Abstract

Most developing countries that do not possess their own fossil fuel resources depend heavily on imports of primary energy. Since there is a parallel between energy consumption and economic development and because prices for imported energy (mainly oil) are always increasing, the yearly energy bills and consequently the balance of payment deficits of such countries are growing.

Often the very same countries that find themselves in such a worsening situation possess major natural resources in the form of water power, that have to a large extent remained untapped. Some big and medium scale hydropower schemes (a few to hundreds of MW capacity) exist in all of these countries. A small portion of the existing potential is used thus, and high grade energy in the form of electricity is produced in such installations. The large quantities of electricity produced require complex transmission and distribution networks. Bringing electricity to the consumers is therefore a costly affair and economically only possible where large load centres exist. These are usually to be found in urban areas where population density is high, thus creating a high domestic demand in a relatively small area. In addition, most large-scale and energy-intensive industries are near urban areas. This too, represents a large demand.

In rural areas, where a majority of the people in developing countries live, the population density is very often low, settlements are frequently far apart and the prevalent simple life style requires less high-grade energy per capita compared to city dwellers. Industrial energy demand is generally confined to small-scale activities such as agroprocessing and cottage industry. Thus, electricity demand per unit of area is low and the reason why supply from large generating sites -often over long distances and difficult terrain-and distribution to many low-demand consumers scattered over a large area, is not economically feasible.

The consequence of this unfavourable situation regarding electricity supply to rural areas is that a great proportion of the population of these areas has so far not benefitted from the amenities of electricity.

Up to and sometimes more than 90 % of energy consumed is in the form of biomass (wood, agro-waste etc.) which is used mainly for thermal energy requirements such as cooking and heating in households and in agro-processing (drying, curing). In absolute terms, for cooking alone, a requirement from 1000 to 4000 kWh per capita and year in conventional fuel is quoted in literature. If electricity is supposed to provide these requirements, a family of five would then need at least 8 kWh of electric energy per day. Or, for cooking alone, 584 kWh per capita and year. Compared with the 1976 consumption figures of 143 kWh/c.y. for India -which possesses large industries or of 11 kWh/c.y. for Nepal one may conclude that such a scale of development would be unrealistic.

Moreover, scientifically speaking, it is bad practice to use high grade energy such as electricity for such low-grade thermal applications as cooking. Lastly, besides high generating costs, electric cooking also involves high costs on the part of the consumer for necessary equipment (hot-plates, good quality pots + pans). In another energy sector - rural transportation - electricity is also not an economic or even practical proposition. This includes the transport of people and goods by road, agricultural draft power and river transport but excludes perhaps railways passing through rural areas and possibly ropeway systems.

The domain where small hydropower can potentially have an important impact on development is in domestic lighting and in providing stationary motive power for such diverse productive uses as water-pumping, wood and metal working, grain milling, textile fibre spinning and weaving. While much of the discussion is concerned with the generation of electricity, it must be recognised that the same source of power can perform mechanical tasks directly via gears and belt drives, very often more economically. This is illustrated by a look at the history of early industrialization in Switzerland and the role of small hydropower during that time.

In regions where no grid system for the transmission of electricity exists for the reasons explained, many oil-derivate fuelled prime movers (typically diesel engines) have been installed over the last few decades. These provide electricity for rural communities and individual plantations and farms or perhaps more often, motive power for all kinds of machinery. Operators have found it more and more difficult in recent years to maintain economics, mainly due to the sharp rises in the cost of fuel.

Small and very small hydropower schemes combine the advantages of large hydro on the one hand an decentralized power supply, as with diesel sets, on the other. They do not have many of the disadvantages, such as costly transmissions and environmental issues in the case of large hydro, and dependence on imported fuel and the need for highly skilled maintenance in the case of diesel plants. Moreover, the harnessing of small hydro-resources, being of a decentralised nature, lends itself to decentralised utilization, local implementation and management, making rural development possible mainly based on selfreliance and the use of natural, local resources.

There are in fact many thousands of small hydro plants in operation today all over the world. Modern hydraulic turbine technology is very highly developed and the hardware is highly dependable. Its development has a history of more than 150 years. Sophisticated design and manufacturing technology have evolved in industrialised countries over conventional technology the last 40 years. The aim is to achieve higher and higher conversion efficiencies, which makes sense in large schemes where 1 percent more or less may mean several MW of capacity. As far as costs are concerned, such sophisticated technology tends to be very expensive. Again, it is in the big schemes where economic viability is possible. Small installations for which the sophisticated technology of large hydro is often scaled down indiscriminately, have a much higher capital cost per unit of installed capacity, without either the advantage of economics of scale or a significant increase in capacity compared to simpler technology. For these reasons a different approach is necessary.

The prime issue of this paper is to show what can be achieved with the development of hydropower at the lower end of the scale (e.g. micro-hydro up to approx. 100 kW), which technology is relatively well developed for this purpose, and how its implementation should make the utmost use of local resources.

Emphasis is on the use of currently available know-how, using simple equipment that can be made locally, and the use of local construction materials and techniques. The aim is to reduce capital costs as far as possible. Rather than scaling down large-scale technology, this may lead to a more appropriate upgrading of local technology for larger schemes at a later stage.

Cross-Flow turbines (Michell-Banki), developed in Nepal with Swiss technical cooperation, and almost simultaneous activities with the same turbine type in other countries, are the basis of this effort at further dissemination. The state of the art of turbine and accessory design, possibilities of using ready-made components, problems encountered, and experience in planning and installation are described and documented. In addition, the basics of all parts of civil construction required are explained. For better understanding of the principles of hydraulic machines, the most important types in current use are explained and differences pointed out. Also, in order to see where the Cross-Flow turbine propagated stands in relation to output capacity and efficiency, compared to commercially-available small turbines, respective graphs are given.

At first sight there is a simple answer to the question as to where the potential may exist for developing small hydro resources: obviously in all those countries with a great deal of rain resulting in substantial runoff, and with a suitable topography (hills, mountains). In reality, however, it may prove difficult to identify sites, establish the generating potential and compare costs for the development of alternative sites. River-flow is, roughly speaking, a function of rainfall and the size of the catchment area, but evaporation, infiltration and the speed of surface runoff are other important factors. The main criterion is the river discharge and its fluctuations over a period of time. For most, if not all small rivers, discharge data over an extended period do not exist, nor are good topographical maps available for all regions of interest. Careful investigation must therefore precede all projects. In most cases there is no choice but to take a non-scientific approach whereby the risk involved should be understood. It can be shown that even under such circumstances the implementation of projects is feasible.

The existence of small metal workshops and/or a local tradition in surface water irrigation are indicators that the harnessing of water power can be initiated with mostly local technological resources.

The economics of small-scale hydropower are naturally a central issue. Of prime interest is a comparison with other sources of renewable and conventional energy and the end-use to which various energies are put. Initial investment is relatively high for hydropower compared to other resources. Capital interest and depreciation therefore result in relatively high fixed costs independent of the quantity of energy produced, making the degree of plant utilisation a critical factor. It is shown how investment cost, operation cost and plant factor interrelate to determine economic viability. In addition, social factors and others that cannot be expressed in monetary terms are briefly analysed.

The identification of measures for promoting the development and dissemination of hydropower technology is the first step towards implementation. Issues on different levels, such as policies governing the use of water licences and tariffs, institutional questions concerning the involvement of government, local authorities, cooperatives and private enterprise as well as the local community, are dealt with and examples quoted. The importance of training at all levels of manufacture, planning, construction, operation and maintenance is stressed here as an essential part of the activities. In the area of transfer of technology and specific information networks, it appears that documentation of existing know-how is necessary. In addition, international and regional information networks and specific symposia will help to coordinate development efforts, to solve common problems and to avoid duplication of mistakes.

On matters of financing different aspects again are considered: Institutional financing for fomenting local know-how and capacity in the areas of the manufacturing of equipment, surveying, the planning and construction of projects, operation and maintenance; the financing of items related to transfer of technology and information flow, training and problem-solving missions; and last but not least, the financing of individual hydropower installations or regional packages of a number of projects. Grant components, lending policies, local participation in financing, the tariff system or the structure applied, are a number of factors that affect project financing one way or the other. Individual project situations tend to be diverse, calling for specific methods of financing.