Page 14 RAIN January 1978 The electrical system reflects the intended use of the machine-partly for heating and partly for electric power. (Previous large machines have been built for electric power production only.) The generator (2000 kw, 3000 volts) delivers variable frequency a-.c. power, which goes down a cable to the ground and under the ground for some distance to a nearby control house. There it is transformed to 440 volts, rectified to d.c., and _inverted to 50 hertz a.c., synchronously phased with the local power grid. Resistive load, thermal storage (resistively heated), electrical disconnects, and other control circuitry are connected between the windmill and the transformer. Because the generator was not custom designed for the windmill, it is somewhat fully sized. Also, about 80 percent of energy use at the Tvind Schools is as heat, only 20 percent as electricity. Thus the rectifier-inverter system is smaller, electrically, than the generator, and is rated at 500 kw, not 2000. It is expected that this will be ample to handle the electrical load of the school. At times there will be a surplus which may be sold to the local power company. Wind generator output in excess of 500 kw will be used as heat. The economic value of electricity sold into the net grid at wholesale rates is about 10 Danish ¢re/kwh (l.6¢kwh at 1977 exchange rate); the economic value of the same electricity converted to heat and used to save fuel oil is about the same. Fully as remarkable as the technological features of the Tvind windmill are the place where it was built and the way in which it was built. The Tvind Schools are part of the Danish education system; they receive money from the state, but they are not public schools in the usual sense. They are better described as private schools receiving public funds to pay the costs of educating the students. They have complete autonomy and the education program is quite out of the ordinary. The curriculum includes problems in the third world, problems in Denmark, and many other things not commonly covered in depth in the public schools, as well as the usual public school subjects. The students do practical work as well as classroom exercises. There are 3 schools, a teacher training college, a 'h¢jskole' and an 'efterskole.' The h¢jskole students are age 18 and up; the efterskole students are 14 to 18 years. Many of the h¢jskole students have been working for some time before returning to school. Students and staff live at the Tvind community, or in one of the outpost communities, in a cooperative and communal manner. Staff salaries are pooled, and a major fraction of the money is used for projects of the school, of which the windmill is one. Staff and students work together on these projects with a high degree of motivation and commitment. The cooperative projects, the egalitarian social structure, and the warm informal atmosphere contrast noticeably with the competitive and hierarchical conditions of most universities, companies and government laborator.ies. I. The Tvind Schools are a frees'tanding community of about 1000 people located 4 km south of the town of Ulfborg (which is itself 90 km north of the city of Esbjerg) in West Jutland. Tvind is about 10 km from the North Sea coast in the direction of the prevailing westerly wind. Address: Energikontor, Tvindskolerne, Tvind, 6990 Ulfborg, Denmark. Construction work on the windmill project began in May ! 975 and has pro~ressed steadily since, with some changes m plan as the project evolved. The motivation for the project was not to build the world's largest windmill. Rather, it was an effort to gain energy self-sufficiency for the school by using a renewable energy source. The best renewable energy source at Tvind is wind. (There are some solar collectors on Tvind buildings, but solar energy in the winter is a difficult proposition in Denmark.) The motivation came first, the technology was acquired-and not without effort-as the project proceeded. The great windmill stands today as an impressive professional accomplishment-conceived, organized, and mainly built, by amateurs. Another matter worth noting is the cost and the funding of the machine. To the point of completed assembly and installation, but before first rotation, about 4 million Danish kroner had been spent ($660,000 U.S.). None of this money came from the government, and none from any large private corporation or foundation. Essentially, all the funds were contributed by staff members at the school from salary income. A tremendous amount of unpaid labor was donated to the project by members of the "windmill team," volunteer workers from all over Denmark. A number of skilled fulltime workers spent extended periods at Tvind; they received living expenses but no salari~s. Some outside labor for specialized jobs was hired at regular rates. The cost of the outside labor and the living expenses of the full-time workers is inNovember 17, 1977: bolting on the last 88½ ft. blade, 2½ years after May 29, 1975, ground-breaking (note size of workers atop rotor hub and in open nacelle). eluded in the 4 million kroner. Although it cost more than had been originally estimated, much less money was spent than on machines of comparable size built elsewhere. When the machine is in regular operation it is expected to supply all the energy needs of the school, both electricity and heat, and to generate some surplus electricity for sale to the local power company. The workers at Tvind have built a machine which is a first rank achievement in technology, which demonstrates the power of community organization, and which shows the way in renewable energy implementation. 2. This report was written while the author was a visitor at the Neils Bohr Institute, Copenhagen.
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