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Small Hydropower Fact Sheet

Background

Water has been used for energy purposes for thousands of years. It has been used for motive energy in many parts of the world for at least two thousand years, primarily for grain milling. Water mills were constructed all over Europe and North America during the first decades of the Industrial Revolution to provide motive (shaft) power for a variety of uses, from flax processing to textile spinning and weaving, from timber milling to wood working.

All hydropower energy was produced from small hydro schemes (i.e., less than 10 MW) until the beginning of the 20th Century. In fact, almost all hydropower schemes until the late 19th Century were mini (less than 1 MW) or micro (less than 100 kW). Thousands of towns and cities in the world are located around these early small hydropower sites showing the heyday of hydropower in the 18th Century. Hydropower was eclipsed in the late-18th Century for nearly one hundred years by the discovery of coal. Coal quickly became the primary energy source for most of the 19th Century, and many hydropower sites were either abandoned or neglected.

However, hydropower witnessed another renaissance with the discovery of electricity in the latter part of the 19th Century. Hydropower was the first major source for generating electricity, until coal, oil and later nuclear, became more prominent. Still, hydropower accounts for nearly 10% of the world's commercial energy, and accounts for over 90% of the electricity generated in such countries as Norway, Austria and Kenya.

Initially, hydroelectric plants were small or micro hydro sites. However, the industrial and domestic demands called for the construction of ever larger dams and hydropower schemes until by the end of the first half of the 20th Century, small hydropower was once again in severe decline. This decline was accelerated with the advent of cheap petroleum products in the post-World War II era. These two factors (large hydro and cheap petroleum) nearly spelled the end for small-scale hydropower by the 1950s. Thousands of small hydro-electric plants were abandoned in Europe, Asia and North America during from the 1950s to the early-1980s. Small hydropower plants virtually ceased to exist in the Former Soviet Union (FSU) and Central and Eastern Europe (CEE).

However, since 1989 there has been yet another renaissance of small hydropower in Europe. This has been particularly pronounced in CEE, as the economics of production have improved, and as concerns for reducing environmental emissions have increased. Since 1989 over 2000 small hydro-electric plants have been renovated in Europe, while another 1000 new plants have been constructed.

Resource Potential

About 680 GW of hydropower has been developed globally, 47 GW of which is small hydropower (<10 MW/site). The remaining non utilised global hydropower potential is estimated at 3,000GW, 180 GW of which is at small hydro sites. 70% of this small hydro potential (126 GW) is in developing countries.

Table 2: Estimates of Small Hydro Capacity and Production by Region (1995)

Region

Capacity (MWe)

Production (GWh)

North America

4,400

18,000

Latin America

1,000

3,500

Western Europe

9,740

40,000

CEE and FSU

2,070

8,500

Mid East and Mediterranean

180

700

Africa

400

1,600

Pacific

160

700

Asia

10,000

42,000

Total

27,950

115,000

Sources: International Water Power and Dam Construction Handbook (1996) Hydropower and Dams: World Atlas (1997)

 The World Energy Council estimates that, under current policies, installed capacity of small hydro will increase to 51 GW by 2020, with the largest increase coming in China. Under the WEC's favourable case scenario, installed capacity increases to about 75 GW by 2020. All regions of the world are experiencing significant increases in small hydro capacity, with China again showing the largest increase.

Table 2: Estimated Deployment of Small Hydro by 2010 By Region

Region

Capacity (MWe)

Production (GWh)

North America

5,500

25,000

Latin America

3,000

10,000

Western Europe

12,600

50,000

CEE and FSU

7,000

28,000

Mid East and Mediterranean

400

1,700

Africa

700

3,000

Pacific

750

3,000

Asia

25,000

100,000

Total

54,950

220,700

Sources: International Water Power and Dam Construction Handbook (1996) Hydropower and Dams: World Atlas (1997)

Of the estimated 130 hydropower turbine manufacturers in 1995, over 100 produce turbines and machinery only for small hydropower plant. Production is concentrated in Europe, North America and Japan, although there are important producers in China and India. Micro-hydro producers are found all over the world, and new advances in this small-scale technology show the vitality of the industry.

Technologies

Small hydropower technologies can range from the simple and inexpensive, to the complicated and expensive. They can be constructed on:

Run-of-river schemes tend to be most expensive, as they involve the construction of weir to catch water from a fast-flowing stream or river. The water is then diverted down a shaft, or "penstock" into the turbine. The turbine turns a generator, that, in turn, generates electricity. Conversely, the turbine can turn a shaft for simple mechanical power or a combination of mechanical and electric power generation. Canal systems tend to be less expensive, as access and some infrastructure are already in place. Nonetheless, the system is relatively similar to that of run-of-river systems. Costs per kilowatt installed can vary widely, but, if all civil works must be constructed for a hydro-electric small hydro system, prices per kilowatt range between US$ 750 and US$ 4,000, and can be higher or lower depending upon difficulty of access, size of system, among other factors.

Micro (and even "pico", for less than 10kW) and mini-hydropower systems are being built all over the world. Nepal has one of the most successful micro-hydropower programmes in the world. Considerable assistance has been provided to setting up, initially, micro-hydropower systems for mechanical power, primarily using "cross-flow" low-head turbines, with assistance from the Swiss and UK development agencies . Since 1980, hundreds of such schemes have been built. Since the early 1990s many of these systems have been converted to generate electricity. Similar success stories can be found in India, Sri Lanka and Peru in the developing world. China has installed thousands of small hydropower systems since the 1960s.

The least expensive small hydro systems are those that utilise pipe systems, generally systems carrying drinking or irrigation water from mountainous areas. These systems are inexpensive because they merely require the placing of a turbine on the pipe. Turbines can be standard (Peltons, Francis, etc.) or they can even comprise a pump put into reverse flow (the cheapest option of all). Such systems are being developed rapidly all over Central and Eastern Europe where over 1 GW of such systems have been installed since 1991.

Off-Grid Applications

Small hydro offers a number of possibilities for off-grid applications, as has been demonstrated vividly in Nepal and other parts of the developing world. However, applications are, by definition, limited to sites or areas where there is water. Construction and installation costs can be high, but maintenance is very low. Furthermore, small hydro schemes have very long lifetimes, as the thousands of systems rehabilitated over the past decade in Europe and North America amply demonstrate. New improvements in technology are widening the scope for small hydropower, particularly for mini-, micro- and pico-hydro applications.

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