I think thats the difference between rules that sys admins work under and procedures the sys admins create and enforce - most importantly are given the authroity to enforce.
I've rarely seen good rules come from above.
I've seen a lot of good rules/procedures come from sys admins to be signed off on by above. In the cases where management accept the recommendation as is its a good thing - where it gets rejected, or discussed by manglement and "improved" it isn't
I use it for Morrowind which I'm playing at the moment
Not because I didn't buy it, I did plus the expansions, but because I absolutely hate having to put a 700Mb CD into the drive to play a game when I have a 200Gb of hard disk right there...
(and and because the original disk is getting so scratched it takes an hour to manage to do an install - I thought taking an image to be a safe precaution)
I'm a perl developer:) I certainly don't need any more obscurity!!
Having predecessors whose code I end up maintaining that had actually read PBP would be a very very good thing
(especially the 0th rule "Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live." - alas I don't know where they guy who wrote what I spent 3 months ripping to pieces to make sane lives)
Quality of sys admin is inversely proportional to the number of rules they have to work under.
The more red tape an admin has the worse the actual results they will provide
When you take a good sys admin, tell them what you want, give them a sensible budget and ask them to delvier it you will frequently get a great system.
When management try to micro manage, heap them with rules, specify particular components because they read an artical that described it as good or the vendor took them out to lunch you will get problems - lots of them.
Right now I work in a very large bank and some days I think the admins could not find their rear end with both hands and a man page - I've never met them persoanlly so no idea what they are actually like. From otehr friends I have working in banking I know how much red tape they have to work under and I suspect half of the problems the user end sees (bear in mind I'm an ex admin myself and now developer) are caused by the red tape, not by the admin.
Virtual break glass on the root password? 2 weeks aproval before changing anything, even if its trivial? These are the kind of things that can drive an admin insane.
Last company I worked for was a start up - a great place to work for a short period, the admin their was very competant on solaris, windows and linux, had a great system implemented. It didn't start going downhill til a new CEO came in that started to micromanage him (and everyone else). Thats why I got out, same for a few others, the sys admin is leaving when he can find something else he wants to do. Still even with all the hassel he had I still got great results from him, mainly because I respected his limitations, didn't break things, knew what I was doing and helped him out when he needed it. Sales staff on the other hand? With them if it wasn't explicitly on his supported list he;d tell them to take a running jump - because of all the hassel they caused breaking things (the same way repeatedly), ignoring instructions, using unsupported devices or software and then wanting it fixed - and they wondered why he didn't want to help them?
Sys admins are human like the rest of us - overly managed they are stiffled, pissed off they are unhelpful - what else would you expect?
While I'm shopping should I look for a sarcasm detector for you? Or possibly a sense of humor?
One of the main reasons for the high rates solaris admins command is where its used - the financials, most of them still use solaris (8 in a lot of cases) though I know of a few running AIX.
The financials pay far better than almost any other comparable position, the stress and pressure is a lot higher but if you can cope with that you are well compensated. (london rates are 500-600 a day right now). Commonality between unix's will not change that, those that can perform in such environments and cope with the pressure will still get those roles, those that can't or don't want to will go for different positions.
Personally I'm happy to be out of the admin game (both unix and san) - been there, done that, can still do it but prefer not to, to be honest I get bored of it. Right now I'm happy in dev, back office currently, the rates are the same or better as what the admins are and i get more variety - just my preference.
(though if you are a decent solaris admin and happy doing it any chance you want to apply here - ours seem to be able to manage to break the home directory nfs mounts on average twice a month - some how doing it on a different day for each user.... then take 2 days to get it back, though I suspect 80% of that time is the usual banking beaurocracy)
I want it to take a learning curve for people to transition to it!!
How else am I going to continue justifying an obscene daily rate for having solaris 8&9 skills in bank if any monkey thats run linux for a bit has the same skills?
Supply and demand is why the average solaris admin can get double what a linux or windows admin can
You the have trust in the competancy of the developers that it will allocate the resources it needs then suid to a lower priveleged user.
Admittedly thats 2 parts - one the OS being designed to let you do that.
Two, having decent developers with well tested products - I know you wont have an issue running apache as root and letting it suid - but how about some unknown piece of software you have never heard of? Will you just run it as root without thinking? Probably not.
After sky diving regularly (to the point of being licensed and in control of yourself in the air) you start to look at the sky differently. It ceases to be just something that is there, instead its a medium that is yours, you can move with it in, you feel as though you have an extra degree of freedom - its changes your perspective.
I'm told many pilots and other aerial sports people feel the same way - ditto for divers and the water.
Harking back to the good old days of high school...
We had several antiquated BBC micros in one of the classroom blocks public areas - in theory for getting work done during break but since no other classes used those machines they usually ended up having games on them for those that knew how to find (or write) them.
Bored one lunch time I typed in the same 20 or so lines of basic on each machine and with the help of a friend hit enter at the same time on each.
The screen now flashed from black to red and black, beeped every second and read "This computer will self destruct in: 5:00" counting down every second. After a bit of a giggle (ok we were 12) at how this looked we walked away and wondered who would find it.
It turned out to be one of the dinner ladies (for those that didn't have this concept in school - they are non teaching staff that wander the open building and grounds during breaks keeping an eye on things). Being about 60 or so she obviously beleived what the computers said and hit the fire bell!
One evacuation later and a short investigation of the computer screens (which if I had got the code right should have one letter on each screen - B O O M - I never did see the final result so I don't know) everyone returned to classes.
Didn't really hear much until my next IT class, at the end the teacher took me to one side - his comments were basically:
"Very nice trick, but please, don't do it again, ok?"
Was fairly obvious it was me, only the lowest years of the school were allowed in that area, I was the only one in that categry that could have done it. I do remember the teacher was trying to stop himself from grinning.
The free air con was that as the air comes out of the cylinders its going to decomress and cool down and if you pump that through your house as it does.
As I said - misuse of Charle's law gives interesting results.
The assumption was that you could store this compressed air, and that in compressing it it would get hot and that you would have to cool it - that cooling could be used to heat water and you would still have the compressed air.
The original thoughts came in between discussing the new compressed air car motor and ground source heat pumps
Getting over 100% effective efficeincy (though not actual efficiency) is obviously easy with a heat pump - 400% is feasable I beleive - though its obviously a different mechanism of effectively moving heat from one place to another - not trying to pull it out of the same process twice in different ways.
Since you are familiar with this please do just double check my assumption in discarding all of this:
If you compress 540 cubic feet of air, to 6000 psi and store it in a 1.323 cubic foot cylinder at 6000psi then the heat gain is going to be negligable? (there will be some at the pump I suspect, but the system as a whole will just balance out)
Though if anyone can demonstrate a way this would work and still half an electric bill given 3:0 peak:offpeak pricing (the measure I figured would be the only viable option for it) I'll retract the above;)
However given the tank specs I was looking at (tanks hold 540CF of air at 6000psi) I can't see you getting the temperature differential during compression I was thinking of (my original math came up with a delta T of over 100K but I explained why that was incorrect) I can't see it happening unless you expend more energy to compress the gas to raise the heat and pressure before you cool it and I suspect (though I could be wrong) that its cheaper to just heat the water...
You would still get some cooling effect and the 64% efficency on storage is correct (and for me would still be a small saving) but to be honest I think I'll just install a heat pump.
You finally convinced me to check my math several times - I'm afraid this is one of those cases where back of the paper napkin science still seems close to rational enough in the cold light of morning.
Actually the math is right, perfect, spot on, not a single mistake. As is all the specs. I'd gone over them myself a few times trying to convince myself of all this (as had obviously suceeded) - still not quite believing it I had checked up on all the individual things when sober and it seemed to all add up.
I found the problem though.
One calculation in the middle based on Charle's law when the situation it was describing had variable pressure (had to rewrite the calculations from scratch to find it - probably something I should have done on sunday but never mind)
Not sure which is stranger though the fact I didn't notice the problem or the fact my brain commonly goes on tangents like this (drunk or sober) though I normally just rule out random ideas much sooner.
I do think its important to be able to admit when you are wrong - and apologise to all concerned about the general content of this thread and blame it on only 16 hours sleep total in the last 96 hours (not to mention nearly being at the end of a 12 hour shift which I thank you all for the diversion you have given me this afternoon)
There is no such thing as free energy. However air has quite a bit of energy - about 1J/gK at stp
Lowering the pressure of a gas will lower its temperature - this is how a lot of cryogenic plants work, using expansion of compressed gas as a cooling machanism (compress, it heats up, cool to room temp while under same pressure then decompress, and voila the temeprature has dropped)
Take a piston, compress the gas inside it to 6000psi, its going to get hotter.
Leave it to cool back to romm temperature but without retracting the piston (lets assume for the moment there is no leakage or air in or out - thats another matter and I'm trying to keep this simple for you) - keep it at that pressure, the gas is not going to go to a lower pressure, it can't it has no where to go.
If you think it will go to a lower pressure I'd love to hear your explanation - I could really use a good laugh!!
The "waste" heat is what you get from the air as you compress it - not from inefficiencies of the compressor, see Charle's law. You get maybe 4kWh of waste on the compressor itself (and you need to make sure it does not over heat) and the air itself is what gives you the rest, it needs to be cool enough by the time it reaches the tanks not to damage them or the valves.
The pure energy storage of this type of system? 64% efficent at best (assuming 80% efficent compressor and 80% efficient turbine/generator system - actually quite realistic for good quality systems)
You gain on the heat you pull out of the air (see air source heat pump), you also gain on cold air that replaces the power you would need for air conidtioning, so in value to you its a lot mor than just the power storage capability - as said before downside = cost + implementation complexity
See the diagram someone else linked for how its done on large scale power stations
It takes the energy from the air - same as an air source heat pump (which are available as commercial heating solutions), its not as concentrated as in the ground but its there go read up on them
No the ideal gas law says that in a closed system if you increase the pressure you will increase the temperature and via verser - there is nothing to stop you taking the energy from that energy increase and moving it elsewhere. (if what you were saying were true freezers, fridges, heat pumps or air conditioning systems would not function)
You don't cools the tanks by the way, you cool the air just after it leaves the compressor before it reaches the tanks - its still at high pressure at this point, cooling it doesn't lower the pressure.
You do not need to insulate the air tanks - the only requirment is the air going into the tanks is at a temperature within the tanks tollerance (hence cooling it while its still at pressure)
A lot of this is counter intuitive I will admit - but thats because you are trying to ignore the whole system and think only of the electic in, the compressor, the tank, and then decompressing through the turbine. The energy within the air is the other component within the system (and the fact when the air is decompressed its much cooler, ie has less energy)
Feel free to do the math, compress 10800 cubic feet of air to 6000psi, find out what temperature it now is, figure out the specific heat capacity, find out what water is heated by using the water to cool this, find out how much cooling potential you have on release, then add in the 64% (ish) efficiency you have on the actual electric storage to generation cycle, then take into account 3 times price difference of peak to off peak prices (which is what I currently pay, see economy 7 tariff on scottish power for regions in the south of england if you want proof of that)
Now the hard bit - putting that system together, safely with the right automatic controls as someone else here pointed out - hence as in my oringal post the $40k price tag (and thats being optimistic)
Oh and the discussion was on solar energy and its viability in a peak/off opeak pricing system - my comment was on the latter
my current electricity bill for an average house in the uk is 1200 pounds per year - and I don't have air con - thats 2400usd btw
Thats way above average as where I am located I'm stuck with storage heaters.
Something like this could half my electric bill plus provide air con (which I don't currently have) and would provide more hot water than I currently use.
Yet it would still take 10 years atleast to break even - as I said the problem is the cost.
It wouldn't help if everyone increased their off peak usage, but electric companies are keen to make sure their off peak usage atleast uses all the power nuclear plants can make - sicne these are effectively always on it makes sense to get the most use from the possible. For the uk the provide about 20% of total generating capacity (or atleast did in the late 90's the last time I had access to detailed figures, I'm sure you could find more current info online if you are inclined to look)
Exactly, you cannot beat the laws of thermodynamics, but you can in effect steal energy from elsewhere, same as with heat pumps
The problem with any peak time storage based system (which the discussion got to by power companies forcing people onto the peak/offpeak rates) is if it gets suffiently viable to store power when its cheap everyone will start doing it and then the peak/off peak will average out... however that averaging out on the whole would be a good thing, but economically isn't really going to happen.
Yes its an over simplification - its a post on slashdot.
The tollerance specs on the equipment required runs to several pages each, tanks, turbine generator, not to mention water and air pumps plus the control systems you would need.
You're right though - the best place to "store" energy is in the grid -especially if you can get a decent sell back price from them.
As you say water storage for temerpature is also pretty good (but then thats the other side of this system for home use, you store the heat generated by compression into water)
Net the air compression storage by itself is worse than batteries - you dont have the economies of scale large power plants that use this do. It becomes useful in the side effects of hot water and cold air.
But personally I'd rather go for a wind turbine, a ground source heat pump and cutting down usage where I can (I'm in the uk so solar isn't too much use)
No you pull the energy out of the heat in the air.
Check it - take 10800 cubic feet of air at stp, comrpess it to 6000psi - keeping it at the same pressure cool it with water, now figure out how many joules has gone into that water and how much that water temperature has now gone up.
You still have the compressed air in the tank - which gives you both cool air on demand and its stored potential energy (ie the compressed air will drive a turbine)
Depend son the area - UK economy 7 tariff is 3.5p/unit off peak and 11p/unit peak - atleast where I am.
Also that 540 cubic feet is how much air at standard presure and temperature (ie room temp and normal air pressure) it will hold when compressed to 6000psi at standard temerature. don't ask me why its rated like that but thats what the tank specs get listed as.
Slashdot Mirror
If it does go to court it will be interesting to see how he travels to defend it.
iirc he is on the US no fly list plus a couple of terrorist watch lists... (something to do with organisational affiliations I think)
You mean you can't run a md5 hash then base 64 encode it in your head???
;)
What kind of geek are you!!
I think thats the difference between rules that sys admins work under and procedures the sys admins create and enforce - most importantly are given the authroity to enforce.
I've rarely seen good rules come from above.
I've seen a lot of good rules/procedures come from sys admins to be signed off on by above. In the cases where management accept the recommendation as is its a good thing - where it gets rejected, or discussed by manglement and "improved" it isn't
Virtual CD works nicely
I use it for Morrowind which I'm playing at the moment
Not because I didn't buy it, I did plus the expansions, but because I absolutely hate having to put a 700Mb CD into the drive to play a game when I have a 200Gb of hard disk right there...
(and and because the original disk is getting so scratched it takes an hour to manage to do an install - I thought taking an image to be a safe precaution)
I'm a perl developer :) I certainly don't need any more obscurity!!
Having predecessors whose code I end up maintaining that had actually read PBP would be a very very good thing
(especially the 0th rule "Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live." - alas I don't know where they guy who wrote what I spent 3 months ripping to pieces to make sane lives)
Quality of sys admin is inversely proportional to the number of rules they have to work under.
The more red tape an admin has the worse the actual results they will provide
When you take a good sys admin, tell them what you want, give them a sensible budget and ask them to delvier it you will frequently get a great system.
When management try to micro manage, heap them with rules, specify particular components because they read an artical that described it as good or the vendor took them out to lunch you will get problems - lots of them.
Right now I work in a very large bank and some days I think the admins could not find their rear end with both hands and a man page - I've never met them persoanlly so no idea what they are actually like. From otehr friends I have working in banking I know how much red tape they have to work under and I suspect half of the problems the user end sees (bear in mind I'm an ex admin myself and now developer) are caused by the red tape, not by the admin.
Virtual break glass on the root password? 2 weeks aproval before changing anything, even if its trivial? These are the kind of things that can drive an admin insane.
Last company I worked for was a start up - a great place to work for a short period, the admin their was very competant on solaris, windows and linux, had a great system implemented. It didn't start going downhill til a new CEO came in that started to micromanage him (and everyone else). Thats why I got out, same for a few others, the sys admin is leaving when he can find something else he wants to do. Still even with all the hassel he had I still got great results from him, mainly because I respected his limitations, didn't break things, knew what I was doing and helped him out when he needed it. Sales staff on the other hand? With them if it wasn't explicitly on his supported list he;d tell them to take a running jump - because of all the hassel they caused breaking things (the same way repeatedly), ignoring instructions, using unsupported devices or software and then wanting it fixed - and they wondered why he didn't want to help them?
Sys admins are human like the rest of us - overly managed they are stiffled, pissed off they are unhelpful - what else would you expect?
While I'm shopping should I look for a sarcasm detector for you? Or possibly a sense of humor?
One of the main reasons for the high rates solaris admins command is where its used - the financials, most of them still use solaris (8 in a lot of cases) though I know of a few running AIX.
The financials pay far better than almost any other comparable position, the stress and pressure is a lot higher but if you can cope with that you are well compensated. (london rates are 500-600 a day right now). Commonality between unix's will not change that, those that can perform in such environments and cope with the pressure will still get those roles, those that can't or don't want to will go for different positions.
Personally I'm happy to be out of the admin game (both unix and san) - been there, done that, can still do it but prefer not to, to be honest I get bored of it. Right now I'm happy in dev, back office currently, the rates are the same or better as what the admins are and i get more variety - just my preference.
(though if you are a decent solaris admin and happy doing it any chance you want to apply here - ours seem to be able to manage to break the home directory nfs mounts on average twice a month - some how doing it on a different day for each user.... then take 2 days to get it back, though I suspect 80% of that time is the usual banking beaurocracy)
I want solaris to be different from linux!!
I want it to take a learning curve for people to transition to it!!
How else am I going to continue justifying an obscene daily rate for having solaris 8&9 skills in bank if any monkey thats run linux for a bit has the same skills?
Supply and demand is why the average solaris admin can get double what a linux or windows admin can
I for one do not want this to change!!!
Most daemons do run as root though - at first.
You the have trust in the competancy of the developers that it will allocate the resources it needs then suid to a lower priveleged user.
Admittedly thats 2 parts - one the OS being designed to let you do that.
Two, having decent developers with well tested products - I know you wont have an issue running apache as root and letting it suid - but how about some unknown piece of software you have never heard of? Will you just run it as root without thinking? Probably not.
Yes..
Until you start to sky dive
No I'm not being sarcastic I'm serious.
After sky diving regularly (to the point of being licensed and in control of yourself in the air) you start to look at the sky differently. It ceases to be just something that is there, instead its a medium that is yours, you can move with it in, you feel as though you have an extra degree of freedom - its changes your perspective.
I'm told many pilots and other aerial sports people feel the same way - ditto for divers and the water.
Resevoir Jar Jar?
;)
"Misa mistar Pink!"
"No no, yusa mistar blue!"
"No no Pink!! Misa Pink!!!"
Worth seeing for the seen where the cut BOTH of his ears off - otherwise I'd avoid it
Harking back to the good old days of high school...
We had several antiquated BBC micros in one of the classroom blocks public areas - in theory for getting work done during break but since no other classes used those machines they usually ended up having games on them for those that knew how to find (or write) them.
Bored one lunch time I typed in the same 20 or so lines of basic on each machine and with the help of a friend hit enter at the same time on each.
The screen now flashed from black to red and black, beeped every second and read "This computer will self destruct in: 5:00" counting down every second. After a bit of a giggle (ok we were 12) at how this looked we walked away and wondered who would find it.
It turned out to be one of the dinner ladies (for those that didn't have this concept in school - they are non teaching staff that wander the open building and grounds during breaks keeping an eye on things). Being about 60 or so she obviously beleived what the computers said and hit the fire bell!
One evacuation later and a short investigation of the computer screens (which if I had got the code right should have one letter on each screen - B O O M - I never did see the final result so I don't know) everyone returned to classes.
Didn't really hear much until my next IT class, at the end the teacher took me to one side - his comments were basically:
"Very nice trick, but please, don't do it again, ok?"
Was fairly obvious it was me, only the lowest years of the school were allowed in that area, I was the only one in that categry that could have done it. I do remember the teacher was trying to stop himself from grinning.
3:1
The free air con was that as the air comes out of the cylinders its going to decomress and cool down and if you pump that through your house as it does.
As I said - misuse of Charle's law gives interesting results.
The assumption was that you could store this compressed air, and that in compressing it it would get hot and that you would have to cool it - that cooling could be used to heat water and you would still have the compressed air.
The original thoughts came in between discussing the new compressed air car motor and ground source heat pumps
Getting over 100% effective efficeincy (though not actual efficiency) is obviously easy with a heat pump - 400% is feasable I beleive - though its obviously a different mechanism of effectively moving heat from one place to another - not trying to pull it out of the same process twice in different ways.
Since you are familiar with this please do just double check my assumption in discarding all of this:
If you compress 540 cubic feet of air, to 6000 psi and store it in a 1.323 cubic foot cylinder at 6000psi then the heat gain is going to be negligable? (there will be some at the pump I suspect, but the system as a whole will just balance out)
Though if anyone can demonstrate a way this would work and still half an electric bill given 3:0 peak:offpeak pricing (the measure I figured would be the only viable option for it) I'll retract the above ;)
However given the tank specs I was looking at (tanks hold 540CF of air at 6000psi) I can't see you getting the temperature differential during compression I was thinking of (my original math came up with a delta T of over 100K but I explained why that was incorrect) I can't see it happening unless you expend more energy to compress the gas to raise the heat and pressure before you cool it and I suspect (though I could be wrong) that its cheaper to just heat the water...
You would still get some cooling effect and the 64% efficency on storage is correct (and for me would still be a small saving) but to be honest I think I'll just install a heat pump.
Thank you.
You finally convinced me to check my math several times - I'm afraid this is one of those cases where back of the paper napkin science still seems close to rational enough in the cold light of morning.
Actually the math is right, perfect, spot on, not a single mistake. As is all the specs. I'd gone over them myself a few times trying to convince myself of all this (as had obviously suceeded) - still not quite believing it I had checked up on all the individual things when sober and it seemed to all add up.
I found the problem though.
One calculation in the middle based on Charle's law when the situation it was describing had variable pressure (had to rewrite the calculations from scratch to find it - probably something I should have done on sunday but never mind)
Not sure which is stranger though the fact I didn't notice the problem or the fact my brain commonly goes on tangents like this (drunk or sober) though I normally just rule out random ideas much sooner.
I do think its important to be able to admit when you are wrong - and apologise to all concerned about the general content of this thread and blame it on only 16 hours sleep total in the last 96 hours (not to mention nearly being at the end of a 12 hour shift which I thank you all for the diversion you have given me this afternoon)
There is no such thing as free energy. However air has quite a bit of energy - about 1J/gK at stp
Lowering the pressure of a gas will lower its temperature - this is how a lot of cryogenic plants work, using expansion of compressed gas as a cooling machanism (compress, it heats up, cool to room temp while under same pressure then decompress, and voila the temeprature has dropped)
Take a piston, compress the gas inside it to 6000psi, its going to get hotter.
Leave it to cool back to romm temperature but without retracting the piston (lets assume for the moment there is no leakage or air in or out - thats another matter and I'm trying to keep this simple for you) - keep it at that pressure, the gas is not going to go to a lower pressure, it can't it has no where to go.
If you think it will go to a lower pressure I'd love to hear your explanation - I could really use a good laugh!!
The "waste" heat is what you get from the air as you compress it - not from inefficiencies of the compressor, see Charle's law. You get maybe 4kWh of waste on the compressor itself (and you need to make sure it does not over heat) and the air itself is what gives you the rest, it needs to be cool enough by the time it reaches the tanks not to damage them or the valves.
The pure energy storage of this type of system? 64% efficent at best (assuming 80% efficent compressor and 80% efficient turbine/generator system - actually quite realistic for good quality systems)
You gain on the heat you pull out of the air (see air source heat pump), you also gain on cold air that replaces the power you would need for air conidtioning, so in value to you its a lot mor than just the power storage capability - as said before downside = cost + implementation complexity
See the diagram someone else linked for how its done on large scale power stations
It takes the energy from the air - same as an air source heat pump (which are available as commercial heating solutions), its not as concentrated as in the ground but its there go read up on them
No the ideal gas law says that in a closed system if you increase the pressure you will increase the temperature and via verser - there is nothing to stop you taking the energy from that energy increase and moving it elsewhere. (if what you were saying were true freezers, fridges, heat pumps or air conditioning systems would not function)
You don't cools the tanks by the way, you cool the air just after it leaves the compressor before it reaches the tanks - its still at high pressure at this point, cooling it doesn't lower the pressure.
You do not need to insulate the air tanks - the only requirment is the air going into the tanks is at a temperature within the tanks tollerance (hence cooling it while its still at pressure)
A lot of this is counter intuitive I will admit - but thats because you are trying to ignore the whole system and think only of the electic in, the compressor, the tank, and then decompressing through the turbine. The energy within the air is the other component within the system (and the fact when the air is decompressed its much cooler, ie has less energy)
Feel free to do the math, compress 10800 cubic feet of air to 6000psi, find out what temperature it now is, figure out the specific heat capacity, find out what water is heated by using the water to cool this, find out how much cooling potential you have on release, then add in the 64% (ish) efficiency you have on the actual electric storage to generation cycle, then take into account 3 times price difference of peak to off peak prices (which is what I currently pay, see economy 7 tariff on scottish power for regions in the south of england if you want proof of that)
Now the hard bit - putting that system together, safely with the right automatic controls as someone else here pointed out - hence as in my oringal post the $40k price tag (and thats being optimistic)
Oh and the discussion was on solar energy and its viability in a peak/off opeak pricing system - my comment was on the latter
my current electricity bill for an average house in the uk is 1200 pounds per year - and I don't have air con - thats 2400usd btw
Thats way above average as where I am located I'm stuck with storage heaters.
Something like this could half my electric bill plus provide air con (which I don't currently have) and would provide more hot water than I currently use.
Yet it would still take 10 years atleast to break even - as I said the problem is the cost.
It wouldn't help if everyone increased their off peak usage, but electric companies are keen to make sure their off peak usage atleast uses all the power nuclear plants can make - sicne these are effectively always on it makes sense to get the most use from the possible. For the uk the provide about 20% of total generating capacity (or atleast did in the late 90's the last time I had access to detailed figures, I'm sure you could find more current info online if you are inclined to look)
Exactly, you cannot beat the laws of thermodynamics, but you can in effect steal energy from elsewhere, same as with heat pumps
The problem with any peak time storage based system (which the discussion got to by power companies forcing people onto the peak/offpeak rates) is if it gets suffiently viable to store power when its cheap everyone will start doing it and then the peak/off peak will average out... however that averaging out on the whole would be a good thing, but economically isn't really going to happen.
Yes its an over simplification - its a post on slashdot.
The tollerance specs on the equipment required runs to several pages each, tanks, turbine generator, not to mention water and air pumps plus the control systems you would need.
You're right though - the best place to "store" energy is in the grid -especially if you can get a decent sell back price from them.
As you say water storage for temerpature is also pretty good (but then thats the other side of this system for home use, you store the heat generated by compression into water)
Net the air compression storage by itself is worse than batteries - you dont have the economies of scale large power plants that use this do. It becomes useful in the side effects of hot water and cold air.
But personally I'd rather go for a wind turbine, a ground source heat pump and cutting down usage where I can (I'm in the uk so solar isn't too much use)
No you pull the energy out of the heat in the air.
Check it - take 10800 cubic feet of air at stp, comrpess it to 6000psi - keeping it at the same pressure cool it with water, now figure out how many joules has gone into that water and how much that water temperature has now gone up.
You still have the compressed air in the tank - which gives you both cool air on demand and its stored potential energy (ie the compressed air will drive a turbine)
Depend son the area - UK economy 7 tariff is 3.5p/unit off peak and 11p/unit peak - atleast where I am.
Also that 540 cubic feet is how much air at standard presure and temperature (ie room temp and normal air pressure) it will hold when compressed to 6000psi at standard temerature. don't ask me why its rated like that but thats what the tank specs get listed as.