sunMAX - How is Production affected by Shading, Tilt & Orientation?

Overview

Production is dependent on available power at the solar array. Power and current (irradiance) are directly related via (P = I * V).

To maximize irradiance exposure and therefore increase production, the array should be installed free of shading, at the best possible tilt and orientation. Both tilt and orientation of the sunMAX Residential System are fixed (static) by design.

Shading

Shading occurs wherever and whenever direct sunlight to the array is blocked. Usually from trees, buildings, etc. A good principle to follow is only install arrays where there is direct sunlight available all day-time hours.

During a site survey, you may discover there is minimal shading on areas (particularly edges) of the array. When deciding whether a section of the array is viable for installation, take into account all variables, including hours of shading, kWh costs, and more.

Tilt

Optimum tilt (also called angle, slope, pitch) depends on the location (geographic latitude) of each customer. The farther from the equator  (0° latitude), the greater the tilt requirement becomes when 'capturing' sunlight.

The roof mounting system of the sunMAX Residential System matches pitch of the customer's rooftop. So if the customer rooftop has a pitch of 15°, then the array will also be aligned at approximately 15°.

Orientation

Optimum orientation refers to the cardinal direction at which the tilted array should point (that is, face/align) to produce maximum power.

At the equator (0° latitude) the orientation is irrelevant, since panels are mounted flatly—that is, without tilt. However, as one moves away from the equator in either direction, the panels should be facing 'true' South (in the Northern Hemisphere), or, 'true' North (in the Southern Hemisphere). 'True' South/North differs from 'magnetic' South/North.

A good general rule is to only install on rooftops that are South-, Southeast-, or Southwest-facing in the Northern Hemisphere; vice-versa in the Southern Hemisphere.

Examples

Example 1

To achieve maximum solar efficiency in San Francisco, United States, an array should point toward 'true' South (that is, 13° East of South) at roughly 31° tilt.

Example 2

A Maryland Utility charges customers according to Time-of-Use, where 1) Off-Peak = 8¢/kWh, and, 2) Peak = 12¢/kWh.

In general, a rooftop that faces both East and West will produce equivalent energy on either side. However, because the sun rises East (morning, during off-peak rates) and sets West (afternoon, during peak rates), it is economically better to install on the West rooftop.

Example 3

The following screenshots present a 24% difference in annual production levels between two separate 15° tilt array simulations in the Northern Hemisphere (Baltimore, United States):

South-facing (ideal; 5148 kWh/annually)

North-facing (poor; 3912 kWh/annually)