Friday, April 30, 2010

More thoughts on Interseasonal Charging

30 April 2010: Chris Wood says that for the mass of clay that our boreholes reach, you can continue pumping heat down there and we should not be alarmed if the temperature reading does not rise dramatically - the whole point of this experiment is to 'move the heat outwards'. There is so much thermal mass that is building up nicely, but very slowly. We can guarantee that this soil will never chill, and that is an achievement in itself.

The only way we could have a significant rise in the temperature would be if the ground was fully enclosed in a swimming pool size box of rock or earth, insulated by vast amounts of polystyrene. This would cost vastly more than the boreholes we now have, so you have to balance off the advantages and disadvantages.... and would it be enough to get through the winter for a house of this size?
   Even the vast storage water pond at the headquarters of Renewable Energy Systems, Beaufort Court has the top heavily insulated with half meter of insulation, but is uninsulated below to permit surplus build up of heat to warm the soil below, without distance limit. See the Beaufort PDF. Image from their website.
That prevents it overheating, but also provides an additional source if the water source is too cooled in winter. They claim that this is a 'World First', and I have been there and seen it myself.
    If we ONLY had heat in the summer and had to store it all winter, then Interseasonal charging would be vital, but we have enough evidence from the cold days of March, and from the photovoltaic statistics to see that there is plenty enough winter sun (with our vertically oriented panels) to top up continuously throughout the winter.

Summer performance - some things different from expected

30 April : Midday Observation with sun shining :-
  • Air temp in boxes 32ºC, 
  • Glycol going down to ground, 23ºC, 
  • ....and returning back up at 12ºC. 
             That's charging!

Summer Performance - the unexpected
I have also realised that my intentions for night air charging are possible, but unnecessary. When heating is going on (late March/early April) the boxes worked at night because air temp was better than glycol temp - that was helpful. Now that it is summer (we hope it stays that way) I have noticed three things:
  • Morning Startup: The sunboxes don't start up by themselves on cloudy days, until the heat-pump lowers the glycol sufficiently : good! this is saving pump power and the heat we would get down would not be worth the pump power. On cool days, the boxes come on when GSHP demands, support the GSHP in Realtime while it does a water heating cycle, then they turn off shortly after the GSHP goes back to sleep. This is good! On sunny mornings, the cold sensor is at Room temperature, say 22ºC, so they will start up by themselves if the Sunbox temp rises to 27ºC. (Startup is dependent on the temperature difference - I am finding that 5 degrees C is pretty well perfect balanced - ensures that pump is not on for excessive hours, but when it is, the heat being claimed is worth getting.).
  • Day gains-Night gains: The amount of power we get on sunny days is sooooo much that it's not necessary to chase after small gains based on night time air temperatures (but I am willing to change my mind later in summer, depending on the datalogger finding.) Night time action only occurs if the GSHP demands realtime heat. There's no point in interseasonal night charging.
  • Temperature reversal : The earth below the house is getting 8-16 kWhr per day. This disperses well, so there is no danger of chilling. At the end of a day, the temperature below is quite acceptable, sometimes higher than the morning temp. e.g. before we did this, the evening temperature might be 5.8º but in the morning it had recovered somewhat. The reverse is happening now. At the end of the day when we put heat down during the day, but draw little up, the temp is high in the evening perhaps 12.8º, but in the morning, this heat has moved outwards and the stable temperature (stable meaning that for 12 hours, no heat in and no heat out), it is about 11.8º. 
Forget Overheating risk
If this is the case, there is no need to have louvres top and bottom to 'flush air through' - this was thought essential for summer night time gains. The daytime performance is better if the boxes are very airtight. The boxes never overheat - I was worried about this, and the top louvre was intended mainly to meet the overheating risk. However, the hotter the boxes get, the quicker the pump pulls heat from the boxes and buries it, keeping the sunbox air temperature below 40ºC (about the same as Baghdad in summer, or your blood temperature). The only overheating risk is if the pump is not working, but in this case there is an expansion bottle in the loft to cope with swelling of the liquid mass. There are cooling louvres top and bottom, in case I stop the pump for maintenance, or try running the GSHP for a week with sunboxes turned off, for testing purposes.

    Progress report 29 April

    29 April 2010: Sorry if this is just a list... but it's useful for the progress record:
    • Sunbox2 PV: The photovoltaic panel with the crazed glass now has aluminium framing all round the edge and a 4mm polycarbonate over sheet. Much heavier now, but safer, and waterproof. 
    • Sunbox2 construction: Work has started on the aluminium sections for Sunbox 2, all drilling being done by the Makita drill. But I hope to get a new chuck for the desktop press drill tomorrow.
    • Electrical: I want my relays to be able to turn the loftpump Off when the GSHP is in a heating cycle, and after asking around a bit and of testing, I discovered that the Omron relays I already have are dual purpose, they can be in Normally On mode or Normally Closed. i.e. when they come on, they can turn something else off. So I am buying two more relays for use in the loft.
    • Datalogging: I have begun to string more wires down from the loft area to the utility room, to turn relays on and off and it's getting worrying how many wires there now are. The Datalogging wires add to the visual confusion of course. I will have to get some more cable ducting to put it all into.
    • Pump performance: I have been wondering if the external pump that pushes water round the underfloor system is necessary. It is just above the GSHP and uses 130 Watts at slowest speed and runs most of the time. It would use 3kWh/day just for that pump if left on 24 hrs. I consulted the manual, but it does seem necessary. The under floor system is using very small gauge pipes, and two manifolds, and the pump is necessary for monitoring the current floor temperature. The one inside the heatpump only comes on when actual heating is required.

    Wednesday, April 28, 2010

    Reverse cycle cooling enquiry from P. King

    28 April: I had an email from a GDL friend, Paul King (I think he is in the USA):
    Question: "Hi David - very interested to see what you were doing with sunboxes! Could an additional string to the bow be using an additional air source heat pump to charge the reservoir during summer possibly using off peak tariff  electricity (cooling the house when too hot, or the surroundings when temperatures are mild), or using excess hot water from solar hot water system during day."

    Answer: Hi Paul, Thanks for having a look through the blog!
    The essence of our idea is to use the [free] solar heat to charge the earth - and the pump is mostly driven by power from the PhotoVoltaic roof. So for us, 'off peak' is in the middle of the day - when the roof is able to drive many of the appliances in the house and not import any electricity from the grid. We certainly wouldn't want to expend the running cost of an air source pump (air conditioner) to do what can be done for free.
        If we were in a hot climate, we would have considered a reverse cycle heatpump, but ours is for heating only. The thermal stability of the house is such that we would never really need summer cooling - and if we did, the first thing I would do would knock up some aluminium sections to make Shading devices for the south facing windows - a passive method, not an active one.
       I originally intended an off-the-shelf solar thermal panel, but this produces heat at a much higher temperature for water heating - and we can manage with something cruder as we are quite pleased to get heat in the 15-25 range (Celsius). 'Sunspace' is also a method of capturing heat, so think of our boxes as miniaturized sunspaces.
        Actually, my enthusiasm for plumbing leads me to think about the idea (if cooling was needed) of bypassing the existing loops to a heat exchanger, so that the ground loop (at a temp. averaging 12 deg C) could be exchanging heat with the underfloor heating loop, making it a cooling loop.
       We are not having solar thermally assisted hot water, as this would confuse the readings that we are taking of the improvements in performance of the heatpump as a result of the earth charging. The hot water is virtually free as during summer, the PV roof produces such a surplus that no imported power is needed during hours of bright sky.
          Hope you (and any other readers) can post a comment on the earth charging blog. thanks...

    More discussion with Dr C Wood

    28 April 2010: More about the interesting discussion with Dr Chris Wood in the Uni...
         He has been working with Roger Bullivant since getting the PhD and is also researching interseasonal heat transfer, using the heat building up under rooftiles to store in the ground. (Unfortunately no blog about that.... ). If he is willing to tell more, I hope something about it can appear here, or it will appear in journal articles later.

     He provided me with a number of better quality Thermocouples to replace the ones we now have, which should give more accurate results with the datalogger. One of these is 21m long, to go right up to the sunboxes. These have better quality welds at the tips.

    He commented on my 'bottle-shape' idea for the boreholes. Although it is broadly right, there are likely to be bands or strata of different conductivities or thermal capacity in the average soil, so if you could chart the undisturbed temperatures all the way down, the bottle would have narrower and wider sections as it went deeper (a bit like an old Coca Cola bottle). For our house, all we know is what the drillers told us and what we knew from the British Geological Survey, which is that it is mostly Marl, all the way down - just about perfect for deep boreholes.
        We also discussed briefly whether there is a case for patenting the sunboxes, and if it is worth it or possible - I have not thought this possible earlier when the idea was only about using the black panels, because these ideas are well known. But there is a case for trademarking the technological solution, and there is also a case for just being in front of the others, and doing it first. I also had information from another expert that for patenting I would have to delete this blog and ask everybody I talk to from now on to sign non-disclosure agreements!

    Pumpflow questions: C Wood

    28 April : Had an interesting discussion with Dr Chris Wood in the Uni.  The main topic was about pump flow.
      He praised the decision to put a 3-port solenoid valve (Danfoss) to divert ALL the glycol to the sunboxes when the thermostat commands, because it will make it far easier to identify the contribution made by the sunboxes. I said that if it drained as much heat as was available more efficiently, the pump in the loft would be turned off by the thermostat until the sunbox air temperature increased naturally.
      He did question whether the pump in the loft should be running when the GSHP is on. At the moment it is necessary to divert a fraction of the glycol to the sunboxes, while the other fraction goes down below. The loft pump is absolutely necessary for pumping heat down to the ground when the GSHP is dormant for long hours of the summer. But what about when it is working?
       Once we have the 3-port valve, all glycol goes up to the sunboxes. The loft pump is merely speeding up the flow sent to the sunboxes, and would this be too fast? Do we need the 'parasitic energy consumption' of the extra pump if it is not helping the process? Would it be better to have it turn off when the heatpump's water pump comes on? (and would this be a restriction on the flow?) More importantly, does it confuse the algorithm inside the GSHP controller which expects glycol to move at one speed when (unknown to it) the glycol is arriving faster than expected? I am hoping it is smart enough to recognise the watt-hours moving towards it, and adapt accordingly. The GSHP has a manually settable variable speed glycol pump (set to highest speed). The GSHpump just seems to work for fewer hours or minutes if the heat coming in is good for its needs.
      In the same vein, do we really need the external supplementary pump for the underfloor circuit? Does this confuse the controller, or cause too much circulation? I can disable the external underfloor heating pump.
      The Danfoss is now in stock just near the University campus, so I will try to collect it today.

    Gravel as an Energy Store

    27 April : I am glad to see the article in today's Guardian, reporting on ideas from Isentropic to even out intermittent production of renewable technology by storing spare energy in vast silos of Gravel.
        This isn't simply storing heat like in my project, it is far more extreme. One silo of gravel might be boosted to 500ºC, and another cooled to -160ºC using a powerful heatpump. This is equivalent to pumping water high up a mountain. The equivalent to letting the water down again is to allow the silos to exchange temperature, somehow generating electricity in so doing by using the same [reverse cycle] heatpump.
      I can assure all readers of the blog that I have no intention of heating the clay under my house to 500ºC. I am trying to prevent it cooling, but it would take a truly profligate lifestyle to use so much heat that my deep ground fell to minus 160 degrees!

    How deep are the Boreholes?

    27 April : I have been trying to find ways to demonstrate the proportions of the house and the boreholes beneath the house. This is for the poster for the Open Day on 16 May. The holes are 48m deep, but of course, what matters is their 'reach', i.e. how much of the soil around will be thermally responsive to our cooling and heating.
        Initially, one imagines deep Cylinders, but in all likelihood, the shape is more like a tapering Bottle shape.
        Near the ground surface, the ground temperature varies with the seasons and the days, so only the volume immediately round the pipes is relevant - so it looks like the neck of the bottle.
        As you go deeper, the radius of active soil around them increases, perhaps to 3.6m, so it looks like a Bordeaux bottle. As it deepens, it widens to something like 5 metres depending on conductivity, the delta-T that we are working with. The deeper parts are no longer affected by the seasonal changes in the upper layers. At the bottom of the borehole, the bottle-shape is likely to be domed at the bottom.
      This model is absolutely to scale (using ArchiCAD 3D), but it's a perspective projection, foreshortening the bottle-shapes.
      The model also assumes consistent conductivity. All we know is from what the drillers told us, who reported that for the entire depth, it was pretty consistent 'Marl', a mixture of dense clay and broken limestone - a glacial mixture. It sounds right, there was a huge amount of clay slurry coming up, and much of it is still splattered on the wall. If the density varies, the bottle would have thin and wider zones, indicating the range that is affected by our 'interfering' with the natural ground temperature.
      The GDL model tells me that the volume is 3600 cubic metres which amounts to about 8,000 tons of dense conductive marl.

    Starting work on Sunbox 2: Mr Makita gets a virtual hug!

    27 Apr : Work began on repairing the PV panel, fixing aluminium angles to the perimeter. Tomorrow, I will be coating the front with 4mm polycarbonate.
      I don't have a press drill at the moment as it is being repaired. But for work like this, I am alternately drilling metal and screwing with self tapping screws. You cannot beat a Makita cordless combi drill driver with torque control. This has a keyless chuck, two speed gearbox with fine speed control in the trigger, adjustable torque clutch (so you can't overtighten), mode switch between drilling, screwdriving and hammer drilling. Two rapidly interchangeable power units and a fast charger. It's wonderful and I would like to give a big hug to Mr Makita who designed this!
       I treated myself to one of these in March. I just wish-wish-wish I had the smartness to get one earlier - one of these in December and January would have saved so much time and made all the fixing of self tapping screws so much easier and more precise. And when you have to do anything with wood, you can invest in self hole-drilling screws.
      One of the delays with the first sunboxes was my search for the right type of screw. 10x1/2" Panheads were good before, but they had a blade head (easy for hand screwdriving, hopeless for Drilldriver). And I couldn't get enough to do the whole job, and the next lot weren't good enough either, so the Surya Sunboxes finished with 3 or 4 different screw types. Some were replaced, but the replacements had to cut different threads... hours wasted.
        This time, I was able to go to Screwfix and immediately pick a good quantity of these Prodrive Stainless steel 10x1/2" self tapping screws, for less than the price of a coffee. With their very broad but flattened domeheads, they are perfect for cutting thread and biting firmly into 3mm aluminium angle.
     Anyway... enough of Minutiae. Back to the design in a few days time.

    Tuesday, April 27, 2010

    Inspiration from the Post-it-Note!

    26 Apr :  I read today about the 30th birthday of the Post-it-Note. The inventor Geoff Nicholson worked for the US stationery giant 3M. It was a good way to get rid of some not very effective adhesive and lots of scrap paper. Now it is in every household.
       He provides a great quote "Research is the transformation of money into knowledge. Innovation is the transformation of knowledge into money." Another one worth remembering relates to his struggle to get the invention noticed, "Every great new product is killed at least three times by managers." .... so you have to persist.

    Platinum Analogy: Catalytic Converters

    26 Apr 2010: Had a long discussion with my dissertation student, Robert, today. We are trying to resolve his topic as the hand-in-date is getting very close. the most important thing is to get the Abstract right, because the rest of the dissertation can be built rapidly if the structure is completely agreed.
       When he set out, the project was in its infancy, and during that time, it took some misdirections (e.g. the plastic balls), and it suffered some delays (bereavement, pressure of work at Uni, waiting for deliveries, plumber etc) So he also had contingency plans for the topic in case I never completed the project - this would have been mainly around Photovoltaic and Feed-in-tariff policy. Anyway - there is now enough in the Sunbox project to build a dissertation around.

    In discussing the long term future of Sunboxes, we realised that government policy can have a major effect on the prospects for a product. Clearly, legislation cannot be applied to products that do not yet exist. But if they come into being and are compellingly useful, the first stage is for them to be a luxury or an added extra. But if they are compelling enough, they can become a necessity, and even a mandatory requirement.

    In trying to convey the potential of Sunboxes to the  reader, we realised that a useful analogous example would be the Catalytic Converter. This reduces the emissions from car engines, and is part of the exhaust system. It was originally an experimental invention from the early 50s, but did not take off. The US introduced tough emission regulations in the mid 70s when unleaded petrols began to be used, but still did not take off fully. They contain Platinum, a metal more valuable than Gold.
    Without regulation, these would be difficult to sell to purchasers merely because they reduce emission - goodwill is not enough. But regulation can change things totally, which can make them universal, and would result in a reduction of manufacturing cost through volume production.
    Since the turn of the century, these are installed in most cars, now that regulations in Japan, Europe and the US require them. So, even a small car will have one of these.

    If GSHP emerges as a key technology for moving building design to Carbon Zero (based on the fact that they can use renewable electricity), I still believe from my personal experience of a GSHP that the COP will never be good enough to reduce their power consumption to a level that is satisfactory. Someone will demand improvements!
        If we can prove that Sunboxes, an inexpensive add-on, can improve the COP by a third or more, then there would be a good cause for them to be a 'required component' of a GSGP installation.
      How much does the benefit need to be quantified precisely? Or would people just accept that they are 'A Good Thing'. Catalytic Converters have been tested, and have quantified data about them. It's become clear that recent methods of calculating congestion charge, parking charges and road tax are based on emissions, not merely on engine size.

    Relay cables to the GSHP

    26 Apr : Both the Omron relays purchased last week are now installed. One connects to the thermostat and comes on when the green light comes on. The other one has a thin cable that trails around behind and over and into the GSHP cabinet. It has to connect to the water pump that works the ground loop, the specific indication that the GSHP is activated.
       I first thought I might have to cut the main cable to the pump and insert a small junction box or 'chocolate block' but I discovered that the electronic board behind the user's control panel contains a number of outputs, one of which is the pump for the ground loop - so it was easy enough to connect in the new cable.
        Now I have to work out how to connect the relay to the DT500 datalogger, and that's another little job done!

    Sunday, April 25, 2010

    Forest, and Ways to use PV power from Sunbox 2

    24 April : During the final home game of Nottingham Forest (winning 3-0 against Plymouth), I couldn't help drifting off a bit thinking of the earth charging project. I was thinking about creative ways to use relays now that I have discovered them!
       I think that if I use the Sharp PV panel with its maximum of 180w (somewhat reduced due to the polycarbonate cover and the crazed glass) with a regulator, car battery and inverter (as illustrated), I can use the 230vAC to run the two water pumps that will be in the loft.
       This makes sense because the pump workload will be higher when the Sun shines more strongly, so it is appropriately that this should be when the supply is enhanced. In reality, the power of the pumps cost us nothing, as our PV roof does so well whenever the Sun shines. However.... this is a research project and I want to test everything out.
        If I find that the car battery is always fully charged, I can run an extension into the house and run more appliances from it, so long as I don't exceed 600 watts. I will not bother with 12v pumps etc, as these are difficult to find, noisy, run too fast, and I might later want to run the Sunbox without a PV panel.

    Saturday, April 24, 2010

    Aluminium, Polycarbonate and bicycles

    23 April : The Aluminium and the Polycarbonate have arrived, for the Sunboxes Mark 2. 
    However... we have family staying, and the garage is full of bicycles and the decks are being cleared for my wife's birthday party on Sunday - so the radiator and the PV panel are in storage.

    The work on the new sunbox cannot really start until next week. More family are arriving on the 24th, and there is a Forest match tomorrow.

    During the afternoon, my daughter Sophie and I went for a 30kilometre bike ride - some things are more important than mucking about with drills, screwdrivers and wire! Quality time! We went to Attenborough Nature reserve and back, along the Trent.

    I rode on my son's bike, a 'Specialised', and my daughter has a similar bike - so seemed like an easy ride - and during the afternoon, my son took my bike (a 30yr old Dawes) and gave it a thorough service.

    Hour timer added, and relays for the DT500

    23 April 2010: The sunbox system now has a Curtis 700L 'hour timer' underneath the thermostat. This (illustrated Left) will only display when the sunbox pump is on which will make evening readings a bit difficult. But overall, it will be useful to know how long the system is running for, and comparing that with the volume transmitted and energy harvested on the same day.
       The DT500 will also record the times when the pump and the GSHP come on and off. This is important because the sunboxes do not come on by themselves unless the GSHP starts up in the morning. This is because the pipe to which the Cold sensor is attached is inside the house and reaches room temperature overnight, about 21º. And during the early hours, the sun is still too far in the east to heat up the Warm sensor in the sunbox to 5 degrees more than the Cold pipe.
        And during a cold day, the sunboxes turn off quickly, but come on again when stimulated by the GSHP. Similarly, the reason that the sunboxes are often working at 9 or 10 at night is that the GSHP is now doing a heating cycle (because evenings are cold) and they come on if there is residual heat up above (perhaps due to warmed up brickwork.) I would like to have been able to paint my brickwork with Matt black paint, but wasn't prepared to do this when the project was in its construction phase - in case it all had to be taken off.
      I assumed that the Datalogger would be able to detect a 230v AC ON/OFF, but it seems that this is not possible. So Dr Chris Wood tells me I have to take a 230v AC lead from the Sunbox Pump and another from the water pump inside the GSHP, and lead these all to relays like the Omron (illustrated Right), which simply open or close a circuit (can be DC or AC) when a 230vAC is applied, and this we will attach to the port of the datalogger to record the On and Offs. So the relays have been purchased and installed, and next time Blaise calls, we will wire them to the datalogger with speaker cable.

    I am very grateful to Chris for educating me on relays. I have realised that if I want to power the pump in the loft, I don't need to run a power cable up there. I could just run a thin pair cable (capable of insulating 230vAC but not required to carry any current) up there which alerts the relay, and then permits the pump to use the power sockets in the loft. As I will have two pumps in the loft, for Sunboxes Mark 1 and mark 2, they can be alerted by relay. Until the Savita is installed, I will stick with the existing conventional power cable running up to the loft.

    2012 Postscript: The Savita was never installed, as I didn't want to mess up my South wall any more, I re-used the components at East Leake, and I have decided to install a second system using high temperature collectors instead - evacuated tubes.

    Thursday, April 22, 2010

    April Sunshine and hot baths....

    22 April : We've had a succession of good days, sunwise, and my whole family is here... son and daughter. We have had 5 days out of 7 above 20 kWhrs of Photovoltaic generation, and have burst through the prediction for April - for this month we should expect 306, but we beat that today... with nine days of April to go.

    I am quite glad my daughter is doing 'normal' things like having a bath (because we only ever have quick showers....) as this is a good test of the GSHP's ability to bring the water tank back to 51º, using some of the buried heat to achieve a good COP.
      This evening it was Very Quick to reheat the water by the way. Although I have made the Sunbox activating temperature difference to be 5degC, they are still working at 10.30 pm feeding heat to the ground and GSHP!
      The air temp outside is 8.5º but it is 10.5º inside the sunboxes despite the glycol continuously pulling heat out of the boxes at 5.0º. I feel that the brickwork must be continuing to release heat, otherwise, how could the air temp be holding up well late at night? I would like to paint the brickwork inside the sunboxes with matt black paint, but am reluctant to do this as there are already some holes drilled, is that enough? The black paint would make them even more effective.

    Datalogger starts work

    22 April : Blaise called round in the evening with a USB cable for the datalogger to the PC, so we got it working. There were a few white and green strands to swap, and one of the thermocouples didn't work but we had a spare.

    So now, 8 different channels are being recorded every 5 minutes. We have more cables to add, but they have been programmed into the PC already.

    Some time in the near future, I am going to have to have a week with the Sunboxes turned off, just to compare with their present performance with them not operating. As it is nearly summer, I don't mind having them off a while.
       The heatpump looks a bit wierd festooned with fine green and white wires, but they are all doing an important job!

    ICAX : pioneering Interseasonal Heat Transfer

    22 April : In my early research for this, I came across the website of ICAX, a British company who seem to be the pioneers of  Interseasonal Heat Transfer, in fact I think they have trademarked the name IHT[tm]. They have a wonderfully informative website, demonstrating some of the projects they have done already, but also providing a wealth of theoretical and explanatory background. They do not include Sunboxes yet, but are clearly looking for every way to harness sunshine and store for heating, even as a way to keep roads ice free. After the evening with Alan Simpson last week, I resolved to get in touch with ICAX, and discuss a new way to 'Recycle Sunshine' as they put it on their site.
        I had a phone conversation with Edward Thomson, one of the ICAX team who has written much of the website. I will be monitoring the performance of our sunboxes over the long summer, and into the winter. If a Sunbox system is ever to be commercially available, it needs to be value engineered as being proven to do the job at a cost and with a buildability that is proportional to the return. So the monitoring will continue, as will tweaks to the system that bring about improvements, such as fitting the three-way solenoid valve. I hope to meet with some of the ICAX team at a future opportunity - meanwhile, I advise my blog-readers to look at the ICAX website.

    The Swarm concept - urban opportunity for Sunboxes?

    The Swarm concept
       On Monday, Alan Simpson MP told us the story of Hamburg, where there is a debate about building new power stations. One strongly discussed idea is that of the 'CHP Swarm', remotely controlled by the Grid management system. Thousands of CHPs could be installed in domestic and commercial premises, giving a good geographical distribution. When demand is low, the machines hibernate (because other sources like wind and solar may be providing enough), (although individual house owners can run them when they need to for heating); when demand picks up, the machines are booted up (e.g. windless winter days); when demand is high (winter evenings, and events when demand is predictable such as intervals  of Televised football matches), the machines spin up to higher output. If one urban area has higher demand (eg office district in daytime and residential in evenings), the machines in that area spin up to meet the demand. Transmission losses are low because the consumer and generator are in the same district. The householder needs do nothing apart from accommodate the machine, and maintain their broadband connection - they are paid through the feed in tariff for the energy output, so it is in their interest to maintain them reliably.
      We have all seen natural history videos of vast flocks of Locusts, Starlings, Midges, Herring etc appearing to have like a single intelligence, moving rythmically or purposefully.

      The idea of thousands of sophisticated machines is not so strange as we already use the 'swarm technique' already for short term transportation, in routes which are short or cannot be served by public transport. Every morning, thousands of children pile into cars to be taken to school then the cars return to be parked outside the house. Thousands of cars drive into city centres and shopping malls every day. Despite the cost of making a car, most families seems to find one way (finance, second hand, third hand, lease) of having one. Cars all cost more than CHP units, but many families have two.
      The 'swarm' idea applies in culture and the media. 20 years ago, there was only BBC1 and BBC2 and ITV. There were a limited number of national or local newspapers, end of story. Highly channelled and centralised. Although we now have more channels than we could have imagined, the swarm technique now applies in the Blogosphere, where thousands of people can join a Facebook or Myspace group within hours, and contribute comments, and provoke discussion, create crazes. Youtube allows individuals to make their point or post their music. Some people spend 6-10 hours a day on line and never watch live TV, they watch iPlayer.
      It has been a recent fashion to have 'render-farms' so that many machines on a network share the task of computing difficult problems or rendering tasks. I have been in the University of Nottingham's 'inner computing centre' and there is no enormous computer. There are racks and racks of interlinked servers, each the size of an iMac laid flat in a rack.

    Urban opportunities
    I am leading to the idea that urban areas could have a large number of sunboxes conveniently posted on walls or roofs, often integrating well with buildings, which were conducting solar heat directly underground.
       In dense urban areas, the ground is shaded by the trees and well insulated buildings, the tarmac loses as much as it gains and is largely covered by parked cars, and shaded by trees in summer. The visible areas of tarmac are not enough to store solar heat 'accidentally' - so something more deliberate needs to be done. Sunboxes are cheap as a technology, and can be unobtrusive (looking rather like a window), can fit between windows, as part of a facade, in the valley between roofs, or even as part of a balcony surround.

    1.  The overhead photo (thanks to Googlemaps) shows an area of West London, typical of city residential density. This photo makes my point about the trees and the parked cars. But there are plenty of roof spaces where sunboxes would not even be visible to ground level. The problem here would be laying in ground pipes. But I remember when Cable TV was being laid in Nottingham 20yrs ago, every street was dug up for cabling!   There is a new generation of small diggers, small enough to fit through a house door (for excavating ground floor slabs), so it is possible to plant slinky Ground loops in domestic back gardens.

    2. The middle photo show the square mile of London, with key buildings many of which now use CHP on a vast scale, some have boreholes for cooling and for heating, they all have plant rooms, and they all have a high value but high running costs, making it a worthwhile investment to instal energy saving systems. Sunboxes work better on wall than on roof, and tall buildings have plenty of wall surface. Sunboxes can be part of a double facade construction. Just as the Heron Tower (just north of the picture) has a whole south wall of Photovoltaic, but also has a high level of transparency, Sunboxes are just a double skin with thermal collectors which do not need to occupy the whole space - so you can see round them, and they can include PV in patches.

    3. The Barbican development is one of the most successful London districts, being of mixed use (residential, cultural), and of mixed height - built in late 60s early 70s. Developments on a large scale like this can justify investment in district heating, boreholes, energy centre (for CHP), and for large scale heatpumps delivering to many residences. A new development can incorporate sunboxes so easily that the the viewer would just see them as part of the facade, if they realised what they were at all.

    The swarm concept is first about numbers, but it is also about the mass action or mass intelligence effect, compared with larger, single purpose solutions (as in thousands of network connected CHPs being better than a power station). So although my sunboxes are currently controlled solely by thermostat, I shall apply some thought to the idea of broadband connection (in the same way that my PV roof is now on broadband) and what they could do. If ultra-deep boreholes are shared by several houses, you would need some way to control and monitor the sunboxes serving them, the individual ones could respond more quickly to clouds moving away from the sun compared with a central weather station miles away. As clouds moved, sunboxes would come on and switch off accordingly.  Districts with newer, better insulated houses would have different amounts of draw from the borehole.

    Is it so unreal that heatpumps could be in the majority of households in the long term future? Well you only have to look at the food retail industry to see how supermarkets and frozen food have made it essential to preserve food in refrigerators. There not been a private market or council house built in the last 50 yrs that included cold cellars or traditional larders.  Fridges are so commonplace that there are now 'fridge mountains' of thrown-away fridges when people upgrade to better models.  If very expensive refrigeration technology can be built in sufficient numbers, it becomes very cheap - and fridges are the most reliable appliances in the home. Heatpumps are simply large scale fridges, with pipes attached - they could become a lot cheaper!

    CHP (Combined Heat Power)

    22 April : I did not  include CHP (Combined Heat Power) in an earlier discussion of Carbon Zero solutions because it burns fuel, and heat is the by-product of generating electrical power. Sometimes you get more heat than you really need for a very well insulated building. And if you want heat, then the Sun is a cleaner source of heat, and PV a cleaner source of electric - both require a storage medium - earth or water for the solar heat, and the Grid for PV.
       Most CHP discussion is about applying it in office buildings, libraries, schools etc, and for large buildings they make sense. CHP devices have been miniaturised in size for working in houses, although the thought of having an 'engine' working in my house (the byproduct of which is heat), in a box the size of a large fridge immediately makes me think of which corner of the garage you would put it in.We couldn't possibly need all the heat it would produce, especially in the summer, and I couldn't bear to look out of the windows of the house seeing combustion smoke surging from a flue over the garage. If you need electrical power in the summer, what do you do with all that waste heat?
       In Urban areas where densities are high, and all cannot use PV or heatpumps etc, they have a use. Although the electricity produced is not large, there are no transmission losses in the immediate area, so there can be a benefit. They can be remotely controlled if connected to the broadband - switch on, and vary speed, on demand. And surplus heat can somehow be used to augment chillers, although this is a mystery only understood by refrigeration engineers.

    Three port Solenoid Valve ordered!

    22 April : The Three-way valve has been ordered! A Danfoss 28mm three-port. In an earlier article, I pointed out that the split between the glycol going to the sunboxes and down to the ground was unknown, and therefore confusing the evaluation of this system. I found today from David Atkins that you can get 28mm versions, you just have to go to a specialist supplier - and extra cost of 28mm over 22mm is negligible - so order and be happy!
      He points out that earlier I was complaining about how I could have done this whole system with 22mm or even 15mm piping, since the sunboxes were tee'd on with their own pump. If the sole purpose was for summer time pumping to the ground, this would be sufficient as one is simply capturing free energy when it's available.

      Things have changed! I have since observed that the Realtime heat augmentation is a real benefit (visible during the day).
         I want to reorganise the plumbing and electrics so that the Entire Glycol circuit goes to the Sunbox when the thermostat commands, to maximise the Realtime and Diurnial benefit. The Interseasonal will be unaffected by this change, so it will be an improvement. If I had built the system with small tubing, this would be a non starter. But my huge investment in the larger diameter pipes will now pay off as I can push the entire ground loop through it without disadvantage. This means that the GSHP and the ground will rapidly exhaust ALL the heat that the sunboxes have to offer, then turn the sunboxes off, then continue with the ground until the sunboxes warm up again - and the cycle starts again. When this is happening, the little 40w pump in the loft will be reinforced with a powerful 200w pump inside the GSHP, thus downloading the sunbox heat faster!
      When the Danfoss arrives, one has to check it carefully (by blowing through it) to make sure that when the Sunbox electrics are turned off and the valve relaxes into a set position, the GSHP resumes business as usual, through the ground loop.
      As air temperature is now very important, I shall make sure that the Sunbox Mark2 is a lot more airtight when closed up. I had imagined that the boxes could run at night with the ventilation louvres open, but really, they get so much heat during the day, a bit more low quality heat at night is not worth the pump consumption.

    Wednesday, April 21, 2010

    Glossary explains many things

    20 April : For those who arrive at this blog somewhere in the middle of the process (it's always in the middle...) I have written a Glossary. It is stored in a location in Aug 2009, but is regularly updated. Please ask if there is a term you want explaining better or expanding on.

    Tuesday, April 20, 2010

    Datalogger upgrade

    20 April : Blaise came round in early evening with a replacement Datalogger, the Datataker DT500. He has 8 cables, so most of the connections were made to the significant pipes.
      Unfortunately, we couldn't actually set it running, as we will need a serial cable from the DT500 to a PC, and the one we had has the wrong sockets. So another day will go by.
    The software sets up the DT500 so it knows what is coming in through the channels, whether analogue, digital etc, and whether temperature, humidity, time, counters or whatever. The thermocouple ends are wrapped in ptfe tape and firmly taped to key pipes.
    19 April: I also purchased the Polycarbonate sheeting for the sunbox and for the PV panel front, and have purchased a timeclock that can be set into a pattress box to display accumulated time. So this Sunbox mark 2 project is under way!
    PV roaring ahead again
    Although the air temperature was cold, the sunshine was intense, and we had our best day ever, 22 kWhrs of power generated!

    Evening with Alan Simpson

    19 April : I and about 30 others shared an enjoyable evening with the outgoing MP for Nottingham South, Alan Simpson. He has built a truly green home in the Lace Market area of Nottingham. One good reason for leaving is that he feels that he can do more campaigning for renewable energy solutions (to combat Climate Change) out of Parliament than in it.
    In recent years he has gone from being Blair's toughest rebel to being a significant advisor to Ed Miliband on Feed in Tariffs. This was the result of a cross party coalition of concerned MPs that he organised to promote FITs as an energy initiative that is proven to have worked in Germany.
      We had a good 45 mins of address from Alan, followed by an hour of audience questions. Although he isn't standing, most of the audience were constituents, who are still interested to hear his views, and regret losing him as MP.
      As one of Alan's new initiatives will be renewable heat (along with renewable energy generation), I hope he will find a genuine interest in the application of Sunboxes in buildings and housing estates where GSHPs are used.
     This may be some way off, as even in the under-construction eco-housing scheme in Nottingham's Meadows, they are not using GSHP (but they will use wind turbines and a lot of Photovoltaic on the roofs).

    Monday, April 19, 2010

    Does the meter run in reverse? No!

    19 April : I wondered a couple of days ago if my meter would 'go in reverse' if you have a good day of photovoltaic generation. For the weekend on a good day, I took readings every couple of hours. Mine doesn't, it remains static during the day and only moves forward only if we do some ironing or use the kettle a lot, or the heating has to be on. After sunset, it rolls along as a normal one would. Chris Brook of EvoEnergy has provided me with an answer:

    "Whether your meter works in reverse depends on the type of meter installed. Old style mechanical meters will run in reverse and people with these will get an extra, though unintended, financial benefit. If you have a more modern electronic meter this will accurately record the units of electricity you import from the grid. It will be stationary if the amount of energy you are producing exceeds your current demand. Your [OfGem] generation meter will tell you accurately how much you have produced. In terms of what you export, this will only be measured accurately if your electricity supplier installs an import/export meter. The only energy provider currently doing this is Scottish and Southern Electricity. Other major providers intend to estimate how much you have exported based on the amount generated. As far as we know most are going with a generous 50/50 estimate.

    Energy you produce will flow to its nearest point of use. If there is demand within your home this will be nearest. If you produce more than you currently demand the excess will flow to its nearest point of use via your mains electricity cable. In all likelihood there will be demand from one of your neighbours and this is where the electricity will be used. The electricity flows via the grid to your neighbours."

    Obsolete meters with the revolving disk used to go backwards, but not the modern digital meter - and for a PV producer, we have to have a modern meter.

    Blaise version of Circuit diagram

    18 April 2010: Blaise has done his own version of the circuit diagram, of plumbing and electrics. This is incorporating most of the datalogging wires, and shows more of the engineering of the heatpump and of the heating circuits. The ground is drawn more like a 'battery'.
      I can see a few things to change or add on there, and I will probably uprate my own version, with the datalogger network as another layer.

    2011 Update: - the Plumbing Circuit was modified in May 2010 and is different from this. The only correct diagram is the one I issued after May 2010.

    Sunday, April 18, 2010

    Now it is Summertime, slow the pump

    18 April :  As for the existing system, I have decided to call the present time, officially, Summertime so the pump speed can be returned to slow. We can return to the middle speed in October.

    This is for two reasons,
    1. The heatpump does its business very quickly, but with warmer external temperatures, the sunboxes may run for 10-12 hours or more. For about an hour a day of GSHP working, we just don't need so much pumping. The soil is warm, and the sunboxes deliver Realtime heat, so the GSHP gets the heat it needs very quickly.

    2. Although the daytime energy used by the pump is free (it comes from the PV roof), there is no need for such high pump speed during the summer, as I still suspect that for a small house Interseasonal Thermal Storage is a dream that may turn out to be a mirage - although for buildings with large footprint like a School or Office, there is more potential.

    Interseasonal Thermal Storage - will it work?

    18 April : Let's discuss Interseasonal Thermal Storage a bit more.
    This was my original intention with this research project - I have observed on good days that the soil temperature around the pipes does indeed rise nicely, but by midnight, the heat has distributed outwards well, and the soil is at a stable temperature - not as cold as it would have been without the solar charging. Blaise will want me to turn off the sunboxes for a week, some time, to see if it makes a difference. As the timescale of this is seasonal, I can't really see the point of just three days. We have had three years without sunboxes, and should have measured then!

       What I can be sure of are the Realtime and the Diurnial effects, and we are seeing that every day during this equinoctial time. Later this year, in the Summer, any energy used by the circulating pump is freely supplied by the PV roof, so we shall store the thermal energy, even though we don't yet know how much will stay Interseasonally until Winter.

       I can be certain that with this system there will be an absence of the usual longterm Soil Chilling - it is already clear that the sunboxes are preventing chilling, every day.

    We have got through the 2009-2010 winter now, and normally the soil in April would be chilled from a long winter of having heat pulled out for the house. After a month of operating the sunboxes, the soil is already at a temperature that you would normally expect to find at the end of a long summer (of not drawing heat from it, and for it pulling in heat from the vast surroundings).
        For research reasons, we will run the pump for the entire summer, of course, and we will continue to make measurements. The long moment of truth will be during the winter months of December-January-February-March, to see if the workload of the GSHP is made easier by warmer soil. Can some of the build up of summer heat be evident in the dark month of December?

    13 Dec '10 Postscript: Yes it can!!
    Ground temperature is 10.4°C at this date, whereas it was 7.2°C a year ago. This is a partially thanks to the summer charging, but I suspect is equally due to regular recharging by a good number of sunny days since the summer which keep the temperature from falling too much.
    16 Jan '11 Postscript: Yes it still can!! 
    Ground temperature is 10.6°C at this date, whereas it was 5.2°C a year ago. With the mild weather of early January'11, the deep ground temperature has been rising very slightly.
    8 March '11 Postscript: Yes it seems to be proven! 
    We got through the low point of winter with the ground temperature never falling below 10º, and it is now rising firmly, nudging 11º. Yesterday, the GSHP only used 13.63 kWh despite the air temp never rising above 10º and the night before having been below freezing.

    Painting Panels for Savita Sunbox

    18 April : I got some Blackboard Paint from Screwfix, and have painted the back of the Sharp PV panel, so that it can radiate inwards towards the steel radiator. The sun was out, and as soon as the paint was dry, it had a surface temperature of about 60ºC when the sun was shining (even though air temperature is still cool). This bodes well. 
      The steel radiator was also painted, and those pesky fins are a real pain to paint. The front surface of the radiator has to pick up heat from the back of the PV panel. The fins at the back are important, as they are mainly to pick up air temperature, but their black surface will also project surplus heat into the brickwork which will act as a short term storage medium.
       The polycarbonate was ordered on line from LIV Supplies, and so there's no going back! I have enough aluminium and polycarbonate to make a 'faux-PV Panel' that is dimensionally identical to the real one, and can be interchanged - so I can test it out with a clear over panel allowing the radiator to see the sun directly. And I can try with a piece of black painted polycarbonate to see if that will project heat into the sunbox.
      The sunbox mark 2 will be called Savita, which is the female equivalent to Surya - but like a woman, vastly more mysterious and complex than the male version.

    Radiator for the Sunbox mark 2

    18 April : Seems that more and more people are thinking about PVT:- PV and Thermal combined - although they are intending it for hot water heating mostly, and what makes my project unique is that it's for a Sunbox, which augments a Heatpump.
      Blaise is doing a paper on it for Shanghai, and I am developing one, and Mike S wants to develop one too.
      As a commitment to the project, I have ordered the aluminium for my prototype, and have compiled the shopping list for the Polycarbonate.
      For the Thermal Collector, I did have a free gift of a central heating radiator, but it was 25 yrs old and would be too inefficient and probably full of rust and scale. I decided "not to spoil the ship for a ha'porth of tar" so gave that radiator away on Realcycle, and went to Screwfix for a brand new, high surface area single panel radiator, and a pot of Matt Black paint and some brushes. This will be for the radiator and for the back of the Sharp PV panel.
      Ice Energy will supply another Wilo pump and a Supercal Energy flow meter. Although this unit will be tee'd into the existing loop to the existing Surya Sunboxes, it will have its own pump and energy flowmeter, so we can calculate its contribution separately and subtract the difference. These will be switched on by the same thermostat that we presently use. Also, it will be based on 15mm or 22mm plumbing so will need a pump to avoid it being a 'backwater'.

    Measuring up for Datalogging

    17 April : Blaise came round to discuss where we would fit thermocouples for the datalogger. He is the engineer who is also a PhD student in our school studying heatpumps, and will be at Shanghai to present my sunboxes (and a couple of other things too, including PVT).
      Seeing it in action on the sunniest day of the year, he really did seem to appreciate how they worked and the thermostat was working wonderfully to display the temperatures. As a heatpump engineer, he has  focused on the mechanics and the COP, whereas I have this larger idea about how the product might be extended as an
      He suggested moving the Cold sensor to the pipe that comes from the loft, and I did that.... It's useful to have an accurate display of that pipe coming down from the sunboxes - but I changed it back after he had gone because I remembered that the sensor has a double function - it needs to be in the COLDest location, or it will not switch on the sunboxes. The only temperature that should trigger it is the Ground loop temperature.
      I realised this when I found that the sunbox pump was still working at sunset, but by now pushing glycol through the loop colder than the loop had been earlier. By moving it to the position I had originally put it in, the Sunbox can Never cool the loop.

    Time for a Better Datalogger
    The datalogger I had originally been loaned is a DT50 and only really records 4 channels. We identified FIFTEEN important temperatures that must be recorded:

    • 2 - The flow and return to the Sunboxes
    • 2 - The flow and return from GSHP to the Groundloop
    • 2 - The flow and return to the underfloor heating
    • 2 - The cold water main and the hotwater supply pipe
    • 1 - The combined temperature of outgoing pipe and incoming sunbox pipe where the Trigger-Sensor is located.
    • 3 - the Air temperatures in the House, externally in the shade, and inside the Sunbox.
     3- We also need Lines in from the Energy Flowmeter on the Sunbox circuit, the Hot water flowmeter and the future Energy Flowmeter to the PVT sunbox that is not yet built.

    2 - We also need a line in from the thermostat and the heatpump simply to record WHEN the devices go on and off. As they seem to track each other, this is valuable information.

    So we need a better datalogger, and Blaise will bring a more powerful one next week - probably a DT500. We will put it on the roof of the GSHP, and ask Chris to weld us up 12 thermocouple cables.
    My laptop had a problem with loading the software - I have an old virus checker on it that has become worse than a virus - it can't be upgraded, but it won't allow me to install another, or de instal it.
       So he will try to get an old laptop from the Uni. Actually... I just remembered, I have one in the office at the Uni. So I will bring that back.

    PV roof like Usain Bolt! 1000kWhr

    17 April : The Photovoltaic roof took a long time to crawl to 500 kWhr because it was Winter, but now we are in April, it has charged to 1000 kWhr, and crashed through that target like an olympic sprinter, with a monster sun-day of almost 21 kWhrs in one day!

    Meter stuck?
      This was also a test of our house meter, and I am very annoyed about something that I hoped would work for us... but it seems I am going to have to make some phone calls next week.
       I had fondly imagined that somehow our house electric meter would work in reverse on good days, so that we get credited for power we generate through the saving on reversing the meter. The OfGem meter correctly shows what is being generated, and we hope and presume that it goes out to the grid - but through what cable I don't know. The actual house meter just locks when stuff is going out, so for example, while 20kwhr was generated by our roof, the house meter just stuck at 26632 at 3pm. It didn't move back, but while the sun shone, did not move forward either until after sunset.
      I spoke to my friend Karina Wells later in the day and she says that when her roof is doing well, her net consumption for the day is down to 1 kWhr. That is impossible for us, because even if the house uses none in the day there is still the baseload of the house, and evening heating/ lighting/ power - so it can't be less than 7-8 kWhr in a day. We used 7 kWhrs in evening cooking, lighting, power, so the day ended at 26639.

    18 April : Another sunny day and another chance to test the meter. The reading was 26639 last night at about 2am (yes, I am nerdy enough for the test to have checked it at that time). The reading at 2pm today, 12 hours later, having generated 17 kWhrs from our roof is still 26639. It seem that at this time of year, the only time the meter moves forward is at evening/night time.

    19 April: PS, I have had a reply from our installer, and the new generation of meters are designed only to show the IMPORT from the grid, so will remain static when we are generating. The balance between what we use ourselves and export is based on a rule of thumb of 50%-50% over a year (at the moment, we are exporting more than we use, of course). I will probably publish this answer in full in a later posting.

    Friday, April 16, 2010

    Mike Siebert calls

    16 April : In my acknowledgements, I have mentioned Mike Siebert as 'sparking off the idea'. He called round this evening for a look at the system, and to extend discussion of future projects.
       It was a discussion a year ago when he mooted the idea of having pipes from a solar panel feeding into the same mass under a house as the ground loop from a GSHP.
       This is difficult to model theoretically - how big would you make a concrete slab or rock store? 300 thick? 500 thick? the size of a swimming pool? (I am sure Dr Chris Wood knows how....) would you insulate under it, or only at the sides? (letting heat escape downwards but not sideways).
       But then one thinks there would be a stasis or evaporation problem with water, and that a large block of phase change wax might do it better because it stays at one temperature.... and concrete is a CO2 producing material. In our case, if the soil is well compacted with no cavities or moving groundwater, maybe the earth is a good battery, and merely needs recharging more quickly than normal solar heat can get down there.
       After making some enquiries in the Dept and getting nowhere, it seemed to me easier to model it in full size and realtime, on my house, and as I was unsatisfied with the performance of the GSHP, I wanted to find a way to make it work better.

      Mike is presently thinking of designing a range of houses, but he is frustrated that you can't get triangular PV panels, as so many houses including the ones he wants to do have hipped roofs. He is also wondering if the sunbox idea could be applied to black roof-tiles on a roof-plane. [Actually Sharp do make triangular panels, but they are not exported to the UK and not approved for certified installations in UK]. He and I and others are also preoccupied with the idea of combining Photovoltaic and Thermal - and I am building one right now!

    April Circuit diagram

    16 April 2010: I have updated the circuit diagram to record how it is in mid April. However... there are some changes, possibly I will add in a 3 way Danfoss just above the GSHP, and I may add the extra Sunbox Mark 2 with its additional Pump, PV panel and Energy meter.... so expect another in May!
    I havent removed the earlier circuit diagrams for the purposes of archiving the historical development process.
    October 2011 Postscript: This circuit was changed in mid May 2011, although the circuit above would work fine for use with a conventional flat plate or evacuated tube panel. The general configuration now would be on this page:

    Time for more plumbing?

    16 April : At the moment, the flow from the GSHP divides more or less equally into:

    • roughly half up to the Sunboxes, 
    • and roughly half down directly into the ground loop. 

    I discussed this a few days earlier - with the GSHP now working correctly (so has become a 'constant'), this particular question of flow division becomes more significant because it is a 'variable' that affects the results - and worse, it is an unknown variable. The actual fraction depends on the pump speed of the Wilo in the loft, since the pump speed in the GSHP is a constant setting. So, collected data is confused by this big unknown.

    What I could or should do is fit another Danfoss solenoid valve that would CLOSE the direct link to the ground loop when the boxes are working, and send ALL the glycol through the sunboxes and then to the ground loop. As soon as enough heat has been downloaded, the thermostat would tell the Danfoss solenoid valve to open again, close the Danfoss in the loft, sending ALL from the GSHP to the Groundloop.

    There is a risk in this if one or both of the Danfosses doesnt work and the GSHP is trying to push against Two closed valves. If the thermostat is turned off due to a fuse blowing or a wiring disconnection, the Danfosses have a feature in them to revert to a closed position. So there might need to be a 15mm open bypass pipe in case of that occuring. In case of a persistent problem, eg Thermostat failure, the Danfosses can be manually locked in the open position.
       Also, I have realised that you can get a Three-Way Danfoss, so that if one closes, the other route opens. This avoids the risk of a blockage, and could be set to connect either to the other part of the loop or to a bypass, with the default (no power) option to be sending through the ground loop only.
        Time for some Drawing first, then consult with Ice Energy, then a bit more Plumbing perhaps. At the same time, an Energy Flowmeter could be included. These are both 22mm units, so we definitely need the OK from Ice Energy.

    Excellent results with a working GSHP!

    16 April : I am getting some interesting results now that the GSHP is working correctly. It comes on, does its job efficiently, and now spends long periods in sleep because the house is well enough insulated not to need more heat for a while. So I can take accurate readings of the sunbox performance. I can also rely on the reading from the down loop pipe as I made my special copper connector, and took care to calibrate the sensor precisely last night.

    For example today... with the GSHP slumbering, the sunboxes are the only heating device... this morning after the GSHP had been off since the night before, the deep ground was 12.0. After a morning heating, the ground had been cooled around the pipes to around 8 degrees (during this warming cycle, the sunboxes contributed about 1/3 of the heat). During the lunch hour, the house was warm, the GSHP sleeping and the sunboxes were only recharging the earth.

    Time Sunbox  Looptemp   From Sunbox to loop
    1245 23.0     9.8> 9.8  12.2
    1300 36.0    10.9>10.9  14.1
    1315 27.8    11.3>11.3  14.3
    1330 24.6    12.1>12.1  14.1
    Heating restarted 1340
    1345 26.6     8.5>11.8   9.7
    [in this table, 
    ['Loop temp' is glycol coming up into GSHP and going out again]
    ['From Sunbox' temp is 50-50 mixture of glycol from the GSHP and from Sunbox]
    ['Sunbox' temp is air temp in the sunbox, just above the black plastic slabs. The weather is alternating sun and cloud]
    [when the GSHP is sleeping the In and Out temperatures level out because GSHP is allowing glycol to pass directly through, and at steady state this is indicating the deep earth temperature immediately around the deep pipes.]

    This clearly shows some immediate 'realtime' benefit. The ground temperature is rapidly recovering from the morning's heating cycle. In merely 45 mins, the deep-earth temp around the pipes increased from 9.8º to 12.1º. The liquid going down was consistently warm, and coming up cooler, having given its heat to the deepground, and is sent up to retrieve more. The moment that heating resumed, the sunboxes contributed directly to that, as can be seen from the significantly reduced temperature from Sunbox, still giving about 1.2 degs benefit.

    As an observation, when a heating cycle is running, the algorithm in the GSHP is usually requiring about 3/0 - 3.6 degsC difference between out and in. On a nice day like today, the Sunbox/GHP combined return temperature is consistently contributing about 1/3 of that,  e.g. 1.2 degs in the example above.

    Here is a similar sampling from later in the same day, again during a period of GSHP sleep, external air temp in the shade is 14.6º. The loop temp shows the returning temperature of glycol from deep in the ground loop. The house internal air temp is stabilised by good solar gain through the west facing house windows, so the GSHP is remaining dormant.

    Time Sunbox  Looptemp   From Sunbox to loop
    1515 35.7    13.3>13.3  16.0
    1530 34.7    13.5>13.5  16.5
    1545 32.4    13.6>13.6  16.4
    1600 29.8    13.7>13.7  16.3
    1630 33.7    13.7>13.7  15.9

    1700 32.7    13.7>13.7  15.5
    1800 24.5    13.6>13.6  14.1

    Heating restarted 1845
    1900 15.6     8.9>11.1   9.2

    As I take these samples, it gives me a clearer idea of where we need to put sensors for datalogging. These are so far the most valuable real-time readings we could have to prove the concept, and of course the regular meter readings (daily, weekly, monthly) are also vital for longterm analysis.

    The last 5 readings of that group are especially interesting. What it suggests is that the ground recovers heat to a certain extent, but when the delta-T between the borehole pipe and the surrounding soil is high enough, e.g. at a glycol temperature of 13.7º, the rate at which heat moves out through the soil away from the pipes begins to equal the rate at which it is being put down there - the soil does not just get hotter, but the temperature distribution gets smoother.

    We don't expect the soil to get hotter, what we hope for is for the body of warm soil to be larger, with warmth reaching out further, but not so far that it will not come back. So, two solid cylinders of soil 5 metres radius all at 13.7º without any cold 'rings' by the end of the summer would be a good result, and anything more than this would be an excellent result.

    Energy Flowmeter on the electric pump

    16 April : I am somewhat concerned at running the sunbox pump at mid speed, although this produces more efficient results for the sunboxes when they are interacting with the GSHP during heating cycles. In Winter and Equinox, this fast response is proving to be very welcome.
      For the long summer months when the GSHP is doing nothing much (a v small amount of water heating) it will only be charging the earth - for which speed is not significant. As much of this heat will diffuse into the infinite surroundings, there is no call to run the pump quickly.
     We might choose a date for official 'Summertime' when the pump is changed to slow speed - this can be when average air temperatures are consistently higher than 15º and the GSHP is working in summer mode.

    I have fitted a Brennenstuhl energy flow meter to the pump, so I can add to my metering spreadsheet its daily energy consumption and the cumulative total.

    PS, the damn Brennenstuhl doesnt work, it show zero for everything except the time. Doh!

    Thursday, April 15, 2010

    Reducing system losses

    15 April 2010: I also did a lot of pipe insulating, both in the house, and in and around the GSHP. If it is now working correctly in the electronics - response to sensors etc - it pays now to find other ways to make it more efficient. I have some rolls of super-thin insulation blanket that deserves to be used.

        In Sweden where the IVTs come from, winter temperatures are much lower, and many GSHPs are stored in basements, garage or or outhouses, so they are designed to protect themselves from frost by having permissible heat losses in the cabinet - there are uninsulated hot pipes in the cabinet, and the main water tank has a completely exposed copper bottom!
       As ours is not moving to an outhouse or garage in a hurry, and lives in a utility room with underfloor heating, it is not in danger of frosting up. I used some insulation inside the cabinet for the water tank bottom and some of the hotter pipes inside the cabinet, before closing up the side and front panels.
       The pipes that send and receive to the underfloor heating are usually in the range of 25-33ºC, I thought it was worth insulating them too, to reduce even the very small system losses from these pipes moving through the air in the house, which averages 10 degs lower.

    August 2010 comment: The insulation inside the heat pump - around the tank and pipes - has worked very well. You can leave the machine all day and if nobody runs the hot water, the temperature remains very very stable!

    Sunboxes on Volcanic Ash day - Cold Sensor question

    15 April : The Surya Sunboxes didn't come on much because it was a cloudy day with a cold north wind, blowing the Icelandic volcanic ash over the UK. It was densely clouded and one of our poorest days for Photovoltaic since March - and we had cold air temperatures all day, never getting above 12ºC, and more often below 10.
        I noticed that whilst the boxes remained off most of the day, they still came on correctly when the GSHP was putting out cold glycol, and we still pulled in 4 kWhours during the daytime heating period - all contributing to house heating.
        I reduced the trigger temperature difference back to 3.0 deg C to make it easier to come on, but am leaving the pump on at midspeed, because it seems to act more decisively - it downloads heat from the sunboxes and turns off quickly if the GHSP is satisfied.

    Sensor fixed!
      A new problem became visible - the Cold sensor that triggers the Sunboxes is an oval rubber coated thermistor at the end of a black bellwire, and being blobby, is a bit slow to respond. (The sunbox sensor hangs in mid air, visible to the Sun, so has no such problem).
       David suggested connecting the cold sensor next to some copper pipe, not to the underground plastic pipe. As the oval blob makes only tangential touching contact with any pipe, the response is really very poor on any pipe - it is slow, and perhaps not accurate, even if surrounded by insulation.
      So, I got a small section of 28mm copper pipe, cut it to a 120º sweep segment, and flattened slightly so it perfectly makes touching contact to 28mm copper pipe. The Oval blob was polished with a file to give it one flat surface, and super-glued to the copper segment, with some sticky tape to maintain very tight contact. The resulting component (pictured) was then attached to the Copper outgoing pipe from the GSHP, with a large smear of Vaseline to close out any small air-pockets between the surfaces. This sensor is now surrounded with plenty of high quality insulation to ensure that it is only reading the copper temperature.

    Heatpump : day of fixing! part 1

    15 April : As usual, the heat-pump started the day by going into its familiar overdrive and pushing the water temperature far too high. It really does mess up my big experiment having a machine that cannot respond correctly. The weather was cold, with a North wind, the same one bringing the ash from Iceland that closed down the airports of northern Europe. So if I didn't get it fixed, the machine would be on and off all weekend, perhaps more ON than I would like.
       I had a long series of phone calls with David at Ice Energy. David points out to me that most Heatpump owners can leave theirs on (like a fridge) for weeks or months on end - when we tried this, it consumed 65 kWhr in one day, or it spirals temperatures upwards and then shuts down. So we have managed ours not like a Fridge, rather more like an Oven. You only turn it on when you need it. This isn't right.
      Our series of discussions today seem to have fixed it, although my phone bill will be very heavy at the end of the month. Having read out all the parameters to him, it seemed strange that the transfer fluid temperatures in and out seemed wrong, compared with the ever rising water temperature. For some months, we have blamed the REGO controller. We decided to check all the sensors, perhaps it is them sending wrong information to the REGO controller (the light grey box, bottom right in the photo).

       For the last year and more, I have tried the "IT Crowd" method which is turn it off and turn it on again. This hasn't worked for longer than half a day. The machine is too heavy and plumbed in to try the other classic repair method - give it a good shaking, and a few kicks! :)

       So this time, I took the front and the side panels off and checked all the wiring inside - using a method which I used to find very effective for repairing computers in the 90s, pulling out all internal sockets and plugs, ribbon cables and sensors, and re-inserting them, in case there was a poor connection - checking bellwires from sensors, and power lines to pump and compressor etc. Sensors were checked to make sure they were connected.


    The moment all the plugs, sockets, cables etc had been pulled out and re-inserted, I restarted the GSHP. Straight off, it began to behave as it should do!
       The water temp was already so high that we didn't test that until some washing had been done in the house - but when it did work on the hot water, the GSHP boosted it to the correct temperature, plus the hysteresis margin, and then turned itself off precisely! Correctly!
       The heating came on less often, got to temperature more quickly, pulled in heat from the Sunboxes, and then moved to hibernation once the job was done.... Amazing!

     Story continues in the next posting

    Heatpump : day of fixing! part 2

    15 April 2010: There were still some other problems principally with pressure which is what made David and I chase the Air release valve to the hot water jacket surrounding the water tank - plenty of air came out!
    Then with his help, I checked the pressure in the underfloor heating circuit. There was also insufficient water pressure in the underfloor heating circuit (less than 0.5 bar), and mains water pressure can be used to boost it to 1.5 bar (see the little dial in the photo, middle right in the first posting). The low pressure permitted too many air-bubbles in the circuit which was why it was so noisy, and another reason not to leave it on at night.

    There were some drips of water into the 'tundish' from the heating circuit (discharging onto the driveway), so I gave the pressure valve a few seconds of water flushing to flush out any grit, and recharged the pressure to 1.5 bar. Normally, this would require a call-out, but David is confident enough in me to fiddle around inside.

    Sorry for all this outbreak of excess cheerfulness, but after a day and now an evening of this improved GSGP performance, it seems uncanny to have the machine working so much better and quietly. It is in hibernation much of the time (despite it being a cold day), and correctly coming on only when needed either for a quick boost to the water or heating.
    ..... useful day, although not much else done during the day .... but better use of time than all the thousands of people in UK airports sitting around being angry about their non-flights...

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