http://www.sciencedaily.com/releases/2010/01/100104151923.htmSolar-Powered Irrigation Significantly Improves Diet and Income in Rural Sub-Saharan Africa
ScienceDaily (Jan. 5, 2010) — Solar-powered drip irrigation systems significantly enhance household incomes and nutritional intake of villagers in arid sub-Saharan Africa, according to a new Stanford University study published in the Proceedings of the National Academy of Sciences (PNAS). The two-year study found that solar-powered pumps installed in remote villages in the West African nation of Benin were a cost-effective way of delivering much-needed irrigation water, particularly during the long dry season.
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Striking results
The results were striking. The three solar-powered irrigation systems supplied on average 1.9 metric tons of produce per month, including tomatoes, okra, peppers, eggplants, carrots and other greens, the authors found. Woman who used solar-powered irrigation became strong net producers in vegetables with extra income earned from sales -- significantly increasing their purchases of staples and protein during the dry season, and oil during the rainy season. During the first year of operation, the women farmers kept an average of 18 percent by weight -- 8.8 kilograms (19.4 pounds) per month -- of the produce grown with the solar-powered systems for home consumption and sold the rest in local markets.
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Nutrition and sustainability
In terms of nutrition, vegetable intake across all villages increased by about 150 grams per person per day during the rainy season. But in villages irrigated with solar-powered systems, the increase was 500 to 750 grams per person per day, which is equivalent to 3 to 5 servings of vegetables per day -- the same as the U.S. Department of Agriculture's Recommended Daily Allowance for vegetables -- and most of this change took place in the dry season.
The research team also concluded that, despite higher up-front costs, using solar power to pump water can be more economically sustainable in the long run than irrigation systems that run on liquid fuels, such as gasoline, diesel or kerosene. "When considering the energy requirements for expanded irrigation in rural Africa, photovoltaic drip irrigation systems have an additional advantage over liquid-fuel-based systems in that they provide emissions-free pumping power," they added.
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http://www.stanford.edu/group/solarbenin/results.html<snip>
Additionally, these early data suggest that the payback time of a half-hectare Solar Market Garden is 2-3 years (this estimate is closer to 2 years for a surface system, closer to 3 for a submersible system, and will be refined over the second year of operation).
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Via PG&E's blog
http://www.next100.com/2010/01/more-hope-for-the-farmers-of-a.php