Description of the PV system.

To accomplish a retrofit, such as this, one might start with a careful site evaluation. Solar, Wind, and Water are some sources of renewable energy. The wind where I am is gusty and not dependable and there is no running water on the property. There are a lot of trees, making solar a tough venture, but the only real option.

The idea in my mind was to gradually increase the amount of solar PV and heat collection and increase efficiency in the energy consuming items until the collection exceeds the energy consumption and the home is completely operable on solar.

I quickly realized that half the roof faced magnetic south, which is only a few degrees from true south in this location. South is pretty much the sunny side of the world in the Northern hemisphere. The direction the roof faces made roof mounted PV a viable option. This would put the panels above the shading from the trees for most of the year. Solar PV would produce electricity, solar hot water could heat water for domestic hot water use and radiant heating, and solar hot air collectors could also help heat the residence.

Since I am operating on a limited budget, I decided to start my own "panel of the month club". This is a method suggested by one author in a Home Power magazine article, where the individual purchases and installs panels one at a time until they achieve the desired level of energy capture for the given loads.

In March I obtained 8 Solarex MSX120's, a SW4048 and a c-40 charge controller. The MSX120 is a 120 watt solar panel produced by a company named Solarex in Frederick, Maryland. The SW4048 is an inverter which will convert up to 4000 watts of the solar panel DC electricity into the regular house flavor of 120 volts AC electricity. The C40 is a "charge controller" which will regulate the electricity from the solar panels into the batteries which store it for when the sun is not shining.

There were a bunch of snags. First, I had a lot of trouble getting on and off the roof. Not that my roof was steep or hard to get on, but I had a big fear of walking around that high off the ground. Secondly, I wired up the first set of panels incorrectly for 24 volts instead of the 48 volts I am using. Then I had not installed blocking diodes in the panels. After trying to rewire one panel on the roof, I decided to bring them down, rewire them, and put them back up. After rethinking things, I decided to wire the panels for 24 volts into the attic and series them to 48 volts in the attic. This way I could monitor each panel individually from the attic and ensure they were all performing to specs.

A month or two later I added another 8 MSX120's four batteries and a second c40 charge controller. A couple months later I added another four batteries and the required PV ground fault protective breaker for roof mounted PV, a 400 amp fuse for the battery bank and a central disconnect. I took my time installing all this stuff and it was getting toward autumn by the time I had it all up and connected.

In December I was able to obtain 12 more MSX120's, bringing the system to an almost respectable size.

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