246 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
space heating it is clear that there are important conservation as- 
pects to solar house heating. In northern climates the capital cost 
of large heat-storage capacities is so great that it seems wise to 
use small auxiliary plants operating on conventionel fuel in addition 
to the solar heating plant. 
In those areas where fuel is expensive and wood and shrubbery 
need to be conserved in order to minimize soil erosion, there is a 
special need for solar house heating. In areas of greatest need there 
is likely to be both a scarcity of fuel and an absence of electricity 
What then is to be used in the solar heating plant for circulating 
air or water through the heat storage bins? Circulation by natural 
convection is usually not enough. Efforts should be made to de- 
velop an inexpensive, solar-operated device for circulating air or 
water. 
When ample electricity is available the use of a heat pump offers 
attractive possibilities with a reservoir of heat produced by solar 
radiation. 
REFRIGERATION AND HOUSE COOLING 
Household refrigeration is one of the most urgent fields for the 
utilization of solar energy. Nutritional deficiencies among people 
living in tropical areas could be reduced by providing cheap re- 
frigerators for preserving proteins and other foods. The potential 
market all over the world for refrigerators and house cooling is tre- 
mendous. 
In the United States with its abundant supply of electricity, re- 
frigeration developments have followed mechanical refrigeration 
with moving parts powered by electric motors. The absorption and 
desorption of ammonia in water and other similar types of refrig- 
eration are probably simpler and more efficient. Intensive research 
on small solar-operated cooling systems should include not only 
absorption and desorption of gases in solutions, but also adsorp- 
tion and desorption of gases on solid surfaces and dehydration sys- 
tems in which the dissolved water is driven out of a solution with 
solar heat and the dry high-boiling liquid is then ready to absorb 
more water vapor. 
DISTILLATION OF SEA WATER 
A million calories per minute or 500,000 kilocalories per day of 
solar energy striking an area of 100 square meters could theoreti- 
cally support enough heat to vaporize about a milion grams of water, 
which is a layer of water 1 centimeter or 0.4 inch deep. Practically, 
of course, the efliciency would be low and solar distillation would 
normally correspond to less than 0.2 inch cf rain. Multiple stills 
are possible in which some of the heat of condensation of the water 
