HEAT STORAGE
FOR CSP
Masdar Institute of Science and Tehcnology
Laboratory for Energy and Nano-Science (LENS)
Solar Energy Group
The Beam-Down Solar Thermal Concentrator
Experimental Characterization
and Modeling
Marwan Mokhtar
Concentrated Solar Power (CSP)
Page 2
Overview : Beam-Down Pilot Plant
Optical Design
Cavity Receiver
Ground Level Receiver
Segmented Secondary Reflector

Lower Wind Load

Lower Thermal Stress
Ganged-Type Heliostats
Three Banks of Mirrors
Courtesy of TokyoTech
Lower Blocking and Shading
Page 3
Overview : Beam-Down Pilot Plant
Optical Design
Cavity Receiver
Ground Level Receiver
Segmented Secondary Reflector

Lower Wind Load

Lower Thermal Stress
Ganged-Type Heliostats
Three Banks of Mirrors
Lower Blocking and Shading
Page 4
Overview : Beam-Down Pilot Plant
Optical Design
Cavity Receiver
Ground Level Receiver
Segmented Secondary Reflector

Lower Wind Load

Lower Thermal Stress
Ganged-Type Heliostat
Ganged-Type Heliostats
Three Banks of Mirrors
Lower Blocking and Shading
Conventional Heliostat
Page 5
Motivation
Initial Project Objectives
 Test design concepts
 Simulation model verification
 Feasibility of scaling up
LENS Experimental Testing
(March 2010)
 Inadequacies in the measurement
system
 Heliostat concentration quality
Page 6
Outline
Beam-Down
Experimental Characterization &
Modeling
Preliminary
Experimental
Characterization
Concentrated Solar
Flux Measurement
System
Geometrical-Optics
Model and Error
Analysis
Page 7
Beam Down
Performance
Overview
Outline
Beam-Down
Experimental Characterization &
Modeling
Preliminary
Experimental
Characterization
Concentrated Solar
Flux Measurement
System
Geometrical-Optics
Model and Error
Analysis
Page 8
Beam Down
Performance
Overview
Brief on the Measurement System
4
x 10
11
10
100
9
8
200
7
6
300
5
4
400
3
500
2
1
600
100
200
300
400
500
600
Image of Flux Distribution on the Target Taken by
the CCD Camera
Page 9
Brief on the Measurement System
Lambertian Target and Embedded Heat Flux Sensors
Page 10
Heliostat Field Performance Test
Optical performance characterization of
individual heliostats
Identify problems in the design or/and
implementation
6 days of testing
33 heliostats
5 data points per heliostat per day
900 < flux maps to inspect
100
200
300
400
500
600
700
800
900
100
Page 11
200
300
400
500
600
700
800
900
Metrics
Flux Map
Total Energy
Content
Flux
Distribution
Concentration
Centering
Page 12
Hypothetical Receiver and Weighted Flux Map
Centroid
and
distance r
Page 13
Receiver
dimensions
(r1,r2)
Flux Map Centroid Calculation
Calculation is affected by ambient radiation on the target
Page 14
Pre-processing: Flux Map Filtering
Page 15
Calculating the Weighted Flux Map
Centroid
and
distance r
Page 16
Receiver
dimensions
(r1,r2)
Selecting receiver aperture dimensions (r1,r2)
r1=70=28.5cm  60%
r2=120=49.0cm  90%
Cumulative power intercepted by the receiver from the centroid until the radial distance (r),
normalized by the total power.
Page 17
Results : Intercepted power
Page 18
Tower Shading
Page 19
Results : Flux Map Offset
Page 20
Flux Centering and Optical Alignment
Page 21
Tracking Sensor Alignment
Page 22
Central Reflector Alignment
Page 23
Main Observations
1) Inadequacies in the measurement system
2) Heliostat concentration quality
 = 50o,  = -47o, d = 0.5o, d = 0.5o
Canting:actual, SpillageIdeal= 7%, Spillagew / error= 14%
800
Actual Flux Map
Standard Time: 10:40,  = 50o,  = -47o
2500
2500
w/ errors d ,d
700
2000
600
1500
1500
500
1000
1000
400
500
500
300
0
200
-500
100
-1000
0
-1000
-1500
-2000
0
-0
-500
-1500
-100
-200
2000
X "mm"
X "mm"
Factory Calibration W/m 2
Ideal efffective source
-2000
-2500
100
200
300
400
500
600
700
800
-2500 -2000 -1500 -1000 -500
0
500 1000 1500 2000 2500
2
Y "mm"
Reference Reading
W/m
Page 24
-2500
-2500 -2000 -1500 -1000 -500
0
500
Y "mm"
1000 1500 2000 2500
Outline
Beam-Down
Experimental Characterization &
Modeling
Preliminary
Experimental
Characterization
Concentrated Solar
Flux Measurement
System
Measurement
System
Inadequacies
Concentration
Quality
Page 26
Geometrical-Optics
Model and Error
Analysis
Beam Down
Performance
Overview
Outline
Beam-Down
Experimental Characterization &
Modeling
Preliminary
Experimental
Characterization
Concentrated Solar
Flux Measurement
System
Measurement
System
Inadequacies
Concentration
Quality
Page 27
Geometrical-Optics
Model and Error
Analysis
Beam Down
Performance
Overview
Concentrated Solar Flux Measurement System
Optical Method
Convenient
High Resolution 700x700
Less Accurate
Requires a Uniform Lambertian
Target
Measures Luminance (cd/m2)
4
x 10
11
10
100
9
8
200
7
6
300
5
4
400
3
500
2
1
600
100
Page 28
200
300
400
500
600
Concentrated Solar Flux Measurement System
Heat Transfer Method
Flux Measured in (W/m2)
Accurate
Reliable
Low Resolution (Point Measurement)
Requires real-time corrections
against ambient conditions
Page 29
Concentrated Solar Flux Measurement System
4
x 10
11
The combination of the two
system will give:
10
100
9
8
200
High resolution of optical
method
Accuracy of the heat transfer
method
7
6
300
5
4
400
3
500
2
1
600
100
200
300
400
500
600
The final result is a heat
“Flux Map” in (W/m2)
Page 30
Problems in the Inherited System
Heat Transfer Method
Optical Method (Steve’s Thesis)
ON/OFF Cooling system
How Lambertian is the target ?
Response to varying ambient
conditions
Degraded Quality of the target
Manufacturer calibration for
different spectrum
CCD camera temperature response
and the correlation between the
two systems
(Steve’s Thesis)
Page 31
Heat Flux Sensors (HFS)
Courtesy of Kidd and Nelson 1995
Page 32
Preliminary Testing of HFS
800
700
Factory Calibration W/m 2
600
500
400
300
200
RMSE= 115 W/m2
100
0
-100
-200
0
100
200
300
400
500
Reference Reading W/m2
Page 33
600
700
800
Heat Transfer Model of HFS
G
Page 34
Temperature Variation in HFS
Page 35
Heat Transfer Model of HFS
G
We need measurement of
•Reference Solar Radiation
•Local Wind Speed
•Ambient Temperature
•Effective Sky Temperature
•Cooling Water In/outlet Temperature
Page 36
Experimental Setup for Calibration
Page 37
Results of Applying the Regression Model
Page 38
Results of Applying the Regression Model
800
700
Predicted Reading W/m 2
600
500
400
300
RMSE= 6.3 W/m2
200
100
0
-100
-100
0
100
200
300
400
500
Reference Reading W/m 2
Page 39
600
700
800
Residuals Analysis
40
Residuals [W/m 2]
Residuals [W/m 2]
40
20
0
-20
0
200
400
0
-20
-15
800
600
20
Reference Solar Radiation [W/m ]
Residuals [W/m 2]
Residuals [W/m 2]
10
40
40
20
0
-20
-10
5
0
-5
Tw - Tambient [K]
-10
2
-5
0
10
5
20
0
-20
0.5
2
1.5
1
4
-1
4
4
(Tw ) - (Tsky ) [K ]
W spd * (Tw - Tambient) [K.m.s ]
Page 40
2.5
9
x 10
In-Situ Calibration of HFS
Page 41
In-Situ Calibration of HFS
Page 42
Regression Model
forced to be the same for all sensors
Page 43
Results of Applying the Regression Model
1000
900
Predicted HFS Reading W/m 2
800
700
600
500
400
RMSE= 16.3 W/m2
300
200
100
0
0
100
200
300
400
500
600
Actual HFS Reading W/m
Page 44
700
2
800
900
1000
Residuals Analysis
60
40
20
Residuals [W/m 2]
60
40
20
0
-20
-40
-60
-100
-120
60
-20
70
80
90
100
110
120
130
140
Radiative Loss [W/m 2]
-40
60
40
-60
20
-80
Residuals [W/m 2]
Residuals [W/m 2]
-80
0
-100
-120
-200
0
200
600
400
800
1000
0
-20
-40
-60
-80
2
PSP [W/m ]
-100
-120
-80
-60
-40
-20
0
20
40
Convective Loss [W/m 2]
Page 45
60
80
100
120
Outline
Beam-Down
Experimental Characterization &
Modeling
Preliminary
Experimental
Characterization
Concentrated Solar
Flux Measurement
System
Measurement
System
Inadequacies
Concentration
Quality
Page 46
Geometrical-Optics
Model and Error
Analysis
Beam Down
Performance
Overview
Geometrical Optics Model
 Very fast calculation
compared to ray tracing
 Allows the study of:
1. Optical aberrations
2. Optical errors and real
sunshapes
3. Spillage, scattering,
canting and other
optical design
parameters
Page 47
Visualization of the Model
Page 48
1. Optical Aberrations
Page 49
1. Optical Aberrations
Actual Flux Map
Standard Time: 16:09,  = 30o,  = 69o
2500
2500
2000
2000
1500
1500
1000
1000
500
500
X "mm"
X "mm"
 = 30o,  = 69o, d = 0.5o, d = 0.5o
Canting:actual, SpillageIdeal= 10%, Spillagew / error= 17%
0
-500
-500
-1000
-1000
-1500
-1500
-2000
-2500
-2500 -2000 -1500 -1000
-0
-2000
-500
0
Y "mm"
500
1000
1500
2000
2500
Page 50
-2500
-2500 -2000 -1500 -1000
-500
0
500
Y "mm"
1000 1500
2000 2500
1. Optical Aberrations
 = 61o,  = 0o, d = 0.5o, d = 0.5o
Canting:actual, SpillageIdeal= 0%, Spillagew / error= 5%
Actual Flux Map
Standard Time: 12:30,  = 61o,  = 0o
2500
2500
Ideal efffective source
w/ errors d ,d
2000
1500
1500
1000
1000
500
500
X "mm"
X "mm"
2000
0
-500
-500
-1000
-1000
-1500
-1500
-2000
-2500
-2500 -2000 -1500 -1000
-0
-2000
-500
0
Y "mm"
500
1000
1500
2000
2500
Page 51
-2500
-2500 -2000 -1500 -1000
-500
0
500
Y "mm"
1000 1500
2000 2500
2. Spillage and Heliostat Defocusing
Page 52
2. Spillage and Heliostat Defocusing
Page 53
3. Error Analysis
Intercept Factor: Portion of radiation falling
on the target that is intercepted by the
receiver
Effective Source:
Effect of optical errors
combined with sunshape
Intercept Factor
assuming Perfect optics
and point sun
Page 54
Effective Source
1
Sunshape
Effective Errors
Effective Source
0.9
Total Optical Errors
3.74 mrad
CSR = 5%
Normalized radiation intensity
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-0.06
-0.04
Page 55
-0.02
0
Deviation [rad]
0.02
0.04
0.06
Deviation due to Effective Source Errors
Deviation due to effective source error
Canting= actual,  = 50o,  = -47o, CSR=5%,  eff-source=0.00374 rad
Facet#1
Facet#13
Facet#15
Facet#19
Facet#32
1
Probability
0.8
0.6
0.4
0.2
0
0
200
400
600
800
1000 1200 1400 1600 1800 2000 2200
Deviation [mm]
Page 56
Outline
Beam-Down
Experimental Characterization &
Modeling
Preliminary
Experimental
Characterization
Concentrated Solar
Flux Measurement
System
Measurement
System
Inadequacies
Concentration
Quality
Page 57
Geometrical-Optics
Model and Error
Analysis
Beam Down
Performance
Overview
Hypothetical Receiver and Power Block Design
4
x 10
10
100
9
8
200
7
6
300
5
4
400
3
500
2
1
600
100
200
300
400
500
600
Page 58
Optimal Receiver Size
4
10
x 10
Net Useful Power (Day Average), Tfm,o= 773[K]
Net Useful Power
Incident Power
Radiation Loss
Convection Loss
9
8
Power [W]
7
6
5
4
3
2
1
0
0
0.5
1
1.5
Radius [m]
2
2.5
Receiver Heat Loss Model
 Liquid Sodium is used as a HTF
(MP:371K,BP:1156K)
Heat Removal
Factor
Overall Heat Loss
Page 60
Receiver Heat Loss Model
 Heat Removal & Efficiency Factors
Page 61
Receiver Heat Loss Model
Convection Losses
Radiation Loss
Losses are function of Tpm
and m hence an iterative
process is required
Page 62
Optimal Receiver Size
4
10
x 10
Net Useful Power (Day Average), Tfm,o= 773[K]
Net Useful Power
Incident Power
Radiation Loss
Convection Loss
9
8
Power [W]
7
6
5
4
3
2
1
0
0
0.5
1
1.5
Radius [m]
2
2.5
Optical Efficiency
Optical Efficiency
Average Eff = 37%, 34%, 33%, 32%,
50
45
40
Efficiency [%]
35
30
25
Tfm,o= 400oC
20
Tfm,o= 500oC
Tfm,o= 600oC
15
Tfm,o= 700oC
10
5
0
6
8
10
12
Time
14
16
18
Receiver Collection Efficiency
Receiver Efficiency
Average Eff = 70%, 74%, 72%, 70%,
90
80
70
Efficiency [%]
60
50
Tfm,o= 400oC
40
Tfm,o= 500oC
30
Tfm,o= 600oC
20
Tfm,o= 700oC
10
0
6
8
10
12
Time
Page 65
14
16
18
Overall Thermal Efficiency
Overall Thermal Efficiency
Average Eff = 28%, 27%, 26%, 24%,
45
40
35
Efficiency [%]
30
25
20
Tfm,o= 400oC
15
Tfm,o= 500oC
Tfm,o= 600oC
10
Tfm,o= 700oC
5
0
6
8
10
12
Time
Page 66
14
16
18
Useful Thermal Power Collected
4
12
Useful Power
x 10
Power Collected in HTF [W]
10
8
6
Tfm,o= 400oC
Tfm,o= 500oC
4
Tfm,o= 600oC
Tfm,o= 700oC
2
0
6
8
10
12
Time
Page 67
14
16
18
Maximum Possible Work
4
7
Maximum Possible Work
x 10
6
Work [W]
5
4
Tfm,o= 400oC
3
Tfm,o= 500oC
Tfm,o= 600oC
2
Tfm,o= 700oC
1
0
6
8
10
12
Time
Page 68
14
16
18
Outline
Beam-Down
Experimental Characterization &
Modeling
Preliminary
Experimental
Characterization
Concentrated Solar
Flux Measurement
System
Measurement
System
Inadequacies
Concentration
Quality
Page 69
Geometrical-Optics
Model and Error
Analysis
Beam Down
Performance
Overview
Collaboration Team
Page 70
LENS Solar Group Members
Abdul Qadir
Ahmad Zayan
Irene Rubalcaba
Marwan M. Mokhtar
Matteo Chiesa
Peter Armstrong
Ragini Kalapatapu
Steven Andrew Meyers
Zaid M. Tahboub
&
The Committee
Dr. Matteo Chiesa
Dr. Peter Armstrong
Dr. Olaf Goebel
Page 71
HEAT STORAGE
FOR CSP
Thank You
ً ‫شكرا‬