19 January 2014

Monitoring Your System

Introduction

Once you get a solar panel system installed with a panel level monitoring system, you become more aware of the solar cycle that that interested man kind for the past 20,000 years.  You can visually see the Sun low on the horizon on 21 December and quickly rise up at the end of December and early in January.  This continues of course until 21 June when the cycle starts to go backwards.  I can even see this effect on the instantaneous output of the South and East panels early in the morning.

Discussion: 

What I would like to see in a monitoring system is instantaneous, peak production, daily production, hourly, daily, weekly and monthly output per individual panels.  One of the first limitations that you see with all panel monitoring systems is that they are internet based.  That is so that they can sell you the monitoring system at some time.  Ours is included with the system for 20 years.  What I want to see overall is if any panels are not working up to stuff or are there shading issues that I am not aware of.  Being Internet based, the panel information is only captured and shown every 15 min.  Therefore it is an approximation of what is happening. With clouds moving in and out across the Sun, you can miss the any peak values that may occur in the system.  For example, our peak values showed up a few days ago as around 6.6 kW but I was able to observe a peak value of around 8.4 kW via the DC/AC  Inverter panel display.

I am speaking about an overall system monitoring program.  You revenue meter insures that all power produced is shown and paid for regardless of what you may monitor.

SolarEdge does a good job in showing the output of every panel and highlighting low production panels for easy identification.  It also helps me to see that the way the snow is left on the panel can have a major impact on the panels output.  If 3-4 inches wide of snow is left longitudinally on the panel and 90% or so of the panel is left clear, the snow will reduce the panel's output by about 80%.  That helps to highlight how important it is to clear all the snow off of the panel.  The same effect occurs with early morning Sun and any shading caused by buildings and roofs, structures or trees. 

SolarEdge just recently (this week) changed the way that we can see the data that is collected.  By using the playback feature of the system, you can see the approximate output of each panel in Watt per sec.  That is what we would sometimes like to know.  We have 225 W panels and we can see the values rise from 10 to 180 W/s.  That is nice to know.  Being able to raise and lower my East and West panels, selecting the optimum angle is a bit tricky.  Now I am able to see just when the East panel outputs equal the South panels output or when the East and West panels should be raised or lowered to better optimize the system.  I have a 3 position switch for the panels, so there is not much room to optimize the daily output but it does help a lot because these panels can benefit form morning and afternoon Sun light equally.

Another great feature of this monitoring system is the histogram plotting of the system output.  I can see that if the weather is co-operating, I can get a very rapid rise in system output as the Sun rises early in the morning. This is showing how the South panels react to the sunlight early in the morning as it rises from the south-east. A slower response would mean that you would benefit from more East facing panels,  South panels do an amazing job here.  Currently in mid January, they equal the output of the East facing panels at around 10 AM.  East facing panels tend to peak at around 10:30 due to the fixed angle of the roof being as high an angle that I can go.  The West panels can exceed the angle of the East panels as they can be raised a bit higher in the morning to face the Sun.  That means that they will also stop peaking earlier and would benefit by a small change in the angle facing the Sun.

In the past, system owners would have to record the hourly output from each panel in order to determine the panels output power.  The recent inclusion of the play back recording now makes this a thing of the past.

Summary:

Over all I am very pleased with our panel monitoring system.  The biggest complaint is that it is internet based and not locally supported on my computer as it should be.  We can see and identify any panels not producing properly and see any unforeseen shading issues.  You can see the system charts and outputs by going to the SolarEdge website and  following the link located at the top of the page that says "Monitoring Portal Login".  Then go the the public sites and type in Lakeshore.  Select Lakeshore3 to see our results.

As a closing note, you will see the system panel layout, production summaries and all of the bells and whistles.  You will also see that almost every panel will have a slightly different output.  Remember, that without having panel optimizers, you would lose the power generated from each panel that is about the lowest value.  In my case that is very high as one panel is typically producing 10% lower and another panel which will be replaced, is producing about 30% lower than it should be.  That would rob us of over $40,000 if this situation was left un-noticed in a straight string inverter system as so many people tried to sell us.

Solar Production Update:

At or before the 15 January, overcast days are now producing 10 kW or more with next  to no observable sunshine.  It is not too dark but the sun normally isn't seen on these days.  This represents the break even day or point.  It is the minimum that you normally will earn even when the weather is "bad" or poor.  It covers you  monthly interest payment on your long term investment.  For example, today by 9:30 AM we were producing 2.25 kW and at 12:15 PM 8.0 kW (we can't exceed 10 kW).  This shows that you normally will produce 20-50% of your maximum output even with no sunshine.  The Sun did indeed just come out and we peaked at 9 kW (or $3.6 per hour)  On partially sunny days we are starting to produce about 30 kW or about $12 per day (or expressed $390 per month if every day were like this which it never normally is).  We have not yet seen a clear blue sky day in January, so that out put can only be estimate for this time of year to be around 50 kW ($20 per day or monthly rate of $620).  Unfortunately we never see that great of a solar day for many days in January, but we never expected to.  This varies from year to year.  The bottom line is that the system is starting to produce power at a return greater than the monthly interest charge.  This will only improve as the Sun moves or tracks higher in the sky.  We are doing very well as we have cleared the snow from the panels as I explained in an early post.  Having done so a few days ago, we only had a light dusting on most panels this AM.  I also removed snow this AM from two panels that I should have cleaned yesterday but forgot that I had installed a ladder support needed to safely do so.  I found the support this AM when clearing the snow. The wind is howling at around 30 mph or so gusts.  The light snow normally will just blow off the panels under these conditions.  The high wind will also really cool the panel improving its efficiency.  Solar panels produce heat and you can use the will chill temperature chart on them.  NOTE: Solar trackers lay flat when the wind exceeds 20 mph and the production goes down).   Extreme cold prevents snow from melting off the panels (-12 to -20 C).  One high producing panel remains with some fouling from snow that I couldn't reach.  Perhaps the high wind will help to remove the snow.