CSP Parabolic Trough Technology for Brazil A comprehensive documentation on the current state of the art of parabolic trough collector technology

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CSP Parabolic Trough Technology for Brazil

A comprehensive documentation on the current state of the

art of parabolic trough collector technology

13.03.2014

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Content

13.03.2014

1. Introduction

1.1. History

1.2. Aspects for Parabolic Trough Design

2. Overview on Parabolic Trough Collectors

2.1. First Commercial Collector Generation

2.2. Currently Available Parabolic Trough Collectors 2.3. Recent Collector Developments

3. Financial Parameters

3.1. Levelized Cost of Electricity

3.2. Comparison of Parabolic Trough Power Plants

4. Technological Developments

4.1. General Trends

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Introduction

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In 45 minutes, the sun sends more energy to the earth than humans consume in an entire year. With solar power plants more power can be generated on only 1% of the earth’s deserts than fossil fuels produce globally today. The future belongs to whoever succeeds in using these reserves effectively and profitably. Investing here is investing in the market of the future. Our future energy supply must be based on the use of renewable energies. Solar power plants make a valuable contribution to a sustainable and climate-friendly generation of energy.

Concentrating Solar Power (CSP) allows to convert the existing solar energy into dispatchable electricity.

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4 342 4,245

707

Projects under construction, commissioning or operational

Dish

Fresnel

Parabolic Trough

Power Tower

Source: CSP Today Global Tracker, December 2013 Source: CSP Today Global Tracker, December 2013

Technology split of global CSP projects under construction, commissioning or already operational as of Dec. 2013.

 Parabolic Troughs are the single most important technology used.

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Seite 5 Comparison of CSP Technologies 13.03.2014 Implemented by An d a s o l / Sp a in Sa u d i Ar a b ia St u tt g a rt 500 m from tower towards pole 500 m from tower towards equator 500m East/West Tower Height 180 m Dish Stirling Parabolic Trough Tower Fresnel Br a z il C a li fo rn ia

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Solar Irradiance and LCOE

13.03.2014 0,00 € 0,05 € 0,10 € 0,15 € 0,20 € 0,25 € 0,30 € 0,35 € 1500 1750 2000 2250 2500 2750 3000 3250 LC O E [€ /k W h] DNI [W/(m^2 * a)]

LCOE and direct normal iradiance (DNI)

design output: 50 MW storage: 6 h

O&M and insurance: 3 % of total investment Operation time: 25 years

Interest Rate : 8 %

Brazil:

 Direct Normal Irradiation (DNI) at a high level.

 Higher DNI leads to lower

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Content

13.03.2014

1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

3. Financial Parameters

4. Technological Developments

4.1. General Trends

4.2. Further Cost Reduction Potential

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History

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early 20th century

• First 45 kW parabolic trough collector plant by Shuman and Boys

80ies

• First commercial parabolic trough power plants in the Mojave Dessert in California (SEGS)

2004

• Introduction of feed in tariff (FIT) by the Spanish government

2008

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Andasol Plants (2009)

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Content

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1. Introduction

1.1. History

1.2. Aspects for Parabolic Trough Design

2. Overview on Parabolic Trough Collectors

3. Financial Parameters

4. Technological Developments

4.1. General Trends

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Seite 11 Principle of a Solar Parabolic Trough Power Plant

 The trough is tracking the sun on a single axis (elevation axis)

 Direct radiation is focused on an absorber tube

 A heat transfer fluid is pumped through the absorber tube and is heated up

 Steam is produced and runs a turbine

 Heat is stored in storage tanks to produce electricity on demand

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Parabolic trough power plant functional principle

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Pros and cons of parabolic troughs

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Pros

 short distance between reflector and absorber tube

 low energy losses

 delivers dispatchable energy  proven technology

 bankable

 lower part costs  lower LCoE  low area demand

 low energy losses  easy to scale

 10 MW to 250 MW

Cons

 limited operation temperature (by heat transfer fluid)

 higher cosine losses than dish  even terrain required

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Supporting Structure

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Torque Tube

Torque Box

Space Frame

Steel Aluminum

+ high stiffness and strengths + low thermal expansion -- high mass

+ low mass -- low stiffness

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Genealogy of parabolic trough collectors

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Content

13.03.2014

1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

2.1. First Commercial Collector Generation

3. Financial Parameters

4. Technological Developments

4.1. General Trends

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Seite 17 LS-2:

- torque tube design

- able to achieve good optical accuracy - easy to assemble

- good optical performance - high costs

- aperture width: 5 m - SCE: 7.8 m

- SCE per SCA: 6 - SCA length: 47 m

LS-3:

- Space frame truss design - 2x as long and larger aperture - inadequate torsion stiffness - cost savings not demonstrated - lower optical performance - aperture width: 5.76 m - SCE: 12 m

- SCE per SCA: 8 - SCA length: 96 m

First commercial collector generation

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Content

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1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

2.2. Currently Available Parabolic Trough Collectors

2.3. Recent Collector Developments

3. Financial Parameters

4. Technological Developments

4.1. General Trends

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Euro Trough– Key figures

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Implemented by

Solar Collector Element (SCE)

 Structure: Torque boxes

 Length: 12 m

 Aperture width (gross): 5.76 m  Aperture area (net): 68 m²  HCE Diameter: 70 mm

Solar Collector Assembly SCA

 SCA: 12 SCE per SCA

 Length: 150 m  Aperture area: 816 m²

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Seite 20 SENERtrough:

- torque tube supported on sleeve bearings - stamped arms to support the reflector panels - most common collector today

- aperture width: 5.76 - SCE length: 12 m - SCA length: 150 m

ENEA collector:

- torque tube as main structure element - molten salt as heat transfer fluid

- reflector panels: special aluminum honeycomb facet with thin glass mirrors

- aperture width: 5.76 m - SCA length: 100 m

Currently available parabolic trough collectors

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Seite 21 Solargenix (SGX-2):

- used in Nevada Solar one, Nevada - extruded aluminum space frame - easy to assemble

- aperture width: 5 m - SCE length: 8 m - SCA length: 96 m

Currently available parabolic trough collectors

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Content

13.03.2014

1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

2.2. Currently Available Parabolic Trough Collectors

2.3. Recent Collector Developments

3. Financial Parameters

4. Technological Developments

4.1. General Trends

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Seite 23 HelioTrough:

- torque tube with constant stiffness along the whole collector

- reduced number of parts (mirrors, HCE etc.) - increased lifetime

- cost reduction of maintenance and assembly - improved optical efficiency

- aperture width: 6.78 m, - aperture area: 1263 m²

- SCE length: 19 m / SCA length: 191 m - developed by: sbp and Flagsol

Recent collector developments

Ultimate Trough:

- world´s largest collector

- peak optical efficiency of 82.7 % - truss toque box design

- continuous mirror surface - economic use of material

- high stiffness allows increased span of 24.5 m - aperture: 7.51 m, aperture area: 1716 m² - SCE length: 24.6 m, SCA length: 240 m - total solar field cost savings up to 20 %

- developed by: sbp, Flabeg (German consortium)

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SENERtrough-2:

- torque tube

- increased aperture width, collector element length and focal length

- drive pylon structure: vertical pipe

- aperture width: 6.87; aperture area: 1048 m² - SCE length: 13.2 m

- SCA length: 158 m

SkyTrough:

- aluminum space frame

- reflective polymer mirror film attached on an aluminum sheet instead of glass reflector panels - aperture width: 6 m; aperture area 656 m²

- SCE length: 14 m - SCA length: 115 m - developed by: Skyfuel

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Large Aperture Trough (LAT 73):

- aluminum space frame

- reflective polymer film on aluminum back sheet - aperture width: 7.3 m; aperture area: 1392 m² - SCE length: 12 m

- SCA length: 192 m

- developed by Gossamer Space Frames and 3M

Abengoa E2:

- steel space frame collector - aperture width: 5.76 m (LS-3) - SCA length: 125 m

- monolithic glass reflector panels

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Content

13.03.2014

1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

3. Financial Parameters

3.1. Levelized Cost of Electricity

4. Technological Developments

4.1. General Trends

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Levelized Cost of Electricity LCoE

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• Overall performance value

• Usually used to compare different options for power generation • Calculation:

Total investment costs incl. all expenses (e.g. O&M, taxes, insurance) divided by cumulated electric energy produced during the complete operational time

• Unit: € / kWh

• Parametric calculation to show the impact of the DNI on the LCOE (50 MW with 6 h storage)

Implemented by 0,00 € 0,05 € 0,10 € 0,15 € 0,20 € 0,25 € 0,30 € 0,35 € 1500 1750 2000 2250 2500 2750 3000 3250 LC O E [€ /k W h] DNI [W/(m^2 * a)]

LCOE and direct normal iradiance (DNI)

design output: 50 MW storage: 6 h

O&M and insurance: 3 % of total investment Operation time: 25 years

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Content

13.03.2014

1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

3. Financial Parameters

3.2. Comparison of Parabolic Trough Power Plants

4. Technological Developments

4.1. General Trends

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Comparison of parabolic troughs power plants

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Implemented by

50 MW 50 MW 100 MW 100 MW 200 MW 200 MW 6 h Storage w/o Storage 6 h Storage w/o Storage 6 h Storage w/o Storage

M€ 213 125 392 232 726 420 M€ 7 4 14 9 28 16 M€ 58 35 111 67 215 120 M€ 14 7 26 14 50 27 M€ 5 3 8 5 15 9 M€ 60 57 110 105 200 190 M€ 40 0 69 0 120 0 M€ 22 13 41 25 75 44 M€ 7 4 12 8 22 13 M€/MW 4 3 4 2 4 2 M€ 14 8 25 15 47 27 M€ 6 4 12 7 22 13 k€/MW/a 128 75 118 70 109 63 M€/a 20 12 37 22 68 40 €/kWh 0,108 € 0,111 € 0,098 € 0,102 € 0,094 € 0,095 € Total annual costs

LCOE Owner costs spec. Investments

annuity of investment costs O&M costs and insurance spec. O&M costs

HTF system (with HTF) other solar field costs power block

storage EPC costs

Investment costs

Earth works & Foundations Parabolic trough costs

For comparison, the LCoE for three plant sizes is calculated.

Boundary conditions:

• EuroTrough collector (established, reliable performance data) • solar irradiance (DNI): 2500 W/m²

• with and without thermal storage • operational period: 25 years

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Comparison of parabolic troughs power plants

13.03.2014 50 60 70 80 90 100 50 100 200 LC O E , n o rm a li ze d [% ] design output [MW]

LCOE (normalized ): impact of TES and up-scaling

without TES with TES

(LCOE normalized to 50MW design output and without TES)

LCoE can be reduced by

• power plant scale-up (parabolic trough collector scale-up not considered here) • integration of thermal storage (increased controllability, utilization of the turbine)

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Content

13.03.2014

1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

3. Financial Parameters

4. Technological Developments

4.1. General Trends

4.2. Further Cost Reduction Potential

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General trends: Cost reductions due to collector scale up

13.03.2014 EuroTrough, 510‘120 m² _{UltimateTrough}®_{, 466‘731 m²} 1‘500 m _1‘750_m 1‘ 05 0 m 1‘ 30 0 m

The Ultimate Trough®_{shows a cost reduction of about 20 to 25 % compared}

to the EuroTrough by:

 decreasing specific solar field cost [€/m²] by “going large”  increased of optical performance (8 %) by stress free mirror

attachment

Due to increased collector dimensions and optical performance one UT loop will have more than twice the thermal power compared with ET loop.

Header piping ET UT Ratio

north-south [m] 1'678 n/a

east-west [m] 6'840 3'757 55%

total [m] 8'518 3'757 44%

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Seite 33 13.03.2014

Implemented by

Significant cost reduction due to:

 Number of “loop specific parts” (drives, sensors, local control board, cabling, swivel joints, control & separation valves, loop

interconnection piping) significantly reduced by 50 to 60 %

 Less piping (material, installation, insulation)  Less heat transfer fluid  Lower installation,

commissioning and operation cost

Collector Type EuroTrough Ultimate

Trough® Ratio UT/ET

Aperture Width m 5.77 7.51 130%

SCE length m 12.0 24.5 204%

SCA per SCA # 12 10 83%

SCA length m 147.8 246.7 167%

Aperture Area / SCA m² 817.5 1,716.0 210%

Solar field m² 510,120 466,731 91,5%

Capacity (gross)

8 h storage MW 50 50 100%

Loops # 156 68 44%

SCE # 7,296 2,720 37%

Drives/ Sensors/ Controls # 608 272 45%

Pylon foundations # 7,800 2,992 38%

Swivel joint assemblies # 1,248 544 44%

Cross over pipes # 156 68 44%

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Cost

Reduction

by

20 - 25%

(Compared to the

currently available

EuroTrough

collector)

Large scale

 low specific cost [€/m²] for structure, civil works and assembly by “going large” - 7.5 m aperture (Ultimate Trough)

 significant reduction of parts with related cost savings  the amount of heat transfer fluid (HTF) is reduced by 25 %  overall solar field costs about 23 % less compared to

EuroTrough

 LCoE is decreased by about 11 % compared to EuroTrough

 Steel structure with low accuracy allows effective sourcing  Simplicity in assembly allows low skilled labor requirements and time efficiency

 Close to perfect - Intercept factor • 99.2 % @ 94 mm HCE • 97.5 % @ 70 mm HCE

 Optimized for molten salt systems for higher energy efficiency

High optical accuracy Innovative design

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Source: Riffelmann et al.,

„Performance of the Ultimate Trough Collector with Molten Salts as Heat Transfer Fluid”, SolarPACES 2012, Marrakesh, September 2012

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Seite 35 The Ultimate Trough collector is ready for molten salt operation:

 The higher concentration factor using a 70 mm receiver tube compensates the higher thermal losses at elevated temperatures while the intercept remains high at 97.5 %. This leads to a significantly higher thermal efficiency compared to troughs with a lower concentration ratio.

 Electrical isolation of HCE for impedance heating is available

 HCE supports suitable for higher expansion length due to elevated temperatures are available

The commonly available receiver diameter of 70mm is the optimum diameter for the Ultimate Trough high-aperture collector for use with molten salt. The graph shows that the maximum annual yield of a given power plant (120 MW gross output and 14 h of thermal storage, located in Daggett, U.S.) is highest for a receiver diameter of 70 mm.

Source: Riffelmann et al., „Performance of the Ultimate Trough Collector with Molten Salts as Heat Transfer Fluid”, SolarPACES 2012, Marrakesh, September 2012 Higher operating temperature Requires higher concentration ratio Requires higher optical performance 550 560 570 580 590 600 610 620 60 70 80 90 100 Ne t annua l e ner gy [ GWh ] HCE diameter [mm]

General trends: Cost reductions due to higher operation temperatures

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Seite 36 16,9 15,4 13,9 11,2 10,2 0 2 4 6 8 10 12 14 16 18 -9 % -10 % -20 % -10 %

- 40 %

LCoE Daggett [€-Cent/kWh] 13.03.2014

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Content

13.03.2014

1. Introduction

1.1. History

2. Overview on Parabolic Trough Collectors

3. Financial Parameters

4. Technological Developments

4.1. General Trends

4.2. Further Cost Reduction Potential

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Reflectors:

 significant cost reductions in glass mirror manufacturing  manufacturers increase accuracy and reflectivity

 anti-soiling coating reduce O&M costs

 new reflector concepts: reflecting film / composite facets

 larger structures allows for smaller solar fields  this significantly reduces number of parts

 cost savings (e.g. drives, pylons, sensors, controls)

 various drive concepts have been conceived and tested  hydraulic drives are the most cost efficient solution

 manufacturers increase production procedures due to competition

Drives and control: Metal support structure:

Further cost reduction potential

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Absorber tubes (HCEs):

 manufacturers increase production procedures due to competition  reduction of thermal losses by using new procedures

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Parabolic Trough technology is a proven technology with a long

track record. Performance and cost estimates for Parabolic

Trough technology are based on validated performance models

and build projects

It provides the production of dispatchable renewable energy at

currently lowest possible cost.

And yes, there is still room for improvement:

• There is still not enough development, testing, and

standardization. HTF technology, not only molten salt, is a

key to further cost reduction. The Ultimate Trough® is just

one step in the required direction

• The low deployment of the technology as of now allows

significant cost reductions through economies of scale in

future projects.

Conclusion

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Contact Details

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As a federal enterprise, GIZ supports the German Government in achieving its objectives in the field of international cooperation for sustainable development.

Published by

Deutsche Gesellschaft für

Internationale Zusammenarbeit (GIZ) GmbH Registered offices, Bonn and Eschborn, Germany

“CSP Parabolic Trough Technology for Brazil”

“Address of Programme here” T +55 61 2010-2070

E giz-brasilien@giz.de

I www.giz.de/brazil

Responsible

schlaich bergermann und partner, sbp sonne gmbh

Author(s)

Finn von Reeken, Sarah Arbes, Dr. Gerhard Weinrebe, Markus Wöhrbach, Jonathan Finkbeiner

Photo credits