But it warms the water!!! - Thermal plants

OVERKILL

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If you ever do the tour of Bruce Nuclear like @Rand has now done, and I've done a couple of times, one of the things that is pointed out by the guide is that the differential between inlet/outlet temperature on their OTC is only ~3C and it has no impact on lake temperature, as the sun is by far the biggest contributor to lake temperature change.

This is a good picture of Bruce B, where you can clearly see the outlet channel in the foreground, with the 4 units of Bruce A in the background. This is the largest power plant in North America and the largest operating nuclear power plant in the world, which uses Lake Huron as its cooling source. When at full nameplate after the refurbs, it should be at ~7,040MWe.
Razed Heavy Water Plant 02.jpeg


The inlet draws water in from the bottom of the lake about a kilometre out.

But, how "insignificant" is it really?

Well, I've had a few folks bring this up on twitter lately so I figured it might make sense to share what I wrote there, here:

For those following along who might actually benefit from this information, the earth receives 8,160Wh per square meter in a 24hr period (340W per square meter averaged over a 24hr period). The surface area of Lake Huron is 59.6 billion m2, so it receives 20.26TW per hour.

So, again, because we are using a 24hr average (solar peak is over 1,000W/m2) that is 486.25TWh/day. Bruce, at 100% nameplate with all 8 units at full thermal capacity produces 22,656MWth, ~7,000MW of which is converted into electricity with 15,656MW rejected into the lake.

This means, in a 24hr period, the plant sinks 375,744MWh of thermal output into the lake; 0.376TWh, compared to 486.25TWh from the sun. Now, on smaller bodies of water of course, this is going to be more significant, as this relates to surface area and Huron is a big lake.

This is why OTC isn't used on smaller bodies of water typically and cooling towers are employed, to reduce water volume cycled from the body and thermal impact.


I did the same math for Pickering, which is <1/2 the output of Bruce (but Lake Ontario is smaller) and the numbers aren't really any different because of the scale factor:

If we want to look at the specifics of this, for fun, like I did for Bruce, it's pretty straight-forward. Pickering has 6 active units, each with a thermal capacity of 1,744MWth, so a total of 10,464MWth. 3,114MW of that gets turned into electricity, leaving 7,350MWth to sink.

Lake Ontario receives, roughly, averaged over the year, 8,160Wh per square meter from the sun in a 24hr period (340W per square meter per hour). It is the smallest of the Great Lakes with a surface area of 18,960 square kilometres; 18.96 billion square meters.

This means it sinks (averaged to be per hour) 6.45TW per hour (Huron sinks 20.26TW in comparison); 154.7TWh/day from the sun, compared to 0.176TWh from Pickering.



A comment also mentioned the fact that the Great Lakes have water inflows of 10-16,000 cubic meters of water per second. Ergo, the impact is even lower than just based on surface area.
 
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So playing devils advocate...

You state the earth receives 8,160 Wh per square meter in a 24 hour period. Does that hit uniformly over the surface of the earth? Does it all actually make it to the surface of the earth (like the surface of Lake Huron?) What factors reduce it and how does that affect the calculations you've provided? (Hint: the number is different at the equator than it is at higher latitudes, and the number provided is only for a clear day).

Next question: How many other thermal sources are there to Lake Huron and do they have a cumulative effect over time?

Next one: What is the long term trend in Lake Huron (or Lake Ontario) water temperatures?
 

OVERKILL

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So playing devils advocate...

You state the earth receives 8,160 Wh per square meter in a 24 hour period. Does that hit uniformly over the surface of the earth?
No, that's just the average, obviously it's higher closer to the equator and lower as you move away from it.
Does it all actually make it to the surface of the earth (like the surface of Lake Huron?)
No, of the (average) 1,361 watts per square meter that hits the atmosphere, some of it doesn't make it through, and of course there are other things like cloud cloud cover, smog, fog...etc that can impact it.

That being said, the 1,361W is the average over the entire earth's atmosphere, over the course of a year. If we go by the "makes it through" value, that brings us down to about 1,000W per square meter (250W per hour over a 24hr period, averaged over the year). But again, that's the average over the entire earth including everything from the poles to the equator.
What factors reduce it and how does that affect the calculations you've provided? (Hint: the number is different at the equator than it is at higher latitudes, and the number provided is only for a clear day).
Obviously there will be some variability but it doesn't change the calculations much. Let's say we re-ran the math using the aforementioned 250W per square meter, we get 14.9TW per hour absorbed by the lake from the sun; 357.6TWh per day, vs 0.376TWh from the plant. The difference between the numbers is so huge it doesn't really matter.
Next question: How many other thermal sources are there to Lake Huron and do they have a cumulative effect over time?
Bruce is the only large thermal plant I know of on Huron, unless there are some state-side (which is certainly possible).

Your second question isn't really relevant, given we know that the sun, and inflows, would be what drive lake temperature change. A particularly cold winter would likely mean a very cold spring/summer lake temp relative to a mild winter for example. The lake doesn't start to "see heat" (bulk lake temp) until mid summer, it takes that long, at the amount of sun exposure we are discussing, to really start pushing up lake temperature, and even then, the temp of the water being drawn in by the plant isn't much off freezing (bottom of the lakes are around 3C).
Next one: What is the long term trend in Lake Huron (or Lake Ontario) water temperatures?
The EPA tracks these, they appear to be pretty consistent since 1995:
1664158512381.png


Of note, 2014 was a particularly cold winter in Ontario. You can see the 2014 temperature dip in every single lake, which supports what I stated earlier.
 
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From my source:

"If we average out over an entire 24 hour cycle the amount of solar radiation hitting the Earth’s surface (known as the solar irradiance) on a clear day at the equator on the equinox is approximately 340 W/m2."

Source: https://explainingscience.org/2019/03/09/solar-energy/

340 W/m2 = 8160 Wh/m2/day (conveniently matches the number you've supplied).

Again, that is at the equator. Not at the latitude of Lake Huron (or Ontario). On a clear day.

So again, what the amount of energy that makes it to the surface at Lake Huron?

(Most sources that take this down to a daily average for the latitudes of Lake Huron will be closer to 3150 Wh/m2/day - taking into account cloud cover, water vapor, latitude effects, etc...)

As an example, one viewer of data:


Still stand by the 8160 Wh/m2/day number?
 
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I watch the odd fishing show and they do like to fish around the cooling outlets of the large thermal plants, as it attracts the warm water species early or later in the seasons.
The outlets are a point source of heat, and the heat certainly is never distributed across large areas of the whole lake like the sun, also the currents and dissipation pattern would be interesting to study and see if they have changed the local ecosystem. I suspect a small portion of the lake is probably effected quite a bit, but I don't think its a reason to prevent a plant from being built on a great lake or a large river.
I imagine a medium size river with summer water temps close to the max for trout, could be be heated that extra bit on a hot summer day to start to effect their populations.
Also as a side note, in our pond we've found that its a succession of warm humid nights over 20C that really heat up the water to the point our rainbow trout start to die off. The sun is the big heat source but a cool dry night seems to pull a lot of heat out again.
 
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In regards to lake trends, other papers show lake surface temperatures increasing. One example with data from 1973-2013:

1664161252325.jpg


From:


Page 16. Parts of Lake Huron show a positive increase in surface water temperature over time. Is that air temp related? Input source related? All of the above?

Or from the same data you used, if you download and analyze the data and not hide it in the large scale axis, a trend of temp increase can be seen in that dataset as well.
 

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From my source:

"If we average out over an entire 24 hour cycle the amount of solar radiation hitting the Earth’s surface (known as the solar irradiance) on a clear day at the equator on the equinox is approximately 340 W/m2."

Source: https://explainingscience.org/2019/03/09/solar-energy/

340 W/m2 = 8160 Wh/m2/day (conveniently matches the number you've supplied).

Again, that is at the equator. Not at the latitude of Lake Huron (or Ontario). On a clear day.
OK, from Wikipedia:
The average annual solar radiation arriving at the top of the Earth's atmosphere is about 1361 W/m2. This represents the power per unit area of solar irradiance across the spherical surface surrounding the sun with a radius equal to the distance to the Earth (1 AU). This means that the approximately circular disc of the Earth, as viewed from the sun, receives a roughly stable 1361 W/m2 at all times. The area of this circular disc is πr2, in which r is the radius of the Earth. Because the Earth is approximately spherical, it has total area 4πr2, meaning that the solar radiation arriving at the top of the atmosphere, averaged over the entire surface of the Earth, is simply divided by four to get 340 W/m2.

Note that this is not at the equator, it's the average over the whole planet.

We have the same two numbers here, but your source is claiming this is only at the equator, while mine is claiming this is the average over the whole planet. That appears to be the disconnect.
So again, what the amount of energy that makes it to the surface at Lake Huron?
Using Wikipedia again:
Average annual solar radiation arriving at the top of the Earth's atmosphere is roughly 1361 W/m2.[32] The Sun's rays are attenuated as they pass through the atmosphere, leaving maximum normal surface irradiance at approximately 1000 W/m2 at sea level on a clear day. When 1361 W/m2 is arriving above the atmosphere (when the sun is at the zenith in a cloudless sky), direct sun is about 1050 W/m2, and global radiation on a horizontal surface at ground level is about 1120 W/m2.[33] The latter figure includes radiation scattered or reemitted by the atmosphere and surroundings. The actual figure varies with the Sun's angle and atmospheric circumstances. Ignoring clouds, the daily average insolation for the Earth is approximately 6 kWh/m2 = 21.6 MJ/m2.

Which works out to 250W per square meter.
(Most sources that take this down to a daily average for the latitudes of Lake Huron will be closer to 3150 Wh/m2/day - taking into account cloud cover, water vapor, latitude effects, etc...)

As an example, one viewer of data:


Still stand by the 8160 Wh/m2/day number?
I think it would be better to use the 250W per square meter figure, though your 3,150W is worth running the math with. This gives us 187.84TWh/day, vs 0.376TWh for the plant. Still insignificant; basically a rounding error.
 
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Again, I am playing devils advocate. I understand the point you are trying to make - look, its only a drop in the bucket, so its all good. Move along, nothing to see here...

There is an external thermal consequence to a resource here. I'm not saying its good or bad. We have / had many operations that use large waterbodies for thermal cooling, similar to your example. Are they better or worse than traditional cooling towers, etc? I'm not going to get into that argument.

Long term, when temps start moving in waterbodies of this size and scale, do we not think there may be other, unintended consequences? Maybe the better question is whether those consequences are better or worse than other choices.

But arguing that there is no external loading or "its just a drop in the bucket" is like old school pollution engineering - the solution to pollution is dilution - until there are so many drops in the bucket...
 
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Similar to a poster above, and in line with the point that you make - the intake is a deep water intake. How about the outfall? Is that dispersed? Is it reasonable to assume that the entire lake is receiving the thermal load equally or are there more localized affects?
 

OVERKILL

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In regards to lake trends, other papers show lake surface temperatures increasing. One example with data from 1973-2013:

View attachment 118555

From:


Page 16. Parts of Lake Huron show a positive increase in surface water temperature over time. Is that air temp related? Input source related? All of the above?

Or from the same data you used, if you download and analyze the data and not hide it in the large scale axis, a trend of temp increase can be seen in that dataset as well.
Well, air temp is trending up slightly over time:
1664162457283.jpg


Which would make sense if that correlated with water temp to some degree.

Interesting graphic (of the same data), but it seems to show the biggest changes happening in Superior and very little change in Huron and Ontario with basically none in Erie. All our thermal plants are in the light yellow areas FWIW.
 
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The light yellow areas are all a positive temperature trend, FWIW. (ie: greater than zero). How much? I don't have the data.

Source of the air graph you provided appears to be:


Which also has another figure, seems to show the average air temperature increase in that time period is about 0.015 Degrees Farenheight per year.

1664163664321.jpg
 
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OVERKILL

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Again, I am playing devils advocate. I understand the point you are trying to make - look, its only a drop in the bucket, so its all good. Move along, nothing to see here...
My point is simply that the biggest factor in lake temperature for large bodies like Huron, is the sun. You start looking at rivers or smaller bodies, and that factor is greatly reduced.
There is an external thermal consequence to a resource here. I'm not saying its good or bad. We have / had many operations that use large waterbodies for thermal cooling, similar to your example. Are they better or worse than traditional cooling towers, etc? I'm not going to get into that argument.
Well, there are more than one external thermal consequence in play ;) We have inflow temperature from Superior, we have of course the sun, we have ambient air temperature, air flow (wind) and of course we have these other inputs too.

Cooling towers are used where the resource isn't big enough to support OTC. Both designs are equally traditional, we just didn't use cooling towers because all our large thermal plants were on the great lakes. It isn't really an argument as much as it is a design choice, which should be made based on the best data available at the time.
Long term, when temps start moving in waterbodies of this size and scale, do we not think there may be other, unintended consequences? Maybe the better question is whether those consequences are better or worse than other choices.
But that's a global trend (warming), it's not isolated to the Great Lakes. You can see it in the air temp graph too.
But arguing that there is no external loading or "its just a drop in the bucket" is like old school pollution engineering - the solution to pollution is dilution - until there are so many drops in the bucket...
In this case, it's like peeing in an olympic sized swimming pool. Is there some local warming? Yes. Is it detectable? Yes. Is it going to meaningfully change the temperature of the pool? No. If the pool is outside, the sun and ambient temperature are ultimately what are going to have an impact.
 
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OVERKILL

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The light yellow areas are all a positive temperature trend, FWIW. (ie: greater than zero). How much? I don't have the data.
There's a legend. The light yellow is the lowest value above, grey, which is "no trend".
- Most of Erie is "no trend"
- Huron and Ontario have large sections of light yellow (0.01 degrees F to 0.18 degrees F, which is a pretty big range if we are being honest)
- Superior has a sizeable section that's orange (0.28-0.36F)
- Superior has a small section that's light red (0.37-0.45F)
 

OVERKILL

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I watch the odd fishing show and they do like to fish around the cooling outlets of the large thermal plants, as it attracts the warm water species early or later in the seasons.
The outlets are a point source of heat, and the heat certainly is never distributed across large areas of the whole lake like the sun, also the currents and dissipation pattern would be interesting to study and see if they have changed the local ecosystem. I suspect a small portion of the lake is probably effected quite a bit, but I don't think its a reason to prevent a plant from being built on a great lake or a large river.
Yes, it's, on average, a 3C rise between inlet/outlet (at Bruce), and that warmer water, particularly late in the season when the lake is getting cold and surface water temp drops, attracts fish.
I imagine a medium size river with summer water temps close to the max for trout, could be be heated that extra bit on a hot summer day to start to effect their populations.
Also as a side note, in our pond we've found that its a succession of warm humid nights over 20C that really heat up the water to the point our rainbow trout start to die off. The sun is the big heat source but a cool dry night seems to pull a lot of heat out again.
Yeah, if the heat can't dissipate over the night (hot, humid nights) the temp of the pond will just keep going up.

On a river or something smaller, you'd want to use evaporative cooling (cooling towers) to minimize water volume pulled from the lake/river. OTC is really only suitable for large bodies and ocean-facing plants.
 
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You don't need to attempt to insult me.

Your words:

All our thermal plants are in the light yellow areas FWIW.

Does the legend state that the light yellow areas have a postive , no trend, or negative rate of temperature change?

That was the point.

Are rising air temps in the Lake Huron basin due to air temp changes? Due to water temp changes? Or due to changes in ice coverage and patterns (which is a large player in Superior's surface water temp changes...)
 

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Similar to a poster above, and in line with the point that you make - the intake is a deep water intake. How about the outfall? Is that dispersed? Is it reasonable to assume that the entire lake is receiving the thermal load equally or are there more localized affects?
You can see the outflow in the picture in the OP, in fact, I pointed it out specifically.

This is something that has evolved over time.

Our oldest plants (all thermals, not just nuclear) used near-shore inlets and outlets. Second generation plants (like Bruce) used deep water inlets to get colder inlet water, which is more effective, but still let that water out near shore.

Our newest plant, Darlington, has both a deepwater inlet, as well as a deepwater outlet diffuser:
Screen Shot 2022-09-25 at 11.51.43 PM.jpg

Screen Shot 2022-09-25 at 11.52.31 PM.jpg
 

OVERKILL

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You don't need to attempt to insult me.
No insult was attempted, if this is going sideways, I'll have the thread locked, I honestly thought you didn't see the legend.
Your words:

All our thermal plants are in the light yellow areas FWIW.
Yes, and those yellow areas cover most of the lakes in question, while Superior, which doesn't have any plants on its northern border, is clearly experiencing the biggest changes and is upstream from all of these other lakes. Yes, the plants are in the yellow section, but, as I said, that's most of the lake(s). It would be difficult for them not to be.
Screen Shot 2022-09-25 at 11.56.09 PM.jpg

Subsequently, not seeing the "gotcha" you seem to think this is?
Does the legend state that the light yellow areas have a postive , no trend, or negative rate of temperature change?

That was the point.
Again, that's almost the entire lake with Huron and Ontario. Yet there are no thermal plants on the northern shore of Superior, and it's clearly the most affected.
Are rising air temps in the Lake Huron basin due to air temp changes? Due to water temp changes? Or due to changes in ice coverage and patterns (which is a large player in Superior's surface water temp changes...)
Perhaps all of the above. Superior is by far the biggest lake, and the source of most of the water for all of the others, so if it is getting warmer, that's going to have a trickle-down effect.
 

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In regards to lake trends, other papers show lake surface temperatures increasing. One example with data from 1973-2013:

View attachment 118555

From:


Page 16. Parts of Lake Huron show a positive increase in surface water temperature over time. Is that air temp related? Input source related? All of the above?

Or from the same data you used, if you download and analyze the data and not hide it in the large scale axis, a trend of temp increase can be seen in that dataset as well.
I found the original source for this (they reference it) which has some more information that you might find beneficial:

This is USGCRP, 2018, as noted in the reference for your link.

They note:
Lake-surface temperatures increased during the period 1985–2009 in most lakes worldwide, including the Great Lakes.196 The most rapid increases in lake-surface temperature occur during the summer and can greatly exceed temperature trends of air at locations surrounding the lakes.197 From 1973 to 2010, ice cover on the Great Lakes declined an average of 71%;14 although ice cover was again high in the winters of 2014 and 2015,192 a continued decrease in ice cover is expected in the future.198,

Note the high ice cover in 2014 (which was a particularly cold winter as I noted earlier) which also meant a cooler year for lake temps. Also note that this appears to be a worldwide trend. There's also a paragraph that follows this on water level, which includes the impact of a warm winter, and increased sunlight reaching the lake:

Water levels in the Great Lakes fluctuate naturally, though levels more likely than not will decline with the changing climate.200 A period of low water levels persisted from 1998 to early 2013. A single warm winter in 1997–1998 (corresponding to a major El Niño event) and ongoing increases in sunlight reaching the lake surface (due to reduced cloud cover) were likely strong contributors to these low water levels.11 Following this period, water levels rose rapidly. Between January 2013 and December 2014, Lake Superior’s water rose by about 2 feet (0.6 meters) and Lakes Michigan and Huron’s by about 3.3 feet (1.0 meter).201 Recent projections with updated methods of lake levels for the next several decades under 64 global model-based climate change simulations (from the Coupled Model Intercomparison Project Phase 5, or CMIP5 database, using the RCP4.5, RCP6.0, and RCP8.5 scenarios) on average show small drops in water levels over the 21st century (approximately 6 inches for Lakes Michigan and Huron and less for the other lakes), with a wide range of uncertainty.200

I recommend reading the whole thing, it's quite good.

I am going to see if I can find the raw data so we can get a better idea of the temperature trends.
 

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OK, following sources through sources, I got to the following document:

Which cites the Sharma et al. [2015] database. Which I am going to try and locate, as that's the source for these:

Huron has two references:
45.35 x -82.84 - 25 years of data - Lake SSWT trend is 0.85 degrees (C) per decade
44.76 x -82.33 - 24 years of data - Lake SSWT trend is 0.44 degrees (C) per decade

Superior has two references:
47.58 x -86.59 - 25 years of data - Lake SSWT trend is 1.16 degrees (C) per decade
48.05 x -87.10 - 21 years of data - Lake SSWT trend is 0.80 degrees (C) per decade

Ontario has one reference:
43.63 x -77.62 - 23 years of data - Lake SSWT trend is 0.33 degrees (C) per decade

Hopefully I can get that database and graph it.

EDIT:
Found it:
 
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