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Comment by hourislate | Hacker News Reader

I've read about this before when Toronto was implementing a system like this. The City of Toronto cools a large portion of it's downtown office towers using this method. They draw cold water from deep in Lake Ontario to be pumped into chillers to cool the office buildings. Seems to be environmentally friendly and cost efficient.

A couple of links:

https://www.acciona.ca/projects/construction/port-and-hydrau...

https://www.toronto.ca/community-people/get-involved/public-...

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Sorta. They run heat exchangers between the in-bound municipal water and loops that go to the office buildings.

So it helps with some eco-effects (ie: there’s no dumping of the heated water), but everyone’s municipal water is a bit warmer in summer. I don’t think the effects of that have been calculated. Can offset water heating a bit; but other office towers use that water for their a/c cooling needs.

They deepened the water intake too, so it definitely means colder tap water in winter too, which residents mostly have to heat up inefficiently.

Is there a limit how hot or cold your waste water can be?

In many eastern europe cities heating is centralised and uses quite expensive wood or oil burners. Wondering if extremely deep geothermal bores could serve 200-500k people.

It’s kinda hilarious (to people living in areas with actual seasons) to hear about summer and winter in Hawaii. Based on the temp averages I see on weather.com, there is some variation. But how does it actually feel? Does “Hawaii winter” feel like actual different season or is it just “slightly less hot summer”/every other day?

Temperature measurements are usually counted as above ground, in shade measurement for the time/date given. In Hawaii the difference in summer/winter is in number of hours of sunshine (due to cloudy/rainy season), sun altitude at solar noon (due to position in northern hemisphere), and total numbers of daylight hours (same thing, due to position in northern hemisphere).

All these factors mean that during summer you need to cool offices in Honolulu more than in winter, even though that the measured difference in temperature at noon can be minuscule.

It feels different to us in Hawaiʻi, mainly due to increased rainfall.

Days are shorter in the winter and the weather patterns are different. Summer is much hotter and the trade winds blow stronger. Winter storms come from north of japan and bring north swells. In the Summer storms near Australia send swell up from the south. And it rains more in winter as another hner indicated. I recall it rained for about 3 weeks straight one year.

It's relative. If you step off a plane in winter you might think the 64°F night-time temp is downright balmy. But if you've lived there for long enough it's "freezing" and requires a nice warm sweater.

But yeah, most freestanding houses have neither, and need neither active heading out cooling (aside from a ceiling fan for circulation).

For the last 30+ years though, it seems like there's been an importation of building design that rely upon air conditioned spaces (concrete with sealed windows basically) where buildings from mid century would have ensued outdoor access on two sides with louvered windows for cross ventilation.

I wonder if this deep water cooling proposal is basically an attempt to mitigate the rather short-sighted move to these more energy consuming buildings and the realization that they are needlessly expensive to operate and not in line with the community's purported environmental ideals.

> deepened the water intake too, so it definitely means colder tap water in winter

Would it be so expensive to have two intakes?

If they considered the (mostly negative) externalities I described, a valve could've been a good idea. But getting people water a few degrees warmer in winter saves somebody else money, not them.

Maybe collecting deeper water improved water quality in some other way. Dunno.

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