Thermal Power Plants in Today s and Tomorrow s Energy System

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1 Institute of Combustion and Power Plant Technology Prof. Dr. techn. G. Scheffknecht Thermal Power Plants in Today s and Tomorrow s Energy System Prof. Dr. techn. G. Scheffknecht

2 Today s Energy System The European power system developed along with thermal power plants Today thermal power plants still provide over 70 % of electricity generation within the European Union Thermal power plants are used to guarantee reliability of supply Share of thermal power plants is decreasing due to massive increase of renewable energies 2

3 Renewable Energies in the European Union Mandatory target of the European Union, 20 % for renewable energy s share of total energy consumption by 2020 Targets for renewable energy s share in the electricity sector are part of National Renewable Energy Action Plans (NREAP) Roadmap how member states expects to reach its target Detailed information about planned capacities of renewable energy sources 3

4 Renewable Energies in the European Union Installed capacity of renewable energies in GW Increasing share of intermittent generation Offshore wind Onshore wind Solar (PV) Biomass Other Hydropower Source: National Renewable Energy Action Plans (NREAP) collected by ECN 4

5 Renewable Energies in the European Union Increasing share of intermittent generation is replacing thermal power plants What happens at night without generation from photovoltaics? What happens when there is only little wind? What happens during storm shutdown of wind power plants What happens during solar eclipses High gradients of photovoltaics No shutdown of photovoltaics possible Thermal power plants are necessary for multiple reasons 5

6 Contribution from Thermal Power Plants Secured generation capacity Secure system operation Black-start capacity 6

7 Secured Generation Capacity Thermal power plants provide a secured generation capacity The power output does not depend on external influences like weather phenomena The power output can be controlled very easily and changed in short time frames 7

8 Example: Wind Generation in Germany 2013 Fluctuations in power generation Installed capacity: 32.5 GW Maximum generation on 05 December 2013 Wind power generation: 26.3 GW (approx. 80 % of installed capacity) Minimum generation: GW (04 September 2013) Power demand (load): 62 GW (04 September 2013) Dispatchable power plants necessary to cover power demand 8

9 Example: Development of Residual Load in Germany Maximal residual load nearly unchanged 9

10 Example: Wind Generation in Germany 2013 Fluctuations in power generation Installed capacity: 32.5 GW Maximum generation on 05 December 2013 Wind power generation: 26.3 GW (ca. 80 % of inst. capacity) Minimum generation: GW (04 September 2013) Power demand (load): 62 GW (04 September 2013) Dispatchable power plants necessary to cover power demand Power imbalances due to forecast error 10

11 Forecast Error of Intermittent Generation Example of day-ahead wind forecast in 2013 Installed capacity: 32.5 GW Minimum forecast error: 6.1 GW (ca. 19 % of inst. capacity) 6.1 GW 11

12 Contribution from Thermal Power Plants Secured generation capacity Secure system operation Black-start capacity 12

13 Secure System Operation Within the power system, the power balance has to be maintained at all times Fluctuations of generation or load can be caused by various reasons Uncertainties within forecast of load Uncertainties within forecast of intermittent generation Shutdown of power plants or loads Outage of operation equipment 13

14 Secure System Operation Power generation = load Grid frequency = 50 Hz 50 Hz ~ ~ 14

15 Secure System Operation Power generation < load Grid frequency < 50 Hz 50 Hz More load than generation ~ ~ 15

16 Secure System Operation Power generation > load Grid frequency > 50 Hz 50 Hz More generation than load ~ 16

17 Secure System Operation Thermal power plants are used to ensure the secure operation of the system Frequency control (primary, secondary and tertiary control) 17

18 Load-frequency Control Stabilizing and restoring of the grid frequency f [Hz] 50, t [s] 49,5 Load-frequency control to guarantee stability and compensate active power losses 49,0 18

19 Secure System Operation Thermal power plants are used to ensure the secure operation of the system Frequency control (primary, secondary and tertiary control) Damping of frequency oscillations and power imbalances 19

20 Inertial Response - Grid Inertia Rate of Change of Frequency (ROCOF) becomes problematic for systems with high feed-in from wind power like Ireland f [Hz] 50,0 Lower damping with less thermal power plants t [s] Higher damping with more thermal power plants 49,5 Damping of deviations by rotational energy of turbines and generators Limitation due to stability reasons 49,0 20

21 Secure Grid Operation Thermal power plants are used to ensure the secure operation of the system Frequency control (primary, secondary and tertiary control) Damping of frequency oscillations Voltage support 21

22 Voltage Control Voltage drop due to power flow Generation Load Voltage control by thermal power plant Limitation due to stability reasons V gen Load flows over long distances can lead to voltage problems V load Power flow V reserve Limitation due to stability reasons Transmission distance 22

23 Contribution from Thermal Power Plants Secured generation capacity Secure system operation Black-start capacity 23

24 Black-start capacity Many thermal power plants are suitable for island operation Thermal power plants can handle black starts in order to restore the electric power system after a blackout 24

25 Summary Thermal power plants are used to ensure the secure operation of the system Thermal power plants are necessary to guarantee stability Load-frequency control Inertial damping Voltage control Thermal power plants are necessary to restore the electric power system after a blackout 25

26 Thank you for your attention Prof. Dr. techn. Günter Scheffknecht Tel.: / , guenter.scheffknecht@ifk.uni-stuttgart.de University of Stuttgart Institute of Combustion and Power Plant Technology Pfaffenwaldring Stuttgart Germany 26