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EPOS: European Plate Observing System

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Last update: September 03, 2021, at 09:32 AM
Version: pmwiki-2.2.126



Department of Earth Science
 Allé gt. 41, N-5007 Bergen, Norway  
0.2   Added more information and photos. 1 Apr, 2020 OM OM  
0.1 Draft - for comments - 19 Aug, 2018 OM OM -


JNE/Ulla, new solar panel August 2018.


1.1 Solar panel

  • Supplier: Sunwind / Gylling
  • Model Max Power 160 watt, supplier p/n: 102560
  • Dimensions (W x D x H): 1470 x 660 x 50 mm, weight: 12.5 kg. Installed in metal frame for protection.
  • Cell type: Mono-crystaline
  • Power: 160 watt
  • Warranty: 30 years
  • Construction: Hardened glass TPT
  • Max charge current: 8,88 A

Specifications, from this source:

1.2 Shunt resistor and analog panel instrument for showing charging current

  • Shunt:
    • Elfa Distrelec p/n: 176-38-422
    • 15A/50mV - Shunt 15 A, 50 mV class 1.0, Fujita
    • Since solar panel max charging current is 8.88 A, it would have been better to use 10A shunt (Elfa p/n: 176-38-414). Consider replacement.
  • Meter:

1.3 Regulator

1.4 El. panel

Click to see large version.

Liberg el. panel, from 2019 photo album. Click to enlarge. Left meter shows current from wind generator, full scale 30 A. Right meter shows solar panel current, with full scale 15 A. (Labels attached after photo was taken.)

1.5 Battery bank --- identical for both stations (JNE/Ulla and JNW/Liberg)

Click to enlarge.

Liberg battery bank, from 2019 photo album.

3 ea installed (replacement) in 2016
Click to enlarge.

EXIDE Technologies AS ES1300 GEL battery. Click to enlarge.

  • 3 ea 120 Ah / 12V, wired in parallel.
  • Manufacturer: Sønnak - Exide Technologies
  • Model: ES1300 GEL
  • Data sheet
  • Weight: 38.7 kg
  • Dimensions (L x W x H): 349 x 175 x 290 mm
  • Supplier: EXIDE Technologies AS
  • Installed: April 2016
  • NOTE: Wind generator regulator feeds these batteries, in parallel with solar regulator.
Added 2 ea (for each station) new batteries in 2019

Ritar model DG12-200 --- 12 V, 200 Ah / C20

1.6 Solar panel cables

6mm2 cables used.

For future reference:


North orientation is required for three reasons:

  1. Instrument cabins should have one side facing South, in order to maximize solar panel energy contribution.
  2. Seismometer requires North orientation within +/- 3 degrees.
  3. Geodetic GNSS antenna requires North orientation within +/- 3 degrees.

There are different ways in establishing North reference line.

2.1 Using handheld GPS

A North reference line can be established by walking due South some hundred meters from a starting point, by keeping longitude (E/W) GPS coordinate fixed while walking.

2.2 Tracking Sun's position

Determine at what time the sun is due South at a particular location, and use the shadow cast by a pole as reference line. According to web app SunCalc:,-8.2934,10/2018.07.18/08:52 - the sun should be due South at 14:40 local (Norwegian) time at Ulla location, on 18 July 2018. Check : Since Ulla is at longitude 8.29242W, and the sun moves 1/4 degrees per minute (hence 1/4 degree * 60 * 24 = 360 degrees per day), it should be due South (8.29242 / 0.25) 33 minutes later, compared to zenith time at the prime meridian. The same web app tells that seen from Greenwich-observatory, the zenith time is 14:07 Norwegian time (two hours after UTC) on the same date -- that is (14:40 - 14:07) 33 minutes earlier then at Ulla zenith time --- just as expected (a detail: geodetic zero meridian on a geocentric reference ellipsoid -- which is what GPS positioning yields --- is 102.5 meters east of Greenwich meridian).

Link to online apps that might help for North orientation:

2.3 Using FOG = fiber optic gyro, model "CDL TOGS-S", made by Teledyne Marine

We used this instrument to establish the "official" North referance. NOTE: FOG heading accuracy is 1.53° RMS at 71°N latitude (JNE / Ulla coordinates: 70.98842N, 8.29242W) - see below.

  • Model: CDL TOGS-S
  • Data sheet: Link (PDF)
  • Manufacturer: Teledyne Marine
  • Heading accuracy: 0.5° secant latitude RMS
  • Secant of latitude means inverse of the cosine of latitude.
Click to visit product web page.

CTBTO/IMS uses this optical gyro. However, it has a specified operating latitude of ± 70° (ref datasheet). All new EPOS-N/SVALBARD stations will be above 76 deg N - how will the gyro operate at such latitudes?

Perhaps this limitation is a consequence of the physics behind optical gyros, which then has to be studied in more detail.

Model CDL-TOGS is intended for subsea use, with 3000 meter depth rating in basic version. Presumably such features drives price upwards. Aren't there any optical gyros for surface use, that could be suitable - and much less expensive? We have to search ...

When heading accuracy of gyros is specified to be "0.5° secant latitude" - which is the case for "CDL TOGS-S" - ref datasheet - it means it will be accurate to 0.5 degrees at the equator, and show reduced accuracy according to the secant of latitude, which is inverse of the cosine of latitude.

A plot of heading accuracy vs. latitude for this model, with some geographic locations added:

2.4 Comparison of two North orientation methods

A North reference line can be established by walking due South some hundred meters from a starting point, by keeping longitude (E/W) GPS coordinate fixed while walking. This North reference line was marked with black on sensor pit concrete. Compared to "official" North line, measured by Teledyne Marine Fiber-optic gyro (FOG) model CDL-TOGS-S --- marked with red on concrete ---- there is a difference of 2.49 ° counter-clock wise. NOTE: FOG heading accuracy is 1.53° RMS at 71°N latitude (JNE / Ulla coordinates: 70.98842N, 8.29242W). Also, the photo used for the illustration might distort lines slightly, depending on viewing angle from camera lens. This means that handheld GPS method is most likely acceptable, in order to get North reference for similar shallow sensor pits. (We have some deep sensor pits, and some sensors located inside buildings, where the FOG is required.)

Click to enlarge.

JNE/Ulla seismometer sensor pit. Photos shows GPS North reference line (black, to the left) and multiple FOG north reference lines (red). Seismometer is Trillium 120QA. Click to enlarge.

We had a theory that sensor pit and instrument cabin was North oriented when they were built and installed in 1984 and 1989, respectively. In 1984, the magnetic declination at JNE/Ulla coordinates (70.98842N, 8.29242W) was 16.33 deg W (ref:, selecting IGRF12 model for magnetic variation). And it seems sensor pit and old instrument cabin was oriented towards compass North, without correction for magnetic declination. Ref attachment.

2.5 Current solar panel azimuth angle - JNE/Ulla

Click to enlarge.

Current solar panel azimuth. Its position is better then the alternate location. Click to enlarge.


Plot showing sun position, seen fram sensor site JNE/Ulla, at various dates:

Solar panels should from this figure have 40 degree vertical angle - ref figure below.


3.1 Length of supporting struts for solar panel frame

Assuming 40 degree vertical angle, how long should these struts be? ("Strut" = "Stag")

Click to open PDF version.

Click for PDF version.


The new instrument cabin at JNE/Ulla was installed so as to utilize existing concrete blocks for anchoring the cabin with steel wire to the ground. The azimuth angle of the cabin is thus not optimal - it would of course be best of one side, where the solar panel is mounted, faced due South. We are interested in estimating the loss in energy production that current azimuth means, compared to the optimal azimuth, with solar panel facing South.

UiB/GEO software to calculate daily energy production from solar panels, over one year, has these features:

  • Arbitrary number of solar panels, each having arbitrary wattage, azimuth and tilt.
  • Arbitrary location on Earth.
  • All these parameters specified in separate parameter file that can easily be modified.
  • Assumption: No clouds or terrain obstructions. (Software can be modified to account for these factors, without too much effort.)

This software is used to make diagram below (link to Excel file). The flat green line represents the daily energy requirement of the instrumentation, given by the power times 24 hours:

17.4 Watt * 24 h = 417.6 Watt*Hours/day

Comments to the diagram:

  1. Solar panel has 40 degree elevation referred to the horizon (ref section above). This equals 50 degree tilt, measured with reference to vertical axis (used in the software).
  2. The gray line is the difference between optimal azimuth (due South) and the actual. It can be seen that difference is largest in certain spring and autumn periods. During the summer, the difference is fairly small.
  3. The purpose of the solar panel is to supplement energy production from wind generator, during summer when the wind can be absent for extended periods of time, as shown on wind generator simulation based on actual weather data. We consider the time between 1 June and 1 September to be critical in this regard. And in this time frame, the difference between optimal and actual panel azimuth is not very great.
  4. Yellow curve shows output from panel in "winter" configuration, with 20 deg angle to the horizon (equals 70 deg tilt). Yes, there would be an increased energy production in spring and autumn - but that would not be required, as there is ample wind during these periods. So no need to have winter/summer adjustment on the panel. Dark blue curve shows difference between winter and summer angle.
Click to enlarge.

Click to enlarge.

4.1 Energy budget, JNE/Ulla

Click to enlarge.

Click to enlarge.


We consider using solar panels of brand "MAX POWER", from distributor SunWind (Gylling):

Prospective models:

  1. Max Power 100 watt, Dimensions (W x D x H): 1195 x 540 x 35 mm, weight: 7.5 kg
    • Bracket, adjustable, for installation of solar panels: Max Power 50 watt, 75 watt, and 100 watt:
      "Sort utførelse, pulverlakkert og produsert i galvanisert stål for ekstreme vindstyrker."
  2. Max Power 160 watt, dimensions (W x D x H): 1470 x 660 x 50 mm, weight: 12.5 kg
    • Bracket, adjustable, for Max Power 160 watt:
      "Sort utførelse, pulverlakkert og produsert i galvanisert stål for ekstreme vindstyrker."
  3. Max Power 185 watt, dimensions (W x D x H): 1482 x 676 x 35 mm, weight: 11.5 kg
    • (Does not look like SunWind had bracket for this model, perhaps bracket for 160 Watts panel covers 185 Watt panel too - must check.)

We select MAXPOWER 160 Watt, since frame is stronger than that 185 Watt version.


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Page last modified on April 30, 2020, at 11:49 AM
Electronics workshop
Department of Earth Science - University of Bergen