While this isn't new, I just learned about it today, and thought I'd pass it along. Cornell University, since 2000, has used a system called "Lake Source Cooling" to cool buildings during the warm Ithaca summers. The technique is fairly simple, and works extremely well. By no longer using traditional air conditioning, the university was able to reduce its cooling-related power consumption by 80-90%, and the campus' overall demand by 10%; in 2001, that meant a reduction in CO2 emissions of over 21 million tons.
Because the old air conditioning systems were falling apart (as well as environmentally hazardous due to the choloflorocarbons in the cooling system), in the mid-1990s Cornell needed to find a replacement. At around $60 million, the LSC project cost more than a direct upgrade to modern conventional cooling systems; since it is designed to have a 75-100 year lifespan, as opposed to the 30-40 years of a traditional cooling system, and results in such a dramatic reduction in energy consumption, the real cost difference was minimized.
The lake water heat-exchange system is fascinating. While it is obviously not universally appropriate, it's an excellent example of working with the environment instead of against it. For those of you concerned about the effects of returning warmed water to the lake, the environmental impact statement makes for good reading (in short, the warm water has a negligible effect on lake organisms, and has a heat effect the equivalent of 2-4 hours of additional sunlight per year). The primary negative effect of the LSC's operations appears to be a 3% increase in phosphorus during the summer months, which contributes to the growth of algae near the outflow pipes.
Do any of you have first-hand experience with this system at Cornell? How well does it work? Would you recommend the idea to other communities?
(Image from Cornell's LSC site)
There are a couple of schemes using even more extreme temperature gradients for this kind of thing.
Solar Ponds collect a lot of sunlight in salty, dark water. The heat is either stored for later heating needs, or in some versions (can't find a link, I think they were in israel) the water use used to power steam turbines by boiling non-salinated (and therefore lower-boiling-point) water.
Ice Ponds freeze an swimming-pool's worth of water in winter, in some versions by just spraying water into the air when it's cold and collecting it in an insulated pit. The ice is insulated, and heat exchanger pipes run through it to provide AC in summer.
It's really a very promising approach for climates with significant annual climatic variations.
Cornel is in a very unique situation.. the finger lakes of central NY are very deep and narrow from glacier carving, in fact the highest waterfall east of the Rockies empties into the same lake a few miles away. And it is very cold in the winter. And the top surface area of the lake is relativly small compared to the depth keeping it colder. And getting to the bottom of the lake from the edge is not very far. All these things make it a poster child for this technology.
The City of Toronto has installed deep lake water cooling for the downtown core. It went in last August, around about the time we were wandering through the blackout. I'll be interested to see the stats on effectiveness as the summer rolls in. Most of the PR doesn't address potential negative ecological impacts, but there are these stats from Environmental Science & Engineering Magazine:
-DLWC uses 90% less electricity than conventional air conditioning and 75% less energy overall.
- It reduces carbon dioxide, nitrogen oxide, sulphur dioxide, smog, acid rain, greenhouse gases and ozone-depleting chlorofluorocarbons (CFCs).
- DLWC cuts the greenhouse gas carbon dioxide emissions by 40,000 tons per year - the equivalent of taking 5,000 cars off the road.
- Sulphur dioxide emissions will be reduced by 176 tons each year. Sulphur dioxide combines in the atmosphere to make sulphuric acid, which kills aquatic life in Lake Ontario.
Why has`nt someone come up with a home cooling system that would utilize some type of heat exchange, running pipes, or radiator fins,perhaps through water, under the foundation of a house in the ground where it is always cooler. It just seems to be the logical way to cool a house, using the least amount of energy.