Cooling Toronto Using Lake Ontario 698
An anonymous reader writes "Air cooled by the frigid waters deep in Lake Ontario started bringing relief to buildings in downtown Toronto on Tuesday after the valves were symbolically opened on the multi-million-dollar project. The company says that they have the capacity to air condition 100 office buildings or 8,000 homes - the equivalent of 32 million square feet of building space. They note that the cooling system reduces energy usage, freeing up megawatts from the Ontario's electrical grid, minimizes ozone-depleting refrigerants and reduces the amount of carbon dioxide entering the air."
Re:Just two questions (Score:5, Informative)
Q2 is apparently answered in the article. Approx 25% of the energy requirements for electrical air con.
Re:Environmental effects (Score:5, Informative)
"...Brought to the John St. Pumping Station, the water's cold will be extracted and used to lower the temperature in downtown buildings. The water will then be treated and enter the city's drinking supply...."
So might be a double whammy, the water isn't directly injected into the lake again.
Re:Environmental effects (Score:5, Informative)
Re:Environmental effects (Score:3, Informative)
http://www.enwave.com/enwave/view.asp?/dlw
Will DLWC warm up Lake Ontario?
* No. Enwave is not extracting from Lake Ontario's water and then directing 'warmer' water back to the lake. The DLWC project has been designed to draw very cold lake water - colder than what the City needs for its water supply - from Lake Ontario. Enwave will extract the extra coldness before the water is sent into the usual water supply system. Water from Lake Ontario is being used for two different purposes: a cooling alternative for Enwave and a drinking water source for Toronto and York citizens.
Of course, what would you expect them to say?
Re:Environmental effects (Score:5, Informative)
-Toronto cools off using Lake Ontario waters [greatlakesdirectory.org]
The answer is in the article. (Score:5, Informative)
that feeds from the bottom of the lake to cool down
a closed loop system, which is then used to cool down the offices/homes. No warm water is fed back into the lake. So the lake should not heat up at all.
The lake is NOT warming up ! (Score:5, Informative)
Look at the diagram on http://www.enwave.com/enwave/dlwc/ They warm up the city's drinking water by a few degrees.
A
The London Underground is also doing this (Score:5, Informative)
Here's the BBC's story about it [bbc.co.uk].
And more importantly, Alec Baldwin was there (Score:3, Informative)
The Toronto Star's coverage [thestar.com] has more info about Alec Baldwin's participation in the launch of the Deep Lake Water Cooling system:
Re:Environmental effects (Score:3, Informative)
When the pre-heated warmer water from nearer the surface falls down to replace the cold water that is removed, what happens? Does it say warmer, or does it cool down?
Another link (Score:5, Informative)
No registration required;
http://www.cbc.ca/story/canada/national/2004/08
water warming? (Score:2, Informative)
Re:Messing with lakes: NOT a good idea (Score:5, Informative)
Lakes 'turn over' like this when there has been long-term stratification of the water. Stratification occurs when a layer of warm, less dense, water forms over the colder, denser, lower layers. This is stable since the heat of the sun reinforces the stratification. Only a seasonal reduction in sunlight, or strong winds, can mix the layers.
Lake Nyos is in a tropical area where there is a permanent, marked stratication due to year-round abundant sunlight. Since mixing of layers is so rare, hug amounts of gas can accumulate in lower layers. This is dangerous should something trigger a rapid breakdown of the stratification - such as the landslide in Nyos.
In temperate areas stratification is confined to the summer, only then is there sufficient sunlight. In other seasons stratification breaks down and mixing occurs such that a potentially dangerous build up of gas is not possible.
Re:Messing with lakes: NOT a good idea (Score:5, Informative)
Re:Environmental effects (Score:3, Informative)
In practice, one will see a small tempretaure increase in the vicinity of the pipelines, but they're probably ecologically stuffed areas anyway, with various additional current effects, etc. The overall volume affected will be very small in relation to the lake itself and thus the total impact is not significant. The natural seasonal cooling cycle should ensure that there is always cold water available (until global warming destroys the seasonal cycle, anyway :) ).
Re:The lake WILL warm up (Score:1, Informative)
Cool, but not new (Score:2, Informative)
For example Fortum [fortum.se] (Energy company in Sweden and Finland).
Re:water warming? (Score:2, Informative)
Of course if it's just a tiny fraction of the cold water that gets extracted there might be no effect at all.
Actually, water DOES flow down hill (Score:5, Informative)
As a grandson of a plumber I can confirm that the water does eventually end up back in the lake. Rule #1 of plumbing ...water flows down hill.
The beauty of this implementation is that the incremental warming of the water may actually further save energy if slightly warmer water comes into water heaters. From a thermodynamic standpoint this looks like a very large geothermal system. The economies of scale may make it quite cost effective too.
Do building ACs use refrigerants? (Score:3, Informative)
I know that "real" portable cooling units have no refrigerants (the corp I work for resells some).
I can see the savings from power, but I still don't like the idea of sucking cold water from the bottom of a lake. It would seem to me you could upset the balance and possibly cause the lake to flip thereby releasing tons on CO2 - something which happened in Africa, which did kill a lot of people.
Re:Environmental effects (Score:5, Informative)
I'm annoyed by all this hysterical nonsense over environmental effects on the lake. Apart from the fact that the heat input is trivial given the size of the lake (do you know what the heat capacity of 393 cubic miles of water is?) People think the lake is not some finite reservoir of coolness - no, it's a heat store, it cools down in the winter people! Consider the hitorical effect of tens of thouands of summers if that were not true.
In all this ranting, the very real envirnoemental benfits of reducing energy consumption and CO2 emissions get lost in the noise. I'd have expected better from the so-called technically literate.
Re:Nice :) (Score:2, Informative)
Re:Environmental effects (Score:4, Informative)
Very slightly if the water is fed back into the lake. However water has a high specific heat capacity around 4.2kJ is required to raise one litre of water by 1 degree celsius. The water in this case is comming from a very large lake, so it would take a huge amount of energy input to change the temperature of the lake by any noticable amount.
There also exist methods of extracting heat from rivers and lakes for heating. So possibly these could be used in winter.
What are the envirnmental effects of this?
Most likely considerably less than dumping heat in to the atmosphere, which is how conventional air conditioning works.
Re:Environmental effects (Score:5, Informative)
Re:The lake WILL warm up (Score:2, Informative)
Think first!
Re:The lake WILL warm up (Score:4, Informative)
Did no one RTFA???
You've already extracted from the exact same source of water for decades, for use as drinking water. This just raises the temperature of your drinking water by about 10C, with a net "gain" derived from reducing AC costs to the city.
So yes, you can technically say that removing water from the coldest part of the lake raises the average temperature. But to turn that into "we should not be doing this" ignores the reality of the situation. This results in less energy consumption overall, a good result no matter how you look at the situation.
Re:It's a GREAT Lake (Score:3, Informative)
Re:Environmental effects (Score:2, Informative)
Needless to say people felt pretty strongly both for [cornell.edu] and against [cldf.org] the project.
Re:I was going to ask about that... (Score:2, Informative)
Re:Just two questions (Score:5, Informative)
1 - Lake Ontario doesn't freeze over, but it does have some surface ice in midwinter. Ice implies a surface temp at or below 0 degrees c. Right?
2 - Having lived next to another sizeable lake (Lake Champlain, which typically does freeze over), and as an EXPERT in hydrodynamic modelling, I can assure you that that niggling little physics detail about water having maximum density at... (drum roll) 4 degrees C is accurate. However, twice a year, lakes like Ontario have all their water churned about as ambient average temp falls below 4 degrees C, then as ambient temp rises above 4 c. Wierd, but true. Frankly, seiche's are wierder [wisc.edu].
3 - So, as winter gets cold enough, any water not AT 4 degrees C rolls to the surface, where it is... say it with me... chilled by the Toronto winters. Before any ice is made, everything in the lake chills to 4 degrees C (this is my biggest oversimplification here, since inversion layers can exist in large water bodies. It doesn't matter in the overall calcs to follow, since all I was interested in showing is the mechanics for recharge of the cold zone).
4 - The thermal mass of Lake Ontario (one site says 86 m average depth, x 19,000 km^2 in area... 19,000,000,000 x 86 x 100 ^3 cm^3 per meter x 1 degree c x 0.0039683 btu's per calorie x
The Fact Sheet on Enwave's site [enwave.com] says they're gonna free up 59 megawatts. Now, I should be able to disregard a part of this as an efficiency improvement (electricity for cooling is gawdawfully inefficient, compared to non-compressive heat exchangers like this'll use), but I'll eat the inefficiency because that's the nice guy I am. 59 x 24 x 365 (megawatt-years to megawatt-hours) gets us *finally* to matching units. If I haven't completely bolluxed the calculation, we're looking at a capability of handling 3673 of these facilities. Or, the temp of Lake O going up 1/3673 of a degree.
Oh. Yay. The little fishies aren't even going to notice this. In fact, there's room for exporting this capability and if we're willing to warm Lake O by a few degrees I think it'd take care of the AC demands of most of North America, if them clever Canadians can just figure out a way to export this.
When she's working hard, the sun 'wastes' enough energy warming up dirt and water around the world to fuel our needs a thousandfold over. When she's not paying attention (at the poles, nights and winters), earth's radiating it off like gangbusters.
The risk of us boogering up our surroundings when we do BIG things is a valid one. But not here, not yet.
We've reached the point where we're influencing the world in several spots: cfc's, pesticides, acid rain, particulate emissions, garbage, animal populations, etc. etc. etc.
But this isn't one of them. As a side joke, I bet there are a few million Toronto residents that'd be more than happy to let the thermal average temp of Lake O go up 30 degrees, just for the lake-effect warmth it'd impart on their town each winter and the ability to swim without turning blue in midsummer. Back during a nasty winter ('93), a favorite bumper sticker of mine was 'Another Vermonter *for* global warming'.
Rock on Toronto & Enwave.com
This has been around for a long time (Score:4, Informative)
The General Motors Technical Center in Warren, MI has been using open-loop cooling for decades, using the large pond on the campus as an open-ended evaporator. The fishes that live in it don't seem to mind.
There's a nice picture here:
http://www.bcausa.com/projects/tax_gm.html
(Pictured is the "Design Dome" the design building to the right, general engineering in the buildings above the pond, and the Cadillac, Chevrolet, Pontiac and mid-lux buildings beyond)
Re:Environmental effects (Score:4, Informative)
Since this has been going on since the 1800's, I think you could probably estimate the environmental impact based on Chicago's experience.
Re:Environmental effects (Score:5, Informative)
I live just north of Toronto, in Markham (part of York Region).
We get our drinking water from Lake Ontario. All of the GTA (Greater Toronto Area), including the City of Toronto, York Region, Durham, Peel etc, use water pumped from the lake.
Our sewage is sent back down to Toronto, where it is treated before being dumped back into the lake. In fact, they're in the middle of building an additional set of sewage pipes to further growth in York Region (sort of controversial, because they're affecting groundwater and the Oak Ridges Moraine while they're doing it. Long story - google for details).
In other words, I don't think it would make any difference, because we've already been drawing our water from there. It's just coming from a different part of the lake.
Comment removed (Score:2, Informative)
Re:Environmental effects (Score:3, Informative)
More info (Score:1, Informative)
http://www.city.toronto.on.ca/water/deep_lake/ [toronto.on.ca]
Video:
http://www.enwave.com/enwave/news/?s=dlwc&Release
Posted AC cuz I modded here (torstenvl)
postnumber % 1000000 == 0 ?
Re:Environmental effects (Score:3, Informative)
So the area of the turbin = 30*30*3.14 = 2800sq m.
so 2800sq m * 5 = 14000 cu m/s (amount of "air" moving through the area covered by the blades.)
1 cu m of air weighs 1.3kg. So 14000 * 1.3 = 18200kg.
18 tonnes of air moves through the area covered by the turbine every second.
Kenetic Energy of 18000kg moving at 5m/s
= 0.5mv^2
= 0.5 * 18200 * 5 *5
= 227500 kg m^2/s
= 227 kilojoules
227 kJ are produced per second
= 227 kilo Watts (1 J/s = 1W)
Therefor the total energy of wind passing though the wind turbine's blade area is 227kW.
I've heard of wind turbines putting out about 20kW, so that's less that 10% of total power contained in the wind. So the wind would slow down a sililar amount.
http://www.awea.org/faq/basicen.html
Disclaimer:
- Size of blades and speed of wind pulled out of thin air
- Assuming 100% wind-power efficiency, but most likely is more like 50%, which would make it 40kW of wind consumed for every 20kW of power
Re:Environmental effects (Score:2, Informative)
This is why there are controls on what temperature effluent you can discharge into the sewer system. Because biological treatment likes everything very consistant. Also remember the sewage pipes running to the treatment plant from the city run underground in direct contact with the earth which regulates the water temperature.
YIAAEE (Yes I Am An Environmental Engineer)
Questions Answered (Score:2, Informative)
Lake water cooling was pioneered by Cornell University at the end of the 90's, using water from Cayuga lake:
http://www.utilities.cornell.edu/EIS/ExecSummar
This document is a prospectus, but the project is completed and operating as expected.
(1). Annual lake heating is equivalent to 3-4 hours of sunshine once per year (0.1% of total heating)
(2) The project saves 80% of the previous cooling costs.
CV
Re:Environmental effects (Score:4, Informative)
No, they aren't heating the lake. They are extracting a small portion of cold water from the lake, and sinking the heat into that water as it flows on its way to the drinking water purification system. The absorbed heat will be dissapated by the time that water returns to the lake through the sewage treatment system.
I'd agree with you that it would be a problem if that isolated part of the lake were being used as a heat sink, but that's just not the case. What IS happening there is that there is a net loss of colder water in that region, at that particular strata of the lake. But the fluid dynamics of water (and the persistence of temperature strata) will tend to disperse the effect over a fairly wide area. The comparison to 7 additional seconds of sunlight over a year is probably about as accurate as you can get without a lot more math.
I'm sure the reversal [chipublib.org] of the Chicago [lindahall.org] River [niu.edu] more than a century ago has affected Lake Michigan more than this will Lake Ontario.
Re:The lake is NOT warming up ! (Score:3, Informative)
Anyone who lives around Lake Ontario knows how freaking cold that lake is, even when it's high 90's out, humid as hell, you can turn on your cold water and get freezing water out all summer, it's because this is a large deep lake. I live in a different city (still on the great lakes) yet the cold water is noticable warmer in the summer months due to the lake that it draws from being so shallow.
The cold water from Lake Ontario (for city usage) is a constant cold temperature year round, and this is just from the top layer of water that the city uses.
-b
Re:Environmental effects (Score:2, Informative)
Not a nitpicker, but maybe we should start using accurate terminology in news articles so non-experts will stop believing every junk science "story" that comes along.
Little to no impact. (Score:2, Informative)
It's been a while since I've seen that show, so I can't remember if it was a representive of the company or of some environmental agency, but they said that using this system for one year would have the same environmental impact as the sun shining on the lake for an hour and half.
So in other words, you would have to heat up a lot more water then they are to warm up Lake Ontario.
-Derek
Re:Also an interesting fact about water (Score:3, Informative)
where I said elements I meant liquids
and the reason the water wont get warm is that the warm water will rise above the cold water, and when it cools it'll sink.
water's interesting in what it does.
Similar implementation (Score:5, Informative)
Geothermal Heat Pump (Score:3, Informative)
You can find more infomation here [anl.gov] and here [southerncompany.com]
Is Chicago out of luck? (Score:5, Informative)
There was an interview on the morning news yesterday with a guy who is a big fan of this technology. The interviewer asked him if this technology could be used in other cities on the Great Lakes. Yes, he said. There were various cities where it could be used. Rochester and Milwaukee were two examples he offered. But, he said, it could not be used in Chicago. Presumably because Chicago doesn't have easy access to a deep cold layer.
Here in Toronto we have always taken our water from deep in the lake too. As you can see from this map [noaa.gov] the depth drops precipitously just off Toronto Island.
The American fan of this technology was Alec Baldwin, the actor.
The interviewer next asked him if any of those other cities were considering following Toronto's example. He replied that he was flying to Chicago that afternoon to make a presentation.
Re:Environmental effects (Score:3, Informative)
Surely you've noticed a difference in the comfort of 100F at 10% humidity vs. 85F at 90% humidity then? I've been to Arizona and lived in the north-east US. I'll take the former any day. The air conditioning is as much to dry the air sometimes as it is to cool it.
Re:Environmental effects (Score:5, Informative)
Taking deep water, warming it, and returning it disturbs the system, and it would be prudent to understand the effects of that disturbance. If the city's already doing that for drinking and washing, well, now they are doing a whole lot more of it and the effects will be more pronounced, so again it's prudent to understand the effect of increasing the pressure on the system's equilibrium.
I don't study large lakes and I don't know what significant effects, if any, might be expected. I just hope that someone *does* study this particular lake and *does* understand the issues and *was* consulted.
I do hope it works out well. It's a nifty idea.
Finally, this ignorant Yank must admit that his first thought was, "Toronto needs *cooling*?"
Re:Also an interesting fact about water (Score:4, Informative)
You also meant 4 degrees C, not a few hundredths. Below that point, the molecules are slow enough for hydrogen bonding to begin dominating their interaction, and the structures that form take up more space than the unstructured liquid, meaning it's less dense, meaning it will rise above the denser water which is (at this temperature) slightly warmer.
If you notice, you also meant "less dense", not "lighter". H2O has the same mass/mole at any temperature (and the same weight too given equal gravitational acceleration).
Water is, indeed, interesting. Let us know when you're fully awake.
Re:Environmental effects (Score:3, Informative)
Re:Very interest and I imagine many US cities like (Score:2, Informative)
Re:Show me the numbers (Score:2, Informative)
Lake Ontario has a volume of approximately 1700 trillion litres. (1.7x10^15 l) The water used for cooling is then passed to the Toronto Island water filtration plant, which has a daily capacity of about 300 million litres. Over the six month cooling season, it'll warm up about 5.5x10^10 litres of water per year, or about 0.003% of the water in the lake.
Keep in mind that the normal daily transfers of heat into and out of the lake from natural processes are still several orders of magnitude larger than anything humans do.
Not quite right. (Score:1, Informative)
First, it's not lighter, but less dense and thus it "floats" (is displaced by something more dense). This is so because water forms a crystal when freezing and the molecules are actually farther apart than liquid water (to simplify things).
Water at depths doesn't freeze because of the massive pressure it's under. It's an entropy thing, ie it would require more energy to crystallize.
FYI.
Simpler? More direct? (Score:3, Informative)
Simpler? More direct? Let's compare them:
Alternative 1: Want airconditioning? Just use the cold water to do the cooling.
Alternative 2: Use the temperature gradient in the lake to produce electricity and use this electricity to run the air conditioning.
Ahem.
Such plants have been proven to work with ocean water
Proven to work, yes. But not economically. It's very difficult to produce electricity from relatively small temperature gradients and the efficiency is very low. Much higher gradients are available as waste heat from industrial sources and even they are barely practical for producing electricity.
Science fiction authors seem to like this idea, though. Power generation from ocean thermal gradients is featured is many SF works. Don't confuse this with practical and available technology.
Re:Already Done (Score:1, Informative)
You have never been to Niagara Falls, have you? (Score:5, Informative)
Lake Erie and Lake Ontario have about the same surface area. But Lake Ontario is much deeper and so has a greater volume. I have links here to charts showing the temperatures, at various depths across various slices of Lake Erie [noaa.gov] and Lake Ontario [noaa.gov].
Note that Lake Erie is much warmer. But most of the water in Lake Ontario came from Lake Erie? Why is it so much colder? It cools off in the winter time. It takes water from the Niagara River six years before it flows down the St Lawrence.
If, for the sake of argument, Rochester, Kingston, Hamilton all used deep lake cooling, and they all grew so much that they exhausted the Lake's deep layer, Lake Ontario would still not evaporate, any more than Lake Erie evaporates away to nothing.
Yes, there are deep areas of Lake Ontario that have been at 4 degrees celsius for a long time. How long? Since the last ice age? The glaciers covered the entire Great Lake basin a few tens of thousands of years ago. So that is how long a unique deep lake water ecosystem would have had to evolve.
How much water would the cities have to draw from the deep layer to use up all the cold layer? I don't think you understand how deep the Lake is, and how great its volume. Look at these three maps. West [noaa.gov] Centre [noaa.gov] East [noaa.gov]. So, lets say the deep layer is currently something like half to one third of the volume of the lake. The cities would have to use up the equivalent of the flow of two or three niagaras worth of water in order to drain all the deep cold water.
So long as our winters continue to get cold enough for the lake to cool to 4 degrees the cold layer gets regenerated every winter.
I think it could be argued, if Global warming every gets bad enough that using deep lake cooling exhausts the cold layer in mid-summer that, since we have the infrastructure in place, we use it every summer until it is exhausted. What about the cold deep lake water ecosystem? I am all for preserving interesting, unique ecosystems. But I doubt that a few tens of thousands of years is long enough for it to become interesting and unique.
Catch-22 (Score:3, Informative)
For the Heller-challenged:
When Yossarian is in the hospital, he meets the "soldier in white"Changing the jars was no trouble to anyone but the men who watched them changed every hour or so and were baffled by the procedure.
Re:Environmental effects (Score:4, Informative)
and when they take the coldness the water then goes into the city's potable water system. RTFA!
Re:Environmental effects (Score:5, Informative)
Re:Residential applications? (Score:3, Informative)
John McPhee article (Score:2, Informative)
It has to do with running water in the winter into a pit to make slushy ice. Keep it covered, and it will last through summer. Put pipes at the bottom and run water through it, and the water will get cold (duh). Use this new 'reserve of cold' to cool buildings. Easy and cheap.
The story is in the books "Table of Contents" and "The Control of Nature". Both are highly recommended.
Re:Residential applications? (Score:4, Informative)
Like its much more energy efficient to use chilled water a/c with a large central cooling tower. Then pump chilled water out to each home for use in chilled water a/c units. Large office and university campuses do this. But, at several million dollars, the investment is just too much for developers.
Re:Environmental effects (Score:3, Informative)
Necessity is the Mother of Invention. (Score:3, Informative)
http://www.lincolnenergy.com/ does this already (note: I don't work there so I don't know all the ins and outs but I will try to explain what I can figure out from talking to a friend of mine who does)
Canadian climate is harsh. With the exception of the west coast much of Canada experiences hot summers, and cold winters. You probably know that while the surface temperature of the Earth changes quickly the temperature a couple hundred feet down usually stays at the average temperature of the region. Lincoln energy uses a technology they call "GeoThermal Exchange" which uses the Earth's heat to cool down buildings in the summer, and warm them up in the winter. The technology does not require as large a setup as the one described in this article and can be economical for single buildings. To quote from their website:
Re:Environmental effects (Score:5, Informative)
Re:Environmental effects (Score:5, Informative)
According to a cooling calculator online, a 30x60 office building would require approx 23.5 million BTU cooling over the course of a month. This assumes the building is insulated (I'm sure all Toronto buildings are) and that it's longest wall faces the sun. It also assumes cooling 24 hours a day. (If somone out there is a cooling systems engineer or contractor, why not share the actual cooling needs for typical office builings?)
Based on the numbers (and assuming the cooling plant is fairly efficient) then you should be able to cool somewhere around 51 million such buildings for three months (about the max cooling season there) before you have transfered enough heat to raise the lake's temperature one degree. I suspect if you used accurate heat transfer numbers you'd find it would take even more time.
In other words, before you could make any significant difference in the lake temperature, the next winter should re-cool the water already as others have mentioned.
Re:I was going to ask about that... (Score:1, Informative)
Please.
Take it from a Canadian.
Mod parent down - untrue (Score:5, Informative)
Re:Just two questions (Score:3, Informative)
IANA Weatherman/Climatologist. That said, there are plenty of places around the world with warm water adjacent to cold climates. Anchorage, the whole SE alaskan coast, Ireland, Great Britain, etc. You don't get 120' of snow. You can get 30" of rain or more, though.
If the winter temp >32, lake effect is to warm stuff up and you get rain. The warm currents could be why the above list of places are all foggy, rainy spots.
Once temps reach 32, the lake freezes, then temps tend to plummet.
I've only been to Buffalo a few times, and Toronto once. I'd always assumed that being north of the lake spared Toronto from eastward and southward storms that'd pick up moisture and dump it on 'em. Meanwhile, Buffalo's not so well-positioned.
Anyone else know for sure?
Incidentally, I've heard of places where nuke power cooling discharge has so altered the *local* water temp that 1 - people swim there in cold weather, 2 - tropical fish thrive, etc. That'd be another strong example of why the thermal impact of this Toronto project are probably trivial.
Re:Environmental effects (Score:1, Informative)
How this affects the environment depends on the amount of heat pumped into the lake, the volume of the reservoir, the size of the surface area, etc.. You have to have models and numbers to make any prediction. It's a folly to conclude anything without numbers to back it up. Saying that it's a stretch of an old method of cutting ice to cool down house is silly considering that the number of pupolations and buildings now vastly outnumbers then. Can you say the same about dumping waste into a river, after all it's a stretch of the old method? People did it in the old days, but if you dump sewage into rivers now, you'll have serious problems.
Yes, 5 tons per car (Score:3, Informative)
500 gallons * 6.167 lbm/gallon = 3083 lbm fuel.
3083 lbm fuel * (12 g carbon / 14 g fuel) = 2643 lbm carbon.
2643 lbm carbon * (44 g CO2 / 12 g carbon) = 9689 lbm CO2.
That's close enough to 5 tons (4.5 metric tons) for my taste. Your mileage (pun intended) may vary.
Re:Environmental effects (Score:5, Informative)
I assumed standard water (1 kg/L) when converting from volume to mass. I also used only two significant digits for specific heat capacity (4.2 kJ/KgK). I also assumed uniform temperature and uniform heat distribution because I'm looking for averages, to get an idea of order of magnitude.
Anyway, I RTFA and saw that the cooling power is only about 207 megawatts. That convinced me to rule out any macroscopic environmental consequences and get on with my life.