Design with PV in Mind

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

A great solar site has always been at the top of my homestead “want” list, so when my husband Shawn Schreiner and I stumbled on a piece of property for sale that had a wide-open solar window and a building pad that was ready to go, we pounced on it with our PV and passive solar dreams.

Both Shawn and I spent months scouring the Web for passive solar home plans that provided a small, efficient footprint and that would be relatively easy to build ourselves. We initially fell in love with a modern, simple design that would have suited our passive solar plans well, but scrapped it due to its north-facing roof.

So we went back to the drawing board—Shawn spent lots of time drawing in SketchUp, free modeling software that proved very handy, since we could observe how the various designs worked with solar gain. Besides having a passive solar home, we knew we wanted to use renewable fuels exclusively, so designing a large, uninterrupted south-facing roof space for a PV array and, potentially, solar hot water collectors, was essential.

The design we finally arrived at was a modified, “modernized” ranch—two long rectangles joined at a common wall. A south-facing roof measuring 60 feet by 20.6 feet would give us more than 1,200 square feet for PV modules and solar hot water collectors. With only one penetration for a stove pipe in the uppermost part of the roof, we had lots of room for renewable energy collection.

The building pad wasn’t facing true south and redoing it wasn’t an option—we needed to work with what was there. At a 218° azimuth, the house favors the south-southwest. We also deviated from the “default” roof pitch (equal to the location’s latitude: 42°) specified by PVWatts, and the “optimal” orientation specified for our location, which is 7:12 or 30°. Instead, we went with a 3:12 (14°) pitch for ease of building and aesthetics. How much would this compromise solar generation? Surprisingly, not very much—compared to an “optimal” orientation and tilt, our potential solar production would only take a 5% efficiency hit (see graph).

Load Goals

Our main goal was to use renewable energy systems for our homestead, which includes a small, separate office building and a 576-square-foot cabin, and make as much electricity as we use each year. Except for space heating, which would typically be served by our wood heater, all of our loads would be electric.

Although I hand-calculated the potential heating contributions from our passive-solar design, the figures were untested until the house was built and occupied. We sized a wood heater to provide backup heating, but building codes required an auxiliary system, so we opted for an in-floor hydronic system, fueled by an electric water heater. Our original plans called for using solar thermal collectors for both domestic hot water and hydronic heating. However, winters in southern Oregon are often overcast—when we’d need space heating the most. The sunny summers would’ve guaranteed plentiful production from a SHW system, but with a system also sized for space heating, we would have had to make sure our overheating protection was robust and design in some sort of diversion load.

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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