prospects of wind and pumped storage systems’ integration in greek islands george caralis...

Prospects of Wind and Pumped Storage

systems’ integration in Greek islands

George CaralisMechanical Engineer NTUA

Wind Energy Laboratory

Contents of the presentation

Contents• Current situation in the autonomous Greek

islands• Operational targets and Architecture of WPS• Simulation • Parameters for optimization • Case studies - Results • Conclusions - Recommendations

G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 2

Current situation in the autonomous Greek islands

• 4% of the national demand with 1 million citizens• Weak autonomous electrical grids, based almost

entirely on oil • High rates of increase (due to tourism development)

• High variation of demand between summer and winter and during the day (low load factor of the conventional units, high Electricity Production Cost)

• Abundant wind potential (annual wind speed 8-9m/s)

• High investor’s interest for wind applications • Constrain in the wind installed capacity• Wind power rejection during low demand




Electricity Production Cost (2005)

0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

10 100 1000 10000 100000 1000000

peak demand (kW)

€/k

Wh

8micro

10medium

1 Large

CreteLesvos

Serifos

11small



share of fuel cost to electricity production cost

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

10 100 1000 10000 100000 1000000

peak demand (kW)

8micro

10medium

1 Large

Crete

LesvosSerifos

11small

Current electrical system


Wind energy combined with pumped storage unit (WPS)


Operational design and Architecture of WPS

a. Peak demand supply (when the demand exceeds one value)

b. Supply of a stable percentage of the demand

c. Stable operation of the turbine at its technical minimums as a spinning reserve


050

100150200250300350400

73 81 89 97 105 113hours

Po

we

r d

em

an

d (

MW

)

050

100150200250300350400

73 81 89 97 105 113

Po

we

r D

em

an

d (

MW

)

050

100150200250300350400

73 81 89 97 105 113

Po

we

r D

em

an

d (

MW

)

other sources turbine

last 24hours' peak

Options of the hydro turbine operation


Single or double penstock • Single penstock

– Cheaper solution– Turbine priority– Pumping priority

• Double penstock– Operational flexibility– Independent pumping and

turbine operation– Quick response of the

turbine when it is needed



Instantaneous wind penetration permitted • “Simple control”: Stable maximum instantaneous

wind penetration “δ”– (i.e. δ = 30%), as it is used today in most autonomous

islands with concrete wind installed capacity.

• “Advanced control”: Increase the wind penetration by an amount equal to the rest ability of the hydro-turbine. – Two-sided communication (The EUO should know the

rest capacity of the hydro-turbine, in order to permit equal increase of wind penetration).

– The turbine should be in operation.


Scenarios definition


Scenario

Single/ Double penstock

Operational target Wind penetration permitted

1 Single penstock/ turbine priority

Peak demand supply Stable δ=30%

2 Double penstock Peak demand supply Stable δ=30%

3 Double penstock Peak demand supply Advanced control

4 Double penstock Stable supply of a percentage of the demand

Stable δ=30%

5 Double penstock Stable supply of a percentage of the demand

Advanced control

6 Double penstock Stable operation of the turbine at its technical minimums

Advanced control

Conventional power given the rest ability of the committed conventional units is used for complementary pumping

Simulation

Non-dynamic analysis, based on annual hourly time-series (demand and wind)

Main Steps – Calculations 1. The hydro-turbine’s set-point, the number

of conventional units committed 2. The wind power absorbed directly and the

wind power rejected by the grid 3. The conventional units set-point, Available

grid power for pumping4. The pumping - turbine operations and the

water flowsG.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 12

Parameters for optimization – Dimensioning The most important parameters:

– the wind potential (mean wind velocity) and– the hydraulic head between the two reservoirs.

The main parameters for optimization are: – the wind capacity to be installed, – the capacity of the two reservoirs, and– the capacity of the hydro-turbine

Other parameters are: – Rating and number of pumps– Diameter of the Penstock


Main assumptions

• H=300m, L=3000m • Wind velocity: 8.1m/s at the hub-height. • Financial evaluation without any subsidy• Oil price: 54$/b (annual mean for 2005)• Basic parameters introduced dimensionless:

– The wind installed capacity as a share of the mean annual load demand (10% - 390% by step 20%)

– The volume of the reservoir in respect with the maximum hourly water pumping ability (10 to 150 by step 20).

– The maximum operational target (as a percentage of the peak) is calculated using an iterative procedure. A bigger target could be set, but it would be achieved in less than 100% of the year.


Optimization procedure - Example: Crete


0

20000000

40000000

60000000

80000000

100000000

120000000

140000000

160000000

180000000

200000000

0% 20% 40% 60% 80%part of the peak to be covered with the turbine

Re

se

rvo

ir's

vo

lum

e (

m^

3)

31921532142753363974585195806417037648258869471008106911301191

0,00

0,05

0,10

0,15

0,20

0,25

0,30


Tu

rbin

e's

EP

C (

€/k

Wh

)

31921532142753363974585195806417037648258869471008106911301191

lower envelope curve

Indexes for the evaluation • Turbine’s EPC

• Conventional unit’s EPC

• Electrical system’s EPC


Crete

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35


Tu

rbin

e's

EP

C (

€/kW

h)

1

2

3

4

5

6

Crete

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35


Co

nve

nti

on

al u

nit

s' E

PC

(€

/kW

h)

1

2

3

4

5

6

Crete

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35


Ele

ctri

cal

syst

em's

EP

C

(€/k

Wh

)

1

2

3

4

5

6

Crete

0%

10%

20%

30%

40%

50%

60%

70%

80%


Hyb

rid

's e

ner

gy

sup

ply

(%

)

1

2

3

4

5

6

Results - Crete


Crete

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35


Tu

rbin

e's

EP

C (

€/kW

h)

1

2

3

4

5

6

Crete

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35


Co

nve

nti

on

al u

nit

s' E

PC

(€

/kW

h)

1

2

3

4

5

6

Crete

0%

10%

20%

30%

40%

50%

60%

70%

80%


Hyb

rid

's e

ner

gy

sup

ply

(%

)

1

2

3

4

5

6

Crete

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35


Ele

ctri

cal

syst

em's

EP

C

(€/k

Wh

)

1

2

3

4

5

6

Results - Crete


Lesvos

0,00

0,05

0,10

0,15

0,20

0,25


Tu

rbin

e's

EP

C (

€/kW

h)

1

2

3

4

5

6

Lesvos

0,00

0,05

0,10

0,15

0,20

0,25


Co

nve

nti

on

al u

nit

s' E

PC

(€

/kW

h)

1

2

3

4

5

6

Lesvos

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%


Hyb

rid

's e

ner

gy

sup

ply

(%

)

1

2

3

4

5

6

Lesvos

0,00

0,05

0,10

0,15

0,20

0,25


Ele

ctri

cal

syst

em's

EP

C

(€/k

Wh

)

1

2

3

4

5

6

Results - Lesvos


Serifos

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

0% 20% 40% 60% 80% 100%part of the peak to be covered with the turbine

Tu

rbin

e's

EP

C (

€/kW

h)

1

2

3

4

5

6

Serifos

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00


Co

nve

nti

on

al u

nit

s' E

PC

(€

/kW

h)

1

2

3

4

5

6

Serifos

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%


Hyb

rid

's e

ner

gy

sup

ply

(%

)

1

2

3

4

5

6

Serifos

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00


Ele

ctri

cal

syst

em's

EP

C

(€/k

Wh

)1

2

3

4

5

6

Results - Serifos


Comparison of the three islands (scenario 3)


scenario 3

Lesvos

Crete

Serifos

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0


Tu

rbin

e's

EP

C (

€/kW

h)

Crete

Lesvos

Serifos

scenario 3

Serifos

Crete

Lesvos

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0


Co

nve

nti

on

al u

nit

s' E

PC

(€

/kW

h)

Crete

Lesvos

Serifos

scenario 3

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%


Hyb

rid

's e

ner

gy

sup

ply

(%

)

Crete

Lesvos

Serifos

scenario 3

Serifos

Crete

Lesvos

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0


Ele

ctri

cal

syst

em's

EP

C

(€/k

Wh

)

Crete

Lesvos

Serifos

Proposed solutions for the examined islands


Island Peak (MW)

Wind Capacity (MW)

Reservoir (•106 m3)

Turbine (MW)

% peak supply

% energy supply

Crete 563 580-1200 40-80 250-350 44-63% 45-70%

Lesvos 58 44-130 2.3-10 23-40 40-68% 41-83%

Serifos 2.9 2.1-3.2 0.2-0.3 1.6-2.3 55-81% 49-93%

Lesvos

30$/b

80$/b

54$/b

0,00

0,10

0,20

0,30

0,40

0,50

0,60


Ele

ctri

cal

syst

em's

EP

C (

€/kW

h)

80$/b

54$/b

30$/b

Serifos

30$/B

54$/b

80$/b

0,00

0,10

0,20

0,30

0,40

0,50

0,60


Ele

ctri

cal

syst

em's

EP

C (

€/kW

h)

80$/b

54$/b

30$/b

Sensitivity analysis of the Brent price


Crete

30$/b

54$/b

80$/b

0,00

0,10

0,20

0,30

0,40

0,50

0,60


Ele

ctri

cal

syst

em's

EP

C (

€/kW

h)

80$/b

54$/b

30$/b

Conclusions• The proposed architecture of the WPS (scenario

3):– Double penstock / “Peak demand supply” / “Advanced

control”• With the introduction of the WPS the system’s EPC

is decreased• This benefit should be shared between the pubic

utility and the investor, by the definition of a suitable price.

• The basic parameters in issue are: – Hydraulic head and the Wind potential– Plant size, Island size– Current cost– Duration curve of the demand.

• The production cost is quietly defined• The introduction of the WPS is proposed and

expected to have very positive results


Thank you for your attention

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