Info

I began crunching numbers to find out how many batteries the system would need. The data revealed that I'd need at least two of the 105 amp-hour (AH), absorbed glass mat (AGM) batteries that I wanted to use (see battery sizing table). Two of these batteries in this system provide a very modest amount of energy storage. But utility outages here in southern Oregon, are few and far in between. Also, I work during daylight hours most of the year, and have the utility grid available, so I really don't need too much battery capacity.

To figure out how many PV modules were needed, I did a little more math. The formula I learned at SEI suggested that I needed 3.39 of the PV modules I had decided to use. "Hmmm," we said to ourselves. "Can we afford to round up—three modules or four?" Well, we rounded down. Three modules were enough for us to start the system. PV is modular, so whenever funds allow we can easily add to it.

System Components

The PVs we chose are Siemens (now Shell Solar) SR100, 100 watt modules. These are nice, efficient, single-crystalline modules. They're stout, easy to work with, and they have cool silicon wafer polka dots. This particular model has since been discontinued, but at the time we were buying modules, they came to us at a good price.

We bought two of them with plans to buy another soon. Our plans to buy the third module were foiled when the HP crew gave us one wrapped up as a surfboard for a wedding present. I'm glad there was a PV inside that surfboard facade because it looked way too thick and klunky to ever carve any turns on a wave.

The other key component in the system is the sealed, lead-acid, maintenance free, absorbed glass mat (AGM) battery bank. I wanted these because they are OK to house inside living spaces, as long as the batteries' terminals are protected. AGMs don't have to be vented like flooded, lead-acid batteries. This means they can live in my office and I don't have to worry about explosive and corrosive gases.

I landed two, Concorde PVX-12105, 105 AH, AGM batteries, used, for next to nothing. They were still in good

System components: Class T fuse, shunt, batteries, meter, DC breakers, charge controller, and inverter with extension cords. Note the conduit (bottom left) that brought the PV wiring in from the roof.

System components: Class T fuse, shunt, batteries, meter, DC breakers, charge controller, and inverter with extension cords. Note the conduit (bottom left) that brought the PV wiring in from the roof.

condition—despite a traumatic past—so I snatched them up. In their previous life, they were part of a stand-alone PV system for HP Central's remote, off-grid radio telephone communication system. One day, some dishonorable scumbag stole the two, 75 watt PVs that charged this system. The batteries held up for a while, but eventually went dead from giving all their chemically stored energy to the repeater. After being removed, they were nursed back to life over several months. Now they're living a second life in our system.

The batteries, other system components, and breakers live in a wooden box Tiffany and I found at a junk store. Because all the components fit in or on the box, this half of the RE system can be moved easily with a hand truck.

On one side of the box, a Statpower ProSine 1000, 1,000 W inverter provides all the AC power my office will ever need, with significant room for expansion. My computer equipment likes its sine wave output. I like its easy-to-read digital display and two GFCI receptacles.

An RV Power Products Solar Boost 50 (SB50), 50 amp (A) charge controller, two DC-rated 30 A breakers in a Square D two-circuit box, and a Cruising Equipment E-Meter (now Xantrex Link-10) are mounted on the front of the wooden box. We chose the SB50 because we wanted a maximum power point tracking (MPPT) charge controller that we could grow into. The two breakers allow us to safely isolate any one current source in the system for maintenance, removal, transport—whatever. The E-Meter measures the amp-hour activity of the batteries. I like this meter because it tells me the system's status at a glance. I have it in scroll mode so I can see what's going on from across the room at my desk.

Installation Day

Before we installed the system, we had an impressive heap of renewable energy (RE) gear in the garage. It was pretty cool to look at, but the real fun began when we started to put it all together. I enlisted our friend Joe Schwartz to give me a hand. Start to finish, it only took us about six hours to install the system.

The first step was to install the PVs on the rack before we hoisted them up on the roof. We bolted them to the 11/8 inch (29 mm) galvanized, angle iron rack, using stainless steel hardware with lock washers. Then we wired the PVs up in parallel with #10 (5 mm2) THWN-2 CU wire in Liquidtight conduit. We checked the module's short circuit current (Isc) and open circuit voltage (Voc) as we went to make sure the panels were working and wired properly. Then we climbed up on the roof to prep it for the array.

The patio roof is built with 4 by 4 posts and 2 by 4 rafters. The roofing material is translucent, corrugated, fiberglass sheets. These sheets are affixed to the 2 by 4s with 1 inch (25 mm) "wiggle molding" below and above. I laid down a few 2 by 12s on the wiggle molding so we could walk around on this fragile roof.

With the 2 by 12s providing a safe working surface, we lifted up the array. Lifting up the rack with the PVs installed was hard work, and a bit awkward. But once we got the

Grisen PV Syste:

Photovoltaics:

Three Siemens SR100, 100 W each, wired for 300 W total at 12 VDC

Photovoltaics:

Three Siemens SR100, 100 W each, wired for 300 W total at 12 VDC

Charge Controller:

RV Power Products

Breakers:

Two 30 A

Charge Controller:

RV Power Products

Breakers:

Two 30 A

Amp-hour Meter:

Cruising Equipment E-meter

Amp-hour Meter:

Cruising Equipment E-meter

Fuse:

110 A, Class T

Shunt

Shunt

Inverter:

Statpower ProSine 1000, 1,000 W, 12 VDC Input 120 VAC sine wave output

Inverter:

Statpower ProSine 1000, 1,000 W, 12 VDC Input 120 VAC sine wave output

Note: All numbers are rated, manufacturers' specifications, or nominal unless otherwise specified.

System' Loads

Note: All numbers are rated, manufacturers' specifications, or nominal unless otherwise specified.

Grisen System Costs

Item

3 Siemens SR100 modules, 100 W

Xantrex ProSine 1000 inverter, 1,000 W

2 Concorde PVX-12105 batteries, 105 AH

SolarBoost 50 charge controller, 50 A

Cruising Equipment E-Meter

Cables, wire, conduit, J-box, disconnects

Steel & misc. hardware for PV mount

Trace TFB110 fuse, class T, 100 A

Shunt, 50 mV 500 A

Battery box, used

DIY Battery Repair

DIY Battery Repair

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