Wrote a Victron to Prometheus exporter. Now starting to get data from the controller. Peak output from the panel was 38 W.
Recorded a timelapse of the sun on the target area. The Hero 7 records timelapse at 2 Hz and stores at 30 FPS, so 1s = 15s. The area is totally in shade by 10:27 in = 157 minutes after starting. Stopped at 15:01, 164m long, so in shade at 14:54. The sun is at 223 deg / 20 deg at that time, so the nearby buildings are at 20 deg.
Printed a Victron BlueSolar to DIN adapter. Took two tries as the Victron mount isn’t flat.
Made an adapter for the Raspberry Pi header that supplies power and has a voltage divider to make the 5 V VE.Direct connection work with the 3.3 V Raspberry Pi.
Used the extra ports on the Raspberry Pi 4. Enabled by adding
dtoverlay=uart0 dtoverlay=uart1 dtoverlay=uart2 dtoverlay=uart3 dtoverlay=uart4 dtoverlay=uart5
/boot/firmware/config.txt. This creates
/dev/ttyAMA0 through to
ttyAMA4 didn’t work initially as the pin had the wrong pinmux set. This can be fixed by running:
sudo raspi-gpio set 13 a4 pn
Got most of a day’s worth of charge. The day was cloudy with good amounts of sun. Got around 100 Wh of generation out of the panel which charged the battery about by 50 to 70 %.
Wired a relay and the fall back mains supply. The relay switches to mains fast enough, but the DC ready signal from the mains doesn’t decay fast enough causing the Pi to reset.
According to the Sonoff switch, the system pulls 8 W. On 12 V this is 4.3 W.
Wrote a VE.Direct to Prometheus and MQTT exporter. Integrated with Home Assistant, works well.
Printed the corner pieces for the stand and assembled. 11.5 mm U section aluminium for the posts. Designed for 28° which is good for winter here.
Changed the power swichover relay to be driven by the Pi, and did a quick hack that checks the battery state every 10 minutes and switches using hysteresis.
powersel, added monitoring, and set the switchover values to their final values. Still runs as root.
Added a udev rule to give
gpio access to the pins, and made
powersel use that group.
Set up backups using http://rclone.org/ to https://www.backblaze.com/b2/ on
Got a first full day of OK sunshine. The switch over worked correctly and the system ran on solar or stored energy for 14h.
- Move the panel into the final location
- Run the wires through the window and put the server in the final location
- Publish the
Ideally the outcome includes turning off the existing NAS. I have a solution for video, but not audio to Android.
2020-11-05 74 Wh 2020-11-06 39 Wh 2020-11-07 91 Wh 2020-11-08 65 Wh
Total of 269 Wh or 7c of electricity. 56 % of what’s needed to run the server.
avg_over_time(victron_ppv_watt[16h])*16 gives the total number of Wh over a day.
On 2020-11-09, the battery was fully charged and some generation was dropped:
2.08 W with
hdmi_blanking=2 dtparam=pwr_led_trigger=none dtparam=pwr_led_activelow=off dtparam=audio=off dtoverlay=disable-wifi dtoverlay=disable-bt
With a slope of 60 deg, produces 54 kWh/m2/month in December, which is ~1.8 kWh/d, or 75 W/m2.
December is 30 % of the peak output.
Taking a Victron BlueSolar 90 W @ 119 CHF with area of 0.52 m2. Solar irradiance is ~1120 W/m2, so the panel is 15 % efficient.
So a 90 W panel can supply 5.9 W for 24 H in December.
To check, a 90 kW (note: 1000x) system gives 4278 kWh in December and 13853 in July at 37 deg, which is 6.5 W continious in Dec and 19.2 (3x) in July.
At 60 deg, this is 4825 kWh in December, or 6.7 W. 2 d of storage is 320 Wh, 26 Ah @ 12 V, or 53 Ah @ 12 V with 50 % cycling.
Appendix: unsorted links
Horizontal = 1.31 to 5.64 kWh/m^2/day = ~39 to 169 kWh/m^2/month
Horizontal - 30 to 200 kWh/m^2/month
Actual solar - 32 to 177 kWh/m^2/month
Panel: 545 x 668 x 25mm series 4a
So sin 28 deg = O/H, O = 313,
cos 28 deg = A/H, A = 589.