The largest deep lake water cooling project just got bigger
theglobeandmail.com
theglobeandmail.com
The lake water continues out of the heat exchangers into the intake of the water treatment system, feeding drinking water to the city. The water eventually returns to the lake after being used by people and flowing through the sewers and wastewater treatment system (returned at a shallower level).
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?
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.
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.
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 ?
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.
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.
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.
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.
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'm mainly curious about the result to the native wildlife since practice engineering's videos on the dams and how fish are handled.
This is net cooling L. Ontario because Darlington (hence the its cooling loop) doesn't have to run as hard to power all the displaced ACs
Return pipe is municipal wast treatment, which is probably enough to make that water essentially the same temperature as surface level waters once it returns to the lake.
The most plausible explanation is that the article is wrong, and that the author meant to say that the lake is about the same temperature as it was before. Which is generally true; although the water being returned is slightly warmer, once you get more than a few meters away the difference is negligible. There is a ton of research on this phenomena with respect to the lake source cooling plant in Ithaca, because people obviously had the same concerns about that one before it was built.
Although L. Ontario's surface can hardly be described as "warm"
1 BTU is about 1kJ, so every 1 square foot of cooling (per hour) could theoretically be offset by 25,000J / 4.18J = ~5980g of water being heated 1 degree C. Density of water is 1g/mL, so it takes approximately 6L per hour per square foot if you assume that you don't raise the temperature of the water more than 1 degree C.
They're talking about 50 million square feet with this system, so that's 300 million liters per hour, or about 80 million gallons per hour, or 1.3M gallons per minute. For context, the third water tunnel project in NYC was supposed to deliver 1.3B gallons per day, or about 903,000 GPM assuming constant flow. That's a big pipe.
I tried to find actual citations of their flow rate, but haven't found anything yet. Regardless, I am skeptical of the claim that they aren't returning warmer water to the lake. I'm not worried about it (lake Ontario is gigantic), but I don't believe the article.
(edit: 1BTU is the energy required to heat 1lb of water by 1 degree F at maximum density, so you could work it out directly from the bizarro-world units of HVAC systems.)
The system has the ability to absorb:
H2o_heat_capacity*mass flow rate * delta(T) = cooling_power.
The first term is know and very large. The last term is determined by the number of users and is estimated with forcast usage models. Ask an Env Eng a desired delta(T) and you get the mass flow rate required.
It's a lot of flow.
When I lived in Toronto, I toured Steam Whistle brewery and they featured this system prominently in their setup.
Is there anything environmentalists won't try to complain about?
Click "Supply" for near real-time data:
* https://www.ieso.ca/power-data
Depending on how much wind is generating, (natural/methane) gas generators are dialed up and down.
Ontario is planning to expand nuclear:
* https://www.cbc.ca/news/canada/london/ontario-new-nuclear-bu...
Both large and small:
* https://news.ontario.ca/en/release/1003248/ontario-building-...
It's really too bad because perfect often is the enemy of good. And when nothing is good enough to be perfect people burn fossil fuels instead and get on with their lives.
It's an ugly truth but it's true.
Keep in mind that environmentalists speak with many voices because they are concerned about different aspects of the environment. Keep in mind that there are many charlatans who will gladly sell something as environmentally friendly when it is not or when it is simply a delaying tactic, so some environmentalists view most claims with extreme skepticism. Keep in mind that there are many environmentalists who believe that we should be setting higher targets.
We shouldn't be painting any group with a singular brush.
There will always be a cost to human life that cannot be recovered from the environment. You can either seek open compromise or veiled genocide.