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Comment by boringg | Hacker News Reader

Interesting project -- walk me through how it isn't bringing warm water back. Last I checked thats how cooling loops work.

There is an argument that since it is small it won't impact the lake -- however if you have it en masse it certainly would have an adverse impact.

It's like all things -- the pilot project is cool and fascinating but what are the impacts of something in a very large scale. Also what is the advantage over something like this instead of say renewable backed heat pumps? Is it essentially efficiency of centralized system similar to district heating a la NYC?

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The advantage over heat pumps is simplicity lower total investment. If you need 1/10th as many PV panels that’s not just less cost but less land use and less pollution from mining the materials etc.

In terms of impact, lakes are heat sinks that average out energy gain and loss over a year, but the numbers get huge.

For scale a single hour being cloudy or sunny could be an ~10 terawatt-hours worth of energy being dumped into the lake or not and that doesn’t have a significant impact. Meanwhile Canada total electricity demand at 577 terawatt-hours in 2022. Even cooling every house in the country across a full summer just isn’t going to move the needle here.

> For scale a single hour being cloudy or sunny could be an ~10 terawatt-hours worth of energy being dumped into the lake or not and that doesn’t have a significant impact. Meanwhile Canada total electricity demand at 577 terawatt-hours in 2022. Even cooling every house in the country across a full summer just isn’t going to move the needle here.

I'm not worried about it, but I don't think you can just assume that energy input from sunlight at the surface of the lake is going to be equivalent to slurping up cold water from the deep, heating it, and re-injecting it. Sunlight doesn't make it more than about 200m underwater, and deep bodies of water have distinct layers of temperature and density, largely because the water doesn't circulate freely through those layers.

At the very least, you're creating a current where none existed before.

The return pipe was apparently not in deep waters?

So its strictly extractionary then?

The water is returned near the surface, and being warm it rises.

Heated water is not returned directly to the lake in the Enwave system. It forms part of the city's normal municipal drinking water supply: treated and sent to a pumping station for distribution.

It doesnt affect L. Ontario for at least two reasons:

1. L. Ontario is absolutely massive.

2. L. Ontario would be heated far more by the heat dumped into it by the otherwise displaced electrical generation.

Furthermore, the water return, as I understand it, is in shallow waters. Therefore the deep waters are largely unaffected and surface waters are locally cooled.

I'd take a step back. How is the water heating in the first place ?

They are saying heat exchangers do the magic. OK. Lets consider first the use cases.

- Cool Water: I'm really confused as to how cool water is helping anything. Its not like this water is helping a nuclear reactor or some really hot tropical city. We are talking CAN here.

- Hot Water: I can see the usefulness. But I dont get how they get the energy. There's some electricity warming up the water so it can be useful, but how is that is more effective than other types of heating ? Sounds like a gimmick - Am I crazy to think that ?

I don't know why you're being downvoted—I'm wondering the same thing.

You get down voted when you question the current dogma. I happen to work in climate tech and i find people don’t like questions to their tech especially if its perceived to be exceptionally great and only providing upside.

They'll castigate you as a anti-progress environmentalist if you are on the green side of things or a pro oil toting fool if on the right. The space has become a mimic of our political disconnect. Sad state of affairs for engineers with real questions.

The interiors of large commercial buildings that this loop is serving have no exterior exposure and therefore have only internal heat gain from people, lighting, and equipment. Therefore they are in cooling-only for a lot of the space and often only have heating around the perimeter of the structure where there is heat transfer to and from the environment.

We have a similar thing over here, and the cooling capacity is pretty useful. ( https://www.helen.fi/en/housing-companies/cooling-for-housin... ) As the summers have gotten hotter, this has gotten more common to have a somewhat stable temperature indoors.

Heat pumps allow shifting the temperature that's in the cooling and heating circuits, so you can extract (or add) more heat, making it more effective. This is used to cool data centers and heat homes/offices, so it also allows to move heat between places instead of always having to have a cold sink and a heat source.

Sure, there is electricity warming up the water, but earlier the energy that was used to cool a space was just discarded into the air, now it's gathered and put into the circuit to be useful elsewhere.

Not a gimmick, it saves _a lot_ of energy.

OK, that makes a TON of sense. Thank you .

Your answer implies a circuit, which is logical and explans a lot, but its not what the article is saying directly.

The article just has a cold sink (the lake) which is being asked to expand for help. No idea what the heat sources (nuclear reactor, data center) are that could help close the circuit. Maybe this is where the buildings they mention with the expansion, come in? Yet its not clear if article's buildings are actually the heat sources - unlike your explanation, which is pretty clear.

When water is returned it's pumped to near the lake's surface, so will rise, cool down, then sink.

So it's just providing a higher quality source of 'cold' to make things efficient instead of requiring heat pumps that dump heat to the air directly when it's hot out.

Much more efficient overall.

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