Solar angles Solar height h, Azimuth (bearing) a

Transkript

1 AEBF1: L5 Sun and climate F5: Solar angles and climatic pre-conditions Why do we have so little sun during the winter? Architectural design regarding the outdoor climate Solar paths Solar angles Solar height h, Azimuth (bearing) a h a 56 N 56 N 57,7 1,8 9 /27 Paris: 48 N, Madrid: 41 N, Shanghai 31 N, Waterloo 43 N, Helena Bülow-Hübe 1

2 AEBF1: L5 Sun and climate Calculation of solar height and azimuth sin h = sin d sinϕ cos d cosϕ cos t sin a = (cos d sint ) cos h h = solar height a = azimuth t = time angle d = declination ϕ = latitude for the site (All angles in the same unit, either degrees or radians) Rule of thumb Solar height at noon (12) = 9 latitude of site ± declination* * The declination = the angle of the earth axis in relation to the solar path, -23 at winter solstice, at the equinoxes and +23 at summer solstice. True solar time The sun is always highest in the sky at 12. true solar time! Solar height and azimuth Stereographic projection Solkarta Question: Solar height and azimuth on April 15 at 9 o clock? Answer: h = 33 a = 124 Helena Bülow-Hübe 2

3 AEBF1: L5 Sun and climate Solinstrålning Outdoor temperature ( C) 1 5 January 1988 Januari -5-1 Direkt från solen - direktstrålning Reflekterad från luftens partiklar himmelsstrålning, alt diffus strålning I N Utomhustemperatur I dh /I g Direkt solstrålning mot normalen, I N Beam irradiance (W/m²) 12 January Diffus solstrålning, I dh Global solstrålning (direkt + diffus) mot horisontalen, I g Markreflekterad strålning Direkt solstrålning Outdoor temperature ( C) March 1988 Mars Outdoor temperature ( C) June 1988 Juni Utomhustemperatur 5-5 Utomhustemperatur Beam irradiance (W/m²) 12 March Beam irradiance (W/m²) 12 June Direkt solstrålning 6 4 Direkt solstrålning December Diffus solstrålning June March September Accumulated solar radiation towards vertical surfaces for var. outdoor temp Årlig ackumulerad solinstrålning (kwh/m²) 43 Söder Öster Väster Norr Horisontellt Utetemperatur ( C) Helena Bülow-Hübe 3

4 AEBF1: L5 Sun and climate Strategy 1: Minimize losses through the building envelope 15 Energibalans (kwh/mån) Uppvärmning Utnyttjad solvärme Utnyttjad bovärme Ventilation Transmission J F M A M J J A S O N D Relationship between: enclosing area to volume, A enc /V enclosing area to floor area, A enc /A heat Form A enc / V A enc = 217m² V = 3 m 3,72 A enc = 27 m² V = 3 m 3,9 A enc = 35 m² V = 3 m 3 1,17 Side Scale 1 A enc = 6 m² V = 1 m 3 6 A enc / V 1 A enc = 6 m² V = 1 m 3,6 Single-family separate house Multi-family dwellings 1 A enc = 6. m² V = 1.. m 3,6 Row houses Helena Bülow-Hübe 4

5 AEBF1: L5 Sun and climate Strategy 2: Solar utilisation Solar radiation towards vertical surfaces Idea: Long facade or glazed space towards south? 2 storeys increases the facade towards south, less shading Intelligent solar shading summer spring, autumn Fixed or movable solar shading? Helena Bülow-Hübe 5

6 AEBF1: L5 Sun and climate Daylight or solar radiation? The reflectance of inner surfaces mainly affects the rooms lightness A fixed screen, balcony or similar can make the rooms unpleasantly dark Surface reflectances The reflectance of the ground Grouping of houses Solar studies in models Pleijel s sun dial Shadow length Helena Bülow-Hübe 6

7 AEBF1: L5 Sun and climate From Sketch-up APRIL 9. APRIL 12. FEB 1. FEB 13. JUNE 9. JUNE 12. Plan for sun and wind Source: Sol Energi Form Strategy 3: Build air-tight buildings! Increased cooling the outer surface resistance is reduced transmission losses through walls etc increase slightly, largest effect in poorly insulated parts like windows, solar panels, green houses Increased air leakage through cracks and untightnesses increased air-change gives higher ventilation losses Effect of increased wind speeds at normal infiltration rates Energianvändning exkl. hushållsel (kwh/m 2 år) Känslighetsanalys av en variation av vindreduktionen Andel (%) av vindhastigheten i klimatfilen som används i beräkningen Summary Minimize losses Build wellinsulated buildings Minimize losses Build air-tight buildings Utilise free energy Utilise solar energy Plan the outdoor environment regarding sun and wind Källa: Sundquist & Allansson, 25 Helena Bülow-Hübe 7