| Local Experience With Micro-Hydro Technology |
|C. Small hydropower in the rural situation|
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.
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.
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.
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.