Let’s calculate the shadow length of building ‘B’ on building ‘A’. Height of building B is 8 m and height of building A is 5 m. Distance between buildings is 2 m. Buildings are located in Delhi, India.
Step 1: Altitude and Azimuth Angles
Since the shadow creating object (i.e. Building ‘B’) is on east side of proposed solar roof (i.e. Building ‘A’). Hence, it will cause shadow during morning hours. Therefore, Altitude and Azimuth angles were considered for morning hours i.e. 10 am for Delhi location and 21st December (Winter Solstice).
Using www.sumposition.info, Altitude and Azimuth Angles were derived:
Altitude Angle: 28 Degree, Azimuth Angle 142 Degree
Step 2: Relative height of Shadow creating object
Height of Shadow creating object (Building B) is 8m. Height of building where solar PV array is proposed (Building A) is 5m.
Hence, relative height of a shadow creating object = 8 – 5 = 3 m
Step 3: Shadow Length (m)
Using below formula, for East-West shadow profile:
Shadow Length (m) = H (m) x [ Sin (Azimuth) / Tan (Altitude) ]
Shadow Length (m) = 3 x [ Sin (142) / Tan (28) ] = 3.5 m
Hence, 3.5 m shadow distance need to be left from Building B in West direction.