PHOTOSYNTHESIS AND THE POSSIBLE USE OF SOLAR

ENERGY.1

By H. A. SPOEHR,

Carnegie Institution of Washington, Coastal Laboratory, Carmel, Calif.

The purpose of the following brief outline is to show that while the photosynthetic process of the plant is at present the only means we have of utilizing solar energy, this method is so very inefficient and subject to such great uncertainties that it is exceedingly doubtful whether it can be depended upon to maintain our energy requirements. In other words, our civilization is using energy at a prodigious rate, and we would be depending upon the exceedingly inefficient and slow process of photosynthesis to supplant the supplies which have been stored for centuries and are now being depleted. Add to this, that in order to supply food for our increasing population no encroachment on agricultural industry would be permissible. Theoretical speculations of the nature of what might be accomplished if, for instance, all the arable land were cultivated, are of no consequence to the problem. Conditions, economic and social, must be faced as they exist. The inertia of our civilization is such that great changes are induced only by the labored movements of evolution or by catastrophe. What part, then, can science and engineering play in the solution of this problem?

First of all, it is the function of scientists to exercise foresight in matters regarding the material welfare of humanity. The experiences of the various scientific bodies called together to cope with the many problems incident to the war, concur in the conclusion that very rarely is necessity the parent of invention where difficult and highly complex problems are concerned. So for this work there will be required an enormous amount of patient labor, which naturally should be begun long before the situation becomes acute.

It has frequently been said of our earth that there are no exports and no imports aside from occasional meteorites. This is true as far as matter is concerned, but it is not true when energy is considered. Matter and energy are the two fundamental entities in our conceptions of all physical phenomena. As scientific thought progresses, ever-increasing attention is being given to the paramount importance of energy relations in the interpretation of natural phenomena. Matter is of interest to us largely in so far as it exhibits certain properties and undergoes definite changes. In viewing the common materials upon which we depend for the maintenance and propagation of life, it is evident that we are less interested in the matter as such than its ability to undergo certain changes which contribute

Reprinted by permission from the Journal of Industrial and Engineering Chemistry, vol. 14, no. 12, December, 1922.