Prospects of Wind and Pumped Storage systems’ integration in Greek islands George Caralis Mechanical 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 G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 3

Current situation in the autonomous Greek islands G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 4

Current situation in the autonomous Greek islands G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 5

Current electrical system G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 6

Wind energy combined with pumped storage unit (WPS) G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 7

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 G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 8 Options of the hydro turbine operation

Operational design and Architecture of WPS 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 G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 9

Operational design and Architecture of WPS 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. G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 10

Scenarios definition G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 11 Scena rio Single/ Double penstock Operational targetWind penetration permitted 1Single penstock/ turbine priority Peak demand supplyStable δ=30% 2Double penstockPeak demand supplyStable δ=30% 3Double penstockPeak demand supplyAdvanced control 4Double penstockStable supply of a percentage of the demand Stable δ=30% 5Double penstockStable supply of a percentage of the demand Advanced control 6Double penstockStable 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 pumping 4.The pumping - turbine operations and the water flows G.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 G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 13

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. G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 14

Optimization procedure - Example: Crete G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 15

Indexes for the evaluation Turbine’s EPC Conventional unit’s EPC Electrical system’s EPC G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 16

Results - Crete G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 17

Results - Crete G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 18

Results - Lesvos G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 19

Results - Serifos G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 20

Comparison of the three islands (scenario 3) G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 21

Proposed solutions for the examined islands G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 22 IslandPeak (MW) Wind Capacity (MW) Reservoir (10 6 m3) Turbine (MW) % peak supply % energy supply Crete %45-70% Lesvos %41-83% Serifos %49-93%

Sensitivity analysis of the Brent price G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 23

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 G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 24

Thank you for your attention G.Caralis, “Prospects of Wind and Pumped Storage systems’ integration in Greek islands” 25