lecture 9: design criteria for new parabolic trough collectors
TRANSCRIPT
Lecturer: Eduardo Zarza MoyaPlataforma Solar de Almería – CIEMAT(e-mail: [email protected])
First Summer SchoolPart A: Line-focus Solar Thermal Technologies
September 20-24, 2021
Lecture 9:Design criteria for new Parabolic Trough Collectors
Slide 22 / 22“Design criteria for new parabolic trough collectors”
Design Criteria for new Parabolic Trough Collectors
Content
Software tools for the design of parabolic trough collectors
Basic guidelines for new designs of parabolic trough collectors
Slide 33 / 22“Design criteria for new parabolic trough collectors”
Design Criteria for new Parabolic Trough Collectors
Content
Software tools for new designs of parabolic trough collectors
Basic guidelines for new designs of parabolic trough collectors
Slide 44 / 22“Design criteria for new parabolic trough collectors”
Design of New Parabolic Trough Collectors
The design of new parabolic trough collectors:
must take into consideration the intended commercial applications
needs the experimental evaluation of prototypes
is commercially interesting nowadays
is a multidisciplinary task and previous experience is very valuable
Slide 55 / 22“Design criteria for new parabolic trough collectors”
aaa
cgeo d
wld
lwAAC
⋅=
⋅⋅⋅
==ππ
AC= net collector aperture area (m2)
Aa= absorber area (m2)
w= aperture width (m)
l= total length (m)
do= absorber diameter (m)
Geometrical Concentration Ratio
Design of New Parabolic Trough Collectors
Slide 66 / 22“Design criteria for new parabolic trough collectors”
Absorber Tube outer diameter, , do= 2·R
W/2
rβ/2
β
ψ
C geo, max = Sin(90) · Cos(0,266) / π·Sin(0,266) ≅ 70
)2/cos()2/(
ββsen
rR=
)2/(·)2/)·cos((
βπβ
sensen Ψ
=
Theoretical Maximum Geometrical Concentration Ratio
ldllc
o
ageometrica ⋅⋅
⋅=π o
a
Rl
·2⋅π= Cgeo
W W
)(·2
Ψ= senr
la
Rsenr
·)(·
πΨ
=
W
Design of New Parabolic Trough Collectors
Slide 77 / 22“Design criteria for new parabolic trough collectors”
Acceptance angle, β, and Aperture angle, ψ
da
βw/2
Ω
R’
Design of New Parabolic Trough Collectors
Slide 88 / 22“Design criteria for new parabolic trough collectors”
Acceptance Angle, β,
βmin= 0,53º
0,53º
Actual shape
Theoretical shape
Recommendation: 0,9º ≤ β≤ 1,5º
Design of New Parabolic Trough Collectors
Slide 99 / 22“Design criteria for new parabolic trough collectors”
Aperture Angle, ψ
ψ
Receiver tube
Parabolic reflector
-500 -400 -300 -200 -100 0 100 200 300 400 5000
50
100
150
200
250
300
350
400
Ψ=90º
Ψ=80º
Ψ=70º
Ψ=100ºC
D
B
A
Y
X
-500 -400 -300 -200 -100 0 100 200 300 400 500
0
50
100
150
200
250
300
350
400
Ángulo de abertura (ψ)
Área de captación m2
Área de espejos m2
Area de captación /Area de espejos
100 68,5 75,97 0,90 90 81,4 93,46 0,87 80 97,0 116,62 0,83 70 116,2 148,34 0,78
ApertureAngle, ψ
Aperture Aream2
Mirrors Aream2
Aperture Area/ Mirrors Area
Design of New Parabolic Trough Collectors
Slide 1010 / 22“Design criteria for new parabolic trough collectors”
Other recommendations for the collector design (I)
the size of the collector:• Big: for solar thermal electric plants• Medium: for industrial process heat applications• Small: for air conditioning systems or similar ones (small solar fields)
Structural design :• Maximum mechanical torsion at collector end ≤ 0,3º
Receiver tube type:• For T > 300ºC: evacuated tube with good selective coating• For T < 250ºC: non-evacuated tube, with carbon steel and black
chrome, nickel or thermal paint with high absorptivity• For 250ºC ≤ T ≤ 300º: the type of receiver tube depends on the
expected efficiency
Design of New Parabolic Trough Collectors
Slide 1111 / 22“Design criteria for new parabolic trough collectors”
Accuracy of the solar tracking system: ≈0,1º
Type of solar tracking control:• Either option (open-loop or close-loop control) have good performance
Type of Drive Unit:• For small-size collectors: electric motor with reduction gear box• For big-size collectors: hydraulic units
Other recommendations for the collector design (II)
Design of New Parabolic Trough Collectors
Slide 1212 / 22“Design criteria for new parabolic trough collectors”
Design Criteria for new Parabolic Trough Collectors
Content
Software tools for new designs of parabolic trough collectors
Basic guidelines for new designs of parabolic trough collectors
Slide 1313 / 22“Design criteria for new parabolic trough collectors”
Software tools for the design of parabolic trough collectors
Design tools for supporting structures, based on FEM (ANSYS)
Design of New Parabolic Trough Collectors
Slide 1414 / 22“Design criteria for new parabolic trough collectors”
Space frame performance analysis with ANSYS
Structure without deformation Structure deformation by torque
Design of New Parabolic Trough Collectors
Slide 1515 / 22“Design criteria for new parabolic trough collectors”
“Ray tracing” computer programs
Software tools for the design of parabolic trough collectors
Design tools for supporting structures, based on FEM (ANSYS)
Design of New Parabolic Trough Collectors
Slide 1616 / 22“Design criteria for new parabolic trough collectors”
“Ray Tracing”: angular distribution of both the incident and the reflected radiation
ncident radiation Reflected image
Vector normal to thereflecting surface
Angle of the reflexioncone
Design of New Parabolic Trough Collectors
Slide 1717 / 22“Design criteria for new parabolic trough collectors”
Tools for thermal simulation of receiver tubes
“Ray tracing” computer programs
Software tools for the design of parabolic trough collectors
Design tools for supporting structures, based on FEM (ANSYS)
Design of New Parabolic Trough Collectors
Slide 1818 / 22“Design criteria for new parabolic trough collectors”
0
1
2
3
4
5
6
7
8
9
10
350 400 450 500 550 600 650
Tabs / [K]
UL
/ (W
/m²·K
)
Aire (65 mbar)
Kr (65 mbar)
Aire (1 bar)
Aire (1x10-4 mbar)
0
1
2
3
4
5
6
7
8
9
10
350 400 450 500 550 600 650
Tabs / [K]
UL
/ (W
/m²·K
)
Aire (65 mbar)
Kr (65 mbar)Kr (65 mbar)
Aire (1 bar)
Aire (1x10-4 mbar)Aire (1x10-4 mbar)
Simulation of the thermal loss global coefficient in a receiver tube with different gasesin the annulus between the steel absorber and the glass cover (Rojas, 1993).
Design of New Parabolic Trough Collectors
Slide 1919 / 22“Design criteria for new parabolic trough collectors”
Tools for geometric analysis of concentrators
Tools for thermal simulation of receiver tubes
“Ray tracing” computer programs
Software tools for the design of parabolic trough collectors
Design tools for supporting structures, based on FEM (ANSYS)
Design of New Parabolic Trough Collectors
Slide 2020 / 22“Design criteria for new parabolic trough collectors”
Evaluation of the geometric shape accuracy using “Photogrammetry”
Parabolic trough concentrator with“Targets” attached for Photogrammetry
Deviations between the ideal shape and theactual shape of a parabolic trough surface
Design of New Parabolic Trough Collectors
Slide 2121 / 22“Design criteria for new parabolic trough collectors”
Final Recommendation
!! Use standard commercial components whenever possible
(e.g., steel profiles, mirrors and steel tubes of standard sizes).
The manufacture cost of the collectors will be much higher
otherwise¡¡
Design of New Parabolic Trough Collectors
Lecturer: Eduardo Zarza MoyaPlataforma Solar de Almería – CIEMAT(e-mail: [email protected])
First Summer SchoolPart A: Line-focus Solar Thermal Technologies
September 20-24, 2021
Lecture 9:Design criteria for new Parabolic Trough Collectors
- Thank you very much for your attention- Questions?