Sunday, July 31, 2011

July '11 Reports

31 July 2011: During the whole of this week, the Sunboxes have been exposed to the sky, and it has been a good week (sunny), so we haven't suffered, in fact Sunday 31st was the highest daily score (20 kWh)  on the Sunboxes since April or last October. Power consumptions are all DOWN on last week and PV and Sunboxes are all UP on last week. In fact for the last week, the daily average Sunbox thermal capture has been the highest ever in Summertime working. I am not panicking to get the Surya-3 Sunboxes finished while this good weather lasts and the thermal capture is good. Ground temperature was 13.5º. These are comparable to last year's summer temperatures.
  One small mention, our PV installation is about to blast through the 6,000 kWh point, and if the weather is similar to last year, we got 660 kWh in the August and September of 2010 - so I am hoping to attain a figure of 3,300 kWh for the year from 1 Oct'10 to 1 Oct'11.
24 July 2011: This is the week in which I have started rebuilding the boxes, and I took the fronts off in the afternoon. More of that in another posting.
Our annual figures have levelled off (as I would expect) and the next big change would be if we have a mild autumn and early winter compared with the same period in 2010 which was extremely cold.
The annual house figure is 5,331 kWh, the GSHP is 3,335 kWh, the PV is 3,297 kWh, the Sunboxes are 2,990 kWh.
17 July '11: A goodish week, holding steady, relative to last week's figures. I have been concentrating on the design of the new boxes with every constructional detail worked out, so that re-construction can be done with minimum downtime.  The ground was 13.4º and although this is good, it's not good enough for me, which is why I want to reconstruct the boxes. I can only assume that if it is some weeks at over 13º, there is some thermal consolidation taking place, i.e. a larger proportion of the earth round the pipe getting to this comfortable temperature, instead of just a narrow cylinder. If that 13.4º can move out to fill the full 3.5 metres from the pipes, that is a helluva lot of heat! (If I measured the temp at 6pm it would be hotter of course, but I always wait till midnight to allow the heat to disperse a bit.)

10 July '11: For the first time this year, the house and GSHP aren't breaking records, for the simple reason that a year ago we were on holiday and everything was turned off. Ground is above 13ºC, but only just, it is still 13.3º and this is driving me to consider the redesign of the sunboxes - so that the air temperature in the box can be increased and get more heat buried.

3 July '11: For the 26th Week Running, the House consumption and the GSHP are lower than the week before, and now we are in record breaking mode, every week. The house consumption has broken through the 5,300 barrier (5,295). More symbolically, the GSHP has touched 3,325 kWh... symbolic because that was the highest annual score of the PV panels on the roof - 3,325 kWh. The Sunbox annual capture is falling slightly and I notice that the temperatures in the boxes are not at high as the same time last year.

Ground Temperatures have risen smoothly during the spring, and seem able to stay above 13.0ºC at the moment.

Friday, July 29, 2011

Wetherby Service is burying heat!

27 July 2011: We took a short holiday to Harrogate and Ripon (Yorkshire) and on the way stopped for lunch at Wetherby Service station on the A1(M) - recently built. I was glad to find an exhibition of its environmental strategy and discover that it is using underground thermal energy storage.
    The building is dumping heat gains of the summer (and of the shops and the food centre) into 32 boreholes under the car park, aiming to get the ground up to 18ºC. The ground source heat pump is reverse cycle, so it can do this. Then during the winter, it will bring the heat back up, expecting to reduce the ground temperature to 12º . This is similar to the system being used in all the new buildings of the University.
The only differences between these and my system (apart from the obvious one of size) is that I am not using a reverse cycle GSHP and don't have a building with large heat gains to dump. Houses do not have these. So I use custom designed solar panels and boxes to provide this summer heat. 

Thursday, July 28, 2011

Summertime better to be naked!

28 July 2011: Well it's been 4 days since the covers were taken off, and I have kept an eye on performance. At this time of year, they are doing pretty well.
   The daytime temperature has been above 19ºC so the unenclosed 'boxes' have ticked over nicely even when it has been overcast. When the sun shines, the panels do better. I noticed, after an hour of work by the GSHP (boosting the hot water) that the panels were black and glistening with droplets of condensation. When you take material through a phase change, you extract a lot of useful heat. Later, those droplets will evaporate off during the night. They've averaged about 1.25 kW, with an average of about 0.95 kW in the previous week. That seems pretty clear.
   Does this mean I would be better leaving them exposed all year? Big question for me, as I have staked a lot on the idea of the greenhouse effect enclosure. I've written articles etc.
   However... I know that in the good time with the sun shining at equinox angles, the old boxes frequently exceeded 40ºC interior temperatures. In February, the boxes reach over 30º when the air temperature outside is 10º. I am hoping that in the newly designed boxes, with better insulation and sloping fronts and larger volume, the raised performance will make it worth doing all this, averaged over the whole year. I hope there will be more occasions with above 40º temperatures.
  I am trying to get higher temperatures. If naked panels were better over 12 months, then commercial flat plate solar panels would have bare metal fronts, and no glass or insulation. I'd like to push my deep ground up to 16º or 18º, but at the moment, they seem to be comfortably stable but stalled at 13.4ºC.
  If they were naked, they would run at a much lower temperature in Winter, benefitting from the latent heat of freezing. I didn't want to have very frozen pipes passing through the house (covered with condensation), and the external panels coated with ice.
  One thing I can do is more manual control. I cannot open and shut the large front panels, but I can operate the lower louvre. I will keep the upper roof as an openable component. During the Summer on sunny days, the panels can be tight shut and contain the heat that builds up. During long overcast days, the air temperature is high enough and the louvres should be wide open, so that warm air flushes through. On overcast days below 19ºC, the greenhouse effect will warm up the boxes if they are tight shut.
   What about the Winter?.... well, I have to think that through. I will fix the fronts on and complete the boxes and monitor the whole set up for another autumn and winter, through to the same time next Summer, and will mark the anniversary of these boxes by having another big think - end of July 2012.

Wednesday, July 27, 2011

East Leake update

Photo of the Surya-1 design at
East Leake, with black collectors
arranged horizontally in
a vertical array.
26 July 2011:   I have offered to David H at East Leake to replace his front panels with triple wall polycarbonate. There are stronger winds there and the front face would need a reinforcing bar across the midpoint. I still advocate keeping the existing sidewalls and retain the verticality of the front face because of the trampoline, and for simplicity.
   He needs the fronts taking off anyway as there are leaks somewhere. Although the fronts hinge up, it would be relatively easy to take them off altogether to get access to the radiators.
  They should have been higher as one can see in the photo which reveals a shading risk (photo was taken in February) but he wanted it done without scaffolding and without access to the roof space above.
  I've advised him to wait a week or two to see if my sunboxes improve in performance. As he has not taken a data reading since May, there isn't exactly a hurry as there is no way of knowing how the present ones perform. But there is a leak - a dropping off of pressure in the glycol circuit, so there is some work to be done.

Tuesday, July 26, 2011

Surya3 progress - side walls up

26 July 2011: Well I had other things to do at the Uni today, but managed to get the sidewalls up in the morning, before departure. No matter how careful one is on the ground there is still some cut-and-come again work to be done high up, with a small saw to slightly modify the polycarbonate. The essential things have worked out well, the aluminium edge bits come together with millimetre accuracy! It was worth doing a super accurate drawing last week!
  When I got home later in the day, I got the floors of the sunboxes up into position. They are lightly tacked in, just to ensure everything is plumb and square (they are....) and I can rebolt them later with more washers etc. I have only one detail to improvise, the rear part of the floor where it meets the opening bottom louvre. This needs a custom flashing section which I will have to make by bending sheet aluminium.
  I don't need to hurry because it's clear that at this time of year with daytime air temperatures above 20ºC, the panels are working quite cheerfully without their boxes - therefore, there is no serious 'down-time' while the work is going on - the kilowatt hours are still being pulled in!
  I have tried to do all the components on the ground so that the whole thing is assemblable-disassemblable, and made as accurately as possible, in conditions where I can lay everything out. However, there is still a lot of customisation because it is fitting to existing metal brackets and rails and polycarbonate sidewalls. So if I was starting again with a 4 square meter system, I would do the fixing details with less complexity although the exterior profile that they have now is as perfect as I can make it.

Monday, July 25, 2011

Surya 1 disassembly and heat surge


25 July 2011: This is the week in which I have started rebuilding the boxes, and I took the fronts off in the afternoon with the help of Matt, a neighbour.
   I was able to give them a good clean, there had been white stains from old plumbing putty that have annoyed me for the last year and a half!

Increasing performance!: As it was a sunny day on Sunday, the impact of the black panels being naked in the bright Sun was an immediate increase in kilowatts. This is what I would expect on a sunny day.
   Even though this removal of the front was at 4pm, there was enough sunshine for the Average for the day to be immediately boosted to 1.36kW whereas for previous week with the fronts on, the average has been about 0.94kW - a typical summer daily average. It makes me wish there was an easy way to have a major hinging method or similar that would boost the summer capture. I just don't see how this could be done with the strong wind forces that we occasionally get, and the difficult of a control system operated from a ladder.
  My original thought had been to optimise for Winter and Equinox and to inhibit overheating in Summer. But now it is Summer, I am greedy and want more heat buried and a warmer ground temperature.  This is the intention behind using the sloping face and the thinner PC skin and the larger volume.

Another reason for Polycarbonate: Although Chris Wood has suggested that I could do just as well with a flat plate solar panel or tubes, there is one thing that weighs on my mind. This gable wall over looks an agricultural field that is full of handy ROCKS! We have had a stone throwing incident about 2 years ago and one of the ideas behind using polycarbonate instead of toughened glass was the risk of them being target practice for teenage kids. Flat plate solar panels or arrays of tubes may be safe on the roof, but they are very risky on a wall.

Sunday, July 24, 2011

Disassembly of the old boxes

We who are about to die, salute
the setting SUN!
23 July 2011: Yes, this will happen..... :( This is the last photo of the Surya 1 sunboxes saluting the setting Sun for the last time. Shortly after, the foot mirrors were removed.  the next ones will not need them at the foot, and the ones at the top will be tiltable.
  The floorboards of the scaffold are wonderfully clean! Richard Pearson has recently started his business, so it looks as if the boards have never been rained on!

Progress on the Surya 3

23 July 2011: Progress is being made on the Surya-3 sunboxes!  top photo is forming an aluminium edge around the main sloping front panels. The Triple wall PC is considerably more flexible (floppy) than the 6mm solid PC, so the framing is quite strong.
The sunboxes are temporarily assembled for overnight storage. Many thanks to the admirable Mr Makita for supplying me with such a wonderful cordless drill. The entire work you see there (countless pop rivet holes) has been done on a single battery charge!

Friday, July 22, 2011

Scaffolding up!

Pearson Scaffolding seem to be doing a lot
of West Bridgford houses, so i rang them.
0780-4794374 and 0115-841-1193
22 July 2011: Richard Pearson turned up in the morning to erect the scaffolding. It amazes me how these skilled guys can do it without someone else "to hold the other end".
 So now it's up, I have to get on with things!
 Dr Chris Wood emailed to say that with these changes I might as well have gone with a commercial solar flat-plate panel.... Hmm... That was my first idea, but things took the course they took, with Ice Energy's donation of the swimming pool panels, and with the decision to plumb the liquid circuit in the Trickle-and-Whoosh method.

Surya 3 Construction starts!



21
July
2011 : 

The Polycarbonate arrived yesterday and today I bought most of the Aluminium, Screws and Bolts that I will need for the job. I also got some neoprene foam strip to help make it more airtight. The detailing will be thermal break design, i.e. no direct thermal loss except from screws and bolts. There will still be a louvre at the bottom for ventilation. The top rooflets will be openable and the top mirror will be adjustable.


The most important thing is to get the geometry of the side panels correct. That determines the precise dimensions of the front and soffit panel. 



 I now wish I had used Stainless Steel plate for the top mirrors. The aluminium ones are effective but would be more so if they had a nearer to mirror finish and remain perfect for several years, which would be the case with stainless steel. I might still do this, as thin sheet is not too expensive.



  Most of the jointing is with the Riveter. It's easy to drill the 1mm PC outer skin, and the rivets hold the PC firmly.
  I am going to use the existing cantilevering Polycarbonate sides and they are securely fixed to the metal rails, fixed with anchor bolts.

Saturday, July 16, 2011

Close to decision time on Surya 3

15 July 2011: I have invested a lot of time in getting the details right for the replacement sunboxes. Previously, I had the scaffolding up for four months, and I had the polycarbonate delivered early and was able to spend a lot of time tinkering about on the scaffolding getting the details right with the minimum of cutting. I am about to place the order with LIV supplies but need more than ever to get the sizes right.
  I have a schedule to meet, which is an annual target of kilowatt capture, so I cant afford too much down time. The scaffolding will not cast shadow, but the time that the boxes are removed will be missing out on summer storage. Also, with a weeks time lag to get polycarbonate, I must get all that I need and not discover some missing bit once most of it has arrived. This triple wall is cheaper than the solid PC I used before, but I shall be needing more aluminium - I will try to recycle as much as I can from last year's build.
  I shall have for recycling, re-use or whatever, 5 square metres of 6mm solid clear Polycarbonate. Any offers?

Wednesday, July 13, 2011

How does 15% become 30%?

12 July 2011: It has troubled me, that there seems to be a mathematical puzzle. How does a 15% improvement in COP give a 30% improvement in electricity consumption?
  At New Year's Eve, the deep temperature of the deep boreholes were 5 degs warmer than in the winter of 2009-2010. On this basis, I expected the improvement in GSHP efficiency to be in the region of 15% at best - the rule of thumb is that each extra degree of warmth in the heat source gives 3-4% increase in COP. So 30% should not be possible, but this is the evidence of our electricity readings.
  It struck me of course, and I don't know why it took so long. Most good quality Heat pumps on the market have a protective algorithm, that if they cannot get enough heat from the ground, they change over to direct heating. Our GSHP is nominally 6 kW and for the first two years of existence it used 222 hours per year. In the first test year from Oct'09 to Oct'10, it used 111 hours (strange mathematical coincidence there). That makes a difference of several hundred kilowatt hours every year. If the COP improves significantly, it tips the GSHP over into the happy state of not using the emergency 1:1 heating. In the whole of last winter, the coldest on record, it used 1 hour.

Tuesday, July 12, 2011

Form finding GIF

Click on this to make it animate
12 July 2011: Here is some more 3-dimensional form finding. This image may not animate, but if you click it to make sit in its own window, it may animate.
  This is all the same object, but it is parametric and allows me to change the front angle - the consequent geometry is all recalculated with a neat bit of trigonometry.
The preferred final solution - 70º
  I didn't take the 55º seriously, but have been thinking of the 60º angle. Now that I have seen this, I feel more inclined to stick with 70º as a best compromise.
  A great projection will cause too much shading to the windows below. This sun angle is midday in the Equinox period.
  The triple wall PC is fluted and not polished, so I hope it will suffer less from reflection of light and heat off the glassy front of the panels.

Monday, July 11, 2011

Form finding

10 July 2011: I have been climbing up the ladder to measure the existing boxes - they are exactly fitting the original drawings from which I placed the order for the PC - the main unknown was the space between the boxes.
  I decided that the side panels are so firm and well fixed, they should stay and be the main cantilever supports for the new box. It would therefore be possible to retain the rooflets and the louvre unchanged.
  That means that the sloping angle has to start and finish from the front edge of the 200mm line, causing the overall structure to project far from the wall and shading the windows below. although I would prefer a 60º angle at the front, and a right angle at the apex, it looks a bit alarmingly large. The smallest one, the 75º front, is optimal at the winter solstice, but this is a short moment. Equinox occurs twice a year and has the highest scores on the sunboxes - it's a time when the GSHP is still in the heating season, but there is good daytime sunshine. Also, heat comes from the bright sky, not only direct sun angle.
  53º would be optimal for the Equinox but I didn't consider this angle for a moment as it is just too projecting a profile.
  There is a temptation to stay with the idea of the two boxes because the hinging mechanism built for the present boxes could continue to be used. However... if I'm to go to the trouble and expense of making this change, it should be more significant, not just a tweak. So maybe it will be the 70 or 65º angle... a true british compromise, and sticking with the idea of combining into one volume.

Friday, July 8, 2011

Double width sunbox design

This Surya mark3 would be of twin wall Polycarbonate
with aluminium framing. The upper reflectors
are a wintertime optional booster
7 July 2011: If I rebuild the sunboxes, it may finish up as a large single one - double width.
  Thinking of earlier postings, I remember regretting that I had not made the sunboxes as a larger volume. Although it's OK for the liquid to be fed into the panels in a manifold arrangement, I realise now that one wants a good thermal balance between the volume of air and the volume of liquid in the black panels. If the balance isn't right, then the black panels can chill the air space too quickly.
  There is greater surface area and smaller volume with the two existing rectangular sunboxes, and they don't balance up their temperatures with each other, e.g. the West one is tree shaded in Winter and Equinox, but the thermostat sensor is in the East one.
  Assuming that the air is at about 25ºC and the liquid is a 40-60% glycol water mixture.

 Volume of air = 2.96 m3 (present volume 1.02 m3)
 Volume of liquid = 0.048 m3 (assuming 4 m2 x 12mm)
 Mass of Air = 3.55 kg (present mass 1.22 kg)
 Mass of liquid = 51 kg
 Thermal capacity of air/ºC = 3570 joules (present capacity 1230 joules)
 Thermal capacity of liquid/ºC = 183,500 joules

So, the liquid is unchanged, but the air has almost three times the volume, mass and thermal capacity, the ratio of liquid to air changing from 150x to 50x.
  Question is, do I do it this summer or next? During the summer, the GSHP is virtually inactive, and the ambient air temp is warm enough for bare black panels, so it seems that a vote for this summer would be better. Also... I have some free time at the moment.

Monday, July 4, 2011

Sunbox modification needed?

3 July 2011: As stated in the July report, the Sunbox annual capture is falling slightly and I notice that the temperatures in the boxes are not at high as the same time last year.
   I suspect that this is because of the high sun angle on the face of the boxes, and the air tightness of them. They were more leaky and more productive, this time last year. In a month when the average temperature is above 18º, it makes sense to leave the lower louvre open all the time. I am sure that David Atkins and Chris Wood would agree with this.
  This will probably get higher temperatures in the middle of the day, and yes, it will cause a shut off earlier in the evening when it cools quicker. The black slabs in the boxes contain about 48 litres of glycol, and the cold liquid takes about 10 mins to move through, so they are cooling the airspace quicker than it can be re-warmed by the Sun - at the very best, the temp gets up to about 37º whereas in February and March (with more direct sun angles), I was seeing box temperatures of 40-45º. In July and August, they would probably work better in fresh air, as I originally intended when building them with openable bottom louvres.
  In the short term, I can cut the tape that makes the lower louvres airtight. In the longer term, I can work on the design of a new box shape, and decide if it's to be done this summer or next summer.

4 July 2011: As a special celebration of US independence, I climbed up the ladder and took the tape off the bottom louvre of the right hand sunbox. (lied about the first half of that sentence....)
I will keep an eye on the internal temperatures, and really, should have enough self-belief to take it off the left hand box too.
5 July 2011: Oh here goes, I'll take the tape off the left hand box too... and give the aluminium reflectors a good cleaning while I am up the ladder.

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