Heat pumps in cold air

[nick pine]

This youtube video shows an air source heat pump making 95 F (555 R)
refrigerant with -12 F (448 R) outdoor air...
http://www.youtube.com/watch?v=n8q9jnkaPOk&feature=plcp

http://en.wikipedia.org/wiki/Heat_pump says the Carnot efficiency limits the
maximum achievable efficiency of a heat pump to COP = Thot/(Thot-Tcold), using
absolute temperatures, eg 555/(555-448) = 5.2 in the video.

It goes on to say:

>while current "best practice" heat pumps (ground source system, operating
between 0° and 35° Celsius) have a typical COP around 4, no better than 5, the
maximum achievable is 12 because of fundamental Carnot cycle limits. This means
that in the coming decades, the energy efficiency of top-end heat pumps could at
least double. Cranking up efficiency requires the development of a better gas
compressor, fitting HVAC machines with larger heat exchangers with slower gas
flows, and solving internal lubrication problems resulting from slower gas flow.

Better heat pumps that also AC combined with very cheap PVs and yearly net
metering for energy storage could kill solar thermal collectors.

Energy Secretary Chu's 2012 youtube predictions for PV prices are already out of
date, ie too high... http://ases.org/conference/

Nick

 

 

[CJE]

I don't know if that's true - simplicity has it's benefits. I well remember the 1970's solar system. The problem was: no one could work on them. Particularly the controls. I built several tracking control systems for parabolics because no one seemed to know anything about the existing controls. Not even the makers.

Those 'mini-split' heat pump units pictured are really nice - until they break. Then customer service is lacking as is the technical people to do the work.

Or; that has been my experience anyway. <g>

I can build heat pump systems but, as compared to the thermal solar systems I build, they are just more complicated than I care to deal with for myself. And I have a hard time picturing that a basic differential controller and a circulating pump could ever have a life-cycle cost even near to that of a low-temp heat pump.

stephen
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