# Wind, solar, storage and back-up system designer - Page 4

Posted by Scottish Scientist on July 7, 2019, 2:26 am

On Saturday, 6 July 2019 22:12:24 UTC+1, ads  wrote:

Hi ads and thank for being the first to reply to my post.

That's why I have included "SOLAR" to my

Wind, solar, storage and back-up system designer for 100% renewable energy
grids and microgrids with 24/7/52 power-on-demand!
https://scottishscientist.wordpress.com/2017/07/14/wind-storage-and-back-up
-system-designer

I also say in that blog post, which you obviously haven't bothered to look

"The energy generation percentages from wind and solar power can be adjuste
d, either directly using knowledge of local wind and solar capacity factors
, or, according to the latitude of the system using a simplistic formula wh
ich assumes that wind power generators are preferred near the poles and sol
ar power generators are preferred near the equator.

Diagram of the Earth explaining what latitude is.

Latitude
The latitude of a place on the Earth can be specified as a number of degree
s from
-90, representing the South Pole,
to 0, representing the Equator,
to 90, representing the North Pole."

So I clearly am considering the rest of the world.

Posted by ads on July 7, 2019, 9:50 pm

On Sat, 6 Jul 2019 19:26:32 -0700 (PDT), Scottish Scientist

calculations are at the wrong end of the scale - you are making the
assumption the EVERYONE who sees your post will be
government/corporate-related and funded.

Note that this group's name ends in "homepower", implying *small
scale* alternate energy, with no more than roof-sized solar arrays and
1KW or smaller wind generators up probably less than 50 feet - not
megawatt generators up 80 meters.

Posted by Jim Wilkins on July 7, 2019, 11:01 pm

Latitude is a measure that divides exactly into nautical miles, 60 per
degree, which is one reason why metric never caught on for navigation.
The other is because metric was defined incorrectly in the 1790's. The
Earth's circumference was meant to be 40,000 km but it isn't, by 75 km
around the equator and 8 km around the poles.

The solar system installers around here have zero interest in systems
as small as mine, and I suspect yours. They require all the
electrician's labor of larger systems without the profit.

Posted by ads on July 8, 2019, 2:44 am
On Sun, 7 Jul 2019 19:01:51 -0400, "Jim Wilkins"

My small system (420AH of 12 volt AGM batteries, max of 1600 watts
solar - not all installed) was a learning project with a design goal:
I wanted a "solar generator" that could provide "Wait until daylight"
power for essentials during the too frequent commercial power outages
we have.  They're rarely long: 16 hours one July after a thunderstorm
with some 70MPH+ winds took down a lot of lines; 12 hours one December
when the county had 7 to 12 inches of snow - in an area that rarely
experiences more than 3 inches.

Depending on the season, we get 8 to 24 hours of limited power -
running the blower for the central heat takes it to the low end as
does running a small (5000BTU) window A/C for a few hours on the worst
summer days.  Spring and fall, we power the fridge, a few LEDs, etc.,
and we're closer to 24 hours - with variations for using/charging
laptops, tablets, cell phones.

With a 2000 watt pure sine wave inverter, the solar generator mets my
design goal of running fridge, freezer, phone, internet and a few LED
lights long enough that I don't need to be out in a thunderstorm or in
the dark in 30F and snow trying to get a gasoline generator started.

There are several sources that offer 'silent generators', but none of
them met my requirements.  When I designed the system, the closest was
the Yeti 1250 but it doesn't have the battery AH or the inverter watts
to run all that might be on at the same time - and you're limited to
using two very small solar panels for solar charging - for a total of
\$000 when I designed my system.

My system's cost is now up to around \$700, but that includes 420AH of
AGM batteries as primary power, another 240AH of AGMs as
communications power, the 2000 watt pure sine wave (PSW) inverter for
the generator transfer switch, a backup 2000 watt PSW inverter, a 500
watt PSW inverter for the communications equipment (two routers, 24
port switch, etc.), some system specific test equipment (clamp on DC
ammeter) and tools(MC4 crimp tool), lots of 4 gauge copper wire,
serious DC breakers from 20 to 200 amps, 1600 watts of solar panels
and assorted bits and pieces that are in a multi-page Word file that I
used to document the process and track all the pieces.

And then there are the spreadsheets that I put together over time to
track how much power a "100 watt" or "250 watt" solar panel could
actually be expected to deliver (not much better than 75 watts for the
100's but I have some Jinko 250's that I've measured at 235 watts in
backyard sun - so some do work better than others) and how much
battery AH is required to support which appliances for how many hours,
including the inefficiencies in the inverters and limiting the battery
discharge to 50% to extend their useful life.  If I had to piece
things together from old car batteries and limit the discharge to only
10 or 20%, I have a spreadsheet for that ;-)

This is what happens when you have a retired shade tree engineer with
time on his hands and a few extra dollars from selling his first novel
as a Kindle ebook: https://www.amazon.com/dp/B01LVU5ILA

Posted by Scottish Scientist on July 7, 2019, 11:34 pm
On Sunday, 7 July 2019 22:50:11 UTC+1, ads  wrote:

my designer page calculates for ALL scales of 100% renewable energy systems
.

Didn't you read my comment to Jim where I used the designer web-page to des
ign him a wee 4KWh per day system, for his power outages, that needs only a
100 Watt back-up generator?

100W! That's really small. You can't buy a generator that small, as far as
I know, so you'd have to buy the smallest generator you could get - maybe a
portable 900 Watt generator and run it as slow as it will go and even then
it will be more than you need for such a small system.

Here's my comment to Jim again for the record.

The Wind, solar, storage and back-up system designer will help you to desig
n a system to generate any maximum of KWh a day that you need. Just beware
that in the Off-grid daily usage focus table the daily usage (max) is a max
imum figure.

You just need to adjust the values in the tables to suit. The tables are fu

There's the off-grid table for 4KWh maximum daily usage and 8% solar capaci
ty factor.
http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calc
ulator.htm?usage=4&units=kw&spc0&scf=8#off

Here's the text configuration page for row D.

Wind, solar, storage and back-up system designer
Configuration text page.

Daily Usage of Energy: 4 KWh
Solar Power Capacity: 2.64 KW
Solar Capacity Factor: 8%
Solar energy per day (average): 5.07 KWh
Storage Energy Capacity: 4.48 KWh
Back-up power: 0.093 KW

So 3KW of solar panels, 4 of your 12V105Ah batteries and a 100 Watt generat
or if you can find one that small, would do that, if that's all you need to
get you through your power outages?

ee if you like those numbers better.

Breaks my heart to design you a system that generates so little power. ;) L
OL.