concentrated solar power course - session 2 : parabolic trough

March 2010

Manuel Silva

Seville University

CSP TrainingLesson 2: Parabolic Trough

See also CPV

CONCENTRATING PHOTOVOLTAICS

Advantages, Interviews, Video

CONCENTRATING PHOTOVOLTAICS

Advantages, Interviews, Video

http://www.leonardo-energy.org/concentrating-photovoltaics

http://www.leonardo-energy.org/concentrating-photovoltaics

Solar Thermal Power Plants. Parabolic Trough Technology

Manuel A. Silva PérezGroup of Thermodynamics and Renewable

EnergyETSI – University of Seville

[email protected]://www.leonardo-energy.org/csp-training-course-lesson-2-linear-focus-technologies

http://www.leonardo-energy.org/csp-training-course-lesson-2-linear-focus-technologies

4

Main Concentrating Technologies

Central Receiver / Heliostats

Parabolic troughs

Parabolic dishes

Linear Fresnel Reflectors



5http://www.leonardo-energy.org/csp-training-course-lesson-2-linear-focus-technologies


6

Solar Thermal Power Plant. Basic configuration

Beam irradiance

Concentrator

Receiver

Thermal Storage

Concentrated irradiance Electricity

Power conversion system

Thermal energy

BoilerFossil fuel Biomass

Generator



7

PT power plant configuration



8

Collector



9

Collector



10

Main elements of the collector

• Reflector (mirror)• Receiver tube• Structure• Tracking system• Connecting elements• Control system



11

Applications

Process heat STP plant



12

The reflector

Thin glass mirror (0.8 mm)

Thick glass mirror (3 -5 mm)



13

Alternative reflecting surfaces

AluminumAlanod

Reflective films (polymers)Reflectech, 3M



14

Structure



15

Receiver tube

Selective coated steel tube

Glass envelope

'Getter‘ for vacuum maintenanceExpansion bellow

Glass pin for evacuation of gasesVacuum between glassand steel tubes

Glass – metal welding



16

Receiver tubes

Schott PTR-70Solel UVAC-2 y UVAC-

3



17

Heat transfer fluid

• Thermal oils– Caloria (SEGS I and II,

<300ºC)– Therminol VP-1 (<400 ºC)– Syltherm (Dow Chemical,

>400ºC)• Water / Steam

– >400 ºC– DISS Project

• Molten salts– Archimedes - ENEA facility

• Gasses– PSA Research Facility

State of the art



18

Tracking mechanisms

Electrical motor - gearbox Hydraulic



19

Connecting collectors

Flex hoses Rotating joints



20

Solar field configuration (I)

1 SCA 150 m 12 SCE 1 Drive Pylon 10 Middle Pylon 1 End Pylon 1 Shared Pylon (shared with next SCA)

Cold Oil

Hot Oil

End Pylon

Drive Pylon

Middle Pylon

Shared Pylon

SCE

150 m

150 m



21

Solar field configuration (2)

Cross OverPipes

1379 m

1248

m

Loop of6 SCA’s

HeadersSEGS Power Block80 MW Rankine Cycle



22

A) Direct returnB) Reverse return

C) Central

Thermal losses Higher cost P balanced Lower consumption

Thermal losses unbalanced P Higher consumption

Shorter pipelines Better access to collectors unbalanced P

Solar field configuration (3)



23

X

Y

N

SE

O

Z

S

C

Sol

X

YN

SE

O

Z

S

C

Sol

b) N-S trackinga) E-W tracking

Solar field orientation (Northern Hemisphere)

Maximum efficiency at noon.

Maximum yearly energy generation

Incidence angle never 0 at noon

More balanced seasonal generation



24

Diámetro , D

Rayosolar

Angulodeapertura, f

Angulodeaceptancia, qReflectorParabolic

External receiver diameterD

Sun rays

Aperture angle f

Acceptance angle, q

b) Acceptance angle, a) Concentration ratio, C

Aperture, A

Absorber tube

Basic design parameters

Length, L



25

Beam irradiance

interception factor, ,

Selective-coated steel tube (Absortivity = )

Glass envelope (Transmissivity = )

Parabolic mirror(Reflectivity = )

o,peak = ···

Energy balance. Optical losses



26

Sun

Sun

Side view

Plant view

Shaded area

Reflecting surface

Absorber tube

L = concentrator length = incidence angle

F = focal length

Sol

F

ED

L

b) Loss of effective collector lengtha) Shading losses

Af = W x ED = W x F x tan()

Geometrical losses



27

Loss of effective collector length

W

ED



28

ambabsabs

conv-condabs,radabs,absL T - TLD

Q + Q=U

[W/m2

abs ºC]

UL)col = UL)abs / C

Qv,abs.

Qabs,rad.

Qabs,cond/conv. Qamb,rad

Qamb,conv

Glass envelope

Absorber tube

Thermal losses



29

effeff

cos IAQ csol inouteff hhMQ thoptglobal K º0,

Energy balance (solar to thermal)



30

95

96

97

98

99

100

Avail

ab

ilit

y -

%

1995 1996 1997 1998 1999

III IV V VI VII0%

10%

20%

30%

40%

50%

60%

70%Effi

cie

ncy [

%]

0

200

400

600

800

1000

1200

Dir

ect

Norm

al R

ad

iati

om

[W

/m²]

05:00 07:00 09:00 11:00 13:00 15:00 17:00 19:00 21:00

Solar to Electric Efficiency (gross)

Direct Normal Radiation

Thermal SolarField Efficiency -

Solar Efficiencies Measured at SEGS VIon July 1997 by KJC Operating Company

Typical operation curve (clear day, no thermal storage)



31

Andasol-type plants (thermal storage and auxiliary boiler)



32

SEGS 30 MW



33

Costs

• Difficult to evaluate– Confidentiality of contracts– Volatility of prices– Only 2 – 3 providers of key elements– O&M experience restricted to US (SEGS

Plants)



34

Costs (w/o TES)

Approx. 3.5 – 4 €/kWe



35

Costs – Solar field



36

Electricity cost

• Depends on different factors– Solar Resource– TES Capacity– Labour cost– Financial– Etc.

• Spain 2010: LCOE < 250 €/MWh• SW USA: LCOE = 120 €/MWh?



37

PT Technology today, pros & cons.

• Pros:– Mature technology;

• Comercially proven, over 500 MW installed capacity;

• Extensive operational record: 9 plants operating for 20 years in USA

– Easy to finance (in Spain!)• Cons:

– Few manufacturers of key elements (recievers, mirrors…) -> limited competence

– Limited maximum temperature -> limited efficiency

– Costly, hazardous HTF– Limited TES options



38

More…

• http://www.nrel.gov/csp/troughnet/• Sargent & Lundy Assessment of CSP

http://www.nrel.gov/csp/troughnet/pdfs/34440.pdf

• Look for movies at youtube, e.g:– http://www.youtube.com/watch?v=ysDXwvN

GHeM&feature=related– http://www.youtube.com/watch?v=3OLjooHY

1VA– http://www.youtube.com/watch?v=mDWSW

8BAM3U&feature=related– And more…


http://www.nrel.gov/csp/troughnet/



http://www.youtube.com/watch?v=ysDXwvNGHeM&feature=related

http://www.youtube.com/watch?v=ysDXwvNGHeM&feature=related

http://www.youtube.com/watch?v=3OLjooHY1VA

http://www.youtube.com/watch?v=3OLjooHY1VA

http://www.youtube.com/watch?v=mDWSW8BAM3U&feature=related

http://www.youtube.com/watch?v=mDWSW8BAM3U&feature=related


concentrated solar power course - session 2 : parabolic trough

Technology

solar field configuration

solar thermal power

thermal losses

structure http

receiver tubeselective

w x ed

mmthick glass mirror

reflectorthin glass