Small hydro plants: 1) Encountered difficulties 2) Variable speed 3) Water-wheels
University of Applied Sciences of Western Switzerland Delémont
HENe
HEVd
HEGe
HEF
6 cantons: Jura Neuchâtel Fribourg Vaud Genève Valais + Bern
HEVs
5 engineering schools
Engineering school
Fribourg
Lausanne
Yverdon
Sion
Le Locle + St-Imier
Genève
Teaching activities
Canton
FR
VD
VD
VS
NE
GE
Department of civil engineering
X
X
X
Department of mechanical engineering
X
X
X
Lectures on hydraulic machines
X
Department of electrical engineering
X
X
X
X
X
X
X
X
X
X
X
X
Encountered difficulties 1 Flow rate available?
1st year 2nd year 3rd year 4th year 5th year 6th year 7th year
Flow hydrograph (over 7 years)
Flow rate Q [l/s] 90.0 80.0 70.0 60.0 50.0 40.0 30.0 20.0 10.0
Au gu st Se pt em be r
Ju ly
Ju ne
M ay
Ap ri l
M ar ch
Fe br ua ry
Ja nu ar y
O ct ob er
N ov em be r D ec em be r
0.0
Encountered difficulties 2 Penstock: - data on existing pipes: diameter, material,‌ - net head, losses - costs of excavation Head losses Roughness k = 0.0013 [mm]
DN 100 DN 150 DN 200 DN 250 DN 300 DN 400
20
18
Head loss [mWS / 100 m pipe ]
16
14
12
10
8
6
4
2
0 0
20
40
60
80
100
Flow rate [l/s]
120
140
160
180
200
Encountered difficulties 3 Turbine and generator: - types - efficiencies - costs
Encountered difficulties 4 Connection to grid: - transformer - losses in wires - costs of wires and excavation - good coordination
Encountered difficulties 5 Capital costs: - borrowed capital - rate of interest - duration of paying off - selling of electric power
Personal relationship
Pumps running as turbines Variable speed
Characteristic of a pump running as a turbine: net head: 80 to 110 m, flow rate: 50 to 90 l/s, maximal efficiency: 79 %
120 4000 rpm
3000 rpm
3500 rpm 100
2500 rpm
Penstock characteristic
2000 rpm
H [m]
80
M=0 60
Mechanical power [kW]
40
20
0
0
20
40
60
Flow rate Q [l/s]
80
100
120
Topology of the frequency converter for variable speed with a synchronous or asynchronous generator
SM
grid control
machine control
Water-wheels Flow coefficient = filling coefficient:
ϕB =
Q /( a B ) Q = Ue a B π De n
Net head:
C ⎛D ⎞ H = De + Δz + H o + ⎜ e − Δy ⎟ tan α + o 2g ⎝ 2 ⎠
2
Energy coefficient:
2g H ψ= 2 Ue
Efficiency hillchart of a w ooden w ater-w heel
75 70 65 60 55 50 ψ [ −]
45
0.3l/s
η =79 %
η=0 .775
0.6l/s
η=0 .75
40
0.9l/s
35
1.2l/s
30
1.35l/s
η=0 .7
1.5l/s
25 20 15 10 η=0 .6 5
5
η=0 .6
0 0
0.05
0.1
0.15
0.2
0.25
0.3
0.35 ϕ B [-]
0.4
0.45
0.5
0.55
0.6
0.65
0.7