Apropos of nothing in particular, I ended up watching an interesting short on YouTube last night, fronted by
Kryten Robert Llewellyn, about a company in Glasgow who are using large-scale heat pumps to provide heating for a town in Norway; they've also got big ideas about using heat pumps to provide community heating AND cooling for data centres and the like. They didn't mention the heat pump technology they were using, but they did mention it was a pretty old, so I'm guessing it's Stirling cycle...
So, anyway, this got me thinking: The oft-quoted efficiency of a stirling cycle heater/cooler is 3kW of heat for 1kW of electricity (using an electric motor, obviously), AND 3kW of cooling too, if you can use both. Well, I have a 6HP diesel engine sitting around looking for an excuse to be used, so in theory I could get 18HP of heating and/or 18HP of cooling; plus I can use engine/exhaust heat recovery to warm a tankful of water, for example, for hand washing... Yes, it'll cost money to run (in diesel), but it'd make a cool project, and the engine can always be replaced by an electric motor...
So, now I need to sit down and:
a) Work out how big a stirling cycle system needs to be to utilise a sensible fraction of a 6HP engine
b) Which type of engine arrangment to use (I'm thinking Alpha)
c) What ancilleries are needed (e.g. blowers, trunking, valves, etc)
d) Engine cooling arrangements (I've already got that covered I think)
I'd also like to run the heat pump with compressed air, to further increase the heat extraction potential. So it needs to be pretty robustly constructed. I'm also expecting it to be quite large...
Ideally I'd like the hot end to be at one end of the engine, and the cold end at the other (not separated by 90 degrees as shown in most pictures) or failing that parallel to each other. This is to simplify the airflow and valving. Finally.... should I extract heat/cold to/from fluid, or the air? Air is obviously simpler, but fluid has much more heat capacity. If I use fluids, then in theory I can simply stick a bunch of radiators in the office & either heat or cool them according to whether I want it hotter or colder, but I don't know how well a super-cold radiator would work as an alternative to a/c cooling.
Any thoughts welcomed
