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 – 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 92 VIII. Energy from Biomass

PSE 104 Section 2: Lecture 93 X.Hydroelectric Power A. A. 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 94 X.Hydroelectric Power B. B. 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 95 X.Hydroelectric Power Waterwheels

PSE 104 Section 2: Lecture 96 X.Hydroelectric Power B. B. History First known use of hydro for electricity: 1881 in UK - waterwheel power on river River Wey Very fast growth into 20 th 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 97 X.Hydroelectric Power Fourneyron turbine

PSE 104 Section 2: Lecture 98 X.Hydroelectric Power Francis turbine

PSE 104 Section 2: Lecture 99 X.Hydroelectric Power C. 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/sec 2 )(m) = (kg–m)(m) = (Newton)(m) = 1 Joule sec 2 Power must be a function of volume flow of water (Q) Q = m 3 /sec Power (P) = Energy per unit time P = (ρ)(Q)(g)(H) = (kg/m 3 )(m 3 /sec)(m/sec 2 )(m) = N-m/sec = Joules/sec = watts

PSE 104 Section 2: Lecture 910 X.Hydroelectric Power C. C. Hydro Power Fundamentals For water where ρ= 1000 kg/m 3, 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 911 X.Hydroelectric Power C. 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/in 2 = psi (ρ)(g)(H)= (kg/m 3 ) (m/sec 2 )(m) = N/m 2 Turbine types and efficiencies vary with head

PSE 104 Section 2: Lecture 912 X.Hydroelectric Power C. C. Hydro Power Fundamentals

PSE 104 Section 2: Lecture 913 X.Hydroelectric Power C. 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