As the civilization of to-day is absolutely dependent on the energy stored up in the coal beds many thousands of years ago it is of interest to determine whether our descendants will possess any adequate substitute for this source of energy, when it shall have been exhausted. The quantities of coal mined in various countries in 1909, expressed in millions of tons, were as follows : United States, 402.0 ; Great Britain, 268.0 ; Germany, 217.4 ; all other countries, 209.9. The total amount for the whole world, therefore, is 1,097.3 million tons which, assuming the heat of combustion to be 6,000 calories per kilogramme, would produce, in burning, 6.6 X 10” calories. The quantities of mineral oil produced in 1909, also expressed in millions of tons, were : United States, 23.0 ; Russia, 8.6 ; Austria-Hungary, 1.7 ; Rumania, 1.1 ; all other countries, 2.8. The total is 37.2 million tons, which, assuming the heat of combustion to be 10,000 calories per kilogramme, would produce, in burning, 3.7 X 10” calories. The total amount of energy obtained from fossil fuel in 1909, therefore, was about 7 X 10” calories. For some purposes it is preferable to evaluate our consumption of fuel in mechanical, rather than British thermal units. A modern steam engine consumes, for each horse-power developed, 500 grammes of coal per hour, or 4.3 tons per year. The corresponding quantities for a motor using liquid fuel, in the most favorable conditions, are 200 grammes and 1.7 tons. Hence the coal and oil mined in 1909 would suffice for the production of about 270 million horse-power continuously throughout the year. The substitute for mineral fuel that first suggests itself is “white coal,” or water power, which already is utilized very extensively, with the aid of the most improved technical appliances. An accurate valuation of the aggregate available water power of the globe cannot yet be made, but it is possible to form an approximate estimate and to assign a superior limit with certainty. More or less thorough surveys of water power have been made in many lands, including Switzerland, Norway, Sweden, France, Italy, the United States and Canada. The most complete data accessible are those of Switzerland, where the total water power worth developing, including that which is already utilized, is estimated at 1.25 million horse-power. This water power is distributed through the valleys of the Rhine, the Rhone, and other rivers, which at mean height carry 1,475 cubic meters of water per second over the Swiss frontier. The average level of this water is 1,130 meters higher on entering than on leaving Swiss territory. A cubic meter of water weighs 1,000 kilogrammes, and a horse-power is 75 meter-kilogrammes per second. Hence this flood of water is theoretically 1,475,000 X 1,130 equivalent to--= 22 million horse- 75 power. We will call this the “meteorological” water power, in distinction to the “technical” or practically available water power. In Switzerland the latter is 1.25 million horse-power, or about 5.5 per cent of the power. The ratio is larger in some countries (Norway and Sweden) and smaller in others (Canada), but the Swiss ratio fairly represents the general average, and applies particularly to tropical lands with definite rainy seasons and to the vast mountain region of the Andes. We shall certainly not underestimate the available water power of the globe if we assume the Swiss ratio to apply everywhere. The volume of water poured into the ocean by the rivers of the whole world is esti- • Prof. Georg von dem Borne, in Deutsche Technifc. mated at 31,000 cubic kilometers per year, or one million cubic meters per second, and the mean height of the continents above sea level is 700 meters. Hence the meteorological water power of the globe is about 9,000 million horse-power, and the technical water power is 5.5 per cent of this, or about 500 million horsepower. The quantity of fuel which this amount of energy can replace will depend on the form in which the energy is used. If it is used in the form of mechanical energy it is more than sufficient to replace all of the fuel now consumed, as the power obtainable from the mineral fuel consumed in 1909 is 270 million horsepower, while the technical water power of the globe is 500 million horse-power. But this superfluity will not long continue, for both the consumption of fuel and the utilization of water power are steadily and rapidly increasing. On closer examination, indeed, the excess proves to be only apparent, for a great deal of fuel is burned in order to produce heat, not mechanical energy. The thermal equivalent of one horse-power is 640 calories per hour, or about 5.5 million calories per year. Hence the available water power of the globe is equivalent to 2.8 X 10” calories per year, that is to about 40 per cent of the thermal effect of the coal mined in 1909. Thus we reach the conclusion that all the water power on earth could not furnish a sufficient substitute even for the present consumption of coal. This insufficiency is rapidly increasing and it cannot be annulled by any probable increase of the ratio between meteorological and technical water power, which we have taken as 5.5 per cent. Very little calculation is required to prove that winds and tides can never play an important part in the energetics of the world, although they may be useful in exceptional cases. All of the sources of energy heretofore considered, except the tides, we supplied by solar radiation. This fact suggests the possibility of obtaining energy directly from the sun's rays. We will consider the most favorable case, that of a tropical desert, where the effect of the rays is least diminished by clouds and obliquity of incidence. At the latitude of 20 degrees one square meter of horizontal surface receives annually 1.4 million calories from solar radiation. The thermal equivalent of one horse-power, therefore, is received by an area of 4 square meters, the equivalent of the earth's available water power is received by 2,000 square kilometers, and the equivalent of the world's consumption of coal in 1909 is received by 5,000 square kilometers. The desert of Sahara alone covers an area of 9 million square kilometers. The meteorological conditions for a capture of energy on a vast scale are thus provided. The capture has been attempted, but on a very small scale and by an ineffective method. The sun's rays have been made to furnish mechanical energy by generating steam in boilers. This method involves great losses, and is incapable of high efficiency. A more promising method consists in employing the solar radiation to form chemical compounds rich in latent energy ; the greater part of which could be re gained in the form of heat or electricity by converting these compounds into others, poor in energy. A beginning has been made in the realization of this idea, in laboratory experiments. This process of capturing the energy of solar radiation is constantly going .on, in the vegetable world, on a colossal scale. It will be of interest, therefore, to test its efficiency by an example. In a favorable season one hectare (about f.5 acres) of good land produces 40 tons of beets, containing 6 tons of sugar. One square meter, therefore, produces 600 grammes of sugar, the combustion of which will yield about 2,000 calories of heat. During the growing season of the beet (May 1 to September 15) one square meter of ground at the latitude of 50 degrees receives the equivalent of 300,000 to 400,000 calories in solar radiation. Hence the proportion of solar radiation that can be captured and utilized in this way is only 0.5 to 0.7 per cent. Nearly the same result is obtained when the wood produced in a forest is substituted for the sugar yielded by a beet field. Hence a productive area of 3.5 million square kilometers, equal to two thirds of European Russia, would be needed to furnish sufficient fuel to produce the thermal equivalent (7 X 10” calories) of the fossil fuel consumed in 1909. With favoring climatic conditions and skilful cultivation the yield here taken as an example can be multiplied many fold. Nevertheless the radiation engineer of the future will be compelled to adopt far more rational methods than those of the most successful agriculturists of to-day, in order to still the energy hunger of his fellow men, without encroaching upon the area required for the production of food. Will he succeed in producing a harvest of energy large enough and cheap enough to constitute a veritable substitute for coal? Upon the answer to this question, which cannot now be given, will depend the fate of our whole civilization, unless the future shall reveal available sources of energy, which are now unknown or but dimly foreseen, such as the immense store of latent atomic energy which produces 'the phenomena of radioactivity. Baffin Land, the largest island of the American Arctic archipelago (area about 236,000 square miles), is also one of the least well known. A tentative delineation of the northern part, but without actual surveys, was made by recent Canadian expeditions under Capt. Bernier, while the eastern coast of the Fox Basin, as shown on our latest maps, depends upon the Eskimo charts published in the narrative of Hall's second Arctic expedition and drawn in 1868. Although Scotch missionaries have been stationed on Cumberland Sound for thirty years, and Scotch traders have lived there and elsewhere on the east coast, no one ever succeeded in crossing the island from east to west until the year 1910, when the feat was accomplished by a young German ornithologist, Bern-hard Hantzsch, who unfortunately lost his life on his return journey the following year. A preliminary report of Hantzsch's explorations has just been published in Germany, and a larger work, including all the explorer's journals and notes, is in preparation. We wish to call attention to the fact that we are in a position to render competent services in every branch of patent or trade-mark work. Our staff is composed of mechanical, electrical and chemical experts, thoroughly trained to prepare and prosecute all patent applications, irrespective of the complex nature of the subject matter involved, or of the specialized, technical, or scientific knowledge required therefor. We also have associates throughout the world, who assist in the prosecution of patent and trade-mark applications filed in all countries foreign to the United States. Munn&Co., Patent Soticitors, 361 Broadway, New York, N. Y. Branch Office: 625 F Street, N. W., Washington, D. C.
This article was originally published with the title "Energy Sources of the Future"