Hydrox

swedishstreakΜηχανική

22 Φεβ 2014 (πριν από 2 χρόνια και 9 μήνες)

58 εμφανίσεις

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)


http://www.eia.doe.gov/emeu/international/RecentElectricityGeneratio
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

Z
A

2
2
v
g
A

B

p

Advanced Materials and

Sustainable Energy Lab

CBEE

Energy in Hydro

2
3 3 2 1 2 2 3
2 2 2 2 2 2 3 2 2
Energy = Potential Energy + Kinetic Ener
gy + Pressure Energy =
1
2
Dimensional Analysis:
( )
VgZ mv PV
kg m m ms m kg ms N m m
kg m s kg m s kg m s m m kg m s J

   
    
  
         
           
2 2
Formula in book starts here, divides by
Vg
1 1
/////
2 2
Energy is now in "head" (units of length
, m or ft)
VgZ Vg mv Vg PV Vg Z v g P g

    
     
Advanced Materials and

Sustainable Energy Lab

CBEE

Power conversion

A more useful picture is to think of pow
er conversion (= )
By similarity, at top it is
(for most books V = Q, also introduced a
n efficiency term )
Note that the real design variables are
Z
dE
dt
P gZQ
 


and Q:
high head low flow is as good as low h
ead high flow as mentioned before
The efficiency term contains several iss
ues lumped:
Hydraulic head losses due to friction
with walls and efficiency of
turbine
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)


1.852
L
1.852 4.871
10.472 Q
H [m]= ×L
C d

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

1 1 1
cos
t
V q


2 2 2
cos
t
V q


1 1 2 2
( cos cos )
P T Q q q
   
  
(This is known as Euler’s Turbine Equation)

Advanced Materials and

Sustainable Energy Lab

CBEE

Pelton

Turbine

1 1 2 2
( cos cos )
P Q q q
  
 
2 2 1 1
1 2 1 2
P large if sign of cos is same as cos
Max P if and cos cos 1
q q
q q
 
 

   
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

1 1 2 2
( cos cos )
P Q q q
  
 
P is large if the second term disappears

2
2 2
2
0
( cos ) 0
cos 0
q
q




  



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

1
81%, 11, 0.49
X s G
= = = -