August 2013
HYBRID SOLAR THERMAL INTEGRATION AT
EXISTING FOSSIL GENERATION FACILITIES
OF ENGINEERING,
KEVIN MILLER MANAGER
BLACK & VEATCH, SOUTH AFRICA
AGENDA
Solar Thermal Integration at Existing Rankine
Cycle Generating Facilities [HYBRID CSP]
Solar Integration with Coal / Oil Steam Plants
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CONCEPTS OF COMBINED BRAYTON / RANKINE
CYCLE GENERATION
Brayton Cycle
Rankine Cycle
Integrated Solar Combined Cycle adds steam to
the Rankine Cycle
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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
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Eskom CSP Workshop
August 2013
WHY CONSIDER HYBRID CSP?
• 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
More efficient with lower capitol cost
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Eskom CSP Workshop
August 2013
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
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Eskom CSP Workshop
August 2013
DIRECT NORMAL IRRADIATION (DNI)
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Eskom CSP Workshop
August 2013
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
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Eskom CSP Workshop
August 2013
MARTIN NEXT GENERATION
SOLAR ENERGY CENTER
Source; John Van Beekum for The New York Times
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Eskom CSP Workshop
August 2013
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
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Eskom CSP Workshop
August 2013
COMBINED CYCLE GENERIC LAYOUT
Main Steam
Steam Turbine
HP
IP / LP
Hot Reheat
Air-Cooled
Condenser
Cold Reheat
Duct
Firing
HP Steam
IP Steam
LP Steam
I
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Fuel
Air
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Gas Turbine
Heat Recovery Steam Generator
BFP
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Eskom CSP Workshop
August 2013
POTENTIAL SOLAR STEAM INJECTION
POINTS
• 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
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
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Eskom CSP Workshop
August 2013
STEAM ADMISSION LOCATIONS DRIVEN BY
SOLAR TECHNOLOGY
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)
Parabolic Trough Technology was selected by
the Client
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Eskom CSP Workshop
August 2013
STEAM ADMISSION LOCATIONS DRIVEN BY
SOLAR TECHNOLOGY
• 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
Because parabolic trough systems are more
mature commercially and technically.
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Eskom CSP Workshop
August 2013
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
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Eskom CSP Workshop
August 2013
TYPICAL FEEDWATER EXTRACTION
LOCATIONS
• 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)
Extraction point can impact the feedwater
temperature further influencing the size of the
solar field
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Eskom CSP Workshop
August 2013
FEEDWATER FROM BFP DISCHARGE + HP
STEAM ADMISSION USED IN THIS CASE
Main Steam
Steam Turbine
HP
IP / LP
Solar Field /
Solar Power Block
Air-Cooled
Condenser
Duct
Firing
HP Steam
Fuel
Air
H
P
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H
P
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H
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Gas Turbine
BFP Discharge
Heat Recovery Steam Generator
BFP
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Eskom CSP Workshop
August 2013
REPRESENTATIVE SOLAR STEAM
GENERATOR OUTLINE
Steam Out
Steam Out
HTF out
HTF in
• 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
Other configurations are available, including
vertical orientations
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Eskom CSP Workshop
August 2013
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
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Eskom CSP Workshop
August 2013
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
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Eskom CSP Workshop
August 2013
MARTIN NEXT GENERATION
SOLAR ENERGY CENTER
Array includes 6,864 Units
192,000 Mirrors
Covers approximately 202 ha
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SOLAR INTEGRATION
WITH COAL / OIL
STEAM PLANTS
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Eskom CSP Workshop
August 2013
TYPICAL STEAM PLANT GENERIC SCHEMATIC
Steam Turbine
Hot Reheat
Main Steam
Steam
Generator
(BOILER)
HP
IP/LP
Generator
Cold Reheat
Condenser
Final Feedwater
Deaerator
HP FW Heaters
BFP
LP FW Heaters
Condensate
Pump
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Eskom CSP Workshop
August 2013
POTENTIAL INJECTION POINTS FOR SOLARSOURCED THERMAL ENERGY
CONFIGURATIONS CAN INCLUDE THE FOLLOWING,
ALONE OR IN COMBINATION
• Feedwater heating - 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
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Eskom CSP Workshop
August 2013
STEAM ADMISSION LOCATIONS DRIVEN BY
SOLAR TECHNOLOGY
• 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
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
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Eskom CSP Workshop
August 2013
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
HP FW Heaters
BFP
LP FW Heaters
Condensate
Pump
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Eskom CSP Workshop
August 2013
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
HP FW Heaters
BFP
LP FW Heaters
Condensate
Pump
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Eskom CSP Workshop
August 2013
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
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