Thursday, December 1, 2011

Solar Panels: That Simple?

When installing solar panels, you stagger the rows so that one row of panels does not shade the next. And, of course, it makes sense to tilt them towards the sun. That simple? Nope. Throw in a few more factors like limited area for the array installation, the limitations of the rack systems, the relative cost of more and less efficient panels, and the surprisingly small reduction in efficiency if the panels are not at the optimal angle to the sun and another, better route emerges.

For the array that we are installing on our commercial building in Durham, we made choices that yield a cost-effective solution but that seem counter-intuitive. While slightly more complicated than this, our options boiled down to two alternatives that both exceeded our energy generating goals. Option one: expensive and highly efficient panels installed in consistent and optimally tilted rows. Option two: a larger quantity of considerably less expensive and somewhat less efficient panels installed mostly in consistent and optimally tilted rows but with two leading rows that are not tilted towards the sun. In fact, they are tilted slightly to the north. The lack of tilt allowed us to install the first rows more compactly without shading the next row. We picked option two. Option two delivers slightly more power. Option two saves over $40,000 in up-front costs. Not bad. Our only concern is hearing the comment: “Hey, Mr. Solar Intelligence, the sun is to the south.” To those folks, I’m happy to tell this story, enjoy the clean energy, and put the money in the bank.

For any energy geeks (this term used endearingly) reading this, the first rows of panels are on a separate inverter so the reduced output from these rows does not degrade the output from the optimally tilted rows. Option two schematic roof panel layout shown below.