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