Energy and the New Reality, Volume 2:
C-Free Energy Supply
Chapter 6: Hydro-electric power
L. D. Danny Harvey
harvey@geog.utoronto.ca
Publisher: Earthscan, UK
Homepage: www.earthscan.co.uk/?tabid=101808
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Kinds of hydro-power
• Run-of-the-river (no reservoirs)
• Reservoir-based
Power production:
• Mechanical power of flowing water is equal to
Pe = ρg Q H
where H is the “head” and Q the volumetric rate
of flow
• Electric power produced is equal to
Pe = ηeηt ρg Q H
where ηe and ηt are the generator electrical and
turbine mechanical efficiencies, respectively
Figure 6.1a Low-head hydro-electric system
barrage
turbine
river flow
(a) low head
Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, 183-226 )
Figure 6.1b Medium-heat hydro-electric system
reservoir
dam
turbine
penstock
(b) medium head
Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, 183-226 )
Figure 6.1c High-head hydro-electric system
high reservoir
dam
turbine
penstock
(c) high head
Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, 183-226 )
Figure 6.2 Impellors
a)
b)
c)
Fixed blades
d)
Adjustable blades (Kaplan)
Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, 183-226 )
Figure 6.3 Impellor Space
1000
500 MW
Pelton
Head (m)
100 MW
100
10 MW
1 MW
Francis
10
Crossflow
100 kW
20 kW
Propeller
3
0.2
1.0
10
100
500
Volumetric Flow Rate (m3 /s)
Source: Ramage (1996, Renewable Energy, Power for a Sustainable Future, Oxford University Press, Oxford, 183-226 )
Figure 6.4 Hydro Efficiency
100
Pelton
Crossflow
Efficiency (%)
80
60
Francis
Propeller
40
20
0
0
0.2
0.4
0.6
0.8
Flow as a Proportion of Design Flow
Source: Paish (2002, Renewable and Sustainable Energy Reviews 6, 537–556,
http://www.sciencedirect.com/science/journal/13640321)
1.0
Figure 6.5 Hydro-electricity generation
3500
Asia Pacific
TWh/yr Electricity Generation
3000
2500
Middle East & Africa
FSU
Europe
S & C America
North America
2000
1500
1000
500
0
1965
1970
1975
1980
1985
Year
1990
1995
2000
2005
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 18000 TWh)
Figure 6.6 Top 10 countries and rest-of-world in terms of
hydro-electric power capacity in 2005. Total = 778 GW
China, 100
USA, 77.4
ROW, 293.2
Canada, 72.0
Sweden, 16.1
Italy , 17.3
France, 25.5
Norway, 27.7
Brazil, 71.1
Russia, 45.7
India, 32
Figure 6.7 Top 10 countries and rest-of-world in terms of
hydro-electric generation in 2005. Total = 2838 TWh.
Canada, 359.0
ROW, 931.0
Brazil, 338.0
China, 337.0
France, 56.0
Sweden, 72.0
Venezuela, 77.0
India, 97.0
Norway, 136.0
USA, 270.0
Russia, 165.0
Figure 6.8 Percent of total electricity generation as hydro-electricity
Norway
Brazil
Iceland
Columbia
Venezuela
Canada
Switzerland
New Zealand
Chile
Sweden
0
20
40
60
Percent Hydro Power in 2005
80
100
Total small-hydro (< 10 MW)
Figure 6.9 Hydro-electric generation potential
6000
Technical Potential
Economic Potential
Existing
Total Electricity Demand
Electricity Production (TWh/yr)
5000
4000
3000
2000
1000
0
Africa
Asia
Australasia
Europe
N&C
America
S America
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
30
Wind energy density (based on foundation
area) with 7.5 m/s mean wind speed:
about 360 W/m2
25
20
Solar energy density (based on 200 W/m 2
annual mean irradiance and 15%
sunlight-to-AC efficiency): 30 W/m2
15
10
5
Boreal
Balbina
Curua-Una
Segredo
Itaipu
Barra Bonita
Miranda
Tres Marias
Serra da Mesa
Xingo
Samuel
0
Tucurui
Annual Average MW/km2 (W/m2)
By comparison:
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”)
8.0
0.7
dos Santos
0.6
Fearnside
0.5
0.4
Coal at 45%
efficiency
0.3
0.2
Natural gas at
60% efficiency
0.1
Boreal
Balbina
Curua-Una
Segredo
Itaipu
Barra Bonita
Miranda
Tres Marias
Serra da Mesa
Xingo
Samuel
0.0
Tucurui
Equivalent CO2 Emission (kgC/kWh)
0.8
Figure 6.11a GHG emissions vs power density for reservoirs in Brazil
600
Samuel
CO2-eq Emissions (gC/kWh)
500
400
Tres Marias
300
Barra Bonita
200
Serra da Mesa
Tucurui
100
Miranda
Segredo
Itaipu
0
0
2
4
6
Annual Average Power Density (W/m2)
8
Figure 6.11b GHG emissions vs power density for reservoirs in Quebec
18
Churchill Falls
16
CO2-eq Emissions (gC/kWh)
14
La Grande Complex
12
Manic Complex
10
8
6
Churchill/Nelson
4
Sainte-Marguerite
2
0
0
2
4
6
Annual Average Power Density (W/m2)
8
Capital cost of hydro powerplants
• Small hydro, $1000-3000/kW, developing
countries
• Small hydro, $2000-9000/kW, developed
countries
• Large hydro (involving dams and
reservoirs), $2000-8000/kW (including
access roads for high estimates)
Figure 6.12 Small-hydro capital cost
10000
9000
8000
US$/kW
7000
6000
International data
5000
4000
3000
2000
1000
Developing country
0
0
500
1000
1500
kW Installed
Source: Paish (2002, Renewable and Sustainable Energy Reviews 6, 537–556,
http://www.sciencedirect.com/science/journal/13640321)
2000
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.