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Energy use in India
Energy. Vol
I, p 335.
Pergamon Press 1976.
Printed in Great Britain
ENERGY NEWS Salinity power
An indirect form of solar energy is available theoretically as the result of mixing fresh and saline waters. Extraction of salination energy may be accomplished conceptually by either mechanical’ (e.g. an osmotic salination converter) or electrical’ (e.g. a dialytic battery) devices. Seawater salinity potential is approximately 22.4 atmospheres, which is equivalent to the hydrostatic head of a 225-m column of water. Dilution of 1 m3/sec of fresh water into a large volume of seawater dissipates approximately 2.24 MW of salinity power, a part of which may be recoverable. For total world river flows of about 1 x lo6 m3/sec, salinity power constitutes a theoretically renewable energy resource of 2.2 x 10”MW (optimistically convertible to 0.44 to 1.1 x lo6 MW,), which may be compared with the 1973 world-wide average rate of electrical-power generation of -0.7 x 10”MW,. Preliminary electrical power-cost goals for an osmotic salination design are -200 mills/kWh, for salination by seawater’.3 and -5 mills/kWh, for salination by Dead Sea brine.’ Direct conversion of salinity power to electricity may be accomplished by a dialytic battery, which consists of an array of alternating anion and cation exchange membranes. The operation of a dialytic battery is essentially the reverse of conventional electrodialysis desalination processes. For advanced ion exchange membranes, outputs of 1.7 W/m’ for salination by seawater and costs of -$1/m* may be attainable. Thus, the capital cost of the membranes would amount to $59O/kW,, which for a IO-yr lifetime and a plant factor of 90% converts to an energy cost of - 10 mills/kWh,. The cost estimates of Loeb3 and Weinstein and Leitz* should warrant further assessments of the potential of electrical-power generation from salinity differences. REFERENCES I. R. S. NORMAN, Science 186, 350-352 (1974). 2. J. N. Weinstein and F. B. Leitz, Science 191, 557-559 (1976). 3. S. LOEB, Science 189, 654-655 (1975).
Energy Center, UCSD La Jolla, CA 92093, U.S.A. Energy use in India
Roger Revelle in “Energy use in rural India” [Science 192,%9-975 (1976)]has indicated that actual per capita energy consumption in India is about 3 times larger than is normally estimated. The reason for this large discrepancy is that people in rural areas of poor countries tend to make relatively heavy use of wood, dried cow dung, plant refuse, and of animal and human work, which are not included in estimates of commercial energy consumption. Daily per capita energy consumption in India from all sources corresponds to (1.46 x 10’/365) Btu = 6.87 x lo-’ bbl, or about 4.3% of current U.S. consumption. Roughly one third of the food energy intake of the entire Indian rural population is expended on manual labor. About 5 1.5% of 500 x IO9hours per year of human labor are spent on agriculture, domestic activities consume 39.5%, and all other occupations together about 9%. According to Revelle, energy consumption in rural India should be more than tripled at a cost of about $3.2 x lo’, which could be paid for by exporting about 10% of increased food grain and would yield refuse with a potential energy content of about 2.8 times the additional energy required. Proper utilization of the energy contents of this heavy refuse production remains as a technological challenge. S.S.P.
335
I, p 335.
Pergamon Press 1976.
Printed in Great Britain
ENERGY NEWS Salinity power
An indirect form of solar energy is available theoretically as the result of mixing fresh and saline waters. Extraction of salination energy may be accomplished conceptually by either mechanical’ (e.g. an osmotic salination converter) or electrical’ (e.g. a dialytic battery) devices. Seawater salinity potential is approximately 22.4 atmospheres, which is equivalent to the hydrostatic head of a 225-m column of water. Dilution of 1 m3/sec of fresh water into a large volume of seawater dissipates approximately 2.24 MW of salinity power, a part of which may be recoverable. For total world river flows of about 1 x lo6 m3/sec, salinity power constitutes a theoretically renewable energy resource of 2.2 x 10”MW (optimistically convertible to 0.44 to 1.1 x lo6 MW,), which may be compared with the 1973 world-wide average rate of electrical-power generation of -0.7 x 10”MW,. Preliminary electrical power-cost goals for an osmotic salination design are -200 mills/kWh, for salination by seawater’.3 and -5 mills/kWh, for salination by Dead Sea brine.’ Direct conversion of salinity power to electricity may be accomplished by a dialytic battery, which consists of an array of alternating anion and cation exchange membranes. The operation of a dialytic battery is essentially the reverse of conventional electrodialysis desalination processes. For advanced ion exchange membranes, outputs of 1.7 W/m’ for salination by seawater and costs of -$1/m* may be attainable. Thus, the capital cost of the membranes would amount to $59O/kW,, which for a IO-yr lifetime and a plant factor of 90% converts to an energy cost of - 10 mills/kWh,. The cost estimates of Loeb3 and Weinstein and Leitz* should warrant further assessments of the potential of electrical-power generation from salinity differences. REFERENCES I. R. S. NORMAN, Science 186, 350-352 (1974). 2. J. N. Weinstein and F. B. Leitz, Science 191, 557-559 (1976). 3. S. LOEB, Science 189, 654-655 (1975).
Energy Center, UCSD La Jolla, CA 92093, U.S.A. Energy use in India
Roger Revelle in “Energy use in rural India” [Science 192,%9-975 (1976)]has indicated that actual per capita energy consumption in India is about 3 times larger than is normally estimated. The reason for this large discrepancy is that people in rural areas of poor countries tend to make relatively heavy use of wood, dried cow dung, plant refuse, and of animal and human work, which are not included in estimates of commercial energy consumption. Daily per capita energy consumption in India from all sources corresponds to (1.46 x 10’/365) Btu = 6.87 x lo-’ bbl, or about 4.3% of current U.S. consumption. Roughly one third of the food energy intake of the entire Indian rural population is expended on manual labor. About 5 1.5% of 500 x IO9hours per year of human labor are spent on agriculture, domestic activities consume 39.5%, and all other occupations together about 9%. According to Revelle, energy consumption in rural India should be more than tripled at a cost of about $3.2 x lo’, which could be paid for by exporting about 10% of increased food grain and would yield refuse with a potential energy content of about 2.8 times the additional energy required. Proper utilization of the energy contents of this heavy refuse production remains as a technological challenge. S.S.P.
335