Ppf a tool to study solar irradiation and illuminance in urban areas
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PPF: a tool to study solar irradiation and illuminance in urban areas. Raphaël Compagnon (September 2002) Developed in the framework of the European project : PRECis: Assessing the Potential for Renewable Energy in Cities.

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Ppf a tool to study solar irradiation and illuminance in urban areas

PPF: a tool to study solar irradiation and illuminance in urban areas

Raphaël Compagnon

(September 2002)

Developed in the framework of the European project:PRECis: Assessing the Potential for Renewable Energy in Cities


A method to quantify the potential for solar (passive+active ) and daylighting applications in urban areas

Focus mainly on vertical surfaces (buildings facades)

Goal: helping thedesign of “Solar Cities”


Final energy urban solar and daylight availability utilisation factors
[Final Energy] ) and daylighting applications in urban areas=[Urban Solar and Daylight Availability][Utilisation Factors]

[Urban Solar and Daylight Availability]=[Sky][Urban form]


Sky model
Sky model ) and daylighting applications in urban areas

Hourly sky models generated by gendaylit usingclimatic data from METEONORM

Averaging process to obtain «average sky models » for specific applications

Heating season

Year

8h–18h

radiance values

radiance values

luminance values

2

2

[W/m

/sr]

2

[W/m

/sr]

[lm/m

/sr]

Active solar applications

Passive solar

Daylighting


Average radiometric sky model computed over the heating ) and daylighting applications in urban areas

seaso

n (2299 hours):

Average radiometric sky model computed over the whole

year (4330 hours):

False colour radiance scale:

Radiometric average skiy models(solar applications)


Photometric average sky model daylighting
Photometric average sky model ) and daylighting applications in urban areas(Daylighting)

Average photometric sky model computed over the whole year (4330 hours):

False colour luminance scale:


3d buildings model
3D buildings model ) and daylighting applications in urban areas

Geometric data:

  • Buildings footprints at ground level

  • Top heights

    Numeric data:

  • Number of storeys


Simulations

Sky component ) and daylighting applications in urban areas

Reflected component(1st order &2nd order)

 Simulations 

Using Radiance backward ray-tracing program

Sky vault

“virtual” pyranometer or luxmeter


Ppf structure
PPF structure ) and daylighting applications in urban areas


Global solar irradiation distributions

Facades % with PV potential ) and daylighting applications in urban areas

=

Global solar irradiation distributions

Irradiation in [kWh/m2]

Threshold for PV facades systems


Global solar irradiation heating season

Facades % with passive solar potential ) and daylighting applications in urban areas

=

Global solar irradiation (heating season)

Irradiation in [kWh/m2]

Threshold for passive solar


Illuminance distributions

Facades % with daylighting potential ) and daylighting applications in urban areas

Threshold for daylighting

=

Illuminance distributions

Mean illuminance (8h-18h) [klx]


Case study site in fribourg ch
Case study site in Fribourg (CH) ) and daylighting applications in urban areas

  • Facades fractions:

  • for PV = 6.5 %

  • for passive solar = 52 %

  • for daylighting = 54 %

Perolles areaPlot ratio = 1.2


Hypothetical urban forms plot ratio 2 0
Hypothetical urban forms ) and daylighting applications in urban areas(plot ratio=2.0)

  • PV = 10 %

  • passive solar = 84 %

  • daylighting = 83 %

Comb (6 storeys)

  • PV = 15 %

  • passive solar = 80 %

  • daylighting = 82 %

Courtyards (4 & 8 storeys)

  • PV = 21 %

  • passive solar = 100 %

  • daylighting = 100 %

Towers (15 storeys)


Climatically independent characteristics

Outdoor daylight factors (CIE overcast sky) ) and daylighting applications in urban areas

Sky view factors (SVF)

Climatically independent characteristics


How to define the orientation of an urban area

Perolles area ) and daylighting applications in urban areasFribourg (CH)

Plaka areaAthens (GR)

How to define the “orientation” of an urban area ?

  • Count SVF-weighted facades areas facing every directions


Visualisations
Visualisations ) and daylighting applications in urban areas

Gray level aerial view showing annual irradiation levels on a part of the PATHSIA area in Athens


Visualisations1
Visualisations ) and daylighting applications in urban areas

Falsecolour aerial view showing roof areas suitable for PV modules on a part of the PATHSIA area in Athens


Conclusions
Conclusions ) and daylighting applications in urban areas

  • PPF allows to compute irradiation and illuminance distributions over large urban areas

  • Already used for several case studies

  • PPF used as a tool for ongoing projects in collaboration with EPFL

  • New extensions planned for urban open space analysis


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