SOLAR POSITION

Sun’s movement through the day/year is a critical environmental factor that needs to be understood to design a high performance building

Planned correctly, you can take advantage of the sun’s path Natural daylighting Passive heating Photovoltaic energy generation Natural ventilation

SOLAR POSITION Altitude – vertical angle the sun makes with

the ground plane Azimuth – horizontal angle between the sun and true north (-180 degrees, 180 degrees, positive in a clockwise direction from north)

SEASONAL VARIATIONS/IMPORTANT DATES

Sun’s path varies throughout the year Summer – sun is high and rises/sets

north of east-west (northern hemisphere) south of east-west (southern hemisphere) Rises much earlier and sets much later in

the summer than the winter To plan for the extreme heat in the

summer study the summer solstice Sun is at its highest noon altitude

SEASONAL VARIATIONS/IMPORTANT DATES

Winter sun is low in the sky Rises/sets south of east-west (northern

hemisphere) Rises/sets north of east-west (southern

hemisphere) To study extremes of winter look at the

sun’s path during winter solstice, sun is at its lowest noon altitude

SEASONAL VARIATIONS/IMPORTANT DATES

To study more average positions look at the sun’s path on the spring and autumn equinoxes, sun rises and sets due east-west

Altitude of the noon sun at the equinox is determined by the latitude of the site

Rule of thumb for optimum angle of solar panels is the latitude of the site, rays are most perpendicular to the panel for most of the year

TIPS/RULES OF THUMB Study particular days

Solstices: extreme of the sun’s position Equinoxes: average sun position

Study different seasons: Winter studies – How to maximize sun to

passively heat the building Summer studies – How to minimize sun to

passively cool the building

DATES TO REMEMBER

LOOK AT SOME SPECIFIC TIMES OF DAY Morning – try to capture the sun’s energy

to warm up spaces when the sun is low in the sky, need to protect against glare

Noon – Strongest and highest in the sky. Avoid hot midday sun to reduce cooling loads. May want to capture the sun for passive solar heating/energy generation

Afternoon – Prevent overheating/glare Occupancy hours – Think about when the

building is used most

STEREOGRAPHIC SUN PATH DIAGRAMS Used to read solar azimuth and altitude

throughout the day Like a photograph of the sky, looking

straight up towards the zenith with a 180 fish-eye lens

Paths of the sun at different times of the year can be projected onto this flattened hemisphere

HOW TO READ STEREOGRAPHIC SUN PATH DIAGRAMS

Used to read solar azimuth and altitude Azimuth lines- angle lines run around the edge

of the diagram Altitude lines – represented as concentric

circular dotted lines that run from the center out Date lines – Start on the eastern side of the

graph and run to the west. Represent the path of the sun on one particular day of the year

Hour lines/analemma – shown as figure 8 lines that intersect the date lines and represent the position of the sun at a specific hour. Intersection between date and hour gives the suns position

READING THE SUN POSITION Locate the required hour line on the diagram Locate the required date line (solid lines are Jan-June

and dotted July-Dec Find the intersection point of hour and date lines (solid

with solid, dotted with dotted) Draw a line from the very center of the diagram

through the intersection point to the perimeter Read the azimuth angle take clockwise from the north Trace a concentric circle around from the intersection

point to the vertical north axis, displays altitude angle Interpolate between concentric circle lines to find

altitude Gives suns position as defined by azimuth and altitude