4 ms·

I’m in the 98% not feasible category for a few reasons. I’m open to new information or arguments, but I can’t see a way over a few very large hurdles. 1. Pave

by Nbox9 5y ago

I’m in the 98% not feasible category for a few reasons. I’m open to new information or arguments, but I can’t see a way over a few very large hurdles. 1. Pavement is a very poor conductor, energy doesn’t move easily through it. 2. The Delta between ambient air temp and pavement temp low. Generating power would most likely include moving energy between the higher temp pavement to the lower temp air and capturing some of it during the transition. This is possible at any delta, but were really talking about a maximum of about 30 degree C temperature delta. 3. There are more efficient ways to generate power. Build wind turbines, solar panels, dams, etc. These are all very good ways of generating power. 4. There are more efficient ways to keep pavement cool. Change the pavement materials, plant trees, build shade sources for the pavement.

na85 5y ago
>Pavement is a very poor conductor, energy doesn’t move easily through it. Oh dear I'm certainly not proposing running electricity through the pavement itself. I'm suggesting you harvest the heat from the asphalt with e.g. a thermocouple and use that to produce a voltage. >The Delta between ambient air temp and pavement temp low. Perhaps, but not between the pavement and the soil a foot or so underneath.
- agurk 5y ago
  Conductor can be used to describe more energy types than electricity. In this case they were referring to heat energy. This would be important as if you moved the energy from the hot pavement to a cold source you're cooling the small part where you're taking heat from. As pavement is a poor heat conductor all the energy in the surrounding mass of pavement would flow only very slowly to the patch you were using. This would severly limit your ability to move heat and therefore generate electricity. This is also why using the ground as the cold sink isn't a great idea. Once you have moved the heat energy to the ground it sits there only slowly moving away. This is why the ground is noticeably cooler just a foot beneath the hot pavement. Once your cold source is warm, the ability to move heat is again limited. Air is also a bad conductor of heat, but as it's a gas it can move. So once you heat up some cool air it will become less dense and move away. This is convection.
  - Nbox9 5y ago
    Confirming that I was using conductor to mean heat transfer instead of electrical transform. You could theoretically build a power plant by building a pipe through the pavement (does this reduce the structural integrity of the pavement?) or directly underneath and touching (surface area and high heat transfer would be the desired quality of the pipe). Inside the pipe is a liquid and a set of conditions such that as the liquid heats up next to the pavement it will turn into a gas. You could then capture the extra pressure generated by the gas via a turbine. There would be a condensing section of pipe (typically above the boiling section so gravity can move the cool liquid back down) so it’s a closed system. The primary problems with this setup are: 1. You’d have to change the liquid or change the pressure inside of the tube to adjust for the difference in temperature. Imagine a place like Houston where the pavement might be 150F or it might be 50F. The conditions of the power plant vary. 2. The material cost is stupid high for the amount of power it would generate. It would probably be a better use of materials to capture the heat waste of kitchens boiling water. 3. The labor cost is stupid high for the amount of power it would generate. 4. I’m really concerned about how this will change fundamental goal of pavement (to provide a solid, long living, smooth material for roads and building foundations.). It’s actually possible that reducing the size of the heat fluctuations will make the material more stable. I think it’s just as likely that adding complexity to the system will make the pavement less stable, but if you are going for the 2% of doubt a reduction in maintenance cost would be able to modify the $/Watt function you’d be fighting wind/solar/hydro for. I’d really like to stress than 2 and 3 will combine to make Wind 10x-1000x cheaper.

by Nbox9 5y ago

na85 5y ago

>Pavement is a very poor conductor, energy doesn’t move easily through it. Oh dear I'm certainly not proposing running electricity through the pavement itself. I'm suggesting you harvest the heat from the asphalt with e.g. a thermocouple and use that to produce a voltage. >The Delta between ambient air temp and pavement temp low. Perhaps, but not between the pavement and the soil a foot or so underneath.

agurk 5y ago
Conductor can be used to describe more energy types than electricity. In this case they were referring to heat energy. This would be important as if you moved the energy from the hot pavement to a cold source you're cooling the small part where you're taking heat from. As pavement is a poor heat conductor all the energy in the surrounding mass of pavement would flow only very slowly to the patch you were using. This would severly limit your ability to move heat and therefore generate electricity. This is also why using the ground as the cold sink isn't a great idea. Once you have moved the heat energy to the ground it sits there only slowly moving away. This is why the ground is noticeably cooler just a foot beneath the hot pavement. Once your cold source is warm, the ability to move heat is again limited. Air is also a bad conductor of heat, but as it's a gas it can move. So once you heat up some cool air it will become less dense and move away. This is convection.
- Nbox9 5y ago
  Confirming that I was using conductor to mean heat transfer instead of electrical transform. You could theoretically build a power plant by building a pipe through the pavement (does this reduce the structural integrity of the pavement?) or directly underneath and touching (surface area and high heat transfer would be the desired quality of the pipe). Inside the pipe is a liquid and a set of conditions such that as the liquid heats up next to the pavement it will turn into a gas. You could then capture the extra pressure generated by the gas via a turbine. There would be a condensing section of pipe (typically above the boiling section so gravity can move the cool liquid back down) so it’s a closed system. The primary problems with this setup are: 1. You’d have to change the liquid or change the pressure inside of the tube to adjust for the difference in temperature. Imagine a place like Houston where the pavement might be 150F or it might be 50F. The conditions of the power plant vary. 2. The material cost is stupid high for the amount of power it would generate. It would probably be a better use of materials to capture the heat waste of kitchens boiling water. 3. The labor cost is stupid high for the amount of power it would generate. 4. I’m really concerned about how this will change fundamental goal of pavement (to provide a solid, long living, smooth material for roads and building foundations.). It’s actually possible that reducing the size of the heat fluctuations will make the material more stable. I think it’s just as likely that adding complexity to the system will make the pavement less stable, but if you are going for the 2% of doubt a reduction in maintenance cost would be able to modify the $/Watt function you’d be fighting wind/solar/hydro for. I’d really like to stress than 2 and 3 will combine to make Wind 10x-1000x cheaper.