| Local Experience With Micro-Hydro Technology |
a) Liquid Fuel from Biomass
b) Gaseous Fuel from Biomass
c) Direct use of Sun and Windpower
d) Water-Power Resources
Energy problems are manifold indeed, and a unique solution - consisting of a variable mix of resources and technologies for each case - seems to be called for. There is scope for improving the balance of rural ecosystems through conservation, reforestation and effective wood lot management, and the use of traditional energy may be enhanced with better devices such as more efficient cooking-stoves and charcoal-kilns. Various new technologies have emerged in the past that can meet a number of needs and it is perhaps worthwhile to give a short summary of the state of the art of the major possibilities:
a) Liquid fuel from biomass:
The conversion of biomass to liquid fuel is not new. It was used during the Second World-War as a substitute for scarce fuel. It holds considerable promise for application in the developing countries. The production of alcohol, particularly ethanol (ethyl-alcohol), from certain types of biomass, is a commercially well established technology. Ethanol is produced by fermentation and distillation of carbohydrate materials such as sugar cane, sugar beet, molasses and cassava. It can be used to power vehicles either by itself or blended with petrol. Within limits, ethanol can substitute for an equal volume of petrol with only minor engine modifications. It could thus help to reduce the consumption of petroleum in the transport sector. Methyl alcohol, produced from wood, is more difficult to use as a vehicle fuel, and does not hold promise for the near future.
The economics of alcohol production are not very well established and depend greatly on the cost of biomass material. R + D is being done to improve the efficiency of production and to reduce costs, but it is still too early to assess the prospects for a breakthrough. The biggest constraint of using biomass-derived alcohol on a large scale is the direct competition with food production for arable land. Great care must be taken not to upset an already precarious balance.
b) Gaseous fuel from biomass:
Biogas, a mixture containing 55 -65 % methane (CH4) can be produced from the anaerobic (in the absence of oxygen) decomposition of animal, plant and human wastes. It can be used directly in cooking, reducing the demand for firewood. Also, combustion engines may be run on biogas with little adaptation of the engine only. Moreover, the material from which biogas is produced retains its value as a fertilizer and can be returned to the soil. Millions of small plants exist worldwide (China, India, South Korea, Nepal). Their operation has met with varying levels of success. In cold climates, prospects for the application are reduced since economics are best in the temperature range 25 -35° C. The poorer part of a population often has no access to the necessary feedstock. Although there is a big potential in aquatic weeds (water hyacinth) and other vegetable waste, its use as a "free" feedstock is not developed to any extent. More research and funds are required to make biogas a viable alternative in many more situations.
Partial combustion of wood or materials such as straw, nutshells, bark or rice hulls, produces a gaseous mixture (wood-gas, producer-gas) with a low calorific value. It can be burned for thermal energy applications, or if filtered, for use in combustion engines. The production and use of both biogas and producer gas could be viable much more widely in rural areas, given funds for research and development, incentives for experimentation and effective dissemination mechanisms.
c) Direct use of sun and windpower
Solar and windpower technologies are a third source of renewable energy for developing countries. A firm technical basis exists for windpower projects. Particularly water pumping is a simple and effective technology for rural areas. Machines that produce electricity are highly optimised for small outputs (up to 5 kW) and may be the best alternative for remote and isolated small consumers. Windpower tends to be an erratic resource and care must be taken to assess the wind regime properly and to choose a suitable machine that has been designed for the kind of existing wind regime.
Water heating by flat plate collectors is the solar technology most ready technically, economically and commercially - for widespread application. Some developing countries have begun to manufacture their own solar water heaters and many others could do so. Solar water heaters are often an economical source of hot water for domestic and industrial purposes. Solar dryers that basically heat air, can provide heat for drying crops in agriculture and are already in use in a number of countries.
Photovoltaic cells, which convert solar energy directly into electricity, appear well suited to many applications in developing countries because they promise long life and trouble-free operation. Solar electricity is still at price levels on the order of $ 2 per kWh. Costs of photovoltaic cells are falling but it is still difficult to say when the big cost breakthrough will happen. For its high costs it has good prospects only in applications where relatively low power needs exist in remote locations. The use of photovoltaic electricity for water pumping (drinking water, irrigation) appears -at prices of early 1981 - to be viable only where no other alternative exists.
d) Water power resources:
For many developing countries, unused water power resources constitute a very considerable potential. The technology is well developed and plays an important role worldwide. Geographically it is limited to suitable sites along rivers and other sources of flowing water.
"The historical approach to energy planning stresses the expansion of conventional energy sources and, generally, large-scale centralised systems. Thus, many countries face the problem of unequal internal growth, and also, a disintegration of the rural and non-commercial sectors." On the other hand, small potentials may be a very useful resource mainly in the field of providing motive power to stationary users -either direct or through electricity - and lighting. Considerable recent experience exists from a number of developing countries. The rest of this paper is devoted to this and to the elaboration of a practicable approach to harness water power on a small scale (in relation to installation size), but widely applied wherever potential exists and where it appears to be a viable or often superior alternative to other energy sources.