Any PV (solar panel) owners out there?

[rkawakami]

In September of last year the wife said it was time to think about putting a new roof on the house. I suggested that as long as we were going to do that, why not look into installing a solar array. She had the same thought so I started looking into what was involved. We eventually settled on a 20 panel, 3.7KW DC (3.1KW AC) system. Out of pocket cost is $14K when all of the rebates and tax credits are applied. Return on investment (ROI) was calculated to be 13 years. System went live on December 24th. The first month's electricity bill was $13. Last January it was $80.

The system is designed with "micro-inverters". No, not the kind that drives LCD backlights . These inverters (Enphase D380) are positioned below the panels and converts the ~40VDC into 240VAC. One inverter is connected to two solar panels (ET-M572185B). The entire array is then piped down via a single cable into the electrical service panel on a separate breaker. When PG&E finally got around to inspecting the system and changing out the standard "smart meter" for one which does time-of-use (Net Metering), the breaker was flipped on and the panels connected to the power grid.

The inverters have been designed with Ethernet capability (a la Powerline AV or HomePlug). There's an Envoy Gateway interface box plugged into an AC outlet in my garage, which is also connected to my home network via a wireless Ethernet bridge. That allows the gateway to gather power data from the inverters and send it over the internet to the Enlighten servers. The data is then condensed into reports that shows the amount of power currently being generated, along with historical data. To view my system, click on the following link:

http://www.kawakami-ca.com/solar/

The page will display a note that Flash is required to view the information and then it will re-direct to the EnphaseEnergy web site.

[killer]

That's fascinating stuff. I imagine your ROI could be much sooner than 13 years given the rapid increase in energy costs. Did you have to strengthen your roof before putting on the panels?

I wish we could have solar power here but we live in a thatched cottage in a conservation area and National Park. The only way we could do it would be to have the panels in the garden ... which might look a rather unsightly mess.

[poshgeordie]

Very Interesting Ray - It gives the rest of us the encouragement to carry out similar projects ourselves. I'm really annoyed that when we had the roof (slate) done 5 or 6 years ago that we didn't look into doing a similar thing.

[rkawakami]

No extra strengthening was needed for the roof in order to support the solar panels. There is no absolute requirement that the roof and solar be done at the same time but it helps if both companies are involved so that what one company does (or doesn't do) won't affect the other. The solar company knew the roofers we selected and everything went smoothly. The ROI assumed a 5.5% annual increase in utility costs which I thought was a little high but with gasoline prices now topping out at just over $4/gal here in the South Bay, that might have been a conservative estimate . The only real hiccups with this project were with the local power company (PG&E) and the configuration of the Envoy monitoring service. PG&E took their time coming out to inspect and approve the installation. The panels were ready to go for over four weeks before they were connected to the grid.

Once that happened I was able to get the data from the Envoy gateway directly from my home network. There's a web server built into the box that allows you to see the status of each microinverter and solar panel from any browser. It was also reporting that the internet connection to the Enlighten servers was good. However, Enlighten kept saying that they couldn't see my system. After a couple of go-arounds with Enlighten and Real Goods Solar everything was sorted out. My guess was that either Real Goods did not send Enlighten the physical map of the system, or Enlighten lost it the first time, or there was some miscommunication of account numbers. What you see on the Enphase web site for my installation accurately reflects the arrangement of each solar panel on my roof. There's three rows of panels, consisting of 6, 6 and 8. They are all facing south; the 180° in the upper right corner of the map. Visitors to the web site can see general information about the power but when I log into my account, I can click on each panel and get individual information just about that panel. This allows me to monitor the efficiency over time. This service was built into the cost of the installation for the first five years. After that, it's $180 for another five years of monitoring. I think it's a small cost for the peace of mind that it can deliver.

The monitoring service is one of the reasons why I opted for using microinverters instead of a single (large) inverter at the power panel. Additionally, if our electrical needs increase in the future, or if another family moving into the house needs more power, it's much easier to add on solar panels with this system. It also provides for more uniform power generation in the event one or more panels is shaded or develops a defect. With a traditional single inverter system, if one panel's output drops to 50%, the entire system goes down to 50%. It's the effect of the "weakest link". Using microinverters, one for every two solar panels in my case, when one panel gets shaded it only affects that microinverter's contribution to the overall system. Since there are 10 microinverters on the roof, that's a 10% power drop at the most.

The few bad things about microinverters is that it introduces more points of failure in the system and system costs are more than a single inverter. Although they are warrantied for 15 years and have a supposed MTBF of 100+ years ( ), having more "pieces" in a system always means more chances of having problems or needing replacement later on.

[rkawakami]

When I set up my Enphase solar monitoring system, I allowed it to be placed on a public list that can be accessed by anyone. Other people have done the same so you can see how much power can be generated by various installations. This list is here:

http://enlighten.enphaseenergy.com/all_public_systems

By default, the list seems to be arranged in more or less chronological order of when the system was installed. Locations are given, along with the number of PV panels at the site. You can click on the column headings (System name, Location, # of PV modules, Lifetime Energy) to sort the list. Sorting by Location is arranged by State, but it's not further sorted by city. If you are thinking about installing solar panels and want to get an idea of how much energy can be produced, use your browser's Find function to search for your town (or one near you) and then click on the listing to see the details about that system. Keep in mind that the number of panels, and how they are arranged, have a great influence on the amount of electricity that can be produced.

[rkawakami]

Just a note about my solar installation and a recent problem related to Thinkpads.

In the last few weeks, my Envoy monitoring system has only been registering 3 to 6 microinverters (out of 20). I get email notices whenever the monitor detects problems with the system. As I've mentioned earlier, the microinverters communicate over the power line with the Envoy. A couple of years ago Real Goods came out and replaced all 10 of the D380 microinverters after several of them had failed, with 20 D190 units. So much for the 100 year MTBF. I also re-located the Envoy from the garage to inside the house. Everything was working fine up until about 3 weeks ago

I initially thought that the D190 models were having a similar problem with reliability, although a check at the electric meter seemed to indicate that power was still being uploaded to the grid. In other words, AC power was still being generated by the solar panels but the communication between the Envoy and microinverters was broken. I tried re-booting the Envoy and forcing it to do a re-scan (to identify all working microinverters) but that didn't help. I called Real Goods last Thursday and left a message for them to contact me to arrange for somebody to come by and take a look at the system. They left a message on the home phone on Friday but I didn't get it until late in the evening. This past weekend I spent a little more time on the issue and believe I've identified the problem....

It's the 135W AC adapter I'm using with a W520.

I've been using an X60 (90W supply) for some time at the dining room table. I recently (i.e, three weeks ago) started using a W520. Both 90W and 135W AC adapters were plugged into the same wall outlet. The Envoy is plugged into the same circuit in the laundry room; opposite side of the wall where the Thinkpad adapters are. Unplugging the 135W supply and performing a re-scan on the Envoy and all 20 microinverters were identified. Signal strength reported by the Envoy is very poor however. Plugging in the 135W adapter must be sending enough noise on the AC power line which is swamping the signals from the microinverters. I tried another 135W AC adapter but it too caused the Envoy to only detect 3 microinverters. My plan now is to possibly move the Envoy onto another power circuit, separate from the one in the dining room, or to use a filtered power strip with the Thinkpad adapters and see if that reduces the noise on the AC line.

[shawross]

Maybe check your earthing.

[RealBlackStuff]

Another option: get an isolation transformer, preferably a toroidal one.
http://www.toruspower.com/plain-white-p ... ansformer/
Those are also available with MD-approved specs for even less interference,
such as this: http://www.ebay.com/itm/391016406062