 |  | Local Experience with Micro-Hydro Technology (SKAT, 1985, 171 p.) | ||
 |  | C. Small hydropower in the rural situation | ||
|  | 1. PAST AND RECENT HISTORY | ||
| | 2. RURAL ELECTRIFICATION IN DEVELOPING COUNTRIES | ||
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a) Switzerland:
At the beginning of the 20th century, when still more than 65 % of the population lived in rural areas, small hydropower was used extensively in all parts of Switzerland. The statistics of 1914 show that the majority of installations had a size of less than 20 HP (1,36 HP = 1 kW). All stations of 1000 HP and less together, made up 99,2 % of the total number and made up 31,7 % of the total hydro capacity utilised. The average size of a station was 76 HP and by far the most served small industry, mills and other enterprises. Distribution of the stations was of course not even, but depended on the topographical and hydrological situation. Nonetheless, on average there was 1 plant on every 6 km².
Fig. 4: Hydropower Installations in
Switzerland 1914
Source: Mitteilung der Abt. f. Landeshydrographie, Berne 1914
By 1928 the picture had changed somewhat. While still 96 % of all stations were below 450 HP in output, all stations below 1000 HP together contributed about 29 % of total generating capacity. In the range up to 450 HP the average turbine (or water-wheel) size was as low as 18,8 HP, while it was 245,5 HP in stations from 450 to 999 HP. In some installations, as many as 10 individual turbine units were installed.
Fig. 5: Hydropower Installations in
Switzerland 1928
Source: Statistik der Wasserkraftanlagen der Schweiz, Berne 1928
Small plants continued to supply small and very small enterprises. As fin. 6 shows, a major portion of power was utilised right at the generation site. Generation of electricity for power transmission was secondary. Thus, costs could be kept down and the technology applied was simple and reliable. The table shows stations in different areas of the country with an exemplary (incomplete) list of successive stations along the river named.
Fig. 6: Examples of Small
HP-Stations
Source: adapted from: Statistik der Wasserkraftanlagen der Schweiz 1928
Between 1920 and 1935 imports of petroleum products rose by a factor of 5,9 while total expenditure for these products fell by more than 31 %. This was the advent of cheap oil for Switzerland. In consequence, small hydropower was of less and less importance. It had been the sole basis for industrial development in many areas and it was clearly small hydropower that made large scale developments feasible.
b) China:
The construction of small hydropower stations has been a very meaningful application of the Chinese dictum "walking on two legs" in the past 25 years. Besides the development of large resources, much emphasis was given to small-scale developments resulting in an estimated 90'000 stations dotting the vast countryside in 1979
The first large-scale campaign to establish many small waterworks started in 1956. An ambitious plan called for the construction of 1'000 small stations of a multi-purpose character, combining irrigation, flood control and power generation, in one year, reaching a total capacity of 30 MW. The campaign actually achieved far less, a mere one -fifth of stations with only 2,8 MW capacity.
The program gained momentum again in 1957 and about 350 MW were added in the following two years. Revived during the Cultural Revolution the campaign continued, and even more so after 1969. Most small stations now in operation were built after this date. Capacity in 1973 reached around 1800 MW with an average size of 36 kW per installation. Up to 1975, a further 1100 MW were added with 10'000 new stations, increasing the average size of new installations to 110 kW. In 1979, finally, the total generating capacity of all small plants was 6300 MW with 40'000 stations built in the period from 1975 to 1979, having an average size of 85 kW.
Although industrial capability permitted construction of large turbines, and the range under which small hydropower falls in China was extended to 12 MW, this indicates that construction of very small units continued. In fact, a range of miniature turbine-generators with outputs from 0,6 to 12 kW was developed, suitable for scattered mountain villages with small hydropower resources.
The development activities in this field were entirely relying on local resources -materials, skill and labour - and the results achieved are from this perspective even more impressive. Also, hydropower development in China faces some major natural obstacles. The regional distribution of resources is very uneven and concentrated in regions that are thinly populated. Flow variations in many rivers are considerable. The maximum recorded flood flow in the Huang Ho river was 88 times larger than the minimum discharge and in smaller rivers this ratio is likely to be much higher. The silt load in many rivers is enormous and has a considerable effect on the life of storage reservoirs and hydraulic equipment, making the utilisation of hydraulic resources perhaps more difficult than in many other parts of the world. Still, the results are there and might encourage emphasis on such development activities in other countries.
It is also worthwhile to look at some other aspects: As earlier stated, the trend is in most cases one of multiple use of hydro resources. Flood control, irrigation, fish breeding and even recreation are listed. Often, these other uses seem to have higher priority than power generation. Economics tend naturally to be better with such an approach ,since civil construction costs for intakes, dams, ponds and canals need not be attributed to a single activity. The specific situation in China seems to make this possible and sometimes imperative. In many other areas of the world, the potential for such a multidisciplinary approach is likely to be smaller, hut this need not necessarily reduce the scope for small hydropower development.
Guidelines governing the development of small hydropower stations in China are identical all over the country; emphasis is on local resources, low costs and short construction time. Financing is done with funds accumulated by communes or production brigades with only small amounts of subsidies provided by the state, along with assistance in design, equipment and training of operators. Labour and materials for construction are exclusively local, only minimal quantitles of cement, steel and timber are used. Even the hydroelectric equipment is made locally in small workshops.
Plans for a new hydraulic scheme originate from commune level. For the design, the county waterbureau is available for help, and decisions for stations below 500 kW are taken at county level, while bigger plants are approved by the province administration. Ownership is usually with the communes. Power use is to about 65 % in the agricultural sector for purposes such as water pumping and cereal processing. Small industry consumes 16 %, while domestic lighting amounts to less than 20 %. Cooking in rural households is mainly done with wood, coal or biogas. Tariffs applied depend on the use of energy. Water pumping is by far the cheapest, and industrial use has the highest tariff in one example while it is highest for domestic purposes in a second example. There seems to exist flexibility in fixing tariffs, depending on the local situation. The role of small-scale hydro-electricity is considerable in rural areas by any standard. In 1974 about 30 % out of 1100 counties had their electricity mainly from small stations.
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.
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