Building Reserve and Using KWH

[DanS26]

Bruce I hope you have a grandfathered contract that is forever renewed.

Some REMC POCOs are run by good old boy board of directors that have no clue or business sense. The deal you have is absolute economic nonsense. Good for you!

You better keep that contract in a safe because it's worth its weight in gold.

[bcroe]

Thanks to the weather this has been my worst solar production
year ever. Usually I have some 11,500KWh of energy in reserve
on this date, to be consumed over the winter. I only see
10,300KWh on the spinning disc meter. The system is working
very well, but the clouds are so common, and I may also be losing
to the smoke from the left coast. But I think it will be enough.

I took a shot at measuring net metering inverter efficiency, waiting
for stable strong sun to give clipping. If I believe the inverter
display of voltage and current, input and output, the efficiency of
each is near 93%. Maybe the readout errs, the efficiency was rated
95%. I doubt it has dropped that much, which would cause a lot
more heating. Or is it a hint they are getting old?

I continue to be bombarded with ads for Smart Thermostats. The
price listed is astronomical, which then allows these supposedly
generous rebates. I will just continue to use my little round, tilting
mercury tube thermostat, which will last a lifetime with no batteries
and no maintenance.

Seems natural gas price has tripled in 3 years, electricity is way up
too, propane is probably doing the same. Not buying any here.
Every year the solar science experiment looks like a better investment.

The energy use situation here has hardly changed in 2 years, I do
now have a pretty small attic vent fan with heat/humidity control,
runs a lot of the year. I am told it will help my energy situation,
but that is minimized by good insulation. A complete measurement
would be need to be made for the entire year.

The percent clipping meter did not get built this year.

I have shown an output graph of keeping my inverters in clipping 8
hours straight in good sun. That over the majority of months. BUT
the time never increases, even on the longest day of the year. My
observation of the cause, is the sun rising and setting so far to the
north, trees are shading the panels. One cure might be build a
different array, another is my chain saw. The snow rejection of
the older sections could be improved. We shall see.

The last, variable tilt, snow rejection array construction has been
superior. But increasingly expensive to construct, with the price of
materials. I realized it could easily be built as double sided, with
minimal additional construction cost. So mounting twice as many
PV panels on it would be more economical, with panels so cheap.
Of course this wants to face E-W, at an angle better for snow rejection.

Bruce Roe

[DanS26]

Installed my Nyle in April 2012...so over 10 years of excellent service. Replaced a relay about 5 years ago was the the only time I had to touch it. The unit is well built...I expect at least a 20 year life. My only ding is that it uses neutral switching to control the unit instead of power phase switching. I talked to their engineers about that design and they stated the new unit would not have neutral switching on their 120v systems. I added an extra thermostat control on the input side of things because I don't trust neutral switching in that type of device. Cut in set for 95* and cut out at 125*. Very quiet and efficient......I do not know if it's running unless I'm standing right next to it.

Don't know why the delay in the new E8 product......but the marketing and specs look good.......

https://www.nyle.com/water-heating-systems/units/e8/

[bcroe]

I use a Nyle system. I only run it during late spring, summer and early fall. It is also on a timer so that it only operates during daylight hours. In the warm months it will use ~50 to 60 kWh per month and generate most of our hot water requirements.

Very efficient and quiet. Since it is also rated as a one ton AC I have it connected to the cold return duct work but as you see I also installed a louver to redirect the cold air during late spring and early fall when the house is too cool for additional AC.

So another year, Nyle periodically says the unit will be available,
but once again failed to deliver it. Bruce Roe

[bcroe]

Another Net Metering year, the weather only gave me 29,000 KWh, still
about 7% more than I consumed. 1st net metering month April was just
terrible, unseasonably cold used a lot of energy, so many clouds limited
energy collected. Still got thru with 500KWh surplus, no buying energy.
That array can usually break even under clouds, but it really delivers
under sun.

I was promised the availability of a heat pump that can attach to any
water heater, for the 3rd year it did not materialize. Have been thinking
of some kind of dual mode setup, using inside summer air to help AC
and dehumidify in summer, some other heat source in winter.

Meantime energy sources have been running wild, Mon I put a re
conditioned 24 gallon tank on the 77, and the pump shut off at a $100
limit before it was full. Good thing my coast to cost travels are way down.

Both the connect fees and the energy charges continue to escalate,
my crazy idea to not connect to the gas line, and generate all property
energy with solar, is starting to look not so crazy. Bruce Roe

[DanS26]

I have never had a single MC4 failed connection in over 10 years...(knock on wood)....I use silver conductive grease sparingly on every connection and make sure the connection is torqued each the same. I also make sure every connection is away from the rain and at the the high point of a drip loop.

Silver conductive grease I believe is the secret sauce, but never use too much since it could cause a short in the connection if it oozes. Some people confuse it with di-electric grease which will have an opposite effect. Silver conductive grease is expensive but I think worth every penny.........

https://www.amazon.com/MG-Chemicals-Conductive-conductivity-Dispenser/dp/B005T8QLYM/ref=sr_1_2?crid=19Z469DT2LAXZ&keywords=silver+conductive+grease&qid=1649186294&sprefix=silver+conductive+grease%2Caps%2C6908&sr=8-2

[bcroe]

Dan, your method is much more expedient than mine. That is pretty
much what I did, the first time working on the array wiring. But panels
have no power switch, so daytime work requires a lot of care. These
days I just do not like shutting anything down in daylight.

I recommend the DC disconnect switch to the inverter breaks both wires.
My installer used one switch, 2 poles breaking the POS hot lead on the
2 systems. This had the obvious disadvantage that one system could
not be disconnected while the other was running. When it first operated,
the installer had left me some unacceptable wiring mangement (or lack of).

While I was DC disconnected and rerouting a wire, apparently it brushed
the frame and blew the inverter ground fault fuse. This caused some panic
and took a while to figure out. These problems go away with 2 DC
disconnect switches, each breaking both the POS and NEG leads of a system.

Living on the property, I am not in a hurry to solve a problem, if the losses
are small. The price is setting up night lights, and another day for each
setup change. But I do not need to disconnect every panel. My first stage
test would find wiring problems, completed once by following the wire to a
burned out MC4. The next stage (day) is to identify individual panels. Can
take extra days if strong sun goes away.

My tests are made with the panels connected, with MPPT loading. My
experience with a disconnect panel is that voltage tests will not find much,
and short circuit current will not reveal part of a panel being bypassed. I
need to see all sections work together without any bypassing, hard to be
sure of when disconnected.

When I first connected 40 no name panels (purchased at different times),
I found 3 that sometimes would partially bypass. While I might still find a
use for these under producers, swapping in others put this array at peak
efficiency. Getting this good a match would be difficult, doing MPPT
testing of individual panels, under a less than stable sun. A similar thing
happened with the pine sap coating, the degraded panels would drift in
and out of bypassing. When the worst offender was cleaned, another
became an offender.

All the same panels are still in service today, 8.5 years later. Most of the
several hundred MC4 connectors have been apart and together at some
point, for testing and rewiring the snow resistant arrangement. From the
quality seen, I sort of expect each time, some fraction of the MC4s might
need replacement, this time using NoOx on contacts. I am leaving them
alone for now. Bruce Roe

[DanS26]

Bruce, I take a somewhat different approach when trying to find an underperforming panel. Our solar plants are very similar. As you know, I have 96 ground mount panels made up of 8 strings feeding two Fronius 7.5kW inverters. Because its a matched set any time one inverter is performing poorly I can eliminate 4 strings and concentrate on the remaining strings. With my trusty DC Amp meter I can now identify the problem string of 12 panels.

Now here is where we differ on approach to identifying the problem panel(s).........

1. I shut down the AC feed to the lower performing inverter. That shuts down the DC load.
2. Next is to open the DC switch feeding the inverter.
3. Next I open all the combiner box 15 amp touchless fuses....all 4 of them.
4. Now that I'm sure the load is removed from the offending string which I double check to confirm no voltage, I proceed to detach all 12 panels from the string.
5. In full sunlight I now check the voltage and short circuit amperage in each panel with my trusty Fluke multimeter.

At this point I can usually find the problem, but if I still cannot find the panel then I have to check each panel under load.......

6. Using a 12v car battery and a cheap charge controller, I rig up a test system with my Fluke in the middle to measure amp production for each panel under load.

All along the way I'm also looking for poor, loose and corroded connections.

[bcroe]

The multiple string PV solar system here had a problem, here is my method to track
down an array issue.

This system is actually two complete 7.5KW inverter systems with identical panel
arrays. On a clear midday with good sun, the outputs usually match very closely. It
was noted, that the WEST system output was lagging the EAST system by several
hundred watts.

The ground mount array looked like this, all the strings operate at the same voltage
since they are wired in parallel. Variations in power will be caused mostly by variations
in string current. The first step was to use a clamp on DC ammeter to check the
current of each string. This gives best results under strong sun, and STRING 6 was
found to be lagging the others.

StringsTest.jpg

The normalized output of a solar cell looks like this, with about half a volt MPPT per
cell today. These strings have 12 panels of 60 cells wired in series. With 720 cells
in series the string MPPT total voltage is about 360V. With todays low sun and my
poor, rather low winter elevation, the MPPT current was about 5.5A. With a series
connection all cells in a string are forced to conduct the same current. Even with
matched panels the precise MPPT current will vary slightly, but each cell will vary its
voltage slightly to match the current of the others. This will normally stay pretty close
to the broad power curve MPPT top. The problem comes when a sufficient reduction
in voltage to match current, is far from the rated MPPT voltage. This fault condition
might run the panel (or a portion of a panel) all the way down to zero volts without
reaching a matching current. In that case a panel bypass diode will conduct to avoid
much reverse voltage.

PvMpp.png

The shift in voltage is used here to find an under producing element. A voltmeter can
detect the low voltage element, the rest of the string will raise its voltage to match the
other strings, but in sliding up the voltage curve, the current (and the POWER) drop.

My 12 panel strings looks like this, the big problem is actually connecting a voltmeter
to the weather proof wiring. To narrow it down, I would like to measure the voltage
across each quarter of the string, toward finding the under producer. The negative
end is at ground potential here, so the frame can be a test point. 4 more test points
are needed as indicated.

StringTest.jpg

I break apart the MC4s where indicated and insert a 3 way MC4 connector like this.
The 3rd port will be a voltmeter access. But WAIT A MINUTE! This array can deliver
enough power to cook 50 hot dogs at a time, and breaking any DC connection under
load can cause awful, equipment damaging arcs. Leaving any conductors exposed
to the weather can also cause serious damage.

3wayMC4.JPG

So here it must be PITCH BLACK to work on wiring, AC outlets at the array allow
use of work lights. The 3rd port is not left exposed. An MC4 with no conducting
metal is plugged in, its wire hole is plugged and the latches are ground off. The O
ring will retain it briefly. Then wait for good noontime sun.

Noon next day, the voltmeter reveals that three of the string sections accessed
are running good voltage, the section nearest the POS output is low. Just making
the measurements needs some special test leads. Long extension wires (no
metal exposed) are connected to the voltmeter, to reach any point on the string.
At the ends of each are both a male and a female MC4, because the 3 ways might
have either. Again, the latches are ground off, so the plug may be removed and the
voltmeter connected quickly without tools. The plug can be put on the unused
voltmeter MC4. In general, MC4s are kept mated to avoid weathering.

MC4TestPr.JPG


Once the offending section is identified, the test points are moved into that area
to resolve to an individual panel. WAIT FOR NIGHT AGAIN. The new locations
are shown here, near the POS end.

StrinSegTest.jpg

Here is a pic of the offending section, the top 3 panels, with the test points
already moved to bracket each one. The night work light is to the right, the
cement mixer not involved.

StringSegTst.JPG

At this point one panel might stand out with way too little voltage under good sun.
Weak sun is found to be inconclusive. HOWEVER, my situation was different. The
first attempted fix was to replace (IN THE NIGHT) the center panel with my unused
spare. Next day the center panel voltage was right where it should be, but those on
either side were not good. These panels had previously been washed, which had
no effect.

A careful examination of the removed panel revealed a dark, rough, somewhat
streaked surface. I remembered, for a time a pine branch had grown out above the
3 panels, though not usually shadowing. The panels were coated with PINE SAP.
Washing with soap did nothing, alcohol did not do it either. I took a straight blade
from a utility knife and SCRAPED off a black powder. Fortunately the glass
underneath was very smooth, so the blade slid smoothly across once cleaned. IN
THE NIGHT I swapped it with the panel on the right as seen above.

UtilitBld.JPG


Next day, it was obvious, 2 of the 3 panels were at voltage. From the front, the
remaining panel (now on the right) was dark, clearly affected. Sap can also be
seen running down the edge of 2 original panels.

3PanPineSap.JPG

This panel was swapped with another scrapped clean panel, and all was well
again. OK but have I removed any panel protective coating? Time will tell.
NIGHT AGAIN, remove all the MC4 test access points.

So why not wire test points in the day? First opening a working circuit could
damage connectors or worse. MC4s are not so easy to separate, and slips
could be fatal.

Then why not open the fuse and test with no current flow? The panels need
to be checked under load, near their MPPT point. Even a bad panel often looks
good unloaded. Bruce Roe

[DanS26]

Here I use the DROKs to monitor my genset, note the frequency is the box on top. Very useful to monitor loads during an outage.

There's a lot going on with this panel that a few readers may be interested in......

It's a 10 position critical load panel that I modified to accept 12 positions
An N1 switch was installed to exercise the generator under load without interrupting power to the house. See the red label.
The item with the blue LED lights is a MidNite Solar SPD that protects the panel from high voltage surges that might emanate from a submersible pump.
Below that is an SPD from Levitron which protects the main distribution panel.
Next below is the DROK frequency meter.
Next below is the DROK phase A and B load meters.

Inside the panel are a low voltage monitor device that protects the switch mechanism from low voltage burnout and additional SPDs to protect the generator AC and DC control circuits.

Finally the switch was wired using the Canadian code method for critical load panels. That method requires that all wiring for critical loads be removed from the main panel and routed through a junction box before landing in the critical loads panel. I went a step further and used a pass through block in the junction box rather than a mess of wire nuts.


Monitoring.JPG

IMG-173.jpg

[bcroe]

Those DROK meters certainly are compact and economical, having integration over
time (KWH) and frequency a bonus. They do draw power on the order of a watt, so
the V leads need to be attached on the supply side of the current transformer to
avoid becoming part of the readout. Before them I had wired this into 240VAC ckts.

ENEmeter.png

I expect to be using the frequency readout if I run the gen set. PF could be
useful on big motors. Bruce Roe

[DanS26]

Here I use my DROKs to monitor my EV circuit..........

EV Circuit Monitor-001.jpg

[Ampster]

I used the same Drok device and it worked well. I my case it was to monitor current and voltage while parallel top balancing a LFP pack.

[bcroe]

Did you build that 240V power meter yourself?

The readouts are DROK 80-300V 100A Voltage/Current/Power Factor/Frequency/Electric Energy Monitor
I picked up for $21 from Amaz. I use a pair because sometimes the load may be unsymetric, so then one for
each 120V line. The rest is just a box for a 4 wire 50A plug feeding a same socket, the hot 120V wires passing
thru the meters current transformers. Each has a pair of voltage wires, one of each meter is connected to that
wire. The neutral volt wires are connected together, and switched to the big neutral for 2 meters. The switch
can connect that node to a 120V line instead, then one meter monitors a single 240v load and the other is off.
Bruce Roe

4W50ADVM1.JPG

[nerdralph]

Still clinging to the old technology is my very reliable, easily repaired, electric stove.
At the beginning of my PV Net Metering, it actually did a lot more than heat food, and
there were a few days when every incandescent light in the house was left turned on
24/7. No need for that anymore. Most seasons my 240V KWH meters show the stove
only uses about 0.4 KWh a day, not even 1% of my energy budget. It, with some
standby drain, is an acceptable tradeoff.

240KWM2.JPG
Bruce Roe

Did you build that 240V power meter yourself?