By Manuel A. Silva Pérezsilva@esi.us.es

April 14, 2010

Concentrated Solar Thermal PowerTechnnology Training

Session 3 – Point Focus Technologies

http://www.leonardo-energy.org/csp-training-course-5-lessons

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

Central Receiver Systems  ‐ CRS

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

Solar Thermal Power Plant. Basic configuration

Beam irradiance

Concentrator

Receiver

Thermal Storage

Concentrated irradianceElectricity

Power conversion system

Thermal energy

BoilerFossil fuel  Biomass

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

Central Receiver System

http://www1.eere.energy.gov/solar/power_towers.html

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

Heliostat

Back support structure

Elevation drive

Azimuth drive

Reflecting surface

Reflected ray

Incident ray

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

Glass – metal heliostat

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

Glass – metal heliostat

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

Glass – metal heliostats

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

Stretched membrane heliostats

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

Stretched membrane heliostats

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

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

North field

0

200

400

600

800

1000

-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

Surrounding field

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

Geometrical performance of heliostats

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

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

Reflectivity

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

Shading and blocking

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

Atmospheric attenuation

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

Spillage

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

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

Types of receivers for CRS plants

External Cavity

Volumetric (Fluidized bed)

Working fluid Working fluid

Air intake

Solid particlesAbsorber

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

Cavity

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

Molten salt cavity receiver

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

External, cylindrical 

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

External, cylindrical receiver

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

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

CRS (PS10, sat. steam)

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

PS10 and PS20 (Abengoa Solar, Spain)

CRS (Gema Solar, Molten salts)

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

Gema Solar (Torresol Energy, Spain)

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

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

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

Sierra Solar (e‐Solar, USA)

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

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

Parabolic dishes

Parabolic dish systems

• Combine a paraboloidal concentrator (parabolic dish) with a Power Conversion Unit (PCU) directly attached to the concentrator

• Types of PCU– Gas Turbines

– Direct Steam Generation

– Stirling Engine

Advanco ('82-'85)

MDAC ('83-'88) Boeing/SES (‘98-’99)

SBP/Almeria('88-'99)

Cummins('89-'96)

SBP/Solo

SAIC/STM

Solar Village (Arabia Saudí)

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

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. 

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

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

SBP/Solo-PSA

10-kW EuroDish

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

Structural optical surface

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

Space frame structures

Stretched membrane

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

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

Stretched membrane. Single facet

• Membrane– Preshaped (vacuum not 

enough)

– Thin reflective plastic

– Thin metal sheet + reflective surface

Stretched membrane ‐multifaceted

• Avoid the need for preshaping

• Difficult alignment

Polar tracking

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

Elevation ‐ azimuth tracking

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

Directly illuminated tubes receiver

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

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

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

Striling Engine

• The Stirling cycle

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

Stirling engines

• Kinematic

• Free piston

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

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

Tessera Suncatcherhttp://www.tesserasolar.com/

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

Infiniahttp://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

Infinia

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

Eurodishsbp.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

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