Solar panels on the wall

At first glance, an unused area is the right place for mounting solar panels. If we go by the logic that every free space in the urban environment should be used to collect solar energy, then a south-oriented vertical wall is a real mine of pure free energy.

Many facades of buildings and high-rises in large cities facing partly south unnecessarily absorb sunlight and heat the walls. This absorbed light could instead be harnessed to generate electricity.

In the following consideration, I will run comparative calculations with the SPAC application to explore potential expectations.

The task of this post is to evaluate the benefits of installing solar panels vertically on the walls of buildings or houses.

• For optimal solar energy production, panels must be installed on a south-facing wall free from any shadow cast by surrounding structures.
• Larger adjacent buildings block solar capture completely along the east-south-west route. Lower buildings nearby may also shadow the lower sections of the facade.
• Sunlight falls at azimuth angles between 0 and 110 degrees depending on latitude and time of day. Lower solar angles during winter favorably complement the geometry of vertically mounted panels, keeping the angle of incidence closer to perpendicular.

We begin by analyzing an ideally placed building with south-facing walls and no shading effects from surrounding structures or trees.

For this test, we select the latitude of Chicago and 10 solar panels rated at 400 W each. We then compare these results with optimally tilted setups at 45° and 30°.

Comparison against 45° and 30° inclinations shows the following monthly and annual production metrics (kWh):

Chart comparison: Blue bars represent wall-mounted vertical panels.

While standard tilted arrays show linear variations across seasons, vertical installations yield a unique double-peak distribution graph.

1. Reflected and diffuse components

Standard tilted arrays capture limited ground-reflected light. Vertical wall installations are far more effective at capturing reflected radiation, as well as diffuse light during high sun angles.

For example, in January, direct light dominates (diffuse: 3%, reflected: 4%). In June, when high sun angles penalize direct capture on vertical surfaces, diffuse radiation contributes 15% and reflected radiation provides 12% of overall collected energy.

2. Monthly incident angle at solar noon

Low winter sun provides favorable geometry for vertical panels, though shorter day lengths cap maximum output. Production peaks in March, declines sharply to a minimum in May/June, rises back to an annual peak in October, drops through November/December, and recovers through January. This establishes two primary production peaks—early spring and early autumn.

3. Monthly energy gains, ups and downs

Notable peak monthly productions occur in January (62.55 kWh) and August (63.54 kWh). The sharpest output reductions occur in April (79.98 kWh drop) and November (108.54 kWh drop).

With declining panel prices, facade mounting becomes increasingly feasible, despite payback periods extending up to 40% longer than optimally tilted arrays.