Parabolic dishes * general description * main elements: parabolic concentrator, structure and tracking system, receiver, stirling engine and generator * state of the art: types of dish-stirling systems; operational aspects; performance and economy * future developments Central receiver systems * general description * main elements: heliostat, tower, receiver, power conversion system * state of the art: technology options; operational aspects; performance and economy * future developments

1. Concentrated Solar Thermal Power
Technnology Training
Session 3 – Point Focus Technologies
By Manuel A. Silva Pérez
silva@esi.us.es
April 14, 2010
http://www.leonardo-energy.org/csp-training-course-5-lessons

2. Session 3.
Point Focus Technologies:
Parabolic Dish
and
Central Receiver Systems
Manuel A. Silva Pérez
silva@esi.us.es
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

3. Central Receiver Systems ‐ CRS
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

4. Solar Thermal Power Plant.
Basic configuration
Beam irradiance
Concentrator
Concentrated irradiance
Electricity
Receiver
Thermal energy
Thermal
Storage
Power conversion
system
Fossil fuel Biomass Boiler
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

5. Central Receiver System
http://www1.eere.energy.gov/solar/power_towers.html

6. 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
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

7. Heliostat
Incident ray
Reflected ray
Back support
structure
Elevation drive Reflecting surface
Azimuth drive
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

8. Glass – metal heliostat
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

9. Glass – metal heliostat
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

10. Glass – metal heliostats
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

11. Stretched membrane heliostats
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

12. Stretched membrane heliostats
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

13. Heliostat field layout
• Surrounding field
• North (south) field
• Secondary concentration
• Secondary concentrator optics tower (SCOT)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

14. North field
1000
800
600
400
200
0
-600 -400 -200 0 200 400 600
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

15. Surrounding field
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

16. Geometrical performance of heliostats
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

17. Cosine factor
Yearly average cosine factor for a
north heliostat field
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

18. Reflectivity
• Reflectivity of a new, clean mirror ≈ 0.90 ÷ 0.94

19. Shading and blocking
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

20. Atmospheric attenuation
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

21. Spillage
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

22. CRS – Receiver
• Function: to receive concentrated solar radiation and
transform it to thermal power (enthalpy increase of
the working fluid)
• Components
– (Tower)
– (Cavity)
– Absorber
– Supporting Structure
– (Other auxiliary elements: Steam drum, recirculation
pumps...)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

23. Types of receivers for CRS plants
External Cavity
Working fluid Working fluid
Volumetric (Fluidized bed)
Absorber Solid particles
Air intake
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

24. Cavity
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

25. Molten salt cavity receiver
4.5 MWt molten salt receiver tested under a cost shared program with US utilities and industry.

26. External, cylindrical
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

27. External, cylindrical receiver
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

28. Receiver – working fluids
• Water / Steam
• Air
• Molten salts
• Sodium
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

29. CRS (PS10, sat. steam)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

30. PS10 and PS20 (Abengoa Solar, Spain)

31. CRS (Gema Solar, Molten salts)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

32. Gema Solar (Torresol Energy, Spain)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

33. Gema Solar
Design 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

34. CRS: Pros and cons.
• Pros:
– Ability to achieve high temperatures
– Wide industrial base for most components
– Many technological options
– Technologically proven
– Multiple thermal storage opptions
– Great potential for improved efficiency and/or cost reduction
• Cons.:
– Complexity
– Short commercial record
– Still inmature?
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

35. Sierra Solar (e‐Solar, USA)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

36. Unit #1 (100 kW hybrid GT) (Aora Solar, Israel)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

37. Parabolic dishes

38. Parabolic dish systems
• Combine a paraboloidal concentrator (parabolic dish) with a
Power Conversion Unit (PCU) directly attached to the
concentrator
MDAC ('83-'88) Boeing/SES
• Types of PCU (‘98-’99)
– Gas Turbines Advanco ('82-'85)
– Direct Steam Generation
– Stirling Engine SBP/Almeria
('88-'99)
SBP/Solo
Cummins
('89-'96)
SAIC/STM

39. Solar Village (Arabia Saudí)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

40. Parabolic dish ‐ Direct Steam Generation
Dish collector field at Shenandoah, GA
• Industrial process heat project.
• 7 meters in diameter,
• aluminized film reflector
Heat from the field was used in a textile plant for air
conditioning and process heat.

41. Parabolic dish – Stirling engine experiences
(source: Mancini et al. JSEE 2003)

42. Parabolic dish – Stirling engine
•High performance
– High concentration ratio
– High temperature
– Modularity
– No water consumption
• Costes todavía por encima de la
fotovoltaica
• Reto en la reducción de O+M
• Durabilidad del grupo receptor/motor
10-kW EuroDish
SBP/Solo-PSA

43. Dish – Stirling systems. Main elements
• Structure
• Concentrator
• Tracking system
• PCU
• Control
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

44. Structural optical surface
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

45. Space frame structures

46. Stretched membrane

47. Glass mirror‐faceted
• Spherically curved mirrors
• Individually alignable
• Parabolic shaped structure
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

48. Full surface paraboloid
• The entire surface forms a
paraboloid
• Usually made of a number
of ‘petals’
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

49. Stretched membrane. Single facet
• Membrane
– Preshaped (vacuum not
enough)
– Thin reflective plastic
– Thin metal sheet + reflective
surface

50. Stretched membrane ‐ multifaceted
• Avoid the need for
preshaping
• Difficult alignment

51. Polar tracking
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

52. Elevation ‐ azimuth tracking

53. Receiver
• Absorbs concentrated solar energy and converts it
to thermal energy that heats the working fluid
(gas) inside the engine.
– External (low temp.)
– Cavity (high temp.)
– Directly illuminated
tubes
– Reflux
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

54. Directly illuminated tubes receiver
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

55. Reflux receiver
• Intermediate heat transfer fluid
• Decouple receiver and engine
– Pool boiler. The absorbed surface is always immersed in
a liquid
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

56. Reflux receiver
• Heat pipe. A wick draws the liquid metal from a
small sump
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

57. Striling Engine
• The Stirling cycle
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

58. Stirling engines
• Kinematic
• Free piston
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

59. State of the art
• Most efficient solar to electric technology.
• Pre‐commercial experiences
– Increase reliability
– Reduce costs
• Three main manufacturres / systems today
– Tessera Suncatcher (SES) 25 kW
– Cleanergy / SBP Eurodish 10 kW
– Infinia Corp 3 kW
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

60. Tessera Suncatcher
http://www.tesserasolar.com/
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

61. Infinia
http://www.infiniacorp.com/
• 3 kW Free piston engine
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

62. Infinia
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

63. Eurodish
sbp.de
• 10 kW kinematic Stirling engine (SOLO V161)
• 8.5 m diameter concentrator
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems

64. Tessera – SES Maricopa Solar Plant (AZ, USA)
http://www.leonardo-energy.org/csp-training-course-lesson-3-point-
focus-technologies-dish-stirling-and-central-receiver-systems