Installation began during the last week of October 2011. First steps were to install supporting rails to the roof surface:
These rails were fastened to the standing seams of the metal roof with heavy aluminum clamps, as can be seen here:
Individual 240W photovoltaic panels were then fastened to the rails as can be seen here:
An individual panel is shown here:
A total of 66 panels were installed and connected to common cabling. Owing to the hillside location of the house, the array of panels can be seen only from the air.
A conduit running down through the roof and along an exterior wall connects power from the solar panels to a pair of inverters shown here:
The inverters have several functions. Output of the solar panels fluctuates depending on the amount of sunlight they receive. The inverters transform this output, converting direct current from the solar panels to the alternating current used by household electric wiring, and synchronizing the phase and frequency of their output to that of the CPS grid voltage.
The inverters also monitor utility current and are programmed to shut down when grid voltages fall outside standard limits. This is particularly important in the case of grid power failure when contact with solar system voltage could be dangerous for electric utility crews.
Cables running through our crawl space connect the inverters to a pair of CPS service panels where power comes to the house from the grid:
The photo shows two electric meters – the one on the left registers current from the solar system; the meter supplied by CPS is on the right. The box on the far left houses a manual cutoff switch which disconnects the solar system when servicing is required.
AC current from the solar system is kept at a slightly higher voltage than current from the grid so that solar power is used preferentially whenever it is generated. The grid supplies power to the house whenever household demand exceeds solar power production. This sharing of power supply is continuous and imperceptible within the house.