AEBF01: L5 Sun and climate

Helena Bülow-Hübe 1

F5: Solar angles and climaticpre-conditions

Architectural design regardingthe outdoor climate

Why do we have so little sunduring the winter?

Solar paths Solar anglesSolar height h, Azimuth (bearing) a

h

a

Lund 56°N

90°/270 °

Lund 56°N57,7°

10,8°

Paris: 48°N, Madrid: 41°N, Shanghai 31°N, Waterloo 43°N,

AEBF01: L5 Sun and climate

Helena Bülow-Hübe 2

Calculation of solar heightand azimuth

tcoscosdcossindsinhsin ⋅⋅−⋅= ϕϕhcos)tsind(cosasin ÷−=

h = solar heighta = azimutht = time angled = declinationϕ = latitude for the site(All angles in the same unit, eitherdegrees or radians)

Rule of thumb

• Solar height at noon (12) = 90° −latitude of site ± declination*

* The declination = the angle of the earth axis in relation to the solar path, -23° at winter solstice, 0° at the equinoxes and +23° at summer solstice.

True solar time

The sun is always highest in the sky at 12.00 true solar time!

Solar height and azimuth

Stereographic projection Solkarta Question:Solar heightand azimuthon April 15 at 9 o’clock?

Answer:h = 33°a = 124°

AEBF01: L5 Sun and climate

Helena Bülow-Hübe 3

Solinstrålning

Direkt från solen - direktstrålning Reflekterad från luftens partiklar –himmelsstrålning, alt diffus strålning

• Direkt solstrålning mot normalen, IN

• Diffus solstrålning, IdH

• Global solstrålning (direkt + diffus) mot horisontalen, Ig

• Markreflekterad strålning

IN

IdH /IgBeam irradiance (W/m²)

0

200

400

600

800

1000

1200

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Lund

Stockholm

Luleå

January 1988

JanuariOutdoor temperature (°C)

-30

-25

-20

-15

-10

-5

0

5

10

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Lund

Stockholm

Luleå

January 1988

Utomhustemperatur

Direkt solstrålning

MarsOutdoor temperature (°C)

-25

-20

-15

-10

-5

0

5

10

15

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Lund

Stockholm

Luleå

March 1988

Beam irradiance (W/m²)

0

200

400

600

800

1000

1200

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Lund

Stockholm

Luleå

March 1988

Utomhustemperatur

Direkt solstrålning

JuniOutdoor temperature (°C)

-5

0

5

10

15

20

25

30

35

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Lund

Stockholm

Luleå

June 1988

Beam irradiance (W/m²)

0

200

400

600

800

1000

1200

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

LundStockholm

Luleå

June 1988

Utomhustemperatur

Direkt solstrålning

Diffus solstrålningDiffuse irradiance (W/m²)

0

100

200

300

400

500

600

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Lund

Stockholm

Luleå

March 1988

Diffuse irradiance (W/m²)

0

100

200

300

400

500

600

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

LundStockholmLuleå

June 1988

Diffuse irradiance (W/m²)

0

100

200

300

400

500

600

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

LundStockholmLuleå

September 1988

Diffuse irradiance (W/m²)

0

100

200

300

400

500

600

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Lund

Stockholm

Luleå

December 1988

Accumulated solar radiation towardsvertical surfaces for var. outdoor temp.

Årlig ackumulerad solinstrålning (kWh/m²)

0

100

200

300

400

500

600

700

800

900

1000

-15 -10 -5 0 5 10 15 20 25 30

Utetemperatur (°C)

SöderÖsterVästerNorrHorisontellt

Stockholm

430

AEBF01: L5 Sun and climate

Helena Bülow-Hübe 4

Strategy 1: Minimize lossesthrough the building envelope

-1500

-1000

-500

0

500

1000

1500

J F M A M J J A S O N D

Uppvärmning

Utnyttjadsolvärme

Utnyttjadbovärme

Ventilation

Transmission

Energibalans (kWh/mån)

Relationship between:• enclosing area to volume, Aenc/V

• enclosing area to floor area, Aenc/Aheat

Form

Aenc= 217m²V = 300 m3 0,72

Aenc= 270 m²V = 300 m3 0,9

Aenc= 350 m²V = 300 m3 1,17

Aenc / V

Scale

1 Aenc= 6 m²V = 1 m3 6

Side

100 Aenc= 60.000 m²V = 1.000.000 m3 0,06

10 Aenc= 600 m²V = 1000 m3 0,6

Aenc / V

Single-family separate house

Row houses

Multi-family dwellings

AEBF01: L5 Sun and climate

Helena Bülow-Hübe 5

Strategy 2: Solar utilisationSolar radiation towards

vertical surfaces

Idea: Long facade or glazed spacetowards south?

2 storeys increases the facadetowards south, less shading

Intelligent solar shading

summer spring, autumn

Fixed or movable solar shading?

AEBF01: L5 Sun and climate

Helena Bülow-Hübe 6

Daylight or solar radiation?

A fixed screen, balcony or similar can make the rooms unpleasantly dark

The reflectance of inner surfacesmainly affects the rooms lightness

Surfacereflectances

The reflectanceof the ground

Grouping of houses

Solar studies in models

Pleijel’s sun dial

Shadow length

AEBF01: L5 Sun and climate

Helena Bülow-Hübe 7

FEB 13.00FEB 10.00

From Sketch-up APRIL 9.00 APRIL 12.00

JUNE 9.00 JUNE 12.00

Plan for sun and wind

Source: Sol Energi Form

Strategy 3: Build air-tightbuildings!

• Increased cooling ���� the outer surfaceresistance is reduced transmission lossesthrough walls etc increase slightly, largesteffect in poorly insulated parts like windows, solar panels, green houses

• Increased air leakage through cracksand untightnessesincreased air-change gives higher ventilation losses

Effect of increased wind speeds at normal infiltration rates

Känslighetsanalys av en variation av vindreduktione n

0

20

40

60

80

100

120

140

0 20 40 60 80 100

Andel (%) av vindhastigheten i klimatfilen som anvä nds i beräkningen

Ene

rgia

nvän

dnin

g ex

kl. h

ushå

llsel

(k

Wh/

m2år

)

Källa: Sundquist & Allansson, 2005

Summary

• Minimize losses ���� Build well-insulated buildings

• Minimize losses ���� Build air-tightbuildings

• Utilise ”free” energy ���� Utilise solar energy

• Plan the outdoor environmentregarding sun and wind