Hydrothermal Cooling: Improving on Air-Conditioning
by Jeremy Elton Jacquot, Los Angeles on 06.11.07
Unlike the rest of us who are still eagerly awaiting the release of a solar powered air conditioner to quench our hot summers, Canadians living in Toronto have found a cheap and sustainable way to stay cool. Drawing on the large supply of cold water from Lake Ontario, the city's residents have pioneered a method of directly extracting the "cold" to power their air conditioning systems.
Three pipes running 3 miles (about 5 km) into the lake to a depth of approximately 83 m pump 4°C water to a filtration plant and then to a heat-transfer station located on its shores. The system, built by Enwave Energy Corporation, transfers the "cold" to a closed loop of smaller pipes that in turn supply the towers of Toronto's financial district. Businesses have been particularly keen to use this technology as it has allowed them free up space on their roofs previously used by cooling units to invest in more office space or other facilities.
Officials at the Toronto Dominion Center, a set of five office towers, estimate that the technology, which has already been incorporated into three buildings, has saved them 7.5 megawatts of electricity. Once the remaining towers are modified to implement this system, they estimate another 2.5 megawatts of electricity will be saved. With plans in place to connect up to 52 more buildings to the cooling technology, the project is expected to reduce Toronto's energy needs by a whopping 61 megawatts.
But that's not all.
In addition to being the largest such project in the world, Toronto's system is also the only one that combines cooling with drinking water (water from the lake provides about 15% of the city's supply).
Now other cities and institutions are ratcheting up their efforts to establish similar projects: Stockholm's system, which relies on seawater, is about two-thirds the size of Toronto's while the system used by Cornell University extracts its cold from Lake Cayuga's waters. Geneva and Tokyo are both looking at possibly investing in such a scheme. Other cities that had originally been interested in such a project, including Chicago and New York, were unable to move forward due to spatial and depth constraints on their sources of water.
Image courtesy of The Economist
Via ::A cool concept
See also: ::Cooling London's Tube Trains With Ice, ::Eureka! The Solar Driven, "Water-Fired" Chiller-Heater, ::Local Cooling: Tuning Your Computer to Save Energy, ::Air Conditioner in a Can from Japan, ::Solar-Powered Air Conditioner About To Be Released
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I humbly submit that the need for air conditioning does not justify raiding the thermocline. What this effectively does is heat up the bottom of the lakes, which will have adverse consequences to the marine system, AND the local weather. In the long run, no net gain.
Remember back in the era of nukes, everyone was worrying about their "thermal pollution"? This is exactly the same thing.
Effort should be put into LEED-style building retrofits, not using natural thermal sinks to keep inefficent old regimes running business as usual.
This sounds great but has anyone figured out what the increase in water temp does to the lake? We are still just pumping heat from one place to another.
Is this new?
The original World Trade Center used Hudson river water instead of chillers for cooling.
Environmentalists were very upset with number of aquatic organisms entrained by the system.
There are number of articles praising the new Freedom Tower design because it dramatically reduces the amount of river water drawn in for cooling.
Give me a break. A few 10's of degrees difference is not going to make a difference in a lake the size of Lake Ontario. Yes this is heat transfer, as is anything that cools an area down. Maybe geothermal systems will cool the earth down too much too....
I just blogged this as well and had the same thought as mike. I would assume it will increase the lake temp, though maybe not if ONLY Toronto is doing it. Even so, a small increase might be worth it to gain all the electricity and heat production savings this might bring to city, and all the downstream benefits as well.
That's the thing, isn't it? There's no such thing as a machine that consumes heat, only machines that move it from one place to another.
Based on the surface area of Lake Ontario, it receives about 19.5 Terawatts of heat when the sun shines on it on a clear day, so the 61 Megawatts (1/300000 of solar contribution) contributed by this system should have a minimal effect.
I'm guessing that you would have a long battle convincing the residents of the buildings to forego air conditioning to save electricity, so I think this is a huge step forward compared to the status quo.
...but this IS something we're going to have to deal with more and more, the "not enough" factor.
It is clear that some quantiy of thermal pollution would adversely effect the lake, and we must not take any more energy from that lake than that which it can afford to give us. And anyone asking to exploit such a limited public resource should be required to use it as sparingly as possible, or pay top dollar for it. Otherwise it's just greenwashing.
Should the government subsidize solar panels for buildings that haven't been made energy efficient? Should we give tax abatements for hybrid SUVs over a certain unacceptable curb weight?
We can relax about the lake temperature impacts as long as we're taking the cool from large water bodies where the metalimnion is tens or even hundreds of meters deep.
An intelligent system design could be come up with which uses counter-current flow extraction technique to take "cold" from drinking water intake pipes and uses that "cold" to pre-cool the air intakes to HVAC air handlers in the summer. No double dipping then.
Chicago has long had the newby hydrocooler projects like this one beat. The City of Big Shoulders has been hydrocooling buildings in the loop for many years...some implementations go as far back as the early 50s' or possibly even earlier. Withdrawal is not even from Lake MI, as plenty of cold water enters the Chicago River from the Lake, entering through the locks, after which it flows Westerly along Wacker Drive and then moves south around the rim of the City's inner loop. This the same river the water taxis follow to and from the Amtrac and local train station.
The article doesn't say what happens to the water after its "coldness" has been used up. I seriously doubt they waste energy pumping that water back where it came from. They probably just dump it back on top where it has no impact on the thermocline.
But it is all a matter of scale. I'm sure there is a size threshold beyond which this type of system would effect the lake's ecosystem. That threshold maybe so high as to be irrelevant. But gloal warming will definitely have an impact on the lake's temperature.
I've always wondered if we put up too many wind turbines would we change global climate patterns? A wind turbine is harvesting energy from the atmosphere. Can we possibly take too much energy out?
Hi. The "warmed water" is not dumped back into the lake..
people drink it (well ok, people warm it up even more before they dump it back into the sewer systems...)
this is the normal drinking straw for the city. They just add some heat to the water before it goes into the pipes and people drink it. It probably even saves some energy in water heaters that don't need to work as hard to make hot water.