Info

Total

Less 2008 Federal Tax Credit Grand Total

$14,981

2,000

$12,981

communicate via the system's 240 VAC output wires to the service panel. We mounted the Enphase Envoy communications module in the house. It picks up the inverters' communication signals through the AC wall outlet that the module is plugged into and exports the data to our network router. From there, the data communicates to Enphase servers for near real-time display on Enphase's Enlighten Web site. No communication wire is needed to the roof or between inverters, making this the easiest Web-based data monitoring system that we've installed. The Web-monitoring system requires a broadband connection, but the Envoy can also communicate through a LAN and information viewed by typing an IP address into an Internet browser.

The data monitoring system shows information common to most other systems: instantaneous power, daily and monthly

Wire Ties" sidebar). After securing all the inverters and wire, the continuous bare copper grounding wire was connected to the grounding clip on the top of every microinverter.

We connected an Enphase AC home-run cable to the last inverter. The cable was terminated with a 240 VAC heavy-duty toggle switch in a weatherproof enclosure, as a roof-mounted AC disconnect to shut down the array when servicing. In this box, we switched from the Enphase cable to THWN-2 wire run in electrical metallic tubing (EMT) conduit from the roof to the ground, and then transitioned to PVC conduit for the underground run to the service panel.

We've found that microinverter systems require a bit more time on the roof than standard PV systems, but can save a significant amount of time, space, and money by not mounting and wiring a DC disconnect, inverter, and AC disconnect on the house. A utility disconnect is sometimes still required by the utility or local jurisdiction.

Data Monitoring

Enphase microinverters have a data monitoring system to follow individual module performance. The inverters

The Envoy communications gateway receives data through the AC power lines and sends it to Enphase's Enlighten Web site.

The Enlighten site provides private Web pages for each subscriber that show specifics for individual PV modules as well as the whole system.

The Envoy communications gateway receives data through the AC power lines and sends it to Enphase's Enlighten Web site.

A graph of the array's performance on a partly cloudy day from the Enlighten Web site.

A Web site display quantifying system production.

A Web site display quantifying system production.

cumulative kWh generated, and total cumulative kWh generated. What's unique about Enphase's data monitoring is the ability to keep tabs on per-module production, both instantaneous and cumulative. The Web site's graphical layout depicting module placement adjusts the color of the modules to reflect instantaneous power output, ranging from black (0 W) to light blue (at full inverter output). Besides near real-time monitoring, we can review time-lapse graphic displays of the system's daily and weekly production and, if problems arise, easily pinpoint individual module or inverter malfunctions. The monitoring system automatically alerts us to system failure via e-mail. Setting up the monitoring function entailed making a layout map, marking the serial numbers of the inverters on the map, and then sending the map to Enphase.

This monitoring service costs an additional $350 for the Enphase Envoy Internet gateway (including one year of data monitoring) and $650 for five years of additional service. The Enlighten service also includes "rapid replacement" if there are inverter problems, along with financial reimbursement for lost production.

Daily System Production

Alternatively, a computer networked directly to the Envoy allows monitoring of the inverters, but without the sophisticated Enlighten Web site and automated e-mail notification. The system will operate normally without an Envoy connected, but there is no way to track individual inverters.

Maximizing Performance?

After working on PV systems for almost a decade, it amazes us how far the industry has come. Our system is performing well, and we'll be excited to see our first full year of performance in September—and whether or not we truly hit 100% of our energy goal. Comparing our actual system output to the National Renewable Energy Laboratory's PVWatts analysis, our system performed above the monthly projected average for October. So, at this time, meeting our goal seems very likely. And by April, we'll have our first round of chicks, and finally be on our way to eating our own solar-powered omelets.

Installation Tip: Wire Ties

When thinking about PV installations, which may be producing energy for decades, long-term durability should be your guide, down to the wire ties you choose. Stainless steel wire ties and module clips are highly recommended to secure module wires to the module frames and racks. All wires must be secured to prevent them from touching the roof surface. Wiring that comes in contact with the roof can be damaged due to mechanical abrasion by wind or ice, potentially creating fire and shock hazards. In this installation, the installers added a few layers of electrician's splicing tape under the stainless wire ties to prevent abrasion against the ties' abrupt edges.

Access

Kathy Swartz ([email protected]) oversees the RE education program at Solar Energy International (SEI). She is looking forward to using her chickens' eggs to bake goodies for the SEI staff.

Kris Sutton ([email protected]) has worked in the PV industry since 1999. He currently is a PV instructor at SEI (www.solarenergy. org) and runs a PV consulting business, Sutton Solar Services. He is a NABCEP-certified PV installer, a Certified SEI Affiliated Master PV Trainer through IREC/ISPQ, and on the Board of Directors of CoSEIA.

Many thanks to Matt Harris, Laura Bartels, Dave Clark, and the students in SEI's straw bale workshop for helping us erect and plaster our coop. We couldn't have done it without you!

System Components:

Direct Power & Water Corp. • www.directpower.com • PV mount Enphase Energy • www.enphaseenergy.com • Inverters SolarWorld • www.solarworld-usa.com • PV modules

Battery System

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

Get My Free Ebook


Post a comment