Tuesday, October 30, 2012

ETFE panels need new hinges

30 October 2012: The inner frame of the ETFE panels have 30mm square welded aluminium frames and the previous polycarbonate had a 16mm thickness. The front panels are 'fatter', so the hinge detail needs permanent modification. (this means I won't be able to re-use the old polycarbonate panels as a replacement should these get damaged or something).

As I do not have a helper, I had to make a temporary cradle that would hold the fronts in position while I disconnect the old hinges. As my helper previously was called Bill, I wondered if I should call this 'Virtual Bill', but ended up calling it 'Brian'.Brian is doing a great job supporting the panel fronts at the lower end, and the clamps ensure that the front is safe against gusts of wind while I work.
Two hinge tops are in place and now the Sunbox front must be closed tightly so I can drill the 8mm holes for the M8 bolts to secure the hinge.Hinge is now completely safe. The frame is fatter, so it has forced the roof upwards and the finished roofline follows a slightly different angle. I have used a strip of compressible foam glued in to the gap to reduce air leakage.


Next is the left hand panel, and Brian is helping again.
Both Sunboxes are now secure at the top. I need to complete some fixing at the bottom of the frames, and they will be complete. The scaffolding can't come down until the lower roof sunbox / panel goes on.
  At the moment, I am keeping the old front panels, but later, as my confidence in the ETFE continues, I might re-cycle the aluminium from them for a future project. 
There's not much more to do on the fixing up now, I must just monitor the results for a few months. On the first full sunny morning of having these, I noticed that even with a washed out sun, they were delivering over 2 kilowatts. Let's hope this continues.
   You might notice from these photos that I also removed the MIRRORs that have spent two years at the top part of the sunbox. With the sunbox facing more directly toward the sun and receiving more direct thermal energy, the contribution from the mirror is not worth having. Leaving it up is a long term maintenance problem because the Mylar has to be replaced eventually.
   I have to submit a paper for CIBSE by the first week of December in which I shall make a preliminary report on this and other aspects of the work. Bear in mind that we are in the first winter quarter, but that is still quite a good test of the system.

Goodbye to the Mirrors

For over 2 years now, I have used the idea of 'mirrors', to act as boosters to the Sunbox by gathering more sunlight. They were intended to improve the solar capture in winter by forcing more heat through the roof part of the Sunbox, as is done with thousands of rural solar cookers in Africa and the Subcontinent. 
    These should be redundant now, with the new ETFE fronts. The bare aluminium 'mirrors' helped through the first winter, but became very matt grey after a year of exposure. I then added Mylar film which restored their power somewhat, but the Mylar gets dirty and should really be replaced annually. It is not fun 8 metres up atop a ladder and this is not a task I want to do again - and with the ETFE fronts, I cannot really consider leaning a ladder against the front faces. 
   The upper mirror was only intended to boost sunshine in the winter and this is not necessary any more. This mirror does nothing in the summer because of its 60º angle. There are internal mirrors in the Sunbox which still reflect light upwards onto the black collectors. They will remain active.

We Salute those who are about to die - but they will live again, as the aluminium sheet is very usable for a future project.Five spins of the 5mm drill and the rivets are gone and the mirror is free!

Both mirrors gone now, the wall looks a lot tidier, and the Sunbox looks less bulky.

Sunday, October 28, 2012

More slating progress

28 October 2012: [Extension] One of my Tall Building Studio students, Pelin, came over to help for an afternoon and most of our daylight time was taken with collecting the old polycarbonate panels from East Leake. With our remaining daylight, we set about working on the slating of the west wall. Getting slating started is the most difficult because in the first two courses, there are a lot of cut slates, and we ran out of daylight soon, but it was a good start. Having someone working for you is an incentive to work quickly, and I was doing all the cutting while she fixed. Sorry, we forgot to take a picture while she was helping. 

This was good start, although later I noticed (and fixed) an error in the batten spacing higher up, and I realised I had to take some slates off again in order to fix the aluminium corner angle. Cutting cutting cutting…. once you get a system going it gets quicker. 
Now the aluminium corner angle is fitted.The slates are put back in and fit perfectly to the corner angle. 
Aaaah. thats enough done for a day. Time for a late lunch and after that, to fix the ETFE fronts onto the Sunbox. Later in the evening, long after dark, I continued with slating on the east wall, getting to work it around the window.Picture later with a few more added: It is amazing how long it takes to sort out all the corner and edge conditions. Quite different from roofing.

Surya Sunbox refronted with ETFE panels

28 October 2012: Winter has arrived, the hours are shorter, it rained almost all day on Sunday 28 Oct, but I had an imperative to get the Sunbox re-fronted with the Holscot ETFE frames because I am going to be paying weekly charges for the scaffolding. 

The ETFE panels are still in their packaging on the left, but I have taken one of the polycarbonate fronts off the right hand sunbox. Here I am getting the ETFE panel out of the packaging, terrified of accidentally puncturing it. Luckily the wind from yesterday has ceased and it was easy to handle the large panels. 
It turned out to be impossible to position them alone, and one of the Sharphill forestry group, Bill Logan happened to be walking past the house at that exact moment and offered to climb the scaffolding and help out. Thanks to my very accurate fabrication the week before and with the help of Bill, the panels slipped into place very easily. Here's the first of the panels, with a holding bolt at the top hinges. We try the left hand panel, and Bill is holding it in place (without the hinge bolts fixed yet) hence the nervous expression. Didn't take long to fix the bolts and make it safe!
We then lowered the triple-skin polycarbonate panels to the ground. Note how much rain had fallen just in the short time we were up there. First view of the new ETFE panel fronts, now allowing people a view of the interior. The ETFE is not optically clear, but it is transparent to thermal energy.

In the remaining daylight, I secured the lower parts of the frame to ensure that they remain reasonably airtight. I am not sure if I can re-use the 'bonnet-stay' detail, but I will do so if I can find a way to adapt it.
     I will modify the detail at the top  hinges next time I get some daylight.
     Sunday, it has been very grey all day and spent most of its time raining, so I am looking forward to the next sunshine to test out our new ETFE fronts. I am very tempted now to remove the MIRRORs as the performance boost they gave the old panels is probably not needed.

Goodbye to East Leake

27 October 2012: David Hill in East Leake has decided he needs another use for the wall on which the Sunbox was fitted, and offered me back the parts. This coincides with my interest now in building a roof mounted sunbox on the house extension.
   This panel (modelled by my helper Pelin) is perfect size for the new sunbox with all the correct aluminium sections and hinge details already included. 

Friday, October 26, 2012

Use more of the Swimming Pool panels

26 Oct 12: I met one of my colleagues who has been doing research with 4 of the same SolarFocus swimming pool panels that I have been using in my Surya Sunbox. His research is finished and the panels are redundant.
     It is very tempting to use those instead of the PVT panels, and there is enough roof surface to enlarge the area from the present 4 sqm to 8 sqm !
     I could use it to amplify the present solar capture, but more usefully, I could also use it to experiment with the design issues of having a construction of a Sunbox on a sloping roof. It would need ALL of the roof, thus covering up all that beautifully placed Aluminium.... Oh well!
I will have to ring the company who are presently looking after them to see if I can collect them. As the panels were donated, there seems little reason for them not to let them be used!
  In the drawing, the blue lines are the raised seams that the mounting rails would fix to.

Thursday, October 25, 2012

More thought on the solar shader - curve!

25 October 2012: Having decided that I might be able to make a wing shaped louvre, I thought harder about it and realised that a thin crescent shape might work better than a wing, especially in Winter. It would bounce the light better into the kitchen, providing it was bright finish on both sides.
Back to model making!: it is extraordinary how quickly it is possible to devise or refine a mechanism with some paper (or card), pins, scissors and glue.
Then I worked with ArchiCAD to work out the spacing of the uprights and to workout the size of the mechanism that swivels the louvres.



ETFE lifted up

25 October 2012 : (I shall have to retake this photo in daylight, it was taken in the twilight and the picture is very fuzzy).
My daughter has been to stay for a couple of days, so I had some on-site help to get the two ETFE Holscot panels up to the top level of the scaffolding. It required some ropes and good knotwork. We were worried about the light frames blowing in the wind against one of the scaffolding poles and getting punctured (they do look like polythene). After that I had to take her to the rail station to go home, so  additional work will have to be done on it when I get more daylight and some time to work in. They now have enclosing frames, and are dimensionally as accurate as I can make to the previous (existing) fronts. Let's hope these fit when I try them out!

Tuesday, October 23, 2012

First steps with the ETFE

21 Oct 2012: I've made a start with re-fronting the Surya Sunbox with the ETFE panels donated by Holscot

First I had to go up the scaffolding and record the various hinge and frame details so that I wouldnt have to keep yo-yoing up and down the scaffolding to try and remember how the new frame should be cut at the junctions.
The two ETFE frames are in stout cardboard packaging, with stern warnings to be careful if using a knife to open the box.One of the frames emerging, with its inner packaging of Bubblewrap. I am terrified of puncturing the ETFE. Turns out that the aluminium frame within is welded at the junctions, giving me more confidence in its strength and squareness.
First Cut of the outer enclosing frame. I cannot drill the ETFE frames, I have to make a wrap around frame that holds them with metal tabs.Getting the corner true and square seems to need a lot of clamps. All the rivets will point outwards so that the ETFE frame fits snugly within.
I have a lot of rivets, there is no point in economising on them. The frame doesnt have to be totally stiff at the corners because it is non structural. I want it to be reasonably airtight as it wraps around.Two part frames set up on the lawn, ready to rivet the corners. 
The inside line of the frame is a 50x3mm flat. The catfood trays hold water and the paint brush is a way of keeping the drill head cool - elongates the cutting life of the drill head.First attempt to see if the frame sits around the ETFE. I am slightly surprised that the ETFE is not optically transparent, but I am assured that it is transparent to solar thermal energy.
It's time to commit myself by riveting down the corner, using a large square to make sure the angle is 90º. All corners riveted now. I'm not sure that a cross piece along the top will be needed, I have to leave that decision until the frames are on the scaffolding.
The front panels have to be hinged, so these are cut from 40x40x3mm angle. Hinges are now drilled and shaped, but the hinging hole will not be drilled until the frames are up on the scaffolding.

Monday, October 22, 2012

Ideas for the solar shader

19 Oct 2012: The large window will have a solar shader, and initially, I can re-fix up the mirror-shader that was made for the previous window. That worked fine for the winter. For Summer use, we need a more cantilevered shader, and I planned a triple louvre shader cantilevering about 700-800mm. I have a present method of making louvres that keeps the aluminium flat, and has a stiffening rib behind. The outward facing surface can be mirrored with Mylar. I want the outermost louvre to tilt fully so it directs sunlight into the window, but the two nearer the wall to tilt only slightly. 
After doing some sketches, I devised the principles of tilting the first two and having a reciprocating tilt for the third. As it is not clear what the dimensions would be for this to work smoothly, the only way to progress the design was to make a working model. Even without dimensions, the mechanism would reveal itself.This model, in cardboard, is about 50% scale and the third louvre needs a cranked or angled tilting lever. this is a good way to establish if the principle works. It does.
This is in the Winter setting. With the cranked lever above the right hand louvre, it is possible to get all the louvres parallel in the winter and the summer setting. The outer faces of the louvres face out correctly. The right hand louvre has a mirror finish and reflects sunlight onto the window. The left and middle face the sky and reflect daylight onto the window. The problem with the reciprocating louvre is that there is no useful middle setting. If I make them to beall parallel, there would be some in-between positions.

The Summer setting is shown here, and it is really 'neat' the way the third louvre flips as one moves the control lever.
   If the louvres remain one-sided like my existing one on the previous window, then this would be the best solution, especially if the outer one is a bit larger.

This shows the location of the shader on the south wall above the large window. I might use the old existing shader at the sill level to bounce light up into the south window.
 

As I was going home after making this, my colleague suggesting making a wing (mandala) shape for the louvre, so that they could be double sided, with both sides reflecting. I realised that with my experience of doing the metal roofing, I know enough now to make a wing shape - with the 0.7mm alloy. The 1.2mm is too stiff to do it, but I tested the 0.7mm and it is quite possible.
  I have also managed to find some mirror finish aluminium (but only 0.5mm gauge) and I am weather testing a piece of it in the front garden now.

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