Alternative Climate Control (water cooling)

[Nowhereman1280]

^^^
Hmm well this is interesting. I wonder how else they would do it? I'm sure that it wouldn't have any impact on the so-called "eco-system" of the Chicago River. I generally don't think of the river as having much of anything living in it. Not to mention it would be flushed out into the lake right away and cooled by the lake waters...

[honte]

The process is basically as I said in the first post. You dig a well and let the earth regulate the temperature before returning the water to the river. But in Chicago that sounds mighty strange, because the water table is so high anyway. Maybe there is a tube and the water is pumped back down... ? It's not making a lot of sense to me.... hence the reason I question the whole thing.

[bnk]

is currently being build in the northwest suburbs of Chicagoland.

Elgin.

FYI

Originally Posted by honte

The process is basically as I said in the first post. You dig a well and let the earth regulate the temperature before returning the water to the river. But in Chicago that sounds mighty strange, because the water table is so high anyway. Maybe there is a tube and the water is pumped back down... ? It's not making a lot of sense to me.... hence the reason I question the whole thing.

Your answer lies below.

http://thefutureofsherman.com/energy_faq.php



A view from Sherman Hospital's Geothermal LakeGeothermal energy is energy that is derived from the temperature of the earth. The earth absorbs 50 percent of all solar energy, and traps it as heat just below the frost line. Using a heat pump, this natural and renewable resource trapped below the earth's surface is transformed into a harnessable form of energy. This energy --geothermal energy-- provides buildings with a dependable, eco-friendly and economic heating and cooling system.

Geothermal heating and cooling technology has been given the best rating by the Environmental Protection Agency (EPA).
Geothermal energy is a renewable resource, and doesn't deplete non-renewable resources.
Geothermal energy does not produce any form of pollution. And, it doesn't contribute to the greenhouse effect.
Buildings that use geothermal energy use up to 40% less energy than other high-efficiency buildings.
Geothermal energy requires no outside sources of fuel to keep the power houses running.
According to a U.S. Energy Information Administration (EIA) report issued on Oct. 12, 2005, heating bills for all fuel types will cost Americans about one-third more during the 2005-2006 winter, on average. Projected rates for the Midwest are up to 61 percent higher than last year. With significantly rising energy costs, geothermal energy provides a cost-effective alternative for heating and cooling.

Sherman Hospital plans to build one of the largest geothermal lakes in the world. Unlike other forms of geothermal technology, geothermal lakes rely on the heating and cooling properties of water.



Construction of Great River Medical Center’s Geothermal Lake, West Burlington, Iowa: Installation of Grids and Pipe CoilsThe temperature at the bottom of the lake--a constant 55°F--will be the heating and cooling source for the hospital. The energy for the hospital will be harnessed by a lake loop-heat pump system under the water.

Sherman's geothermal lake will provide energy-efficient heating, cooling and ventilation, resulting in increased patient comfort and safety. The lake will make Sherman one of the most energy-efficient health care facilities in the country. It also will help Sherman to significantly reduce operating costs

Sherman's geothermal lake will be one of the largest - if not the largest -lake loop heat-pump systems in the world.
Sherman will be the first hospital in Illinois to build a geothermal lake.
The geothermal lake is projected to decrease Sherman's gas and electric costs by nearly $1 million annually, compared to the energy costs of its current campus.
The geothermal lake will allow Sherman flexibility to grow. It is easy to expand the geothermal system when the hospital grows.
The lake will help Sherman create a therapeutic atmosphere. The lake will have a fish population and a fish feeding dock for patients and visitors.
The lake will be safe. Sherman does not expect safety issues with its lake, but as an added safety feature, Sherman's lake will have a shallow shelf around the edge of the lake.



A view from Great River Medical Center's Geothermal LakeThe geothermal lake is a fiscally responsible choice for Sherman. With rapidly rising energy costs, using an alternative energy source is a smart choice to manage the hospital's energy costs in the future.
Sherman already had plans to build a six-to seven-acre water retention lake on the replacement hospital site, so building a geothermal lake is a logical and easy extension of those plans.

Starting from a blank slate presented an excellent opportunity for Sherman to incorporate geothermal technology into the plans for the replacement hospital. It is very difficult for buildings to convert to geothermal after a building has been constructed, which is one of the reasons the technology is not more prevalent across the country today.
Sherman's 154-acre replacement hospital site has plenty of room for a 15-acre lake.
Sherman's due diligence period showed that one other hospital in the country has embraced geothermal technology on a large scale. Great River Medical Center in West Burlington, Iowa built a geothermal lake five years ago. In addition to being recognized as one of the most environmentally-friendly hospitals in the country, Great River has saved more than $1 million annually over the cost of heating and cooling its old campus. Sherman Hospital is committed to being one of the most energy-efficient hospitals in the country. Sherman's plans to build one of the largest geothermal lakes in the world will help the hospital achieve its goal. Sherman is doing its part to make a cleaner, brighter future.

As modern as the word "geothermal" may seem, its roots date back as far as 10,000 years ago when an ancient Indian culture tapped into the natural resource of hot springs. The United States first capitalized on geothermal energy in the early 1800s. The first commercial use? Three spring-fed baths in the city of Hot Springs, Arkansas, in 1830.

Geothermal technology is a dependable, proven technology with many uses around the world. Geothermal power plants are producing electricity in more than two countries, supplying about 60 million people with energy. In the U.S., geothermal technology supplies 4 million people in the Western U.S. and Hawaii with energy. More than 500 schools across the U.S. have adopted geothermal technology.

[Nowhereman1280]

^^^ Nice Post Bnk!

How exactly does a heat pump work?

Well out of curiosity I just looked it up on wikipedia and I guess they just use pressure differentials to transfer energy, Its like a reverse refrigerator I guess. Another question that I can't look up on wikipedia is, how do they save more energy then they use pumping the heat? Isn't refrigeration really inefficient?

[honte]

^ There is no compressor, like you would have in a cooling system. It's just a heat exchanger and a pump to circulate the fluid (which is environmentally friendly antifreeze in northern states). The heating or cooling effect it achieved through transfer of energy from the thermal mass - usually the earth itself, but sometimes fluids. Usually you can get 3x the energy saving out vs the energy that you put into the system.

By the way, Unity Temple in Oak Park has recently gone through (or is still undergoing?) a very expensive and elaborate process to install heat pumps for their heating and cooling needs.

[Nowhereman1280]

Originally Posted by honte

^ There is no compressor, like you would have in a cooling system. It's just a heat exchanger and a pump. The heating or cooling effect it achieved through transfer of energy from the thermal mass - usually the earth itself, but sometimes fluids. Usually you can get 3x the energy saving out vs the energy that you put into the system.

Hmm, Interesting, but I guess I still don't get the exact physics behind it. Perhaps there is an entry on howstuffworks or something?

[bnk]

Originally Posted by Nowhereman1280

Hmm, Interesting, but I guess I still don't get the exact physics behind it. Perhaps there is an entry on howstuffworks or something?

Perhaps this will help.

http://en.wikipedia.org/wiki/Geother...ange_heat_pump

A geothermal exchange heat pump, also known as a ground source heat pump or GSHP, is a heat pump that uses the Earth as either a heat source, when operating in heating mode, or a heat sink when operating in cooling mode. All geothermal heat pumps are characterised by an external loop containing water or a water/antifreeze mixture...



A diagram of a simple heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor.




Cooling mode

The cooling cycle is very similar except a valve on the internal refrigerant loop reverses the direction of flow. Now the compressed refrigerant coming from the compressor heats the external fluid, before passing through the evaporator where it vaporizes taking up heat from the air in the house. The heated external fluid is pumped into the ground where it is cooled and recirculated. Alternatively, the superheated refrigerant may pass through a second heat exchanger allowing the water heater to absorb the waste heat. This means that in summer, the heat pump provides air conditioning and the hot water. The heat is being pumped from the air in the house to the water in the water heater.

Heating mode

In heating mode, the external fluid is pumped from the well at 8-16 degrees Celsius and passes through the heat exchange unit. Within the heat exchanger, the refrigerant expands and changes from liquid into gas. This absorbs heat (latent heat of vaporization) from the external fluid, thereby cooling the external fluid. Meanwhile the refrigerant is pumped to the compressor where it is pressurized thereby becoming superheated. This 'hot gas' releases the heat and warms the air of the house. At the same time, the refrigerant gas loses heat to the air and changes back to a liquid. The external loop again provides the heat necessary to change the refrigerant back into a gas thereby cooling the external fluid. The external fluid absorbs heat from the soil and the process is repeated. Note the external fluid only changes temperature while the internal refrigerant changes both temperature and phase. There are some residential heat pumps that use refrigerant in the external loop.

[honte]

^ Hmmm. Maybe I was wrong; there does appear to be a compressor. Not a mechanical engineer...

[Loopy]

There is a lot less magic in these systems than is obvious from the hype.

Generally, in an open-loop geothermal system, the natural water source simply replaces a traditional cooling tower. In most of the Chicago river water systems, the energy savings come from using river water for the condenser loop on the buildings chiller system. This saves energy by eliminating the need for a rooftop cooling tower, thus subtracting the cooling tower fan motor horsepower from the energy equation. Also, some savings are realized from lower pump horsepower as well, given that the water does not have to be pumped all the way to the roof of a high-rise buiding to reach a cooling tower. But this water is still a secondary heat rejection loop; river water is not being used to directly cool and dehumidify building air.

Some buildings have been engineered to use lake or river water for the primary cooling loop during Winter in large buildings with high internal heat loads. I'm not sure if any Chicago buildings do this though.

The Toronto system is no different. The only novelties there are that they have mechanical chiller systems engineered to take advantage of the cold lake water (80 degree water is fine for traditional cooling tower operation) and they are able to send the warmed water to the regional water treatment plant which saves the water treatment process energy because they previously had to warm the lakewater before they could condition it for domestic use. The primary cooling loop does not use lake water either directly or through plate heat exchangers. It is simply used in the secondary condenser loop that removes the rejected heat from a mechanical chiller.

A geothermal, open-loop heatpump system uses ground, river or lake water for both a heat source and a heat rejection medium using mechanical refrigeration devices (compressors). Again, no magic there, as this has been done on a smaller scale for decades. Air-source heat pumps are common as dirt in regions South of here for small residential heating and cooling. And closed-loop water-source heat pump systems are common in larger Southern buildings as well. Efficiancy gains and industry acceptance have made the combination of Geothermal loops and water-source heat pumps an interesting proposition. But there is little about either technology that is new.

[honte]

^ Thanks Loopy. I need to get my technical knowledge of these systems up to the next level, it seems.

[Loopy]

Ha, after one year of reading your excellent posts, I'm stunned to finally discover an aspect of development that you are not fully expert in! I mean this sincerely, you are the least dilletantish forumer I know of.

But back to the subject. One ironic twist to keep in mind when considering these new gee-whiz systems is that the technology and efficiency improvements that are making them viable are also making the more traditional approaches to HVAC even more desirable.

Geothermal heatpump systems are now being introduced into local condo projects. As a consumer and an HVAC expert, I would avoid these systems like the plague. Their value as marketing devices greatly outweighs their true value as heating/cooling systems. Imagine the special assesment your humble building would face to repair a leaking ground loop 400 feet below your condo. No thanks.

[Nowhereman1280]

Thanks Loopy, your posts were a great read. You seem to be quite knowledgeable on this subject so I will ask you questions when I have them.

Since you know a lot about this, do you think it will ever be a possibility for Chicago or even Milwaukee to get a system like Toronto? If we are using the water already, we might as well save the energy and use it for cooling as well. Do they even need to warm the drinking water in Chicago and Milwaukee?

I have a friend who works as an engineer at MMSD, Milwaukee Metro Sewage Disposal or something like that, I should ask him about the heating the water thing and get a firm answer, unless you already know.

[Loopy]

Nowhereman, I just noticed that you had started this thread specifically about the Toronto system, so I went back to the Enwave site to give it a closer look. I was initially put off by their vague descriptions and I wrongly assumed it was just another lake water heat rejection system. But its actually quite revolutionary.

http://www.enwave.com/enwave/dlwc/

I wrongly assumed that the chillers were doing all of the dirty work and the cold lake water was a super efficient condenser medium to carry the heat away from the process. But it is a lot slicker than that.

The Enwave system does seem to use the lake water as the primary medium of heat removal. Although it is separated from the customer's buildings by two sets of heat exchangers, it is still the primary medium. The chillers are in line between the first and second sets of heat heat exchangers to trim the delivery temps in response to the load. My guess is that that the chillers are sized to run as though they were in traditional duty, that is; in the Winter, they hardly run at all, run moderately in Spring and Fall, and run balls-to-the-wall all Summer. But they only have to be as large (and numerous) enough to make up for the efficiency lost in two sets of heat exchangers that are placed between the cold lake water and the customer.

It seems that there would be no need for the chillers at all if the lake water could be pumped directly to, and through the customer's building.

http://www.enwave.com/enwave/view.asp?/dlwc/flow

Before the chillers, the first set of heat exchangers isolates the lake water from the primary cooling process water for sanitary reasons. Without these first heat exchangers, a blown tube in a chiller would send refrigerent and oil into the domestic drinking water supply. Not good.

After the chillers, a second set of heat exchangers are necessary to isolate the customers buildings from the process water in case a single building blew a pipe, the whole metro system doesn't drain out and every building in the network loses their cooling.

Also, it seems that the lake water goes through the filtration plant before the thermal process. It is entirely potable while it goes through the first set of heat exchangers. I'm not sure where I got the notion that the extra btu's were assisting the purification process. I took water purfification courses in school and it was always beaten into us that low water temperature was undesirable for the coagulation and flocculation process before filtration. The warmer the water the higher the process rate could be set through the system. It could be that the ultra deep source of the water negates the need for flocculation, and it merely needs filtration, which is not temperature critical.

Could Chicago do this at Jardine? That would be cool if we could because Jardine is one of the biggest plants in the world. But as was already discussed, Michigan is no where deep enough to provide year-round 39 degree water. Too bad? Maybe.

Don't forget that the distribution efficiencies are low in these systems and the costs are high. Also, it creates a new monopoly utility for the buildings that are connected to it. I would rather encourage the less sexy approach of good building design and execution, expert mechanical specifications, smart control systems and good building operation practices, than this top down approach. Much more energy (and money) will be saved this way in my opinion.

[bnk]

Originally Posted by Loopy

Could Chicago do this at Jardine? That would be cool if we could because Jardine is one of the biggest plants in the world. But as was already discussed, Michigan is no where deep enough to provide year-round 39 degree water. Too bad? Maybe.

.

I am not so sure that threre is no where deep enough intake depth in lake Michigan for Chicago to utilize.

Toronto intake depth is at 83m.





In the image that depth could be achived if the intake point was in the green zone. It would be a good distance, so the economics or engineering factors may have something to say about this.


Also

http://www.geo.msu.edu/glra/workshop...hp/AMtalks.htm



Projected average temperature of lake bottom at average lake depth under HadCM2

Also

At that depth, greater than 50-60m the water temperature is similar in each lake Ontario or Michigan. See page 24 below.

ftp://ftp.glerl.noaa.gov/publication...108/tm-108.pdf

[Nowhereman1280]

First off, Jardine is the biggest water purification plant in the world, an interesting, but brief history can be found here:

http://www.chipublib.org/004chicago/...e/tunnel1.html

Anyhow, if it was economically practical to build a tunnel 60 feet under the lake bottom for two miles under the lake just to get clean water in 1867, I imagine it would be no problem at all to engineer a tunnel 10 miles out today to get 2C degree water from the lake basin.

I guess people are just convinced that its not worth the trouble, but I think that it would be well worth it. I mean it would drop cooling prices to nearly nothing, it would literally make cooling as cheep as water. It would also make highrise construction cheaper because there would be less of a need to build cooling towers on top like many large buildings use.

[bnk]

Originally Posted by Nowhereman1280

Anyhow, if it was economically practical to build a tunnel 60 feet under the lake bottom for two miles under the lake just to get clean water in 1867, I imagine it would be no problem at all to engineer a tunnel 10 miles out today to get 2C degree water from the lake basin. I guess people are just convinced that its not worth the trouble, but I think that it would be well worth it. I mean it would drop cooling prices to nearly nothing, it would literally make cooling as cheep as water. It would also make highrise construction cheaper because there would be less of a need to build cooling towers on top like many large buildings use.

I have to agree with your valid points. 1867 was over 140 years ago.

Today this cannot be that great of an engneering feat compared to back then.

This would be much less of a problem as the Deep Tunnel http://en.wikipedia.org/wiki/Tunnel_and_Reservoir_Plan , Chunnel projects of the recient past.

[Loopy]

Here is a pretty good article on Enwave from Scientific American

In Focus
September 27, 2004
Big Chill
An ambitious new project uses lake water to cool off city slickers
By Sarah Graham

DEEP LAKE WATER COOLING project in Toronto uses water from 80 meters below the surface of Lake Ontario to cool downtown buildings.
Staring at a lake on a hot day, many people might think the most straightforward way to cool off would be to jump into it. But the city of Toronto recently unveiled a much more intricate way to use Lake Ontario to cool some of its citizens. Beginning on July 15, an elaborate set of pipes began dredging cold water from the bottom of the lake to cool downtown buildings. According to Enwave, the company responsible for the $170-million project, it will reduce overall annual power usage by more than 40 megawatts and greenhouse gas emissions by nearly 40,000 metric tons--the equivalent of taking 8,000 cars off the road--once it is fully operational.
The new system is an example of Deep Lake Water Cooling (DLWC), an alternative to airconditioning systems dependent on fossil fuels and electricity. The idea is not novel. As Lanny Joyce, program manager of the Lake Source Cooling Project at Cornell University in Ithaca, N.Y., points out, cities have had to rid themselves of excess heat since the industrial revolution. Indeed, a number of Scandinavian cities, including Stockholm, use bodies of water as heat sinks and have been doing so for more than a decade. Seattle recently commissioned a study that investigated the potential of DLWC for a new development area; small systems in San Francisco and Vancouver are in place, and a site in Hawaii is also under construction.

ADVERTISEMENT (article continues below)


The process relies on a simple premise: heat flows from hot to cold. A closed loop of chilled water flows through buildings, taking with it heat removed by air conditioning. Often, expensive chillers use refrigeration to remove this excess energy. But with DLWC, the cold lake water whisks the heat away. For example, in Cornell's set up, water drawn from Cayuga Lake is between 39 and 41 degrees Fahrenheit, but when it returns it is slightly warmer, averaging about 47 degrees F during the winter and 56 degrees F in the summer.
The Toronto project is more ambitious in scope. In the planning stages for more than 20 years, the development includes a new intake pipe for the city's drinking water supply. Water removed from 80 meters below the surface of Lake Ontario is pumped through three pipes to the Toronto Island Filtration Plant and treated to meet drinking water standards. Next, it travels to an energy transfer station and moves through heat exchangers to chill Enwave's closed water-supply loop that is distributed to customers. The two water supplies don't mix, and the lake water, now warmer and potable, moves to the John Street Pumping Station to be distributed to consumers. Meanwhile, the chilly water in Enwave's closed loop is distributed to their network of customers, with the cold water doing the work that used to be the domain of old-fashioned mechanical chillers.

Since its July 15 start-up, the system has been cooling nearly a dozen downtown buildings, including banks and office towers. “Everybody's thrilled because the water's colder than we had expected, slightly, and the heat exchange is working well,” Enwave's COO Chris Asimakis reports. “It's nothing but good news so far; the customers seem happy.” To date, however, Enwave has only signed up enough businesses to utilize about 34 percent of the system's total capacity.

Part of the resistance, Asimakis surmises, stems from the unknown nature of the project. “Everyone's familiar with chillers,” he says, referring to the devices that use chemical refrigerants, such as chlorofluorocarbons (CFC) until they were banned in 1993 by the Montreal Protocol, to control temperature and humidity. He points out that businesses signing up with Enwave can view the move as insurance against rising electricity costs, because the dependency on ever-present lake water leads to price stability. In addition, the heat exchangers used by the buildings on the Enwave loop last 50 years, on average, whereas a chiller's lifetime is estimated to be 20 to 25 years at most. Citing the example of the CFC ban, Asimakis further notes that many companies had to replace or retrofit their chillers to comply with the new regulations. For Enwave customers, the company manages the infrastructure and would be responsible for any such concerns in the future.

The start-up costs associated with DLWC are impressive, and in many cases, prohibitive. The report commissioned in Seattle, for example, notes that the price tag is more than what developers would consider feasible at this time. In the case of Cornell University, Joyce observes that the school had one advantage over industrial interests: “Cornell has been around for almost 150 years, and expects to be around for at least 100 more,” he remarks. A company that lacks such security is less likely to want to absorb the large initial costs. Even with some long-term security in place, the decision to switch to DLWC was not an easy one, Joyce says. In the high-flying mid-1990s, selling people on a system that required between 10 to 13 years before costs could be recouped was difficult, but in the end the university decided that it was worth it to reduce its overall environmental impact. To date, Cornell has decreased the energy utilized for air conditioning (about 10 percent of the total campus electricity use) by 86 percent, thanks to the Lake Source Cooling Project.

When it was first proposed, the Cornell project did encounter some initial resistance from a group of Ithaca inhabitants who were concerned enough about the added heat's potential effects on the lake's ecosystem to file a lawsuit in an attempt to stop the project. (The case was dismissed.) In Seattle, concerns about the health of the salmon population were also raised during the study. But the envionmental benefits of DLWC often outweigh the worries. "Some roadblocks have been thrown up, but none have not been permitted" once officially proposed says Bob Klug, a senior systems analyst for Seattle City Light who wrote the grant applications for the city's feasibility study. "[DLWC] is as green as can be."

The old adage, “location, location, location” also plays a huge role in DLWC, with geography being the biggest limitation on which cities, towns and companies can even consider employing the system. In addition, the approach requires district cooling, a central system that pools the cooling requirements of a number of buildings, in order to work. But if the Toronto project is a success, it could make other lake-adjacent energy users sit up and take notice.

© 1996-2007 Scientific American, Inc.

[Loopy]

A more recent blub on Deep Lake Water Cooling from the Economist that mentions chicago.

Hydrothermal cooling

A cool concept
Apr 24th 2007
From Economist.com

How to use cold water from lakes and oceans for air conditioning

GEOTHERMAL heating—using the warmth of the Earth’s interior to heat water—is an old idea. Using the planet’s natural coolness, though, is something of a novelty. Nevertheless, as cooling and heating are merely two ends of the same process, it could save money and reduce carbon-dioxide emissions. As long, that is, as you can find a suitable source of cold.

Fortunately for Toronto, it sits next to a very large supply of the stuff, in the form of Lake Ontario. Canada’s largest city has been pioneering the idea that instead of using electricity to power air conditioning, a useful supply of cold can be directly extracted from the environment.

Three large pipes have been run 5 kilometres (3 miles) into Lake Ontario, to a depth of 83 metres. The water at that depth is a constant 4°C, its temperature protected by a layer of water above it, called a thermocline. The water is piped to a filtration plant and then to a heat-transfer station on the lakeside. Here the chill is “transferred” to another closed loop, consisting of smaller pipes that supply the towers of the city’s financial district. Built at a cost of C$230m ($200m) over four years, the system is run by the Enwave Energy Corporation.

One of the first buildings to be connected was the Toronto Dominion Centre, a distinctive set of office towers. Three of the five black buildings were designed by Ludwig Mies van der Rohe and built in the late 1960s and early 1970s. So was their air conditioning. Connecting them to the deep-water cooling project saves 7.5 megawatts of electricity.

The two newer towers, modelled on Mies van der Rohe’s designs, were also recently connected and this summer all five will be air conditioned by water from Lake Ontario. That will save another 2.5 megawatts. Another 12 megawatts will be saved from the connections to the Royal Bank Plaza and the Metro Centre, home to local government.

Some 36 buildings in the central business district have now been connected and a further sixteen have signed on to join the system. The project is expected to save the city 61 megawatts, enough to power 8,500 homes.

Toronto’s project is the largest of its kind in the world and the only one that combines cooling with drinking water. (The water taken from the lake goes on to reservoirs and provides about 15% of the city’s drinking water.) Other cities use similar cooling projects. The one in Stockholm uses seawater and is about two-thirds the size of Toronto’s. A much smaller system at Cornell University uses Lake Cayuga as a source.

Geneva would be an ideal candidate for the system, as Lake Geneva is both cold and deep. The city is investigating a scheme. Tokyo also has deep water, but has not yet done anything about using it.

Not all cities can benefit. Chicago, for example, initially appeared promising as it has harsher winters than Toronto and sits beside frigid Lake Michigan. But close to dry land, Lake Michigan is shallower than Lake Ontario. To get cold water, engineers would have to lay pipelines that were six times as long as Toronto’s. Officials in New York have explored using such a system, but ran into a similar problem: the neighbouring ocean is too shallow.

Using cold water for air conditioning saves more than just energy. Most office and apartment towers put the cooling units on the roof. Removing them means the space can be used for something else, such as a running track or a garden.

The three original Mies van der Rohe towers in Toronto have the cooling units built in between floors, so they appear as black, windowless bands from the outside. The owner is now working out how to convert that to office space, which in downtown Toronto is as precious as electricity.

Copyright © The Economist Newspaper Limited 2007

[honte]

Loopy, thanks for all the great information. I'll have to re-read your explanation a few times when I get a bit more time - it's going to take a while to wrap my brain around all of the technical aspects.

[Ecacophonix]

It is quite fascinating the amount of info and expertise being provided at this post on geothermal-based air conditioning...especially the practical and technical aspects...but I'm not sure how geothermal would perform on a large-scale implementations

I do a fair bit of work in oil & energy from algae , and of course am aware of geothermal only in passing, but this post gave me a much better idea...many thanks

NS @ Oilgae.com - Oil & Energy from Algae