I'm kind of a novice on this, but what happens to the heated up water? I assume returning it to the bottom of the lake could have effects on local wildlife, so is it returned to the top? That seems like it'd have the same effect but take longer since the hot water will remain toward the top. Or is it assumed to be fine since when winter rolls around the heat will be dissipated then.
I'm mainly curious about the result to the native wildlife since practice engineering's videos on the dams and how fish are handled.
That makes sense, but is a bit misleading (on the part of the article) if true -- you'd have to be pretty lucky to have your water consumption needs exactly match the heat capacity of the system.
That will just make your extracted water hot, making the whole thing a waste of energy?
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.
Not sure if that is the solution here, but the easy way is high volume. If you have enough water volume compared to the amount of dumped heat the temperature rise will be tiny.
> The article says that the water is returned to the lake at about the same temperature that it leaves...though I'm unclear how that's possible.
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.
this system is probably locally cooling the water since the 4C water picks up relatively little heat from the city and is returned to the warmer surface layer.
Although L. Ontario's surface can hardly be described as "warm"
Well, heat capacity of water is 1 calorie (4.18J) per gram. The interwebs hand-wavily say it takes about 25 BTU/hr to cool 1 square foot in a commercial HVAC system.
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 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.
I made another comment down the thread where I estimate this at 1.3 million gallons per minute if you want to have no more than a 1 degree C heating effect.
Because water is densest at 4 degrees, the bottom of every (big enough) lake is that temperature. If they pumped warm water in at the bottom, it would rise because it’s less dense. Regardless that lake is so huge, it would have negligible impact on the overall temperature.
Doesn’t Toronto have far more cold days than warm? So wouldn’t the water mostly be cooled? And if that’s the case, there’s not a lot of headroom above freezing.
>Although many environmentalists say they like DLWC, there is some concern that its reliance on electricity for pumping and running the giant heat exchangers could contribute to carbon emissions if the power is from coal- or gas-fired plants or pose other risks if the source is nuclear energy.
Is there anything environmentalists won't try to complain about?
Canada has high levels of immigration and needs to plan for the demands of a significantly larger population in the future. You can keep ratcheting up the demand on existing infrastructure or offload some demand with better solutions.
Environmentalism suffers from the same "purity test" mindset as other things these days. Better than incumbent alternatives is nowhere near good enough. It has to be blameless now and forever.
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.
> Environmentalism suffers from the same "purity test" mindset as other things these days.
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.
It's a genuine desire to declare human life and experience as having less value than that of the environment. It's the only mindset under which "perfection" is an available option.
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.
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?
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.
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.
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 ?
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.
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.
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.
The system in Toronto takes cold water from deep in Lake Ontario, runs it through heat exchangers that feeds the district cooling loop downtown.
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).
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[ 2.9 ms ] story [ 118 ms ] threadhttps://archive.today/IZSDQ
* https://en.wikipedia.org/wiki/Deep_Lake_Water_Cooling_System
I'm mainly curious about the result to the native wildlife since practice engineering's videos on the dams and how fish are handled.
https://learnmech.com/types-of-heat-exchanger/
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.
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.
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).