Wind power

“ It can be readily seen that winds are a form of energy, as we have innumerable instances of the power and energy which they exert. Advantage is taken of that kinetic energy by means of windmills, in which the energy of the wind is imparted to the revolving sails, and thence to the machinery, various forms of mechanical work being the result, as, for example, the grinding of corn, or the pumping of water. ”

“ The land and sea breezes express more than double the amount of wind force which the direct heat of the sun is capable of exerting upon the tradewinds. I say more than double, because in the land and sea breezes the wind-producing power acts alternately on the land and on the sea—in opposite scales of the balance; whereas in the trade-winds it acts all the time in one scale—in the sea scale ”

“ Wind power is the cheapest power we have. A windmill properly proportioned to its work is a great help, especially when it is attached to a good pump for the purpose of lifting water into an elevated tank from which it is piped under pressure for domestic purposes and for watering live-stock. ”

“ Of late, however, small windmills, especially designed with superior mechanical skill, have been rapidly growing in popularity in this country, mainly for pumping water for railway and domestic purposes, an application for which these devices are excellently adapted; and I entertain no doubt that there are many situations where work is to be done that does not demand a continuous exercise of power, and where the prime consideration to be observed is the element of cheapness, where wind-power might be most advantageously employed. ”

“ Hence, upon the whole, a considerable part of the world is well suited for investigations upon the best methods of deriving power from the winds. The first requisites of a wind-power machine are some sort of a motor driven by the wind, and an accumulator to store the energy and yield it at the required moment. ”

“ The utility of the wind, however, in generating the power in a stationary mechanism is familiar to everyone. Windmills were constructed at a comparatively early period, and notwithstanding all the recent progress in the development of steam and electrical power, this relatively primitive so-called prime mover still holds its own in agricultural districts, particularly in its application to pumps. ”

“ The great significance and value of the newer generalization lies not alone in the recognition of the geologic potency of wind-power as an agency of erosion, or as a means of forming such vast continental deposits as the loess, but of its tremendous efficiency as a general or regional denuding force. ”

“ THE POSSIBILITY that the wind was the first inanimate power utilized by man, has already been referred to. There are records of the use of sailing vessels in Egypt that date as far back as 6,000 years before Christ. Navigators of that early date, however, could hardly claim to have mastered the wind. They merely used wind power when the wind was disposed to help them. ”

“ From time immemorial people knew the two motive forces of flowing water and of streaming air, or wind. When the steam-engines came into use, the latter had gradually superseded the former, partly because rapidly flowing or falling water is not always procurable, partly also because the supply of water, as well as its power, depends on the quantities of rain falling in the higher districts. The latter inconvenience, the variability of power, made itself still more strongly felt in the application of the wind. ”

“ The power-house, with its turbines and other machinery, involves a comparatively large outlay, but if the pump can be directly driven from the turbines, so that the cost of attendance is reduced to a minimum, the system should certainly receive consideration.
Although the wind is always available in every district, it is more frequent and powerful on the coast than inland. The velocity of the wind is ever varying within wide limits, and although the records usually give the average hourly velocity, it is not constant even for one minute. ”

“ Water-power is, however, limited, and is generally least available where small motors are most wanted—in populous cities. Doubtless in many locations, where the windmill is employed to supply water to a house, a combination of wind and water power might readily be made which would prove quite satisfactory. ”

“ EXPERIMENTS IN THE OPEN WIND
I have pointed out21 that an indefinite source of power for the maintenance of mechanical flight, lies in what I have called the “internal work” of the wind. It is easy to see that the actual effect of the free wind, which is filled with almost infinitely numerous and incessant changes of velocity and direction, must differ widely from that of a uniform wind such as mathematicians and physicists have almost invariably contemplated in their discussions. ”

“ When any portion of the earth’s surface is periodically more heated above its normal temperature, or average for the year, than the neighboring region, the resulting abnormal temperature gradient causes a periodic surface wind tending toward the excessively heated place, and a counter wind above. That is, the cooler and heavier column of air sinking and uplifting the lighter, results in a lowering of the common center of gravity of the two 386columns of air, and thus furnishes the driving power of the wind. ”

“ In such very large single farms, achievable power densities as low as 1 MW/km 2 have been suggested. Our availability assumptions on land imply a small likelihood of a necessity for very large single wind farms. ”

“ The useful power developed by windmills when pumping water in a moderate wind, say of sixteen miles an hour velocity, is not very high, ranging from one twenty-fifth horse-power for an eight and one-half foot wheel to one and one-half horse- [Pg 42] power for a twenty-five foot wheel. The claims of some makers of windmills as to the power developed should be accepted with caution. ”

“ It was first utilised in windmills, whose sails are nothing more nor less than an immense screw which is turned by the action of the wind on its surface. In the case of turbine water-wheels, where perhaps 970 cubic feet of water are utilised by means of a mechanism not larger than a hat, we see another illustration of it, with this difference, that water takes the place of wind as the motive power. ”

“ In one respect the strain on poles that carry aluminum may be greater than that on poles with equivalent copper lines, namely, in that of wind pressure. A wind that blows in a direction other than parallel with a transmission line tends to break the poles at the ground and prostrate the line in a direction at right angles to its course. The total wind pressure in any case is obviously proportional to the extent of the surface on which it acts, and this surface is measured by one-half of the external area of all the poles and wires in a given length of line. ”

“ The velocity of these vapors, though not necessarily in reality greater than that of the central clouds, appears greater, owing to their proximity, and, of course, also to the usual presence of a more violent wind. They are also apparently much more in the power of § 4. They are subject to precisely the same great laws.the wind, having less elastic force in themselves; but they are precisely subject to the same great laws of form which regulate the upper clouds. They are not solid bodies borne about with the wind, but they carry the wind with them, and cause it. ”

“ From Table V it will be seen also that a wind velocity of fifteen miles per hour develops a power three times as great as an eight-mile wind, and a twenty-mile wind is twice as powerful as a fifteen-mile, or six times that of an eight-mile. Hence, a small increase in velocity greatly increases the power of the windmill, while a low velocity gives but little working force. ”

“ Wind'mill', a wheel driven by wind to obtain power. Windmills vary in diameter from eight to thirty feet. The largest sizes in ordinary wind developing as high as four H. P. The ordinary pumping-wheel develops less than one quarter H. P. For service requiring small power, and where constant operation is not vital, as in pumping water and grinding feed, windmills are, according to Wolff, the cheapest power available. ”

“ It is difficult to believe, but it is, nevertheless, a fact, that since time immemorial man has had at his disposal a fairly good machine which has enabled him to utilize the energy of the ambient medium. This machine is the windmill. Contrary to popular belief, the power obtainable from wind is very considerable. Many a deluded inventor has spent years of his life in endeavoring to "harness the tides," ”

“ SOFTLY, O midnight Hours!
Move softly o'er the bowers
Where lies in happy sleep a girl so fair!
For ye have power, men say,
Our hearts in sleep to sway,
And cage cold fancies in a moonlight snare.
Round ivory neck and arm
Enclasp a separate charm;
Hang o'er her poised, but breathe nor sigh nor prayer:
Silently ye may smile,
But hold your breath the while,
And let the wind sweep back your cloudy hair!
Bend down your glittering urns,
Ere yet the dawn returns,
And star with dew the lawn her feet shall tread ”

“ The vibrations in the air were so terrific as to break windows and overturn frame houses over a hundred miles away, and the pressure wave, like some huge blast of wind, traveled round the world three times before it died down. ”

“ In middle age, its violent forces are directed toward maintenance of the colossal wind system. The total energy it can derive from heat and moisture no longer produces an outflow above in excess of the inflow of air at the bottom. ”

“ It is not enough that we have the evaporation of moisture that will ascend into the higher regions of the air and there be condensed into cloud and possibly rain, but we must have the means for distributing these conditions over a large area, and for this purpose we have the phenomenon of wind. Why the winds blow can be accounted for to a certain extent,—we might say to a large extent,—but there yet remain many unsolved problems relating to wind and weather. Of the phenomena of wind we will speak more fully in a future chapter. ”

“ The need of irrigating prairies, inundating vines, drying marshes, and accumulating electricity cheaply has, for some time past, led to a search for some means of utilizing the forces of nature better than has ever hitherto been done. Wind, which figures in the first rank as a force, has thus far, with all the mills known to us, rendered services that are much inferior to those that we have a right to expect from it with improved apparatus; for the work produced, whatever the velocity of the wind, has never been greater than that that could be effected by wind of seven meters per second. ”

“ Thus the meridional currents produced by overheating combine with the currents embracing the whole [p. 46] wind system of the earth, with the result of disseminating the excess of temperature and humidity of the torrid zone over the temperate and arctic zones, thereby producing the prevailing winds.
8. This is accomplished by the production of alternating local depressions and elevations of barometric pressure by the disturbance of indifferent equilibrium in the upper layers of the air. ”

“ During fog, rain, hail, sleet, snow, and thunderstorms, the electrical state of the air undergoes many variations. The intensity of the electricity increases with hot weather following a series of wet days, or of wet weather coming after a continuance of dry days. The atmospheric electricity, in fact, seems to depend for its intensity and kind upon the direction and character of the prevailing wind, under ordinary circumstances. It has an annual and a diurnal variation. There is a greater diurnal change of tension in winter than in summer. ”

“ A current of air increases in velocity where the space of its passage is straitened: the same wind which was moderate in an open plain becomes violent in passing through a narrow passage in a mountain, or between two [100] lofty buildings; and its most violent action is at the top of these structures or mountains, for air being compressed by these obstacles, its density and mass becomes increased, and as the velocity remains, the force or momentum of the wind naturally becomes much stronger. ”

“ It is a reservoir of dynamical force for the winds—a regulator in the grand meteorological machinery of the earth. The heat which is transported by the vapours with which that sea loads its superincumbent air is the chief source of the motive power which gives to the winds of the southern hemisphere, as they move through their channels of circulation, their high speed, great regularity, and consistency of volume. ”

“ When these winds blow, the air is charged with electricity, until, the tension of the atmosphere having grown insupportable, a tempest comes to restore the equilibrium, to give place to another wind, coming from the south-west, and known as the pampero. ”

“ If the north-east wind changes to a north-west wind, it shews either that a part of the northern air descends upon us in a spiral eddy, or that a superior current of southern air is driven back; but if a north-east wind be changed into a south-east wind it shews that the northern air is become retrograde, and that in a day or two, as soon as that part of it has passed, which has not gained the velocity of the earth's surface in this latitude, it will become a south wind for a few hours, and then a south-west wind. ”

“ Lanchester maintains that the work done by the motor in making headway against the wind for a certain distance calls for more engine energy, and consequently more fuel by 30 per cent, than is saved by the helping force of the wind on the return journey.
CHAPTER XIV. ABOUT WIND CURRENTS, ETC.
One of the first difficulties which the novice will encounter is the uncertainty of the wind currents. With a low velocity the wind, some distance away from the ground, is ordinarily steady. As the velocity increases, however, the wind generally becomes gusty and fitful in its action. ”