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International Workshop on:

DESIGN OF SUBSYSTEMS FOR CONCENTRATED SOLAR POWER TECHNOLOGIES19-22 December 2013. Jodhpur (India)

Direct Steam Generation

CIEMAT-Plataforma Solar de Almería

E-mail: [email protected]

Eduardo Zarza MoyaLoreto Valenzuela Gutiérrez

International Workshop: “Design of Subsystems for CSTP Technologies”19-22 December 2013, Jodhpur (India)

Contents

Advantages and disadvantages of the DSG process

Current status of the DSG technology


Introduction


Contents




Introduction


Steam Production with Linear Solar Concentrators

a) using a Heat Transfer Fluid

So

lar

Fie

ld

Steam

Generator

Feed pump

Oil expansion

tank

T1 T2

T1 T2 + 10 K

Process

T1 T2

T1 T2 + 10 K

Steam

Liquid water

b) with Flashing

Flash tank

Water

recirculation

Expansion

valve

P1P2P1>>P2

Feed water

pump

P1P2>>P2

Saturated steam

Liquid water

So

lar

Fie

ld

Process



c) with Direct SteamGeneration (DSG)

Feed water

pump

Steam

Liquid waterS

ola

r F

ield

Process


Different sections in the rows of a DSG solar field

Solar Radiation

2L 3L1L

To

Po


m

Preheating SperheatingEvaporation


vl = m · (1-x) / (Atubo · l)

vg = (m · x) / (Atubo · g)

Two-phase Flow Pattern Map

for an horizontal pipe

0,01

1

1

0,1

0,1

0,001

0,01

10

10

100Sp

erf

icia

lli

qu

id v

elo

cit

y /

(m

/s)

Superficial steam velocity / (m/s)

Annular

Intermittent

Estratified

Bubbly



Feed water

pump

Steam

Liquid water

So

lar

Fie

ld

Process


Two different “Bubbly” configurations

Disperse-Bubbly Flow


A

A’

A

A’

A

A’

A

A’

A

A’ Sección A-A’

A

A’ Sección A-A’

Foggy-Bubbly FlowSection A-A’

Section A-A’


Slow-Intermittent Flow

Plug-Intermittent Flow

Section A-A’

Section A-A’

A

A’

A

A’

A

A’

A

A’

A

A’

A

A’

A

A’

Two different “Bubbly” configurations



vl = m · (1-x) / (Atubo · l)

vg = (m · x) / (Atubo · g)

Two-phase Flow Pattern Map

for an horizontal pipe

0,01

1

1

0,1

0,1

0,001

0,01

10

10

100Sp

erf

icia

lli

qu

id v

elo

cit

y /

(m

/s)

Superficial steam velocity / (m/s)

Annular

Intermittent

Estratified

Bubbly



Feed water

pump

Steam

Liquid water

So

lar

Fie

ld

Process


The Three Basic DSG Processes

Once-Through Boiler

Lowest Costs

Least complexity

Best Performance

Controllability ?

Flow Stability ?

T

u

r

b

i

n

e

Feed pump

Solar Collectors

Injection Process

Better Controllability

Flow stability equally good

More complex

Higher investment costs

T

u

r

b

i

n

e

Injectors

Feed pump Solar Collectors

Recirculation Process

Better Flow Stability

Better Controllability

More complex

Higher investment costs

Higher parasitics

Feed pump

Separator

T

u

r

b

i

n

e

Recirculation pump

Solar Collectors


Contents




Introduction


Comparison between the DSG and the HTF (oil) technologies

Smaller environmental risks because oil is replaced by water

Higher steam temperature (maximum steam temperature with oil = 385ºC)

Advantages of the DSG technology:

The Direct Steam Generation Process


Scheme of a typical HTF plant with parabolic trough collectors

Thermal oils currently available have a thermal limits of 398ºC. There is a significant

degradation above 400ºC

Typical HTF Solar Thermal Power Plant

295 ºC Oil

395 ºC Oil

Steamgenerator

Deaerator

Reheater

Oil expansion vessel

Steam turbine

CondenserG

So

lar

Fie

ld

Preheater

Superheated Steam (104bar/380ºC)

Reheated steam 17bar/371ºC

G







The overall plant configuration is more simple


Simplified Scheme of typical HFT and DSG solar thermal power plants

Direct Steam Generation versus HTF Technology

Auxiliary boiler

Degasifier

Condenser

Steam turbine

GDV Plant

Steam at 104 bar/400 ºC

Liquid water at 114 bar / 120 ºC

Superheater

Steam Generator

Degasifier

Reheater

Oil expansion tank

Auxiliary heater

Solar Field

Steam turbine

Condenser

Oil at 295 ºC

Oil at 390 ºC

Steam at104 bar/371 ºC

Oil

Cir

cu

it

HTF Plant








Lower investment and O&M costs and higher plant efficiency


Lower LCOE of DSG versus HTF Plants

LEC changes by different DSG options

compared to oil reference

(TES = storage, OT = once-through,

PCM = PCM storage).

A comparative study of HTF and DSG performed by DLR for a 100 MWe plant

with a 9-hour TES has shown that:

• Scaling-up beyond a certain limit is not recommended for DSG plants (two 50 MWe plants together have a lower LEC than a single 100 MWe plant)

• The size and type of TES has a great impact on the LEC





Solar field control under solar radiation transients

Disadvantages of the DSG technology:






Influence of solar radiation transients on feed-water flow distribution


'1L

Radiación solar

2L 3L1L

To >Ti

Po <Pi

'3L'2L

m

Pi, Ti

T’ < To

P’ > Po

Radiación solar

m

Pi, Ti

Radiación solar

"1L "2L "3L

T > To

P” < Po

m

Pi, Ti






Instability of the two-phase flow inside the receiver tubes









The Ledinegg instability

Mass flow, m

Pre

ssu

re d

rop

,

P

Pressure drop versus mass flow in a row of PTC wit DSG at

Constant intel temperature, outlet pressure and heat

Only Steam

Only liquid

Typical performance curve

of a centrifugal pump

P

P’

•P”

•

•

0)

cteEdm

P






Instability of the two-phase flow inside the receiver tubes

Temperature gradients at the receiver pipes







Uneven heat transfer at the steel absorber pipe

Receiver pipe

Parabolic trough

concentrator

hliquid

hliquid



Temperature gradients in the steel absorber pipes

Uneven heat transfer at the steel absorber pipe



DSG-related projects and studies since 1980

Theoretical studies by SERI (1982)

The ATS (Advance Trough System) project by LUZ,(1987-1991)

DSG with Linear Solar Concentrators

Experiments by ZSW at the HIPRESS test facility (1992-1994)

The project PRODISS

The GUDE project experiments at Erlangen (1992-1995)

The project ARDISS (1994-1997)

R+D activities at UNAM (Mexico, 1976- up to date)

The DISS project (1996-2001)

The RealDISS project (2009-2011)

The INDITEP project (2002-2005)

The DUkE project (2012-2014)


Contents




Introduction


Curent Status


Technical feasibility of the DSG process in linear solar concentrators has

been proven. There are several DSG solar thermal power plants in operation



Plant TSE-1, Thailand

5 MWe

34 bar, 340 °C

Technology by Solarlite



Plant Puerto Errado-2, Spain

30 MWe

55 bar, 270 °C

Technology by Novatec&ABB


Accurate simulation&design tools for DSG solar fields have been developed

Ball-joints for water/steam at 100bar/500ºC have been successfully tested.

The best configuration for commercial DSG solar fields is a mixture of injection

and recirculation. This configuration has been experimentally evaluated at PSA




Curent Status



Scheme of a DSG row of collectors with Recirculation

( 20%)

( 7%)

Feed water

Water recirculation

Preheating + Evaporation

Water

inyection

Steam superheating

Water/steam

separator


Compact and cost-effective water/steam separators have been developed








Curent Status



Water/steam separators for DSG

Classic water/steam separator Compact water/steam separator


A cost-effective thermal energy storage technology for DSG still to be

developed








Compact and cost-effective water/steam separators have been developed

Technical feasibility of the Once-Through option must be fully investigated

Curent Status



Upgraded PSA DISS Facility for Once-Through mode

View of the new DISS solar field for Once-Through at 500ºC /112bar

International Workshop on:

DESIGN OF SUBSYSTEMS FOR CONCENTRATED SOLAR POWER TECHNOLOGIES19-22 December 2013. Jodhpur (India)

Eduardo Zarza MoyaLoreto Valenzuela Gutiérrez

CIEMAT-Plataforma Solar de Almería

E-mail: [email protected]

End of the Presentation

Thank you very much for your attention !!


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