There was some method behind the madness:
- Our 3.7kW on-roof solar pv system could potentially dump around 14A onto the grid when running flat out.
- Under UK guidelines for connection of small-scale generation, we are allowed to connect up to 16A of potential export without seeking prior permission from the grid operator. That's 2 whole amps to play with!
- We currently dump excess solar generation into space heating (a 400W panel heater currently, and a 1.8kW storage heater in the process of being hooked up), so as far as generation goes, the more the merrier.
- Everyone needs a hobby...
The new system wouldn't qualify for the Feed-in Tariff, so it was important to keep costs down. This was done by judicious choice of components and by collecting the bulky stuff from local suppliers where possible, thus saving a fair bit on shipping charges.
The initial idea was for a couple of cheap 250W crystalline panels mounted at approx. 60 degrees inclination (to both maximise winter generation and take up less space) connected to a dinky Mastervolt Soladin inverter. Output would be knobbled by shading from the house until mid-morning, but from then until virtually sunset, the panels would be in full sun. A bit of computer modelling in PVSyst showed it was a goer. I then came across Solar Frontier's 150W thin film panels, available from Dulas. Thin film technology works better in low light conditions and is more shade tolerant than crystalline technology. Three Solar Frontier 150's came in at a similar price to a couple of typical 250W poly panels but, according to PVSyst, would far outperform them. I could also collect from Dulas' warehouse in Welshpool... and they look better than crystalline panels... and are a little shorter (which helps with positioning). Job done and three panels were soon sat in my garage awaiting somewhere to put 'em.
Solar Frontier 150W thin film panels |
Ubiquitous Mastervolt Soladin - perfect for small systems |
I soon discounted mounting the panels directly off the concrete fence posts, via some dodgy framework of dubious strength. Instead I plumped for a more traditional ground-mount frame, using treated timber. A few rough sketches later and something resembling a frame was soon knocked up in front of the fence (ropey fence panels first replaced!). Panels were attached to the frame using a traditional aluminium rail and clip system. This was sourced from the ever-helpful people down at REDtip (STF Fasteners) in Bilston, a handful of miles down the road. Driving home with 3.2m rails sticking out of the passenger window of a van with a 2m long load bay was 'entertaining'. Fortunately no pedestrians were impaled.
Framework up. Very sturdy. |
Rails and clips in place, ready to take the panels. |
Panels on. Ooh, shiny. |
The new ground mount system beneath part of its big brother |
Do yoou have any data showing that thin film panels actually perform better in low light? I looked at IKEA/Hanergy/Solibro but couldnt find any supporting data for this. I later found the Solar Frontier panels which are at least a good 50W bigger and can be used with transformerless inverters enabling dual arrays, so interested in what you have knowledge of. Also reading your solar diverter posts with interest.
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