model tools for solar tower receiver systems summer … · model tools for solar tower receiver...

Model Tools for Solar Tower Receiver Systems

Prof. Dr. Bernhard Hoffschmidt

June 25-27, 2014

Font Romeu, France

CRS Receiver Simulation: Overview

Levels of Simulation

• System level

• layout

• simplified receiver models (also costs)

(receiver characteristic => as map or correlation)

• => Annual Performance

• Pre-design

• definition of basic receiver design

• Detailed design

• detailed analysis of

- solar flux distribution

- temperature distribution

- Stresses / lifetime assessment

• => Design Values

System Simulation: Workflow for Solar Towers Annual Yield Calculation

Load Curve for Ambient Temperature - Taweelah

0

5

10

15

20

25

30

35

40

45

50

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

hours [h]

tem

pera

ture

[°C

]

Climate data

Power plant process

Solar resource data

Solar field performance Operational strategy

1 2 3 4 5

Solar-Hybrid

1 2 3 4 5

Teillast

Solar

HFLCAL

Field Layout

Jahres -

Power plant -

simulation

h gross h net

P el

Q Rec usw .

p amb T amb

h Field

h Rec

Q Rec

A Field

etc.

p amb

T amb

j amb

DNI

Interface for

annual yields solar tower

receiver

hot

tank

G

steam generator

condenser

solar field

steam turbine

cold

tank

m PB

m R

m B r

R Br

T 1

T 2

PB

m PB

m R

Br PB R

T 1

m S

T 2

m PB

m R

R Br

T 1

PB

T 2

m PB

R Br

T 2

PB

T 1

R : Receiver Br :: Aux. . burner PB : Power block T 1 : hot tank T 2 : cold tank

1 2 3 4 5

m PB

Electricity demand

System Simulation: CSP System Modelling

- Heliostatfield

- Tower with receiver

- HTF loop

- Thermal storage

- Power block

- Total power of CSP power plant

- Most often systems are economically optimized (LCOE minimum)

PBTESHTFSFSFelsys ADNIP hhhhh Rec,

]/[costannualtotal

0,

kWhEURdtP

LCOEendt

telsys

Every single sub-

component is important!

solar tower

receiver

hot

tank

G

steam generator

condenser

solar field

steam turbine

cold

tank

System Simulation: Thermodynamic analysis of receiver

solar tower

receiver

solar field

),( SSFieldreflreflinc h ADNIQ

incQ recQ

lossincrec

inoutrec

QQQ

hhmQ

radloss,convloss,optloss,loss QQQQ

radloss,Qconvloss,Q

incident power on receiver aperture area:

power from receiver to HTF:

losses of receiver :

sunQ

][elevation sun :

][azimuth sun :

[-] efficiency optical fieldsolar :

[m2] area aperture fieldheliostat :A

[-]ty reflectivi average :

S

S

field

refl

refl

h

[kJ/kg] enthalpieoutlet inlet/ :h / h

[kg/s] HTF flow mass :

inout

m

optloss,Q

[W] lossesradiation :

[W] losses convective :

[W] losses optical :

radloss,

convloss,

optloss,

Q

Q

Q

Note: optical losses do not depend on the receiver

temperature whereas convective and radiation heat losses do

receiver efficiency:

increc / QQrech [W]receiver on power incident :

[W]receiver frompower thermal:

inc

rec

Q

Q

solar tower

receiver

solar field

incQ recQ

radloss,Qconvloss,Q

optical losses:

convective losses:

radiation losses:

sunQ

[-]receiver efficiency optical : opth

][m area aperturereceiver :

][W/m lossheat specific areaconstant :

2

rec

2

loss

A

q

optloss,Q

]K[W/mconstant Boltzmann Stefan :[-] emissivity : 42

optincopt loss, 1 hQQ

a) option “constant heat losses” :

reclossconv loss, AqQ

b) option “heat transfer coefficient ” :

recconv loss, ambrec ATTQ

desinc,

incdeswall,in-outin rec

Q

QTTTkTT

C][ mperatureambient te :

C][ emperaturereceiver tmean :

K][W/mt coefficienfer heat transconstant :

rec

rec

2

T

T

rec

4

amb

4

recrad loss, 15.27315.273 AKTKTQ

[W]power incident design :

[K] surfaceouter allreceiver w of etemperatur-Over :

)outlet inlet/ between re temperatutiverepresentaany define to(used

[-] 0.5 e.g. factor, g weightin:k

K][W/mt coefficienfer heat transconstant :

deswall,

2

desinc,Q

T


On system level different approaches

for receiver modeling can be used:

• simplified receiver models

(as shown before)

• receiver characteristic,

as map or correlation

(if available => detail

simulation)

typical receiver characteristic


Design

point

140mm

140mm

2mm

0.02 m²

Absorber

0.57 m²

Submodul

5.7 m²

Subreceiver

22.7m²

Receiver (Jülich)

Detail Design: Open Volumetric Receiver


Simulation of Volumetric Absorber Structures

homogenous approach channel model FEM

directions discretefor

tscoefficien scattering and absorption :radiation

ReNu;Nu

:ferheat trans

;0)(

;)()1(2

2

m

vv

v

fwv

f

p

fwvw

Ad

AA

TTAdz

dTvc

dz

dITTA

dz

TdPo

approach valid for different

kinds of porous structures

suitable for comparison

of different materials

gray tracin d terminate:radiation

nscorrelatio -Nu standard :ferheat trans

200 400 600 800 10000,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0A

bso

rber

wir

kungsg

rad [

-]

Flussdichte [kW/m²]

ARR = 0,50

exchanceradiation - FE :radiation

Equ. Stokes-Navier : transfermom. &heat

calculate performance of

defined honeycomb

structures

study temperature and flow

details inside regular porous

structures

Layout & Operation of Modular Air Receivers

parallel flow trough absorber modules adapt flow to flux distribution

140mm

140mm

2mm


140mm

140mm

2mm

parallel flow trough absorber modules adapt flow to flux distribution

step 1:

layout of fixed orifice

diameter for design flux

distribution

step 2:

variation of flow through

subreceivers during

operation to adapt to

changing flux profile



example: layout of mass flow distribution for Solar Tower Jülich

ray tracing: calculate flux distribution

for different sun angles

create artificial design flux

distribution for receiver layout

(weighted superposition of real

flux distributions)

calculate fixed orifice

size distribution

15 15 15 18 20 17 19 21 23 23 24 25 25 26 26 26 26 25 25 24 23 23 21 19 17 20 18 15 15 15

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20 17 20 23 26 28 29 31 32 33 34 35 35 35 36 36 35 35 35 34 33 32 31 29 28 26 23 20 17 20

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18 19 20 23 25 27 29 30 31 32 33 34 35 35 35 35 35 35 34 33 32 31 30 29 27 25 23 20 19 18

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15 15 15 15 18 20 17 19 20 21 23 23 24 24 24 24 24 24 23 23 21 20 19 17 20 18 15 15 15 15



example: layout of mass flow distribution for Solar Tower Jülich

calculation of maximum

material temperatures for

real flux distributions

Setup of a characteristic

map for the system

simulation



Conclusion

- System Simulation

- aims for determination of the design point with the highest annual

yield and the lowest LCOE (operation strategies)

- must be fast to enable an optimization of a set of different plant

configurations on a yearly base (storage sizes, power block designs,

hybrid modes…)

- models the components as simple as possible/acceptable due to the

demanded accuracy (correlations, characteristic maps,…)

- Detail Simulation

- aims the real design values for each component

- and the detection of constrains, critical operation modes and life

time estimation

- checks possible improvements and new design approaches

14 R. Buck > DLR Stuttgart > Stellenbosch University, April 10, 2014

15

Thank you for your attention!

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