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home > solar power
Installing a grid intertied
solar electric power system


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Overview System
sizing
Financing Panel
Siting
Hardware Grounding Rail
Installation
Inverter
Installation
Panel
Installation
Real-time
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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.


Solar attic vent shading a solar panel
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,
New double electric meter for solar installation
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.

If we generate more than we use in any given month (likely to happen in the summer months) then that credit is "banked" against future months.

Note: the dual meter was later replaced with a single Smart Meter when the utility company upgraded to the new technology.  However solar net metering customers bills are still hand processed because they have not upgraded their billing software to allow for bi-directional energy flows.  A separate page is added to my bill showing energy credits.
December 15, 2009
Clearing snow off the panels with a snow rakeClearing snow off the panels with a snor rake 2

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. 
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.

 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.
 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!
25 panels on the roofEnphase Enlighten web page shwing new panels recently installed
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.
Smart Meters
April 20 2011 - got smart meters installed
A woman from Central Maine Power installed 2 new Smart Meters today.  We're the last house in the neighborhood to get them for some reason.  Later this year CMP will be rolling our the web interface so subscribers can monitor their usage.  I'm looking forward to that!

June 2012 - added 3 230 Watt panels
I added 3 Solar World (US made) panels with Enphase M190 inverters.  These panels are physically larger than the BP panels - so I had to extend the rails by 12" using IronRidge rail splice kits.  I am pleased that everything in my installation was US made.
As the Enphase Enlighten interface shows at left, the inverter is maxing out at about 197 Watts in full sun using the 230 Watt panel, this means that I'm getting much more power overall from these panels throughout the day.
March 2013 - added 2 245 W panels on south wall
 I added 2 Solar World panels using the newer Enphase M215 inverters.  While the inverter is nominally rated for at least 215 Watts, actual output power as shown on left maxes out at around 224/5 W quite early in the day as soon as the panels get full sun.   I tilted these panels at around 25 to keep the wind load low and optimize snow clearing in the winter.  I had to make my own brackets to mount these to the wall of my building since there is no standard racking equipment for angled mounting like this.  Later I learned that there was a poplar tree that was shading the right panel in the morning, and cut it down.
Sun tracking sensorTracking solar panelsSun tracker control and timerJune 14, 2013 - I engineered my own solar tracking system for the 2 new panels (see above).  A sensor mounted to one panel tracks the sun and sends control signals to a box inside which drives 2 linear actuators that can tilt the panels in or out from the wall.  Due to limitations of the actuator lengths, the panels only actively track the sun position from the fall solstice to the spring solstice,  providing optimal performance during the shortest days of the year.

June 8, 2014.  I noticed that my Enlighten web interface was showing that one of my panels was dropping out and producing only 1 or 2 watts. Since there was nothing visibly wrong with the panel, I contacted Enphase tech support to see if it was an issue with the M190 micronverter.  They attempted a fix by trying to download new firmware to that inverter and when that didn't work, they issued a replacement under their 15 year warranty.  It was relatively simple for my neighbor and I to go up on ladders, remove the panel and replace the inverter underneath, just a few bolts and plugs.
September 22, 2014.  I had been bothered by  the loose dangling wires hanging off of the inverter  and solar panels, and found a company called Nine Fasteners Inc. that makes these great little stainless steel clips designed specifically to secure wires to solar panels.  This really neatens up my installation!
October 22, 2015.  I found a nifty power meter that displays Volts, Watts, Amps and cumulative kWh from a surplus store and installed it next to the solar sub-panel.  Photos were taken in the late afternoon so it is not showing peak output which can be well over 4kW.
October 2016. A friend sold me a 245W Schuco panel for $100 and I installed it on the south facing wall of my house with an Enphase M250 microinverter.  More details on my blog. It has the advantage of serving as a shade for my bedroom windows in the summer. Power for the last 3 days
In June 2017, another Enphase microinverter failed and they sent me a replacement.  This one was relatively easy to access.  More deatils on my blog.