About 1900 marked the beginning of the use of electric energy on farms. One of the first farms to be wired was near Philadelphia, in 1898, and about this time the first farm electric motor was used, in California. THE MODERN PERIOD The modern period-featuring buildings designed to accommodate machinery and equipment for saving labor and controlling environment dates from about the period of the First World War. Building materials changed rapidly in this era. Farming trended more rapidly away from the traditional "way of life" toward an "industrial enterprise." By 1919, 1.6 percent of U.S. farms had received electric energy. This figure had increased to 10.9 percent by 1934. Wood shingles continued to be the primary roofing material through the 1920's, but then gave way to the new composition asphalt shingles. New framing methods New framing methods brought into use plywood, laminated rigidframe bents, insulating board, and pressed board-all aimed at fuller utilization of that important resource, the tree. In 1923 a farmer in Mulliken, Mich., contracted with a bridge company for an all-steel barn (said to be the first in the United States). Soon thereafter, many manufacturers could furnish steel hay barns, sheds, garages, hog houses, and brooder and chicken houses (fig. 4). New uses for concrete Concrete had been used for floors, tanks, slabs, walks, and foundations for some time, but its use for walls had been limited because of the heavy forming and equipment needed for monolithic construction. In 1925, concrete walls made from panels were tilted into position for a house in Iowa. Thus was eliminated the need for heavy forming by casting wall panels in skeleton forms laid on a flat surface. This technique has extended the use of concrete to machine sheds, trench and bunker silos, poultry houses, and dairy and other service buildings. The outlook for developing improved panels and for increasing their use is promising as more research effort is applied. Development of plastics Chemical research about the time of the Second World War began to develop a wide variety of plastic materials that have a wide variety of applications to farm buildings. These materials became available for use as cores, coatings, fillers, structural members, tubes, and pipes, and they show excellent promise for increasing application to the farmstead. New construction techniques Concurrent with development of new building materials and less wasteful use of materials sources were efforts to develop construction techniques that would more fully and efficienctly utilize the inherent strength of the materials incorporated into structures. Examples are the hyperbolic paraboloid (HP) roof section, which utilizes the tensile strength of thin sheets in contrast to the shear and bending resistance of heavier framing members; and improved joint design, which balances joint strengths with member strengths of trusses and other structural frames. Both of these reduce the amount of material required to support a given load over a given span. FIGURE 4. Steel is now widely used in farm structures. This is a modern dairy building under construction. Pole construction, used for temporary buildings since pioneer days, has recently achieved wide popularity for permanent structures. Improved methods of thoroughly impregnating the poles with preservatives have been discovered and new tractor attachments, such as posthole diggers and lifts, make it possible to erect poles with farm equipment. Pole buildings generally cost less and require less carpentry skill and time for erection than conventional methods of construction. The improved preservatives and methods of applying them have been important in conserving our wood resources. Tests of holding power by USDA agricultural engineers (fig. 5) were helpful in developing design criteria for pole construction. During the 1950's the livestock farmer struggled in an ever-tightening cost-price squeeze. The margin between production expenses and gross income narrowed by one-fourth during this decade (31, table 1H). Efforts to improve production efficiency, and thus lower production costs, gained momentum. Reduction of wastes of all kinds structures, materials, power, and labor-assumed new importance. Research to improve buildings, equipment, methods, power sources, and their use was initiated and expanded. Expansion of rural electric lines after World War II by both private power companies and REA-financed cooperatives has resulted in an investment of more than $5 billion to provide service on more than 96 percent of U.S. farms. By 1959, the Nation's farms used 27 billion kilowatt-hours of electric power annually. This is one reason an hour of labor now produces 4%1⁄2 times as much as in 1910 (12). Materials Handling Conference Widespread interest led to a nationwide Materials Handling Conference, sponsored by the American Society of Agricultural Engineers (ASAE) and held at Iowa State College, Ames, Iowa, in September 1958. This conference was attended by agricultural engineers, economists, farm managers, and others from all parts of the United States and some foreign countries and provided opportunity for worthwhile exchange of much valuable information. The formal papers presented at the conference were published by the society (2). Conference on Farmstead Engineering A similar nationwide Conference on Farmstead Engineering, sponsored by the ASAE, the Agricultural Engineering Research Division of the U.S. Department of Agriculture, and the University of Illinois, was held at the University of Illinois, Urbana, Ill., in September 1960. It was likewise broadly attended and the source of much valuable information. The formal papers presented have been published by the society (3). Increased demand for water Demand for water on the farmstead has increased over the years and will continue to increase in the future. The modern farmstead has piped water under pressure in the dwelling, in the service buildings, and at strategic points around the yards and lots. Developing supplies of satisfactory quality and quantity to meet these demands becomes more and more difficult. The increased use of water increases problems of liquid wastes disposal. The problems are particularly difficult with respect to disposal of liquid manures in the vicinity of metropolitan areas as these areas continue to spread out into formerly agricultural areas. Much more research is needed on these problems. PROBLEM AREA DOCUMENTATION Time is running out; our civilization's energy needs will soon outrun nature's declining store of fossil fuels. Before this happens, ways must be found to use solar and atomic energy. Solar energy must be collected and stored. Collection and storage are the keys. New materials are important in the work now being done. Especially important is plastic for solar collectors. It has been hypothesized (24) that nearly 10 percent of our energy will be obtained from solar collectors by 2050. Dr. Abbot of the Smithsonian Institution reported in 1939 that one southwest State could supply from solar radiation, energy equivalent to that currently used for heat, light, and power in all the United States (1). AVAILABILITY OF SOLAR ENERGY All known energy sources on the earth, with the exception of tides and nuclear fuels, are products of radiation from the sun. Energy stored in the fossil fuels (such as coal, oil, and natural gas) and in growing plants require sunlight for photosynthesis. Winds are caused by variations in the heating of air by solar energy. Even waterpower is available because the sun's heat has evaporated sea water and lifted it to higher levels. The thermodynamic efficiency of these natural processes, however, is low. Thus, the application of engineering principles may make sunpower much more useful to mankind. According to a report of the President's Materials Policy Commission (23), an average of 1,500 times the present total daily fuel energy requirements of the United States strikes its land area each. day in the form of solar energy. In spite of the abundance of this undiminishing source of power the bulk of the energy now used for heat and mechanical power comes from fossil fuels which are virtually irreplaceable. The intensity of solar radiation at normal incidence, at the outer limit of the earth's atmosphere, and at the mean solar distance, is termed the solar constant. At present the most accurate determinations fix the value of the solar constant at 419.40 B.t.u./(ft.2) (hr.) +32 percent. The variation is due primarily to the fact that the earth is closer to the sun in winter than in summer (17). Because of several depletion factors, however, solar radiation intercepted by a surface on the earth at a given time is less than the solar constant. The intensity at a given place varies with the latitude, the time of year, the time of day, and the attitude of the receiving surface (fig. 6). On cloudless days when the sun is directly overhead the intensity of direct solar radiation on a normal surface reaches a maximum of about 340 B.t.u./(ft.2) (hr.). Insolation rates for a cloudless day on various oriented surfaces at 35° north latitude at the summer solstice are shown in figure 7. 86770 0-62- 4 |