Emerging Technologies to Benefit Farmers in Sub-Saharan Africa and South Asia (2009) / Chapter Skim
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7 Emerging Technologies to Meet Local Energy Needs
7 Emerging Technologies to Meet Local Energy Needs
Pages 211-232
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This chapter examines a number of energy technologies that might be developed to lessen or remove the current reliance on expensive petroleumbased sources of portable energy, such as kerosene and diesel. Energy 211
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Even with ample rainfall, hydroelectric generating capacity is often inadequate; with low water levels in lakes and an increasing silting problem in storage structures, more expensive diesel generation is needed for peakdemand management, and blackouts are common. Most countries in SSA and SA have plans to expand power-generation capacity, and a widely recognized high priority is the development of longrange technical planning for these regions to replace the day-to-day crisis management that is the current mode of many energy ministers.
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. Status of Large-Scale Renewable Energy Projects Among the types of renewable energy options that exist or are being explored for national and regional grid systems in SSA and SA are geothermal power, hydropower, wind power, and wave and tidal power.
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Geothermal Power Geothermal power plants use steam or hot water from geothermal reservoirs to turn turbines. Geothermal energy is the only clean source that can provide firm, predictable power on 24 hours per day, and it is in much greater amounts for a given installation than other renewable sources (Brown and Garnish, 2004)
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Because small-scale hydropower typically does not interfere with river flow, they offer an environmentally benign way to replace diesel generators and to provide energy to rural populations up to a mile from the generator. Microscale hydropower does not provide storage capacity and is vulnerable to supply variations.
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Energy Solar cookers collect heat from sunlight and provide energy for boiling and cooking, reducing the use of firewood and the pollution associated with burning of wood. They typically consist of a small number of reflectors (or a parabolic mirror)
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. Solar heat can produce electricity if parabolic troughs are used to focus solar radiation on the heating chamber of a Stirling engine (Box 7-1 and Figure 7-1)
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One way to overcome that limitation is to concentrate the solar energy with mirrors, Fresnel lenses, and other devices that are typically placed above the solar cells. The benefit is increased conversion efficiency; as a result, less silicon (which is expensive and of limited availability)
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Second, energy storage has a role in maximizing the benefits of off-grid solar, hydro, and wind power, which are inherently intermittent. If excess power generated when operating conditions are favorable could be stored, energy would be available when operating conditions reduce generating capacity.
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As interest in renewable energy sources has grown, so have ways to increase their efficiency with energy storage. Batteries store electricity in the form of chemical energy.
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The question for all of them is whether they can be developed into applications that meet the needs of small-scale farmers and rural communities. If they are to do that, the potential spectrum of the applications needs to be defined first -- from rechargeable hand tools and small-farm equipment or vehicles to energy storage for the village-scale wind turbine.
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. Hydrogen can also be produced by direct electrolysis of water; this process could be used to produce hydrogen virtually anywhere from renewable energy: solar power in the deserts, wind power, hydropower, or geothermal energy (Everett and Boyle, 2004)
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Plant cell walls consist of cellulose and hemicellulose fibrils intertwined with complex lignin molecules. During plant development, the chemical composition of cell walls varies from tissue to tissue within a species.
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Therefore, the plant breeder needs to improve traits that affect the chemical composition of energy crops to be commensurate with downstream processing technologies. If the biomass is to be digested in an enzymatic process, it is desirable to breed for cell wall lignocellulose structures that are easily degraded by digestive enzymes.
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, and this is toxicologically unacceptable. Castor bean (Ricinus communis)
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. By creating transgenic varieties of Jatropha curcas and Ricinus communis that are non-toxic to humans and animals, these transgenic varieties would be safe for humans and the environment and could be valuable for biofuels and animal feed.
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. Photosynthetic Microbes: Algae and Cyanobacteria In the 1980s and 1990s, DOE's Aquatic Species Program explored the potential use of algae to make liquid fuels and decided that it was impractical because the growth of algae in open ponds was ruined by contamination from local microorganisms and the alternative, a closed bioreactor system, was too expensive to build and operate.
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Closed bioreactors provide additional benefits, including physical containment and exclusion of microorganisms, convenient delivery of concentrated CO2 to accelerate algal growth, facilitated harvest of biofuels from the organisms, the ability to reuse and recirculate water in the production system, and scalable modularity to support both large-scale and small-scale systems. To provide a controlled source of CO2 for the plants, a bioreactor would be ideally constructed as an adjunct to a power plant, brewery, or other CO2emitting facility.
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Pp. 384-439 in Renewable Energy: Power for a Sustainable Future, 2nd edition, G
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2008. Energy Efficiency and Renewable Energy Program: Distributed Wind Energy Technology.
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2007. Flexible energy storage devices based on nano composite paper.
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National Renewable Energy Laboratory. Available online at http://www.nrel.gov/docs/legosti/fy98/24190.pdf [ac cessed March 21, 2008]
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