very much. I suspect that 40C @ 80% is a) not possible anywhere on earth, b) lethal. People just don't understand how relative humidity goes down so fast with increasing temperature.
I hear people saying that they get 35C and 90% humidity in Brisbane, but I'm really doubtful. A quick look around and the maximum dewpoint is around 28C, which is not 90% at 35C! You might get 90% humidity and 35C, but not at the same time. We get 90% humid and 35C in Melbourne too;) (I'm currently sitting in 43C with a relative humidity of 12%, and I think I'd rather have 35C with 28C dewpoint - for a start my eyeballs would stop drying out:)
However Helium is very common in the rest of the solar system, so if it became scarce and we needed lots of it for our quantum thingies or superconducting whatsits there would be a good incentive to do space things more. So if you want to live on the moon, waste He.
Re:Here's what's really going on:
on
RFID Cookware
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· Score: 1
If you read the wikipedia article on induction cooking you'd know that induction cookers mainly rely on magnetic hysteresis heating rather than eddys, and thus you need to use something with a large loop. Conductivity doesn't come into it - you could use suitable non conductive ferrites without significant effect. Also, there is no reason why you couldn't add a copper layer for heat spreading if it is important.
Yeah, as I said there is a lot of BS floating around.
One form of solar that can pay back in months is solar space heating. There are simple designs for 'solar closets' that provide say 10 kW hours/day of heating for $100 investment. You can't even buy a good gas heater for that price, ignoring the price of the fuel entirely.
Actually I recently read that even these renovations typically never return their cost in a selling house. Your are spot on about the subjective nature of people, and they will never like the colour scheme, the fixtures or the rangehood. Having recently bought a house I am begining to understand the german idea of taking everything including the kitchen sink with you. (That's why Ikea sells lots of kitchen stuff - even in rental places you take your kitchen with you, apparently!)
On the other hand, having just bought a house my first priority has been to replace the cladding with a much higher R-value, regas the split-cycle, double glaze and install solar hot water. Those things will be earning me money long before I sell the place. I can survive 3 years with an old bathroom.
Indeed. I'm actually writing a simulation for this exact problem (actually, I'm working on solar greenhouse design) Email me if you're interested in code.
I presume you are ranting about PV, because otherwise what you say makes no sense. Solar hot water pays itself of in a year or two, so I presume you installed that. You very likely use more energy to heat water than all non heating electrical demand combined.
Incidently, this algal technology would give a lower efficiency than PV cells. The mitigating factor might be the low cost of construction, but to be honest I expect that the maintenance costs will swallow any real advantage.
You are wrong about the overall efficiency of solar panels, even the cheapest ones are 15% these days, and there are plenty of new solutions in the mid 30%s. That's more efficient than most cars (and I'm only talking about the engine efficiency, not well to wheels!). For example, a good solution: http://www.greenandgoldenergy.com.au/
I don't think the glowplugs (if they even still use them) would be used. They're only to bring the system up to operating temperature. It's not going to cool much in 5min. I believe these days diesels start directly using an electric motor, and this would certainly be practical if the car has a 30kW motor-generator attached directly to the engine!
Wikipedia: "Modern automotive diesel engines with electronic injection systems use various methods of altering the timing and style of the injection process to ensure reliable cold-starting. Glow plugs are fitted, but are rarely used for more than a few seconds."
I've often wondered whether we could design a system of multiple heat exchangers that can be attached to various heat and cold sources, with a computer selecting which to use. A single compressor would drive through some kind of valve to a set of say 4 heat sources/sinks (say outside air, air in greenhouse/sunroom, pool and roof cavity) to be used as condensers/evaporators. If it were practical the system could even directly connect to the fridge, and multiple wall units in the house. To do this we would need to use a more benign and cheaper working fluid, such as propane or R403A or whatever. There could even by a neighbourhood grid of liquid and gas refrigerant with a central compressor in a box out of the way to balance the system.
This might become practical if things like thermotunnel cooling become practical.
Ok, sounds believable. Though I would have thought that a similar thickness block of solid PMMA or PC would deliver comparable stiffness, but then the thermal resistance would be too high. I suspect there are a number of related reasons. Again, using solid diamond would sold the stiffness problem;)
I think it is more a matter of heat dissipation. Metal conducts better than polycarbonate and spreads the heat out evenly to resist buckling. When we can make diamond on demand you can have your transparent case.
Deep lakes offer something more valuable than direct energy in summer - they offer pure 'cool'. http://en.wikipedia.org/wiki/Deep_lake_water_cooli ng Considering this offsets 200MW of electricity, it can be regarded in essence as a 200MW generator, which is pretty good for its cost. (And you get clean drinking water too!) There are also farming techniques that dramatically increase crop output using soil cooling.
Note that the lowest temperature you can get in a liquid lake bottom is 4C, that doesn't leave much room for heat engines.
Personally I think with better use of energy (better insulation and design) and solar/wind/local energy we probably can move away from fossils quite quickly. It will hopefully sort itself out as fuel prices go up and the economic costs of climate change (if that is measurable) kick in. Unless we have a big war and go out with a bang...
Are you including the carnot efficiency in your calculations (I'm too lazy to work it out). That corresponds to an error factor of 22/277 = 12.6, i.e. you'd need 3777 of them if you've forgotten.
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Half right. If you compress the air it gets hot, but not because of friction. Instead it gets hot because the kinetic energy of the gas goes up. If you then cool this compressed air to outside temperature, and finally expand it it will get cold. So yes, you can store cool in compressed air, but in fact you are storing far more energy this way, which can do work later as cooling power!
Interestingly, if you pressurize the air, then let the compressed air cool to ambient and store it, then finally expand it out into the office, you have invented a gas-cycle heat pump, i.e. a simple air conditioner. Expanding compressed air quietly is a difficult problem, perhaps the air could be expanded through air motors which could then provide cool and power at each desk. Just make sure you wear hearing protection.
I suspect that such a scheme would be significantly less efficient than a phase change heat pump.
I doubt that very much. I suspect that 40C @ 80% is a) not possible anywhere on earth, b) lethal. People just don't understand how relative humidity goes down so fast with increasing temperature.
I hear people saying that they get 35C and 90% humidity in Brisbane, but I'm really doubtful. A quick look around and the maximum dewpoint is around 28C, which is not 90% at 35C! You might get 90% humidity and 35C, but not at the same time. We get 90% humid and 35C in Melbourne too ;) (I'm currently sitting in 43C with a relative humidity of 12%, and I think I'd rather have 35C with 28C dewpoint - for a start my eyeballs would stop drying out :)
However Helium is very common in the rest of the solar system, so if it became scarce and we needed lots of it for our quantum thingies or superconducting whatsits there would be a good incentive to do space things more. So if you want to live on the moon, waste He.
If you read the wikipedia article on induction cooking you'd know that induction cookers mainly rely on magnetic hysteresis heating rather than eddys, and thus you need to use something with a large loop. Conductivity doesn't come into it - you could use suitable non conductive ferrites without significant effect. Also, there is no reason why you couldn't add a copper layer for heat spreading if it is important.
Admittedly, a very big and bright light bulb...;)
Not much if those spikes only lasted for a microsecond.
Yeah, as I said there is a lot of BS floating around.
One form of solar that can pay back in months is solar space heating. There are simple designs for 'solar closets' that provide say 10 kW hours/day of heating for $100 investment. You can't even buy a good gas heater for that price, ignoring the price of the fuel entirely.
Actually I recently read that even these renovations typically never return their cost in a selling house. Your are spot on about the subjective nature of people, and they will never like the colour scheme, the fixtures or the rangehood. Having recently bought a house I am begining to understand the german idea of taking everything including the kitchen sink with you. (That's why Ikea sells lots of kitchen stuff - even in rental places you take your kitchen with you, apparently!)
On the other hand, having just bought a house my first priority has been to replace the cladding with a much higher R-value, regas the split-cycle, double glaze and install solar hot water. Those things will be earning me money long before I sell the place. I can survive 3 years with an old bathroom.
Indeed. I'm actually writing a simulation for this exact problem (actually, I'm working on solar greenhouse design) Email me if you're interested in code.
And yet they are wrong!
3 216&CategoryID=949
http://www.toolbase.org/tertiaryT.asp?DocumentID=
"Paybacks vary widely, but you can expect a simple payback of 4 to 8 years on a well-designed and properly installed solar water heater."
http://www.nrel.gov/ncpv/energy_payback.html
"Paybacks for multicrystalline modules are 4 years for systems using recent technology"
There's a lot of BS flying on both sides of the debate, but the reality is that PV is a good solution for many problems.
Kyocera powers their entire solar panel plant on PV.
I presume you are ranting about PV, because otherwise what you say makes no sense. Solar hot water pays itself of in a year or two, so I presume you installed that. You very likely use more energy to heat water than all non heating electrical demand combined.
Incidently, this algal technology would give a lower efficiency than PV cells. The mitigating factor might be the low cost of construction, but to be honest I expect that the maintenance costs will swallow any real advantage.
You are wrong about the overall efficiency of solar panels, even the cheapest ones are 15% these days, and there are plenty of new solutions in the mid 30%s. That's more efficient than most cars (and I'm only talking about the engine efficiency, not well to wheels!). For example, a good solution: http://www.greenandgoldenergy.com.au/
Correct. We all went out and bought Yepps for half the price and twice the features.
Ok, so my post was correct - a hybrid diesel will be able to stop and start the engine once it has warmed up.
I don't think the glowplugs (if they even still use them) would be used. They're only to bring the system up to operating temperature. It's not going to cool much in 5min. I believe these days diesels start directly using an electric motor, and this would certainly be practical if the car has a 30kW motor-generator attached directly to the engine!
Wikipedia:
"Modern automotive diesel engines with electronic injection systems use various methods of altering the timing and style of the injection process to ensure reliable cold-starting. Glow plugs are fitted, but are rarely used for more than a few seconds."
So that's why they do it! Thanks for your info. I wonder if there is some kind of DSSS type chipping to avoid that problem.
Well you could stop watching it!
I've often wondered whether we could design a system of multiple heat exchangers that can be attached to various heat and cold sources, with a computer selecting which to use. A single compressor would drive through some kind of valve to a set of say 4 heat sources/sinks (say outside air, air in greenhouse/sunroom, pool and roof cavity) to be used as condensers/evaporators. If it were practical the system could even directly connect to the fridge, and multiple wall units in the house. To do this we would need to use a more benign and cheaper working fluid, such as propane or R403A or whatever. There could even by a neighbourhood grid of liquid and gas refrigerant with a central compressor in a box out of the way to balance the system.
This might become practical if things like thermotunnel cooling become practical.
Ok, sounds believable. Though I would have thought that a similar thickness block of solid PMMA or PC would deliver comparable stiffness, but then the thermal resistance would be too high. I suspect there are a number of related reasons. Again, using solid diamond would sold the stiffness problem ;)
Hehe, it was a reference to the barn-pole paradox; but to be honest I have no idea what this does with FTL stuff.
Interestingly, due to dilation the rear door is in front of the entrance!
I think it is more a matter of heat dissipation. Metal conducts better than polycarbonate and spreads the heat out evenly to resist buckling. When we can make diamond on demand you can have your transparent case.
Deep lakes offer something more valuable than direct energy in summer - they offer pure 'cool'. http://en.wikipedia.org/wiki/Deep_lake_water_cooli ng Considering this offsets 200MW of electricity, it can be regarded in essence as a 200MW generator, which is pretty good for its cost. (And you get clean drinking water too!) There are also farming techniques that dramatically increase crop output using soil cooling.
Note that the lowest temperature you can get in a liquid lake bottom is 4C, that doesn't leave much room for heat engines.
Personally I think with better use of energy (better insulation and design) and solar/wind/local energy we probably can move away from fossils quite quickly. It will hopefully sort itself out as fuel prices go up and the economic costs of climate change (if that is measurable) kick in. Unless we have a big war and go out with a bang...
Are you including the carnot efficiency in your calculations (I'm too lazy to work it out). That corresponds to an error factor of 22/277 = 12.6, i.e. you'd need 3777 of them if you've forgotten.