Building Reserve and Using KWH

[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

[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]

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

[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]

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

[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]

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

[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.