Building Reserve and Using KWH

+1. Great job Bruce.

We passed the reset date, once again without buying any KWH for the year. I did burn
down some surplus with the car shop resistance heater, mostly left its propane heater
off. I would really like to find time to put a somewhat larger mini split there, -25F rating
to keep things more comfortable year round. The house could use another for the worst
of winter (set a new low record this year). The bi directional disc KWH meter is doing
well in indicating day by day surplus down to the reset.

For the first years I noted one inverter always produced one or two more KWH a day than
the other. Observation showed that is was because of the shadows at day extremes from
a pair of trees. Those trees were trimmed in 2014, but had regrown worse (from a PV
perspective) than ever. With prospects getting worse, they finally got the axe about a
year ago. Since then the OTHER inverter has been out producing a KWH or 2, which
means the system is producing several more KWH a day.

There is the possibility of saving nearly 1000 KWH a year losses by replacing the rest of
the 4 gauge wire out to the inverter building, with 1/0. I now have a trencher to ease
getting this done, but it is not getting much priority. More likely is to start upgrading the
early panel mounts to the same standards of the latest, but that will take quite a while.
If the HVAC plant reaches its final operational status this year, I might start in on the
optional upgrade stuff.

The PoCo now asks me to pay them $25 a shot to take my old WORKING appliances.
Of course I can just break them down to the scrap metal and get paid for it, like previous
decades. Bruce Roe

There is so much smoke drifting from other parts of the continent, its costing me one
or two dozen KWH a day. That is about the limit of our grief, while others suffer one
disaster after another.

Meantime the car shop is well along in the installation of a 16,000 BTU mini-split
heat pump, pictures soon. This RLS3H has a -25F degree operational capability,
achieved with some internal supplemental resistive heat at the very lowest outside
temps. This luxury will attempt to keep inside temps at least 40 F year around, as
opposed to just being really cold in Feb. This will make quick jobs (oil change) easy
and a quick blast from the propane furnace will get me 65 F for a transmission
overhaul. The occasional, automatic use of some resistance heat at extreme lows
is a huge improvement over using it continuously and manually.

There are some summer days when a little AC will be nice too.

The above can be supplemented with a 7.5 KW electric heater while working, if my
KWH reserve is generous. The low temp Minis in the house are giving me a big
KWH saving to make this addition still completely solar powered.

The shop is 1080 sq ft, with basic level insulation. Meantime I am considering
burying a 500 foot loop of 1/0 out to my inverters, to preserve several percent
of my generation. The question is, if to bury 18 inches deep in conduit, or
24 inches deep with direct burial wire? Bruce Roe

I didn't hear/read of any big fires west or NW of you, but I'm curious, how do you do the estimating of losses due to atmospheric turbidity/smoke ?

Its all a guess of course. I can run at capacity even with very light clouds, an ideal sunny
day may do 158 KWH. When our weather person says no clouds, but smoke from Canada
is causing the haze, I credit the 135-140 KWH lessor day production to the smoke.

I see a heat pump automatic switch over to cooling today, humidity is dripping out the other
(inside unit) drain. Bruce Roe

As Bruce mentioned, I have seen a number of weather forecasts that show the smoke from Canadian fires drifting South on the satellite radar images..

Yea, it is. And I don't have data or literature to comment one way or the other, so I'll not do so.

NOMB or concern, but to be clear, your inverters may be running to capacity but because of your less than optimal array orientations the panel portion of your system is not. If you had ~ 25-26 STC kW of south facing panels at a 45 deg. tilt, instead of ~ 35 STC kW you do have spread in varying orientations as you have, you'd produce about the same output on a sunny May day. You'd probably need bigger/more inverter capacity and that would cost a bit, but I'd wager you'd save a lot more than that cost by having only about 75 % as much STC kW in panels to pay for. But I do appreciate the reasons behind what your doing and the fun you're having.

Also, humidity is the amount of water vapor in the atmosphere or in a gas. What you see is condensed water vapor, or simply condensate.

Respectfully,

PV15May19.png

Will try to say condensate next time.

That is fine for the one fully sunny day on this chart of my recent daily outputs. Better to design a PV system
that does well every day, sunny or not. A close look at my actual numbers reveals more output on EVERY
day than a pure south facing array. My original south facing array would have much deeper valleys than this
chart. Just so any comparisons make sense, there needs to be a common element. Since I cannot change
my 15 KW inverter capacity, I am declaring that the fixed point. It may be used with a DC/AC ratio. Bruce Roe

Indeed it is the system as a whole that is optimized. It is easy for someone to cherry pick the individual components output and try to infer that your system is suboptimal.

Oh, critical analysis is welcomed. If I can not answer that, its time to go back to the drawing
board. Have had to explain that to some new guys on the job. I have stories....
Bruce Roe

Ampster, if you think I'm cherry picking Bruce's array, you're exhibiting an example of your ignorance of the basics of PV and solar energy in general, and I have no inclination to instruct you.

Bruce's array is optimized for what his goals and intentions are. Big AMEN on that. I share more than a bit of what appear to be his eccentricities.

Bruce and I do not share all opinions about the best way to apply solar energy.

IMO, Bruce's array is most likely not something that a knowledgeable PV designer would come up with in most any common semirural, grid tie application if cost effectiveness or optimal use of materials or resources were design goals.

You want to be helpful, buy a decent textbook and find out what solar energy is really all about before you criticize and misconstrue and attempt to twist what I write. You might be able to contribute something technical rather than repeat what you read or heard someplace that fits your view of things. You also might begin to understand some of what Bruce and I respectfully disagree about rather than more of the same blather that doesn't contribute much of anything to the discourse except that you agree with someone and disagree with someone else for unspecified reasons.

I agree with Bruce because he is optimizing his system. Perhaps you might want to try to attack the argument instead of attacking someone else.

You guys ought to just stick to the facts. Bruce Roe

The facts are that large scale solar farms average a DC to AC ratio of 1:25 to 1.That number has been increasing over the years. I don't recall your AC to DC ratio but I believe it is greater than 1 to 1.

Perhaps the misunderstanding is whether we are talking about optimizing the array or optimizing the entire system. I won't speak for J.P.M. but he consistently refers to arrays (the panels) and I interpret your discussion on this thread to mean the entire system, including the panels, inverters and racking.
EDIT
As you point out in the following post, most commercial solar farms are described by their AC rating. My point in the above is that an array centric methodology is not always used by professionals to optimize systems.

The first results are in for the attempt to expand commercial solar in IL. Those I
reviewed were in the 2MW to 20MW (AC rating) range. Of 900 project submissions,
100 were approved, I do not yet know more details of the approval process. I do not
yet know of anything close by, but many of us were not happy to see suggestions of
here putting them on some of the best farm land, in direct violation of existing zoning
Comprehensive Plans, by some sort of slight of hand. And I was additionally unhappy
to see proposals where clouds and snow are so prominent. Bruce Roe