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Bernd  Fighting algorithmic racism like John Henry  1yr ago (image post)   Edited 1yr ago   4902 thread views

Mini Split Heat Pumps: Not Significantly More Than You Reasonably Need To Know

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There's a tremendous amount of wasted heat flowing down every sewer pipe without even having to do any digging




I've thought about this before, and what I came up with was water-water heat exchangers in shower drains, between the outflow and the cold inflow.  You'd want a thermostat-controlled valve to keep the shower temperature from drifting, but that'd be an improvement to UX even without the HX. Dishwashers could do the same thing to recycle heat from prewash->wash->rinse. (IDK if warm rinse would be more effective, but it'd use less energy to dry.)


Putting the recovery device as close as possible to the producer of warm graywater gets you the highest-grade heat, and also means your HX doesn't have to tolerate actual poo. In the individual house/apartment, drain heat is intermittent and unreliable, but conveniently correlated with the need for hot water.  Building-level heat capture could smooth out the availability with a big buffer tank, but hot sewer water is diluted with cold.


In large apartment buildings, the owner could install a cold water pre-heater (to say, 20°C or so), using the most economical type of heat for the climate, which would reduce cooking energy (and time) in winter.  People might naturally use less hot water for washing hands too.  A couple of years ago, I measured the flow rate and hot-cold temperature delta of my kitchen faucet in winter, and now whenever I run the hot water waiting for it to warm up, running through the back of my mind is, "YIKES 13 kW!"


				

				

						

							

								
							

						


						
					

				
			


			

	


			
			 
				
					

						
					

				
			
		

	




	

	

	

	

	

	
	

	
	

	
 















	






			
			

		

		
			
				


	

		
	


	


		
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