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Preliminary tests of a solar heated thermoelectric converter
superheated to 400 to 500 deg C at 100 to 150 atm was designed and constructed. It consists of a beehive collector of selective transparency type, formed by about 2000 small glass tubes, placed on a plate suitably prepared and varnished black, so as to absorb ahnost all the incident radiation. On this collector, with a surface of about 0.50 sq meter, the radiant energy from conical aluminium mirrors is concentrated in the geometrical ratio of 16:1. The device, mounted on a sturdy support, provided with the requisite positioning levers, is installed on a small truck and can be easily moved after disassembly of the bulkiest parts. The results can be read directly on an instrument board with thermoelectric thermometers, pressure gauges, etc. The cellular structure of the absolute blackbody may have numerous other applications. As an example, the paper describes a solar furnace for temperatures of the order of 3000 deg C, consisting of a cone-frustum mirror concentrating the energy on a cylinder placed on its axis and protected by a cellular structure formed, stretched on frames, and remote from the hot portions, In a different area of collector application, the cellular structure described has the properties of being cold as well as transparent in one direction. These properties may be usefully applied, under particular conditions, for heat insulators of negligible thermal mass at very high temperatures.
of the most economical power sources in the power range of 1 to 100 watts. B r e i h a n , R o g e r R., F a r r i n g t o n D a n i e l s , J o h n A. D u f l i e a n d G e o r g e O. G. LSf, S o l a r E n e r g y L a b o r a t o r y , U n i v e r s i t y of W i s c o n s i n , l~Iadison, W i s c o n s i n , " P r e ] i m i n a r y T e s t s of a S o l a r H e a t e d T h e r m o e l e c t r i c Converter", United Nations Conference on New S o u r c e s of E n e r g y , R o m e , 196], 7 p. Illus. Preliminary data are reported on the production of electric currents by focussed sunlight on a thermoelectric converter made at the laboratories of the Westinghouse Corporation. The collector with aluminized mylar on a plastic parabolic reflector 6 feet in diameter focussed less than 50 percent of the intercepted solar radiation on the converter which was 5 inches square. The converter received 16 kilocalories of heat and gave up 12 kilocalories of heat to the cooling water while producing a maximum of 40 watts of electricity at low voltage. Some of the ways in which improvements can be made are pointed out.
YI--Vapor, Hot Air, and Fluid Heat E n g i n e s F o o d a n d A g r i c u l t u r e O r g a n i z a t i o n of t h e U n i t e d Nations, Nutrition Div., Rome, Italy, "Report on Tests Conducted using the Telkes Solar Oven and the Wisconsin Solar Stove over the Period July to S e p t . , 1959," U n i t e d N a t i o n s C o n f e r e n c e o n N e w S o u r c e s of E n e r g y , R o m e , 1961, 12 p. Illus. Two solar stoves, one an oven type (Telkes) and the other a parabolic reflector type (Wisconsin) were tested at FAO Headquarters during July, August and September 1959. In these tests it has been shown that water can be boiled considerably faster on the Wisconsin solar stove than in the Telkes oven. However, performance of the Telkes oven is less affected by infrequent positioning of the stove, by clouding of the sun, and by wind. In addition, it is necessary to consider that the Telkes oven is more expensive as well as more complicated than the Wisconsin stove with greater risk of mechanical difficulties and more need for repairs and spare parts, V--Thermoelectric K o b a y a s h i , 5,Iastsugu, D i r . , R e s e a r c h L a b o r a t o r y , N i p p o n E l e c t r i c Co., L t d . , J a p a n , " T h e r m o - E l e c t r i c Generator", United Nations Conference on S o u r c e s of E n e r g y , R o m e , 1961, l l p. Illus.
Mechanical Power and Electricity Production by 5 I e a n s of P i s t o n E n g i n e s a n d T u r b i n e s " , U n i t e d N a t i o n s C o n f e r e n c e o n N e w S o u r c e s of E n e r g y , R o m e , 1961, 16 p. Illus. For sizes in the range of a few kilowatts, there are good prospects of getting solar power in the near future at around 5 US cents per Kwh in a sunny climate using realistic interest and amortisation charges but omitting maintenance and operating costs. Many consumers would consider 5 cents per Kwh a reasonable price to pay for power in isolated communities, so the prospects for kilowatt power packages is quite good. For large central power units, in the megawatt class, a lower power price is essential and completely different types of collector--of an order of magnitude cheaper per unit area-must be evolved. Two suggestions have been forthcoming one using plastic covers and hence having a high amortisation rate and one--the solar pond--using no plastics and amortised over a longer period. The solar pond still requires the solution of some serious problems: an extensive research programine is being actively pursued in Israel on this project and if successful, could result in power costs of the order of 1 cent per Kwh.
New
Utilization of some silicides of transition metals for the purpose of thermoelectric generator is reported. The raw materials of the silicides are abundant on earth and no such high purities of the materials as in the case of semi-conductor technology are required. U-shaped p-n junction is constructed by pressing and sintering the powder of the component materials. Due to the high densit'es and low mobilities of current carriers in the silicides, the resistivities of the sintered materials are not increased seriously. Thermoelectric properties of the silicides are given in the temperature range between room temperature and 1000 deg C. Merits of utilization of the silicides of transition metals are as follows: (i) The raw materials are abundant on earth, and no such high purities of the materials as in the case of transistor technology are needed. (it) They are inherently refractory and suitable to a thermoelectric generator for high temperature use, resulting in a relatively high conversion efficiency. (iii) Construction of the U-shaped p-n junction by sintering process is possible due to the low mobilities of current carriers in the silicides. Although the conversion efficiency of the sintered junction is reduced a little compared with that of the junction constructed with the pulled crystals, cost reduction and simplicity in construction of p-n junction free from contact resistance and cracks are remarkable. The generator constructed by the sintered elements may be one 146
Tabor, Harry, Director, National Physical Laboratory of I s r a e l , J e r u s a l e m , I s r a e l , " U s e of S o l a r E n e r g y for
C o t t o n , E u g e n e S., W i l l i a m P . L y n c h , W a l t e r Z a g i e b o y ] o a n d J o h n 5{. D a v i e s , P i o n e e r i n g R e s . D i v . , Quartermaster Res. and Eng. Command, U.S. Army, Quartermaster Res. and Eng. Center, Natick, 5Iass., U . S . A . , " I m a g e Q u a l i t y a n d U s e of t h e U . S . A r m y Quartermaster Solar Furnace," United Nations Conf e r e n c e o n N e w S o u r c e s of E n e r g y , R o m e , ]961, 26 p. Illus. The U. S. Army Quartermaster Corps has been concerned for a number of years with the need for protective materials which can be exposed to intense thermal radiation for short periods of time. To facilitate these studies a solar furnace was completed in September 1958 which produces an image approximately 10 cm in diameter. The Quartermaster solar furnace utilizes a two-mirror optical system; it consists of a movable array of fiat mirror segments, called the heliostat, which reflects solar radiation horizontally, and a fixed array of concave mirror segments, called the concentrator, which receives the reflected radiation and forms the convergent beam. By properly aligning the individual segments, a composite solar image can be formed at a point on the system axis inside the test chamber, a working enclosure and control center for the entire system. Solar Energy
of the most economical power sources in the power range of 1 to 100 watts. B r e i h a n , R o g e r R., F a r r i n g t o n D a n i e l s , J o h n A. D u f l i e a n d G e o r g e O. G. LSf, S o l a r E n e r g y L a b o r a t o r y , U n i v e r s i t y of W i s c o n s i n , l~Iadison, W i s c o n s i n , " P r e ] i m i n a r y T e s t s of a S o l a r H e a t e d T h e r m o e l e c t r i c Converter", United Nations Conference on New S o u r c e s of E n e r g y , R o m e , 196], 7 p. Illus. Preliminary data are reported on the production of electric currents by focussed sunlight on a thermoelectric converter made at the laboratories of the Westinghouse Corporation. The collector with aluminized mylar on a plastic parabolic reflector 6 feet in diameter focussed less than 50 percent of the intercepted solar radiation on the converter which was 5 inches square. The converter received 16 kilocalories of heat and gave up 12 kilocalories of heat to the cooling water while producing a maximum of 40 watts of electricity at low voltage. Some of the ways in which improvements can be made are pointed out.
YI--Vapor, Hot Air, and Fluid Heat E n g i n e s F o o d a n d A g r i c u l t u r e O r g a n i z a t i o n of t h e U n i t e d Nations, Nutrition Div., Rome, Italy, "Report on Tests Conducted using the Telkes Solar Oven and the Wisconsin Solar Stove over the Period July to S e p t . , 1959," U n i t e d N a t i o n s C o n f e r e n c e o n N e w S o u r c e s of E n e r g y , R o m e , 1961, 12 p. Illus. Two solar stoves, one an oven type (Telkes) and the other a parabolic reflector type (Wisconsin) were tested at FAO Headquarters during July, August and September 1959. In these tests it has been shown that water can be boiled considerably faster on the Wisconsin solar stove than in the Telkes oven. However, performance of the Telkes oven is less affected by infrequent positioning of the stove, by clouding of the sun, and by wind. In addition, it is necessary to consider that the Telkes oven is more expensive as well as more complicated than the Wisconsin stove with greater risk of mechanical difficulties and more need for repairs and spare parts, V--Thermoelectric K o b a y a s h i , 5,Iastsugu, D i r . , R e s e a r c h L a b o r a t o r y , N i p p o n E l e c t r i c Co., L t d . , J a p a n , " T h e r m o - E l e c t r i c Generator", United Nations Conference on S o u r c e s of E n e r g y , R o m e , 1961, l l p. Illus.
Mechanical Power and Electricity Production by 5 I e a n s of P i s t o n E n g i n e s a n d T u r b i n e s " , U n i t e d N a t i o n s C o n f e r e n c e o n N e w S o u r c e s of E n e r g y , R o m e , 1961, 16 p. Illus. For sizes in the range of a few kilowatts, there are good prospects of getting solar power in the near future at around 5 US cents per Kwh in a sunny climate using realistic interest and amortisation charges but omitting maintenance and operating costs. Many consumers would consider 5 cents per Kwh a reasonable price to pay for power in isolated communities, so the prospects for kilowatt power packages is quite good. For large central power units, in the megawatt class, a lower power price is essential and completely different types of collector--of an order of magnitude cheaper per unit area-must be evolved. Two suggestions have been forthcoming one using plastic covers and hence having a high amortisation rate and one--the solar pond--using no plastics and amortised over a longer period. The solar pond still requires the solution of some serious problems: an extensive research programine is being actively pursued in Israel on this project and if successful, could result in power costs of the order of 1 cent per Kwh.
New
Utilization of some silicides of transition metals for the purpose of thermoelectric generator is reported. The raw materials of the silicides are abundant on earth and no such high purities of the materials as in the case of semi-conductor technology are required. U-shaped p-n junction is constructed by pressing and sintering the powder of the component materials. Due to the high densit'es and low mobilities of current carriers in the silicides, the resistivities of the sintered materials are not increased seriously. Thermoelectric properties of the silicides are given in the temperature range between room temperature and 1000 deg C. Merits of utilization of the silicides of transition metals are as follows: (i) The raw materials are abundant on earth, and no such high purities of the materials as in the case of transistor technology are needed. (it) They are inherently refractory and suitable to a thermoelectric generator for high temperature use, resulting in a relatively high conversion efficiency. (iii) Construction of the U-shaped p-n junction by sintering process is possible due to the low mobilities of current carriers in the silicides. Although the conversion efficiency of the sintered junction is reduced a little compared with that of the junction constructed with the pulled crystals, cost reduction and simplicity in construction of p-n junction free from contact resistance and cracks are remarkable. The generator constructed by the sintered elements may be one 146
Tabor, Harry, Director, National Physical Laboratory of I s r a e l , J e r u s a l e m , I s r a e l , " U s e of S o l a r E n e r g y for
C o t t o n , E u g e n e S., W i l l i a m P . L y n c h , W a l t e r Z a g i e b o y ] o a n d J o h n 5{. D a v i e s , P i o n e e r i n g R e s . D i v . , Quartermaster Res. and Eng. Command, U.S. Army, Quartermaster Res. and Eng. Center, Natick, 5Iass., U . S . A . , " I m a g e Q u a l i t y a n d U s e of t h e U . S . A r m y Quartermaster Solar Furnace," United Nations Conf e r e n c e o n N e w S o u r c e s of E n e r g y , R o m e , ]961, 26 p. Illus. The U. S. Army Quartermaster Corps has been concerned for a number of years with the need for protective materials which can be exposed to intense thermal radiation for short periods of time. To facilitate these studies a solar furnace was completed in September 1958 which produces an image approximately 10 cm in diameter. The Quartermaster solar furnace utilizes a two-mirror optical system; it consists of a movable array of fiat mirror segments, called the heliostat, which reflects solar radiation horizontally, and a fixed array of concave mirror segments, called the concentrator, which receives the reflected radiation and forms the convergent beam. By properly aligning the individual segments, a composite solar image can be formed at a point on the system axis inside the test chamber, a working enclosure and control center for the entire system. Solar Energy