4 ms·

IMO, geothermal doesn't really make sense. It's expensive, and the heat gradient isn't huge- you have to drill or dig huge trenches to make up for it. Solar w

IMO, geothermal doesn't really make sense. It's expensive, and the heat gradient isn't huge- you have to drill or dig huge trenches to make up for it. Solar water heating is extremely efficient (and less complicated), but I have never seen it in the US. As for cooling, if it's hot out, the sun is probably out- solar PV with AC/heat pump should be fine.

olivierlacan 5y ago
I've seen solar water heaters routinely on roofs in Florida and other U.S. states that get sufficient heat (Arizona, etc.). I'm not sure either of our observations are useful to determine how prevalent rooftop solar water heating is.
- lostapathy 5y ago
  Solar water heaters have really fallen out of favor because to make them robust, they are more complicated than you'd think. It's generally not viable to just run a water pipe onto the roof, due to both freezing and temperature regulation concerns. So you end up with a closed loop system (filled with a glycol solution that won't freeze) and a heat exchanger to get the water into your domestic supply and at a consistent temperature. Not to mention the service issues of having something "weird" on your house as a critical system. Nowadays, we have electric heat pump water heaters that are very efficient, so running that in conjunction with solar panels to generate electricity can make a lot more sense in practice.
  - msandford 5y ago
    I wish it was easy to buy a gas hot water heater that also had a few coils of copper in it so I could plumb in whatever kind of energy harvesting heat source I could come up with. It'd be great to tap into the heat my AC throws off, or a closed loop solar thermal panel, or both!
    - lostapathy 5y ago
      It really is a shame that HVAC contractors want to mark up more efficient or "exotic" options so much higher than the "base" option. I had my AC replaced a few years back for like $3500, with "least efficient we can legally sell". Doing anything else was going to double the price, even though the wholesale cost difference to the next step up was under 20% of that.
      - msandford 5y ago
        Yeah that's awful. "Value pricing" I suppose. I wouldn't mind it if there was an easy-enough way to DIY so as to "route around the problem" but with the licensing requirements you can't really.
        lostapathy 5y ago
        To a degree - I get contractor reluctance. Most people don't care to spend more to do better, so they're never going to have much of an install base to build knowledge from. So they're probably estimating high because of unknowns, and also partly because bidding on higher-end packages just isn't as competitive. I'd really just like to order my own equipment and pay an HVAC company's "day rate" to come out and install it, and I'll deal with surprises or warranty issues.
kragen 5y ago
Your comment is entirely unrelated to the article, which is about using the very hot rock several kilometers underground to drive turbines to generate electricity.
Johnny555 5y ago
Solar water heating is quite popular in the state of Hawaii -- energy is very expensive there since fuel is brought in by boat and of course there's a lot of sun, so it's very cost effective.

olivierlacan 5y ago

I've seen solar water heaters routinely on roofs in Florida and other U.S. states that get sufficient heat (Arizona, etc.). I'm not sure either of our observations are useful to determine how prevalent rooftop solar water heating is.

lostapathy 5y ago
Solar water heaters have really fallen out of favor because to make them robust, they are more complicated than you'd think. It's generally not viable to just run a water pipe onto the roof, due to both freezing and temperature regulation concerns. So you end up with a closed loop system (filled with a glycol solution that won't freeze) and a heat exchanger to get the water into your domestic supply and at a consistent temperature. Not to mention the service issues of having something "weird" on your house as a critical system. Nowadays, we have electric heat pump water heaters that are very efficient, so running that in conjunction with solar panels to generate electricity can make a lot more sense in practice.
- msandford 5y ago
  I wish it was easy to buy a gas hot water heater that also had a few coils of copper in it so I could plumb in whatever kind of energy harvesting heat source I could come up with. It'd be great to tap into the heat my AC throws off, or a closed loop solar thermal panel, or both!
  - lostapathy 5y ago
    It really is a shame that HVAC contractors want to mark up more efficient or "exotic" options so much higher than the "base" option. I had my AC replaced a few years back for like $3500, with "least efficient we can legally sell". Doing anything else was going to double the price, even though the wholesale cost difference to the next step up was under 20% of that.
    - msandford 5y ago
      Yeah that's awful. "Value pricing" I suppose. I wouldn't mind it if there was an easy-enough way to DIY so as to "route around the problem" but with the licensing requirements you can't really.
      - lostapathy 5y ago
        To a degree - I get contractor reluctance. Most people don't care to spend more to do better, so they're never going to have much of an install base to build knowledge from. So they're probably estimating high because of unknowns, and also partly because bidding on higher-end packages just isn't as competitive. I'd really just like to order my own equipment and pay an HVAC company's "day rate" to come out and install it, and I'll deal with surprises or warranty issues.

kragen 5y ago

Your comment is entirely unrelated to the article, which is about using the very hot rock several kilometers underground to drive turbines to generate electricity.

Johnny555 5y ago

Solar water heating is quite popular in the state of Hawaii -- energy is very expensive there since fuel is brought in by boat and of course there's a lot of sun, so it's very cost effective.