General > General Technical Chat
Window screens
EPAIII:
OK, Mosquitoes! Never mind any of the exaggerated stories about mosquitoes big enough to saddle and ride. Never mind about 10,000 pounds of fuel being loaded in one. How about a 100% real and COMPLETELY TRUE mosquito story. Mine, and it really did happen. And no exaggeration on the size of them. They were little, small, standard mosquitoes.
I was born and lived the first two decades of my life in Louisiana, on the outskirts of New Orleans. And we had mosquitoes. Just plain, ordinary, smallish mosquitoes. It was a fact of life there and no big deal. Window screens? Heck yes. There were even trucks with fogging machines that would try to eliminate them in your neighborhood if someone paid for it. It did not work well, but people still paid.
One day in the 1960, probably a Friday, after finishing my last class at college I decided to take a ride outside of town. I came to an old fort on the shore line of the Gulf of Mexico a short time before sunset. I got out of the car and walked toward the water. I got half way there (50 meters/yards) and looked at my arm. I am a white skinned and was wearing a short sleeve shirt. And my arm was BLACK. Both my arms were SOLID BLACK. Both arms were almost completely covered with mosquitoes. And they were all biting me.
I wiped them off while turning around and RUNNING as fast as I could back to the car. I don't know how many times I wiped them off my arms but the number got less as I approached the car and got further from the water. I was seriously worried for my very life. I had no idea how many mosquito bites I could endure. I didn't count, but must literally have killed many thousands of them in only a minute or two.
When I got in the car I wiped them off my arms and face and scrambled for the spray can of flying bug spray I had. I probably came close to choking on the bug spray, but I only wanted to kill every last one inside the car. And I drove back home as fast as I could.
Not monsters. Not even the largest mosquitoes I have ever seen. I have seen far larger ones. But thousands and thousands and thousands of them; the shear number of them scared the daylights out of me.
I have traveled around and lived in other parts of the country (the US) and even visited/lived in a couple of others, but have never, ever seen mosquitoes like that any where else. And I never, ever want to.
That's my mosquito story. It is 100% true. I swear it. Not a single syllable of exaggeration. And I really was scared for my very life.
So you can have your Texas mosquitos. Your western mosquitos. Your eastern mosquitos. Your mosquitos from any other area of the world. I don't care about how big they are. Louisiana mosquitos have them beat in shear NUMBERS. And if you don't believe me, I will take you to that coastal Louisiana fort one summer afternoon. But I am staying in the car.
MK14:
--- Quote from: EPAIII on June 12, 2023, 09:41:15 am ---Five words:
The second law of thermodynamics.
--- Quote from: MK14 on June 08, 2023, 01:18:52 am ---
--- Quote from: james_s on June 08, 2023, 12:19:26 am ---
--- Quote from: MK14 on June 07, 2023, 11:32:46 pm ---Pity we can't just invent something, which can turn heat (temperature) as opposed to temperature differences, into electricity. Saving burning so much fossil fuels and reducing the global temperatures (maybe or maybe not, as that electricity would eventually be turned back into heat, when it is used, typically).
--- End quote ---
That's kind of how physics works though. Heat is a bit like static electricity, unless the heat (or electricity) is flowing somewhere, no work is getting done.
--- End quote ---
My understanding, is that it might be theoretically possible.
Example:
You use a very high efficiency heat pump, to turn the existing temperature into a temperature difference, perhaps using a fifth (or hopefully higher) of the electrical energy, that would have been needed, to create the heating (temperature increase) using resistive heating elements.
You then use that temperature difference to power a thermopile https://en.wikipedia.org/wiki/Thermoelectric_generator with perhaps an ...
--- Quote ---efficiency is approximately 33-37%
--- End quote ---
can be used. Then it might be possible, eventually, to make realistic ones, which can 'profitably' extract electricity, out of pure/fixed temperature.
Just that they need to invent, practicable heat-pumps and thermopiles, with the necessary high enough efficiencies, over compatible temperature ranges.
But don't worry. I've heard about and/or spoken to one or more people, who strongly think that the Physics of what I just said, is relatively impossible and it would never work.
Anyway, as a backup solution. Perhaps fusion power will be invented one day (by that I mean our own fusion generators, excluding calling solar cells/panels fusion as they use the suns natural fusion energy system).
--- End quote ---
--- End quote ---
I've enlarged and set bold, for the bit, I'm replying to, at the very top.
Here is an explanation, of why the heat pumps, I was describing, don't violate the second law of thermodynamics.
--- Quote ---Heat pumps operate as a heat engine in reverse, as they do work from an input of electricity to push heat from a cold place to a warm place. This would seemingly violate the Second law of thermodynamics, but the key reason it doesn't is because this heat transfer is not spontaneous; it requires an input of energy to do so.
--- End quote ---
Source:
https://energyeducation.ca/encyclopedia/Heat_pump
MK14:
--- Quote from: EPAIII on June 12, 2023, 09:33:57 am ---CO2 is not a pollutant. It is an absolute necessity for plant life.
CO2 levels are just barely just above their all time, in the entire history of the planet, low level. If we remove much of it, we will need a new food source because the plants will start dying out. And then the animals. And then, guess who!
Oh, and the oxygen, which the plants make, will run out too! Choke! Gasp!
Somebody needs to actually think this thing out. NOW!
--- End quote ---
It really needs someone who can explain the details of global warming, which also is getting too off-topic.
I was only suggesting reducing the CO2 levels, down to whatever it needs to be, to restore this planet back to normality. NOT a total elimination of all CO2.
Zero999:
--- Quote from: MK14 on June 12, 2023, 10:42:15 am ---Here is an explanation, of why the heat pumps, I was describing, don't violate the second law of thermodynamics.
--- Quote ---Heat pumps operate as a heat engine in reverse, as they do work from an input of electricity to push heat from a cold place to a warm place. This would seemingly violate the Second law of thermodynamics, but the key reason it doesn't is because this heat transfer is not spontaneous; it requires an input of energy to do so.
--- End quote ---
Source:
https://energyeducation.ca/encyclopedia/Heat_pump
--- End quote ---
But the overall system you've described would violate the second law of thermodynamics, because the end result would be perpetual motion.
--- Quote ---You use a very high efficiency heat pump, to turn the existing temperature into a temperature difference, perhaps using a fifth (or hopefully higher) of the electrical energy, that would have been needed, to create the heating (temperature increase) using resistive heating elements.
--- End quote ---
As I stated in previous post the maximum efficiency of a heat engine is determined by the temperature differential, between the hot and cold sides, with respect to absolute zero. The reverse is also true with a heat pump. The closer the cold side is to absolute zero and the hotter, the hot side is, the more energy is required to shift the same amount of heat, which is also why it's impossible to cool something to 0 K because it would take an infinite amount of energy.
Note Carnot's theorem only determines the maximum efficiency. Real life heat engines never achieve the same efficiency. This means your heat engine wouldn't be able to make enough electricity to power your heat pump, to produce a great enough temperature difference.
MK14:
--- Quote from: Zero999 on June 12, 2023, 02:11:41 pm ---
--- Quote from: MK14 on June 12, 2023, 10:42:15 am ---Here is an explanation, of why the heat pumps, I was describing, don't violate the second law of thermodynamics.
--- Quote ---Heat pumps operate as a heat engine in reverse, as they do work from an input of electricity to push heat from a cold place to a warm place. This would seemingly violate the Second law of thermodynamics, but the key reason it doesn't is because this heat transfer is not spontaneous; it requires an input of energy to do so.
--- End quote ---
Source:
https://energyeducation.ca/encyclopedia/Heat_pump
--- End quote ---
But the overall system you've described would violate the second law of thermodynamics, because the end result would be perpetual motion.
--- Quote ---You use a very high efficiency heat pump, to turn the existing temperature into a temperature difference, perhaps using a fifth (or hopefully higher) of the electrical energy, that would have been needed, to create the heating (temperature increase) using resistive heating elements.
--- End quote ---
As I stated in previous post the maximum efficiency of a heat engine is determined by the temperature differential, between the hot and cold sides, with respect to absolute zero. The reverse is also true with a heat pump. The closer the cold side is to absolute zero and the hotter, the hot side is, the more energy is required to shift the same amount of heat, which is also why it's impossible to cool something to 0 K because it would take an infinite amount of energy.
Note Carnot's theorem only determines the maximum efficiency. Real life heat engines never achieve the same efficiency. This means your heat engine wouldn't be able to make enough electricity to power your heat pump, to produce a great enough temperature difference.
--- End quote ---
I agree with you. (with some lingering doubts, which could probably be resolved, if I spent ages researching it and perhaps performing experiments).
It seems, one of the effects is called COP (Coefficient of performance), see here:
https://en.wikipedia.org/wiki/Coefficient_of_performance
Which (after my rather quick read up on it, so could be a bit or more mistaken) limits the maximum efficiency of heat-pumps, to values which CAN'T exceed 100% over-all efficiency. Because if it did, it would violate a number of laws of Physics.
So in summary, I agree with you. It seems, it would break some fundamental laws of Physics, even if I don't yet 100% understand the full Physics explanations, on why it CAN'T happen.
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