Hanoi, January 27th 2015

Enrico WeberDEIB – Politecnico di Milano

IMRR ProjectINTEGRATED AND SUSTAINABLE WATER MANAGEMENT OF

RED-THAI BINH RIVER SYSTEM

IN A CHANGING CLIMATE

4. Reservoirs and power plants models

Main reservoirs in the Red River Basin

Strategic reservoirs:• Son La• Hoa Binh• Tuyen Quang (Na

Hang)• Thac Ba

Medium reservoirs (on Da river basin):• Lai Chau• Ban Chat, • Huoi Quang

Not

considered

Essential condition

The model simulation must be extremely fast:

1 year in few milliseconds

We got 3 10-3 sec

Features of reservoirs

• the active (or live) storage

• The stage-discharge curve of the spillways and bottom gates, the intake tower, the penstock curve

By the management point of view a reservoir is characterized by: TuyenQuang

Causal network

tS

1tE1te

1ts 1t

a 1tr t

u

1th

ts

r depends on a and e

st = storage volume at time t

at+1 = inflow volume in [t ,t+1)

et+1 = specific evaporation in [t ,t+1)

rt+1 = effective release volume in [t , t+1)

Mechanistic model

surface

Dung tích hồ [m3]

Diệ

n tíc

h m

ặt n

ướ

c hồ

[km

2 ]TuyenQuang

Mechanistic model

ttt sSeE 11 evaporation

tt sSS surface

storage

Mechanistic model

ttt sSeE 11 evaporation

tt sSS surface

1111 ttttt rEass storage

tt shh level

111 ,,, tttttt EausRrreleaseTuyenQuang

Mechanistic model

evaporation

tt sSS surface

1111 ttttt rEass storage

level

111 ,,, tttttt EausRrrelease

11111 ,,, tttttttttt eausRsSeass

Instantaneous storage-discharge relationships

• s* : storage corresponding to the spillway position

s*

spillway

s(t)

( )r t

TuyenQuang

minimum release

Instantaneous storage-discharge relationships

s*

spillway

open gates

minimum release

s(t)

( )r t

TuyenQuang

Instantaneous storage-discharge relationships

• s min , s max : bounds of the regulation range

s min s max s*

spillway

open gates

maximum release

minimum release

s(t)

( )r t

From this information the function

R t (s t

,u t ,a t+1 ,e t+1 )

is obtained.

Legal constraintsMinumum and maximum (unconstrained) release

legal constrains

Jun 15th - Jun 25th, early flood-period

Before June 25th, if Hoa Binh reservoir level is at 107 m and the Hoa Binh inflow is predicted to be higher than 4,000 m3/s, Son La reservoir is allowed to use the storage between 200 m and 205 m to prevent Hoa Binh reservoir level from exceeding 107 m.

WHAT TO DO?

Son La

st+1 = st +at+1 - Et+1 - rt+1

at+1 = inflow volume [t ,t+1)

Inflow calculation

t t +1

at+1

we assume it uniformly distributed

st = storage volume at time t

Et+1 = evaporation volume in [t , t+1)

a

rt+1 = volume actually released in [t , t+1)

at+1 = st+1 - st + Et+1 + rt+1

st+1 = st +at+1 - Et+1 - rt+1

at+1 = inflow volume [t ,t+1)

Inflow calculation

t t +1

at+1

we assume it uniformly distributed

st = storage volume at time t

Et+1 = evaporation volume in [t , t+1)

a

rt+1 = volume actually released in [t , t+1)

at+1 = st+1 - st + Et+1 + rt+1

from energy measures

st+1 = st +at+1 - Et+1 - rt+1

at+1 = inflow volume [t ,t+1)

Inflow calculation

t t +1

at+1

we assume it uniformly distributed

st = storage volume at time t

Et+1 = evaporation volume in [t , t+1)

a

rt+1 = volume actually released in [t , t+1)

at+1 = st+1 - st + Et+1 + rt+1

from level measures

st+1 = st +at+1 - Et+1 - rt+1

at+1 = inflow volume [t ,t+1)

Inflow estimation

t t +1

at+1

we assume it uniformly distributed

st = storage volume at time t

Et+1 = evaporation volume in [t , t+1)

a

rt+1 = volume actually released in [t , t+1)

at+1 = st+1 - st + Et+1 + rt+1

?

An example: HoaBinh

st+1 = st +at+1 - Et+1 - rt+1

Historical reservoir storageEstimated reservoir storage

EVN estimates

An example: HoaBinh

Historical reservoir storageEstimated reservoir storage

x 4.53

st+1 = st +at+1 - Et+1 - rt+1

An example: HoaBinh

x 4.53

st+1 = st +at+1 - αEt+1 - rt+1

Historical reservoir storageEstimated reservoir storage

Hydropower plant

Hydropower plant model

Hazen-Williams formula [Gardner Stewart.W [1920]

for each turbine for the whole plant

net head

Tuyen Quang

The stage function can be more complex: SonLa

Influence of Hoa Binh reservoir level

Historical Son La downstream level

Historical Hoa Binh reservoir levelEstimated Son La downstream level

1/1/2011 - 31/07/2012

Hydropower plant model

turbine efficiency η η = (q,H) orη = (p,H)

Characteristic curve of a turbine of Tuyen Quang power station

Sources:EVN

for each turbine for the whole plant

Tuyen Quang

Optimal turbines allocation

the efficiency of the two turbines must be equal

If all the turbines are identical, it follows that they must all be fed with the same flow.

the total flow Q has to be equally split among m turbines, where m is the number of turbines that maximizes the total generated power P, given the net head H

Optimal hours allocation

Ej energy production generated by splitting the volume R in j hours

For a given H

1 hour

2 hours

3 hours

Tuyen Quang

The distribution in time has nothing conceptually different from the distribution among the turbines.

Optimality condition: the efficiency must be the same for every turbine and every instant of times

If the net head H were know

Optimal hours allocation

Solve the system numerically for any j and (R,hr)

However, the net head H is not known in advance: it depends upon the volume R (which influences the downstream level hd) and the flow q through the turbines (which, due to the optimality condition, must be the same in each hour and each turbine).

hr = 95

hr = 105

Tuyen Quang

From mechanic to electrical energy

http://www.snowyhydro.com.au

Tuyen Quang

Error = -

maximum (electrical) energy that can be generated if:

the released volume Rt in day t is

know since the start of the day

the reservoir level hr remains stationary for the whole day

efficiency of the generator

Tuyen Quang

Error = -

Final tuning

http://www.snowyhydro.com.au

maximum (electrical) energy that can be generated if:

the released volume Rt in day t is

know since the start of the day

the reservoir level hr remains stationary for the whole day

efficiency of the generator

depends on the diameter and the type of material of the penstock Estimate θ

maximum (electrical) energy that can be generated if:

the released volume Rt in day t is

know since the start of the day

the reservoir level hr remains stationary for the whole day

Tuyen Quang

Error = -

Final identification

http://www.snowyhydro.com.au

Tuyen Quang

HoaBinh

Www.wikimapia.org

Hoa Binh validationError = - 3 year moving windows

efficiency

Hoa Binh validationError = - 3 year moving windows

prior the year 2009

efficiency

SonLa

www.vietnamonline.com 

Son La validation

Togliere verde

Son La validation

1

2

3

4

5

turbines

Son La validation

1

2

3

4

5

turbines

wikipedia.org

TuyenQuang

Reservoir: release function (1)

before July 2012

Reservoir: release function (1)

Historical downstream levelEstimated downstream level

2002-2012

Historical data

Chiem Hoa reservoir

Reservoir: release function (1)

before July 2012

declared to be valid after July 2012

Reservoir: release function (1)

before July 2012

declared to be valid after July 2012

proposed

Van Coc diversion

Scheme of RTBR system

Van Coc diversion

Van Coc rules

• Opening

When

hHNt > 12.8 m and (hHN

t+1 > 13.4 or hHNt+2 > 13.4)

• Closing

When

hHNt < 13.4 m and (hHN

t+1 < 13.4 and hHNt+2 < 13.4)

The detention basin dynamics is assumed to be negligeable

^ ^

^ ^

Thanks for your attention

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