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Issue #208 November 2007
Let There Be Light
by Steve Ciarcia
When kids go back to school in the fall, the first thing teachers usually ask is, “What did you do with your summer?”
“Well, lady, I spent the summer learning everything you never wanted to know about concrete, wind loading, structural steel pipes, and disaster-recovery landscaping.” Needless to say, there wasn’t a dull moment.
The articles I’ve written to describe the installation of my PV system start next month. Let’s just say that as far as commercially installed PV systems go, doing pretty much anything more than slapping a few PV panels on the roof and wiring an inverter or two next to your service panel is an invitation for adventure. Government PV subsidies go up and the voyage begins.
I’ll introduce my installer in the article series, but I will say that I was lucky enough to partner with a team of people serious about getting the job done but not too proud to ask for help when they ran into obstacles. In the same vein, I think they appreciated that my objective in all this was to build and document a great PV system rather than take them to the cleaners over line-item responsibilities in a fixed-price contract. Surely they must have breathed sighs of relief when a test hole for the pole mounts hit a rock ledge and it wasn’t a show-stopper. Rather than chuckle and say, “I guess this job just got a whole lot more expensive for you guys,” I said: “Don’t get excited. I know just the people who can fix this.”
Of course, all of the adventure in installing a PV system comes from dealing with the problems and non-standard issues of actually generating your first watt. There are barely 200 residential PV installations in the whole state of Connecticut and most of those are roof-mounted arrays. After experiencing two types of PV installation methods, I can say that roof-installed panels are a snap and anything else is strictly experience-based knowledge. Certainly, my installer has a healthier appreciation of concrete and pole mounts than he had before dealing with me. I’m also sure the next time one of his salesmen says, “It just needs a few poles,” he’ll price the installation as if he were dynamiting it all out of solid rock. On the homeowner side, anyone installing pole mounts in the yard has to be prepared to remove a lot of trees and then landscape the whole place again after the cement trucks have destroyed everything. Yes, it was an adventure.
As I get a little more experience with the system and begin writing the third article, I’m confronted with yet another issue—remote monitoring. This also appears to be easier said than done.
Working with PV technology reminds me of the early days of computing. Back then, we thought nothing of building everything from scratch because all of us were engineers or trained professionals. If we needed a controller, we simply designed it. Today, ubiquitous and cost-effective computers mean we can purchase them like appliances and concentrate on the applications instead. The same lesson seems to apply to PV today. Most adopters think nothing of writing their own elaborate monitoring software or wiring probes and sensing elements to every panel. While I could conceivably do this too, I’ve done it enough times that I’m actually looking for excuses to avoid it.
My experience with PV installers thus far suggests that they know how to install net metering systems but haven’t a clue what you are talking about when you say TCP/IP monitoring. That’s why all of the PV-related articles you read contain so much homebrew hardware and software.
It’s interesting to note that the Xantrex Technology designed inverters used in my PV system have the potential for extensive interactive monitoring, but at this point, Xantrex offers only a simple “local” LCD to present solar data, and there seems to be only a rudimentary user-supplied PC display program for the inverter’s RS-232 data port. A pair of NETDIO serial-to-Ethernet modules configured for serial tunneling facilitated using the PC software on a single remote desktop, but it did nothing for web-based monitoring. That’s when I started mumbling to myself.
Until I can really solve this problem the right way (and stop running up and down the stairs), I’ll use the ultimate kludge. An hour ago, I went down to the garage where the inverters are mounted and screwed a power line Ethernet extender, a video camera, a video web server, and a 3-W LED light bulb to the wall over the Xantrex LCD. Yes, I know it’s a total kludge (lose my name when you describe this technique to others), but at least I can call up a web page from anywhere and see how the system is functioning. Of course, if I were really insane, the next Rube Goldberg would be to attach a rubber mallet to a big web-controlled solenoid that whacks the front of the inverter to activate its vibration-sensitive display sequencing. I may wait on that one. ;-)
Fortunately, common sense will prevail. Xantrex tells me that they will have a web-monitoring system available soon. I’m also ordering some current transformers so that I can get a better real-time view of what the house is actually consuming and not just what I’m generating. Connecting everything will be an interesting project. I’ll keep you informed. Of course, until then, let there be light.
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