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Bernd  Fighting algorithmic racism like John Henry  1yr ago (image post)   Edited 1yr ago   4193 thread views

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

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Geothermal looks so cool, I'm pretty sure I'll be in my house for at least the next 10 years so it's tempting. My back yard is full of roots though and I'm worried I couldn't dig the trench without killing my shade trees, which I love. I'd probably rent an excavator though, I've done enough digging to know I never want to do it by hand again.


				

				

						

							

								
							

						


						
					

				
			


			

	


			
			 
				
					

						
							



	

	

		
			

			

				

			

		

			


				

					
It does! I'm in a similar situation with shade trees, but seriously thought about lopping them all down and doing it anyways. It was tempting to put a big "geothermal!" mark at COP5+ on the graph, but it was already too crowded.


Had to cut almost everything about ground-source stuff for length, but I think it's the future in cold climates, and Europe is making a serious mistake trying to push air-source units rather than street-level ground source. There's a tremendous amount of wasted heat flowing down every sewer pipe without even having to do any digging, and ultra-low-temperature local cogeneration would make even a simple gas turbine about 260% efficient.


				

				

						

							

								
							

						


						
					

				
			


			

	


			
			 
				
					

						
							



	

	

		
			

			

				

			

		

			


				

					


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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