Nordintown Blog

Rubbish musings, projects and hackerings from Nordin

Solar PV, Aberdeen and me - Update 3

May 062018

I am currenly holidaying in sunny Gran Canaria and whilst dozing by the pool, I caught sight of a bank of solar panels. "Ah" I thought, I have those.

Its also been a while that I last blogged, so I thought I would kill two birds with one diamond laser and post an update. See graph.


It has been up and down with the generation rate but it has surpassed the conservative expectation that the installer gave me. Quite pleasing. The generation estimate was made against the avg Aberdeen sunlight hours, direction of panels, angles etc and the performance tracks  the avergate sunlight hours/day nicely - below, yellow line.


The sunlight hours highs are May followed by August, which appears odd at first (July being the hottest month) until you realise heat and sunlight are not the same thing. It does make me want to investigate all this talk on micro heat-powered Sterling engines I hear so much about. These are dinky blacker-than-black heat traps that expand and contract gasses to drive turbines that generate UnLiMeD POWER!!@%@45£!

At a 60% to 70% efficancy rating, Sterling engines kick solarpanels and their 20% max efficancy off the ballpark. They are more complicated I am given to understand, however the clever dicks are working on the problem and hope to have something investors can overspeculate on soon [1]. When done, we can call China and ask actual ballparks of them - hurrah.



Project Intro: Research and design of self-organising, algae farming, soft robots

Apr 062017

An amateur home-based project to design and evaluate self-organising, algae farming, soft robots.

This is a project started inpersuit of a personal interest in home-grown complete food sources. The notes below for my project log and project substages will be added ad-hoc.

The project itself will take place in 3 phases: (1) Stable Spirulina cultivation and remote monitoring via a conventional self-built monitoring platform, (2) evaluation and improvement of a self-built remote sensing and actuator 'nodes', tethered and water-bound to distribute aeration, inspection and monitoring; and (3) Migration from central controller-based coordination to autonomous, untethered agent-based methods. Succinct project updates will be made on the Research Gate platform whereas informal project notes will be made on the Author's personal blog (


Phase 1: Stable Spirulina cultivation and remote monitoring via a conventional self-built monitoring platform.

1.1 Preparing the culture medium

Chemical ingredients for the cost-efficient RM6 culture medium [1] (Roof, Kaushik and Prasanna 2006) were obtained via various Amazon and eBay supplier sources. Super single phosphate (SSP) was substituted with an alternative inorganic phosphate source Potassium Phosphate due to SSP sourcing problems. Measures of all fertiliser ingredients were made for a 4l liquid volume within a 4.5l demijohn growth vessel, marked GV1:

  • Potassium phosphate 5g,
  • Sodium nitrate 10g,
  • potassium Chloride 3.92g,
  • magnesium sulphate 0.6g,
  • calcium chloride 1.6g,
  • sodium chloride 2g,
  • sodium bicarbonate 32g.

The stated measures of each ingredient were made within 0.5l of dechlorinated local tap water and added to 3.5l within GV1. Any crystallised ingredients were ground to powder form.


Solar PV, Aberdeen and me - Update 1

Sep 082016

The install consisted of 12 BenQ PM096B00 panels, each equipped with a optimiser unit, all tied to s Solaredge SE3680 4Kw Inverter.  The total installed capacity is rated at 3.96KWp or 8.54 KWac. 

Plugging these stats together with the southern angle, plane elevation and shading factors, the Annual Solar PV Yield was predicted via the MCS method and PVsol simulation to be around 3277Kwh per year. Factoring in panel degradation, energy price inflation and the guaranteed FIT tariff (12.03p/kWhr) and export tariff rates (4.85p/kWhr), I am predicted a return of just under 12k over the next 20 year period. The system cost about £6.5k to install with the 20yr kit warranty. O/c this payback is realised over the long term with both the FIT payments as income and cheaper electric bills.

The predicted and actuals over the past month are below: 

Est. Generation Est FIT, Export income & Savings Actual   
Month kWh % of total Month Quarterly
(Running total)
kWh % of Est
Jan 166 2.83% £20.35   10   -
February   166 5.08% £36.52   187  111%
March 304 9.27% £66.67 £123.54 310  102%
April    367 11.21% £80.68   393  107%
May 440 13.43% £96.65   502  112%
June 432 13.19% £94.87 £395.45 482  110%
July 417 12.71% £91.45 £262 Paid from SSE, est. £133 saved on bill 430  103%
August 381 11.63% £83.66   460   -
September 292 8.90% £64.04 £634    
October* 211 6.43% £46.30 est. £230 due from SSE (tbc)    
November 122 3.71% £26.72      
December 53 1.61% £11.56 £719.47    
YEAR 3277 100.00% £719.47 £719.47    


Happily, so far I have generated more per month than the estimated - an average of 108% infact. This can only be a good thing but I have yet to compete the estimated bill savings against reality, which may eat up the extra 8% gain. Only time will tell. (updated Oct 5, 2016) 

Project Intro: Solar PV, Aberdeen and me

Jan 202016


Around January this year, I invited the chaps from AES Solar round to quote me for the installation of solar panels on the roof.

Up to that point I had received a few quotes from other installers, gripped as I was by the impending cut-off date before the tariff dropped. For those that are not aware, many of those opting to install panels do so not just for the green karma (although the true 'greenness' of solar has yet to be totally proven in my eyes) but also for the financial return.  In a nutshell, anyone installing prior to January 13th 2016 is paid at least 12.04p per kWHr returned back to the national grid - the so-called 'Generation Tariff'. You also get an additional export tariff per kWh you export, which is currently 4.85p.  Those who installed Solar panels earlier received much better tariff rates, but this has be offset against the high costs of install back then.

Now or never

Assuming you managed to find a good installer, January 2016 was a good time for PV install. This was primarily down to two reasons:

  1. Hardware was the cheapest it had been due to manufacturing advances etc, and
  2. Tariffs were then due to sharply drop of a cliff by 80%.

Why the drop? well officially the government reasoned that more efficient and affordable panels meant the top-up paid to consumers to 'go green' need not be so attractive. I have since read that a second reason for dropping the tariff was that the uptake was higher than expected which was costing the government rather too much. Whatever the reason, a post-Jan16 install was not going to be quite as lucrative and so if I was ever going to sink some savings into my house in this way, it really was now or never.

The two quotes I had received over xmas all contained recommendations for panels on both roof planes of my house. The maximum size of domestic installation that the government will support via FIT is 4kW, which would on my total roof space. I have SSE facing and NNW facing roof spaces and whilst the NNW plane would get some light at sun rise and sunset, it did not feel great knowing that for most of any given sunny day, the NNE panel array would receive considerably less light (see seasonal sun plots below).   


Summer prediction (End June)


Winter Position (Late December)

The summer sun will reach the north-facing roof, but it will be late in the day when the sun's intensity is much less. It seemed that getting as much sun coverage facing south during those peak hours was preferred but the problem was a lack of southern roof space. The installers I worked with were very accommodating and allowed me to incorporate a 'house addon' in to the array layout. This would be a temporary structure that will accommodate the remaining panels in the beneficial direction. 


 'Lean to' design to accommodate the extra panels.

To proceed with the design, one panel has to be placed on the wall but I was not particularly put off by this. The structure was built, the panels installed and the whole system commissioned 3 days before the cut off date for the old tariff (phew). I will post an update with the predicted earnings/savings some point soon.

Building a Low-pass filter (LPF) for WPSR Tx ( e.g. a Raspberry Pi)

Nov 202015

I found a nice set of guidelines about how to build LPF board for your transmitter. Only if your radio license lets you, I recommend having a go with one of these and a Raspberry pi [0]. 

For the low-pass filter, I am following a PDF guide [1] authored by Revd. George Dobbs (G3RJV).  The kit list is as follows:

  • 3 toroid cores (type FT37-43)
  • 1m enamelled copper wire (AWG tba)
  • 1 Choc box electrical junction box 
  • 1 case mounted BNC connector (male)
  • 2m 50ohm Coax
  • Capacitors (varied) 
  • Stripboard
  • Solder + iron 
  • An online toroid calculator [2] (if I must, and even then only to check)

We have to calculate the windings from the core size, material and desired inductance. Our design calls for 3 coils and 4 caps.

W3NQN's 7 Element standard Value Capacitor low pass filters


Calculating number of N turns required on a Toroid for a given inductance:

N = 10 x SQUARE-ROOT ( L / L10)

N = Number turns.
L = Required inductance (uH).
L10 = Inductance at 10 Turns.

This design can be soldered onto strip board along with the antenna connectors of your choice. For the enclosure, I can recommend a choc-box connector housing from Screwfix (UK)[3] I have a few of these ready for projects and they work very nicely.  If you are very lazy, you can pick up complete LPF filters from [4]. They have a good selection and ship anyplace (also check-out their other kits) 



Space radio: Update 2 - Space TV

Apr 092015

I am not feeling great at all today and so I took a rare sick day from work and oh look, radio.

I needed to avoid spreading the dreaded lurgie and also to recoop from 2-3 nights of horrible sleep. Rather than sitting back and letting Netflix wash over me, I have resolved to finishing my quadrifilar helix (QFH) antenna project in between coughs. A QFH antenna is a 4 part (hence quad) helical receiving antenna design well suited to the capture of APT (Automatic picture transmission) images from orbiting satellites. I want to make something that I can modify for use with both NOAA/ISS APT/SSTV transmissions, which have their downlinks set to 137.500ish and 145.800Mhz respectively.  

John Coppens (ON6JC/LW3HAZ)[2] puts it better than me:

"The QFH is an excellent antenna for satellites, as it receives from 'the entire northen hemisphere', from horizon to horizon, with all the sky in between. Such an antenna cannot have any significant 'gain', as it doesn't have directivity. Such an antenna is not useful for hot spots, as you probably won't have any clients 'in the sky'."

This design [1] looks to be a winner and so I have brought all my parts and tooling together in my study to hammer out something that I can leave connected to an RTL-SDR/Raspi in my loft. I'll take pictures as I go and aim to get it ready for the weekend ISS passes. To achieve this, I need to:

  1. Check the calculations for the two cable loop lengths, spur lengths, height and distance apart using the target wavelength and core thickness [3]
  2. Mark, drill and cut upon my large and small spur pipes using the measurements obtained; and
  3. Solder the wires of correct length to variboard in the correct way.

All doable, so lets go.

Given the wire I am using (1mm wire stripped from a 3 core electrical cable), the calculations turn out to be: (145.800Mhz137.500Mhz)

Large cable loop: 2223 mm / 2357.1 mm (Brown wire)

  • Antenna height (H1) = 672.9 mm 713.4 mm
  • Internal diameter (Di1) = 295 mm312.9 mm
  • Horizontal separator (D1) = 296 mm 313.9 mm
  • Compensated horiz. separation (Dc1) = 290 mm307.9 mm

Small cable loop: 2112.5 mm / 2240 mm  (Blue wire)

  • Antenna height (H2) =  639.5 mm / 678 mm
  • Internal diameter (Di2) = 280.3 mm / 297.3 mm
  • Horizontal separator (D2) =  281.3 mm / 298.3 mm
  • Compensated horiz. separation (Dc2) = 275.3 mm / 292.3 mm

Diag 1 shows where measurements map to on the design.

Diagram 1, Copyright © 2015 John Coppens [3]

The source website also includes a very handy template that is generated from diameters of the larger and small tubes given. [Diag. 2].


Diagram 2, Copyright © 2015 John Coppens [3]

I didn't use this as I am drilling holes for both NOAA and  ISS SSTV frequencies. For now I am wiring for 137.500Mhz (NOAA) since I can test it today. All going well, tomorrow I'll cut lengths for the 145.800Mhz ISS SSTV and swap out the cables, moving the separator rods as needed.

I am using 10mm 25mm PVC piping for the horizontal post and old 12mm fibreglass tent poles for the separator rods.  Let the cutting commence.


Not bad. Not great, but not bad. Next up is the wiring. I used polymorphic thermoplastic to neatly bind the wire to the middle separator rods. The wire can be easily adjusted to make the rounded form required whilst holding firm.


The polarisation does matter here, so with the smaller loop (green) running north-south, the wire is twisting counter-clockwise. Soldering next [diag 3].  


Diagram 3, Copyright © 2015 Akos Czermann [4]

A little clumsy, but eventually sorted.


Having made the basic structure and securely wired it, I need to place it somewhere with a good view of the horizon to test against my store-bought Sky Scanner Rx antenna.

The plan is to hang it in the loft and wire it into a Raspberry PI running RTL-TCP via an RTL-SDR dongle.

Results will follow.