Chemical, Biological and Environmental Engineering Hydroelectricity

Advanced Materials and Sustainable Energy Lab CBEE Hydro Power Hydro power is the most widely used renewable resource in the world. In US we got 2.9 quad in 2006 (versus 2.6 quad in 1970) This is about 3% of total US energy, about 9% of electricity. Worldwide hydro dominates for some countries (TWh for 2006): Canada (352, 59%), Brazil (345, 84%), Norway (118, 98%), China (431, 16%), Worldwide (2998, 16.6%) South America is about 2/3 hydro (639.6/951.0) nByType.xls

Advanced Materials and Sustainable Energy Lab CBEE Largest Hydro US: Grand Coulee, WA Largest hydro in US is on Columbia River Opened in 1942, expanded through 1974, capacity is 6.8 GW 380 feet hydraulic head; 125 sq miles reservoir 33 turbines, 112 MW to 800 MW size Can do pumped storage (6 x 50 MW units)

Advanced Materials and Sustainable Energy Lab CBEE Grand Coulee Francis Turbine

Advanced Materials and Sustainable Energy Lab CBEE Current World’s largest: Three Gorges Dam (14,000 MW)

Advanced Materials and Sustainable Energy Lab CBEE What Could be Coming: Grand Inga, DR Congo Present Inga dams: 351 MW, 1,424 MW. Under development, Inga III 4,500 MW and Grand Inga 39,000 MW World Bank pledged support on 9/11/09 (est. $80 billion) Total electric consumption in Africa for 2006 is 547 TWh (Canada = 594 TWh) Take out RSA (228TWh) and Egypt (109TWh) 257 TWh for ca. 800 million people (321 kWh per capita)

Advanced Materials and Sustainable Energy Lab CBEE

Advanced Materials and Sustainable Energy Lab CBEE Hydropower without dam (run of river) Niagara Falls: 50m head, 1.6 MW

Advanced Materials and Sustainable Energy Lab CBEE The Dalles (2000 MW run of river)

Advanced Materials and Sustainable Energy Lab CBEE Hydroelectric systems Impoundment involving dams eg. Hoover Dam, Grand Coulee, Three Gorges Diversion or run-of-river systems, e.g. Niagara Falls Pumped storage? two way flow: water pumped up to a storage reservoir and returned for power generation

Advanced Materials and Sustainable Energy Lab CBEE Hydropower is without opponents, right? Environmental damage? Large reservoirs result in submersion of extensive areas upstream E.g. Three Gorges project displaced 10 6 people… Increase evaporative losses (big deal at Grand Aswan Dam) Effects of natural flooding removed from system Aquatic ecology: fish (esp. salmon in PNW?), plants, mammals. Health hazards? Water chemistry changes (Mercury, nitrates, oxygen), bacterial and viral infections (malaria, schitosomiasis) Relicensing of dams in question (or breaching actually proposed – see “Lower Snake River” issue) Limited Service Life… Slower/low turbulence water created by dams will cause sedimentation Can reduce usefulness for flood control E.g., Three Gorges Dam has about 70 years lifetime for flood control at current rate of siltation

Advanced Materials and Sustainable Energy Lab CBEE Hydroelectric facility schematic

Advanced Materials and Sustainable Energy Lab CBEE Racoon mountain = 1,532 megawatts (4 x 400MW) Z=100m

Advanced Materials and Sustainable Energy Lab CBEE Micro Hydro (less than 100 kW)

Advanced Materials and Sustainable Energy Lab CBEE Hydro Setup At top (station A): gross head (H G ) = Z A At bottom: net head (H N ) Losses: H N =H G -H L Potential Energy Pressure Kinetic Energy ZAZA A B

Advanced Materials and Sustainable Energy Lab CBEE Energy in Hydro

Advanced Materials and Sustainable Energy Lab CBEE Power conversion

Advanced Materials and Sustainable Energy Lab CBEE Losses… Main losses: Residual head at turbine (small, see book) Fluid friction with walls

Advanced Materials and Sustainable Energy Lab CBEE Hazen-Williams Loss Equation Empirical frictional head loss calculation Q = flow rate [m 3 s -1 ] L = length of pipe [m] d = diameter of pipe [m] C = roughness coefficient (PVC = 150, steel = 100)

Advanced Materials and Sustainable Energy Lab CBEE Pelton Wheel The original impulse turbine by Lester Pelton Water squirts out of nozzles onto sets of “buckets” attached to the rotating wheel Best for high pressure, low flow

Advanced Materials and Sustainable Energy Lab CBEE Francis Turbine Developed in 1848 High efficiency conversion of high flow rate water

Advanced Materials and Sustainable Energy Lab CBEE Kaplan For low head, very high flow (e.g., run of river)

Advanced Materials and Sustainable Energy Lab CBEE Application of turbines

Advanced Materials and Sustainable Energy Lab CBEE Turbines Principal concepts in turbine operation: Kinetic energy of a moving fluid is converted to rotational motion of a shaft Momentum of fluid lost equals momentum applied to turbine blade –if arranged in cylindrical symmetry, rate of change of angular momentum is torque transferred Turbine blades deflect fluid –Impulse: energy transferred from “impact” of water on surface –Reaction: energy transferred by “lift” effect

Advanced Materials and Sustainable Energy Lab CBEE Impulse vs. reaction turbine Images nabbed from F. Gunnerson, M.E., U Idaho

Advanced Materials and Sustainable Energy Lab CBEE Turbine Design - 2 Approaches 1. Impulse turbines - most common for micro-hydro systems - capture kinetic energy of high-speed jets - high head, low flow 2. Reaction turbines - pressure difference of blades creates a torque - low head, high flow

Advanced Materials and Sustainable Energy Lab CBEE Usual analysis: Euler’s equation Fluid in at radius r 1 with velocity q 1 Fluid exits at r 2 with velocity q 2 Tangential velocity at r 1 is Tangential velocity at r 2 is For momentum transfer need mass Use density  and flow rate Q Then power transferred is (This is known as Euler’s Turbine Equation)

Advanced Materials and Sustainable Energy Lab CBEE Turbine analysis continued: velocity triangles u (=r  w1w1 q1q1 w2w2 q2q2   Note for next year: this figure has several errors And not useful For Pelton (impulse) w2 and q2 are exchanged, I think Velocity triangles could be used to show that If q2=1/2q1=u and b1=0, b2=180 then vt1-vt2 = max

Advanced Materials and Sustainable Energy Lab CBEE Pelton Turbine Only possible if space around turbine is not filled with water… Need high pressure (head) to create jet at nozzle

Advanced Materials and Sustainable Energy Lab CBEE Pelton Turbine (Pleton Wheel) General principle: Water hits cups such that water is deflected backwards

Advanced Materials and Sustainable Energy Lab CBEE Francis Turbine P is large if the second term disappears i.e., fluid comes in tangentially, leaves radially (makes 90 o turn)

Advanced Materials and Sustainable Energy Lab CBEE Francis control vanes Closed Open Note how vanes guide water flow in direction opposite flow through turbine (but same as turbine rotation direction)

Advanced Materials and Sustainable Energy Lab CBEE Francis Turbine Developed in 1848 High efficiency conversion of high flow rate water

Advanced Materials and Sustainable Energy Lab CBEE Midterm Good work! Plan for remainder of term: –HW + 1 “project” + Final –GS: (1 talk + 1 paper)=(HW) + Final