VALIDATION OF SOL
A PHOTOVOLTAIC POTENTIAL MODEL WITH
EXTENSION TO BUILDING FACADES
S. Freitas1,2, D. Martins1, P. Redweik3,4,5, C. Catita 3,4, C. Rodrigues6, A. Joyce6, M. C. Brito3,5
1SESUL
– Centre for Sustainable Energy Systems, University of Lisbon
2MIT Portugal - Sustainable Energy Systems Program
3IDL - Instituto Dom Luiz, University of Lisbon
4Centre of Geology, University of Lisbon
5DEGGE – Department of Geographic Engineering, Geophysics and Energy, University of Lisboa
6LNEG – Laboratório Nacional de Engenharia e Geologia
Why solar potential models for the urban environment?
Regulating Energy Efficiency in Urban Contexts
The design of modern cities must be oriented towards the taking of the full potential of the solar resource
We need the sun…
Cities as great consumers of energy
Nearly Zero Energy Buildings (nZEB)
Fast technological improvement of solar energy
Decreasing costs of PV
Increasing public acceptance
However…
Limited available area
Insufficient solar radiation
Unfavourable meteorological conditions
Obstructions from the surroundings
2
SOL: the solar potential model
The algorithm:
Digital Surface Model
Typical Meteorological Year (SolTerm database)
Mathematical sun-path model
Sky View Factor
Shadow algorithm: horizontal vs vertical surfaces
Complete irradiation map
(1 hour time step, 1x1m2)
Redweik et al, Solar Energy 97 (2013) 332-241
Light Detection And Ranging (LiDAR)
3
SOL: the nouvel approach to vertical facades
What is interesting about facades?
• Vertical PV facades will produce
relatively more power in winter and
less in summer
• Different solar facades of a building
will produce at maximum power at
different times of the day
• Soiling rates will be much lower when
PV panels are vertically installed
• Less maintenance will be required
• Solar potential doubles!
Redweik et al, Solar Energy 97 (2013) 332-241
• In modern cities, the ratio between
roof area and facade area is high
4
SOL: Validation case study – LNEG Solar XXI building facade
IST
5
SOL: Validation case study - Methodology
1
2
Solar XXI data:
• Global vertical irradiation 𝐺𝑉𝐼𝑚𝑒𝑎𝑠
• Ambient temperature 𝑇𝑎𝑚𝑏,𝑚𝑒𝑎𝑠
𝑇𝑐𝑒𝑙𝑙,𝑐𝑎𝑙𝑐
𝑇𝑐𝑒𝑙𝑙,𝑚𝑒𝑎𝑠
𝑷𝒄𝒂𝒍𝒄
𝑃𝐴𝐶, 𝑚𝑒𝑎𝑠
SOL results:
• Irradiation 𝐺𝑚𝑜𝑑𝑒𝑙
• Ambient temperature 𝑇𝑎𝑚𝑏,𝑚𝑜𝑑𝑒𝑙
𝑷𝒎𝒐𝒅𝒆𝒍
𝑃𝐴𝐶, 𝑚𝑒𝑎𝑠
6
SOL: Validation case study – LNEG Solar XXI building facade
1. Measured Radiation to Photovoltaic production
𝑇𝑐𝑒𝑙𝑙,𝑐𝑎𝑙𝑐
𝑁𝑂𝐶𝑇 − 20º𝐶
= 𝑇𝑎𝑚𝑏,𝑚𝑒𝑎𝑠 +
𝐺𝑉𝐼
800 𝑊𝑚−2
𝑃𝑐𝑎𝑙𝑐 = 𝑃𝑟𝑒𝑓
𝐺𝑉𝐼
[1 + 𝛾 𝑇𝑐𝑒𝑙𝑙 − 𝑇𝑟𝑒𝑓 ]
𝐺𝑟𝑒𝑓
Marion, B., Prog. Photovol: Res. Appl.10, (2002) 264 205-214
Module parameters:
𝑁𝑂𝐶𝑇 = 47º𝐶
𝑃𝑟𝑒𝑓 = 160 𝑊
𝐺𝑟𝑒𝑓 = 1000 𝑊/𝑚−2
𝛾 = −0.5%/º𝐶
𝑇𝑟𝑒𝑓 = 25 ºC
7
SOL: Validation case study – LNEG Solar XXI building facade
1. Measured Radiation to Photovoltaic production
Novembro
June
November
June
150
50
100
450
150
300
100
150
50
50
23.1
23.2
23.3
23.4
23.5
23.6
Day
23.7
23.8
23.9
24
0
[W/m 2]
200
00
5
GVI
P
P
inv 2
inv 1
Pinv 2
50
Pinv 3
P
P
inv 3
inv 2
60
40
50
Pcalc
100
20
0
20
40
60
80
100
2
5.1
23.1
200
Pcalc
P
inv 3
40
300
100
5.2
23.2
5.3
23.3
5.4
23.4
0
10
20
20
Pcalc [W/m ]
5.5
23.5 5.6
23.6
Dias
Day
out
Pcalc
600
P
inv 3
80
measured
Tmeas ured [ºC]
inv 2
GVI [W/m2]
200
250
GVI
Pinv 1
Pinv 1
750
GVI [W/m2]
GVI [W/m2]
P
300
100
Pout [W/m 2]
P
250
300
100
PPout [W/m
[W/m22] ]
GVI
Pinv 1
300
0
60
330
900
330
5.7
23.7
5.8
23.8
50
60
5.9
23.9
624
00
Shadow events
10
0
30
40
Tcalc [ºC]
8
SOL: Validation case study – LNEG Solar XXI building facade
1. Measured Radiation to Photovoltaic production
November
60
100
50
50
80
Pmeasured [W/m 2]
Tmeasured [ºC]
Tmeasured [ºC]
June
60
40
30
20
Pinv 2
40
Pinv 3
60
30
40
20
20
10
10
0
Pinv 1
0
10
20
30
40
50
0
60
0
1020
20 40
30
60
40
80
50
100 60
2
Tcalc [ºC]
Tcalc
[ºC] ]
PNovember
[W/m
calc
June
100
100
Pinv 1
Pinv 1
80
Pmeasured [W/m 2]
Pmeasured [W/m 2]
80
Pinv 2
60
Pinv 3
40
Pinv 3
60
40
20
20
0
Pinv 2
0
0
20
40
60
2
Pcalc [W/m ]
80
100
0
20
40
60
80
100
2
Pcalc [W/m ]
9
SOL: Validation case study - Methodology
1
2
Solar XXI data:
• Global vertical irradiation 𝐺𝑉𝐼𝑚𝑒𝑎𝑠
• Ambient temperature 𝑇𝑎𝑚𝑏,𝑚𝑒𝑎𝑠
𝑇𝑐𝑒𝑙𝑙,𝑐𝑎𝑙𝑐
𝑇𝑐𝑒𝑙𝑙,𝑚𝑒𝑎𝑠
𝑷𝒄𝒂𝒍𝒄
𝑃𝐴𝐶, 𝑚𝑒𝑎𝑠
SOL results:
• Irradiation 𝐺𝑚𝑜𝑑𝑒𝑙
• Ambient temperature 𝑇𝑎𝑚𝑏,𝑚𝑜𝑑𝑒𝑙
𝑮𝑽𝑰𝒎𝒐𝒅𝒆𝒍
𝐺𝑉𝐼𝑚𝑒𝑎𝑠
10
SOL: Validation case study – LNEG Solar XXI building facade
2. Individual facade assessment VS Measured data
South
South
Digital Surface Model
Irradiance on vertical surfaces
(30th November 3pm)
11
SOL: Validation case study – LNEG Solar XXI building facade
2. Individual facade assessment VS Measured data
1
11 1
2
22 2
3
33 3
4
44 4
5
55 5
6
66 6
7
77 7
1
11 1
2
22 2
3
33 3
4
44 4
5
55 5
6
66 6
7
77 7
Global Radiation - June
Global
Radiation
- -June
Global
Radiation
June
Global
Radiation
June
Experimental:
62 kWh/m-22/month
22
Experimental:
62
kWh/m
Experimental:
62
kWh/m
/month
2 /month
Experimental:
62
kWh/m
/month
Simulation:
64 kWh/m
2/month
22
Simulation:
64
kWh/m
/month
Simulation:
64
/month
Simulation:
64
kWh/m
/month
Dif=
2kWh/m
%
Dif=
23
Dif=
2%
Dif=
2%%
5
55 5
10
101010
15
151515
20
202020
25
252525
Global Radiation - November
Global
Radiation
- -November
2
Global
Radiation
November
Global
Radiation
- November
Experimental:
79 kWh/m
2/month
22
Experimental:
79
kWh/m
2 /month
Experimental:
79
kWh/m
/month
Experimental:
79
kWh/m
/month
Simulation: 88 kWh/m2/month
2
2
Simulation:
88
kWh/m
Simulation:
88
kWh/m
/month
Simulation:
88
kWh/m
/month
Dif=
10
% /month
Dif=
10
%%%
Dif=
10
Dif=
10
5
55 5
10
101010
15
151515
100
100
100
100
80
808080
60
606060
40
404040
20
202020
0
0 00
100
100
100
100
80
808080
60
606060
40
404040
20
202020
20
202020
25
252525
0
0 00
12
Main conclusions and next steps…
• Photovoltaic production (𝑃𝑐𝑎𝑙𝑐 ) from measured irradiance (𝐺𝑉𝐼𝑚𝑒𝑎𝑠 ) is validated
• Overestimation of global vertical irradiance (𝐺𝑉𝐼𝑚𝑜𝑑𝑒𝑙 ), mainly in winter: diffuse irradiance algorithm needs revision
• Check the whole model SOL by comparing the measured photovoltaic production with 𝑃𝑚𝑜𝑑𝑒𝑙 obtained using 𝐺𝑉𝐼𝑚𝑜𝑑𝑒𝑙
• Different spatial resolutions and smoothening of shadows
Distribution of the strings on the facade
November 3p.m.
1
1
2
3
4
500
2
500
400
3
400
300
5
4
300
5
200
200
6
6
7
100
5
10
15
1x1m2 radiation grid
20
25
100
7
5
10
15
20
Interpolation and smoothening to a
0.2x0.2m2 radiation grid
25
13
Thank you!
In the future…