Thursday, March 10, 2005


Ordering the Equipment!

Yesterday, I ordered the 80 Uni-solar shingles from the Alternative Energy Store in Massachusetts. The shingles are rated at 17 watts each, for a total nominal solar power rating of 1360 watts. The shingles will be installed on my south-facing front roof. Each shingle has two wires which will pass through 1-inch holes in the roof base. They will be wired in series strings of 8, which will then be linked in parallel to two wires carrying approximately 72 volts.

The wires from the shingles will run through conduit from my attic to my basement, where they will connect with an Outback MX60 charge controller.

The charge controller regulates the voltage to the batteries, enabling quick charging and protecting them from overcharging. The MX60 allows for input voltages substantially higher than the battery voltage--the 72 volts from the shingles will be charging a 48-volt battery bank.

The batteries will power an inverter, the Outback FX2548, which converts 48-v DC power into 120-v AC. This will then be connected to my household breaker panel, providing power to my household outlets. The inverter will also be connected to the grid so that when the batteries are low I will be able to switch to grid power. When this happens, the inverter doubles as a battery charger, allowing me to recharge the batteries while running my house from the grid. Hopefully this won't be necessary too often--probably just a few long, cold winter nights each year.

The Alternative Energy Store is putting together a bid for me to combine all of the various Outback devices--charge controller, inverter, system monitor and control, and a variety of connectors, breakers and disconnects--onto a single pre-assembled panel. Whether I go with this method or order the parts separately will depend on the relative cost and the advice of my electrical specialist, Rick.

Batteries are my biggest remaining wildcard. Batteries are expensive, heavy, and require periodic maintenance (unless you go for much more expensive). I'm torn between buying lots of batteries, enough to get me through five days without sun, or economizing and relying on the grid when the going gets cloudy. I'm going to check with a few people to see if I can get a good deal on some slightly-used batteries.

Anyway, I'll be posting photos and updates on my progress on this blog from time to time. If you have questions, you can leave comments here or e-mail me.
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