4 195W and 2 440W panels

After I set up my new ground mounted solar array recently (4 195W panels) I realized that I was only getting peak power of around 350W, so I decided to order a couple more 240 W panels from Amazon.  When they arrived (in a cardboard box weighing almost 80 pounds!) one of them was damaged beyond repair so I sent them back and then started looking online for solar dealers here in Maine.  I was surprised and delighted to find a company called Greentech Renewables that had just opened up a huge warehouse a few months ago.  They are about 15 minutes from my home soI stopped by and talked to their salesperson Eric who was very friendly.  I told him I was looking for a couple of high power solar panels around 450 W and he said he had quite a number of them.  So I asked him what the dollars per Watt was for these panels and he said that they were about $0.35.  Wow!  When I installed my first 20 panels 16 years ago the cost was nearly $4 per Watt, prices have really come down!  And the icing on the cake is that these panels were assembled in the USA by Canadian Solar, so no tariffs involved!  

So I paid for them and said I would come back in an hour or two with my trailer to pick them up.  I didn't realize how big these panels would be until I got there.  They are almost 4 x 6' and required two people to move them.  They put 2 on a shipping pallet and fork lifted them onto my trailer.  I asked if I could keep the pallet which is constructed from fresh clean looking 2X6 lumber and they said "Sure!".  So I cut them up with my chainsaw and I'm using them to heat my workshop:

 

I then went to my local metal supplier and purchased some angle aluminum so I could construct a hinged mount that I bolted right on to the back of the 2 new panels.  The metal strip on the bottom is secured to the ground with tent pegs so they can't blow over.  Of course I will need to shovel snow away from the front of them in the winter, but that's a small price to pay and I do have a snowblower.

  

Here's the front view of the full solar array with the newest panels on the right: 

You can also see the solar thermal solar collectors that are used to heat the hot water in my house and a 250 W solar panel that also works as a sunshade for the second floor bedroom.

Wiring for this array was complicated.  In order to optimize power there are two pairs on the left wired in series and the large ones on the right are wired in parallel and then they all combined in parallel to feed into the inverter.  Since the panels are different voltages, the power defaults to the lowest voltage which is a compromise, but so far it's working okay.

According to my calculations they should be producing peak power of 1000 W, but at this time of year with the solar angle being so low I'm getting a little less than that.  The screenshot below shows the energy produced for the last several days.  Day one was the original four panels panels, day two I added the first of two 440 W panels, and then on day three I connected the second 441 panel.  As you can see him offsetting my electric bill by about 3.6 kWh per day which will really add up.

The main reason reason for my adding these panels is that my annual cost of electricity is about $1000.  This is largely due to the two heat pumps and my electric vehicle and I'm slowly working my way towards a zero electric bill.  Next year I'm considering replacing the 29 panels on my workshop with newer much higher power panels.  This should get me to a net energy of zero.  

The other thing affecting my electric bill is that the utility company has been slowly ramping up a surcharge for those of us with solar.  Years ago there was no surcharge, then it went to $22 and now about $44 per month which adds up to $528 per year.  I understand the reasoning, because they have no revenue from me to support the infrastructure, but $44 seems egregious considering that my solar panels are enhancing power quality in my region and reducing the load on their transmission lines.  

Thanks to net energy billing I get full retail credit for every kilowatt hour that I export back into the grid.  Essentially, the utility is paying me for the power I put into their grid and when I reach the point of generating more than a use on an annual basis I will not benefit financially, but that's fine with me.  The way that net metering works is that every kilowatt hour I put back into the grid gives me a credit in kilowatt hours.  For five months or more in the summer I accumulate credits that I then use up into October and November.  At that point the trade-off of solar powered heat pumps doesn't work so well because we have so little sunlight here at 45° latitude and those heat pumps require a lot of energy to operate.  My bills in January and February were over $350 this year.  So my goal is to accumulate enough credit in the summer to carry me all the way through the winter.

I'm 70 years old now and working at reducing my operating costs by investing some money in solar equipment now so that I don't have to pay it out later to the utilities who are constantly raising their rates.  Given the very low cost of solar panels right now, this makes good financial sense as the return on investment is better than the stock market.  

 

 

Adding 4 solar panels on the ground

Solar arrays on my workshop

 My solar power system consists of 37 solar panels mounted on my workshop building and another 250 W panel mounted on my house facing south.  The original 30 panels were only rated at 175W when I installed them 16 years ago.  Then I added additional panels rated 2 tilting 245 W panels and 6 more 375 W.  The problem is in the last few years I have added heat pumps which draw an enormous amount of power during the winter months and my electric bill shoots up from zero (actually, $42 minimum connection fee charged by my utility for the "privilege" of being connected!) through the summer to over $300 in January and February.

With electric rates increasing dramatically I am looking at options.  In my home I'm shifting back to using a propane heater for my living room because the heat pump is unreasonably expensive to operate and in both buildings I'm using more firewood to offset the use of heat pumps and fossil fuel.

Last winter when my propane automatic standby generator failed I was without power for four days and this was unacceptable so I purchased two solar panels and a battery generator as documented in this recent post.  Then in the spring I decided to use the battery generator as a backup power supply for my 3D printers and stored the solar panels inside my workshop.  I realized this was pointless because I was literally losing money from energy these two panels were not generating.

 

So this October I decided to deploy those two 195W bifacial panels and add a couple more similar panels but they're not bifacial, however monocrystalline panels are much more efficient in low light.  Bifacial panels can generate up to 15% more power from the back especially when there is snow on the ground to reflect light onto the back. 

The panels are facing south and tilted up at a high angle to account for the low winter solar elevation angle. 

Panel specs

 

 

Here's a back view showing the bifacial panels on the right.  These are all made by a company called Eco-worthy who make very high quality and very affordable panels and I bought them on Amazon.

 

 

 

 

 I made my own mounting system using aluminum L extrusions that I riveted together.  This cost me roughly $40 per panel and should hold up well.  The whole mounting system folds up flat so I can take it down and store it should I need to.  Cearly, I will need to shovel snow away from the bottom of these panels in the winter.  But that's no big deal to me.

  

It's fall here in Maine and the time of year where we get very strong winds so I used tent pegs to secure the bottom of the mounting brackets firmly so they won't blow over.

 

 

 

All of my other solar panels are connected to the grid using micro-inverters made by Enphase.  (One micro-inverter for every solar panel).  However over the last 16 years 17 of the 32 original inverters have failed.  These were first generation technology and they have been replacing the failed units under warranty with seventh generation technology, but my warranty has now expired.  My trust in that system has eroded over time and I decided to use a string inverter.  String inverters take multiple solar panels connected in series and/or parallel and convert that to 120 V AC or 240 V AC.

Series-parallel connections

I connected the panels in this configuration as shown above which is the optimal one for best energy performance and the smallest gauge power cable required to feed the solar energy to the inverter.  The inverter wants to see a DC solar input from 22 V to 65 V.  By wiring two panels in series I get approximately 44 V and then by connecting them in parallel I optimize the power delivered to the inverter

I needed a couple of Y adapters in order to connect the two pairs of panels to the main cable that feeds into the inverter. Solar power cables use MC4 connectors which snap together and form a fully weatherproof connection.   These connect to red and black 10gauge wires that go across my yard for about 15 feet where they pass through the wall and down into my basement where the inverter is.

 

  

 
I purchased a weatherproof cable entry cover so I can prevent weather and critters from crawling in to my house.  These are typically used on campers and boats.

Down in the basement, I was able to install the (blue) inverter right next to my breaker panel.  I used more 10 gauge wire than I needed and tucked it up in the ceiling in case I need to move the solar panels.  Power comes out of the inverter at the bottom and that power cord plugs directly into an outlet to back-feed the outlet.

This is a G2 Series Grid Tied Inverter (model SUN-1000G2-M) that I purchased on eBay very affordably.  It is rated for 1000 W and my four solar panels can produce up to a peak of 800 W so I might add two additional panels in the future which shouldn't be a problem for this inverter.

The little blue display above the breaker panel monitors a single 245W solar panel mounted to the south wall of my house.

 

 

The inverter has a very helpful color display screen that shows power being generated and also a chart of Watts versus time. This was taken around 9:00am.

 

 

 

 

 

I connected this AC circuit to my Emporia energy monitor so I can see live data of the energy being generated in real time.

I did a detailed blog post about the Emporia system I installed back in 2021.  It is a very affordable system that I use to monitor 8 circuits in each of my 2 buildings.  I can track energy flowing in BOTH directions - meaning that solar power shows as "negative" energy in the charts and readings.