lect21hydropower1-2012 [compatibility mode]
DESCRIPTION
hydro power 2TRANSCRIPT
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Hydro Power
Sergio CaparedaBAEN, TAMU
The Hydrologic Cycle
Worlds Hydro Power Capacity• Produces 21% of world’s electricity supply• 1,010,000 MW combined power output with a theoretical potential of 2,800 GW
• 2,000 hydro power plants in US with a total capacity of 92,000 MW
• Largest hydropower plant in US is the 7,600 megawatt Grand Coulee Power Station, Columbia River, Washington State.
Continent % Energy (GWh)
Asia 24% 618
North America 23% 595
Europe 20% 537
Country Energy (GWh)
Canada 315
China 309
Brazil 282
US 255
● Hydropower is the renewable energy source that produces the most electricity in the United States● Accounted for 6% of total US electricity generation and 60% of the generation from renewables in 2010.● Supplies 28 million households with electricity equivalent to nearly 500 million barrels of oil●The US consumes around 18.8 million barrels of crude oil per day
US Hydro Power Generating Capacity
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● Hydropower is one of the oldest source of energy in the United States● The first US hydroelectric power plant was built on the Fox River near Appleton, Wisconsin in 1882.● Accounted for 6% of total US electricity generation and 63% of the generation from renewables in 2011 (up by 3% from a year before)
US Hydro Power Generating CapacityWater Power
• Theoretical Power (Pt)
• WherePt = power in hpQ = mass flow rate, lbs/minQ = ρAvv = velocity of water stream, ft/minA = cross sectional area of water stream, ft2ρ = density of water, 62.4 lbs/ft3H = head, ft
000,33)( QHhpPt
Water Power• Theoretical Power (Pt)
• WherePt = power in kWQ = mass flow rate, kg/secQ = ρAvv = velocity of water stream, m/secA = cross sectional area of water stream, m2
ρ = density of water, 1000 kg/m3
H = head, m
102)( QHkWPt
Kalayaan Pumped Storage Power Plant, Philippines
3
hrshrm
mreleasestoragehrsTimeeargDisch 51
sec3600sec333,183
sec/1201022)( 3
36
Pumped Storage Facility in the Philippines
Sample Calculations
• Given: H = 291 meters, pipe diameter = 6 m; terminal velocity = 10 m/s; Efficiency 80%. Determine the power output.
• Solution:• 1. Theoretical Power
• 2. Actual Power Output
mNsWx
s
mxmkgsNx
m
kgxsmxmxmQHWPt
2
2
3
2 8.91000104)6(291
102)(
MWWx
MWxWMWPt 806101
329,806)( 6
MWMWxMWPa 64580.0806)(
Bhumibol Dam and Hydro Power Plant, Thailand
Details:1. Capacity:535 MW2. Completed: 19693. Annual Energy Production: 2.2B-kWh
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The 200 W Mini Hydro Power Unit Example• Given: Volumetric flow rate = 35 liters/sec and 1 meter head. Determine the theoretical power possible and actual power if the conversion efficiency was 60%.
• Solution1. 2. 3. 4. 5. Note that 35 lps = 555 gpm.
sec/351sec35sec)/( kg
likgxlikgQ
kWW
kWxmNWxmx
mkgNxmxkgHQkWPower t 343.0
1000sec
sec
8.9sec1sec35)( 2
2
WkWEffHQkWPower a 206206.06.0*343.0)(
yrkWhryrdaysx
dayhrskWxyrkWhOutputYearly /180536524206.0)/(
Technical Specifications of Mini Hydro Units
MHG‐200W MHG‐500W MHG‐1000W
Water head 1.5 m 1.5m 1.5 m
Water flow 35 l/s 70 l/s 130 l/s
Output voltage 220 VAC 220 VAC 220 VAC
Output frequency 50‐60 Hz 50‐60 Hz 50‐60 Hz
Output power 200 W 500 W 1,000 W
Generator weight 16 kg 32 kg 75 kg
%9.38%1008.9sec
secsec5.135sec200)200(
2
2
xJ
mNxm
xW
JxN
mkgxmkg
WInput
OutputWEfficiency
%6.48%1008.9sec
secsec5.170sec500)500(
2
2
xJ
mNxm
xW
JxN
mkgxmkg
WInput
OutputWEfficiency
%3.52%1008.9sec
secsec5.1130sec1000)1000(
2
2
xJ
mNxm
xW
JxN
mkgxmkg
WInput
OutputWEfficiency
Inefficiencies
• Hydraulic loses in conduits and turbines• Mechanical losses in bearings and power transmission system
• Electrical losses in generator, station use and transmission (for hydroelectric power)
• Overall effect is to reduce the theoretical power by a factor of 0.60 – 0.80
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Water Power Generating Devices
• Hydraulic Rotating Prime Movers– Waterwheels (overshot, undershot, breast)– Tub wheel/flutter wheel– Turbines (Reaction: Francis, Nagler, Kaplan, Impulse: Pelton, Turgo‐wheels)
• Hydraulic Rams• Hydraulic Air Compressor
Water Turbines
Comparison of Impulse Versus Reaction TurbinesReaction Turbines
● Reaction turbines are acted on by water, which changes pressure as it moves through the turbine and gives up its energy. They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow.
● Newton’s third law (law or reciprocal reactions or conservation of momentum) describes the transfer of energy for reaction turbines.
●Most water turbines in use are reaction turbines.● They are used in low and medium head applications.
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Waterwheels
Overshot (35 ft x 40” wide) Undershot (10 ft x 24” wide)
Undershot Waterwheel
Application Application: Water Powered Sawmill
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Tubwheel: A small undershot wheel mounted horizontally
Francis Turbine Runner
Propeller Type Kaplan Runner Impulse Turbines• Impulse turbines change the velocity of a water jet. The jet
impinges on the turbine's curved blades which reverse the flow. The resulting change in momentum (impulse) causes a force on the turbine blades. Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy.
• Prior to hitting the turbine blades, the water's pressure (potential energy) is converted to kinetic energy by a nozzle and focused on the turbine. No pressure change occurs at the turbine blades, and the turbine doesn't require a housing for operation.
• Newton’s second law (F=ma) describes the transfer of energy for impulse turbines.
• Impulse turbines are most often used in very high head applications.
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Impulse: Pelton Runner Turgo‐wheels
Typical Range of Heads (m)• Kaplan turbine – axial flow reaction turbine
– Head: 2 < H < 70 m– Specific speeds: 300 ‐ 1100 rpm
• Francis turbine – mixed flow reaction turbine– Head: 300 < H < 500 m– Specific speeds: 60 ‐ 400 rpm
• Pelton turbine – an impulse turbine– Head: 50 < H < 1300 m– Specific speeds: 4 ‐ 70 rpm
• Turgo wheels– Head: 0 < H < 250 m
• Deriaz turbine – reaction turbine, mixed flow– Head: 1 < H < 200 m
Summary of Various Types of Hydro TurbinesHigh Head Medium head Low head
Impulse Turbines PeltonTurgo
Cross‐flowMulti‐inject PeltonTurgo
Cross‐Flow
Reaction Turbines Francis PropellerKaplan
Characterizing Turbines• Specific Speed – used to compare different impellers • Unit of specific speed = dimensionless• Equation for specific speed• where• Ns = specific speed• ω = pump shaft rotational speed (rpm)• q = flow rate (gal/min; m3/hr)• h = head rise = (ft; m)
4/3
2/1
h
qNs
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Specific Speed, ηs• This number describes the speed of the turbine at its maximum
efficiency with respect to the power and flow rate. The specific speed is derived to be independent of turbine size.
• Given the fluid flow conditions and the desired shaft output speed, the specific speed can be calculated and an appropriate turbine design selected.
• The specific speed, along with some fundamental formulas can be used to reliably scale an existing design of known performance to a new size with corresponding performance.
• Example. Given pump rotational speed of 1760 rpm, flow rate of 1500 gal/min and head of 100 ft . Calculate the specific speed
• Solution:
• This is the specific speed for a typical centrifugal pump.
2156100
1500*1760)4/3(
)2/1(sN
Typical Values for Ns in US Units (gpm)Types Ns range Remarks
Radial flow 500<Ns<4000 Typical for centrifugal impeller pumps with radial vanes; double and single suction; Francis vane impellers in the upper range
Mixed Flow 2000<Ns<8000 Typical for mixed impeller single suction pumps
Axial Flow 7000<N2<20000 Typical for propellers and axial fans
Banki Turbine (Mitchel, Crossflow or Ossberger)
Uses nozzles and blades instead of buckets (similar
to overshot waterwheels)
How a Hydro Power Plant Works
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Hydro Power Monograph Types of Hydro Power Plant• On the basis of operation
– Base load plant and Peak load plant
• Plant capacity– Micro (< 5 MW)– Medium capacity (5 – 100 MW)– High capacity plant (100‐1000 MW)– Super power plant (> 1000 MW)
• Based on head– Low head (<15 m)– Medium head plant (15‐50 m)– High head plant (>50 m)
Grouping done arbitrarily and not
sacrosanct
Types of Hydro Power Plant• Based on hydraulic features
– Conventional– Pumped storage– Tidal power type
• Based on Construction Feature– Run‐of‐river– Valley dam type– Diversion canal– High head diversion
Diversion Canal: Tazimina Project, Alaska
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Types of Hydro Plant
• Run-of-the-river
• Diversion Canal
• Valley Dam type
• High head diversion
Types of Pumped Storage Hydro Electric Power
System
800 kW Hydro Power Facility, King Cove, Alaska (700 residents)
Hoover Dam (17 generators @ 133 MW each produces >2,000 MW)
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The Grand Coulee Power Plant7,600 MW
Largest Hydroelectric Power Plant in the World (13,320 MW), Brazil
Environmental Issues
• Water quality (losses oxygen and gains nitrogen and phosphorus)
• Damage to surroundings• Obstruction of aquatic life• Siltation• Affect irrigation scheduling• Overflowing of dams