Building Reserve and Using KWH

[DanS26]

That net metering deal you got from the local REMC was too good to be true from the get go. I guess those good old boys finally woke up. At least you were able to pay for your system a couple of times over if not more.

Most REMC's are moving to net billing where they buy your excess production at wholesale and then make you pay retail to buy it back at night. In any case you got the early adopter benefits.

[bcroe]

In truth my tree line north of the arrays has slowly been retreating from age and trimming. I
am slowly forming an idea of another generation of panels and mounts, which would more
favor the northern sun and accommodate the larger celled panels. The current panels have
all been doing fine since 2013, one had to be swapped after a tree bent it. DC wiring has been
a problem with running high power many hours of every sunny day, but lately all those which
I had described have been fine.

The other thing is anticipation of the Po Co refusing to renew my Net Metering contract in
2033, so I have been looking at ways to more directly use my generation. Using the secondary
water heater element to absorb some energy and keep inverters out of clipping is a serious
consideration, if it plays out I might even have 2 of those lifetime tanks. Direct DC feed of
heat pumps might be possible, which also bypasses inverter losses. Some that connect to
solar panels already do this. With the house running pretty well and gutters + metal roof, I
am very much interested in some of the most efficient windows to replace these awful single
pane. Probably some multilayer with bird glass, a custom order for sure. But running without
Net Metering certainly will cause much less efficient use of facilities. Batteries are not on my
list, they cannot solve my summer to winter energy storage.

With the 2020 heavy 4/0 cable burial out to the inverter shed, the original 4 gauge feed could
be used to bring panel DC power to the house. Right now it just helps with the inverter AC
output. Need to learn to use the latest high power silicon carbide transistors. The Vampire
load chase never ends, these toroid transformers can really help. Bruce Roe

[SunEagle]

Thank you for the info Bruce. too bad about the solar cell size. Hope that doesn't hurt your system during a panel replacement

[bcroe]

14 May first time this year the 15 kw AC inverter plant delivered 150 kWh. I often
have seen the inverters in hard clipping for 8 hours straight, but those hours
never seemed to get any longer even longest day in June. I think I have figured
out why that is. The sun may rise and set nearly straight E and W around March,
but then the sun keeps moving to rise and set farther north, which means my
S facing panels are nearly cut off then. My E and W facing panels only see about
15 degrees max off for sun rise and set, BUT my trees in the north are shading the
panels at those times. To get the longest possible summer day would require
relying more on E W panels and cutting more trees.

Technology moves on, and I no longer can get new panels with 6in sq PV cells for
spares in my system. Had been using 60 or 72 cell panels, same width.
Bruce Roe

[solar pete]

Hi Bruce,

Thanks for the update, all seems to be going quite well. Good tip re the height of the ground mount system in areas that get snow, cheers.

[bcroe]

I constantly see pictures of solar panels and heat pumps mounted barely clear
of the ground. That works IF YOU NEVER GET SNOW. If the snow fall and drifting
is not enough, snow sliding off can build up a huge pile blocking it.

Reserve energy did maintain a positive slope til mid Nov. Then it started dropping
primarily because the sun went away. But by 1 Dec I still had 13,300 kWh for winter,
maybe a record here. Our reward for global warming is Arctic air sweeping down
here for some awfully long, cold winters. But the heat pumps deal with it, no action
from me required. Bruce Roe

[bcroe]

Rollover.jpg

The solar system builds up kWh reserve in Net Metering, starting in April.
I use a minimal amount in summer, so most generation then goes to the
reserve. It generally tops out at the beginning of Nov, then begins dropping
as generation decreases and heating use increases. There is quite a bit
left over on the next reset in April, seems to be increasing. This though I
suspect the actual panels are loosing a bit of capability every year. Good
reason to over panel.

Here is a list of reserve beginning Nov each year, primarily controlled by
the weather. With comments.
2013 3,339 incomplete starting year
2014 12,389 1st complete year
2015 12,389
2016 12,919
2017 13,947
2018 13,991
2019 12,116 E facing panels added
2020 13,448 heavy intra building cable reduces losses
2021 13,665
2022 11,478 fires smoke?
2023 13,824
2024 14,067
2025 14,605

Lately it seems to be rising, I suppose due to warmer weather? Also last year
and 2025, the peak seems to occur later, more like 15 Nov. This is easily seen
on my bi directional, spinning disk kWh meter. Bruce Roe

[bcroe]

We are seeing -7 F. The 6 Heat Pumps installed 2018-2020 are
all doing their jobs, which is usually heating buildings. They can
AC, but very little of that is required here. 5 are in the house, like
one in each corner and 1 in the area of the basement with an
outdoor wall. Starting with 3 HPs temps were a little uneven and
a fan helped one room. Now with more units and the house
blower circulating the air every hour, things are pretty good.

Some would say I have way too much HP capacity. But if one were
to fail, the others could just work a little harder, no crisis like a
furnace failure. What they call RIGHT SIZING I call JUST BARELY
ENOUGH FOR MOST SITUATIONS. And the minimum HP capacity
would be backed up by a resistive heat system with a COP of 1.
With my capacity the HPs can cover that too, automatically,
even if their COP drops pretty low for well below zero F. The
COP will pick up immediately as temps rise a bit. The factor
driving the above is initial cost. But mini splits are easily DIY,
bringing costs to less than half.

2023/4 saw some tree growth dropping sap on on one
panel string, which only gets removed with a scraper
(razor blade). The tree got cut back summer 2024, but
unfortunately a 250W panel was damaged by a falling
branch. It was replaced (in the dead of night) with my last
spare, better find some more.

The solar plant has been doing very well, with absolutely
minimum maintenance. I clear the snow off part of the array
about 4 times a year, the rest pretty much clear themselves.

In the switch over to straight electric water heating, I have
done some manual control of the previous propane unit. I am
suspecting after 13 years of our hard water, the high efficiency
is not so high. At my previous house with similar water heater,
it did not seem to run sooo long. And that unit could be
unplugged for several days before I ran out of hot water, this
one completely cools off in a day even with the circulator
turned off. PERHAPS mineral buildup on the heat exchanger is
interfering? This problem would go away with the electric heater,
the heat cannot go up a vent not present, it will find its way to
the water. If that strain eventually burns out the resistive
element, it is easily replaced. With 2 elements I would still have
service.

Bruce Roe

[solar pete]

Hi Bruce,

I always enjoy reading your reports, thanks for sharing mate, cheers

[bcroe]

In my 12th year of HVAC and electric being solar powered, things
are not too exciting. The same pair of 7.5KW Fronious inverters
providing Net Metering, remain in service. Another identical pair
remain as backup, one is mounted and could be switched into
service by reconnecting a pair of wires.

With regular attention to energy efficiency, the use of Heat Pumps
year around has left enough surplus energy to do several luxury
things. The backup propane furnace remains out of service, but
the (recently replaced) air circulation blower is run for a fraction of
every hour. This allows a large electronic air filter to minimize dust
in the air. Use of a central vacuum with outside exhaust does the
same. And I run a dehumidifier.

One of my goals is to avoid failures resulting in a crises situation,
such as the furnace quiting in winter. The HPs around the house
have done this very well, and the air circulation evens out temps
if one is not running. I am now testing to see what kind of lifetime
they will provide. The installed capacity would be considered excess
by some, but serves my goals. First, I can make it through the very
coldest nights without inefficient electric resistance auxillary heat
(though that was initially used and is in standby). Loss of an HPs
capacity can be covered by the others, till a convenient service time.
And I expect that not working too hard, HP life will be extended. I
believe the efficiency is not affected much by greater capacity.

Realize the $ cost of a DIY mini split is less than half the cost of
hiring the job. A replacement with all the support parts in place,
would be even less $ or time.

After quite a few years waiting for a Nyle Geyser water heater HP
attachment to be available, I give up and am going another way.
The cost of my propane water heating keeps rising, meanwhile I
gave the PoCo some 5000 kWh of energy at April true up. I am
tired of water heaters that rust through in a few years. And my
propane burner recently quit, the flame detector failed to keep it
lit. I cleaned it for now, actually have a backup on the shelf, but
better to use my surplus kWh and stop buying any propane.

So I bought a Stainless Steel tank, lifetime tank electric Water Heater.
It might actually require more than my kWh surplus, better that than
giving kWh away and buying propane. Once it is in service, I will
again be investigating ways to couple in an HP. I doubt the HP WHs
come in SS, and I do not trust them long term.

The WH could be regarded as a small energy storage unit, something
my Net Metering arrangement does not have. So other ways of
increasing efficiency might be possible. Remember my array
inverters run in clipping up to 8 hours on sunny days. Pulling some
water heating DC direct from the array could pull the inverters out of
clipping, getting an increased total energy for that time. If that worked,
could even throw up a few more south facing panels just for helping
heat water.

Working near the inverters a couple days ago, it was a pleasure to
note how well they performed under lighter clouding. Inverters would
run at near full power, to near half if the clouds got more severe. This
all day long, turned in 100 kWh for the day. My day record for the
15 kW plant is 157 kWh. I must point out this is possible with panels
becoming so cheap, catching maximum sun at all hours. Trackers
were used to try and do this when panels were far more expensive,
but a tracker cannot compensate this way for clouds.

Bruce Roe

[DanS26]

Here is what the Nyle rep says........

"It is (disappointing), feel free to let your congressmen know that you would like the DOE to qualify heat pumps, sold without storage, to qualify for energy star. If the DOE makes this change we would work on releasing a residential heat pump again."

[DanS26]

Hey Bruce,

Just got word from a Nyle representative that the current DOE regulations will preclude them from releasing a residential heat pump water heater addon device for the foreseeable future. This is very disappointing since they were in development of replacement unit for the Geyser RO.

Not sure why or what is causing the problems with the DOE regulations.

I installed the Geyser RO in 2012 and run it only in the daytime during solar production. I replaced a relay switch about 5 years ago and bypassed a faulty high pressure safety switch last year. I use a current transformer to monitor the compressor amp draw to now monitor safe operation in lew of the safety switch. Not recommended unless you like to monitor things. It just keeps chugging along and produces all the hot water I need for pennies a day. I asked Nyle if they would provide a supply of off the shelf spare parts since they apparently will not be needing them in the future. Somewhat complicated to work on since it is a closed system that most DIY'ers would not tackle.

[Rade]

I am not a lawyer but RI law is available on line. Some great night time reading for Rhode Island Net Metering:

R.I. Gen. Laws § 39-26.4-3

My reading of it: 12 month annual true up recommended, but not required. It is up to the specific utility to define the exact plan. Blah, blah, blah, if you have too many credits they won't pay/credit you more than 25% over your actual annual usage.

One interesting line give the utility a way to change the plan with enough cause.

"Should there be a material change in circumstances at the eligible net-metering system site or associated accounts during the twelve-month (12) period, the estimates and credits may be adjusted by the electric distribution company during the reconciliation period."

This is pretty dense reading and really should be interpreted by the net metering liaison for your POCO.

I find it hard to believe a POCO can't give a customer the hard facts on how they will or won't be billed since somebody has to write the program to generate the bills. How do you write a program without having a spec?

Just my 2cents.

Thanks for the information! Did not think to look at the RI statutes. I will look further into it. Rade

[J.P.M.]

Dave: Add my $0.02: Seems to me that POCO policies aren't written to be understandable by POCO customers - just the opposite - they're written in such a way so as to keep the POCO out of a lawsuit as well as be a roadblock to understanding.

Further, it also seems to me that any POCO's rules as they apply to net metering in particular are always written so as to be as difficult to understand as possible and also usually so that they favor the POCO in cases where interpretation is necessary.

Don't forget that PV and other distributed generation methods are a real PITA for POCOs.
Pardon the rhetorical question but If so, what incentive do they (the POCOs) have to be one iota more cooperative to PV system owners than they are required to be by law ? No surprises there.

[oregon_phil]

I am not a lawyer but RI law is available on line. Some great night time reading for Rhode Island Net Metering:

R.I. Gen. Laws § 39-26.4-3

My reading of it: 12 month annual true up recommended, but not required. It is up to the specific utility to define the exact plan. Blah, blah, blah, if you have too many credits they won't pay/credit you more than 25% over your actual annual usage.

One interesting line give the utility a way to change the plan with enough cause.

"Should there be a material change in circumstances at the eligible net-metering system site or associated accounts during the twelve-month (12) period, the estimates and credits may be adjusted by the electric distribution company during the reconciliation period."

This is pretty dense reading and really should be interpreted by the net metering liaison for your POCO.

I find it hard to believe a POCO can't give a customer the hard facts on how they will or won't be billed since somebody has to write the program to generate the bills. How do you write a program without having a spec?

Just my 2cents.