| Our Solar Array Current Stats |
| Current Statistics | Historical Statistics | Grid vs. Production Historical Statistics |
| Here are some current statistics for our solar array. The current information is being retrieved directly
from the Envoy monitor (in our basement), which communicates with the individual inverters on each panel.
Other statistics are being calculated from that data as it gets stored in a MySQL database. |
| WEST TISBURY WEATHER |
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| Today's Production vs.
Grid Voltage 3 Please see footnote 6 for Production Timeline issues. (Updated at 1:45 pm) Grid within Specs. | Panels Online Today vs. Sun Elevation Max sun elevation today: 33 degrees. (Updated at 1:45 pm - Offline Panel History) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Individual Panel Status 62 of 62 panels Online - See picture at top of page (Updated at 1:57 pm)
Offline Panel History | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| A Little History | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| We have a 62 panel, 13.33 kW, ground based Solar Array that was installed in 2012. It has been on line since August of that year, and has been working well. When this system was originally designed, our house was totally electric, with the exception of an oil fired hot air system for our primary heat. At that time, the design was based on our typical total yearly power usage, and this system produced more electricity than we used in the summer, and less than what we used in the winter, and we pretty much broke even (production vs. consumption) over a given year. We have since replaced the oil hot air system with an electric heat pump (backed up by Propane), which supplies both heat and AC, so we aren't quite breaking even (production vs. consumption) anymore, but we still come pretty close. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
We had originally been setup to manually report our production monthly to the state, but in 2019 South Mountain Co. helped us get setup for auto reporting by swapping out our solar meter with one capable of doing this (the policy in MA was, at that time, auto reporting is required for any array over 10 kW, which ours is - not sure why we were able to manually report for the first 7 years). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
UPDATE 6/22: Due to issues we were having after our leasing company insisted on putting in their own meter (5/2022), and dragging their feet on getting it registered with the state for auto reporting for the SREC program, we talked to the folks at the PTS (Production Tracking System) department at MassCEC to see what our options were. We found out that the rules have been updated, and it is now possible to manually report on systems up to 25 kW (as opposed to the old rule of a max of 10 kW). As a result, we are back to manually reporting our production for now. As a side note, if you are planning on going solar, our recommendation is to avoid leasing if at all possible. Our lease has been bought out twice, and the current company has been a nightmare to deal with. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
UPDATE 11/22: Due to ongoing issues we were having with our leasing company (constant billing issues, lack of support, unwillingness to repair anything, etc), we made the decision to attempt to buy out our lease, which we were able to complete this month (11/22). In the 2-1/2 years they had owned our lease, they had refused to repair anything (4 inverters failed during that time) because they claimed the system was still producing what the lease guaranteed would be the minimum production. However, this meant we were producing fewer SRECs, and were buying more from the electric company, and thus it was actually costing us more than if the system were fully operational (and of course, the monthly lease cost did not go down). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The array has been very reliable so far. This array is setup with panels that each have their own inverters, as opposed to a multi panel system with a single, large, inverter. Because of this, if one panel is in the shade, it doesn't bring down the entire array. This has advantages for systems mounted on the ground with some trees around that might affect some panels, say, in the morning and afternoon (like ours). So far, since installation in 2012, 12 inverters (out of 62) have needed to be replaced (as of May 2024), but they have a 25 year warranty, and since the entire array is on the ground, it only takes around 30 minutes to replace one. The original monitor device (that collects data from the inverters) failed the first year, but the replacement has been fine since then. Other than that, plus swapping out the original meter to allow for auto reporting, this has been the only maintenance that has been required so far (as of May 2024). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The Inverters and monitor device are from Enphase. The Enphase Envoy monitor (sits in our basement) communicates with the individual inverters via a carrier signal on the 240 Volt line from the array, and has a small web server in it that can be accessed locally. It also 'phones home' periodically to Enphase, and stats and reports can be obtained on their web site with a login account. The information displayed on this site above is extracted directly from the Envoy monitor web site and saved in a database locally. Current stats are displayed directly, and the local database is used to display the historical data (Production History and Production vs. Grid History). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
We found an interesting site that will calculate the position of the sun for any given location, date, and time of day. If you select the Esri Satellite (upper right blue square icon), you can place the calculator right over your array location. As an interesting side note, using this site with the Esri Satellite setting (our array is actually visible in the satellite image), we noticed that our array must have been setup using a magnetic compass, and therefore is pointing to Magnetic South, not True South, which is not entirely ideal. As an airplane pilot in the past, we were taught to be aware of the difference between True North and Magnetic North (among other magnetic compass issues). The magnetic poles are continuously slowly moving (check out this site to calculate for your location). For a graphical picture of what the current declination is for our area, click this link. Thus, in our area, the current declination as of today is approximately -14.04. Back in 2012 when our array was installed, the declination was around -14.70 degrees. In other words, our array is actually pointing around 14.70 degrees to the East of True South (or around 165.3 degrees). We don't really know how much this might affect actual production - it probably sees a bit more sun in the mornings, and a bit less in the afternoons - than if it was pointed to True South. Interestingly, it does seem that peak output during a sunny day does happen right around 12:00pm during the summer months, but since we are in Daylight Savings Time then, this is actually 11:00am Standard Time. According to the Enphase site, our system has been producing a bit more than expected based on the design specs, so we aren't terribly concerned, but if one is installing a ground based system, it is worth keeping this in mind (not much choice if placing panels on an existing roof, of course). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Footnotes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 1
Although the system is DC rated at 14.88 kW (62 panels rated at 240 Watts DC each), the actual maximum AC
output is limited by the inverters, which are rated at 215 Watts AC each. The inverters will
limit the AC output to a max of 215 Watts even if the panels are trying to produce a little more. This design
apparently leads to a bit of a boost in performance over a year of different seasons. Thus, 215 Watts x 62
panels = 13.33 kW max design output. During peak production months, we have, however, seen the peak
production of the array reach slightly (1% - 3%) over the 13.33 kW rated max. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 2
The Current Output gauge may not always agree with the Today's Production graph above it because the
graph gets updated every 15 minutes from the database, where as the gauge gets updated whenever the page is
loaded or refreshed. As a result, the graph may sometimes lag slightly behind the guage in regards to current
output of the array. The Peak value is pulled from the database as well, so it may also lag a bit
behind the current output value. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 3
Grid voltage on the 240 Volt supply line is being calculated by doubling the measured Voltage at a 120 Volt
outlet. This assumes the two 120 Volt legs of the 240 supply are close to being balanced,
which should be the case, but, therefore, this is not necessarily perfectly accurate.
The Min and Max values are based on the accepted tolerance in the US for the 120 Volt legs to be
120 VAC +/- 5%, which works out to 114 to 126 VAC, or 228 to 252 VAC for the grid. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 4
Current grid amperage here is approximated by dividing the current production in Watts by the current Grid Voltage
(as seen at an outlet and multiplied by 2). The current grid voltage and array output amperage information is
not available from the Enphase monitor and as such, both here are somewhat approximate (see footnote 3 for
the displayed voltage info). The output amperage of the array and resulting grid voltage are both affected by the
load the grid and array are seeing, which includes varying amounts of resistive and inductive loads.
Calculating the amperage for a given wattage and voltage into an inductive load involves calculating in a
'power factor', which we do not have access to. The solar meter at the array cycles through displaying the
current voltage, wattage, and amperage, and the relationship between them does not fit the simple formula for
a stricly resistive load, which is Amperage = Wattage / Voltage. At higher wattage output, it seems pretty close,
but at lower wattages, it seems less so. Therefore, take this figure as a rough estimate, and not what the meter
is probably actually displaying. Current Amperage is calculated each time the page is refreshed, based on the
current array output and current grid voltage, whereas Peak Amperage is calculated from data pulled from the
database, which is updated every 15 minutes. The Peak Amperage obtained from the database is then compared to
the Current Amperage, and the higher of the two is what is displayed. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 5
Yearly average is calculated using recorded yearly totals for previous full years (2013 through 2023),
divided by the number of full years (11), so should be pretty accurate. Keep in mind that some of these are leap years. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 6
It should be noted that, when comparing the grid voltage with the production curve, that the timing may not
be perfectly synced up between them. The timing of the grid voltage graphing is pretty accurate, as the grid
voltage at an outlet is updated once a minute, so when the database is updated every 15 minutes, the voltage
reading should be withing a minute or so. The production information is collected from the inverters by
the monitor, but is only done so periodically, and not all at the same time (and we do not know exactly how
this timing is handled by the monitor). The inverters save the data they have collected for each panel until
the monitor asks for it, so the production data may actually lag a bit on the time line, compared to the
grid voltage data. As an example, on a sunny day in October 2023, we shut down the entire array using the main cutoff switch. It took about an hour for the monitor to indicate that all of the panels were off line, and not producing (thus, the website graphs for Production and Panels Online were about 1 hour behind real time, even though all of the panels went off line at the same time). After turning the main cutoff switch back on, it was almost 1 hour before the monitor showed all panels back on line and producing (part of this timing is due to the interrogation timing of the monitor, and the time it takes for the inverters to reboot and reset, which means the panels actually don't come back on line at exactly the same time). On the web page graphs, the time between it showing the cutoff, and fully back on line times does corrospond to the one hour that the array was off, however, the events show up about an hour late on the timeline due to the interrogation delays of the monitor. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Current Statistics | Historical Statistics | Grid vs. Production Historical Statistics
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