3 ms·

> Not sure about the math here, but it is surely cheaper to build a bigger tank with crappy sand than a smaller one with more expensive clay. It's also interes

> Not sure about the math here, but it is surely cheaper to build a bigger tank with crappy sand than a smaller one with more expensive clay. It's also interesting that the sand is heated with energy generated from wind turbines and solar panels, which means that as long as enough energy is being thrown into the thermal capacitor, it will heat up with little cost. From this point onward, it's an economics problem. Either money is thrown at the efficiency of these heating capacitors, which brings at most small gains, or money is thrown in building additional storage capacity for cheap along with increasing how much energy is fed into the system. Would it be more cost effective in replacing sand with more efficient materials, or spend the money in, say, another cheap thermal energy source?

zdragnar 4y ago
> Either money is thrown at the efficiency of these heating capacitors, which brings at most small gains, It really depends on whether the air in the system is a closed loop or not while they are building up the heat in the device. Sand is, at best, going to be about 1/3 as efficient as clay in an open system (hot air goes in, travels through some pipes, then comes back out as waste exhaust). This number is based on experiments with rocket mass heaters I've seen. It could actually be worse- I honestly can't remember if the 1/3 number was for sand, or the large rock (think bowling ball sized) + gravel mix, which was more efficient than sand. In this scenario, since your input energy is basically free, more storage capacity = more money, and switching to clay could triple your effective capacity. If, on the other hand, air is blown in a closed loop, you really only risk burning out your fan and resistive heating elements faster (they don't get cooled down by fresh air). In this scenario, 100% of the energy eventually transfers into the sand, so you're really only losing money if you need to spend more on land for setting up additional units.
- simplotek 4y ago
  > In this scenario, since your input energy is basically free, more storage capacity = more money, and switching to clay could triple your effective capacity. That's all fine and dandy, but the whole point is that projects are evaluated in terms of money and not joules. This means that if a material like clay is , as you claim, 3 times more efficient but ends up costing twice or more to replace and more to maintain, you are in reality looking at a prospective best-case scenario that lies somewhere significant losses or irrelevant gains. Meanwhile, building the exact same sand-based prototype right next to the original one would literally double the capacity at a far smaller cost. People want to get warm, not discuss whether clay or sand pack as much heat. Half the world could not care less about what goes into AA batteries. Projects are evaluated in financial and economical terms. It matters nothing if there's a theoretical possibility that some other material or design is more efficient, if it's savings are irrelevant. The world rides Volkswagens, not Formula 1 cars.
  - zdragnar 4y ago
    What makes you think any part of this conversation is theoretical? I'm speaking with the experiences of people who do this for a living. A few tons of clay are not doing to cost more than the benefit from an operating lifetime of triple returns.

zdragnar 4y ago

> Either money is thrown at the efficiency of these heating capacitors, which brings at most small gains, It really depends on whether the air in the system is a closed loop or not while they are building up the heat in the device. Sand is, at best, going to be about 1/3 as efficient as clay in an open system (hot air goes in, travels through some pipes, then comes back out as waste exhaust). This number is based on experiments with rocket mass heaters I've seen. It could actually be worse- I honestly can't remember if the 1/3 number was for sand, or the large rock (think bowling ball sized) + gravel mix, which was more efficient than sand. In this scenario, since your input energy is basically free, more storage capacity = more money, and switching to clay could triple your effective capacity. If, on the other hand, air is blown in a closed loop, you really only risk burning out your fan and resistive heating elements faster (they don't get cooled down by fresh air). In this scenario, 100% of the energy eventually transfers into the sand, so you're really only losing money if you need to spend more on land for setting up additional units.

simplotek 4y ago
> In this scenario, since your input energy is basically free, more storage capacity = more money, and switching to clay could triple your effective capacity. That's all fine and dandy, but the whole point is that projects are evaluated in terms of money and not joules. This means that if a material like clay is , as you claim, 3 times more efficient but ends up costing twice or more to replace and more to maintain, you are in reality looking at a prospective best-case scenario that lies somewhere significant losses or irrelevant gains. Meanwhile, building the exact same sand-based prototype right next to the original one would literally double the capacity at a far smaller cost. People want to get warm, not discuss whether clay or sand pack as much heat. Half the world could not care less about what goes into AA batteries. Projects are evaluated in financial and economical terms. It matters nothing if there's a theoretical possibility that some other material or design is more efficient, if it's savings are irrelevant. The world rides Volkswagens, not Formula 1 cars.
- zdragnar 4y ago
  What makes you think any part of this conversation is theoretical? I'm speaking with the experiences of people who do this for a living. A few tons of clay are not doing to cost more than the benefit from an operating lifetime of triple returns.