Hydropower's Role in Delivering Sustainability
Authors: Altinbilek Dogan , Seelos Karin , Taylor Richard 
Published: October 2005

Johannesburg's World Summit on Sustainable Development stipulated in its Implementation Plan that hydropower of all scales should be included in the drive to increase the contribution of renewable energy. This can be achieved through the plant-life extension and upgrading of existing schemes, as well as by the sustainable development of new projects according to the needs, opportunities and resources available.

Hydropower is the world's largest source of renewable energy used for power generation; it accounts for 19 percent of the world's supply (by 2010 wind power is expected to contribute 0.6 percent and solar power 0.12 percent1. Hydropower is also a truly global resource, as more than 150 countries generate hydroelectric power. There is about 730 GW of hydro capacity in operation worldwide, generating 2650 TWh/year. A further 101 GW is under construction and 338 GW is at the planning stage2.

Hydropower plays an important role in reducing global GHG emissions by an estimated 10 percent per annum; in its current role, hydropower offsets 4.4 million barrels of oil-equivalent3 (thermal electric generation) each day. There is vast unexploited potential worldwide for new hydro plants, with only 33 percent of the economic potential having been developed so far. The majority of the remaining potential exists in lesser developed countries in Asia, South America and Africa. For example, Europe has developed 75 percent of its economic potential, whereas Africa has only developed seven percent.

Hydropower technologies are reliable, advanced and efficient. The energy conversion efficiency of 80 to 93 percent is far higher than that for other major types of power plant. The level of service from the various types of hydro scheme varies from base-load supply, typically from run-of-river schemes, to peak-load and system-back-up services from hydro storage schemes. In regions where there is long-developed hydro capacity, plant-life extension can be achieved by the replacement of equipment within existing infrastructure; this can extend the operating life by a further 30 to 50 years.

Small-scale, decentralised development has been responsible for bringing light and power to remote communities. Such schemes have catalysed local commercial diversification and prosperity. The lower investment demand of smaller schemes has enabled private sector involvement through independent power production. Typically smaller schemes become grid connected if the power system is accessible, as this increases the security of supply. Furthermore, schemes at remote sites can assist transmission system stability. A further important role of smaller scale hydro is the recovery of energy at water infrastructure developed for other purposes.

In many countries, large schemes play a significant role in national and regional supply security due to the flexibility of storage reservoirs and independence from fuel price fluctuations. Hydro also integrates well with other generation technologies, with its flexibility enabling thermal plants to operate steadily (saving fuel and reducing emissions). In addition, its responsiveness permits the back-up of the intermittent renewables.

The question of storage is clearly a major issue in balancing supply and demand. Hydro reservoirs and pumped-storage schemes offer security in the stability and reliability of power systems; they can absorb power when there is an excess and follow load demand instantaneously. A major challenge is that ‘support’ and ‘storage’ services are rarely understood and encouraged in the market-driven arena.

The main arguments against hydropower concern its social impacts, such as land transformation, displacement of people, and environmental changes, i.e. fauna, flora, sedimentation and water quality. The social and environmental impacts can, however, be mitigated by taking appropriate steps according to established codes of good practice. As a tool for this purpose, the hydropower sector has recently developed and adopted Sustainability Guidelines. These Guidelines are currently being tested by a number of governments and international organisations.