4 ms·

That equation is definitely changing with modern PV prices and heat pumps: https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead http

That equation is definitely changing with modern PV prices and heat pumps: https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead https://www.greenbuildingadvisor.com/article/solar-thermal-i...

jonstewart 7y ago
Yes. Successful passive solar homes typically aren't all that passive, as they often need fans to transfer heat between the solar space and the storage medium (e.g., Hodges's house had pipes in the cement floor with fans; it was also common in other passive solar houses to have a massive rock bed beneath the foundation with air ducted through it). The traditional passive solar house where a mass floor is heated really only works in climates where it's sunny on a regular basis in winter (basically, the Plains, Rockies, and Southwest). If it can get cloudy, the house will need far more thermal storage and a means of heat transfer and control. The capital cost of the storage and system is considerable, and then operation requires maintenance. Also, the glazing typically needs to be covered overnight to keep from radiating all the heat out. It's not very passive. (I own a so-called passive solar home which is woefully lacking in storage; on a sunny day it'll heat up to 78F inside, but it will lose all the heat out the windows overnight). Contrast with the one-two punch that is heat pumps and solar panels, each benefiting from mass manufacturing economies of scale. The heat pump can pull in 3KW of heat for every 1KW of electricity applied, and the solar panel can provide the electricity. The total cost is probably less than $20K, works just about anywhere, and provides air conditioning in the summer.
- learn_more 7y ago
  But there's something special about having a low-tech solution which isn't as likely to break, and doesn't require a genius to troubleshoot. As an engineer myself, I prefer a calmer, low-tech approach when possible.
  - jonstewart 7y ago
    Solar tempering is great! But the point is to get to 100% heating from "passive" solar, you'll need a lot of expensive storage and an active means of controlling heat transfer to/from the storage. It's cheaper to use heat pumps, and, when coupled with solar panels, it lets you get to net-zero, and in existing houses that weren't designed for passive solar.

jonstewart 7y ago

Yes. Successful passive solar homes typically aren't all that passive, as they often need fans to transfer heat between the solar space and the storage medium (e.g., Hodges's house had pipes in the cement floor with fans; it was also common in other passive solar houses to have a massive rock bed beneath the foundation with air ducted through it). The traditional passive solar house where a mass floor is heated really only works in climates where it's sunny on a regular basis in winter (basically, the Plains, Rockies, and Southwest). If it can get cloudy, the house will need far more thermal storage and a means of heat transfer and control. The capital cost of the storage and system is considerable, and then operation requires maintenance. Also, the glazing typically needs to be covered overnight to keep from radiating all the heat out. It's not very passive. (I own a so-called passive solar home which is woefully lacking in storage; on a sunny day it'll heat up to 78F inside, but it will lose all the heat out the windows overnight). Contrast with the one-two punch that is heat pumps and solar panels, each benefiting from mass manufacturing economies of scale. The heat pump can pull in 3KW of heat for every 1KW of electricity applied, and the solar panel can provide the electricity. The total cost is probably less than $20K, works just about anywhere, and provides air conditioning in the summer.

learn_more 7y ago
But there's something special about having a low-tech solution which isn't as likely to break, and doesn't require a genius to troubleshoot. As an engineer myself, I prefer a calmer, low-tech approach when possible.
- jonstewart 7y ago
  Solar tempering is great! But the point is to get to 100% heating from "passive" solar, you'll need a lot of expensive storage and an active means of controlling heat transfer to/from the storage. It's cheaper to use heat pumps, and, when coupled with solar panels, it lets you get to net-zero, and in existing houses that weren't designed for passive solar.