Hydroelectric power is relatively small as a contributor to primary energy, but it assumes a great deal more importance in electricity supply and generation. It is also estimated that only a fraction of the world’s global hydropower potential has been exploited, although costs, availability of financing and environmental concerns may curtail the technical and economic potential of resources, particularly in developing countries.
A large percentage of hydropower potential has already been developed in North America and Europe. As in the developing countries, public opposition to large hydro schemes will probably result in very little new development of big dams and reservoirs.
The development of distributed generation will offer opportunities for development of small scale hydro plants. There is already a large amount of small hydro in the industrial countries and small scale and low head hydro capacity will probably increase in the future as research on low head turbines and standardised turbine production lowers the costs. New computerised control systems and improved turbines may allow more electricity to be generated from existing facilities in the future. Many small hydroelectric sites were abandoned in the 1950s and 60s when the price of oil and coal was very low and the environmental impacts of fossil fuels were unrealised. Increased fuel prices in the future could result in these facilities being refurbished.
Hydro power is classified as a renewable form of energy. Renewables constitute 7.6% of global primary energy supply, excluding electricity trade. Biomass is the most significant renewable primary energy source, accounting for 4.4% of the total, with hydro power second but considerably smaller at 2.1%