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SOLAR THERMAL POWER GEEN 4830 – ECEN 5007 Manuel A. Silva Pérez [email protected] 7. Central Receiver Systems
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SOLAR THERMAL POWERGEEN 4830 – ECEN 5007
Manuel A. Silva Pérez
7. Central Receiver Systems
Central Receiver Systems - CRS
14/7/101 GEEN 4830 – ECEN 5007
Solar Thermal Power Plant.
Basic configuration
Beam irradiance
Concentrator
Receiver
Thermal
Storage
Concentrated irradianceElectricity
Power
conversion
system
Thermal energy
BoilerFossil fuel
Biomass
14/7/102 GEEN 4830 – ECEN 5007
Central Receiver System
http://www1.eere.energy.gov/solar/power_towers.html14/7/103 GEEN 4830 – ECEN 5007
CRS (Gema Solar, Molten salts)
14/7/104 GEEN 4830 – ECEN 5007
CRS
(Phoebus, Open air volumetric receiver)
14/7/105 GEEN 4830 – ECEN 5007
Collector System (concentrator)
14/7/10GEEN 4830 – ECEN 50076
Heliostat field
The concentrator is the “heliostat field”, a Fresnel
concentrator
Main elements
Heliostat
Control System
14/7/10GEEN 4830 – ECEN 50077
The heliostat
“an instrument consisting of a mirror mounted on an axis moved by clockwork by which a sunbeam is steadily reflected in one direction”
Basic components
Reflecting surface
Structure and tracking mechanism
Control system
Typology:
Glass - metal
Stretched membrane
Size: 1 m2 to 150 m2
14/7/108 GEEN 4830 – ECEN 5007
Heliostat
Back support
structure
Elevation drive
Azimuth drive
Reflecting surface
Reflected ray
Incident ray
14/7/109 GEEN 4830 – ECEN 5007
Burning mirror, Hoesen (18th century)
14/7/1010 GEEN 4830 – ECEN 5007
Glass – metal heliostat
14/7/1011 GEEN 4830 – ECEN 5007
Heliostat
14/7/1012 GEEN 4830 – ECEN 5007
Glass – metal heliostat
14/7/1013 GEEN 4830 – ECEN 5007
Glass – metal heliostats
14/7/1014 GEEN 4830 – ECEN 5007
Stretched membrane heliostats
14/7/1015 GEEN 4830 – ECEN 5007
Stretched membrane heliostats
14/7/1016 GEEN 4830 – ECEN 5007
Stretched membrane heliostats
14/7/1017 GEEN 4830 – ECEN 5007
Reflectivity
Reflectivity of a new, clean mirror ≈ 0.90 ÷ 0.94
14/7/1018 GEEN 4830 – ECEN 5007
Mirror quality
Heliostat facets are spherically curved
For large focal distances, a parabolic surface can be approximated by
an spherical surface of radius r = 2f (f: focal distance).
14/7/10GEEN 4830 – ECEN 500719
Mirror quality
2222
cspSD
Ideal spherical curvature
Spherical curvature, with waviness
2222
cspSD
14/7/1020 GEEN 4830 – ECEN 5007
Distortion
Spherical reflectors generate distortion of the image
Dependent on time (relative position sun-heliostat)
14/7/10GEEN 4830 – ECEN 500721
Summer solstice, noon
Summer solstice, 7:30 a.m. Summer solstice, 7:30 p.m.
Heliostat field layout
Surround field
North (south) field
Secondary concentration
Secondary concentrator optics tower (SCOT)
14/7/1022 GEEN 4830 – ECEN 5007
North field
0
200
400
600
800
1000
-600 -400 -200 0 200 400 600
14/7/1023 GEEN 4830 – ECEN 5007
Surrounding field
14/7/1024 GEEN 4830 – ECEN 5007
Geometrical performance of heliostats
14/7/1025 GEEN 4830 – ECEN 5007
Cosine factor
Yearly average cosine factor for a
north heliostat field
14/7/1026 GEEN 4830 – ECEN 5007
Shading and blocking
14/7/1027 GEEN 4830 – ECEN 5007
Shading & blocking
Shading
Blocking
Air transmittance
14/7/1028 GEEN 4830 – ECEN 5007
Air transmittance
Spillage
14/7/1029 GEEN 4830 – ECEN 5007
Receiver system
Function
Components
Types of receivers
Working fluids
14/7/10GEEN 4830 – ECEN 500730
Receiver system
14/7/1031 GEEN 4830 – ECEN 5007
Receiver types
14/7/1032 GEEN 4830 – ECEN 5007
Cavity receivers
14/7/10GEEN 4830 – ECEN 500733
Cavity receivers
14/7/10GEEN 4830 – ECEN 500734
Molten salt cavity receiver
14/7/10GEEN 4830 – ECEN 500735
External, cylindrical receiver
14/7/10GEEN 4830 – ECEN 500736
External, cylindrical receiver
14/7/10GEEN 4830 – ECEN 500737
External, cylindrical receiver
14/7/10GEEN 4830 – ECEN 500738
Tubular receiver (boiler)
14/7/1039 GEEN 4830 – ECEN 5007
Volumetric receivers
14/7/10GEEN 4830 – ECEN 500740
Volumetric receivers
14/7/10GEEN 4830 – ECEN 500741
Heat transfer characteristics of tubular and
volumetric receivers
14/7/10GEEN 4830 – ECEN 500742
Detail of a volumetric absorber (wire mesh)
14/7/10GEEN 4830 – ECEN 500743
Detail of a volumetric absorber
(ceramic cups)
14/7/10GEEN 4830 – ECEN 500744
Working fluids
14/7/10GEEN 4830 – ECEN 500745
Working fluids for CRS
Water / steam
Saturated steam
Superheated steam
Molten salts
Air
Pressurized
Atmospheric
Sodium
Thermal oils
14/7/10GEEN 4830 – ECEN 500746
Comparison of HTF’s
14/7/10GEEN 4830 – ECEN 500747
Power conversion system
Rankine cycle (steam turbine)
Brayton cycle (gas turbine)
Combined cycle (gas turbine + steam turbine)
Stirling engines
(MHD)
14/7/10GEEN 4830 – ECEN 500748
CRS: pros and cons.
Pros:
Ability to achieve high temperatures
Wide industrial base for most components
Multiple technological options
Technologically proven
Multiple thermal energy storage options
High potential for improved effciency or cost reduction
Cons.:
Complexity
Short commercial record
Best technology still undefined
14/7/10GEEN 4830 – ECEN 500749
Energy Balance of Central Receiver
Systems
14/7/10GEEN 4830 – ECEN 500750
High concentration concepts
Secondary concentration
Increase flux density on the absorber
Reduce requirements for primary concentrator (heliostats)
Secondary Concentrator Optics Tower
The receiver can be placed at the ground level
Solar Furnaces
Very high concentration ratios
Combine a field of flat heliostats and a parabolic concentrator
Not for electricity generation
14/7/10GEEN 4830 – ECEN 500751
Secondary concentrators
REFOS Project (DLR)
14/7/10GEEN 4830 – ECEN 500752
SCOT (Secondary Concentrator Optics
Tower)
Weizmann Institute (Israel)
14/7/10GEEN 4830 – ECEN 500753
SCOT (Secondary Concentrator Optics
Tower)
14/7/10GEEN 4830 – ECEN 500754
Beam Down
14/7/10GEEN 4830 – ECEN 500755
Solar Furnaces
14/7/10GEEN 4830 – ECEN 500756
Solar Furnaces
14/7/10GEEN 4830 – ECEN 500757
CRS projects
14/7/10GEEN 4830 – ECEN 500758
CRS (PS10, sat. steam)
14/7/1059 GEEN 4830 – ECEN 5007
PS10 and PS20 (Abengoa Solar, Spain)
14/7/1060 GEEN 4830 – ECEN 5007
CRS (Gema Solar, Molten salts)
14/7/1061 GEEN 4830 – ECEN 5007
Gema Solar (Torresol Energy, Spain)
14/7/1062 GEEN 4830 – ECEN 5007
Gema SolarDesign Data
Total Reflective Area 285.200 m2
Number of heliostats 2480
Total Area covered by Heliostat Field 142.31 Ha
Thermal output of the Receiver 120 MWt
Tower height 120 m
Heat Storage Capacity (equivalent to turbine operation) 15 hours
Steam Turbine power 17 MWe
Natural Gas Thermal Power 16 MWt
Projected Operative Figures
Direct solar radiation over Heliostats 2062 kWh/m2
Annual Energy sales 96.400 MWhe
Contribution of Natural Gas 15%
Capacity utilization 65 %
CO2 savings 23.000 – 85.000 t/y
14/7/1063 GEEN 4830 – ECEN 5007
Sierra Solar (e-Solar, USA)
14/7/1064 GEEN 4830 – ECEN 5007
Unit #1 (100 kW hybrid GT) (Aora Solar,
Israel)
14/7/1065 GEEN 4830 – ECEN 5007
