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Hot water cylinders can have heatpumps too! Wish we found a solid way yo harvest heat from waste water. So much energy is wasted on showers - similar to EV dri

Hot water cylinders can have heatpumps too! Wish we found a solid way yo harvest heat from waste water. So much energy is wasted on showers - similar to EV driving at highway speeds.

throwaway4220 4y ago
https://en.m.wikipedia.org/wiki/Countercurrent_exchange https://en.m.wikipedia.org/wiki/Countercurrent_exchange A lot of mammals do this including humans. Don’t know if there’s a drop in plumbing shower solution.
bombcar 4y ago
We do it. It’s not yet economically worth it but I’ve seen installs. I can’t find it but I saw one that was designed to let a massive shower run continuously with very little heat loss - the water coming out the end of the drain was as cold as the inlet water from the main. https://en.m.wikipedia.org/wiki/Water_heat_recycling https://en.m.wikipedia.org/wiki/Water_heat_recycling
theluketaylor 4y ago
drain water heat recovery is already a thing. It's code for new builds in British Columbia, Canada. It's only expensive due to the amount of copper. The actual install has no moving parts and is completely passive. https://www.nrcan.gc.ca/energy/products/categories/water-heaters/14568 https://www.nrcan.gc.ca/energy/products/categories/water-hea...
- dzhiurgis 4y ago
  What efficiency are these? Brainstormed this a bit and feels like shower cabins (pretty popular over NE Europe) should have such system as standalone... As in - it collects waste, collects heat and stores it for next shower. Dunno how much energy a typical refrigerant can store tho. Also great fit for Japanese-style smart baths (press a button and water of desired temperature fills and stays warm), tho they seem rare outside Japan.
  - theluketaylor 4y ago
    I think they can recover up to 60-70% of the heat in the drain water. Not bad for totally passive. The installs I have seen are on the main drain for the whole house and located right next to the hot water heater. For it to really work you need a hot water tank, but I have seen some small tanks combined with tankless.
  - shellfishgene 4y ago
    There are systems that replace the shower drain with something like a heat exchanger, the water is warmed with the drain water right away, no need to store the heat. For example https://www.oeko-energie.de/shop1/de/eco-shower-duschrinne.html https://www.oeko-energie.de/shop1/de/eco-shower-duschrinne.h... (in German, but the image is simple to understand.)
xani_ 4y ago
If you already have water-water heat pump I'd imagine it would be a heat exchanger away from recovering at least some

Hot water cylinders can have heatpumps too! Wish we found a solid way yo harvest heat from waste water. So much energy is wasted on showers - similar to EV driving at highway speeds.

throwaway4220 4y ago

https://en.m.wikipedia.org/wiki/Countercurrent_exchange https://en.m.wikipedia.org/wiki/Countercurrent_exchange A lot of mammals do this including humans. Don’t know if there’s a drop in plumbing shower solution.

bombcar 4y ago

We do it. It’s not yet economically worth it but I’ve seen installs. I can’t find it but I saw one that was designed to let a massive shower run continuously with very little heat loss - the water coming out the end of the drain was as cold as the inlet water from the main. https://en.m.wikipedia.org/wiki/Water_heat_recycling https://en.m.wikipedia.org/wiki/Water_heat_recycling

theluketaylor 4y ago

drain water heat recovery is already a thing. It's code for new builds in British Columbia, Canada. It's only expensive due to the amount of copper. The actual install has no moving parts and is completely passive. https://www.nrcan.gc.ca/energy/products/categories/water-heaters/14568 https://www.nrcan.gc.ca/energy/products/categories/water-hea...

dzhiurgis 4y ago
What efficiency are these? Brainstormed this a bit and feels like shower cabins (pretty popular over NE Europe) should have such system as standalone... As in - it collects waste, collects heat and stores it for next shower. Dunno how much energy a typical refrigerant can store tho. Also great fit for Japanese-style smart baths (press a button and water of desired temperature fills and stays warm), tho they seem rare outside Japan.
- theluketaylor 4y ago
  I think they can recover up to 60-70% of the heat in the drain water. Not bad for totally passive. The installs I have seen are on the main drain for the whole house and located right next to the hot water heater. For it to really work you need a hot water tank, but I have seen some small tanks combined with tankless.
- shellfishgene 4y ago
  There are systems that replace the shower drain with something like a heat exchanger, the water is warmed with the drain water right away, no need to store the heat. For example https://www.oeko-energie.de/shop1/de/eco-shower-duschrinne.html https://www.oeko-energie.de/shop1/de/eco-shower-duschrinne.h... (in German, but the image is simple to understand.)

xani_ 4y ago

If you already have water-water heat pump I'd imagine it would be a heat exchanger away from recovering at least some