The past 5 years have seen a significant drop in the cost of solar PV modules. A module that cost $2.50/watt in 2009 is now available for under $1/watt. This has significantly changed the way in which solar systems are now engineered.
The old way of thinking was to maximize the output of each individual module because you were paying so much for them. You would likely engineer a mounting system that would bring the modules as close to the optimum angle as possible (53 degrees).
Now, however, with the costs being so low, you should look at maximizing your roof space. It’s no longer about maximizing the individual module; it’s about maximizing the total amount of energy your roof can produce, even at the expense of less output per module.
Lowering the mounting angle of your module will reduce its output over a year, but installing multiple rows will allow more modules to be installed since the shadow they produce will be smaller. Less shadow means tighter rows and a larger overall system.
Last year, when we designed and installed a 153 kW project, we chose a mounting angle of ten degrees in order to hit the energy target we had been given. We looked at 45 degrees, 30 degrees, 20 degrees, and 15 degrees, but none of them gave us the module density we needed to allow the roof to produce the required energy.
The Mosaic project takes it a step further with a zero degree-mounting angle—it’s perfectly flat! When it was initially proposed, we were skeptical; no one mounts solar modules at zero degrees. We started designing at ten, then five, degrees, but no other mounting angle gave us the overall roof production we need. Zero degrees gave us the module density we needed. Certainly, each module is not operating as efficiently as it could, but when looking at the roof as a whole, its energy output it maximized.
Website: Great Canadian Solar