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 Program3IDL - Instituto Dom Luiz, University of Lisbon 4Centre of Geology, University of Lisbon 5DEGGE – Department of Geographic Engineering, Geophysics and Energy, University of Lisboa6LNEG – Laboratório Nacional de Engenharia e Geologia

VALIDATION OF SOL

Why solar potential models for the urban environment?

We need the sun…

Cities as great consumers of energyNearly Zero Energy Buildings (nZEB)Fast technological improvement of solar energyDecreasing costs of PVIncreasing public acceptance

However…

Limited available areaInsufficient solar radiationUnfavourable meteorological conditionsObstructions from the surroundings

Regulating Energy Efficiency in Urban ContextsThe design of modern cities must be oriented towards the taking of the full potential of the solar resource

2

SOL: the solar potential model

Light Detection And Ranging (LiDAR)

Digital Surface Model

Typical Meteorological Year (SolTerm database)

Mathematical sun-path model

Sky View FactorShadow algorithm: horizontal vs vertical surfaces

Complete irradiation map(1 hour time step, 1x1m2)

3

Redw

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The algorithm:

SOL: the nouvel approach to vertical facades

• In modern cities, the ratio between roof area and facade area is high

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4

• 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!

What is interesting about facades?

SOL: Validation case study – LNEG Solar XXI building facade

5

IST

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SOL: Validation case study - Methodology

SOL results:• Irradiation • Ambient temperature

Solar XXI data:• Global vertical irradiation• Ambient temperature

𝑷 𝒄𝒂𝒍𝒄𝑇 𝑐𝑒𝑙𝑙 , 𝑐𝑎𝑙𝑐

𝑇 𝑐𝑒𝑙𝑙 ,𝑚𝑒𝑎𝑠

𝑷𝒎𝒐𝒅𝒆𝒍

1 2

1. Measured Radiation to Photovoltaic production

𝑇 𝑐𝑒𝑙𝑙 , 𝑐𝑎𝑙𝑐=𝑇𝑎𝑚𝑏 ,𝑚𝑒𝑎𝑠+𝑁𝑂𝐶𝑇 −20 º𝐶  800𝑊𝑚−2 𝐺𝑉𝐼

𝑃𝑐𝑎𝑙𝑐=𝑃𝑟𝑒𝑓𝐺𝑉𝐼𝐺𝑟𝑒𝑓

[1+𝛾 (𝑇 𝑐𝑒𝑙𝑙−𝑇 𝑟𝑒𝑓 )]

𝑃𝑟𝑒𝑓=160𝑊𝐺𝑟𝑒𝑓 =1000𝑊 /𝑚−2

𝛾=−0.5% /º𝐶𝑇 𝑟𝑒𝑓=25 º C

SOL: Validation case study – LNEG Solar XXI building facade

7

Marion, B., Prog. Photovol: Res. Appl.10, (2002) 264 205-214

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1. Measured Radiation to Photovoltaic production

SOL: Validation case study – LNEG Solar XXI building facade

Shadow events

23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 240

50

100

150

200

250

300

330

GV

I [W

/m2 ]

June

Day

23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 240

50

100

Pou

t [W/m

2 ]

GVIPinv 1

Pinv 2

Pinv 3

Pcalc

0 10 20 30 40 50 600

10

20

30

40

50

60

Tmeasured

[ºC]

Tcalc [ºC]

0 20 40 60 80 1000

20

40

60

80

100

Pcalc [W/m2]

Pm

easu

red

[W/m

2 ]

November

Pinv 1

Pinv 2

Pinv 3

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 60

150

300

450

600

750

900

GV

I [W

/m2 ]

Dias

Novembro

5 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 60

100

200

300

Pou

t [W/m

2 ]

GVIPinv 1

Pinv 2

Pinv 3

Pcalc

23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 240

50

100

150

200

250

300

330

GV

I [W

/m2 ]

June

Day

23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 240

50

100

Pou

t [W/m

2 ]

GVIPinv 1

Pinv 2

Pinv 3

Pcalc

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1. Measured Radiation to Photovoltaic production

SOL: Validation case study – LNEG Solar XXI building facade

0 20 40 60 80 1000

20

40

60

80

100

Pcalc [W/m2]P m

easu

red [W

/m2 ]

November

Pinv 1

Pinv 2

Pinv 3

0 10 20 30 40 50 600

10

20

30

40

50

60

T mea

sure

d [ºC

]

Tcalc [ºC]0 20 40 60 80 100

0

20

40

60

80

100

Pcalc [W/m2]

P mea

sure

d [W/m

2 ]

November

Pinv 1

Pinv 2

Pinv 3

0 10 20 30 40 50 600

10

20

30

40

50

60

T mea

sure

d [ºC

]

Tcalc [ºC]

June

0 20 40 60 80 1000

20

40

60

80

100

Pcalc [W/m2]

P mea

sure

d [W/m

2 ]

June

Pinv 1

Pinv 2

Pinv 3

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SOL: Validation case study - Methodology

SOL results:• Irradiation • Ambient temperature

Solar XXI data:• Global vertical irradiation • Ambient temperature

𝑷 𝒄𝒂𝒍𝒄𝑇 𝑐𝑒𝑙𝑙 , 𝑐𝑎𝑙𝑐

𝑇 𝑐𝑒𝑙𝑙 ,𝑚𝑒𝑎𝑠

𝑮𝑽𝑰𝒎𝒐𝒅𝒆𝒍❑

1 2

SOL: Validation case study – LNEG Solar XXI building facade

Irradiance on vertical surfaces(30th November 3pm)

South

Digital Surface Model

South

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2. Individual facade assessment VS Measured data

2. Individual facade assessment VS Measured data

SOL: Validation case study – LNEG Solar XXI building facade

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Global Radiation - JuneExperimental: 62 kWh/m2/month

Simulation: 64 kWh/m2/monthDif= 2 %

5 10 15 20 25

1

2

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4

5

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40

60

80

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Global Radiation - NovemberExperimental: 79 kWh/m2/month

Simulation: 88 kWh/m2/monthDif= 10 %

5 10 15 20 25

1

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Global Radiation - JuneExperimental: 62 kWh/m2/month

Simulation: 64 kWh/m2/monthDif= 2 %

5 10 15 20 25

1

2

3

4

5

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70

20

40

60

80

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Global Radiation - NovemberExperimental: 79 kWh/m2/month

Simulation: 88 kWh/m2/monthDif= 10 %

5 10 15 20 25

1

2

3

4

5

6

70

20

40

60

80

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Global Radiation - JuneExperimental: 62 kWh/m2/month

Simulation: 64 kWh/m2/monthDif= 2 %

5 10 15 20 25

1

2

3

4

5

6

70

20

40

60

80

100

Global Radiation - NovemberExperimental: 79 kWh/m2/month

Simulation: 88 kWh/m2/monthDif= 10 %

5 10 15 20 25

1

2

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4

5

6

70

20

40

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3 %

Global Radiation - JuneExperimental: 62 kWh/m2/month

Simulation: 64 kWh/m2/monthDif= 2 %

5 10 15 20 25

1

2

3

4

5

6

70

20

40

60

80

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Global Radiation - NovemberExperimental: 79 kWh/m2/month

Simulation: 88 kWh/m2/monthDif= 10 %

5 10 15 20 25

1

2

3

4

5

6

70

20

40

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80

100

Main conclusions and next steps…

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• Photovoltaic production from measured irradiance is validated

1x1m2 radiation grid Interpolation and smoothening to a 0.2x0.2m2 radiation grid

November 3p.m.

5 10 15 20 25

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500

5 10 15 20 25

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Distribution of the strings on the facade

• Overestimation of global vertical irradiance (, mainly in winter: diffuse irradiance algorithm needs revision• Check the whole model SOL by comparing the measured photovoltaic production with obtained u• Different spatial resolutions and smoothening of shadows

In the future…

Thank you!