OUR WASTE OF FUEL
As was shown in a previous chapter, we utilize very little of the energy in coal. Our steam railroads squander from 94 to 96 per cent of the coal they burn and our best turbine power plants throw away about 80 per cent. The coal we burn in domestic furnaces is most wastefully squandered. Maybe we shall learn how to use the energy in coal more efficiently and make it last longer, but eventually it will all be gone and then what are we going to do?
Of the other fuels available, petroleum takes the leading place, but we are hardly more economical in our use of this fuel and our oil supplies are diminishing much more rapidly than the stores of coal. In 1919 the United States produced 376,000,000 barrels of oil and consumed 418,000,000 barrels, having had to draw on Mexico for 42,000,000 barrels. Natural gas cannot last much longer and peat bogs are estimated at about half of one per cent of the coal supplies. Where shall we turn for heat and power when all these stores of energy are gone?
It has been estimated that the water powers of the earth, if fully developed, would probably supply about half of the energy that we now get out of coal. This is a never-failing supply of energy, and no doubt before we have begun to scrape the bottom of our coal magazines every river on earth that is capable of turning a wheel will be doing so to the limit of its capacity. Then there will be a readjustment of the manufacturing centers of the earth and remote regions such as Iceland, for instance, which has more available water power than Switzerland, will hum with machinery, while such countries as Great Britain, which is relatively poor in water powers, will have to give up manufacture and revert to agricultural pursuits.
But are there not other powers that can be used? If we could capture all the energy of the winds we should have ample power to do all the work that is now done on earth with a large margin to spare. It has been estimated that the winds contain 5,000 times as much energy as is obtained from coal, but how may we capture so fickle a power as the wind. It is so variable, sometimes exerting enough power to lift houses from their foundations and uproot giant trees, and again sinking to an absolute calm. In some places wind power is turned into electricity and then stored up in batteries; but the cost of doing this is high and at present uneconomical.
“BLUE COAL”
The ocean Is a vast storehouse of energy. The quiet but powerful rise and fall of ocean tides, and the tremendous energy of ocean waves, have been looked upon with envy by engineers. All sorts of schemes have been devised for capturing a part of this energy and putting it into the service of man. Water power has been aptly called “white coal” and ocean power “blue coal.” Wave energy is but another form of wind energy and hence just as fickle. There is plenty of power to be had, but it is a costly matter to build a power plant on the shores of the ocean and any day a storm may arise which will dash the machinery to pieces and sweep away the whole plant or convert it into a pile of wreckage. In a few places, however, Nature has provided a plant which the ocean has been unable to destroy and man has adopted the plant to furnish him with power. There is a rocky cave on the California coast which is exposed to the ocean swells. As the swells sweep into the cave they compress the air therein and this compressed air is trapped in a reservoir. Then the air that has been pumped by the ocean is put to useful work. There are similar caves on other rocky coasts which could be made to deliver power when coal becomes scarce and it becomes commercially practicable to exploit them, but the amount of power they would furnish would be a mere drop in the bucket.
SETTING TIDES TO WORK
The ocean tides are also immensely powerful, but the rise and fall of the water is so slight and so gradual in most places that an enormous plant is required to obtain any appreciable amount of power. In certain regions, however, tidal power is actually in use to-day. At high tide water flows into a large basin and at the ebb of the tide the outflow of the basin operates a water wheel or turbine. Power can be obtained while the basin is filling as well as while it is emptying. One serious objection to this plan is that the turbine operates intermittently and at irregular intervals, sometimes by day and sometimes by night, depending upon the tide. However, tide mills need not be exposed to the fury of ocean storms as are plants that seek to employ the power of ocean waves. In certain localities the conformation of the coast is such as to accumulate the tidal flow and produce enormous differences of level between ebb and flood tide. In the Bay of Fundy, for instance, the tide rises seventy feet and an appreciable amount of power could be obtained from the flow of water into and out of the bay. If a sea-level canal were dug across the Isthmus of Panama there would be a flow of water back and forth through it because the tides at the Pacific side have a rise and fall of only two feet while on the Atlantic side the tide rises twenty-two feet. Some power might be obtained from the tidal flow through this canal, but a fall of twenty feet in fifty miles would not produce a very swift current.