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September 15, 2009
Thanks to the Enlighten feature that
allows you to play back the solar panel energy statistics graphically
over time I was able to clearly see that the solar panel on my solar
attic vent was causing a shading issue for over an hour in the late
morning.
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The solution was obvious, I just had to climb up and lower the panel so
that the shading issue was reduced. Now the panel on the vent will be
oriented toward the sun in the late afternoon rather than mid day, but
that is when the heat is highest in the attic, |
 
September 15, 2009
A Central Maine Power crew came out to replace the single meter with a
double unit that allows for 2 readings, energy delivered by them and
energy exported from my solar array to the grid. Russell from CMP shows how the new
meter will install (left) and points to the meter (right) that shows the
solar power being generated. Only one meter spins at a time indicating
which way the current is flowing at the time. As we watched one meter
would stop and the other would start as loads changed in the house.
This was before full sun was shining on the solar array, so the panels
were barely meeting our energy needs at the time. In full sun the
bottom meter spins quite quickly as we export energy to the grid. After
the sun goes down we import it back.
The meter is installed as part of the Net Metering Contract that I
signed with CMP, the company that delivers our electricity. There are
several reasons for this contract. First, the double meter gives CMP
statistics on how much power I am putting into the grid. They need this
data so they can report it to state and federal agencies as part of the
renewable energy portfolio for the state.
Secondly, this contract stipulates that I get full retail credit for
every kWh that I export. It is interesting to note that CMP's computers
do not have the capacity for crediting small residential producers like
me, so the billing has to be hand processed each month. Keep in mind
that due to deregulation, CMP does not generate power they simply
transmit and distribute it and handle billing for the energy provider.
In Maine there is the so-called "standard offer" which has a state
mandated mix of 40% renewable energy. This is currently billed at 15
cents, while the 100% green power that we have elected to purchase from
Maine Renewable Energy
costs us 18 cents. So we get a full 18 cent credit per kWh for our
power.
If we generate more than we use in any given month (likely to happen in
June) then that credit is "banked" against future months.
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December 15, 2009
 
Another
learning opportunity came with the first 8 inch snow storm. I had to
clear the snow off the panels, so I went to the hardware store and
bought a snow rake for about $45.00. This tool has a plastic "shovel"
at the end of an extendable pole that assembles in 3 6 foot long
sections as needed. The panels are so far up that I added a broom
handle and still could not quite reach the top. I learned to be
meticulous, because any snow left on the panels will reduce the
performance as became very evident on the Enlighten web statistics. |
May 2010 - energy monitors
Earlier in the spring I installed a
TED5000 energy monitor for about $200 so I could see our utility
power use and compare it to our solar production. The TED system
installs in the main breaker box and sends data to a small web server
box via the power lines. A network cable connects the unit my LAN
network so that I can see a beautiful web dashboard that gives a real time
view of our electric power usage and the power we generate from solar.
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TED Current Transformers
clamped around utility feed |
TED Current Transformers clamped around
solar power
feed connect to MTUs |
TED MTU units for utility and solar power
send power via
AC wiring to Gateway |
TED Gateway
(web server) |
This is a terrific tool for keeping an eye on electrical consumption.
There are numerous graph functions to explore historical data by the
second, minute, hour, day and month.
For instance one way to measure the total of all the phantom loads is to
look at the lowest points in the early hours of the morning when we're
asleep. While the fridge cycles on and off on a 20 minute cycle, it's
during the off periods that I can see the minimum power reading. By
hovering my mouse over the graph a pop-up window show the exact time and
power for that moment.
Main dashboard showing low energy net usage.
You can select solar or utility page views |
24 hour graph
blue=utility, yellow=solar power, green=net power |
Hourly data for 48 hours showing a partly sunny
day and a full sun day. |
Graph showing first 13 days of April,
note 2 days with net export of power. |
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August 2010 - Adding
2 panels
 Thanks to the modularity of the Enphase system, I was able to add 2
more panels to my array today. Total installation time was
less than an hour. I climbed up and removed the panel clips on
the left edge of the 2 panels that would be adjacent to the new ones
first. Then I slid new bolts into the mounting rail to account
for the inverters and mid panel mounting bolts. I turned off
the array, bolted down the inverters and plugged them in, then with
my neighbor's help hoisted up the panels, plugged them in and bolted
them down, and powered the array back up.
The next step was to call Enphase so they could tell the Envoy data
communications module to scan for the new modules. 10 minutes
later I accessed the Site Builder tool in my Enphase web portal
account and placed the new panels in the array and assigned the
module serial numbers to them - simple drag and drop stuff!
Shown at left are the 2 new modules before the statistics have caught
up with them.
One thing I noticed about the newer Enphase M190 inverters is that
the female AC connector is now on a cable rather than mounted in the
box as they were in the ones I first installed. This
definitely adds flexibility in the installation! The added
length helps to account for uneven rail spacing and larger solar
modules.
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September 2010 - Solar
shading effect of panels on the roof
The warm sunny weather recently caused me to consider whether there
is a benefit to having solar panels on the roof that reduce the surface
temperature on the shaded shingles. So I set up my
Hobo
Datalogger to find out. As you can see from the plot below the roof
stays up to 10 degrees F colder than the exposed roof surface.
Cool! Literally! So that is why I have used my small room
air conditioner a bit less this year. I guess the panels are not
just generating power they are saving it too!
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June 2011 - Added
2 more panels
Added 2 more BPSX175 panels. I got a good price on these as
they had been damaged when they blew off an installation and the
frames were bent. I straightened them out and siliconed the
front seams to prevent water and ice from seeping in around the
weakened seal. |
 
July 2011 - added 1 panel
Added a new 180 Watt BP4180 panel. BP no longer makes the
polycrystalline BPSX175 panel and now make a monocrystalline panel
with a white background that looks quite different. This
exemplifies the advantage of the Enphase micro inverters - you can
mix different panels in the system with no concerns. |
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