15 kw net metering array

[SunEagle]

Of course it is zoned AG. There are horses on the other side of the fence, but they eat too
little & leave way too much behind. Then there are the deer....

It must be tough living out in the country. Wish I could.

Well if I haven't said it yet your pv system looks real nice and I wish you a lot of luck with it.

[bonaire]

Bruce, three acres is a lot, I've got about 2 to mow. About 2 gallons.

Here's an upcoming company with electric mowers using Li-ion.

http://www.meangreenproducts.com/products.html

[bcroe]

Mowing

Bruce, three acres is a lot, I've got about 2 to mow. About 2 gallons.
Here's an upcoming company with electric mowers using Li-ion.
http://www.meangreenproducts.com/products.html

Bonaire,
Its 5 acres, but only about 4 have grass to mow. I don't think there is money left
to buy a powerful electric mower. 54" cut sometimes takes all of the 27 hp to get
through. But at 9 mph, can get done in 2 hours, my neighbor calls it "marathon
mowing". The same AWD rig blows snow in winter, an essential thing in the
country.

Bruce Roe

[bcroe]

15 KW Solar Array Operational Report

After some weeks of operation, i am getting some
actual numbers. Ultimately the goal is 23,000 KWH
a year collected, or 63 KWH a day. In recent days,
with serious clouds every afternoon, its running some
15% ahead of the goal. Some days 45 KWH, some
near 100 KWH. I missed out on the most optimum days
around the beginning of summer, which should have
done quite a bit better. Esp, June & July due to the
AUTHORITIES failing to get the NET METER installed
when agreed. Will have to estimate that production,
measure it for real next year. I know, it will drop in winter.

At this season it produces energy some 14 hours a day.
The extreme tails give out some hundreds of watts, when
the sun isn't directly hitting the panels. Soon as there is
direct sun, it does kilowatts. It takes 16 KW solar DC to
produce the inverter max of 15 KW AC, after DC copper and
inverter losses. With 18 KW of panels, there is some
clipping anywhere near solar noon, if there isn't a cloud
in the way.

If the sun is completely blocked, output could be 5% to
15%, depending on just how dark it is. That includes rain.

Generally, everything was planned over some months, to
fit the existing space, facilities & needs as much as
possible. All the operating parameters so far are pretty much
where they were expected to be.

With the panels being over 500' from the house and the NET
METER, transmission losses are part of the design. A 600'
loop of 4 gauge carrying 250 volt at 60 amps AC (15 KW)
can exceed 3% loss. I knew that, but it was already in place
for free, and no where near overloaded. However the line
voltage here is rather high, 120V/240V all the time. Add 9V
drop in my loop, and the inverters are seeing 250V at peak.
The worry is, they are nominally programmed to trip out at
264V (hasn't happened yet).

My question is, what to do if they start doing high line voltage
trip out? It won't hurt the inverters; they are designed to
operate up to 277V nominal. Perhaps the trip point could
be programmed a bit higher; anybody know how adjust a
Fronius?

Failing that, another way to get some margin is lower the
voltage to the inverters a bit with an AUTOTRANSFORMER.
Just a 5 or 10 volt shift down (at the full 60A) ought to be
enough. Pretty clumsy way, just in case all else fails.

It will take a couple years to run this science project out.

Bruce Roe

[Bobodude]

Nice system Bcroe. My only comment is on the transmission cable from the panels to the out building. If I understand you right it's 600' with #4 cu? Wow, that is nearing a wopping 8.27 % voltage loss at full load! I know it was free but that will be a loss forever! I used 4/0 aluminum for my 70' run from panels to inverter. And it was free too. Wish you the best of luck my friend.

[bcroe]

Losses

Nice system Bcroe. My only comment is on the transmission cable from the panels to the out building. If I understand you right it's 600' with #4 cu? Wow, that is nearing a wopping 8.27 % voltage loss at full load! I know it was free but that will be a loss forever! I used 4/0 aluminum for my 70' run from panels to inverter. And it was free too. Wish you the best of luck my friend.

Using oversized wire is great, esp if you get a good deal. But not having
to dig the trench or lay the wire is a big trade off. All the trade offs were
known at the beginning; if I bring in more energy than I need, it will be
wasted on a Tier 2 grid tie. The actual resistance of the 4 gauge loop
was measured in advance with a Kelvin connection.

Actually the LOOP is 600', 300' each way. 255V @59A gives me a loss
of 9V across the 0.15 ohms, or 3.5%. Since that only occurs at peak
power, its a good trade off verses digging up and replacing all that wire.
Keep in mind there are DC copper losses of 1.4% from the panels and
inverter losses of 4.5%. So trying to beat 1% out of the total 9% is
really into diminishing returns. Copper loss % drop linearly as solar
energy decreases; inverter loses stay in the area of 4.5%. In the long
run, if I cancel out my house energy bills, the losses don't matter. I
still need to install the additional R50 insulation this fall, to adjust the
consumption end.

Still bringing in 90+ KWH (inverter output) every sunny day this month.
Bruce Roe