Overview on Direct Steam Generation (DSG) and

Experience at the Plataforma Solar de Almería (PSA)

Parabolic Trough 2007 Workshop

Eduardo Zarza CIEMAT-Plataforma Solar de Almería, Apartado 22, Tabernas, E-04200 Almería, Spain Phone (+34) 950387931 Fax: (+34) 950365015 E-mail: eduardo.zarza@psa.es

March 8-9, 2007 (Denver)

Parabolic Trough 2007 Workshop

Overview on Direct Steam Generation &

PSA experience

) Advantages and disadvantages of the DSG process

) R+D activities related to DSG since 1980

) State-of-the-art of the DSG technology

March 8-9, 2007 (Denver)

The Direct Steam Generation Process

Comparison between the DSG technology and the HTF (oil) technology

Advantages of the DSG technology: & Smaller environmental risks because oil is replaced by water

& Higher steam temperature (maximum steam temperature with oil = 380ºC)

& The overall plant configuration is more simple

& Lower investment and O&M costs and higher plant efficiency

DSG-related potential problems:¾ Solar field control under solar radiation transients

¾ Instability of the two-phase flow inside the receiver tubes

¾ Temperature gradients at the receiver pipes

March 8-9, 2007 (Denver)

The Direct Steam Generation Process

DSG-related projects and studies since 1980

) Theoretical studies by SERI (1982)

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

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

) The GUDE project experiments at Erlangen (1992-1995)

) The project PRODISS

) The project ARDISS (1994-1997)

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

) The DISS project (1996-2001)

) The INDITEP project (2002-2005)

March 8-9, 2007 (Denver)

The Direct Steam Generation Process

State-of-the-art of the DSG technology

¾ Technical feasibility of the DSG process in horizontal PTs has been proven. More than 5500 hours of operation have been accumulated at the DISS test facility

¾ Accurate simulation&design tools for DSG solar fields have been developed

¾ Ball-joints for water/steam at 100bar/400ºC have been successfully tested. Testing of ball-joints for steam at 100bar/550ºC currently underway.

¾ The best configuration for commercial DSG solar fields is a mixture of injection and recirculation. This configuration has been experimentally evaluated at PSA

¾ It is easy to keep the temperature gradients in the receiver pipes within safe limits. Maximum stress obtained at PSA during operation has been 47% of the limit allowed

¾ Compact and cost-effective water/steam separators have been developed

¾ A Spanish Consortium is promoting a 3 MWe DSG power plants to be installed at PSA

¾ Several projects related to DSG are currently underway in Europe

¾ A suitable thermal energy storage technology for DSG still to be developed

March 8-9, 2007 (Denver)

End of Presentation

! Many thanks for your attention ¡

Overview on DSG

March 8-9, 2007 (Denver)

Direct Steam Generation

Typical Temperature profile in a HTF Solar thermal Power Plant

Steam generator

Re-heater Oil expansion tank

Auxiliary heater

Solar Field

Condenser

Oil at 390 ºC

Steam at 104 bar/371 ºC

Oil

circ

uit

Steam at 17 bar/371 ºC

G

Pre-heater

Evaporator

Sobrecalentador

Steam Turbine

Oil at 295 ºC

March 8-9, 2007 (Denver)

Direct Steam Generation

Simplified Scheme of typical HFT and DSG solar thermal power plants

Solar field

De-gasifier

DSG Plant Steam at 104 bar/400 ºC

Water at 114 bar / 200 ºC

.

Degasifier

Re-heater

Auxiliary heater

Condenser

Oil at 295 ºC

Oil at 390 ºC

Steam at 104 bar/371 ºC O

il ci

rcui

t

HTF Plant Auxiliary heater

Condenser

Steam turbine

Super-heater

Steam Generator

Oil expansion tank

Solar Field

Steam turbine

March 8-9, 2007 (Denver)

Direct Steam Generation

The Ledinegg instability P

ress

ure

drop

, ∆ P

Characteristic curve of a row of DSG Parabolic troughs (constant Tin, Pout and Ed)

P” • ∂(∆ P) )P < 0

• ∂ q Ed = cte m

P’100% steam • Characteristic curve of

a centrifugal pump

100% liquid

Mass feed flow

March 8-9, 2007 (Denver)

Direct Steam Generation

Different sections in the rows of a DSG solar field

Solar Radiation

2L 3L1L

T

P

•

mq Preheating Evaporation Sperheating

March 8-9, 2007 (Denver)

Direct Steam Generation

Uneven heat transfer at the steel absorber pipe

Parabolic trough concentrator

h

h

Receiver pipe

liquid

liquid

March 8-9, 2007 (Denver)

Direct Steam Generation

The DSG test facility implemented by LUZ for the ATS project

March 8-9, 2007 (Denver)

Direct Steam Generation

The HIPRESS test facility implemented by ZSW to study the DSG process

March 8-9, 2007 (Denver)

Direct Steam Generation

The DSG test facility implemented by SIEMENS for the GUDE project

March 8-9, 2007 (Denver)

Direct Steam Generation The DISS test facility implemented at the PSA

(south)

B.O.P. buildingRow of collectors

March 8-9, 2007 (Denver)

The DISS solar field

Aerial view of the DISS facility

Direct Steam Generation The DISS test facility implemented at the PSA

Water

0º to 8º

Recirculation pump

0º0º

l ll

1 2 3 4 5 6 7 8 9 10 11

Water/steam separator

Control valves

of evaporation

Water injection circuit

Feedwater

Feedwater pump

0º 0º

B A

TK-4

March 8-9, 2007 (Denver)

(40-108 bar) (30 - 100 bar)

Superheated steam

0º-2º-4º 0º-2º-4º 0º-2º-4º 0º-2º-4º 0º-2º-4º 0º-2º-4º 0º-2º-4º 0º-2º-4º

Power Block

Specia test co ector

Water pre-heating and beginning

valve

100 m 100 m

Water evaporation (Cont.) Steam superheating

Direct Steam Generation

Scheme proposed for commercial DSG solar fields

Feedwater

Water injectorV1

V2

Water recirculation

Water preheating (3 collectors) + boiling ( 5 collectors)

March 8-9, 2007 (Denver)

March 8-9, 2007 (Denver)

Steam Production at 100bar/350ºC (05/07/2001)

10:00 12:00 14:00 16:00 18:00 20:000

100

200

300

400

500

600

700

800

900

1000

Beam solar radiation

Inlet temperature

Outlet temperature

Sol

ar R

adia

tion

(W/m

2 )

Inle

t and

Out

let T

empe

ratu

res

(ºC

)

Local time (hh:mm)

0

10

20

30

40

50

60

70

80

90

100

110

Outlet steam pressure (bar)

Steam flow *100 (kg/s)

Ste

am p

ress

ure

(bar

)

Ste

am fl

ow *

100

(kg/

s)

Direct Steam Generation

Experimental data collected at the DISS facility

Direct Steam Generation

Water/steam separators for DSG

Classic water/steam separator Compact water/steam separator

March 8-9, 2007 (Denver)

Direct Steam Generation

Simplified Scheme of the DSG Solar Field to be installed at PSA 505 m

Power Bolck

•

125

m

17.5 m

17.5 m

• •

•

•

• lat

•

•

•

Recircu ion pump

Feed pump

Technical parameters

• Number of parallel rows: 4 • Number of collectors per row: 10 ET-100 collectors • Lenght of every collector: 98,5 m • Parabola width: 5.76 m • Total aperture area: 21934 m2 • Peak Thermal power (Ed=1kW/m2): 14,3 MW

March 8-9, 2007 (Denver)

Direct Steam Generation

Simplified Scheme of the Power block for the PSA DSG plant

GSolar field

Generator

HP LP

Aero-condenser

Hot air

Steam turbine

P = 65 bar T = 400ºC

P = 5,6 bar T = 172 ºC

P = 0,1 bar T = 46 ºC

P = 85 bar T = 126 ºC

Degasifier + Storage water tank

P = 2,44 bar T = 127 ºC

P = 80 bar T = 115 ºC

P = 70 bar T = 411ºC

March 8-9, 2007 (Denver)

Direct Steam Generation

Temperature gradients in the steel absorber pipes

March 8-9, 2007 (Denver)