Small Steps Into Renewable Energy: Page 3 of 4

Intermediate

Inside this Article

Stephen and his array
The author with his power system in heavily wooded, sun-scarce coastal Oregon.
Balance of system
The power wall nears completion.
System batteries
Eight Xantrex 1200-200 sealed, absorbed glass mat batteries­—400 amp-hours (20 KWH) at 48 volts DC.
Stephen and his array
Balance of system
System batteries

A large DC disconnect and Class-T fuse are between the batteries and the inverter. This switch was provided by an industrial electrical contractor friend. A battery bank of this size at 48 volts can produce significant arcing. The cutoff switch has to be capable of instantly switching such loads without worrying about arcing.

A Bogart TriMetric 2020 battery system meter allows me to accurately monitor the charge level of the batteries. This unit tracks amp-hours generated and consumed through the daily cycle. The TriMetric allows me to track every amp-hour. Experience over time reveals that this metering device is both very accurate and relevant.

Solar Input

I shopped around on the Internet and bought a pair of 165 W, 24 V Sharp Solar modules for my initial solar contribution. Later I added a pair of 185 W, 24 V Sharp modules. In strong sun, I see 9 to 12 A at 48 V. These modules were wired to a Xantrex C40 charge controller and to appropriate overcurrent protection devices, and then to the batteries.

I find that my system does just fine with four modules totaling 700 rated watts. At about US$600 per module, there is a limit to how many I really need. It is obviously a tremendous advantage to be able to supplement charging at low cost with a generator.

Solar exposure here is poor. In winter, my place has  significant morning shade. Nonetheless, I have found that my battery bank stays charged up pretty easily with the 700-watt array. While we usually have 90 to 120 cloudy days here in winter, we can also have a lot of sun. Some winters, I have probably averaged 20 minutes a day of generator charging. Last year, we had long stretches of full sun during the winter, so I hardly used the generator at all.

Wind

The Oregon Coast can get a lot of wind. While some areas of my property are exposed to wind, the location of my agricultural building is sheltered. I have experimented with both Hornet and Air-X Marine wind generators. I could not get the Hornet in strong enough wind to produce high enough voltages to charge my 48-volt system.

The Air-X Marine produces a little better in my environ-ment. I doubt that it produces one percent of my electricity, but it tends to produce exactly when all other systems are not producing anything at all, so I value its small contribution. While it is cloudy, wet, and windy when I am away from the property, the Air-X Marine may be steadily keeping up with the batteries’ self-discharge and my standing loads (1 to 2 amps).

Up to the Task

Timing has a lot to do with keeping my system well charged. I don’t have a lot of people around making random energy demands, although I do have plenty of energy in case that occurs. But I can generally choose when I use electricity. I tend to do most of the power tool usage early in the morning when the batteries are at their lowest level. With the generator running while I’m working, the batteries get charged, and the sawing and drilling get done.

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