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Cooling Toronto Using Lake Ontario
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."
Q1 is a valid concern.
Q2 is apparently answered in the article. Approx 25% of the energy requirements for electrical air con.
From the article:
"...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.
No it won't, because the water used to cool the air is the same water that would be extracted anyway, to provide potable water to the city. See this schematic. Notice the warm water is not returned to Lake Ontario.
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From the "Fact Sheet" on Enwave's site,c /fact
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?
This has been covered extensively on Discovery Canada, which I watch regularly. Here's a quote that puts this into perspective:
...He said environmental studies show the system will cause a temperature increase [each year] equivalent to the heat the lake surface absorbs during seven seconds of sunshine....
-Toronto cools off using Lake Ontario waters
According to the site they use the city water supply
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.
RTFA !
Look at the diagram on http://www.enwave.com/enwave/dlwc/ They warm up the city's drinking water by a few degrees.
A
Here's the BBC's story about it.
Oxford Dictionaries Online
From the CBC
/ 17 /enwave_040817.html
No registration required;
http://www.cbc.ca/story/canada/national/2004/08
I think this is unlikely to be a problem.
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.
They're not sending the warmed (by 8'C) water directly back - it goes to drinking water supply. The CO2 thing IS super-scary though, imagine living by a lake like that (which people still do) :-O
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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 :) ).
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.
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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.
Will this not cause the lake to warm up?
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.
Actually, Greenpeace is completely backing this endeavor. The water they're taking was also part of an overall plan to upgrade the drinking water plants, so the water is just being diverted before going into the drinking water. Then the water just returns through where the water has always been going (sewers, water treatment, and then probably the lake).
We've done enough (I'm from Toronto) to screw up the environment around this city, we should NOT be doing this!
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.
Man, I can't believe I'm getting sucked into this moronic, paranoiac debate.
.000000293 btu's per megawatt hour = 2* 10 ^9th Megawatt hours needed.
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.
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 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
Geothermal has been around for a long time. There are closed loop systems that put the condenser coil underground, and open-loop systems that use streams (ideal) and ponds (somewhat less ideal)
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)
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Since this has been going on since the 1800's, I think you could probably estimate the environmental impact based on Chicago's experience.
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So might be a double whammy, the water isn't directly injected into the lake again.
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.
You can accomplish anything you set your mind to. The impossible just takes a little longer.
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 of the Chicago River more than a century ago has affected Lake Michigan more than this will Lake Ontario.
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A similar lake source cooling project was implemented at Cornell while I was there. They tore up half the campus laying 36" pipe down to the nearby lake. Of course this project is much larger (with a larger lake as well), but from what I have heard the Cornell project has been a success despite the hand wringing of the radical environmentalist. The Toronto plan seems to be even better as they are not discharging the water directly back to the lake (as they do in Ithaca) but are processing it for drinking water. more information on the Cornell LSC website http://www.utilities.cornell.edu/LSC/default.htm
You can find more infomation here and here
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 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.
In sufficiently large bodies of water there's this thing called the thermocline, separating surface circulation from deeper circulation. It's somewhat like two different bodies of water stacked one on top of the other -- there's less mixing between the two than one would naively expect.
:-)
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*?"
You meant "compounds".
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.
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 and Lake Ontario.
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 Centre East. 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.
RTFA! They don't take the water at all. They only take the coldness.
and when they take the coldness the water then goes into the city's potable water system. RTFA!
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Warming up a lake a few degrees would take a ridiculous amount of energy, more than any city could possibly put into a lake. Calculate it, it takes 4.184 joules to warm up one gram of water one degree C. There are 1640 km^3 of water in Lake Ontario. That's 1 640 000 000 000 cubic meters, which is 1.64 × 10^18 grams. 1.64e18 * 1.0 deg C * 4.184 J/g-degC = 6.87e18 J. This is 1906044444444 kilowatt-hours, which is a hell of a lot.
Eight feet is not deep enough to produce the chilling effect on water seen in lakes like the Great Lakes (or upstate New York's Cayuga Lake, where a similar system was installed to provide cooling for Cornell University several years ago).
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the capital investment tends to be prohibitive for residential applications.
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.
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It's funny you should mention the "Canadian" winter as being especially cold, considering that the winter is always much milder in Toronto than it is SOUTH of the lake in the US :)
The amount of extra energy this will put in to the lake should be close to zero. The water is going to be used as drinking water once they dump a little heat into it. If they where taking that water from the lake to drink anyway the total change from right now should be zero.
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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.
Read this post. Lake Ontario (like most lakes in Canada) mixes once a year in the autumn (turnover, or overturn - I've heard both terms used), usually in the late fall prior to freezeup. The lake is only stratified in the summer, and the only special property held by water at the bottom is a lower temperature in the summer.
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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.
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