Harry Conover wrote:

The Coefficient Of Performance is the ratio of heat energy moved to
electrical energy used, using the same energy units, eg watts. It's
about 3 for a typical AC, vs 10,000 for a good solar heating system :-)

What is the value for a good solar A/C system? :-)

For years, the goal has been to get above 1 :-) But that's less important,
since the energy is free.

Nick

"Unglazed collector/regenerator performance for a solar assisted open cycle
absorption cooling system" by M. N. A. Hawlader, K. S. Novak, and B. D. Wood
of the Center for Energy System Research, College of Engineering and Applied
Sciences, Arizona State University, Tempe, AZ 85287-5806 USA, in Solar Energy,
Vol. 50, pp 59-73, 1993: "An ordinary black shingled roof [was] used as a
collector/regenerator for the evaporation of water to obtain a strong solution
of [lithium chloride] absorbent... Experimental results [with a 36'x36' roof]
show a regeneration efficiency varying between 38 and 67%. The corresponding
cooling capacities ranged from 31 to 72 kW (8.8 to 20 tons)", ie about 1 ton
per 100 square feet of roof area, ie 1 ton per square :-)

In the house "water [the refrigerant] is sprayed into an evaporator, evacuated
to about 5 mmHg of pressure, where it immediately flashes into vapor... Cold
water, pumped from the bottom of the evaporator, flows through a fan coil...
that blows cool air into the conditioned space. The absorber acts as a vapor
compressor and condenser for the system. Water vapor from the evaporator flows
over the absorber where it is absorbed by the concentrated absorbent. The
continuous absorption of water vapor maintains a low pressure in the system
and permits flashing of water in the evaporator... The product of the
absorption process, a weak absorbent solution, collects at the bottom of
the absorber to be pumped [up over the roof] for concentration."

"The dilute LiCl solution was delivered to the collector surface through
a spray header spanning the top of the roof and made from 50.8 mm (2 in)
diameter CPVC pipe fitted with 35 evenly spaced brass nozzles. The
concentrated solution collected at the bottom... in a PVC rain gutter, and
returned via gravity feed to a 1608 l (425 gallon) fiberglass tank... In
the event of of a rain, fluid flowing off the collector could be manually
diverted to a 946 l (250 gallon) wash tank or to a roof drain. During the
initial phase of the rain, residual salt would be washed from the roof
and collected in the wash tank to be stored for later regeneration. After
sufficient rainfall, the rainwater is diverted to the roof drain."