Monday, April 30, 2012

Re-organise Meters

Before the alteration
29 April 2012: I have done some re-organisation in the loft. Firstly the new Supercal 440/ 531 meter for the Sunbox was leaking and the washer needed resetting in the joint - it doesn't leak any more! This meter runs off the mains so it cannot run out of battery life like the old one.
   Then the plumbing for the Tubes needed re-organising, as the evacuated tube plumbers got the Supercal 539 energy meter and sensor in the wrong way round. Wasn't entirely their fault as they didn't ask, I assumed they would know. Perhaps I will change that old energy meter as the old meter has limited battery life left, and it was failing before. I phoned the supplier and they say that the battery is not replaceable. The whole unit has to be replaced after 6-8 years. It may be almost that old already!
   I added back in my old pump, because it will be needed in future to push ground loop liquid through the heat exchanger when it comes in. Above is the plumbing before, and below is taken after the work is done. So far, no leaks observed, so I have now also insulated the pipes.
Alteration achieved!
The small amount of plumbing, off to the lower right of the picture needs a complete rebuild as it was installed running along the floor, and is too low to adapt, and too low to use the draincock, lower right. I can raise that 30 cm, enabling me to add in the heat exchanger.

Building a Heat Exchanger enclosure

29 April 2012: The heat exchanger needs to be insulated, so I have built a special insulated housing using rigid Celotex foam. The foam was randomly chosen (out of a skip) but it was the perfect quantity, leaving almost no waste. Above is the initial cutting process, with considerable care to get it cut precisely so that there would be no air gaps.
 The box is built up with a base and the sides, and all edges are glued, taped and also sealed with sealant. Next is to fill in space within the box around the pipes of the exchanger, and to make the lid that could fit over the pipes entering and leaving the exchanger.
I have the fittings, but I am not ready to plumb it in yet, I need to progress in recordable, steady steps. 

Sunday, April 29, 2012

April 2012 Reports

For those just arrived, I do a computation of the ANNUAL performance every Sunday, by subtracting this evening's meter reading from the same one, exactly a year ago. I add the weekly report to this blog diary entry, every week.

29 April 2012: The last week has been horrible, unremitting heavy cloud and regular rain - temperatures below 10ºC, virtually December weather, and statistically far colder than March - 237 degree days instead of 213 for four week periods in each month.
  Newswise, the UK has been following the Leveson enquiry, revealing more the dirty dealings of the Murdoch empire, with both James and Rupert up for questioning. In so doing, it revealed the behaviour of Culture secretary Jeremy Hunt, and this lively story is still on-going. In the same week it was revealed that David Cameron's fortune comes from offshore banking. Korea tried to test a missile, and invited journalists to view it, and there was worldwide satisfaction when the thing failed within a minute, ha-ha. Britain started the week with a hosepipe ban and official drought, and ended it with extensive floods in some places, and no need for hosepipes! London had its Marathon at the start of the week, and is also gearing up for a Mayoral election next week. At the end of the week, we heard of the British charity worker Khalil Dale, who was executed by Taliban kidnappers in Quetta. That rings a bell as my mother used to live in Quetta in the 30s, and it made me wonder how much of the Quetta remains - not much because she experienced the devastating earthquake of May 1935. A Rubber chicken called Camilla took a flight in space. Chelsea beat Barcelona in the Champions League semi-final, with Fernando Torres scoring the final goal, and he went on to score a hat-trick at the weekend.  What about the meters?

  • 4,855 kWh for the House and 2,858 kWh GSHP, not surprising after the very cold week with evening temperatures always in single figures.
  • PV has dropped to 3,340 kWh. This is to be expected with continuous rain.
  • Sunbox is working, and I have got some figures now, but am using a new meter starting from Zero, so it will take time to recompile a figure for them. The Tubes have done almost nothing in this rain.
  • Ground temperature is 10.9ºC. No sun for the whole week and temperatures comparable with November-December have reduced the ground temperature, not surprisingly.

22 April 2012: I have been back for nearly a week, and have some readings now, and have got the Sunbox working again, although not the energy meter with it. I need to phone DMS for the wiring diagram - I don't know where it got to, or if I ever got one. In the wider world, the world has been gripped by the Anders Breitvik trial, but one wonders why people like Abu Qatada don't get equal rights to world publicity to report their vile beliefs. The Norwegians are far too fair and balanced.
   A wanted man in Afghanistan turned himself in for the reward money, hahaha. Ugly moron. The Space shuttle flew its last flight, piggy backing over Washington, before being sent to a space museum.
   It was the 100th anniversary of the Titanic on the 15th, and Liverpool celebrated with an extraordinary festival of giant puppets, and a couple of cruise ships full of relatives and Titanic-fans went across the Atlantic to visit the exact spot. The French election preliminary stage occurred at the end of the week, with Sarkozy losing to Hollande (hooray) and Vettel won the controversially held Grand Prix in Bahrain. What about the meters?

  • 4,792 kWh for the House and 2,794 kWh GSHP, very poor figures, but fully expected after the very cold week with evening temperatures always in single figures.
  • PV has dropped to 3,386 kWh. But the rain has been good for the garden and for the underground reservoirs.
  • Sunbox is working, but I have no figures for them yet. I have had the Tubes installed, and they are working, but only about 2 kWh per day, so far.
  • Ground temperature is 11.3ºC. It has been a rainy overcast week with short sunny spells, and I am relieved it is above 11.

15 April 2012: I didn't do any meter readings because I was in New York for the week. I left the Sunbox disconnected because my repair wasn't quite concluded and I didn't want anything going wrong during the week. While I was there, the Trayvon Martin killing was a big story. Although it happened many days earlier, the story was how an internet campaign had finally forced the authorities to take it seriously, listen to the sound tracks, do some analysis and idict Zimmerman. Phew!

8 April 2012: Another week, and I won't have time to discuss the world news, but I have a note of the week's events and will write them up eventually. There was the election in Myanmar (Burma), the Korean University shooting (in California), the winter weather sweeping through Europe, the Amazon tax scam revelations.  I have no figures for the Tubes yet as the meter is still the wrong way round. For the house, here are the figures..

  • 4,719 kWh for the House and 2,689 kWh GSHP, higher than a week ago.
  • PV is high, at 3,400 kWh. But the Dull week has reduced our annual figures by 50 kWh.
  • Sunbox still out of action. I have had the Tubes installed, and they are working, but no energy figures to report yet.
  • Ground temperature is 11.1ºC. It has been an overcast week, and yes, the tubes have put some energy down, but not much yet. 

1 April 2012: The main news for the Peveril Solar house is the turning off of the Sunbox system until the leak is fixed, and the installation of the Kingspan Varisol tubes. What has happened elsewhere? 
Things I shall cover: Cruddas and Tory corruption, NewsCorp and OnDigital, Balloon on pylon, Petrol panic, Shard topping, Galloway in Bradford, Las Vegas plane, Cruiseship fire, Aung San Syu Kyi election. Meanwhile, I must work on a Powerpoint for a CIBSE conference later this month.
How's about the Peveril Solar house?
  • 4,629 kWh for the House and 2,626 kWh GSHP, both similar to a week ago.
  • PV is up to a record high level, at 3,450 kWh. No complaints there!
  • Sunbox was out of action, until the scaffolding is moved round to the south and the leak if fixed, I won't have more readings from that. I have had the Tubes installed, and they are working, but the Energy Meter is mis-installed, and needs to be re-positioned for it to show what the tubes are earning. Also, a heat exchanger would make better use of the ability of the tubes to capture energy. At the moment, on a warm day, the hottest that the tubes get to is 17ºC before they are cooled again by the pumping liquid.
  • Ground temperature is 11.5ºC. It has been a sunny week, and yes, the tubes have put some energy down, but not much yet. The GSHP has had a very low workload while this summer weather continues.

Saturday, April 28, 2012

Work to manifold lid

27 April 2012: The Manifold is full of water again, even the amount that was bailed out 3 days ago is back in there and more besides. The recent rain has been unusually continuous (although never heavy) and something has to be done. There are natural drainage out points in the concrete case where the ground loop pipes enter and exit, so it seems that drilling another hole through the concrete will not work because the ground around it must be too dense to act as a soakaway.
   I bought a hand pump, but couldn't get it to work, so resorted to traditional methods, i.e. bailing it out with a bucket!

  I am working on making the manhole lid more waterproof. The edge is completely full of coarse silt, washed in from the tarmac, hence there are many many gaps between the lid and the rim, allowing rainwater to enter. The lid is never totally level or tight.
   Something squidgy like Grease or margarine or lard would not last and would make an awful mess. I am trying a dry solution first. I cleaned out the rim edge thoroughly, and have run a thick line of sealant around the edge, and laid a cut slice of bicycle inner-tube along the edge. This gives a dry surface to put the lid onto, and I hope the rubber will remain stuck to the sealant. I put the lid back on, hoping that it will mould the sealant and rubber into a profile that fits the manhole lid exactly.
    It has rained almost all day, but I need about 3 days rain to be sure that it is working. Then, I will lift the lid and inspect.
    It is a great comfort that there is no green or blue in there. The main system is no longer leaking, except at the new energy meter, and that is under control. I need a couple of hours and lots of PTFE tape to fix that.
   Another idea would be to work something into the crack from above. I'm thinking of something non greasy - I'm thinking of getting Cat-Litter, watering it into a mush and working that into the crack. Most Cat-litter is Bentonite, and this seems to be the cheapest method of getting some. 

Wednesday, April 25, 2012

Hit rate on this Blog

24 April 2012: The readership rate on this site continues to surprise me - and it is pleasing. I expected a rise in hit rate after the CIBSE symposium, but really, there has been consistent readership prior to that, usually over 200 visitors a day.
   The CIBSE after-effect is good. The recognition given to my paper shows that there is significance in this technology in furthering the future of Ground Source Heat Pumps - making them more efficient - but there are many wrinkles to be ironed out, and I am finding most of them!
    I feel added responsibility to get this right, and to document everything. I feel that I have proved that high-volume-low-temperature is effective, but I need to find a reliable source of swimming pool panels. The ones I can find by googling are nothing like as good as the ones I am presently using, and I would like to get some into stock as a precaution, in case someone else wants an installation.
PS. David Atkins has told me to look at the website of SolarFocus in Austria, and they have a UK agent, Oxford Renewables! About 100 pounds each.

Tuesday, April 24, 2012

Water in Manifold - Doh!

Photo taken after I had bailed out quite
a lot of the water
24 April 2012: I am really troubled by a new problem. Having solved the leaks up top, I wanted to just check that the underground manifold wasn't leaking, so I lifted the manhole cover over the manifold. I was dreading finding some green or blue liquid in there, revealing that there might be a leak of glycol. There wasn't any green or blue, but there was about half a meter of clear rainwater in there.
    The manifold manhole is a watertight concrete box, and unfortunately, there is a slight tendency in the tarmac at the surface to run water towards the lid, and the lid is not water proof. I never inspected it until recently, and found it damp but not swimming in water. The weather was dry. I now understand why the insulation in there was so soggy and deteriorated. We have now had a month of rainy weather (always happens after a hosepipe ban), and the manhole is half full of rainwater.
   If the pipes are immersed in water, all the effort of solar charging is wasted - the conductivity of water is so good that it will average the temperatures of up and the down flows very effectively, especially if running at slow pump speed. My earlier efforts to insulate these pipes against losses to the air are nothing compared with the rate of loss to standing water.

I seem to have three choices here, and I could use all, or two of these.
  1. Get a core drill and make a drainage hole in the base, although I am worried that with the dense soil that the house is built on, the effect of a soak away will be pretty poor.
  2. Protect the lid from accepting water by sealing the edge of the lid somehow - rubber strip, sealant, clay puddling etc. The tarmac contours around the lid are apparent while bailing, so that much of the water thrown out tries to drift back.
  3. Install a hand pump, so that the manifold can be inspected monthly, and bailed out with a suction pump. I can't install an automatic pump, as there is no way to lead wiring into the manhole.

New Energy meter installed

24 April 2012: The daily meter readings have been lacking Sunbox energy readings since late March. Since I discovered the leak, I took the old Sontex 539 meter and pump off. I have now installed the new Sontex Supercal 440 energy meter (from DMS) with the 531 integrator. I finally got the wiring installed this morning. During the first day of working (very overcast) it records a grand total of 7 kilowatt hours! I still don't quite get how to get it to show me volume and temperatures, but I will get round to that.
    Like other Sontexes, it has just enigmatic orange buttons, and there are tricks like how long you hold them down, or how often you press them - and little in the way of knowing what the tricks are.
   This one has a mains power supply so that it can run 'for ever', but the ones with battery are rather extraordinary. If the 539's battery runs out after 6 years, the entire unit has to be replaced! Why can't they be like a watch or smoke detector, have a battery that can be replaced every few years?

In the photo, the blue cable is the ethernet link from the PV roof to the broadband modem.

Postscript: Of course, it didn't take me long to learn to use the orange buttons. after nearly a year with the Sontex 440, I am very happy with it, although it cost a lot more than its predecessor, the 539.

Monday, April 23, 2012

Heat Exchanger from the stores

23 April 2012: I have obtained a heat exchanger from the school stores and it is about the size of a large shoebox and about 5 kilos in weight - contains lots of metal plates to link the loops. There were a lot to choose from, but many of them had soldered on ports or seemed too small.  This one seemed to be about right, has 4x 22mm ports, (1 and 3 for the solar tubes and 2 and 4 for the ground loop).
    I will need to get a pump and another thermostat, or a solar controller to operate the link to the ground loop. I have plenty of spare Celotex with which to build a box to put it in - the skips at our department are bulging with off-cuts.
   The tubes system is working quite well (consistently), but I estimate it is only averaging 2-2.5 hours a day which is only about 2-3 kWh per day. It really needs direct sunshine to activate. But for a proper installation, it's clear from discussions with Jason (the plumber) that a circuit with a heat exchanger would work better. In another house in another place, I would try it with a directly south facing array, with the tubes vertical, and probably 4 times the number - 60 tubes, or 8 square metres for starters. This would cost more than my hand crafted Sunbox!

Saturday, April 21, 2012

Restart the Surya system

21 April 2012: I have fitted the non-return valve, checked again for leaks, topped up the system, and set it going again. Fingers crossed, etc etc. I will watch it for a few days, check the exterior frequently, sort out any remaining leaks, and then re-insulate all the exposed pipes. I had to make a decision to move the Ground loop sensor from the pipe going down to the pipe going up. This is because when the GSHP has finished work, a lot of cold liquid goes down to the ground before the thermostat realises it is time to stop. Putting the cold sensor on the up-coming liquid will mean that the pump will only go when there is a delta-T between the deeper ground temperature and the Sunbox. Fewer hours, but less cold liquid sent down.

   I notice that the new arrangement is, like the tubes, more intermittent than before, although that could be due to the weather. There should be less wastage of pumping time.
   I am sorry that i will not be able to read easily the temperature of the liquid coming down from the panels. Perhaps I should invest in a conventional solar controller, that is able to show three temperature locations, so I can see the up and the down temperatures.
      It is really good to see it working again. However.... the Energy Meter needs to be re-connected, the new one that I bought in January but didn't fit. Then we can resume taking readings again!

Surprise Award at CIBSE/ASHRAE

19 April 2012: More about the CIBSE/ASHRAE Symposium. After my paper, there were a few more, then a break for lunch. In the afternoon, we had two and a half hours of plenary papers, followed by a post conference drink in the basement refreshments room.
    I nearly left early, but got into conversation with people interested in my Solar Earth Charging system. Just then, we were called to order and the President of CIBSE, Andy Ford, called the group to order and gave a little speech of thanks to those who had attended, organised, refereed or delivered papers.
    Then one of his colleagues declared the result of a popular (audience) vote for the best presentation of the event... and I could not believe my ears on hearing "David Nicholson-Cole with his paper on Domestic Solar Earth Charging"..... !!! I was so surprised, I didn't know what to do with my half eaten biscuit and half drunk beer (you can see them to the right of the photo!) Fortunately, I handed someone my iPhone to take a quick picture.
   So I am the proud possessor of a £50 book token at the CIBSE bookshop, but more importantly, I feel that this idea and the simple technology behind it has finally got some recognition.
   Speaking afterwards to someone who had voted for it, he said it was the directness and compelling simplicity of the idea that had captured people's interest. The principle of solar earth charging may even be obvious to everybody in someways, but someone still has to have the courage to be the first to try it for real, on a real building. To present the topic as a computer modelling exercise would still leave too many unproven questions in the air. The fact that I have 2 years of data collection and a working system that has produced results is compelling evidence that the idea is worth taking further - and they liked the fact that the circuit was so very simple, no tanks, no heat exchangers.
(Photo by Kishore Bhattacharya, who had travelled from Calcutta and presented a paper on "Fast Tracking Energy Efficient buildings by separating the Building from the Occupants - a New 21st century approach")

CIBSE/ASHRAE Technical Symposium 2012

20 April 2012: The CIBSE/ASHRAE Technical Symposium 2012 was held on 18-19 April at ICL (Imperial College London).

How did I come to be there? Well, last winter, one of my ex-students (who had done a dissertation about the Peveril Solar House) suggested that I send in an abstract. I did that, and it was accepted, so I had to send the paper in sometime in early February. I had to complete the Powerpoint by early April, and of course things had moved on a bit with the installation of the Evacuated Tubes and the leaks in the original Sunbox. The comparison of the two is going to be of interest to engineers, once I get the energy meters working.

I couldn't get there on the 18th due to the New York trip, so I travelled down by train for only the half day of the 19th. I had to give my 18 minute presentation almost as soon as I arrived at the ICL building. This is the first time I have had to present a refereed paper at a symposium (yes, surprising, but that is because I have been on a Teaching-only contract for 22 years) I was extremely nervous in the presence of Building Services Engineers, and the paper before mine was very technical.

Here is a PDF of the 20 minute presentation
I thought it went down OK, but always feel humbled when others present such magnificent tables of data logged figures, computer modelling and analyses etc. Many of the people here were presenting the results of PhD work.
   There were some questions after, with plenty of interest in my project. Maybe because I am used to presenting to architectural students, my PPT was more colourfully illustrated, and I conveyed my self deprecating humour a bit, including pointing out the problems I had with the recent leak, and comparisons between the Sunbox and the Evac-Tubes.

ASHRAE is the American version of our British CIBSE, and it was great to see so many international delegates, from the States, but also from other countries, including India. Click the logos above to transport to their websites.

One of my final point was about the time-lag of acceptability of ideas like this, perhaps 30 years. I referred to the Catalytic Converter for cars and the Safety Elevator for buildings. The president of CIBSE, Andy Ford said that the idea had been around since the turn of the century, so we are perhaps halfway through that period. More real installed case studies are required for it to become commercial.
(see the next Blog entry which is the story of how my paper won the audience vote)

Wednesday, April 18, 2012

Back from New York

 18 April 2012: I have returned from a week in New York with some architectural students, and it was great fun. We saw most of what you could see in just 6 days, and more perhaps. NYC has more museums than London, and of course, we were there to see skyscrapers and other great monuments (like the Brooklyn Bridge and Statue of Liberty).
Above, outside the Guggenheim Art Museum by Frank Lloyd Wright 1959

Above, outside the Whitney Art Museum by Marcel Breuer. Apparently there is another Whitney being built somewhere in Chelsea (NYC)

Above, The Hearst Tower in 8th Avenue by Norman Foster 2007, the greenest skyscraper in NYC, LEED Platinum rated.

DNC and students in a mirror-ceiling at the Skyscraper Museum, Battery City
Oh yes, don't forget the Statue of Liberty. I've been to NYC 3 times before, but this was the first time I had made it over to the island.
Trick photo... the background is a green screen and
they photoshop the ESB into the background

Do I enjoy my job? You betcha! 
Oh and I was wearing my 'Sustainable Tall Buildings' sweatshirts all week.

Sunday, April 8, 2012

Repair progress 8 April '12

8 April 2012: Well, I seem to have completed the repair, but I am off to New York for the week starting Monday, and need this system to run for a day and have it observed closely. So the system is decommissioned until I return. My worry is that the level is never good in the high top up bottle, and I wonder if there is another leak somewhere, e.g., in the ground loop manifold. I need to open the ground loop manhole, lift out the insulation and check for traces of coolant.
   There are no leaks that I know of in the above ground system. While running the heat pump and the tubes ONLY, there are no drop-offs in coolant level, which makes me think there is no underground leak. But when I include the Sunbox circuit, the top-up bottle keeps needing a top up even though there are no drips coming from anywhere.

Having run the system for a while and seen no leaks, I have put the right hand sun box front panel on.
Now, the centre small panel and mini-roof are in place.
 Now, both the front panels are on. I take the dog for a walk and enjoy the view. Everything seems to be working, apart from this worry about the top up bottle needing so much water.
 Mr Makita is an ever present help.
Take a rest after work. 

Progress with Sunbox repair 7 April'12

7 April 2012: Well the plumbing of Saturday has been indoors, the system is now topped up with new liquid, and I hope it will all work on Sunday when I turn it on in daylight. I don't know why I have been so reluctant to use compression fittings in the past. For years, I seem to have been set on soldering everything. Maybe, I was doing it because it is cheaper.
   It is so much of a nuisance when you need to do a repair, as you cannot heat out an old soldered joint if there is liquid inside, and also, glycol has a peculiar ability to find its way out of the slightest fault with a soldered joint. I am using PTFE tape for most of my new joints instead of putty, its clean and dry. The picture above is a sort of 'Still Life' for plumbing junkies.

I now have a 12 litre expansion bottle in the circuit immediately connected to the Surya Sunbox panels, even if the valves are closed. There is also a pressure gauge to keep an eye out for leaks. The bottle is held up with wires at the moment, but if the plumbing works, I shall insulate all, and will build a proper supporting bracket from spare aluminium. I'm not sure how much of the air I should let out of the balloon inside, but I will read the pressure gauge and either let more out or pump more in, depending on performance. 

Saturday, April 7, 2012

Progress with Sunbox repair 6 April

6 April 2012: Repair work on the Sunbox is progressing. The leak was coming from the plastic piping between the two sets of panels, and it is impossible to repair the old Tee-Joint. I would not be able to obtain a replacement on a bank holiday, and even if I could, I would not be able to re-insert it. The space is too small and it was a nightmare getting it in in January 2010. So for the new external piping, I have taken the risk of getting 40mm waste drainage compression fittings - normally these work with gravity, so aren't used to pumping pressure. They are polypropylene, the same material as the black panels, so they should be strong enough. The Tee is designed to be helpful to gravity, so it is asymmetrical. The asymmetrically helped as the vertical centre pipe is not precisely central - it now fits perfectly. Our system is pumped, so this small rightward bias will not matter. The fitting is shorter than the previous, so it is easier to fit in, although I might get some replacement rubber hosing (longer and thinner skinned) before finally closing everything up. 

The previous external piping was using the 40mm compression fittings for ground loops. These are exceptionally durable and would be suitable for external use. However, not long after these were installed in 2010, I made an aluminium and insulation capping that protects them from frost and ultraviolet. These items are so bulky that I would not be able to replace them - they had to be cut out laboriously with a hacksaw.
The previous external capping has been rebuilt now. It provides weather protection to the external pipes, but is now much more easy to lift off for future maintenance, even from a ladder.  The bird spikes have been effective, there isn't a trace of bird shit on the capping or the area around it.
(to compensate the poor birds, we are fanatical about feeding them, providing sunflower seeds throughout the winter, and bit of waste meat or fish throughout the year. If the cat won't eat the waste, then it goes to the birds.)
So this is what the Sunbox looks like, seen from the field at the rear of the house. I now have some internal plumbing to do before these can be restarted. People walking past the house now have an answer as to what is inside the Sunbox! The external piping is done as best I can, but the loft space requires an expansion bottle, pressure gauge and drain point. 

Friday, April 6, 2012

Repair work starts

5 April 2012: Work has started on the repair of the Sunbox system. The scaffolding that was used for the Varisols has been moved to the south wall of the house. The only way to tackle this is to get up there and get in.
Well the fronts have all been taken off, and I was somewhat surprised at how well it was built - in that it takes some getting off to remove parts! so many flashings that have now glued well and truly, and have to be cut to get them off. Perhaps I should put things back so that it is all more disassemblable, a bit like the fairing on a motorbike.

Here is a close up of the leak. It is not leaking from the panels, which is a great relief. Its leaking from one of the joints in the 40mm plastic piping, which is a replaceable part, I hope.  (PS apologies for the slightly messy hinge detail, I kept having to modify it slightly to get the front to fit tightly.) I'm not sure how long it is all going to take. Starting something on the Thursday is a bit risky as some suppliers etc will be on holiday until well into next week. 

Wednesday, April 4, 2012

Tube observations

3 April 2012: After a few days of watching the Tubes working, I have some observations about them. This is an expensive way to learn, incidentally. My little One-square-metre of tubes should really be facing south as they do little when the sun isn't shining. The arrangement of East+West may be OK for water tank heating, but for ground heating, more tubes are required, and they should face south.
  The context here is of heating without using a Heat Exchanger - there is a solar controller setting for heating swimming pools, and our ground is like a very large cold swimming pool.
  I am still convinced that Tubes could be used for heating the ground, but there is a matter of 'critical mass'.  The size of the array needs to be larger - that seems obvious, but how much larger? Well at the moment, the array warms up, and the pump starts, and at the slowest pump rate it flushes out all the warm liquid in a couple of mins. If the flow total only 200 or 300 litres a day flow, then the pipes should be very narrow to give that warmed liquid a chance of getting down to the ground loop. I fear that some of it sits in the pipes within the house, dependent on insulation, probably getting more heat from the house than from the tubes. If the sun is shining, the 1-metre long array flows a few minutes and nearly meets a steady state - depends on how cold the ground loop has been - but the flow of incoming cold liquid forces down the temperature of the rooftop sensor too quickly, until the pump turns off.
  The current settings are that the roof sensor has to be 8 degs higher than the ground, then it starts, and runs until the ground and roof sensors are equal.
   So would the critical mass be 2 metres of tubes? Would that be enough to keep the pump flowing without turning off? I think not. More are needed! There must come a point where the tubes alone could do it without a heat exchanger, but perhaps it would need to be be 4 metres of tubes (i.e. 8 square metres). This is difficult to model on a computer, and it seems that a live installation is the only way to test it so that you are absolutely sure.
   If the length of the array is enough to keep the flow going, then one could manage without a heat exchanger, because the warmed liquid would have time to get down to the ground. This number of tubes would be expensive.
  Standard tube manifolds are 1 and 2m long, so for a start, a minimum system would have to be the larger size, perhaps two of them. Very expensive.

A heat exchanger will be ordered. This is usually for when you have immiscible liquids that must transfer heat, such as glycol through the solar panel and swimming pool water in the other loop. In our case, its value would be in thermal inertia, enabling the tube loop to work continuously. The loop that takes the heat to the ground would become intermittent, drawing heat down, but turning off when that was achieved, without having cooled the block enough to turn off the tube loop. There is only so much you can do with 2 square metres of tube, but this is a way of getting the warmed liquid to travel further down to the ground loop to where it is needed. 

Monday, April 2, 2012

Tubes, Heat Exchanger, Scaffold

2 April 2012: The first of April provided the best possible conditions for testing the new tubes - cool air temperature but very sunny. I have insulated the pipe at the end of the array, and kept an eye on its operation. I am sure it will work better in the summer. When the heat pump works, the tube array does seem to suffer from 'thermal surprise' when liquid at 5ºC or less is delivered to it after the GHSP comes on.
   The System 23 (swimming pool mode) allows for it to switch on if the delta-T is 5 degs, and it continues working until the delta-T reduces to 2 degs. This is a good feature which the existing AKO (used on the Sunbox) doesn't support, although on the AKO, I can provide the equivalent by programming in a hysteresis figure and a time delay before switch off. It is working quite well today even in overcast conditions, and I wish the energy meter was installed the right way round so I could see what we are capturing.

Heat Exchanger
It seems that for satisfactory working over the whole year, the Heat Exchanger is going to be needed, and I will try to work with an industry standard one instead of making one from pipes, box and sand. Jason has recommended a Thermofin model. Looking at the flow rates, the smallest would be sufficient, although larger would have more inertia.

The scaffolding is due to be moved around from the east wall to the south wall as there is too much danger in trying to repair the sunbox from a ladder. I've been up there, but even to exert some force on the jubilee clips requires force, space and angle, which would be dangerous. The fronts need to come off for best access.
   One thing I have learnt - my home crafted Sunbox is far more efficient than a commercial panel! It has great thermal inertia, and my main mistake was to rely on the old expansion bottle. The old one was sufficient for temperature variations from -5 to a maximum of 12ºC, whereas with the Sunbox, the variation is from -5º to about 30º, hence the need for a bottle. I have purchased a 12 litre bottle. I have asked Richard Pearson to relocate the scaffolding.

Sunday, April 1, 2012

Intermittency and Insulated cap

1 April 2012: The Tubes system is working (with the swimming pool configuration) although it is very intermittent. the tube manifold warms up in the sun and starts the pump. A very short while after that cold liquid goes up, the Delta-T closes and it turns off. But the Sun is shining, the air temperature is very cold (freezing overnight, perhaps), and it is an ideal time to observe the operation. So the tube sensor warms up quickly and runs liquid for another minute, then closes. This intermittency is a problem which could be solved with a heat exchanger. However, I would be interested to find out if we still get an energy capture even if it is intermittent.
    I have noticed that as the solar altitude increases, the intermittency is reducing - i.e. the heat arriving at the tubes is almost enough to maintain the flow (at slow speed) with cold liquid coming up from below - the period of action before it turns off is getting longer. Logically, the slowest pump speed is preferable, to allow the tubes manifold to stay hot for longer.
Tubes fitting on the roof between roof lights
I want to insulate this end. It was insulated at the Ecobuild model
    I cannot know if energy is being captured in significant quantity as the energy meter was fitted the wrong way round, so i will have to turn the system off and turn the meter round. It should be on the flow to the tubes, not the return. This isn't the fault of the guys, it's just that they didn't ask which way round it should be.
    Also, I noticed at the Kingspan stand at Ecobuild that the ends of the array had insulated cap-ends, and this insulation does not. I shall either have to ask KS for some cap-ends if such a thing exists as a manufactured item, or make one myself from insulation and aluminium boxing. This may seem small, but there must be a system loss on cold days from having exposed metalwork.

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