6L_Dubas_1_

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