Solar System Description


This solar electric system is rated at 3048 watts. It was built in 2 stages. The first stage was the 1548 watt roof mounted array and associated hardware. It was installed in 1998. The second stage was the addition of the 1500 watt tracking array. This was installed in December 2002. The system operates at 48 volts using a Trace sine wave inverter. This inverter produces a sine wave of AC electricity from the DC power made by the solar panels, which is used in the house or sold back to the electric utility. The inverter can also be powered by the battery bank if they utility grid goes out. This lets dedicated house loads continue to operate without interuption. The rest of the equipment consists of fuses, breakers, charge controllers and meters to measure the electricity that the solar panels generate.

The Roof Array

The roof has 36 panels installed on it. 24 panels are on the upper back roof and face south east. The other 12 panels are on the family room roof and face south west. Each panel is rated at 43 watts. They are designed for a 48 volt dc system. These panels are the MST-43 type, made by Solarex. Electrically, the panels are all connected in parallel. They are made of amorphous thin film type of silicon as opposed to the more common crystalline type of silicon. The thin film type of panel is less efficient than the crystalline type of panel.
 

The Tracker

The tracker is a dual axis tracking device that keeps the solar panels pointed at the sun all day long. It has ten 150 watt panels manufactured by BP Solar. Each BP-SX150 panel is rated at 24 volts dc. The tracking hardware senses where the sun is and uses low power DC motors to position the array so that the panels are always pointed towards the sun. The array is adjusted in the east-west position first and the vertical position last. On cloudy or semi-cloudy days, the array might be found in "table-top" mode, pointed up at the clouds. It moves about every 5 minutes or so on a sunny day. At the end of day, it rotates back to facing east and waits for the sun to rise again. By tracking the sun in this manner, about 30% more power can be received compared to a fixed position array.

The Power Center

The power center conists of a 4000 watt sine wave inverter made by Trace Engineering, charge controllers, breakers, meters and batteries. The system is configured to sell back unused power in an arrangement known as net-metering. I have the inverter connected to dedicated loads such as the refrigerator, freezer, family room, computer and alarm. The utility grid normally powers up these loads, but if it goes out, the inverter instantly takes over making electricity from the batteries and or solar panels. The computer and TV don't even know that the utility has gone down. I also have installed a transformer to step up the 120 VAC to 240 VAC so that I can power up our well pump if necessary. I would have to manually turn on the transformer to accomplish this though.

This system is located in south eastern Pennsylvania.

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