3 ms·

On the other hand, if I'm trying to keep a volume cold for as long as possible, how can I do that without "crazy amounts of insulation"? I can use a Stirling e

On the other hand, if I'm trying to keep a volume cold for as long as possible, how can I do that without "crazy amounts of insulation"? I can use a Stirling engine driven by the solar gain to run a heat pump to push the temperature gradient, but I still need a large-ass amount of insulation to beat the radiating heat creeping into the cold volume. Lots of HVAC discussions revolve around keeping people comfortable and happy, but I'm trying to figure out how to keep a cold space at that set point regardless of what goes on outside it. And if your definition of "crazy amounts" includes cost, then aerogel-core vacuum insulated panels are right out (though in terms of volume occupied, they're nifty, but only a 50 year lifecycle unfortunately).

Retric 6y ago
The cost effectiveness of insulation is a function of the cost of solar power which has been dropping. The most efficient ratio 10 years ago is now outdated. Further, heat transfer is only half the story. A delta of 100f vs 72f is the same as 44f vs 72f which is not that cold. What makes AC consume so much energy is dehumidifying the air, and that varies wildly. That and everything heating the space like people and electronics is helpful in the cold and counterproductive in the heat. Clearly there is always some value in more insulation, it’s simply less important than generally assumed.
- yourapostasy 6y ago
  Aha, I see where we are coming at this from different angles. Thanks for your feedback. I'm looking for designs that incorporate passive elements that last ideally 100+ years that are reusable in modular sections, amortizing cost-effectiveness over generations. For that criteria, below-frost-line earth-covered, foamed glass building envelopes meets my requirements, and I'm happy to set aside 6-12 feet of foamed glass insulation after digging down enough to get below the frost line to achieve the thermal control I'm seeking. I'm looking for dehumidification to consistently 5-8%, with temperature in deep freeze range (-30 to -50°C). I've so far been stumped finding someone who has already, or figuring out myself how to passively (or with about the energy consumption of a Pi Zero per day) capture and use elsewhere the heat hitting panels to manage their thermal cycling. Nor have I been able to find a self-cleaning (superhydrophobic and/or appropriate wettability) coating that can be lifecycle rated to the timeframe I'm seeking. I think if we can control those, then solar panel lifetimes can be extended to 100 years at 20% degradation ("80% 'efficiency'"). Unfortunately, I've been stymied trying to find the lifespan of gallium-arsenide solar panels. Probably because their three-order of magnitude cost differential limiting them mostly to outer space applications where the weight-to-efficiency savings are the primary design motivator, and no one particularly cares about lifespan as long as it outlasts the design life of the satellite, which is way less than the 100+ years I'm seeking. Solar panels already have a pretty decent LifeCycle Assessment compared to coal and natural gas, though their de-manufacturing/re-manufacturing tech is still at a nascent stage. I simply have a different goal than most people with my requirements for long duration lifespans.

Retric 6y ago

The cost effectiveness of insulation is a function of the cost of solar power which has been dropping. The most efficient ratio 10 years ago is now outdated. Further, heat transfer is only half the story. A delta of 100f vs 72f is the same as 44f vs 72f which is not that cold. What makes AC consume so much energy is dehumidifying the air, and that varies wildly. That and everything heating the space like people and electronics is helpful in the cold and counterproductive in the heat. Clearly there is always some value in more insulation, it’s simply less important than generally assumed.

yourapostasy 6y ago
Aha, I see where we are coming at this from different angles. Thanks for your feedback. I'm looking for designs that incorporate passive elements that last ideally 100+ years that are reusable in modular sections, amortizing cost-effectiveness over generations. For that criteria, below-frost-line earth-covered, foamed glass building envelopes meets my requirements, and I'm happy to set aside 6-12 feet of foamed glass insulation after digging down enough to get below the frost line to achieve the thermal control I'm seeking. I'm looking for dehumidification to consistently 5-8%, with temperature in deep freeze range (-30 to -50°C). I've so far been stumped finding someone who has already, or figuring out myself how to passively (or with about the energy consumption of a Pi Zero per day) capture and use elsewhere the heat hitting panels to manage their thermal cycling. Nor have I been able to find a self-cleaning (superhydrophobic and/or appropriate wettability) coating that can be lifecycle rated to the timeframe I'm seeking. I think if we can control those, then solar panel lifetimes can be extended to 100 years at 20% degradation ("80% 'efficiency'"). Unfortunately, I've been stymied trying to find the lifespan of gallium-arsenide solar panels. Probably because their three-order of magnitude cost differential limiting them mostly to outer space applications where the weight-to-efficiency savings are the primary design motivator, and no one particularly cares about lifespan as long as it outlasts the design life of the satellite, which is way less than the 100+ years I'm seeking. Solar panels already have a pretty decent LifeCycle Assessment compared to coal and natural gas, though their de-manufacturing/re-manufacturing tech is still at a nascent stage. I simply have a different goal than most people with my requirements for long duration lifespans.