Hybrid Solar Thermal Integration at Existing Fossil Generation Facilities

1. Hybrid Solar Thermal Integration at Existing Fossil Generation Facilities Kevin Miller Manager of Engineering, Black & Veatch, South Africa

2. AGENDA Solar Thermal Integration at Existing Rankine Cycle Generating Facilities [HYBRID CSP] Solar Integration with Coal / Oil Steam Plants

3. Concepts of combined Brayton / Rankine Cycle Generation Integrated Solar Combined Cycle adds steam to the Rankine Cycle Brayton Cycle Rankine Cycle

4. Hybrid Concepts of Integrated Solar Thermal (ICSS) Steam produced from renewable source Reduces use of natural gas or light oil No additional capacity (MW) will result from the operation of the solar thermal facility

5. Eskom CSP Workshop Why consider Hybrid CSP? More efficient with lower capitol cost Solar energy can be converted to electric energy at a higher efficiency. Capital costs are lower than for a CSP-only facility of similar size. Minimal additional plant staff is required A hybrid plant does not suffer from the thermal inefficiencies associated with the daily startup and shutdown of the CSP facility Potential reduction in fuel costs (fossil fuel input / MWh will decrease) Significant reduction in carbon emissions / MWh

6. Eskom CSP Workshop Key Characteristics of Candidate Facilities for addition of hybrid CSP Located in area of high Direct Normal Solar Irradiation (DNI) Adequate space available • Allocation of approximately 2.75 Hectares / Mw

7. Eskom CSP Workshop Direct Normal Irradiation (DNI)

8. Eskom CSP Workshop Integration of CSP at an existing Gas Turbine Combined Cycle facility in Florida, USA Black & Veatch was Owner’s Engineer on the addition of 75 MW of CSP steam generation at Martin Station Area with high Direct Normal Solar Irradiation (DNI) Available adjacent land area (202 hectare) Available steam turbine capacity Reduction in associated fuel cost & carbon emissions

9. Eskom CSP Workshop Martin Next Generation Solar Energy Center Source; John Van Beekum for The New York Times

10. Eskom CSP Workshop Martin Next Generation Solar Energy Center Martin Next Generation Solar Energy Center was, until recently, the second largest solar-thermal facility in the world and the largest solar plant of any kind outside of California Facility may be the first hybrid facility in the world to connect a solar facility to an existing combined-cycle power plant Provides 75 megawatts of solar thermal capacity Designed to produce an average of 155,000 MWh of electricity annually The expected reduction of system-wide green-house gas emissions is projected to be approximately 2.75 million tons over a 30-year period

11. Eskom CSP Workshop Combined Cycle Generic Layout Main Steam Steam Turbine HP IP / LP Air-Cooled Condenser Hot Reheat Cold Reheat LP Steam IP Steam Duct Firing HP Steam Fuel H P S H R H H P E V H P E C H P E C I P S H I P E V H P E C I P E C L P S H L P E V L P E C Air Gas Turbine Heat Recovery Steam Generator BFP

12. Eskom CSP Workshop Potential Solar Steam Injection Points The most efficient use of solar energy is displacing saturated steam production at the highest pressure. The least efficient use of solar energy is feedwater preheating and steam superheating Admit Steam In LP Circuit Admit Steam Into Cold Reheat Admit Steam Into Hot Reheat Admit Steam Into HRSG HP Circuit Between Evaporator and Superheater Admit Main Steam

13. Eskom CSP Workshop Steam Admission Locations Driven By Solar Technology Parabolic Trough Technology was selected by the Client TYPICAL ACHIEVABLE STEAM TEMPERATURES Parabolic Trough • Fluid: Synthetic oil; HTF Temperature: 748ºF (398ºC) • Steam Temperature - ~715 F Central Receiver • Fluid: Steam, molten salt, air • Steam Temperature: 1025ºF (550ºC) Compact Linear Fresnel Reflector • Fluid: Steam • Steam Temperature: 520ºF (270ºC)

14. Eskom CSP Workshop Steam Admission Locations Driven By Solar Technology Because parabolic trough systems are more mature commercially and technically. Trough Steam Admission Points: • LP, Cold Reheat, HP Steam Between Evap and Superheater Power Tower Steam Admission Points: • Could be same as trough, but also allows higher temperature admissions to Hot Reheat or Main Steam Compact Linear Fresnel Reflector • LP, Cold Reheat

15. Eskom CSP Workshop Steam Admission Locations Driven By Solar Technology… … but when it is being integrated into an existing facility, by the characteristics / capabilities of the existing steam cycle and equipment can become overriding considerations

16. Eskom CSP Workshop Typical Feedwater Extraction Locations Extraction point can impact the feedwater temperature further influencing the size of the solar field Boiler Feed Pump (BFP) Discharge HP Economizer Exit with Booster Pump (A unique booster pump may be needed to overcome the additional pressure drop on the HTF water / steam side)

17. Eskom CSP Workshop Feedwater From BFP Discharge + HP Steam Admission used in this case Main Steam Steam Turbine Solar Field / Solar Power Block HP IP / LP Air-Cooled Condenser Duct Firing HP Steam Fuel H P S H R H H P E V H P E C H P E C I P S H I P E V H P E C I P E C L P S H L P E V L P E C Air Gas Turbine BFP Discharge Heat Recovery Steam Generator BFP

18. Eskom CSP Workshop Representative Solar Steam Generator Outline Steam Out Steam Out HTF out Other configurations are available, including vertical orientations The vessel shown is ~ 15 meters long, 3 meters in diameter In this design there were (3) vessels for each GT / HRSG grouping; • Preheater • Steam generator (this vessel) • Superheater HTF in

19. Eskom CSP Workshop Solar Resource Intermittency Thermal lag time in solar fields is large, 30 minutes or more, due to the large volume of Heat transfer fluid (HTF) and variable HTF flow Cloud cover events result in changing HTF flow as the solar field responds to control HTF outlet temperatures As areas of the solar field see varying levels of cloud cover and the duration of the cloud passage is a variable, the degree the power plant output is impacted is dependant on the magnitude of these events Plants operating in regions with frequent cloud cover should consider these impacts into the design to mitigate operational impacts and to maximize daily solar utilization

20. Eskom CSP Workshop Impact of Cloud Cover on Solar Steam Generation (SSG) Operation These events can lead to a shut-off of the solar steam generator train(s) (SSGs) if the HTF temperature falls near or below the saturation temperature of the steam supply generator (SSG) evaporators Unlike stand-alone solar plants, the steam pressure of the SSG is driven by the operating load of the CC plant CTGs, not the amount of steam that could be produced if the evaporator was free to slide in pressure

21. Eskom CSP Workshop Martin Next Generation Solar Energy Center Array includes 6,864 Units 192,000 Mirrors Covers approximately 202 ha

22. Solar Integration with Coal / Oil Steam Plants

23. Eskom CSP Workshop Typical Steam Plant Generic Schematic Steam Turbine Hot Reheat Main Steam Steam Generator (BOILER) HP Generator IP/LP Cold Reheat Condenser Final Feedwater Deaerator BFP Condensate Pump LP FW Heaters HP FW Heaters

24. Eskom CSP Workshop Potential Injection Points for Solar-Sourced Thermal Energy CONFIGURATIONS CAN INCLUDE THE FOLLOWING, ALONE OR IN COMBINATION Feedwaterheating - External heating Feedwater heating – Provide heating steam Generation of Cold Reheat Steam Generation of Hot Reheat Steam Generation of HP steam Generation of Main Steam

25. Eskom CSP Workshop Steam Admission Locations Driven By Solar Technology Criteria used in the selection of the solar technology used in a specific plant should include not only the capabilities of the candidate technology, but the steam cycle and characteristics of the existing steam cycle Candidate Trough Steam Admission Points: • Feedwater Heating, LP, Cold Reheat, HP Steam Between Evap and Superheater Candidate Power Tower Steam Admission Points: • Could be same as trough, but also allows higher temperature admissions to Hot Reheat or Main Steam Candidate Compact Linear Fresnel Reflector • Feedwater Heating, LP, Cold Reheat

26. Eskom CSP Workshop External Feedwater Heating Steam Turbine Main Steam Hot Reheat Steam Generator HP IP / LP Cold Reheat Air-Cooled Condenser Final Feedwater Deaerator Solar Field / Solar Feedwater Heaters BFP Condensate Pump LP FW Heaters HP FW Heaters

27. Eskom CSP Workshop Generation of HP Steam HP Steam to HP Superheater Steam Turbine Main Steam Hot Reheat Steam Generator HP IP / LP Cold Reheat Air-Cooled Condenser Final Feedwater Deaerator Solar Field / Solar Steam Generators BFP Condensate Pump LP FW Heaters HP FW Heaters

28. Eskom CSP Workshop Summary Hybrid Solar thermal has been applied on large scale basis at an existing combined cycle facility The concept has proven to be operationally acceptable Application at existing coal or oil-fired facilities is technically feasible Designs must consider the steam cycle, where addition of solar generated energy is physically possible, as well as the required temperature and pressure requirements of the cycle