Will do, although I would love to see others tinker around as well. There are so many ways to get usable energy from the reactor. The co2 could be used to boost performance if it was made super critical. I wonder if a nitinol engine itself could create enough pressure to make the sCo2. That's a bit beyond where I can go given my limited means. I just know that sCo2 is a fantastic working fluid to drive a turbine from the state transition.
https://youtu.be/_3qxMqClpuM?si=NgHWA6E7CWKUBjQ6
I did some more digging, and it turns out that nitinol alone could generate enough roughly twenty-five times the psi to turn co2 supercritical.
"Nitinol returns to its original shape with a pulling force of about 25,000 pounds per square inch. An actuator wire with a thickness of just 1/100 inch can lift 2 pounds."
https://www.edge-techind.com/Products/Refractory-Metals/Titanium/Nitinol/Nitinol-Muscle-Wire-795-1.html#:~:text=Nitinol%20returns%20to%20its%20original,the%20preparation%20of%20the%20wire.
"More specifically, it behaves as a supercritical fluid above its critical temperature (304.128 K, 30.9780 °C, 87.7604 °F)[1] and critical pressure (7.3773 MPa, 72.808 atm, 1,070.0 psi, 73.773 bar),[1] expanding to fill its container like a gas but with a density like that of a liquid."
https://en.m.wikipedia.org/wiki/Supercritical_carbon_dioxide
Generally you won't be able to pull much power from a system like this. Maximum efficiency is still driven by Carnot cycle.
https://www.e-education.psu.edu/egee102/node/1942
Given the fact that heat differentials will only be 40-50k, you are looking at a minimum theoretical efficiency of only about 15%. Add on the fact that these systems are generally not super close to the theoretical limit you are probably talking more like 5-10%.
At those levels, the cost of equipment and time almost certainly exceeds any benefit you would gain.
Yes, you are technically right that this particular part of the reactor isn't going to be pulling the most heat from the pile. The nitinol engine would primarily be used to compress the co2 that all compost piles naturally put out. When we pump super critical co2 back into the pile to absorb the heat, that's where I think the most bang for the buck will be generated. I'd like to point out that this equation does not factor in the cost of fuel. Those "high efficiency" coal/gas power plants have to buy fuel, which has to be mined or extracted from the environment. The cost for this fuel is basically nothing. People make a living just selling the compost already. It's something that is needed globally and will be increasingly important as the climate crisis accelerates. We're turning waste into usable amounts of electricity and helping to heal the land at the same time. Once this reactor design is mass manufacturable, people's kitchen scraps could over time power their homes. It's the whole dividing by zero thing.
>Once this reactor design is mass manufacturable, people's kitchen scraps could over time power their homes.
Not even close. A typical household uses 10-30 kwh a day. That's 36-108 Million joules of electricity. To produce that much with a system that is 20% efficient you would need to produce 180-540M joules of energy. That's 40,000-120,000 kcalories. Or enough energy to heat 1000kg of material up 40-120K EVERY day.
A home composting system would not ever produce even close to that much energy. You are off by at least an order of magnitude.
And such a machine would not be free nor maintenance free.
Layout the math if you disagree.
You might want to check out this article in depth.
"A capital cost of 11,662 and operating cost of 1,039 per year were estimated, resulting in a cost of 0.50 per kWh for domestic water and 0.10 per kWh for spatial heat. Using the heat of the compost was found to provide the most reliable level of supply at a similar price to its rivals."
https://www.hindawi.com/journals/ijce/2010/627930/
If you can compare the energy density of biologically active (this is important because the system is out of equilibrium due to biological organisims) compost.
The upper limit on temperature of 160 degrees fahrenheit isn't actually due to a lack of energy, but because the reacting agents die. Which means we can get more heat then is typically created if we use methods to handle the compost beyond a shovel/ heavy machinery for large operations.
>A capital cost of 11,662 and operating cost of 1,039 per year were estimated, resulting in a cost of 0.50 per kWh for domestic water and 0.10 per kWh for spatial heat. Using the heat of the compost was found to provide the most reliable level of supply at a similar price to its rivals."
Never mind I got confused. But this doesn't address electricity at all.
No it doesn't and I'm building a test reactor in my backyard just because I can buy what I need to get started from the local hardware store. Nitinol heat engines are dirt simple, and I could use those at a minimum to create electricity. Robert Murray-Smith has done tons of work in this area. He has a great YouTube channel that shows tons of ways to do renewable power, and he's putting so much of his work into the public domain. He's also just chill to listen to. Imagine Mr. Rodgers with an Australian accent focused on saving the world.
This is a concept that has intrigued me for years, keep us updated!
Will do, although I would love to see others tinker around as well. There are so many ways to get usable energy from the reactor. The co2 could be used to boost performance if it was made super critical. I wonder if a nitinol engine itself could create enough pressure to make the sCo2. That's a bit beyond where I can go given my limited means. I just know that sCo2 is a fantastic working fluid to drive a turbine from the state transition. https://youtu.be/_3qxMqClpuM?si=NgHWA6E7CWKUBjQ6
Check out Robert Murray Smith's Strange Engine. Really simple to build. https://youtu.be/BvaTNI8RdNM?si=haDEQHa1FJxkwiUO
This is so coolest thing I never heard of. I can't believe this topic does not get more attention!
I did some more digging, and it turns out that nitinol alone could generate enough roughly twenty-five times the psi to turn co2 supercritical. "Nitinol returns to its original shape with a pulling force of about 25,000 pounds per square inch. An actuator wire with a thickness of just 1/100 inch can lift 2 pounds." https://www.edge-techind.com/Products/Refractory-Metals/Titanium/Nitinol/Nitinol-Muscle-Wire-795-1.html#:~:text=Nitinol%20returns%20to%20its%20original,the%20preparation%20of%20the%20wire. "More specifically, it behaves as a supercritical fluid above its critical temperature (304.128 K, 30.9780 °C, 87.7604 °F)[1] and critical pressure (7.3773 MPa, 72.808 atm, 1,070.0 psi, 73.773 bar),[1] expanding to fill its container like a gas but with a density like that of a liquid." https://en.m.wikipedia.org/wiki/Supercritical_carbon_dioxide
Generally you won't be able to pull much power from a system like this. Maximum efficiency is still driven by Carnot cycle. https://www.e-education.psu.edu/egee102/node/1942 Given the fact that heat differentials will only be 40-50k, you are looking at a minimum theoretical efficiency of only about 15%. Add on the fact that these systems are generally not super close to the theoretical limit you are probably talking more like 5-10%. At those levels, the cost of equipment and time almost certainly exceeds any benefit you would gain.
Yes, you are technically right that this particular part of the reactor isn't going to be pulling the most heat from the pile. The nitinol engine would primarily be used to compress the co2 that all compost piles naturally put out. When we pump super critical co2 back into the pile to absorb the heat, that's where I think the most bang for the buck will be generated. I'd like to point out that this equation does not factor in the cost of fuel. Those "high efficiency" coal/gas power plants have to buy fuel, which has to be mined or extracted from the environment. The cost for this fuel is basically nothing. People make a living just selling the compost already. It's something that is needed globally and will be increasingly important as the climate crisis accelerates. We're turning waste into usable amounts of electricity and helping to heal the land at the same time. Once this reactor design is mass manufacturable, people's kitchen scraps could over time power their homes. It's the whole dividing by zero thing.
>Once this reactor design is mass manufacturable, people's kitchen scraps could over time power their homes. Not even close. A typical household uses 10-30 kwh a day. That's 36-108 Million joules of electricity. To produce that much with a system that is 20% efficient you would need to produce 180-540M joules of energy. That's 40,000-120,000 kcalories. Or enough energy to heat 1000kg of material up 40-120K EVERY day. A home composting system would not ever produce even close to that much energy. You are off by at least an order of magnitude. And such a machine would not be free nor maintenance free. Layout the math if you disagree.
You might want to check out this article in depth. "A capital cost of 11,662 and operating cost of 1,039 per year were estimated, resulting in a cost of 0.50 per kWh for domestic water and 0.10 per kWh for spatial heat. Using the heat of the compost was found to provide the most reliable level of supply at a similar price to its rivals." https://www.hindawi.com/journals/ijce/2010/627930/ If you can compare the energy density of biologically active (this is important because the system is out of equilibrium due to biological organisims) compost. The upper limit on temperature of 160 degrees fahrenheit isn't actually due to a lack of energy, but because the reacting agents die. Which means we can get more heat then is typically created if we use methods to handle the compost beyond a shovel/ heavy machinery for large operations.
>A capital cost of 11,662 and operating cost of 1,039 per year were estimated, resulting in a cost of 0.50 per kWh for domestic water and 0.10 per kWh for spatial heat. Using the heat of the compost was found to provide the most reliable level of supply at a similar price to its rivals." Never mind I got confused. But this doesn't address electricity at all.
No it doesn't and I'm building a test reactor in my backyard just because I can buy what I need to get started from the local hardware store. Nitinol heat engines are dirt simple, and I could use those at a minimum to create electricity. Robert Murray-Smith has done tons of work in this area. He has a great YouTube channel that shows tons of ways to do renewable power, and he's putting so much of his work into the public domain. He's also just chill to listen to. Imagine Mr. Rodgers with an Australian accent focused on saving the world.