Permaculturing in Portugal

One family's attempts to live in a more planet-friendly way

Let there be light!

Welcome though it’s been, the last month of rain has brought work on the roof behind the main building to a standstill. Jonny was able to construct all the wooden boxes for the slightly unconventional lighting system, but without a rain-free day to fit them, he never got to oversee the completion of his roof before he had to return to the UK. So this one’s for you, mate! (And by the way, I still have your fleece, your gloves – 2 pairs, your …)

Today, the sun returned, and with a rain-free forecast in prospect, we stripped the temporary plastic covering off the roof and got to it.

Light box assembly line

The light box assembly line. Wooden frames and lids assembled and waiting on waterproofing

When originally thinking about a lighting system for this area, I’d considered solar light tubes. But all the manufactured ones I found were ridiculously expensive and massively over-engineered for our very simple application. Making our own was easily within Wayne’s metalworking capabilities but was going to mean sourcing something to use as lenses. Nothing suitable (or suitably priced) was forthcoming after several internet searches. It remained a puzzle until I saw this video on the recycling of PET soft drink bottles as light tubes. Problem sorted!

The next task was to figure out how to fit them into the roof. In the Philippines and Brazil, where this lighting system seems to have been mostly pioneered, bottles are sealed into metal collars which are then dropped into holes cut in what are generally thin metal roofs. But this roof is to have a covering of soil and vegetation, so the bottles would need to be raised above the roof surface to catch enough light. Also, with the intensity of the sun here degrading most plastics within a short time, I wanted to have a system where it would be relatively easy to remove and replace the PET bottles once they started to show signs of becoming brittle. So I had the idea of creating lidded wooden boxes which would be set into cut-outs in the roof, with the lids easily removable for bottle replacement.

Light box assembly line

3 frames (stacked) and more in the background

Light box assembly line

Box lids with PET bottles installed. The box lids are covered with a self-adhesive weatherproof bitumen flashing tape

Light box assembly line

Box frames. The insides are painted white to reflect more light and the outsides with bitumen so the flashing tape adheres to them

Light box assembly line

Close-up of the upper surface of a box lid. There is a collar of aluminium foil around the bottle where it fits into the lid so no light is lost on its passage through the lid. The surplus foil will be removed and a bead of silicone sealant used to seal the bottle into the lid from the outside before fitting

Light box assembly line

10 boxes and lids complete

The first hole is cut and frame fitted

The first hole cut and frame being fitted

Moving along the roof

Moving along the roof

Frames in position for the toilet area

Frames in position for the toilet

Light box assembly line

Drilling for the cut outs. Also introducing new team member Liam “Yosemite Sam”

The toilet light box frames in place

The toilet light box frames in place. At this point I realised that the lids could easily be removed during summer days

Trying lids on for size

Trying lids on for size …

PET water bottle light

… and to see what effect they have. Working well!

The lights make a huge difference beneath the roof. I’m planning on fixing collars of 12V LED lights around each bottle, turning them into ‘lightbulbs’ at night-time as well.

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  1. Pan June 3, 2012

    Yet again I’m awed by your project and your pragmatic applications to achieve your results; Have you tried different coloured pet bottles? Thanks again for your blog, I’m inspired!

  2. Quinta do Vale June 3, 2012

    Hi Pan. Thank you! It really does make the whole web thing worthwhile to know that others are finding this blog a source of inspiration. Coloured bottles … yes, I did think about coloured PET bottles, but rejected them for 3 reasons. First, I prefer plain white light for area lighting. Second, when the sun’s not shining directly on the bottles, then the amount of light they cast is closer to 20W than 50W. Coloured bottles let much less light through, so on dull days and after 4pm they’d be not a lot better than useless. Third, there’s going to be a bottle wall or two under there eventually so coloured light effects are already in the plan.

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