PSE 104 Section 2: Lecture 9 1
X.X. Hydroelectric PowerHydroelectric PowerA. Overview Indirect solar power: rainfall at elevation Largest form of renewable energy in world –
over 90% of renewable electricity Hydro not “renewable energy”?
Virtually 100% of hydro power is for electricity generation
16% of global electricity supply in 2002
PSE 104 Section 2: Lecture 9 2
VIII.VIII. Energy from BiomassEnergy from Biomass
PSE 104 Section 2: Lecture 9 3
X.X. Hydroelectric PowerHydroelectric PowerA. Overview Indirect solar power: rainfall at elevation Largest form of renewable energy in world –
over 90% of renewables Hydro not “renewable energy”?
Virtually 100% of hydro power is for electricity generation
16% of global electricity supply in 2002
PSE 104 Section 2: Lecture 9 4
X.X. Hydroelectric PowerHydroelectric PowerB. History First ‘hydro power’ for pumping water and
milling grain (similar to wind energy) – mechanical power
Waterwheel power used for shaft work: papermills, textiles mills, etc.
Rittenhouse papermill, Germantown, PA 1690
PSE 104 Section 2: Lecture 9 5
X.X. Hydroelectric PowerHydroelectric Power
Waterwheels
PSE 104 Section 2: Lecture 9 6
X.X. Hydroelectric PowerHydroelectric Power
B. History First known use of hydro for electricity: 1881
in UK -waterwheel power on river River Wey Very fast growth into 20th century: public
power and power grid established Recognized that hydro was tremendous
resource for electricity generation Key to growth: availability of hydraulic turbine Fourneyron (UK): outward flow turbine
80% efficiency Francis (USA): inward flow turbine
PSE 104 Section 2: Lecture 9 7
X.X. Hydroelectric PowerHydroelectric Power
Fourneyron turbine
PSE 104 Section 2: Lecture 9 8
X.X. Hydroelectric PowerHydroelectric Power
Francis turbine
PSE 104 Section 2: Lecture 9 9
X.X. Hydroelectric PowerHydroelectric Power
C. Hydro Power Fundamentals Based on potential energy (pe) due to elevation and
effect of gravity For hydro power, need source of flowing water pe = (mass water)(height)(gravity) = MgH (kg)(m/sec2)(m) = (kg–m)(m) = (Newton)(m) = 1
Joulesec2
Power must be a function of volume flow of water (Q)
Q = m3/sec Power (P) = Energy per unit time P = (ρ)(Q)(g)(H) = (kg/m3)(m3/sec)(m/sec2)(m)
= N-m/sec = Joules/sec = watts
PSE 104 Section 2: Lecture 9 10
X.X. Hydroelectric PowerHydroelectric Power
C. Hydro Power Fundamentals For water where ρ= 1000 kg/m3 ,
P = (1000)(Q)(H) Efficiency (η) = electrical output < 100%mechanical input
Efficiency = 75% – +95% for hydroelectric turbines
Effective Power using water = (η)(1000)(Q)(H) = W
Power in kW = (η)(10)(Q)(H)
PSE 104 Section 2: Lecture 9 11
X.X. Hydroelectric PowerHydroelectric Power
C. Hydro Power Fundamentals Available Head = usable height of water in
reservoir Related to pressure energy of stored water =
(ρ)(g)(H) Presure = Force per unit area, i.e. lb/in2 = psi (ρ)(g)(H)= (kg/m3) (m/sec2)(m) = N/m2
Turbine types and efficiencies vary with head
PSE 104 Section 2: Lecture 9 12
X.X. Hydroelectric PowerHydroelectric Power
C. Hydro Power Fundamentals
PSE 104 Section 2: Lecture 9 13
X.X. Hydroelectric PowerHydroelectric Power
C. Hydro Power Fundamentals “High Head” dam: high usable potential energy
Does not necessarily need high water flowrates (Q) for sufficient power generation
High pressures at outflow requires high construction costs
“Low Head” dam: low usable potential energy Must have high water flowrates for reasonable power
generation Difference between tidal barrage and low head
dam:variable water head in tidal barrage
Causes periodic power “spikes” as opposed to continuous power generation
