Modeling solar radiation

for a bioclimatic urban planning

Raphaël Nahon, Benoit Beckers, Olivier Blanpain – July 10th 2015

2 Planning

1. A first methodology for the study of Bioclimatism in Urban planning a) The SERVEAU project b) Definition of the “bioclimatism” of an urban project c) The main stages of an urban project d) Presentation of the solar model e) Presentation of the thermal model f) Illustration on the Batignolles ZAC (joint development zone)

2. Towards a finest characterization of the daylight conditions

a) Different aspects of the solar radiation b) The UDI and DA, prime indicators of the daylight conditions in an interior c) Adaptation of the solar model d) Illustration on a simple office model

3. Conclusions and perspectives

3 Bioclimatism in urban planning – the SERVEAU project

SERVEAU Simulation, Evaluation and Reduction of the Energetic

Vulnerability of Urban Projects

11th Unified Inter-Ministry Fund call for projects

4 Bioclimatic urban planning characterization

Bioclimatism of an urban project

Daylight autonomy [% daylight hours]

Heating and cooling loads [kWh/m²]

Summer comfort

Beyond the scope of this study

5 Main stages of an urban project – The Guide plan

Guide plan : Approximate 2D distribution of the different elements of the urban program (LOD0*)

*OGC City Geography Markup Language (CityGML) Encoding Standard - Copyright © 2012 Open Geospatial Consortium

At this stage : Focus on the layout of the

transport networks , No consideration of the solar

aspect.

Figure – Guide plan of the Libera ZAC (source: Michel Guerin, architecte-urbaniste, 2006)

6 Main stages of an urban project – The Mass plan

Mass plan : Representation of the volumes as mass blocks (LOD1)

Figure – Mass plan illustration

At this stage : No required modelisation, Consideration of the solar

aspects through excel sheets with a low consideration of the geometry.

→ A key stage regarding the bioclimatic potential of an urban project

7 Main stages of an urban project – The Block plan

Block plan : Introduction of architectural details such as windows shapes and positions, solar protections, interior design,… (LOD4)

Figure – Block plan of the urban project of the Quartier du Mesnil (source: Atelier Jam, Latitude Nord, Mission Morel Jeol)

At this stage : Intervention of architects

and engineers, Thermodynamic

simulations, …

8 Bioclimatic urban planning characterization

Bioclimatism of an urban project

Daylight autonomy [% daylight hours]

Heating and cooling loads [kWh/m²]

! At the mass plan : • No description of the walls composition, • No indication on the glazing ratio and performance, • No indication on the possible solar protections, • No description of the interiors, • No indication on the windows shapes and positions, • … Necessity to build those parameters

9 The use of typologies

What is known : • Use of the building (housing, office, store, …), • Location, • Target performances (Standard, Effinergie, Passive).

• Walls composition, • Window-to-floor ratio, • Distribution of the glazing on the façades, • Glazing thermal performances, • Solar protections type, • Mean solar factor.

10 Bioclimatic urban planning

Bioclimatism of an urban project

Daylight autonomy [% daylight hours]

?

Heating and cooling loads [kWh/m²]

Solar gains through windows [kWh]

Irradiances on the façade [kWh/m²] Mean solar

factor

Glazing ratio

Glazing performance

Walls composition

Thermal model

11 Daylight autonomy, a simplified methodology

OR A B C

S 31 27 70

SO 31 21 64,2

O 32 14 58,4

NO 37 1 52,8

N 42 -11 47,2

NE 37 1 52,8

E 32 14 58,4

SE 31 21 64,2

H - - -

ZONE CCLIMAT

1 1,07

2 1,05

3 1,05

4 1,00

5 1,00

6 0,96

7 0,96

8 0,93

9 0,93

𝐷𝑎𝑦𝑙𝑖𝑔ℎ𝑡 𝐴𝑢𝑡𝑜𝑛𝑜𝑚𝑦

= 𝑓(𝑆𝑉𝐹, 𝐴, 𝐵, 𝐶, 𝐷𝑒𝑝𝑡ℎ, 𝐶𝑐𝑙𝑖𝑚𝑎𝑡)

12 Bioclimatic urban planning characterization

Heating and cooling loads [kWh/m²]

Solar gains through windows [kWh]

Irradiances on the façade [kWh/m²] Mean solar

factor

Glazing ratio

Bioclimatism of an urban project

Glazing performance

Walls composition

Thermal model

Daylight autonomy [% daylight hours]

Coefficients of modulation by zone and orientations

Sky view factors from the façades

Depth of interest

13 Presentation of the model – global architecture

Tilling of the sky vault

Irradiances on the external faces of the buildings

estimation

Heating and cooling loads estimation Daylight autonomy estimation

Characterize the bioclimatism of an urban project

Sky radiance distribution Sky view factors

From the external faces of the building

Solar model

Thermal model Simplified method

14 Presentation of the solar model – Tiling of the sky vault

B. Beckers and P. Beckers, “Sky vault partition for computing daylight availability and shortwave energy budget on an urban scale,” Light. Res. Technol., 2013.

Figure – Sky partition in 145, 500 and 5000 elements

Tiles of the same aspect ratio and solid angle

Easyness of computation of the sky view factors

Easyness of navigation between tiles

15 Presentation of the solar model – Sky radiance distribution

R. Perez, R. Seals, and J. Michalsky, “All-weather model for sky luminance distribution—preliminary configuration and validation,” Sol. energy, vol. 50, pp. 235–245, 1993.

Figure – Sky diffuse Radiance distribution for an overcast sky (left) and a clear sky (right), Paris, 28th april and 1 may, 14h

16 Presentation of the solar model – Irradiances estimation

Weather data Geometry

Semantics

Tiling of the sky vault

Tiles radiances

Meshing of the external faces

View factors from mesh to mesh

Irradiances on external meshes

Direct and diffuse Irradiances

on external meshes Reflection factors

Radiosity

Sky view factors

Sun position

17 Presentation of the Thermal model – Electrical analogy

Figure - Thermal model, electrical analogy

J. H. Kämpf, “On the modelling and optimisation of urban energy fluxes,” 2009.

• Tr : inside air temperature • Text : exterior temperature • UA : conductance through the windows and ventilation • Kw1, Kw2 : conductance of the internal and external part of the wall • Ki, Ke : conductance of the thin layer of air at the internal and external wall surface • Cr, Cw : heat capacity of the air and the wall material • Qsun1 : energy flux from the sun to the external wall surface • Qsun2 : energy flux from the sun that penetrates in the room

F. Lorenz and G. Masy, “Méthode d’évaluation de l'économie d'énergie apportée par l'intermittence de chauffage dans les bâtiments. Traitement par différences finies d'un modèle à deux constantes de temps,” 1982.

18 Presentation of the Thermal model

Geometry

Semantics

Faces area Irradiances on external meshes

Mean Solar factor

Glazing ratios

Faces thermal conductivities

Faces thermal capacities

Solar gains through windows

Heating and cooling loads

Target temperatures

19 Test case – ZAC Batignolles

Urban program : • Housing : 46 000 m², • Office : 26 600 m², • Stores : 10 940 m², • School : 7 655 m², • Total : 67 195 m².

No taking into account of the climatic data on the daylight autonomy estimation, No taking into account of the glare, Heating load overestimation due to the mean solar factor, No taking into account of roof tilts on the solar active potential.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Typologies at mass plan STD at block plan

Energy consumptions (MWh/an)

Cooling

Lighting

Heating

18%

Figure - Mass plan of the Batignolles ZAC

20 Solar radiation – A quick look on cloud cover at different locations

B. Liu and R. Jordan, “The interrelationship and characteristic distribution of direct, diffuse and total solar radiation,” Sol. Energy, vol. 4, pp. 1–19, 1960.

21 Solar radiation – Light & Energy from the sky

R. Perez, R. Seals, and J. Michalsky, “All-weather model for sky luminance distribution—preliminary configuration and validation,” Sol. energy, vol. 50, pp. 235–245, 1993.

22 Light & Energy from the sky

Figure - Radiance and luminance distribution – Paris Orly, june 25th, 11h (overcast sky)

23 The concept of Useful Daylight Illuminance (UDI) and Daylight Autonomy (DA)

A. Nabil and J. Mardaljevic, “Useful daylight illuminance: a new paradigm for assessing daylight in buildings,” Light. Res. Technol., vol. 37, no. 1, pp. 41–59, Jan. 2005.

C. F. Reinhart and J. Wienold, “The daylighting dashboard - A simulation-based design analysis for daylit spaces,” Build. Environ., vol. 46, no. 2, pp. 386–396, 2011.

Figure - Illustration Of UDI (left) and DA (right)

24 Bioclimatic urban planning – Heating/cooling loads

Heating and cooling loads [kWh/m²]

Solar gains through windows [kWh]

Irradiances on the façade [kWh/m²] Mean solar

factor

Glazing ratio

Bioclimatism of an urban project

Glazing performance

Walls composition

Thermal model

Daylight autonomy [% daylight hours]

Illuminance levels on an horizontal plane

[lux]

Illuminances on the façade [lux]

Illuminances on the

interior faces [lux]

Light transmittance of the glazing

Solar protections type and positions

Windows shapes and positions

25 Adaptation of the Solar model

Geometry

Semantics

Meshing of internal faces

View factors : • mesh int <-> int • mesh int -> ext • Captors -> mesh int • Captors -> mesh ext

Global Illuminances on internal meshes and captors

Reflection factor of the internal faces

Captors positions

Windows shapes and positions

Light transmittance of the glazing

Daylight autonomy

Direct & Diffuse Illuminances on internal meshes and captors

Solar protection type

Radiosity

Glare threshold Solar mobile protections positions

Perceptive threshold

Weather data Tiling of the sky vault

Sun position

Tiles radiances Sky view factors

Luminous efficacy

Tiles luminances

26 Impact of the LoD - Illustration on simple study case

Figure - Description of the Office model

27 Impact of the LoD - solar blinds on daylight autonomy

• Active user : lowers the blinds whenever the UDI upper limit is crossed on the point at 0.75 cm from the window.

• Passive user : keeps the blinds always lowered.

Figure - Solar blinds impact on the UDI (left) and DA (right)

28 Impact of the LoD - windows positions and ground covering

Figure - Window positioning (var1) and ground covering (var2) impact on the UDI and DA

• var1 : changing the window from horizontal to vertical, • Var2 : changing the ground reflectivity from 0.2 to 0.5.

ref

var1

var2

29 Impact of the LoD - solar blinds on thermal loads

-

10,00

20,00

30,00

40,00

50,00

60,00

70,00

active user no blinds

Heating loads (kWh/m²)

• Walls composition : 20cm of concrete, 15cm of insulation • Double-glazing

Figure – Comparison of the heating load

38%

30 Conclusions and perspectives

• A methodology for a better consideration of the bioclimatic aspect of at early stages of an urban project is presented.

• The limits of this methodology are identified, especially regarding daylight access characterization.

• An adaptation of the solar model is presented in order to explore the impact of new indicators, requiring a higher LoD, on the characterization of the bioclimatism of a project.

• The results show a strong impact both on the heating loads and the daylight autonomy and justify the use of such indicators as soon as in the mass plan.

High calculations cost → PBLI ; Necessity to explore different interior configuration → Procedural modeling ; A reflection on the captors type and location needs to be conducted.

Thank you for your attention