Tuesday, November 2, 2010

Solar Panels on Frosty Morning

An interesting thing regarding solar panels is their configuration or setup. Our 525 panel array is configured so that several panels are connected in series as a "string", and then combined with other strings to send their DC current to an inverter where the output becomes AC current.

One design challenge is that the panels in that string need to be working well together. If 3 out of 7 panels in a string are not functioning - the entire string is unable to make production. On Nov1, we had an exceptionally clear and cold day. The panels had a frost that settled on them, and with the early morning sun rising clearly and slowly, the melt of the frost followed the shadow line as the sun rose in the sky. As you can see by the above photo, that meant that some panels, though being struck by sunlight, were unable to pass along their energy generation because other panels in the string were not producing energy due to frost blocking the light.

One solution to this is micro-inverters that would convert the DC current on each individual panel into AC current. It is an interesting concept, which this NYTimes article discusses more.

The photo is from 8:30am, and the array kept going in and out of operation as the sun glinted just enough light and energy on the threshold of operating. During the day total, there were 452kwh generated, the most in nearly a month.

As of Nov1, the array has generated all electrical needs for the company, even with us switching gas heaters to electric and adding an electric car that charges it's battery here. In fact, the array generated all the needs, and created excess of over 14,000 kwh. The credit of kwh generated and pushed to the grid beyond our consumption pulled from the grid, will be drawn down upon during the winter months when we do pull more than is pushed to the grid.