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close this book Local Experience With Micro-Hydro Technology
close this folder C. Small hydropower in the rural situation
View the document 1. PAST AND RECENT HISTORY


With the exception of China and a relatively small number of higher developed countries, the degree of rural electrification is far from satisfactory. It is difficult to find reliable data of individual countries but there is no doubt that the percentage of people who have electricity supply facilities varies widely within a given area. Numbers in fig. 7 are supra-regional estimates only and point out regional differences and the magnitude of populations concerned.

Generally speaking, there have been two approaches that were followed in rural electrification programs, namely extensions from grid systems, and to a lesser extent autogeneration, e.g. installation of isolated supply systems, typically with diesel sets. Problems with grid-extensions have been touched on in chapter B. The circumstance of high costs for transmission lines combined with a small demand and resulting low financial returns, and the fact that, in expansive countries, not even an extensive grid-system is likely to connect the majority of the population, make this approach limited in scope.

It was for these reasons that the second approach -autogeneration -was chosen in many instances. If such generation is based on oil-fuelled plants, it is obvious that operation costs are seriously affected by the ten-fold increase in costs of oil of the recent past. While many existing plants try to cope with costs somehow, and continue operation, further extensions of rural electrification in this manner have come to an almost total halt.

Fig. 7: Extent of Rural Electrification, by Selected Region

Source: Estimate based on: World Sank, Rural Electrification, Washington 1975

A third approach of more recent origin is electricity generation through the conversion of biomass, either by direct combustion and generation of steam used in steam engines or turbines, or by way of intermediary products such as biogas or woodgas, used in adapted internal combustion engines. The first option is technically mature but has perhaps limited scope in the long-term future due to generally very low conversion efficiencies. Technology involved for the second option is in the pilot stage of development, right now obtainable not without difficulty, and at still relatively high cost. Nevertheless, prospects for the future bear promise at least from the technical point of view. From the standpoint of ecology and the environment, serious constraints exist. If wood is used for power generation, this is in direct competition to needs of fuel for cooking, and the danger exists for accelerated depletion of forests, if it is not accompanied by afforestation and wood lot management programs. Growing energy crops on the other hand, for the generation of biogas (or ethanol, which is not discussed here), competes with food crops and must be subject to an optimum land-use planning.

This constraint naturally does not apply if dung, agricultural wastes and "useless" materials such as water hyacinths are used. Depending on livestock holdings and a favourable climate for vegetation growth, such "raw materials" for conversion into useful energy may be considerable. Reddy states in his article; "The design of rural energy centres", that: "... a biogas plant using cattle manure of the entire village can provide a surplus of 11 m³/day of biogas, after meeting all the cooking energy needs of all the households in the village." This statement -made in connection with the study and the optimisation of a specific situation -is perhaps over-optimistic but may serve here to show the importance of biomass-energy in the rural context.

Another point is this: Caloric fuels such as wood and biogas are relatively lowgrade energies which can produce medium temperatures only (as compared to mechanical or electrical energy which corresponds to infinite temperatures). Such fuels are best used for thermal applications such as cooking, e.g. direct combustion. The thermodynamic principles applying in the conversion into mechanical power severely limit the efficiency which can be achieved. The theoretical limiting efficiency is given by the law of Carnot , which applies for all processes converting heat into work.

Conversely, electricity, which is a high grade energy, is best used for high grade applications such as motive power for productive uses and lighting. If used for low grade thermal applications, electricity becomes relatively inefficient and such uses must be the exception rather than the rule: As a matter of fact, in rural areas already "electrified", the use of electricity is, very broadly speaking, limited to lighting and motor drive. In the Indian village studied by Reddy, only 1 % of all energy used is contributed by electricity. Thus, the consumption is small in absolute terms (e.g. 30 kWh/day for a population of 360). What this amount of energy can achieve on the other hand, is considerable: It pumps water for the irrigation of 4 to 8 hectares of land (depending on pumping height and crops grown), substitutes for about 1000 1 of kerosene that would be required for lighting per year, and runs a small flourmill occasionaly. Such uses have the potential to improve the life of the people served by much more than would be expected from such a small electricity input.

A study and descriptive analysis of the energy situation of six villages on different continents shows no different picture and is corroborated also by various sources from other countries. In conclusion, it is possible to state that if such minimal needs for high grade energy can be met with a local hydropower potential, the resulting station will be modest in size but can have a substantial impact.

For a first approximation, a total energy requirement of 600 kgce/cy (kgce/cy = kilogram coal equivalent per capita per year) - which is substantially above subsistence level, particularly if efficiently used may be applied. With scope for growth, 2 % of the total requirement may be provided in the form of high-grade energy, resulting in an installed capacity of approx. 25 W/capita

(calculation: 600 · 8 kwh/kgce 0,02 = 96 kWh/capita, year 96/8760h/0,4 load factor = 27 W/capita)

This permits basic improvements of the living standards and, depending on the situation, agricultural development of a rudimentary nature. Subsequently, any existing productive power use may be added to arrive at the necessary station capacity. Such a procedure should of course be subjected to much refinement by analysing the given situation and its scope for development in detail.

The approach discussed here is one of supplying high grade energy for basic needs with scope for growth, small stations for initially small demands but multiplied on a large scale, to bring about rural development at a sustained rate. Community development, along with the gaining of experience in executing and operating small projects, and the local development of know-how and skill, would then be the basis for bigger scale developments, diversification of energy use, and more comprehensive, perhaps national, energy planning.