Last year when I added two additional solar panels to the south wall of my workshop I could not figure out how to secure the loose and dangling loops of wire that come off the solar panel and connect to the Enphase micro inverter secured to the underside of these panels. I tried duct tape but it failed very quickly, and the only other option would have been to drill some holes in the frames of the panels and then secure the wires with cable ties. The problem with cable ties is that they will degrade and fail eventually, so I just left the wires hanging there and it has bugged me ever since. These dangling wires are particularly at risk since the panels move in and out on actuators that I installed so that the panels track the sun angle seasonally. This movement, along with strong wind would continuously flex those wires causing a potential failure at some point.
So I called up Vin Marino, product manager at Nine Fasteners to see if he could send me a couple of samples so that I could tidy up my wire mess and he was happy to send me several clips. Here is the before and after view of my tidied up wiring scheme:
When I see climate change denial trolls posting absurd responses claiming that renewable energy is ineffective, I realize that they do not have a clue about the realities of investing in renewable energy systems. From my perspective renewable energy is not only good business sense it is a win/win situation for myself personally and the world at large since I have dramatically reduced carbon footprint of my lifestyle.
A few weeks ago I was using the Enlighten web interface for my solar array and noticed immediately that one of the solar panels was dropping out at different times of the day and producing only 1 or 2 Watts. By clicking the play button in the center of the graphic, I can replay the energy produced by each panel throughout the day - or over several days if I wish. This is a very helpful user interface and is one of the best features of using micro-inverters because you can isolate and identify specific issues very readily.
I immediately emailed Enphase tech support and they responded by saying that they would try uploading new software to the microinverter behind that panel. A week later the panel dropped out completely and was no longer producing any power so I called tech support and talked to very helpful person who explained that they had tried the upload and it had not worked so they had already issued a replacement microinverter.
Enphase inverters have a 15 year warranty which is quite similar to the standard 20-25 year warranty on all solar panels. Once the replacement inverter arrived, it was a relatively simple matter to shut down the array and go up on a couple of ladders with my neighbor and remove the solar panel to access the inverter. At which point it is largely plug and play to replace and then bolt down the new inverter and solar panel. And now I am back to normal again:
The value of my solar power system is enhanced by excellent warranties and customer service.
A month or so ago I noticed that one of the pine trees on our property line had died, so I asked my neighbor if he would like to help me take it down on the condition that we did not use any fossil fuel.
I let Charlie cut down the first major trunk using the corded saw and despite the fact that the blade was a little dull, he made relatively quick work of bringing it down while I stood by with my cordless saw to “debone” the branches after it came down.
Here in Maine, we are approximately at the 45th parallel which means that we have significant seasonal changes in solar elevation from winter to summer. At the spring and fall equinoxes the sun is approximately 45° elevation at noon. This means that the available solar energy in the winter is approximately 25% of the maximum solar energy available in the summer. This is best explained graphically by this chart taken from my TED energy monitor:
The blue bars show the kilowatt hours that we import from our electric utility. The yellow bars show the amount of solar energy actually produced by our 5.7 kW solar array, and the green bars show the net amount of energy that we pay for. Clearly our electric bills drop to near zero in the summer, and since we have an electric vehicle we need to charge your round our bills peak at around $100 per month in the winter. At this time of year it is always nice to see our solar energy increasing, and our electric bills dropping.
Over the last 13 years since we purchased our home in Maine I have been working at reducing our energy footprint as part of my commitment to live as sustainably as practical. My strategy has been to reduce usage by improving things like building insulation and consumption in general. But also I have added renewable energy sources such as a solar heating system for the hot water in our home, and the solar electric system I installed. I decided to review my progress so far since I have extensive data on all of our energy sources and costs. This information is derived mostly from our utility bills.
We use propane to heat the house and also for cooking, clothes drying, and water heating. Below is a chart showing our annualized cost for propane per heating season. Some of the variations such as the spike in 2010/11 are due to fluctuations in the cost of propane, but the trend is largely due to my efforts since the cost per gallon has been increasing.
Not factored into our relatively low propane costs is the fact that we burn approximately 2 cords of firewood per year at a cost
ranging from $300-$500 per year. Last year we spent $425 for firewood which brings our recent total heating cost to a little over $1400 which is less than half the state average for home heating costs.
As you can see our propane consumption dropped about 50% over the years from almost 800 to a little over 400 gallons last season. Part of the reason for our initial lower cost was that our home (constructed in 2001) was reasonably well-built, insulated and relatively tight compared to an average home. Some of the things responsible for this reduction are:
* Improved basement insulation added to exterior concrete walls.
* Tightening up the building envelope by foam insulating air gaps around window and door framing.
* Adding interior storm window panels and closing honeycomb insulating shades in the cold winter nights.
* Weatherstripping around exterior doors and improving attic insulation.
Thanks to the solar power system I installed, our average electric bill would be around $10 if we did not have the Chevy Volt electric vehicle which adds approximately $45 per month to our monthly bill.
One can look at all of the investments I have made in reducing our energy footprint in terms of return on investment. In actual dollars most of these investments have already paid for themselves, such as the solar hot water heating system which according to my calculations paid for itself in approximately 4.5 years:
We had a significant snowstorm last night that dumped over 9 inches on us. The moment the snow stopped, I go out with my extended snow rake and cleared the snow off my panels so that I can get some power.
I have to wear heavy clothing and full yellow slickers because the snow comes right down at me and it is quite heavy! The wind chill at 11 AM this morning was around 0°F and after half an hour of heavy exertion I was ready for a break so I could chip the snotcicles out of my mustache and beard!
Below is a sequence of snapshots taken from the Enphase web monitoring system for my array every five minutes that clearly shows the panels being cleared and some small amount of power being produced.
By the end of the day, I expect to have produced over 1 kWh - even on this heavily overcast day. Since tomorrow promises to be a clear, sunny day I want to have my array cleared and ready to generate maximum power first thing in the morning. Given how much I have invested in my solar array, I try to get every Watt I can out of it.
When I installed our solar array, I signed a Net Metering Contract with our electric utility Central Main Power. Like most Net Metering arrangements, the utility credits me for every kilowatt hour that I export to the grid. This means that if I am paying the utility $.13 per kilowatt hour for the electricity that they deliver, if my solar array is producing more power than we use and we are exporting energy I am getting a credit of $.13/kWh. At the end of the month credits are applied to my bill, and if I exported more than we imported a credit is applied to subsequent bills until the credit is used up. If we were to have a credit after 12 consecutive months, then it would be cleared. So there is no incentive at this point to build a larger solar array than we need.
Since we purchased the Chevy Volt in May 2012, we have not had a net export for any given month because the Volt requires up to 13 kWh for a full charge (about as much energy as our house uses daily). We do not always use up a full charge - on some days when we only run short errands we may only use a partial charge (meaning less than 40 miles range in the summer). So our monthly electric bills have averaged between $15 and $18 from April to September 2013. Here is a chart showing our total daily import versus export:
While most of the variation in our daily net energy use has to do with cloud cover affecting the solar arrays output, there are also periods where our use of the Volt has a significant impact on the net energy for the day.
Below is a chart showing net energy for a typical solar day recently where we were exporting power while the sun was shining, but then we charged the Volt in the evening which used around 3700 W for 3 1/2 hours. So on this particular day we nearly broke even. If this had been a clear, sunny summer day - we would have had some slight export even after fully charging the Volt.
The bottom line is that we are driving our electric vehicle nearly for free within its electric range on average while also providing all of our domestic needs via the solar array.
Recently I was talking with a friend of mine whom I had assumed was somewhat knowledgeable about solar energy. I was surprised when he made the assertion that “solar panels only produce power in direct sunlight”. I corrected him and informed him that even on heavily overcast days, my solar array can produce over 3 kWh. But on a typical sunny day like yesterday, September 20 you can see the power curve shows power being generated before and after sun strikes my solar array which is facing West at 270°. Sunrise on this day was at 6:25 AM and it set at 6:38 PM, and my array was producing power for every minute of this time.
Total amount of power produced on this day was 22.9 kWH and the sun first hit the solar array at around 9:20 AM and Dropped behind the trees at around 5:30 PM (17:30). As you can see my solar array was producing hundreds of Watts before and after the sun was shining directly on the panels.
Compare this with the power curve from today which was heavily overcast with the sun barely making an appearance, yet the array produced 9.71kWH.
When I installed a tracking system for the two solar panels that I added to the south wall of my workshop back in June, I did not expect to notice them moving very often. Theoretically they would move incrementally every day to continuously adjust for seasonal solar elevation changes. However, what happens is that whenever clouds pass over the sun on a partially cloudy day the panels tilt down toward a brighter part of the sky in the south. Today I went out with my camera and took time lapse images every 10 seconds for around six minutes. The wind was gusting from 15 to 20 mph, and small dense clouds were moving across the sky fairly quickly. The GIF animation below condenses 6 minutes into 6 seconds and you can clearly see the panels tracking even the slightest cloud cover.
I cannot be certain, but I believe this is squeezing a few more Watts out of those 2 240 W panels that are fed through Enphase M215 inverters that can produce a peak of around 220 W when facing directly into the sun on an ideal day.
I have been keeping meticulous records since I installed our solar array in 2009, and have been keeping all this information in a spreadsheet. One of the things I have been doing is comparing the estimated power I should expect with the actual power generated. The National Renewable Energy Lamps tool called PVWatts allows you to input the specifics of your solar array including its location, number of panels, and orientation etc. so that it can give you an estimate of how much power you should expect. At the end of every utility billing cycle, I access the records from the web interface for the solar inverters on my system to determine exactly how much power was produced by the array for each month. The chart below shows the calculated estimate vs. actual production. Notice that the estimated production bumps up each year as I have added panels to the array. The scale on the left represents kilowatt hours per month.
Recently I discovered an unexpected benefit to the tracking system I designed for the 2 - 230 W solar panels I added to the south wall of my building. Since my office is on the second floor I notice whenever the linear motors activate to move the panels because I can hear the motors running. I had not expected to notice them moving since the whole idea is simply to adjust the tilt angle seasonally. But one day a storm blew in from the north and a big dark cloud came in over the building leaving the southern sky bright and sunny. My tracking system automatically tilted the solar panels down to point directly at the brighter part of the sky. And since then I have noticed the panels adjusting slightly whenever heavy cloud moves over. I had not expected to be squeezing every tiny watt out of these panels, and it is kind of fun to watch them adjusting to condition. in the photo below, you can see the tracking sensor in the red plastic dome. Inside there are two small light sensors on each side of a horizontal piece of metal painted flat black. When that metal shades one of the sensors it sends a signal to drive the motors to move it out of shade ensuring that the panel is always directly pointed at the brightest source of light.
Since we purchased the Chevy Volt, I have installed five more solar panels on my workshop building to achieve a total array specification of around 5.8 kW peak capacity. On a good sunny day our solar array can generate over 30 kWh, while the Volt requires a little over 13 kWh for a full charge. In theory that should leave us with a significant surplus in the summer and allow us to drive the Volt for free on those days. In reality we have yet to see a zero or negative monthly electric bill, partly because it has been an unusually overcast year to date (climate change?).
I had hoped that the additional panels would help to offset the charging power that the Volt uses via the 240 V charging station that draws 3700 Watts for 3.5 hours to fully charge the vehicle. So recently I decided to go through all of my solar power data and the records I keep of weekly charging power for the Volt and calculate what our electric bill would be if we did not have an electric vehicle. Here is a chart that I created showing our calculated monthly energy bills:
The calculated average monthly bill would be $10.57. This was my original goal for the solar power system - to provide almost all of the power for our home. So essentially I have accomplished that, now I have to think about where to put additional panels to offset the power needed to charge the Volt! I have been eyeing the east facing roof of the house, but my concern is that it is so high that I would be uncomfortable doing the installation with the help of neighbors and friends. I really dislike paying other people to do things I should be able to do myself. So for now this is a stalemate.
When I first mounted 2 additional panels to the south wall of my workshop it was March and I mounted them at a steep angle. Later in the season as the sun rose higher in the sky I extended the brackets to capture more energy in the summer months by tilting them further out from the wall. I realized that an optimal solution would be to adjust them frequently to optimize performance. So I decided to build my own tracking system that would adjust the tilt angle automatically. I started by designing a sun sensor that uses two photocells inside a little green plastic dome:
A flat black piece of metal separates them and when the sun shadows one of the cells it sends a signal to the control box that I designed that moves the linear actuators that I purchased. This image shows the control box mounted to the wall inside my window with the sensor mounted to the side of one of the panels so that it moves with the panel:
And here is a closer picture showing the control box that I built:
Here is my schematic if you are interested in making one for yourself.
I can set the slide switch to the left position which puts the system into automatic, or in the right (manual) position I can press the green button to tilt the panels out away from the wall, or the red button to tilt them back in. This may come in handy in the winter when I need to shed snow off the solar panels, or “furl” them in the case of high winds. The stroke of the linear actuators can drive the panels from about 24° in winter 52° in summer. This is the best range I could accomplish with the available actuator lengths (my winter solstice elevation is 22.4° and summer elevation is 67.18° here in Maine). The actuators have built in switches that shut off the motors at their maximum extensions so they do not try to drive beyond their limits. Since we are close to the summer solstice right now the actuators are fully extended, and over the next several months I will see the system adjust as the sun angle lowers.
I have been fooling around with this great web calculator produced by PVeducation.org that produces charts of available solar energy (insolation). So I have combined this with my recent interest in GIF animation to produce the chart below that shows the available solar energy in Watts/square meter in 10 day increments for the year at my location of 44° latitude North.
I made this animation by taking screenshots at ten-day intervals by adjusting the slider on the calculators webpage.
This clearly demonstrates how the amount of available sun hours per day varies significantly at my latitude. Of course, at the equator there would be very little variation at all, and at the poles you would see almost no sunlight for half of the year.
When I recently added 2 solar panels to the south wall of my workshop, it was early spring and I felt that a steep angle would be appropriate to catch the low winter sun so I mounted them at 70° from horizontal. Recently, when I looked at my performance statistics on my Enlighten web interface I noticed that I was no longer seeing a peak power of over 220 Watts on each panel. So I did some research to determine how much more power I would get if I changed the panel to a 44° tilt angle. Since I live at about 44° latitude, this should make for an ideal average angle. I found a web calculator that allows me to see the relative per module power for each tilt angle, see below:
I have animated the two tilt angle curves so you can see the comparison. This made it clear that I would gain a significant amount of power in the summer by changing the tilt to 44°, so I cut two longer pieces of angle aluminum and have moved one panel up so that I can see the difference:
Here is the proof that tilting to the the panel up to 45 degrees improves performance, this shows peak Watts at solar noon:
Now to go up there an tilt the second panel!
After installing the two additional solar panels on the south wall of my workshop, I have been keeping an eye on the Enphase Enlighten web interface for my solar array to see how well they are performing. I quickly noticed that in the morning between 8:30 and 10:30 one of the panels was getting a lot less power than the other. When I walked around to eyeball things I realized there was a poplar tree that was shading one panel during those hours and compromising the power output dramatically:
The tree shown in the image below is leaning at a bad angle and poplar trees often are weak and will collapse under heavy snow loads or winds.
So I felt it was time to remove that tree before it came down and hit a power line or the building. I am mentoring a high school student named Ben on Friday afternoons, and used this opportunity to teach him how to use a chainsaw safely. Here he is finishing up cutting the trunk into firewood length pieces using my electric chainsaw. We split and stacked the wood together and got enough to heat my workshop for a few days.
The following morning I checked my Enlighten webpage to confirm that I am now getting more power on the one solar panel:
The thing about solar panels is that they often run into shading issues as trees grow. I recently had to move a solar panel on the house since it was easier to move the panel than cut the tree in question.
There is a tool available from the NREL (National Renewable Energy Labs) called PVWatts that allows you to estimate the energy that should be produced by a given sized solar array within the United States. It uses meteorological data for your location to accurately estimate the actual number of sun hours per day/week/month etc. along with specifics of your solar array such as tilt angle and azimuth etc. Here is a chart that I have been keeping showing estimated power vs. actual power generated for the exact same time periods. I get the power generated by my array from reports from my Enphase Envoy web monitoring system. The shape of the calculated curve changes year-to-year as I have been adding solar panels and adjusting the estimate based on the additional wattage available.
As you can see, it appears that actual energy produced is varying more and more from the calculated estimate. I am not sure whether this is natural variability, or if Climate Change is having an impact. As I talk to locals who have lived here in Maine for decades they are all noticing that the lakes are icing out earlier in the spring and freezing much later in the fall. But people don’t really notice a substantial change in cloud cover year-to-year because that is not remembered easily. It is clouds that are the enemy of solar power, and of course their absence is a bonus as can be seen in the fall of 2012.
When I decided to add two more solar panels to the south wall of my workshop, I began by adding the panels to the 3-D model I had already built using Google’s free SketchUp CAD program. I was able to explore the optimal location and tilt angle of these panels before I installed them since this would save me an enormous amount of trouble climbing around on my building trying to eyeball dimensions and locations. I did not bother to model the line of trees along the east side (on the right in the images) of the building, because they would have a relatively minimal impact on these two additional panels in the summer mornings. Since some of those trees are on my property, they may fall victim to my chainsaw if they are shading my panels too much.
I began my solar power installation in 2009 by installing 21 panels at a cost of $3.28 per watt. Over the years I have added panels to the point that I now have 31 panels installed for a total of about 5.8kW. Solar panel prices have dropped consistently since I installed my first panels and the most recent panels cost me $1.08/Watt. This means that if I had waited until now to install my system I would haveve saved many thousands of dollars and the break even return on investment would be much shorter. Depending on how one finances the system today one can see a breakeven point of 12 to 18 months, and in states with very high electrical costs a much shorter period than that. In solar parlance, this is referred to as “grid parity”, meaning that solar now is as affordable as utility power in many cases.
Here’s a list and chart of all of my solar panel purchases correlating $/Watt:
Click here to see live statistics from my solar array and learn more about the installation.