Wednesday, March 30, 2011

Point of non-return for East Leake

30th Mar '11: I had an email from David in East Leake to say that in the plumbing layout, they had forgotten to include the Non Return valve. This simple omission must have caused it to under perform. It has captured about 110 kWh since February, whereas my Surya Sunbox installation at Peveril has captured nearly 4 times that! I was worried it might be due to not being air tight, but really, the greenhouse effect works even if a structure is not fully airtight.
  So I will now observe future meter readings and hope that his installation catches up eventually!

Monday, March 28, 2011

Waxing the mirrors

28 Mar '11:  The foot mirrors have to be re-angled to be almost horizontal, post-equinox, so that the midday sun really drives into the Sunboxes. But if the solar performance is better, with that flat angle of about 10º, they will pick up more dirt, bird shit etc. Even rain will leave dirt deposits.
    I took the car to the carwash at the weekend and had an idea. I bought some Turtle wax. I would have preferred some T-Cut, so that the surface might actually be smoothed, but I suspect that T-Cut cuts paint films but not bare metal.
    My mirrors will never have an optical mirror finish because they are a brushed finish - aluminium tarnishes to a stable level of matt shininess and if you want a much brighter finish you need stainless steel. But the foot mirrors have got dirty and they are a major contributor to thermal harvest. They could do with being cleaner and shinier.
    I put some Turtle wax on a test piece of aluminium and when water  is trickled onto them, it forms into droplets and runs off. On the remainder of the piece, the water is more of a flat sheet. So now, I have been up the ladder and polished both the foot mirrors, leaving just 30 cm unpolished....
1. because I couldn't reach it without falling off or moving ladder, and 2. to leave a bit un-waxed, so I can compare their appearance a couple months on, into the summer.
  Monday was very sunny, but with reduced activity from the GSHP, the Sunboxes don't capture so much either. This is another reason to give those mirrors a polish - get more sun in! the PV had its highest score of the year so far, over 16 kWh, meaning that most of the Sunshine was delivered in the morning.
 PS: I fitted up the right hand (easterly) pipe cover, so now the panels are symmetrical! Let's hope that reduces long term maintenance.

Saturday, March 26, 2011

March heat wave!

26 Mar '11: We seem to have had an astonishing run of sunny days, with all the students at the Uni wearing summer clothes, tutorials taking place on the lawns and even on the flat roof area. Back at home, the PV roof has been recording good scores every day. I also notice that the Sunboxes have been doing well, with their score being 90 kWh more than the PV roof since the start of the year (450 as against 360....) and with a week to go to the end of the first quarter!
  Today, the PV roof has just passed 4000 kWh (since installation), and the Sunbox meter hit 13,000 on the same day. As it started with a few thousand on the clock, that is merely a coincidence - the real count is that it passed a figure of 3,000 two weeks ago, and is romping ahead, consistently harvesting more kWh per day than the PV - unlike the way it performed last year.  The GSHP sits idle for much of the day, its consumption per day being less than 10 for the whole of last week - it has been a total of 48 kWh for the last week which is good for a week in March.

28 Mar '11 Postscript: Following the weekly summary on Monday, the system here is again breaking records for annual performance. There are four main summations each week:
  • the House meter : Record Low! 5,555
  • the GSHP meter : Record Low! 3,564
  • the PV meter : Stabilising at 3,250....
  • the Sunbox meter : Record High! 2,982
We don't have a grand slam of four, because the PV annual maximum ever was 3,325 kWh last October, and currently it is stabilising at around 3,250 kWh per annum. April 2010 was extremely sunny and if April 2011 is not as sunny, the annual PV figure will go down :(
  The underfloor heating circulating pump draws its power from the electric supply to the GSHP so that is adding an apparent 250 kWh or so to the GSHP's consumption figures.
 As the best (highest) PV annual was 3,325 and the best (lowest) GSHP is so far, 3,564, we are only 240 apart before we close the figures. As the underfloor circulating pump uses more than that, we are Carbon Zero now for heating AND hot water, so we now need to improve efficiency further to include the floor pump. That is less than one kilowatt hour per day, over one winter between September and April - Let's do it!

3 April postscript: Here are updated charts for ground temperature and degree-day to heat pump comparison.

Sunday, March 20, 2011

High performance in the sun

19 Mar '11: Sunniest day of the year so far, with a PV maximum of 16 kWh and Sunbox capture of 18 kWh.  That PV score is good for a day before the equinox and it seems these days that the Sunboxes so far always seem to exceed the PV roof. I don't think this will continue during the summer, the PV should push ahead and I hope we get a few days like in summer 2010 with regular scores over over 25.

   Today's score of 18 for the Sunboxes was slightly below the 20 we got a week ago, but this is because the GHSP was less active. Both the house and the GSHP were below 10kWh, and we scored another negative difference, whereby the overall house consumption is less than that of the GSHP. The annual consumption will be recalculated on Sunday and again, it is likely to be less than last week's.

More Mirrors
In this picture, the windows of the south wall are shown for the last time without mirrors - I intend to start with the dining room window, and work my way through the small ones. On a sunny wintry day like today, the south-window solar gain provided a real benefit, giving a good interior temperature and keeping the business of the GSHP to below 10 kWh.
I've also been doing more work on the metalwork of the Sunboxes. I elevated the West-return-pipe cover to the sunbox in the evening, and it will protect the insulation from rain and UV degradation. In this photo in the workshop, the East-return-pipe cover is taking shape, with aluminium, a file, a light hammer, a 'workmate' and an angle grinder.

Welcome to the Moon
This was the night when the moon is the closest it has been to the earth for 18 years, and there was a full moon with clear skies. (this is not my photo, my iphone camera is not good enough to get pictures like this!)

Wednesday, March 16, 2011

Idea to add more mirrors!

16 Mar 2011: I am so taken with the diagram that I published last weekend that I am considering adding more mirrors. This seemed to me to prove that on sunny days, the performance of the Sunboxes was substantially improved.
   The aluminium is already ordered for the head mirror over the large dining room window below. This is at the right angle to increase winter gain, thus reducing heating load for the heat pump.
   I have a parametric model (in ArchiCAD GDL) allowing me to experiment with the depth of the bracket, the tilting angles (calculate reflection angles at different seasons), allowing me to know how much metal to cut.
   There is no point in using foot mirrors to shine upwards as the sill of the dining room window is so low relative to the hillside behind. But the Upstairs bedroom windows could benefit from foot mirrors. They would increase heat gain in winter, and can be swivelled away to do nothing in summer - or can be lifted out of their brackets for the summer.
   Now that I have to write an article about my Sunboxes with one of the leading ideas being that they are like a Solar cooker, I feel it would add interest to do this for the windows too - but I wish I had thought of this last autumn.

Actually I did think of it last October (2010).... when making the mirrors for the boxes, I held the aluminium at different positions and angles to the window and thought that it might help, but I had enough other things to do without adding that to the list. Now that I have some proof that they could be effective, I feel new determination.

Tuesday, March 15, 2011

Soph Solar generating!

15 March '11: Now Soph's house is a power generator!
Inverter in the attic 
Left: master switch for DC, Centre: Inverter, Right: master switch for AC to meter
Handheld meter in the house
and the first few watts going down the line!
Thankyou to Carbon Legacy for this ultra quick installation.... all done in a day! and fully paid for immediately.
I am not sure which electricity supplier she is with, but I wonder if I should try to persuade her to go with Good Energy, the UK's only 100% supplier of renewable electricity.

Soph Solar going up!

Tues 15 Mar '11: The installation in Norwich is happening today! This is my daughter's house and we are doing a sort of 'roof leasing' arrangement with her as her roof is so well oriented.
The scaffolding was put up on a sunny Monday, and the panels are going up on a damp foggy March Tuesday in Norwich. This is quick work, considering that we only ordered it a week ago! When I had mine done in 2009, it was 2 months from order to delivery - there was a shortage of panels at the time due to high demand in Spain. The UK is currently a leading market for them due to our feed in tariff.
   We have employed Carbon Legacy, the company who are also providing the site for the East Leake Surya Sunbox installation.

The working area is 4m x 4m so its a matter for final decision by the installer team whether it is 4x2 or 2x4 arrangement, depending on details of the verge and ridge and chimney flashing. We are using 235W  1000x1600mm polycrystalline panels which should be better in overcast conditions than monocrystalline... will be interesting to compare on a weekly basis with my own mono system.

Getting the first panel on without breaking a roof tile...
Half done now.... 4 more to go. 
The sag in the roof is a slight problem, but there is a very strong new purlin underneath which can carry the whole weight safely (it was put in there by Tom the Builder because of that sag).
Looks like it is complete! Only internal electrics to finish off!

Monday, March 14, 2011

Annual consumption figures go below target - good!

14 Mar '11: Weekly Summary of annual figures
I recompute the annual figures every week - for consumption and power/heat generation.
  • The house annual consumption is now safely below 5,600 kWh and 
  • The GHSP annual consumption is below 3,600 kWh

Let us hope that the weather is 'average' enough not to bring a last cold snap of the winter, so we can stay below these figures all summer! I fixed a cylinder thermostat a while back to reduce overheating of the DHW, so with some luck, the summer GSHP consumption will be lowered. 

With our recent run of grey days in February, our PV annual is below expectation -  3,240 kWh - we hope to catch up - March is not half done yet, and it has already overtaken the total for February. March of the previous year was extremely sunny, and if this month is not as good, the annual figure may remain stuck at 3,250.

Comparison of GSHP consumption and
Degree days, done at weekly intervals
If our final PV harvest is as good as last year (3,325 kWh best figure), it would be great if the GSHP gets closer to this... but I think that with all my best efforts, that 300 kWh gap between 3,300 and 3,600 is not bridgeable. The PV annual is more likely to be 3,250 or less in the future, our score for the first year was unusually high!
    The effect of the sunboxes is not to put heat into the house, but to improve the GSHP efficiency by 15-18% - not enough to close that gap! Now that we have passed the one-year anniversary of the Sunboxes, their effect on cutting annual consumption is going to be less dramatic. 

What else can be done? The fitting of window mirrors is designed to increase our incidental solar gain on the south elevation (thus reducing equinoctial heating requirements), and I am minded to fit a heat recovery unit for the kitchen dining space. A whole house MVHR unit is not totally out of the question, but the fitting of air ducts is problematic. Perhaps keeping them within the house (and not using the loft space) might be an answer.

Chart of Mirror effect

The top mirrors were added a couple of weeks before the black
line, and the blue curve rises slightly, but it really takes off
sharply at the black line when the bottom mirrors were added.
13 Mar '11: One thing that has always been doubted by some readers of this project is the benefit of the mirrors (the brushed aluminium reflectors that I have built around the Sunboxes).
  As it has progressed, I have been more and more convinced by them, to the extent of titling my next article about them to be about 'Solar Cooker style Sunboxes....'. They were not there at the beginning, so how have they become 'the end' ?
   This graph has provided me with some pleasing results. This is the graph of weekly meter readings for the PV roof and the Sunboxes, during the same period - from Mid March 2010 (when the sunboxes were installed) to Mid March 2011 which is now.
• Spring Equinox '10: the kilowatt hour captures were close to each other, the PV being slightly ahead.
Here is the same chart rendered in Monthly
intervals, and created at end of March '11
• Summer '10: the GSHP is asleep and has no effect in driving the Sunboxes - only the weather does that. There is still a relationship between them, with the PV always ahead.
• Autumn Equinox: '10 This was the month after installing the mirrors. I would expect the weather of October to be similar to March - but look at the difference in the curves of the two systems!
• Winter: Both systems went to zero for a while, the roof was covered with snow for a week, and the energy flowmeter on the Sunboxes also went into Error-2 mode for the Xmas week, so we had some zeroes in both curves. But in the pulling out from New year and the sunny periods of Jan and Feb 2011, the Sunboxes pulled ahead again.
• Spring Equinox '11: The rest of February was dull and grey for about 2 weeks, and now in March, the race is on! - and it is clear that the blue curve is again pulling ahead, with the most recent Sunbox week of March being higher than at any time last March or October.
• End of March '11: March was the driest month in 50 years, and there has been some good sunshine. The two technologies have been racing, but at the end of March the figures were SBs 298/ PV 264.

Sunday, March 13, 2011

Improving Air tightness, and protecting pipes

Underside of the Surya Sunbox - in daylight,
the airgap is quite visible.
13 Mar '11: Seeing how much airtightness affects the performance (comparing the Peveril boxes to the East Leake boxes,) I was up the ladder today with a bit of tape sealing ventilation escapes - to make the Peveril boxes even more efficient. I realise that clear packing tape is not externally durable for the full life of the product, but the bits of tape I used last sumer haven't rotted yet. So the panels are more airtight now, especially along the line of the lower louvre, and at the verge-ends of the upper rooflets.
    When I started this, I imagined big overheating problems in summer, but this never occurred, so the large vents at top and bottom are reducing performance (although if I need access for maintenance, I shall just have to slit the tape.) Unfortunately, for the lower louvres I used 1.6mm aluminium angle, not 3mm, so the louvre has a slight sag.... in the summer, I should replace that section.

The front aluminium is all one sheet, cut and
with folded tabs. The side aluminium will be cut
to shape and riveted to this.
I have also started work on the pipe covers. These will also help to reduce future heat losses, and reduce maintenance risks, such as water getting into the insulation. These chamfered corner units have the same pitch as the roof of the house, and will sit neatly behind the corner mirrors.
   I just noticed from this photo that a few pre-existing holes in the aluminium sheet (picked out of a skip!) have holes in the sloping surface, so these will have to be filled in with rivets.
  It is amazing what people will throw away. This aluminium is the same grade and quality as what I buy from the engineering stores. 

Saturday, March 12, 2011

PV In Norwich!

12 Mar '11: With the summer coming up soon, it seems too good to miss the summer harvest. We have an old ISA that is maturing, and there is the choice of leaving it in for another 5 years at a lousy rate of interest. So we think it is better to offer our daughter a roof-leasing deal, whereby we put the panels on her house, and she enjoys the sales and some free electricity while we are paid the FIT.
  Although it is a terrace house, we are lucky that it is widened at roof height by the width of the alleyway (shared by 4 houses), and the roof faces south-south-east, so the chimney has no shading effect. There's enough space for 8 235W panels of 1000 x 1600, so we hope this will result in 1.88 kW at best - roughly 1500 kWh per annum.

Wednesday, March 9, 2011

Kitchen Mirrors

9 Mar '11: I am thinking of ways to use aluminium reflectors to increase the incidental solar gain in winter and equinox. I've designed this swivelling mirror, and feel rather excited at yet another small building project. Our kitchen window faces south, but is greatly shielded by the bulk of Sharp Hill and the rampart just in front of the window. In the winter it doesn't get enough warmth from the Sun.
   This mirror will not block out sunlight, it is positioned to bounce sunlight and heat downwards into the dining room. With a bit of luck it will increase incidental heat gains in the Winter and Equinox periods. the mirror is on a swivelling bracket. In the Summer, it can be swivelled to shade the upper part of the window, without cutting out any of the view.

As our house is becoming noticeably a place where we experiment with reflectors, this seems like a logical next step. If it can save a few kilowatts in the colder season, it is worth trying. The heat pump always reduces consumption on days when sunshine streams through this window. Soon there will be more!

11 Mar '11 Postscript:  I showed this picture to the students in my construction lecture, and went to the stores after to order the Aluminium.... so I am committed to it now! Who knows...? If it makes a measurable difference, it might go on the other south windows!

Tuesday, March 8, 2011

Sunniest days of the year

8 Mar '11: During the sunny day of Mon 7 Mar, the PV roof captured 13.3 kWh, and the Surya Sunboxes caught 20 kWh. And on Tue 8th Mar, the solar capture was 13.6 and 19 respectively.  There were only two days in the whole of last summer when they captured that much in a day prior to the fixing of the mirrors. After being amazed at Monday's harvest I was delighted that it was also sunny on Tuesday, and the sunboxes were dumping heat to the ground, plentifully.
   It was cold both days (below 10º and below freezing at dawn) and the sunboxes were in the high 20s most of the day. Monday and Tuesday were those rarest of days, when the GSHP consumption exceeded that of the house. The house imported 13.63 kWh and the GSHP consumed 13.65 kWh, and did even better on the 8th, 13.36 and 14.48 respectively. This can be seen by looking at my Metering page (see Links) It helps that in cold air temperatures, PV production is enhanced.
Deep Ground Temperatures August '09-March '11
Red line is the date of installation of Sunboxes

That is a rare condition.
• In the Winter, the PV produces little, and the house and GSHP burn much.
• In the summer, the GSHP only burns only 1 or 2 KW a day, and the PV roof produces enormously.
• There is a short cross-over period in the equinox when the PV can generate so much that it is driving enough power to run the GSHP and enough other devices in the house for it to exceed the import.
It managed this only 4 times last year.
  With the reduced consumption of the GSHP (due to nice warm ground) the fact that it only consumed 13.65 kWh on a day when the air temp never got above 10º and was below freezing during the night is remarkable. A year ago it was using over 20 kWh/day for weather conditions like this!
  Look at the temperature chart on the right - the deep ground temps are rising from their low point of January. They would have risen more, perhaps, if there had been more sun in February.
  Coincidentally, the 7th and 8th March of 2010 were also very sunny, and the Sunbox capture was lower than in 2011.
14 Mar '11 Postscript: Deep ground temperature was 10.7 degrees.

Monday, March 7, 2011

Retrofit with GSHP

EcoBuild note: DNC writes: There were some good lectures and seminars, including Retrofit topics. One that I liked was one from Robin Curtis of Earth Energy with advice on retrofitting with ground source heat pumps. I have always thought this would be too difficult, due to the need for a borehole and the need for underfloor heating, and the bulkiness of the GSHP - difficult to fit to an existing house. But it is not as tough as I thought, and the Penwith Housing association (HA) has done it on a huge scale in Devon and Cornwall, with social housing. (This talk is due to be on the EcoBuild site as a PDF and I will download it when possible).

Borehole or horizontal?: Certainly, ground based horizontals are difficult to fit because it is unusual to have enough space in the garden to bring in a JCB and churn it up to the required depth. A vertical borehole is a very quick and tidy solution, and yes it is expensive - a bit like root canal therapy in dentistry, painful, but once it's done it's done. And then provides several hundred years of free heat.... If there is no access to the rear of the house, it can be done in the front driveway! I have never regretted getting the borehole at the Peveril Solar house. It has been instrumental to making my Solar Charging project work.

Underfloor or Radiators?: Underfloor has always been more efficient at distributing heat from a Heat pump because they work more efficiently if they don't have to heat above 35-40 degrees. But for those contemplating retrofit, there is an answer, and it doesn't have to be gigantic wide aluminium radiators as is often thought.
   If you are replacing night storage heaters, you already have electric points but need to add water pipes. If replacing water radiators, you already have the pipes and the circulating pump, but need to add nearby electric points.
  The space may be limited to the size of the previous radiator. With the circulating temperature at only 35-40 degs, you can put in a fan assisted radiator of nearly the same size as your existing high temperature one. The huge annual savings in overall energy cost justifies the consumption fan assisted radiator, one of the same width and height as the previous, but with a very quiet low wattage fan which comes on when the thermostat deems it necessary.
[postscript: Jaga and Dimplex make these type of radiator.]

Space for the GSHP?: We are familiar with Air source heat pumps being placed externally, but GSHPs need better protection, so usually go indoors. If they will not fit indoors, the Penwith HA have retrofitted many houses with GSHPs using a small lockable prefab garden store from B and Q, just large enough to hold the pump, and this can be close to the external wall in a suitable place. It can be insulated to reduce heat loss from the connecting pipes etc. 

Sunday, March 6, 2011

Effect of Mirrors, delta-T and time delay

6 Mar '11: Chris Wood posted replies to my earlier article about the efficacy of the mirrors,
And as I haven't seen the sun for about 2 weeks in this grey February, I am beginning to wonder myself! Logically, they will only work in sunshine. The weather forecast keeps promising a bit of Sun, but it doesn't come - yet! We are approaching the anniversary of the sunboxes very soon, so we can compare their performance with identical weather conditions of a year ago.

As for the other mode of operation, based on Delta-T, these cold days do not result in much action - we are living off our reserves of heat in the ground. I have remembered that in the late autumn I changed the delta-T to trigger the sunboxes, to 6.0 degs C, to reduce wasteful pumping. This may have been overhigh. When it does work, we do get a good delivery, perhaps explaining the higher kilowatt delivery. However, the number of hours are too small. I changed this delta-T to 5.0 degs today.
    Also, when it starts off, based on delta-T, there are about 4 metres of pipe that are indoors, and the glycol in that pipe has warmed up. At startup, the rush of 4 m of room temperature glycol is so warm that it reduces the delta-T so quickly that the sunboxes turn off again. So I have added a one minute delay to the thermostat's operation, so that that first flush of warm glycol gets buried and the glycol from the boxes and the pipes in the loft have time to get down.

8 Mar '11 Postscript: 7 and 8 Mar of 2010 were also extremely sunny, with PV captures of over 14 kWh, higher than in 2011. But the Sunbox capture in 2011 (with mirrors) was significantly higher. Let's hope this continues!

9 Mar '11 Postscript: I swivelled the foot mirrors of the Sunboxes to the Equinox setting - about 20-25º tilt - this is to recognise the higher solar angle and increase reflection into the box. Later, in summer, the mirrors need to be nearly flat, to reflect the nearly 60º angle of midday sun. I have to remember, it is not only about midday sun, it should be at the optimum angle for a combination of solar altitudes from 10am to 2pm.

New Cutaway graphic

5 Mar '11: It's about time I update my cutaway 3D rendering of the Sunboxes, to show them including the mirrors.
Note: On this drawing, I havent shown plumbing details of how the pipes connect to the heat pump on the ground floor. That's a complication too many, or one for another day!

Thursday, March 3, 2011

EcoBuild - we've done it!

3 Mar '11: I'm writing this, sitting in the van waiting to do the stand 'breakdown'. We had seven New York skyscraper designs on show, and three of our teams won the UK prize, and now we look forward to Prague in May. The prize giving was on Weds afternoon.
Left to right: Prof Wolfgang Feist, Chuyu Qiu,
Ankur Modi, Suruchi Kumar Modi

In addition to that, I found time to go to one seminar and do some walkabouts, and found a few useful stands but regret not having had the time to see many many others, especially those on modern construction methods, eg SIPS, Bill Dunster's house, and other timber solutions.
   I did find Anthony Morgan of  NewForm, the company selling the PV Thermal panels on Walthamstow Fire Station, just as it was time to leave, so hope to get into contact with them again. Also, met Nic Wincott from Cambridge who did a seminar lecture on thermal recharging, with many examples from Sweden. Robin Curtis of Earth Energy is a good man to know too, with an excellent lecture on GSHP retrofit. Also met Ivan Lucas and Wookie of Navitron, who had a stand in the North hall.
  It was great to meet Dr Wolfgang Feist of Passivhaus, Hattie Hartman of the AJ and Roland Matzig and some of the other judges of the competition.
I will look forward to next year's EcoBuild without the need to be on duty on a stand! Some photos and more detail will appear later.

Popular Posts