09-29-2003, 06:29 PM
Hi,
The numbers I gave are how much energy would have to be transferred to increase that temperature, which is quite different to the ammount of energy used by an office.
From the post I replied to:
Unless they have a way of pumping over 2 million lightbulb years of energy into the lake in a short time, I don't think we can worry about the temerature change much.
Had you stuck with just the numbers, I would have ignored it. The conclusion you came to (in bold above) is what I'm attacking. You saw a big number (2 million light bulbs) and were impressed. You tacitly assumed that they couldn't get that many "lightbulbs" hooked up through HVAC systems to a lake. I showed that it could easily be done and that your assumption was poor.
As to the rest of your quibbles, it doesn't matter. We're not talking precise numbers, we're talking reasonable approximations. A person puts out about the same amount of heat as a 60 to 100 watt light bulb, a computer with monitor puts out about the same as one or two such bulbs, a person at a workspace has two or more four foot fluorescent bulbs overhead and typically one or more "task" lights. Plus there are copiers, printers, coffee pots, etc. How accurate is my estimate? Probably a factor of 5 one way or the other, good enough for this discussion.
Oh, and *all* the energy used eventually turns into heat. That's what the second law of thermodynamics is all about. And most of it turns to heat pretty fast.
Now, the dissipation, . . .
Bah. Again we are talking averages. Sure, if you want the temperature to be between 70 and 72F and it happens to be 71F outside, you don't need heating or air-conditioning. (That's actually a simplification. The actual outside temperature that gives optimal inside conditions is determined by how much heat is being produced in the building and how rapidly that heat can be removed through windows, fans, ducts and all that. But the principle still applies.) So, what fraction of the time will this happen? In Pullman Washington, the summer average temperature was an "ideal" 70F -- until you realized that this was the result of 90F degree days and 50F degree nights. :)
So, 3 years to change, that's assuming that no energy whatsoever leaves the lakes, as someone has already mentioned, the water flows out of Lake Ontario, as I've already mentioned, heat will conduct and convect out of the water. And what of winter? when the buildings won't have to be cooled so much, but the weather will be cooler, sapping the heat back out of the lakes, the total cycle will take longer and that's if it ever happens at all.
Again, bah. We're looking at order of magnitude calculations here. These are smaller effects, they would change an exact result but have little effect on the approximation used. Second, thermodynamics rears its ugly head again. Whether we're talking of changing the overall temperature of the lake by .03 or 3 degrees per year is not the issue. The issue is that we are changing the temperature by an amount that is considerable over a short time. As to the turnover of the water, what percentage of the water is replaced per year? That, to a first approximation, is the amount of excess heat being carried away. So, if it is less than 20% of the total, it is of no importance in a first order calculation.
What might have been a better idea is if they found some way to use it to heat water for the city or another heat pump can be used to turn that heat into electricity
In looking at all solutions of this type, the energy cost of implementing the measures must be considered as part of the total. For instance, say we have a fan motor that uses 1000 kW-hr per year. Let's assume that a newer model is more efficient and will do the job for 950. Let's further say that the expected life of the motor is ten years. So, unless the new motor can be manufactured (including mining, transportation, etc.) for less than 500 kW-hr, it is an energy *loss* to replace it -- the energy costs are simply being passed back up the line. Usually it is the monetary costs that are considered, but they (very) roughly are commensurate.
It can't be a totally stupid idea, otherwise they wouldn't be trying it.
Yes, it could. Sometimes the only choices are between stupid ideas. Often because the "smart" idea cannot be implemented for political or social reasons. We are in the environmental situation that we are because our ability to reduce infant mortality outstripped our attitudes about having children. Thus the huge families of the late nineteenth and early twentieth century. Before that, nature took care of family size. Now, in many parts of the world, society has finally caught on (however, it seems that the regions that can least afford overpopulation are the ones that contribute to it the most).
"Totally stupid"? How about harvesting old growth timber at the rate of 15 to 20% a year when the replacement rate is about 0.2% a year? How about destroying the fishing grounds that are your livelihood by overfishing? How about moving 50 miles from your place of work and then burning 500 gallons of gas a year (not to mention 700 hours) getting to and from work? People do a lot of "totally stupid" things because of factors that they overlook, ignore, or that really change the "stupidity" of what they are doing.
The final analysis: the population of an area is growing, thus more living and working spaces are required. They need to have some form of temperature control to be comfortable. What solutions are they and how much does each hurt the environment? There are no good solutions, just bad and worse.
--Pete
The numbers I gave are how much energy would have to be transferred to increase that temperature, which is quite different to the ammount of energy used by an office.
From the post I replied to:
Unless they have a way of pumping over 2 million lightbulb years of energy into the lake in a short time, I don't think we can worry about the temerature change much.
Had you stuck with just the numbers, I would have ignored it. The conclusion you came to (in bold above) is what I'm attacking. You saw a big number (2 million light bulbs) and were impressed. You tacitly assumed that they couldn't get that many "lightbulbs" hooked up through HVAC systems to a lake. I showed that it could easily be done and that your assumption was poor.
As to the rest of your quibbles, it doesn't matter. We're not talking precise numbers, we're talking reasonable approximations. A person puts out about the same amount of heat as a 60 to 100 watt light bulb, a computer with monitor puts out about the same as one or two such bulbs, a person at a workspace has two or more four foot fluorescent bulbs overhead and typically one or more "task" lights. Plus there are copiers, printers, coffee pots, etc. How accurate is my estimate? Probably a factor of 5 one way or the other, good enough for this discussion.
Oh, and *all* the energy used eventually turns into heat. That's what the second law of thermodynamics is all about. And most of it turns to heat pretty fast.
Now, the dissipation, . . .
Bah. Again we are talking averages. Sure, if you want the temperature to be between 70 and 72F and it happens to be 71F outside, you don't need heating or air-conditioning. (That's actually a simplification. The actual outside temperature that gives optimal inside conditions is determined by how much heat is being produced in the building and how rapidly that heat can be removed through windows, fans, ducts and all that. But the principle still applies.) So, what fraction of the time will this happen? In Pullman Washington, the summer average temperature was an "ideal" 70F -- until you realized that this was the result of 90F degree days and 50F degree nights. :)
So, 3 years to change, that's assuming that no energy whatsoever leaves the lakes, as someone has already mentioned, the water flows out of Lake Ontario, as I've already mentioned, heat will conduct and convect out of the water. And what of winter? when the buildings won't have to be cooled so much, but the weather will be cooler, sapping the heat back out of the lakes, the total cycle will take longer and that's if it ever happens at all.
Again, bah. We're looking at order of magnitude calculations here. These are smaller effects, they would change an exact result but have little effect on the approximation used. Second, thermodynamics rears its ugly head again. Whether we're talking of changing the overall temperature of the lake by .03 or 3 degrees per year is not the issue. The issue is that we are changing the temperature by an amount that is considerable over a short time. As to the turnover of the water, what percentage of the water is replaced per year? That, to a first approximation, is the amount of excess heat being carried away. So, if it is less than 20% of the total, it is of no importance in a first order calculation.
What might have been a better idea is if they found some way to use it to heat water for the city or another heat pump can be used to turn that heat into electricity
In looking at all solutions of this type, the energy cost of implementing the measures must be considered as part of the total. For instance, say we have a fan motor that uses 1000 kW-hr per year. Let's assume that a newer model is more efficient and will do the job for 950. Let's further say that the expected life of the motor is ten years. So, unless the new motor can be manufactured (including mining, transportation, etc.) for less than 500 kW-hr, it is an energy *loss* to replace it -- the energy costs are simply being passed back up the line. Usually it is the monetary costs that are considered, but they (very) roughly are commensurate.
It can't be a totally stupid idea, otherwise they wouldn't be trying it.
Yes, it could. Sometimes the only choices are between stupid ideas. Often because the "smart" idea cannot be implemented for political or social reasons. We are in the environmental situation that we are because our ability to reduce infant mortality outstripped our attitudes about having children. Thus the huge families of the late nineteenth and early twentieth century. Before that, nature took care of family size. Now, in many parts of the world, society has finally caught on (however, it seems that the regions that can least afford overpopulation are the ones that contribute to it the most).
"Totally stupid"? How about harvesting old growth timber at the rate of 15 to 20% a year when the replacement rate is about 0.2% a year? How about destroying the fishing grounds that are your livelihood by overfishing? How about moving 50 miles from your place of work and then burning 500 gallons of gas a year (not to mention 700 hours) getting to and from work? People do a lot of "totally stupid" things because of factors that they overlook, ignore, or that really change the "stupidity" of what they are doing.
The final analysis: the population of an area is growing, thus more living and working spaces are required. They need to have some form of temperature control to be comfortable. What solutions are they and how much does each hurt the environment? There are no good solutions, just bad and worse.
--Pete
How big was the aquarium in Noah's ark?