PV System Design and Installation LO 9 – Mechanical Design

Mechanical Design (3% of text questions) Task/Skill 9.1. Describe the relationship between row spacing of tilted modules and sun angle, 9.2. Describe the mechanical loads on a PV array (e.g., wind, snow, seismic).

Sun – Radiant Energy PV module Shading issues Flat roof PV installations

Tilted Modules and Sun Angle Row Spacing Design/Layout Reference 2

Tilt Angle Analysis Definitions T = Module Tilt Angle (degrees) H = Module Tilt Height M = Module Width D = Module Row Distance A = Solar altitude (degrees) S = Frame distance Tangent (A ) = H / S S = H / Tangent (A)

What Sun Angle (solar altitude) do you use for design? Think Winter Solstice (9 am to 3 pm).

Right Triangle Geometry C A B A^2 X B^2 = C^2 C = Square Root (A^2 X B^2) Tangent (Angle 1) = A/B Cosine (Angle 1) = B/C Sine (Angle 1) = A/C Angle 1 + Angle 2 = 90 degrees Most calculators use radians to calculate geometric functions. To convert an “angle” to a “radian”; Radians = (3.14 x Angle) 180 Angle 1 90 degrees Angle 2

Class Exercise Calculate required distance between rows of modules on a flat roof