Cooling down without Air Conditioners

[ShadowHM]

I just read an interesting article in my local newspaper, about the first residential building that will make use of a new (to Toronto) technology called Deep Lake Water Cooling to replace air conditioners. I am tickled to see a major developer jumping onto this bandwagon, even if it is only for one building, as yet.

http://www.thestar.com/NASApp/cs/ContentSe...d=1064355913280

The overall Deep Lake Water Cooling project has been on the go for some time, after successfully jumping the environmental assessment hurdles. It will be serving about 100 office towers once up and running (sometime next year). The forecasted cost reductions are substantial, even before the environmental benefits are considered.

More information about the project can be found here.

http://www.enwave.com/enwave/view.asp?/tec...chnology/energy

However, Toronto is not the first on the block for this. According to Scientific American, it has been used by Stockholm since 1995. It certainly is not for every city. Occhi in Texas would be SOL on this one, for example. But there are other places who have high air conditioning loads that are beside deep cold waters.


http://www.sciam.com/article.cfm?articleID...B81809EC588EF21

[channel1]

Interesting, and I'm sure that it would be environmentally benign on a small scale. I would question the effect on the lake's ecosystem if a large number of facilities began to alter the natural deep water temperature significantly.

Another potential large scale problem would be excessive evaporation from the lake, especially in hot weather when there is already a lot of evaporation naturally. Of course, in hotter weather the buildings will be pumping even more heat into the lake.

Another system that has been around for a while is the water furnace ( Water Furnace FAQ ). The principle is similar, but the heat is transferred to and from ground water. Proximity to open water is not an issue, and the potential of direct impact on obvious species (i.e. fish) is less. That isn't to say that there wouldn't be an impact on the ecosystem, but the way that the water furnace works tends to distribute the temperature influence over a larger area.

-rcv-

[DeeBye]

Interesting, and I'm sure that it would be environmentally benign on a small scale. I would question the effect on the lake's ecosystem if a large number of facilities began to alter the natural deep water temperature significantly.

That was my first thought too. I don't think that would be much of an issue, though, considering how absolutely huge the Great Lakes are. It would take an awful lot of these deep water heat exchangers to alter the overall water temperature to any significant degree.

I haven't done the math, but consider how much energy would be required to raise the temperature of 1,640 cubic kilometers of water by even one degree Celsius.

Also, water is constantly flowing from one Great Lake to the next -- eventually emptying out to the St. Lawrence River and out into the Atlantic ocean. The system is always refreshing itself, albeit slowly (lots of volume is moved, but not a lot as a percentage of the system's total volume). There is always fresh cold water moving in.

I don't think we have to worry about this issue. At least, not for quite a long time.


-DeeBye

[ShadowHM]

I would question the effect on the lake's ecosystem if a large number of facilities began to alter the natural deep water temperature significantly.

I wondered about where the warmed up water goes myself. However, it is being fed into the city's water treatment system for general use by the city. Since the city would be drawing water from the lake in any case, it seemed like a minimal loss to the lake's ecosystem to have it drawn from the colder section rather than a shallower level.

[Bob]

I've tried to look for an alternative source of data, but every single site has taken their data from the same source, which lists the volume as 1.640 KM^3. That's no use. You need the mass of the water in kilogrammes to work out how much energy is needed

ah... found a convertor
1 cubic KM = 1 x 10^12 L
= 1 x 10^12 Kg

1 x 10^12 x 1.640 = 1.64 x 10^12 Kg

change in energy = Specific heat capacity x mass of substance x temperature change in Kelvin

SHC of water = 4200 J Kg^-1 K^-1

E = 4200 x 1.64 x 10^12 x 1

E = 6.888 x 10 ^15 J

or 6.888 PJ

in comparison, you average electric lightbulb (100W) uses 360,000 J per hour, or 8,640,000 J per day

so it would take 797,222,222 days for an electric lightbulb to use that much energy, or 2,182,675.5 years. Unless they have a way of pumping over 2 million lightbulb years of energy into the lake in a short time, I don't think we can worry about the temerature change much.

Of course, all the above doesn't take into account the loss of temperature to evaporation, the air and the land around.

-Bob

[DeeBye]

I've tried to look for an alternative source of data, but every single site has taken their data from the same source, which lists the volume as 1.640 KM^3. That's no use. You need the mass of the water in kilogrammes to work out how much energy is needed

1 liter of water weighs 1 kilogram. Yay metric system :)

-DeeBye

[kandrathe]

The dryer areas of the planet (<50% humidity on average) may be able to get some relief from an evaporative cooler(also called a swamp cooler). They use much less energy than traditional compressor models.

[channel1]

The problem is, the lake isn't a pipe that has a consistent flow; nor is it a superconductor that has a practically instant transfer of energy across it's volume.

The water in proximity to the heat exchangers will get noticeably warmer. Some organisms will not do well in the area of warmer water, while others will thrive. An example would be the types of brown and blue algae, which like warmer water and will not get natural competition from the green algae that prefer areas with more light in the shallower water. You could get algae collecting on the heat exchanger, and the brown and especially blue algae produce toxic compounds.

Although this system will at first look like an economical alternative, much of the savings will need to go toward studying the effects of the small-scale installations before it can be allowed to expand.

I do think the water furnace system, using ground water, has greater potential. The temperature of ground water tends to stay more consistent than lake water over the course of the year. As a result, the water furnace can be used both for heating and cooling. Toronto is near the limit of the practical range for the water furnace, however. Down where I am (Windsor-London area), the water furnaces are quite effective. As conventional energy costs rise, the time to break even on the cost of installation of a water furnace will be reduced.

I should note that the water furnace is not a great option in a high-density urban area. If I recall correctly, the area required for a water furnace is about ten times the area being heated. In other words, a 300 square metre building needs about a 3,000 square metre area for the water furnace tubing. That's okay if you have a big back yard, but doesn't help most structures in a city. Burying the tubing under pavement isn't a good option, since pavement does not insulate well. You need to go quite a bit deeper under pavement to get under the frost line.

-rcv-

[--Pete]

Hi,

I really don't care enough about this issue to check your numbers, so I'll just pick up where you left off.

so it would take 797,222,222 days for an electric lightbulb to use that much energy, or 2,182,675.5 years. Unless they have a way of pumping over 2 million lightbulb years of energy into the lake in a short time, I don't think we can worry about the temerature change much.

Let's look at a typical office building filled with typical office workers: Say 10,000 sq ft per floor, 6 floors. Not too big, not too small. Usual allocation is about 35 sq ft per person, but that doesn't include the public areas, etc. So let's use 50 sq ft per person as more typical. That's 1200 people in that one building.. Now, each person has about one light, one computer and person themselves. That's (very roughly) about 3 light bulbs. That gives us about 3600 light bulbs in that one office building. So, taking the ratio gives us 600 years for that one degree change. Now, consider twenty such buildings in each of ten cities around one lake and we're down to 3 years and the problem is real.

There was a bad SciFi movie once where a microscopic organism was consuming energy. The scenes flashed from the lab where it was being studied to a view of the city's lights dimming and back to the lab. White coat says, "Wow. Ten billion ergs." I bust out laughing. Ten billion, yep that's a big number. And ten million ergs is about one peanut butter and jelly sandwich. Hardly enough to dim a city :)

--Pete

[Occhidiangela]

The Water Furnace idea strikes me as being closely linked to the management of an aquifer. That topic has been of considerable interest here in Texas for some time, particuarly as most aquifers in this state have been in a slow decline for a few decades.

I suppose my question would be on the best water removal method: When the ground water absorbs the heat, does the water then "naturally" filter back down into the ground, is it sent "downstream" with river flow, is it put to some other use, or is it pumped back into the ground? The site suggests a return well, depending on the system chosen, so I suppose that the conductive heat transfer with the ground itself should, in time, return the water to the temperature of the local underwater source. I find it odd that the site almost Poo Poo's the problem of aquifer management, but it may be aimed at northern and central latitudes.

Your comment on the problems with using such a system in a city strike me as a part of the challenge. The other challenge is in the competing uses for ground water for other infrastructure, or for example, agricultural needs.

Neat link in any case. :)

My townhouse in Virginai Beach, mid 80's, had a heat pump, and all was well until January rolled around one year with temps in the single digits. My heating bill sky rocketed. That little system was not built for such extremes. :(

[Bob]

I'm not trying to impress you with big numbers, but if I used any different numbers it'd be wrong :blink:

The numbers I gave are how much energy would have to be transferred to increase that temperature, which is quite different to the ammount of energy used by an office. I'll assume you're familiar with diagrams showing how much energy going into something comes out as what. A lightbulb, is 95% inefficient (or so my physics teacher says), so, no arguing, most of that energy going in is being pumped out as heat to be dispelled somehow, however, I'm talking about a conventional lightbulb, not a flourescent tube similar to what is used in the majority of offices, they are much more efficient. But a computer, ok, so AMD chips pump out a lot of heat, but not everything becomes heat, how much of a monitor comes out as heat, and how much as light?, I'd need to get hold of hard numbers to see how much of it is heat.

Now, the dissipation, not all of it has to go through this cooling, since this isn't air conditioning, the windows don't have to be shut, buildings lose a lot of heat through ceilings and walls too. Ok, so the second law of thermodynaics says that it can't get cooler outside than in just passing the heat through walls, only to an equal temperature, so if you want it cooler, you've only got to take it down from the equilibrium temperature.
You also have to keep the people warm, if it's so hot that you need cooling, then there won't be heating on, so some energy could get absorbed by the people and keeping just about everything else in there at a constant temperature.

So, 3 years to change, that's assuming that no energy whatsoever leaves the lakes, as someone has already mentioned, the water flows out of Lake Ontario, as I've already mentioned, heat will conduct and convect out of the water. And what of winter? when the buildings won't have to be cooled so much, but the weather will be cooler, sapping the heat back out of the lakes, I hear that the winters get VERY cold around there. The total cycle will take longer and that's if it ever happens at all.

What might have been a better idea is if they found some way to use it to heat water for the city or another heat pump can be used to turn that heat into electricity B)

It can't be a totally stupid idea, otherwise they wouldn't be trying it. (oh, wait, knowing governments nowadays...). Perhaps they plan to see what effects it has and then use it on larger lakes, where it would take even longer

however, that is a very good point that hadden't really crossed my mind. Oh and thankyou for the mind workout, I won't be forgetting thermal physics anytime soon.

-Bob

[--Pete]

Hi,

The numbers I gave are how much energy would have to be transferred to increase that temperature, which is quite different to the ammount of energy used by an office.

From the post I replied to:

Unless they have a way of pumping over 2 million lightbulb years of energy into the lake in a short time, I don't think we can worry about the temerature change much.

Had you stuck with just the numbers, I would have ignored it. The conclusion you came to (in bold above) is what I'm attacking. You saw a big number (2 million light bulbs) and were impressed. You tacitly assumed that they couldn't get that many "lightbulbs" hooked up through HVAC systems to a lake. I showed that it could easily be done and that your assumption was poor.

As to the rest of your quibbles, it doesn't matter. We're not talking precise numbers, we're talking reasonable approximations. A person puts out about the same amount of heat as a 60 to 100 watt light bulb, a computer with monitor puts out about the same as one or two such bulbs, a person at a workspace has two or more four foot fluorescent bulbs overhead and typically one or more "task" lights. Plus there are copiers, printers, coffee pots, etc. How accurate is my estimate? Probably a factor of 5 one way or the other, good enough for this discussion.

Oh, and *all* the energy used eventually turns into heat. That's what the second law of thermodynamics is all about. And most of it turns to heat pretty fast.

Now, the dissipation, . . .

Bah. Again we are talking averages. Sure, if you want the temperature to be between 70 and 72F and it happens to be 71F outside, you don't need heating or air-conditioning. (That's actually a simplification. The actual outside temperature that gives optimal inside conditions is determined by how much heat is being produced in the building and how rapidly that heat can be removed through windows, fans, ducts and all that. But the principle still applies.) So, what fraction of the time will this happen? In Pullman Washington, the summer average temperature was an "ideal" 70F -- until you realized that this was the result of 90F degree days and 50F degree nights. :)

So, 3 years to change, that's assuming that no energy whatsoever leaves the lakes, as someone has already mentioned, the water flows out of Lake Ontario, as I've already mentioned, heat will conduct and convect out of the water. And what of winter? when the buildings won't have to be cooled so much, but the weather will be cooler, sapping the heat back out of the lakes, the total cycle will take longer and that's if it ever happens at all.

Again, bah. We're looking at order of magnitude calculations here. These are smaller effects, they would change an exact result but have little effect on the approximation used. Second, thermodynamics rears its ugly head again. Whether we're talking of changing the overall temperature of the lake by .03 or 3 degrees per year is not the issue. The issue is that we are changing the temperature by an amount that is considerable over a short time. As to the turnover of the water, what percentage of the water is replaced per year? That, to a first approximation, is the amount of excess heat being carried away. So, if it is less than 20% of the total, it is of no importance in a first order calculation.

What might have been a better idea is if they found some way to use it to heat water for the city or another heat pump can be used to turn that heat into electricity

In looking at all solutions of this type, the energy cost of implementing the measures must be considered as part of the total. For instance, say we have a fan motor that uses 1000 kW-hr per year. Let's assume that a newer model is more efficient and will do the job for 950. Let's further say that the expected life of the motor is ten years. So, unless the new motor can be manufactured (including mining, transportation, etc.) for less than 500 kW-hr, it is an energy *loss* to replace it -- the energy costs are simply being passed back up the line. Usually it is the monetary costs that are considered, but they (very) roughly are commensurate.

It can't be a totally stupid idea, otherwise they wouldn't be trying it.

Yes, it could. Sometimes the only choices are between stupid ideas. Often because the "smart" idea cannot be implemented for political or social reasons. We are in the environmental situation that we are because our ability to reduce infant mortality outstripped our attitudes about having children. Thus the huge families of the late nineteenth and early twentieth century. Before that, nature took care of family size. Now, in many parts of the world, society has finally caught on (however, it seems that the regions that can least afford overpopulation are the ones that contribute to it the most).

"Totally stupid"? How about harvesting old growth timber at the rate of 15 to 20% a year when the replacement rate is about 0.2% a year? How about destroying the fishing grounds that are your livelihood by overfishing? How about moving 50 miles from your place of work and then burning 500 gallons of gas a year (not to mention 700 hours) getting to and from work? People do a lot of "totally stupid" things because of factors that they overlook, ignore, or that really change the "stupidity" of what they are doing.

The final analysis: the population of an area is growing, thus more living and working spaces are required. They need to have some form of temperature control to be comfortable. What solutions are they and how much does each hurt the environment? There are no good solutions, just bad and worse.

--Pete

[ShadowHM]

What might have been a better idea is if they found some way to use it to heat water for the city or another heat pump can be used to turn that heat into electricity

That same company does offer steam heating for water-based heating of buildings in winter. Some of the same savings for the corporate users of those services apply, although the company does use electricity to create the steam.

Perhaps they plan to see what effects it has and then use it on larger lakes, where it would take even longer.

Lake Ontario is the 15th largest lake on the planet. And there are not a lot of big cities on many of the larger ones. (None on Great Bear Lake or Great Slave Lake, for example.) This is not a research effort. This is an attempt to provide, as Pete put it, a lesser evil in terms of delivering cooling to those of us who feel they cannot tolerate the normal range of summer temperatures for our climate. That would include a lot of North Americans, no?

[kandrathe]

One point worth noting; Many modern office building have atrocious insulation, and especially the glass which has become very popular in modern office buildings. The microcomputer revolution has added a little 5 watt furnace to every cubical. So beyond lights and the heat of the humans, add the inefficient insulation and thousands of little CPU furnaces. The ecological point is that to solve this excess of greed expressed as heat, we may jeopardize the ecosystem of the lake. My opinion is that much of that heat could be reflected from the insides of these buildings with better insulated glass and polarizing filters. More efforts could be made to reduce the energy consumption of offices in general. It is sad to have to pay for energy twice, once to heat it, and once to cool it.

<devils advocate>

But, Bob has some valid counterpoints. Because of their frigidity, these lakes support very little life anyway. I dive in Superior, which in the height of summer even at the surface hardly breaks 60F. At 100 ft, the temperature is barely above freezing. (I see you asking why, why in hell would you do that?) There are very few fresh water lakes with 100+ feet of visibility. Humans have trashed these lakes for 100+ years, over fishing them, spewing sewage, taconite tailings, industrial pollutants, and god knows what all else into them. So, like lake Erie, whatever ecosystem they may have once had has most likely already been trashed and whatever fragile life they held has been disrupted. So would polluting them with heat hurt them anymore than they already have been? Maybe it would help them. The transplanted exotic eels and zebra mussels might thrive even better in warmer lakes.

</devils advocate>

[ShadowHM]

&nbsp; I dive in Superior, which in the height of summer even at the surface hardly breaks 60F.&nbsp; At 100 ft, the temperature is barely above freezing.&nbsp;

I am gaping with admiration for your fortitude. I learned to scuba up in Smooth Rock Falls, Ontario and we had to delay our open water test, due to the lakes still being ice-covered when the course was over.

It was damned cold getting into that lake after the ice went out. I hesitated so long at the buddy breathing due to reluctance to let any more of that freezing cold stuff touch my face that I nearly failed the exam.

I quit scuba diving many years ago, due to lack of partners, and confine myself to snorkelling in Lake Huron now. And it is still damned cold below the first thermocline.

Congratulations for sticking it out and just doing it.

[kandrathe]

Heh. It certainly adds some stress to the diving. We fill our wet suits with hot water we bring to the dive site from a "cooler". I'm one of the rare wet suit divers that does cold water diving. Most of the regulars use dry suits. My favorite diving instructor is a rescue/recovery diver so I end up doing many dives in places that most people would not find comfortable. I guess I like the technical challenge, but diving the reefs in the tropics is still the iceing on the cake.

[ShadowHM]

Rescue / Recovery has got to be the scariest of all diving.

I participated only once in such an endeavour, and it was downright claustrophobic and spooky. Never again !

We were trying to recover a big (20 ton) bulldozer that had slid off its barge in a windstorm on the Abitibi River upstream from the power dam at Island Falls.

Two operators were on the barge. One was in hospital with crushed legs and not available, and the other told us approximately where it went down. You would think a bulldozer of that size would not be hard to find, eh?

But the water upstream from a big power dam is full of drowned forest, lying all directions just above the bottom. The bulldozer was big enough to have pushed them all aside before it sank in the bottom silt and let them fall back over it. The water was murky. About 10 feet down into a 60 foot dive there was zero visibility. We did a grid search pattern, going down every five feet.

We had to follow the line to the bottom, grope around in the muck for anything hard and metallic and then come up and repeat. The trees were floating anywhere from the bottom to ten feet up, and they tangled in our gear constantly. It was horrible to feel yourself being poked or tangled by invisible branches and stay focused on the job at hand.

After three days, we called off the search. Go figure - the uninjured guy was right out to lunch in his estimation of the location of the accident. When the other guy finally got out of the hospital he was able to pinpoint the location (about a mile from where we searched) immediately and the bulldozer was recovered.

That incident gave me a healthy respect for anyone who does search and recovery for a living.

Edit: where is my memory going? Island Falls, not Abitibi Canyon!

[Guest]

If our society actually cared about the envirement we would be using ammonia system for much of our cooling.

They are more efficient, and ammonia is envirmentally friendy. It doesnt smell nice if you have a leak, but its not really dangerous.

If large chemical companies werent making Freon etc we probably would be now using ammonia for a large percentage our cooling rather than in a few isolated warehouses.

[Occhidiangela]

IIRC, that was used in early refrigeration units, like back in the 1800's. (If memory serves, Australian beef and lamb was shipped to Europe using an early form of this cooling system)

Ammonia has its own hazards insofar as handling, spillage, and as an irritant to humans who are unlucky enough to get a bunch of it on them. As a hazardous material, it is not the worst, nor is it the best, material to work with.

IIRC, Freon is more efficient at removing heat. It's other advantage, from a practical point of view, is that if it leaks, it "disappears" via evaporation (yes, not the best thing for the air, I agree with you there) whereas if ammonia leaks, that can create secondary harmful effects to persons or animals in the effected area.

My new car, 2000 model, does not use freon in its air conditioner. So, at least the Greens and the EPA have been able to see some progress.

[kandrathe]

To me, that sounds like fun! On my first zero visibility dive I found a stolen GMC suv. The hardest dives are anything under ice and looking for people, especially kids.