No, if we're "storing cold", it's an "energy vacuum" or an "unenergy storage" or an "energy "unstorage" or something.
People like this drastically increase Newton's kinetic energy...
Ice Energy, with its fiendishly simple Ice Bear product has got together with data centre air-conditioning company Data Aire to combine Ice Bear with its Data Temp cooling systems. The idea is to use cheap off-peak energy at night to freeze a tank of water (or "distributed energy storage system"), then use that great block of …
I can understand the concept of using cheap energy at night and storing it as ice to save money during the day. (Electricity is cheaper at night). How does using this big block make the process more energy efficient though? Surely the same energy is needed to provide the cold?
2 years ago there were suggestions of doing something a bit similar on London's tubes - big tank under the train which would be cooled when the train's above ground and then melted underground, extracting the heat from the carriages.
At first glance, it seems perfectly reasonable; it'll be good if it works.
Except that all those 'leccy cars, vans, buses and such charging overnight in the coming years will take care of this for them.
Unless the sort of thing in the article really takes off with the heavy consumers as well, in which case we'll still have a peak demand problem, but it'll be overnight and Sod's law will have had its revenge.
Well, the most obvious thing is that the outside temperature is much colder at night. As such, the thermodynamic efficiency of the ice block creator is much much higher than an air-con unit trying to extract heat from a building at the hottest point of the day. You rely on the ice block not having much temperature loss during the day - but with good insulation that shouldn't be a problem.
I guess this must be new, because when it first appeared was 'pre internet' and so is deemed to have never existed.
30 years ago, I knew farmers who had something similar installed for chilling milk - nothing more than a box of electronics that simply ran the chillers harder at night to build up ice in the tank so they could run less during the day. Oh the joys of cheap rate leccy !
As for efficiency, I can see two reasons it could be more efficient.
1) It will be cooler outside at night, and so you are pumping heat over a smaller temperature difference. If the equipment is optimised for it, then this will get you more cooling for less leccy, or the same cooling for more leccy.
2) You can run the equipment at optimum efficiency, rather than to the immediate load. By eliminating the need to run chiller plant at part load (to match actual load), then you may be able to gain efficiency savings there.
A fun little idea! Two questions:
(1) The night leccy rates are lower because capacity exists and the demand is lower. If everyone uses this, then the demand (and the prices) rise and wipe out the savings. Cool idea - but only if it doesn't sell well.
(2) When a worldfull of leccy SUVs are plugged in for the night ... will there be enough juice left (at a decent rate) to mix up these server rack martinis?
Shaken, not stirred.
To all you people who are popping off about "It is just cheaper, not more efficient!", you might want to learn a bit about how a refrigeration system works before you open your mouth. It makes you look ignorant (or possibly just exposes what you are...)
The concept you are missing is called "Delta T". Heat flows from from hot to cold (that delta T or DT going forward) and it is pretty linear: the greater the DT, the greater the rate of heat flow.
Your standard refrigeration system (car AC, refrigerator, freezer, refrigerated air home cooling, etc) uses this principle twice: the first time, it heats the refrigerate significantly by compressing it, then it dumps the excess energy by allowing it to flow to the outside air (normally). The refrigerant is then cooled significantly by expanding it back to a gas. This cold refrigerant is now much cooler than air it is cooling, so the heat flows from the air (inside your car, your refrigerator or house) to the refrigerant which heats the refrigerant back up while cooling off what you are cooling.
Here is the rub: it takes ENERGY to compress that gas to make it hotter than the outside outside sink. The hotter your sink is, the MORE energy it takes to make the refrigeration system work. When your sink is actually COOLER than your target temperature for what you are conditioning, you can move that energy with much less energy consumption.
One way to do this is to find a cooler heat sink. Geotherm systems do this by dumping the excess energy to the ground (via buried tubes) or to water sources like rivers or lakes. Trying to keep a house at 21C when it is 38C outside is MUCH easier if you are trying to dump the excess heat to a sink that is 13C. Running the AC system at night when it is only 18C (for example) is WAY better than trying to dump the heat to a 38C outside air even if it isn't quite as effective as dumping it to 13C ground.
So yes, there ARE real ENERGY savings by doing the heat dumping at night. The fact that you can also do it using CHEAPER electricity is also a very nice bonus.
Thanks Simon for pointing out the effects of a cooler low temp thermal reservoiur (outside) at night. Everyone seems to ignore that point and concentrate on the cheaper electricity.
Surprised that they're bothering with water though... Most decent-sized systems I've seen to do this sort of thing tend to use spheres of wax encased in plastic. You can easily tune the freezing point of the wax, so you get the phase change storage, and it also tends to expand and contract a whole lot less on freezing, which would make designing the low temp tank a lot easier...
If you've got to chill the water all the way to 0 deg C, then the aircon unit has to handle a much higher delta-T, which would lower effiency. Much better to have a phase change at just below room temperature, so you don't have to get drastically lower temperatures to store your cold.
...Surely this system would therefore require nearly double the capacity on the air conditioner?
I assume that it will operate twice as hard during the night, thus eliminating the need for daytime operation of the compressors. But, surely overnight the system will be chilling for tomorrow, AND will be coping with the continued operation of the data centre. Ok, sure, loading on the centre might fall, and also the efficiency of the cooling cycle (they're far more efficient across small temperature differences) will make calculating this difficult, but it's a consideration!
To those offering that the off peak power might become on peak; surely the trick is to use smart metering and control, allowing excess power to be used whenever it's there; so that even if the night time becomes the new peak, the load could spread out a bit.
I'm working for a big HVAC company, and we're using this system for more than 30 years.
So new??? Marketing bulls... at it best!
You can't use that in every scenario.
Allmost all the office buidlings are cooled, and maybe all have temperature controlled servers rooms.
In some cases, NH3 cooling machines are used, and you can't stop them because if the ammoniac stands still it will attack the joints leading to leakage.
So as the machine is working around the clock, we are using it to store ice to cool the building in the start of the occupancy period (around 9h00 or 10h00 am) to reduce the overall consumption.
The server rooms are also cooled around the clock, but as you go home at the end of the day, the "comfort" energy consumption of the office is dropping. If the equipement is calibrated for producing a minimum of 10.000 KwH (tehoric value) of frigory but the consumption on the IT side is 5.000 KwH, we use the 5.000 KwH to stock energy under the form of...ice,bingo, energy savings.Some of those "ice" vaults (not real ice water, as it freezes and expands) are as wide as a tennis court with a depth of 2 meters.
But in no way could you solely rely on ice vault to cool you office/data/watheveryouthink rooms.
It's just to use otherwise lost energy (thus sparing) or in some cases have a backup cooling supply. Sometimes, I wish that all of you office people start to learn what's happening behind the scene, to assure your comfort is not as simple as to "operating a fridge" or to turn the heater on ;)
It's also about very, very expensive daytime electricity. especially in places like California. That's why the utilities are paying subsidies - these "negawatts" are cheaper than building new powerplants to produce megawatts at times of peak demand.
"Cheap" off-peak electricity is only a few cents cheaper than "ordinary" electricity, but expensive peak electricity is dollars more expensive.
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