Tuesday, October 27, 2009

Our New PV System

I've been trying to get the new PV system in the last week or so, and as a result I'm falling behind on getting new entries up on the website.  Thought I would just give a short progress report on the PV system. 

I do plan to do a new section with a lot of detail on the whole PV system process with lots of detail on design, site survey, mount construction, wiring, installation, ...   probably a lot detail more than you ever wanted to see :)

After much looking at a lot of options, I chose the type of system that uses one Enphase micro inverter for each PV panel.   In this kind of system, each PV panel gets its own grid-tie inverter, which is mounted right at the PV panel.  Each inverter takes one PV panel's DC output and converts it to 240 VAC that is grid compatible.  Each inverter plugs into the next inverter in the array, and you end up with all the power from up to 15 PV panels being available as 240VAC at the last panel/inverter in the string of panels.  My system has 10 PV panels at 215 watts each for a nominal total of 2150 watts. 

I bought the system as a "kit" from Wholesale Solar -- this one...

The more common approach on grid-tie systems is to wire several PV panels in series so that the they produce a high DC voltage.  This string of PV panels are then wired to an single inverter which takes the several hundred volts from the string of PV panels and converts to grid compatible 240 VAC. 

There are pros and cons to each approach, but (I think) both are pretty simple systems that can be DIY projects as long as you are VERY careful to mind the safety precautions. 

In my system, the PV panels are mounted on the ground and are located about 100 ft from the house out in the weeds.  The wires are run underground from the PV panels to the area where power comes into the house, and the grid-tie is made there.

I rented a power trencher to dig the trench for the wires.  In our hard soil, this saved a lot of time and effort.

After some debate with myself, I settled on a rather robust mounting system made from 4X4 treated lumber.  I wanted something that would withstand the high winds we get occasionally, and that would last 30 years.  Treated lumber may not be the best choice for long life in some areas, but around here, if properly installed it lasts a very long time.

This shows the framework that the PV panels will be mounted on. 
Anchored in about in 3200 lbs of concrete!

Running the wire (in conduit) from the house to PV array.

I clamped the PV support rails and a PV panel in place just to get the spacings
right and to plan where the inverters would go (they mount to the same rails as the PV panels)

This is where I am -- just waiting for a day or two of descent weather to finish it up.


Wednesday, October 7, 2009

The Solar Decathlon

The Solar Decathlon is here!  Its going to be from October 9 to October 18.

This is a terrific event.  Here is a good description shamelessly copied from the DOE Newsletter:

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20 Solar Homes Take Shape on the National Mall for the Solar Decathlon

Aerial photo of many small houses under construction along a walkway that runs down the center of the National Mall, with the Washington Monument in the far background. In the foreground, a metal lattice gate frames the walkway and carries a sign that says 'Solar Decathlon.' Solar panels are visible on two nearby houses.

Construction is underway at the Solar Decathlon, which opens to the public on October 9. Enlarge this photo.
Credit: Richard King, DOE Solar Decathlon

The assembly of 20 solar homes on the
National Mall in Washington, D.C., is rapidly approaching completion,
as the 2009 Solar Decathlon prepares to open, free to the public, on
October 9th. The Solar Decathlon is an international event in which DOE
challenges university teams to design and build homes that run entirely
on solar energy. The teams ship their partially constructed homes to
the National Mall, assemble them, and then compete in ten contests.
This year, the 20 teams came from universities in Arizona, California,
Illinois, Iowa, Kentucky, Louisiana, Massachusetts, Minnesota,
Missouri, New York, Ohio, Pennsylvania, Texas, Virginia, and Wisconsin,
as well as Puerto Rico, Canada, Germany, and Spain. Trucks rolled onto
the National Mall just after midnight on the morning of October 1, and
since then, the teams have been steadily working to assemble their
solar homes. See the DOE press release and the
Solar Decathon Web site.

This is the fourth running of the Solar Decathlon, and for the first
time, the competition features a stand-alone electrical microgrid to
which each team will have to connect their home. Starting on October 8,
each home will be monitored for its performance in five areas relating
to performance and livability: comfort (maintaining comfortable
temperature and humidity in the home), hot water (producing a
sufficient quantity at a high enough temperature), appliances (such as
keeping refrigerated items at the right temperature), home
entertainment (running a television, computer, lights, and other
devices), and net metering. For the net metering competition, homes
must use zero net energy over the course of a week, and teams receive a
bonus for producing more energy than their home consumes. Other
contests rate the teams for their communications with the public and
for the architecture, engineering, and market viability of their homes.
The overall winner will be announced on October 16. See the Solar
Decathlon's Contests and Scoring page.

DOE is the primary sponsor of the 2009 Solar Decathlon, which is
also sponsored and managed by DOE's National Renewable Energy
Laboratory. Homes will open to the public beginning on October 9, and
will be open for tours weekdays from 11 a.m. to 3 p.m., and from 10
a.m. to 5 p.m. on weekends, through October 18 (with the exception of
October 14). Not able to come to D.C.? You can keep up with the Solar
Decathlon online through daily journals posted by DOE's Richard King, the Solar Decathlon director; photos of the day from the event; YouTube videos; time-lapse photos from three cameras at the event; blogs
from the teams; the Solar Decathlon Facebook page (become a fan!); and even a Twitter feed!


Monday, October 5, 2009

First Year Performance for $1K Solar Water Heating System

The first full year of performance for the $1K Solar Water Heating system is in the books.  The graph below shows Solar Fraction by month.

All the details, and detailed plots that show collector, tank top, tank bottom, and ambient temperature are here...

So, this is the end of the promised one year of logging -- I now get my loggers back for other projects!

I've also a added a page that describes how I estimate Solar Fraction,
and considers some sources of error, and describes how my method
differs from the SRCC ratings of solar water heating systems.


Saturday, October 3, 2009

Scott's 24 by 8 foot Space Heating PEX Collector

This is a really interesting solar space heating collector design.  It is built as a single unit that is 24 ft wide by 8 ft high.  Compared to building a bunch of separate collectors, the single unit construction saves some time, effort, and materials, and looks very nice.


The absorber is an extra wide variation on the PEX/aluminum absorber.

For more on the collector, including a link to Scott's site with all the construction details, and a few of my thoughts on the collector...

This is a good example of the kind of freedom to try new things and fit your design to your situation that building your own system gives.

Scott is a founder of the Yahoo SimplySolar group -- a good place to discuss your new solar ideas.


Thursday, October 1, 2009

Some New Content Items for Build-It-Solar

Three New Content Items

1. Lee's Solar Mower

Some time back, Lee sent in the details for his solar lawn mower.  The article basically tells you how to convert a gasoline powered mower to a battery powered electric mower with solar charging.
One issue with doing this is finding a good electric motor.  The one that Lee originally used is no longer available.  So, Lee has found a new source of motors that should work well and are cheap and easy to find....


2. Performance Update for Marc's  Compost Furnace
Last week, Marc provided a description of his system to provide space heating via heat extracted from a compost pile.
Marc has provided some performance data and other observations based on the first full season of operation...

3. A Home Built Grid-Tied PV System with Battery Backup
detailed account of the design and installation of a grid-tied PV system
with battery backup.

A home built ground mount system from treated lumber
is also described.


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