PSE 104 Section 2: Lecture 91 X.Hydroelectric Power A. A. Overview Indirect solar power: rainfall at elevation Largest form of renewable energy in world

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


VIII.VIII. Energy from BiomassEnergy from Biomass


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


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


X.X. Hydroelectric PowerHydroelectric Power

Waterwheels



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



Fourneyron turbine



Francis turbine



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



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)



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



C. Hydro Power Fundamentals



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

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PSE 104 Section 2: Lecture 91 X.Hydroelectric Power A. A. Overview Indirect solar power: rainfall at elevation Largest form of renewable energy in world