Use waste heat to drive air-conditioning
Use waste heat to drive air-conditioning
(OP)
It's been a while ! since I did thermodynamics but I think it would be possible to use waste heat to drive a domestic air-conditioner.
The scenario is that we are thinking of buying a house in Portugal which has no electricity. I have discovered that it is possible to buy a generator based on a Stirling cycle engine. Unfortunately, this produces more heat than electricity, which is about the last thing you need in Portugal.
Hope someone can help a refugee from tek-tips.
The scenario is that we are thinking of buying a house in Portugal which has no electricity. I have discovered that it is possible to buy a generator based on a Stirling cycle engine. Unfortunately, this produces more heat than electricity, which is about the last thing you need in Portugal.
Hope someone can help a refugee from tek-tips.





RE: Use waste heat to drive air-conditioning
Waste heat could used for an absorption air conditioner. I know of several institutions that use aborption air conditioning systems and the heat needed is generated from power boilers At one time, certain brands of refrigerators were actually absorption system and the fuel needed to generate heat was natural gas piped into the refrigerator. These refrigerators can still be found but are becoming rare. This type of refrigerator lasted for decades with virtually no maintemance.
Waste heat could also be used with heat pumps as home heating systems. Heat pumps use the same refrigeration cycle and will use the heat of compression to heat structures. It is an efficient heating system but can be expensive when repairs are needed to the compressor.
RE: Use waste heat to drive air-conditioning
I had forgotten about gas fridges. I shall investigate.
Thanks.
RE: Use waste heat to drive air-conditioning
Sometime back there was thread asking the explanation for a solar refrigerator. (It was patented by a South African student, but I couldn't get the link which explains the theory fully) Check that and it may help you.
RE: Use waste heat to drive air-conditioning
The Capstone unit starts at about $40K USD ( 35 KWe)plus cost of gas compressor plus absorption unit, if I remember right.
RE: Use waste heat to drive air-conditioning
I found this huge list http://archive.greenpeace.org/gopher/campaigns/air/1993/ozhold3.txt
This is US based only and I haven't actually read it all as yet.
A small amount of electricity is fairly easy to produce. The problem is you get too much heat with it which is wasteful. As far as I can see, fuel cells are better but I think a little expensive yet.
RE: Use waste heat to drive air-conditioning
Yeah pretty expensive stuff for residential application!!
RE: Use waste heat to drive air-conditioning
if you think that the capstone microturbine mentioned by davefitz is too expensive for domestic use, better stop investigating in stirling cycle systems unless you are able to tinker your own machine. Stirling engines make sense when your fuel is really cheap like wood, other biomass or waste heat from existing combustion processes.Also the cost for an absorption chiller for your residence (unless you bought a palace), compared in Euro per m2 floor space will drive tears in your eyes. I would install a photovoltaic system for electricity and leave the windows open for airconditioning, its not that hot in Portugal.
RE: Use waste heat to drive air-conditioning
A larger scale up of this was used recently to chill the inlet air of a large Utility frame Gas turbine installed in Arizona, USA
RE: Use waste heat to drive air-conditioning
Solar looks good too. But I would like to use waste heat and we do need reliable electricity. I think we are a bit cutting edge here.
I don't know where you live Setra, but from a UK perspective, I can assure you that Portugal is hot.
RE: Use waste heat to drive air-conditioning
It's a dry heat.
RE: Use waste heat to drive air-conditioning
you did not mention what source your waste heat is coming from. The stirling works on external combustion processes. Unless there is any industrial or commercial activity around producing waste heat you have to burn some kind of fuel to drive your stirling engine.
RE: Use waste heat to drive air-conditioning
RE: Use waste heat to drive air-conditioning
For your generator unit with around 5 kW electrical capacity we talk about Euro 15.00,- to 20.000,- investment.
These units are available, but without long term experience about service life.
The adsorbtion chiller in this capacity range will cost you another Euro 10.000,- plus the cost of Gas supply.
The overall efficiency will be very poor because you can never consume the full capacity of your generator and your chiller at the same time over the day.
I make my living with consultancy in renewable energy, and I appreciate your enthusiasm, but you should really focus on solar power for your electricity needs.
RE: Use waste heat to drive air-conditioning
How can we store solar generated electricity? For when the sun goes down.