Sunday, November 4, 2007

The Solar System

Not THE solar system, rather details about the photovoltaic (PV) solar system that we are having installed.

We are getting a 4kW array made up of 20 Sanyo 200W 36"x52"Panels. The panels are arranged in 4 strings of 5 panels each electrically and 4 rows of 5 portrait panels physically.

We'll be using an SMA Sunnyboy 6000 U inverter. This is an over-sized inverter to allow for more panels later if we want (and can afford) more solar power.

So how much electricity can we expect to generate? There are several factors including region, shading, & angle to consider.

Our house does not have a south-facing roof and we don't live in sunny California or Arizona. It is less than the perfect place for solar. However, I believe in the motto, that one should not allow that which you can not do, to prevent you from doing that which you can. Or said another way, "the perfect should not be the enemy of the good." We'll have a good solar installation, because that is what we can do.

We live in Beaverton, Oregon, a suburb of Portland. The Local Production Capacity 1.08 kWh/W*Yr. If you are in the lower 48, you can look at this chart to see how NW Oregon compares to your part of the country.

When south-facing array is not an option, west-facing is preferred to east-facing since early morning sun hours are often blocked by cloud cover that burns off by late morning or early afternoon. West facing lowers our efficiency by 14% compared to south. We could have angled the panels of of our roof to point true south, but this would have required a much more expensive installation. It is cheaper to just install 14% more panels to compensate for the angle loss.

Given our region, angle, shading & array size, our system should generate about 3.7 Megawatt hours per year of electricity. This is about one 3rd of the electricity that our home uses. We are going to start an electricity conservation program to see if we can increase the percentage of our power usage that we get from the PV system; expect to see this as a future blog topic.

No comments:

Post a Comment

Note: Only a member of this blog may post a comment.