Design with PV in Mind: Page 2 of 2

Intermediate

Inside this Article

Installed PV array
Shawn Schreiner with the installed PV array.
View of the home and site
A good view of the home and site, showing its unobstructed southern exposure and a nearly complete PV array.
Lumos Solar modules
The beautifully reflective Lumos Solar modules at sunset. At bottom right is the proprietary spacing tool that helps ensure proper module layout.
S-5! clamps
S-5! clamps were used to attach the rails to the standing-seam metal roof.
The DC disconnect (left) and the combiner
The DC disconnect (left) and the combiner, with its six fuses (right), are mounted on the north roof’s fascia.
The power wall
The power wall on the north side of the house with (L to R): AC disconnect, production meter, inverter, and household mains panel.
Installed PV array
View of the home and site
Lumos Solar modules
S-5! clamps
The DC disconnect (left) and the combiner
The power wall

Given the falling price of PV modules and Shawn’s ability to install the system himself (he’s a solar installer with True South Solar, based in Ashland, Oregon), we felt it made more sense to design a solar-electric system to meet our homestead loads. Like an SHW system, a grid-tied PV system would produce energy year-round and have its highs and lows. However, the big difference would be that we could use all of the energy it produced. How? With a net-metering agreement with the utility that would credit any surplus energy our system generated, “banking” it for our future use. In summer, when we could hang our clothes on the clothesline and use our solar oven more, our system would almost always be generating more electricity than our homestead uses, and we could draw upon this surplus in the cloudier winter months.

Design Marries Substance & Style

We lived in the house for almost a full year before installing the PV system, so we were able to use our past electricity bills to help arrive at a system size. In many cases, we had duplicate loads, since the workshop, which includes an electric range, space heater, and water heaters, was often occupied. The spa tub (admittedly, an energy hog) also ran during this assessment time, as did the radiant floor system. (The spa tub is no longer in use, and we use the radiant floor system only as a backup to the wood heater, which is a backup to the passive solar.) With the extra loads, that year, our monthly consumption for the homestead averaged about 1,350 kWh—or about 45 kWh a day. Ouch! With an average of 4.7 daily sun-hours and a 77% system efficiency, we’d need a 13.4 kW system to zero-out the homestead!

However, we knew we could—and would—do better in decreasing our electricity use. Some of that “extra” electricity use during the year had been running some big tools during the home’s construction, such as compressors, saws, drills, heaters, dehumidifiers, and the like. Some of that usage was due to the inefficient spa’s draw, and some due to testing (and initially “charging”) the radiant floor system. We guesstimated that a system that was under 10 kW would do the trick—and then some.

The PV system’s design would have been straightforward, except for one thing—my knowledge of a sleek, sexy new PV module that was just being introduced. I had seen Lumos Solar’s glossy frameless modules at a solar conference earlier that year and I was smitten. The marriage of form and function—“art” that made electricity!—was just too tempting for me. I also thought it would be a great opportunity for my solar-installer husband to showcase a product that was a little different from other modules on the market. The company he works for could potentially use our home to show the frameless module option to clients.

The modules didn’t have the power density of some other brands, but we had a big roof and could fit more modules to meet our design goals. However, there was a learning curve involved in the installation process (see “Working with Frameless Modules” sidebar).

System Performance

The PV system officially went online on December 13, 2011. As of January 22, 2013 (406 days later), the Fronius inverter showed 14,177 kWh production—a daily average of 35 kWh. PVWatts uses a system efficiency of 77% as the default, when our real-world efficiency is better than that. If you plug in the derate values of the actual components we used (0.97 for power tolerance for Lumos LSXs, 0.955 for the Fronius inverter’s efficiency) and assume 100% availability, the DC-to-AC derate value goes to 83%, and 34.7 kWh per day predicted—very close to our daily average.

Since June, our monthly electricity bills have been $10.12—the “basic charge” for having a utility meter. As of December 13, 2013, we had used most of our accumulated surplus electricity, but several exceptionally sunny, cold days in January were replenishing our bank of energy again.

Access

Home Power managing editor Claire Anderson is keeping a watchful eye on her homestead’s electricity use and PV system’s production with a TED 5000 energy monitor.

Comments (9)

Claire Anderson's picture

Hi William ~ I'm happy to share the floor plans. What specific information do you have regarding the home's mechanical systems? Cheers, Claire

William Campbell 3's picture

I'm planning on building a Green home in the next 6-10 months, with two master suites split plan on a ranch with wheelchair accessability throughout including the kitchen and one of the suite baths. I want to prebuild as much accesability as possible for the bathing facilities in one master suite. So, the design of the floor heating and all other Solar control systems need to be reachable and easy to operate. No step is mandatory in and out of home. There is a lot to envision in the layout, so I've read and looked at lots of pics. Any info to build an almost off the grid home easy to control and navigate would be helpful. We have been very dissappointed in what some home builders consider handicapped accessable. A ramp in and out of the home, or no step entry is just the beginning of what is required. Thanks for any input or advice. I see no reason to give up on my long time plan for a almost of the grid home, just because I am caring for my Mother. She still has her mind but is somewhat physically limited now, and is expected to become more so in the future. Thanks Claire

Justine Sanchez's picture

The modules used in this system are from Lumos you can check out their website for more info: http://www.lumossolar.com

Best,
Justine
Home Power Magazine

mctrivia's picture

I can't seem to find these modules for sale anywhere. They are beautiful and was wondering how much they are per watt

Claire Anderson's picture

If you contact Lumos Solar, they can put you in touch with one of their authorized installers. 877-301-3582 is their toll-free number or 303-407-7994 is their office number in Colorado.

Craig Merrow_3's picture

That would be great! BTW, I was looking at electric water heaters over the weekend, and came across this: http://www.geappliances.com/heat-pu...
Still investigating it, but if it is as efficient as they claim, it would be perfectly suited for DHW and hydronic heated floors with PV's to offset the power useage. The Energy Guide estimates yearly operating costs at $195, based on 1830kWh of use. Not sure if I could get by on one for both demands or run two seperate ones, but between the cost savings and rebates, it could pay for itself in two or three years.

Claire Anderson's picture

Hi Craig ~ Glad you like it! I'm happy to email you our floor plan and elevations if you'd like. It's a fairly simple, straightforward design.

William Campbell 3's picture

I'm into KISS Claire, could I also get info on your floor plan and systems. I'm looking to build for a completion date in 6 months or less and am gathering as much info as possible to be comfortable, GREEN and "almost" completely off the grid. Thanks in advance.

Craig Merrow_3's picture

Interesting house! I'd like to see how the house is laid out and how it is constructed, as it is similar to what I have in mind to build here in Maine. Been on the fence about SHW or going extra PV's for hot water/hydronic heating as you have; my loads are substantially less, so I could use fewer modules and still be net/positive zero.

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