THE SUN’S ENERGY—DANIELS 243 
distilled fresh water. In tackling the economic problems of solar 
energy, let us not be tied to the economic patterns and practices of 
the highly industrialized countries. There may be places where 
people would be glad to pay not 5 mils per kilowatt-hour for elec- 
tricity, but 5 cents, because the whole economy and standard of 
living would be raised. 
We must not become too enthusiastic, however. There are many 
places in the world with long, dark Arctic winters, or with cloud- 
shrouded climates where the sun cannot help. It is well to remember, 
though, that in a given area the heritage of sunlight is the same on all 
the land. The same amount of solar energy falls on an acre of land, 
whether it is city real estate costing thousands of dollars, rich farm 
land costing hundreds of dollars, grazing lands costing tens of dollars, 
or wasteland costing almost nothing. 
In looking around for large areas of unused land to be occupied with 
solar collectors, we might consider the rights-of-way at the sides of our 
railroads and highways—perhaps a “roof” equivalent for every 10 or 
20 feet. 
Solar energy is primarily for the countryside and not for the cities. 
When people are piled deep in multiple family apartments and there 
is no vacant land, demands for power per square meter of sunlight 
cannot possibly be met. No wonder a report on solar energy by a 
committee of scientists in London was rather pessimistic. 
Arizona is indeed a favored place with optimum sunshine through- 
out the year and plenty of great open spaces. It should be an excellent 
proving ground for industrial solar energy. The Bell solar battery 
has shown that we may expect rapid progress through fundamental 
research, perhaps in apparently unrelated fields. Let’s all join in the 
fun of pushing back the frontiers of solar-energy research and 
engineering. 
DEVICES AND DIFFICULTIES 
I would like to give you an introduction to some of the opportunities 
that may lie ahead, and some of the devices and difficulties with which 
we are all concerned. I hope that many new ideas for the utilization 
of solar energy will be brought forth which will lead to a chain reaction 
of additional ideas all over the world. I trust, too, that there are 
many experts who will evaluate these approaches to solar-energy uti- 
lization technically and economically and criticize them relentlessly. 
There are plenty of fertile fields for solar exploration to be worked, 
and the few active workers should not ordinarily waste their efforts 
in unpromising areas. Early criticism may serve to direct our limited 
research resources into more useful channels. 
Let me divide the future development of solar energy into short 
range and long range. About half the solar energy is light and half 
