Energy and the New Reality, Volume 2: C-Free Energy Supply Chapter 6: Hydro-electric power L. D. Danny Harvey This material is intended for use in lectures, presentations and as handouts to students, and is provided in Powerpoint format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see for contact details. Publisher: Earthscan, UK Homepage:

Kinds of hydro-power Run-of-the-river (no reservoirs) Reservoir-based

Power production: Mechanical power of flowing water is equal to P e = ρg Q H where H is the “head” and Q the volumetric rate of flow Electric power produced is equal to P e = η e η t ρg Q H where η e and η t are the generator electrical and turbine mechanical efficiencies, respectively

Figure 6.1a Low-head hydro-electric system Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, )

Figure 6.1b Medium-heat hydro-electric system Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, )

Figure 6.1c High-head hydro-electric system Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, )

Figure 6.2 Impellors Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, )

Figure 6.3 Impellor Space Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, )

Figure 6.4 Hydro Efficiency Source: Paish (2002, Renewable and Sustainable Energy Reviews 6, 537–556,

Figure 6.5 Hydro-electricity generation

Current hydro-electricity About 19% of global electrical generating capacity in 2005 (778 GW out of 4100 GW) About 16% of global electricity generation in 2005 (2838 TWh out of TWh)

Figure 6.6 Top 10 countries and rest-of-world in terms of hydro-electric power capacity in Total = 778 GW

Figure 6.7 Top 10 countries and rest-of-world in terms of hydro-electric generation in Total = 2838 TWh.

Figure 6.8 Percent of total electricity generation as hydro-electricity

Total small-hydro (< 10 MW)

Figure 6.9 Hydro-electric generation potential

Hydro-electric generation potentials Table 6.1 Potential energy generation (TWh/yr), existing (2005) of future generation (TWh/yr), total electricity demand (TWh) in 2005, and percent of total electricity demand met by hydro power in various continents and selected countries (listed for each continent in order of decreasing technical potential). UC=under construction. Source: WEC (2007) for hydro generation, UN (2007) for total generation.

Figure 6.10a Hydro reservoir power densities

Greenhouse gas emissions Methane is produced from the decomposition of organic matter already on the land when it is flooded to produce a reservoir (this emission decreases over time) Methane is also produced from decomposition of organic matter that washes into the reservoir and decays anaerobically For some projects, the GHG emission per kWh, averaged over the lifetime of the projected, is greater than that from a coal-fired powerplant! Accurate assessment of the GHG emissions is, however, very difficult

Figure 6.10b GHG emissions from dams in Brazil (except for “Boreal”)

Figure 6.11a GHG emissions vs power density for reservoirs in Brazil

Figure 6.11b GHG emissions vs power density for reservoirs in Quebec

Capital cost of hydro powerplants Small hydro, $ /kW, developing countries Small hydro, $ /kW, developed countries Large hydro (involving dams and reservoirs), $ /kW (including access roads for high estimates)

Figure 6.12 Small-hydro capital cost Source: Paish (2002, Renewable and Sustainable Energy Reviews 6, 537–556,

Cost of hydro-electricity (cents/kWh) Table 6.4 Cost of hydro-electric energy (cents/kWh) for various capital costs, interest rates, and capacity factors, assuming amortization of the initial investment over a 50-year period. Operation and maintenance, insurance, water rent, transmission, and administrative costs are not included.