Thursday, April 28, 2011

Time around the circuit

27 April '11: Watching the summer time circulation, I can see the temperature going down, and the temperature of the returning liquid. So that should give another indication of how much heat is deposited in the ground. 

 I just calculated the volume of liquid in the loop from the Heat pump into the ground (not counting the loop that goes through the panels) It's a pity we can't do a sort of Pooh Sticks method to find out how long the glycol takes to get round.
Upper: When I had to fill the upper system it required 20 litres of neat glycol and 40 litres of water, that is 60 litres in total. (I had a 20 litre container for pouring, so know this precisely)
Lower: For the lower loop, we have near-enough 200 metres combined length and a 40mm pipe all the way round, whose internal diameter is 32mm, which has a cross sectional area of 0.0008 m2, which gives an internal pipe volume of 160 litres.
 Total: This makes 220 litres total for both parts of the loop.

As the slow pump speed is 300 litres/hour (5 litres a minute), it must take about 44 mins for one entire circulation to take place at the slower pump speed. (When the GHSP is running, it goes at 18 litres/minute, more than 3 times that speed).
The temp diff between going down and returning is about 2.5 - 3.5 degs C.

With specific heat of the liquid of 4.0 kJ/kgK, that suggests: 4 x 300 x 3.5 *1000 / 3600 

That is equivalent to 1.17 kilowatt - i.e. in one hour, just over 1 kilowatt hour of heat deposited. As the data from the energy meter confirms a figure close to that, then I am glad to find agreement. 1.17 kW is almost exactly the average capture we got throughout last Summer.
I have long noticed that during the Equinox and Winter when the GSHP is running and forcing down the loop temperature, the delta-T improves and the rate moves up to 1.5 or even 2.0.

Tuesday, April 26, 2011

A life passes...

26 April '11: my dear Tabby cat Becks, who took such an interest in the datalogging process (in case we dropped some food nearby) has passed away... and I have to bury him in the garden.
  He is about fifteen, and had difficulty breathing and eating, so we had to do the right thing for him.
  Long live the memory of Becks! He will live on in this blog, for certain!

Monday, April 25, 2011

24 April roundup of results

25 April '11 : In my regular Sunday round up, the house is yet again achieving an all time low annual consumption for the whole house of 5,423 kWh and the GSHP of 3,442 kWh.
   The ground temperature is up to 12.4ºC (whereby it was 9 point something a year ago). During the day, the deep ground temp is up to over 14ºC, but my system of measurement is to leave the ground to settle out in the evening, and measure it at midnight. The ground is consistently rising in temperature, and I don't expect it to get to a high temperature, but if that heat has moved out and settled in, then it represents good storage. If it gets to 14º then that is not high enough for it to get lost outwards.
   The Sunboxes are maintaining an annual figure of over 3,000 kWh despite that they do not pull in as much when the GSHP is asleep as it seems to be most of the time now. The flow rate without the GSHP is only about 5 litres/min, but running at a good trickle for sometimes 13 hours a day, this is a good harvest.
    The PV seems to be stable at an annual total of about 3,250 kWh but I suspect that the panels are dirty despite my recent attempt to hose them down. The long hot drought has baked a fine coating of atmospheric dust on the roof of the car despite it having a power wash and wax a short while ago, so I guess that the PV panels might have a similar problem. There is possibly a weather explanation as in the same weeks last year, the weather was very sunny, but also cold with the GSHP required to continue heating - so a good PV harvest! 
Wow!  On the 25th April, the PV roof broke through the 20 kWh barrier for a single day! Highest day of the year.
  Meanwhile I need some very heavy night rain followed by a sunny morning, to get more figures like that!
Doh! A bad note is that the Volume read out on the energy meter seems to have gone wrong, but I have a spare volume meter that I will have to read instead. If the energy reading in kWh goes wrong, I shall just have to shell out for a replacement meter without any delay!

Saturday, April 23, 2011

The walls are helping

23 April '11: By the way, with this summer weather, I am again seeing a special phenomenon, which is that hours after sunset, the Sunboxes are still about 4 degrees higher than the ambient air temperature, even though the daylight hours ended with rain and thunder after a hot day.
    Being at over 22º, the Sunboxes are still sending heat down into the borehole even though it is after 10pm at night. The brick wall has been absorbing sunshine all day and some of that must be conducting to the air space in the Sunboxes. The temperature inside the box has been over 40º for many hours of the day and behind the wall is 100mm of insulation, so the only way out for that heat is to be released to the air space, and a little bit outwards through the brickwork surrounding the boxes.
   This is the phenomenon that enraged the trolls on Navitron forum, who thought that the idea of getting heat from the wall was some 'malicious hoax'.  I got some very nasty criticism, with some casting 'nasturtiums' on me, my children, my wife and job, as if a bit of criticism based on Physics and Engineering wasn't enough.
   Sorry, but having watched the airspace temperature many times this week being 40º, 42º, sometimes 46º, for hours on end, day after day, it is no surprise to me that the brick wall returns this daytime heat. It is simple logic. And it is not taking heat from the house, as it is warmer than the house, and if anything, some of that heat may be migrating inwards to warm up the bedroom at night.

  For a quick calculation:
  • Area of Brickwork= 5.25 m2 behind the polycarbonate
  • Volume of Brickwork = 0.54 m3 assuming 102mm brick leaf.
  • Thermal capacity of brickwork = 0.48 kilowatt hours per ºK per cubic metre
  • Brickwork cools from 42º to 20º during afternoon, and for a couple of hours after sunset, by which time the ambient air temperature is around 14ºC. After the Sunbox goes below 20º, the pump is turned off to save on pump consumption.
  • Thermal storage = 5.7 kilowatt hours over that 22 deg range
  This cannot soak into the walls due to 100mm of insulation, so it has to return to the airspace. Some of it escapes through air leaks, and some is absorbed into the black panels if the glycol is circulating for a few hours after sunset.

It is for this reason, the summer night heating, that I would be reluctant to make Sunboxes that were a portable box with a plywood back, because one would lose this thermal capacity effect.
    Looking at this further, it seems that there is no need to try to make it into a Trombe, i.e paint the brickwork black to help it absorb more sunlight. There is little of it visible to the Sun, most of it is covered by large black chillers. The brickwork gets its heat by conduction from the very hot air in the box. My wife would complain terribly if I painted part of the wall black, even though she is unable to see it directly. If the appearance of the wall matters less than performance, then painting it black could be helpful.

Try Optically clear mirrors?

21 April '11: I have now discovered where to get genuine mirror quality polycarbonate - i.e. external quality, optically clear mirrors! In sheets of 1.25 x 2.5 m size! (but it is £ 250 for one of those sheets!)
    I have to monitor the existing alloy mirrors during the summer, and decide if they make a difference. If they do, and if I feel that making them clear would improve their performance, I might invest some of my earnings from the Feed in Tariff in some clear mirror!
   This is Research, and the specific cost does not have to be met by strict payback targets. If these were ever to be produced commercially, the alloy is 1/6 the cost!
   The 3mm polycarbonate would not be strong enough in itself to perform as my alloy sheets do now, but they could be cut to size and simply riveted to the existing aluminium sheets!
   I have some spare aluminium alloy sheet and have a glass mirror and will spend time in the garden measuring the radiation from the reflection (shining the Sun in my face!) before spending more!

March April Heatwave

Compare the PV and the Sunboxes
21 April '11:  All of this week during several hours of the day, the temperature in the Sunboxes have been above 40º , and with the GSHP having nothing to do, the glycol going down below has been safely above 20º and coming back up at over 13º for that same time....
  What's there not to like about that? (Listen up Navitrolls!)
  This graph is comparing the PV and the Sunboxes at weekly intervals, since Mid March'10 when the Sunboxes were turned on. Throughout Summer 2010, it's clear that the PV whacked the Sunboxes consistently. Since the Autumn Equinox, there was a big change. The aluminium mirrors were fitted to the Sunboxes, but also, the heating came back on. We had an unusually Cold Autumn-Winter, and during this period, the GSHP gets very active, thus boosting the activity of the Sunboxes by using them as a real-time heat source.
   Therefore I am still not clear whether the gigantic improvement in the Sunbox performance was due to the heating demand (and the equivalent reduction in earning of the PV), or due to the additional boost from the mirrors. The only we we will know for certain will be to reproduce this graph at the end of 2011, to compare the two summers and winters. Chris Wood is certain it is the heating effort, and agree 50%, but I also have a belief in my mirrors being the other 50%!
  This graph runs for 13 months, and we can already see the difference between last March-April'10 and this one. During this time, the GSHP has been almost totally dormant, so the Sunboxes are working on summer mode - storing heat, but not using it in realtime - and they are doing better than for much of last Summer.
  This heatwave also demonstrates one reason why the performance figures of the house and GSHP are breaking records every week - last Spring 2010 was unusually long-lasting in the cold wintry weather. The first day with an evening temperature above 10º was March 17th ! But at the same time in 2011, the GSHP is not heating at all, it is on Hot water duty only!

Thursday, April 21, 2011

Dynamic Simulation of Boreholes

21 April '11: I have been trying to work on a dynamic visual simulation of the performance of the GSHP and the Sunboxes. I don't know if there existing pieces of simulation software that can do this, that can transform a process into a 3D image or movie. I have some of the PhD students in the school interested, but none of them immediately latches on and says, Yes, "XyzAbc" can certainly do this.
    In addition, there is the laborious work of transposing the real results into a table that can be read. I decided to do it for the daily figures. Now that the algorithm is working, it could be adapted to a simpler simulation using weekly figures later.
    So I thought I would try it myself, using my own computer programming knowledge, and using real data from the last year. I have written 3 books on programming in GDL, so this is something I enjoy doing and it's a challenge, but not impossible. The understanding of the process and the interactions of the elements are still the more difficult task.
    I have tried to evolving algorithms that match the real behaviour of each element in the process, and have tried to discover constants that give the results that the actual borehole delivered. This is still a work in progress, but the results are better than nothing - there is progress.
  • The GSHP daily consumption figure is used, and if we assume a COP of, say 2.7, that determines the amount taken from the ground. One small error is that my GSHP figure includes the winter overhead of the circulating pump, but that is small in comparison with the main task of evolving an algorithm. There are also complications, in that the COP of the heat pump increases when the deep ground is warmer, so perhaps I should make COP better if the Sunboxes are working.
  • The Sunboxes contribute heat through the energy flow meter, so that quantity is known - approx 3,000 kWh per year. This is the easiest part of the whole program. 
  • The Infinite ground around also tops up the borehole, in fact over a year, it has to contribute about 6,000 kWh, twice as much as the Sunboxes. This is a sliding variable, and not linear. Thus if the ground is very cold, the speed of thermal restoration is very fast, if it is merely cold, then it restores slowly. If the borehole is about 12.8º, there is neither heat gain nor heat loss. If the ground is above 14º due to the work of Sunboxes, some of that heat will be lost to the outside and not recovered. This heatloss will prevent the ground rising to something dramatic like 17º. My algorithm takes all this into account.
  • Missing days?: Where I have been away, for example, holidays or conferences, the main spreadsheet calculates the daily average during the time away, so it is possible to fill in the missing days.
What this simulation shows is the volume of the borehole changing, as a symbol of the temperature changing. I could have considered colour changes, but this is less visual, and not easily picked up when it is converted to video. I have re run them as BOTH colour changing and volume changing. Around each borehole is a blue glass reminder of the original size and temperature at the first day of October.
  As we are in April 2011, I have had to use data from May, June and July of 2010, even though we had a cold May 2010, and the Sunboxes did not have mirrors installed. But for the time, it is good enough to work the animation. When I get time, I will add in for August and September 2010 too.
  I am running two simulations, one of the system running without Sunboxes, and one with. A complication is that in the real case, my borehole started from a position of having had an entire summer of solar charging, whereas the simulation assumes the same standing start for both simulations. The previous year, Winter 2009-2010 had no such charging. So I should find a way to compensate for this.
  What this is now showing is near to the real result - that without the Sunboxes, the ground needs all of the summer until September to recover its temperature. With the Sunboxes, the winter and spring have more stable temperatures, and during the summer, the ground gets warmed up nicely.

• Video of the simulation, assuming Sunbox Solar charging, assume residual heat from previous summer

• Video of the simulation, assuming Zero Solar charging, and a standing start.

These are still not quite right, but I have other work I must turn to so will come back to these. 

In the Solar charging one, the real-life temps never got below 10º in winter due to the accumulated heat from previous summer. In the previous winter, with no solar charging, the real-life ground temp went down below 5º in the coldest point.

This simulation uses rules of thumb for expanding and contracting the volume, but I shall try a simulation which really does use Kilowatt Hours in and out.

Wednesday, April 20, 2011

Using Domelight as a sunbox?

20 April '11: Here's a domelight page....

It seems to me that one answer to the cost and labour of sunbox construction is simply to use domelights on their kerb, mounted on the wall. You can get them single, double or triple skinned, clear and other colours.... try building them with or without a kerb.... so a clear 1800 square single glazed enclosure is big enough to contain two of my black polypropylene panels (1300x850). One of that size would hold also two metal radiators, say 1600x800 size.

One issue that Chris brought up a couple of weeks ago is that having a flat front face with the existing boxes, I get a lot of loss through reflection in morning and afternoon, until the sun swings round and penetrates more directly. Also, I have to use 6mm thick polycarbonate to get enough stiffness with a flat surface.
A curved front would improve admission of heat either side of midday, and would be stiff enough at 3mm, half the thickness - allowing more sunlight to enter. It would give one a marginally larger air volume to warm up with the greenhouse effect.

Underfloor Pump gets a meter

19 April '11: I am keen to find out exactly how much power the GSHP is using, Winter and Summer. One thing that makes the calculation more difficult is that the underfloor heating pump is spurred off the GSHP - which has to send power when the external temperature sensor drops below 15.5º C. At equinoctial times it is off in the day and on in the evening.
    So I obtained another E110 meter which intercepts the cable to the floor heating pump and will record the kWh precisely how much it uses to one decimal place (it remembers the score, even when turned off).
   The other slight unknown is the ratio between heating and DHW. The IVT displays a percentage for this, and during the winter, the ratio was about 18-82, and now that the summer seems to be here, this is moving to 20-80, or 21-79. This ratio is from the time the heat pump controller started, and that date was mid-July 2010. It does not provide me any other way to get a more accurate seasonal balance of workload.

Weather comment
By the way, the weather has been unseasonally warm for this time of year, and that certainly helps the electricity consumption to break all records, week after week. I wish it would rain for a while, to water the garden and refill the water butts. We keep having the 'sunniest day of the year'... when will we get back to normal, i.e. blustery, rainy days, showers etc!?

Sunday, April 17, 2011

Window mirror fitted

17 April '11: Well I have fitted a mirror over the kitchen window, although it's too late in the season to make a difference. It is intended to increase solar gain in equinox times on sunny days - speed up incidental heat gain, and reducing the heating load on the house.
    This angle in the photo doesn't work, by the way. I have to do some fine tuning, by eye. The angle needs to be steeper. The whole mirror swivels (bolt and spring washers) and can act as a shader to the window in the height of summer. Also, now that it is up, I see that it might be better closer to the wall.
I think a foot mirror might be better, bouncing light upwards through the window to the ceiling, but that can't be on the ground floor windows as they are too low set to see the Sun, and there is a safety issue of walking along the side-path. I have rounded the corners, but they are still like blades. I might yet fit foot mirrors to the upstairs facing windows, but they will only reflect some heat+light into bedrooms, not a living space.
   There is an issue with the length of the brackets. For the foot mirrors they can be longer, but seeing these, I guess that they should be shorter for the top mirrors. Sunlight is coming through the gap - it would be better if the top ones hug the wall more closely.

Friday, April 15, 2011

Thermal storage is a historic skill

15 April '11: I was chatting to Chris Wood today and we were discussing the 'patentability' of underground thermal energy storage. We both feel that the principle is so long standing, going back millenia, that this is unrealistic and unethical to do. The only thing that could be specifically patented would be the Box of Tricks that makes one particular system work - i.e. the particular set up of thermostats, switches, valves, tank and circuit design that made it different from other systems. You can as much patent underground storage as you can patent Newton's laws of motion. They are named after him, but he doesn't demand a royalty from every bicycle, car and rollerskate that is manufactured.
   I have been in Stone age caves in France, where it was clear that there were food storage larders in the coolest parts of the cave. Most of us have heard of 'Ice Houses' and if you have even visited an English country house, there is usually a small disused building nearby that is still called the Ice House - these were usually near a lake, and stored the winter ice. Ice houses have very highly insulated walls and roofs. The Persians mastered the ancient art of making and storing ice many centuries ago, and even transporting it on camels.
 Ice storage and delivery used to be a common part of the way of life in British cities, indeed, I remember taking a photograph of the demolition of the Ice Storage company building in Liverpool, in the sixties.
 There is a good entry in Wikipedia on the topic:
Here's an article about Ice storage in Boston, Mass:

When I read the article about underground storage at Heathrow recently, they referred to the thermal hypocausts of the ancient Romans, still visible in excavated villas and forum buildings today (hypocausts are about distribution of heat, not storage, but they are part of the big picture.).
Here's a picture of an Ice house in Kingswood, near Bristol:
Or this one, where the house was demolished, but the Ice house remains:
The Findhorn Ice house, for cooling fish:

So back to heating - why do we not use the warm equivalent of an Ice House for our thermal storage? - a thermally insulated room, perhaps the size of a small swimming pool, filled with earth, and with pipes circulating heat from a solar panel? The reason is that the volume required to hold enough heat to provide for a house is far far more than can be stored in an insulated container unless it is to be larger than the main house. I was disappointed to discover that the theoretical thermal storage of one cubic metre of dense clay is only 0.5 kWh per degree K, and that is why you need such a deep borehole - a few thousand cubic metres per house.
   A large room sized volume would only work with a PCM material (wax or salt) and if insulated, there would be a finite limit to the amount you could inject or withdraw. Typically PCM materials have a thermal capacity of 50 kWh as they go through the phase change. That is 100 times as much! If the phase change requires a range of 4 degrees to fully change, that's 25 times better! They have a storage range above and below the phase change, that would be similar to clay or water (depending on their state).
   For house heating and DHW, you need what we have, in effect an infinite volume, but with an seasonally addressable volume of about 3,600 cubic metres. An insulated container of this size based on clay would have to be the footprint of our house and 50 metres deep, and you would have to calculate the area of solar panel precisely to ensure that the heat taken out was equal to the heat put in, as there would not be access to the infinite soil around. You could tune it by having more solar panels added later, or by having supplementary heating. Also, if the house is insulated to Passivhaus standard, the volume could be reduced.
   Unfortunately the words 'Ice House' is now adopted by bars, graphics agencies, music bands, and heaven knows what else, so Googling for 'Ice House' and finding something useful requires a lot of patience.

Solar top up to System First energy foundations

System First foundations. These can be adapted
for underground thermal energy storage
15 April '11: I am having a correspondence with Chris Wood of Bullivants, who is contemplating ways to provide solar earth charging to his System First energy foundations. He has managed to get two of the black swimming pool panels that I have used in the Surya Sunboxes, and will build a small rig. They are donated by Ice Energy. He is at the moment intending to set them up unclothed in boxes, and this will be an interesting comparison with my enclosed boxes, and you can be sure that his data collection will be very thorough.

I don't think two of those panels will produce enough worth measuring, if they are uncovered. During summer when temps are regularly at about 20 degs, we get over 40 degs in boxes ... A good delta T ! I wasn't prepared to try mine without the sunbox enclosures as I want to move as rapidly as possible to low energy consumption of even to carbon zero. I don't have time to give a year to data collection from a system with reduced performance. If he wants a design and build Sunbox installation over his panels, I have invited him to ask for assistance. We could try 4mm polycarbonate instead of 6 to improve thermal entry. If his sponsors pay for the materials, I will provide my time and labour free, as it is part of my research.

Two of the Solar Focus panels
Chris replied with a message: "Hi David, the main heat transfer in the summer when we have direct beam sunlight is not through conduction with the air. It mainly due to the absorption of light i.e. irradiance on the black surface and thus heat transfer direct to the fluid. This effect has no relation to the delta T with the air. Effectively you could argue that your sunboxes are providing a boundary layer of still air, which in turn lowers the heat loss to the ambient i.e. an insulating effect but maintaining the pathway for irradiance. How much this is of  benefit is hard to quantify. Efffectively it's the same effect as the glass on front of a conventional flat plate solar collector,. Conversely the polycarbonate will have a certain reflective component which will reduce the irradiance upon the panel. Look up what the 'g' factor of polycarbonate is. I know some glass is 0.5 meaning that half the irradiance is reflected." Chris

I replied: "Chris, I'm aware that my panels take time to get going in the morning and I suspect that the steep azimuth angle of sun in early morning is causing most of easterly heat to reflect, hence I have fitted the corner mirrors. The GSHP often demands heat at that time of the morning for the DHW so they come on due to delta-T." I would also add that I am aware that a chilling of the air cavity can occur (due to the black chillers working too well), making the air cavity colder than the ambient air, for a short period - until the greenhouse effect works again and warms up the space again. I also suspect that the 'clear' polycarbonate that we have used is not completely clear as some of the labels on it suggest that they reduce sunlight. I cannot get completely clear polycarbonate without this solar feature. We seem to get enough heat already, but I wonder if 4mm polycarbonate would have worked? 6mm seems good for structural stiffness, and 4mm would require more aluminium framing.

What will this lead to? Well, my sunboxes were limited to 200mm projection from the wall so that they have free planning permission. This causes them to be shallow rectangles with a very small east and west surface area. A further development on another house would make the sunbox have a larger air cavity, with perhaps an octagonal plan (like a traditional bay window) so that it would pick up more morning heat - reducing the amount of heat lost through reflection. Perhaps a curved front surface would be possible, either with thinner polycarbonate clamped at either side, or by curving it thermally.
  The octagonal plan would be complicated to build with more edges, and the curved front panel would be difficult too, with the difficulty of sealing top and bottom. A flattened polycarbonate dome would be best, if it has a rectangular footprint. Some of these may be available as proprietary mouldings.

Heathrow to use solar earth charging!

15 April '11: I am ecstatically happy to see that the Guardian prints a lead story about Heathrow and Solar Earth Charging (or UTES as Nic Wincott calls it, or IHT as ICAX call it). I don't know who the company advising them is (I would guess it is ICAX) but all health to them! This is either a case of 'great minds thinking alike', or more likely, 'an idea whose time has come!' 
   The idea of solar earth charging has gone from 'rubbish' (as said by one of my colleagues) and 'a malicious hoax' (as said by one of the more malevolent moderators on the Navitron forum), to a great energy-efficient and safety-providing idea being adopted by one of the world's leading airports. Heathrow may be the first airport to try this - excellent!
    I have written on here before about the principle of charging the ground without needing a heat pump, eg, for defrosting water tanks on farms, or for defrosting roads, where a heat source with a starting temperature of about 12-13 degrees is enough to defrost, without any more energy consumption than the cost of a circulating pump. All of the summer cost of the pump can be met with PV power.
   ICAX have pioneered the idea of collecting summer heat from dark tarmac and storing it under a well insulated building (so it can't escape far), and my working system with vertical boreholes has provided so much additional efficiency to the heat pump that we can feed the entire annual requirements of the GSHP from the electrical capture of a 4 kW Photovoltaic (PV) array - making our house carbon zero.

With a mere 4 sqm of black panel inside our Sunboxes, we have managed to keep our deepest ground temperature above 10 degs throughout the winter, even at the end of December 2010. An airport is a secure location with acres of free space, and the budget to pay for the laying of underground pipes and cables. It can lay out acres of solar panel to charge up the earth, sufficient to deliver liquid at above freezing temperatures throughout the winter. These do not need to be mounted on buildings, they can be low lying land structures that do not obstruct visibility, and are 'sacrificial, easily rebuildable' in case a plane rolls of the runway and crushes a few. It can also justify enough PV panels to cover the pumping costs throughout the summer and into the winter. For the 'stands' like the ones pictured above, there are acres of roof on the terminal buildings which can contain solar panels.

Burying CO2 or burying heat?

a small part of a very large illustration by Greenpeace
14 April '11: I have become pretty convinced about the benefits of storing heat underground, as long as the geology supports it - no air pockets, gravel etc. As the delta-T is not too great, it will stick around until the following winter, for heat pumps to retrieve.

I have never believed in one of the other underground ideas, that of pumping CO2 underground. Gases in a heavy medium always want to escape. A balloon filled with CO2 above sea level will fall, but put that balloon below the sea and it will pop up as quickly as a submerged beachball. The delta-D of density is enormous, and rock/clay is more than twice the density of water.
  It seems another of the strategies designed to try to enable the public to maintain the present high consumption of power. It's true that power generation will continue to be high, as we move from a gas based heating to more heat pumps - we are going to have to rely a lot more on home generation and renewable sources. But I declare that CO2 burial will not suddenly make emission from coal burning acceptable. Pumping CO2 underground uses a lot of energy and as the geology is very three dimensional (fissures and uneven strata) none of it can be guaranteed. Also, there is increasing statistical evidence that forcible pumping downwards of gas can be associated with increasing risk of earth tremors or worse.
  Greenpeace have published a very authoritative diagram, illustrating some of the hazards of trying to depend on this technology. Click on the illustration, or click here

Tuesday, April 12, 2011

Cleaning the PV panels

12 April '11: I am happy with the solar capture of our PV roof this month, the weather has been good. But one has this slight suspicion that it is not as good as when the panels were new.
   This last few weeks have been a very dry month - I put a wheelbarrow out about 10 days ago and it is still completely dry. If any night drizzle fell, it evaporated quickly. In these conditions, even self cleaning PV panels have a problem. There isn't enough rainfall to flush them clean (taking advantage of the self cleaning coating). Even a light drizzle will carry amounts of atmospheric dust (either falling from the sky or stirred up by daytime motor traffic) and this evaporates before it has time to run off, leaving behind a film of dust that cakes up in the sunshine.

So on returning from New York, one of my first jobs was to set up a ladder and the hose, climb up and give them all a good squirt of fresh water. I can't reach them all with a brush, but am hoping that a strong water flow from the garden hose will help them. They were very 'matt' in appearance before being cleaned.
  I will keep an eye on the figures for next few weeks and try to gauge if that improved things.

At this stage I need to add a 'Do not try this at home' rider. 
As I have built and adapted the Sunboxes, I have got very used to climbing up and down a ladder, and take precautions with a harness, helmet and steel capped boots. No fear of heights, and a very good ladder with a clip-on safety feature that makes it more stable. The job needs a hosepipe end that is controllable and can turn the flow on or off and project it a good distance. So if you really think this needs doing, get someone to do it for you at the start of the summer. See the article written by Karina Wells:
Brian cleaning Karina's panels, using the Velux rooflight
To contact Brian call him on 07974-550118 or email :
My regular window cleaner has a very long brush with water pumped down the handle like this, and he might be prepared to do it, although I think window cleaners hate going up ladders - steeplejacks seem to be more brave. Brian is part of the West Bridgford Skills Exchange, so if there is something useful you can do for him, he will do this for you!

Mid April update

12 April '11 : I have been in New York for a week, so hot water use has been reduced a bit, and the week has also been very sunny for this side of April. Mrs N-C has been here, so the house still needed evening heating and lighting. The Sunboxes work by themselves of course, even if the GSHP is not running. So we have broken three records in the last week :
• The annual House consumption really has dipped below 5,500 kWh.
• The annual GSHP consumption (incl. the circulating floor pump) really has dipped below 3,500 kWh.
• The annual Sunbox capture has risen above 3,000 kWh. (although I had been mentioning a round figure of 3,000 for many months, the precise figure was 2,980 until this week of April).

Plus a few more things:
• The deep ground temperature is rising slowly, and was 11.6 ºC compared with 9.2 ºC exactly a year ago (a month after the Sunboxes first installed). That is equivalent to a stored reserve of about 4,000 kWh of heat more than in the year before - and it is only April, with months of summer to come.
• The average daily heat pump consumption from Jan 1 to April 11 2011 was 14.04 kWh whereas in the same timeslot of 2010 it was 21.21 kWh. This is a 33% improvement, helped by the very mild spring we have experienced, and the cold spring of 2010.
• The average daily House consumption from Jan 1 to April 11 2011 was 19.65 kWh whereas in the same timeslot of 2010 it was 27.85 kWh. This is a big improvement, as explained above.
• Looking at the Weather effect, the ratio of Degree Days for Jan 1 to April 1 2011 was 896, and it was 1100 in 2010. This means that the ratio was 18%, whereas the performance improvement in the GSHP was 33%.

Next Step? Well, logically, it has to be to dip the House and the GSHP another 100 kWh lower, to 5,400 and 3,400 respectively. I will be amazed if this is possible, but an average of one kWh per day less during the summer season will achieve it. If the autumn is mild it will be achieved.

17 April '11 Postscript: Well the week since the 12th has not been so sunny, so the PV and SB count is slightly lower. But I am glad to see that the electric consumption figures for the House and the GSHP have fallen further - the record is extended. The deep ground temperature has risen above 12ºC at last.
   One year ago in the same time period was a cold week so  it's possible that the readings for Sun. 24 April will be even lower! Next stop, 5,450 and 3,450 !

Sunday, April 3, 2011

Insulation, Technology and embodied Technology

3rd April '11: Reflecting on our time at EcoBuild, and the annual results from our PV/GSHP/ Sunbox combo, I wanted to say something about Technology vs Insulation - remembering what our final target must be - to reduce carbon emission into the atmosphere.

Insulation is undoubtedly the first thing we should do, it is a must for all new building, and we should over insulate in these cases, i.e. go far beyond existing UK Building Regs to meet the standards of Passivhaus.

For existing buildings, it can be extremely difficult, even if one is not in a conservation area. One experiences the full trauma of builders, scaffolding, redecoration etc, without an easy way to compute payback. There are the arguments about whether to do it internally (in a rather limited way) or go the whole hog and do it properly, external insulation. Payback is not strictly computable unless you were keeping 5 yrs of energy records prior to the installation, and keep 5 yrs after the insulation, to compare. However, the Comfort return is immediate. If you know someone who has had the exterior insulation, they will say how the house got warmer and the boiler less noisy even in the first week while the work was still being done. If you are going to have external insulation, it is advisable to take it at least half a metre below the ground line, if your paving or flowerbeds can be lifted briefly. In the 1980s, I had my Semi in West Bridgford comprehensively drylined, and whatever it cost then didn't matter, as we had 5 yrs of thermal comfort, and we got the money back when we sold it, the high insulation being a good selling point.

Advocates of Insulation can be a bit single minded (as can be advocates of Technology), but it is clear there has to be a balance in their favour - in high rise for several decades we have had generations of buildings which ignored insulation in favour of glass, and used Active technology to counter solar gain and heat loss by cramming the building with HVAC equipment - the Seagram generation of high rise to name only one - their only concession to passive design was to use very dark glass, which reduced solar gain, but added greatly to the energy cost of lighting. Millions of ordinary houses in the UK have been fitted with central heating systems in the last 40 years, without adding to the insulation.
   The insulation-boys have an overwhelming case for major improvement in the 98% of the existing housing stock - but it should not stay there - we need to consider the overall Energy equation, and find ways to reduce our Carbon emission, beyond just insulating.

Technology: Once you have insulated, what next? Well, the Passivhaus standard is dependent on MVHR, because part of insulation strategy is to make the building airtight. On my house, the ventilation heat loss exceeds the fabric heat loss. On a PassivHaus the fabric heat loss becomes incomputably small compared to the comings and going of incidental heat gains, solar gain, and heat lost through ventilation. Therefore, MVHR is a mandatory part of the Passivhaus standard - this is technology. However, it is not much use in a leaky house with few people living in it - the result is to blow cold air in.

Even if the building performs so amazingly that somehow it doesn't need active heating most of the time, it would not be possible to sell a house or apartment that had no heating system in present market conditions. The advocates of Passivhaus believe that a no-heating house would be possible, but I ask: How about taking into account Lifestyle conditions? the Architect cannot predict or prescribe the occupants, whether they are elderly, ill, very young, or not good at opening and closing windows or keeping the MVHR in good order. Incidental heat gains cannot totally be relied on as energy efficient lighting and A-rated appliances all produce less waste heat that in former times. You cannot tell them that they will have to wait till next Thursday when there is a forecast of sun, just because they left a window open.

My reference to EcoBuild was that Prof Wolfgang Feist told me that our New York skyscrapers should be able to work without any heating - but I would reply that this is forgetting that these people are 200 metres altitude with a biting sea wind, bitter winters, and the occupants are Americans not Germans, and they just expect things to work - they won't all live the ascetic lifestyle. You do not buy an apartment in a billion dollar building in the classiest residential location in the entire city (one block from Broadway, overlooking Battery Park and the Statue of Liberty) and then find it has no heating system, and that they have to walk up the stairs because the elevators have been omitted!
  (No Joke, I recently heard from a student in another module, designing 5 storey flats in Nottingham city centre had been told to leave out the elevators to save energy - but had not been told about Passivhaus construction for the apartments! Elevators are likely to use only about 3-5% of the building's energy bill)

Another thing, argued in an earlier page on this blog, is that we are biologically conditioned to rely on technology. We lost our hair many millennia ago, and have relied on clothing. Look at your clothing now, notice the weave of the fabric, and consider how better that is than a skin peeled off a slaughtered bison (and did you wrestle the bison to the ground or did you use a spear?). Go to the fridge (technology) and consider whether you would eat the meat in there raw, or whether you would eat your potatoes raw. Unlikely. The salad and fresh fruit came from Kenya or Peru. Almost everything you eat has to be cooked, and if it is a preserve, it was cooked then, and put into a container that required technology to make. Unless you live in a climate where salad foods grow all the year round, you are dependent on food preservation and cooking - technology. If you buy fruit or salad out of season, this is Embodied technology, otherwise known as food-miles. Insulation itself is a major technology, even if it is not active. It also has an embodied energy of manufacture, and there is a science to its application.

I have colleagues who regard Renewable Technology on buildings as 'Bling' but I notice that they don't apply it that restriction in their own lives. They have an iPhone (surely it's easier to write someone a letter or shout than use that?) and drive sophisticated cars like a BMW Mini (surely it's easier to walk to London, or perhaps get a bicycle?) They live in georgian or victorian houses and think that a condensing gas boiler is enough technology to save energy with.

The reality is that we live in a world of technology. We expect planes to be fail safe, GPS to get us home correctly, pharmaceuticals to be correctly formulated and labelled, Google to find the information we are seeking. To do without technology now reminds me of the spiritualist healer who rejects all modern medicine and relies on prayer until their children die (recent court case in Paris, March 2011). Buying a car now, even the simplest one will be expected to have a heater, a radio, fuel injection, independent suspension and a catalytic converter.

It is possible to improve the climate of buildings with less reliance on electrically operated systems, such as solar shaders, vertical solar chimneys, wind catchers, water pools etc. and some of these transform the appearance of the building. To me they are Technology - Passive technology, not ones with motors, things we incorporate into buildings that are not merely rooms to live in. Their construction can involve extra investment in materials, and are technology, just as the weave of the fabric of our clothing or the glass of our preserving jars are technology.

With very little dependence on materials, but good adaptation of our IT knowledge, we can use Smart technology, such as thermostats and sensors, building management systems which recognise climate, time and the activity of users, and reduce the power consumption of the Active systems, and by opening or shutting louvres, to make the Passive systems work better.

I believe that our Peveril Solar house is adequately insulated, and I cannot do much to improve it further.  Partial MVHR is something I may try to build in, in the future. However, at this moment, the virtuous triangle of technology - PV, GSHP and Sunboxes - has taken it the extra distance to make it Carbon Zero, all working around the firm foundation of a well insulated house.

Surely it's time for Architecture to accept 'technology' as much as we have done in our phones, cars, planes and media - whether it is active, smart, passive or embodied - accept its inevitability! Enjoy! But we must learn from the mistakes of the previous century. Slapping active technology into bad buildings can be very stupid, and we don't need any more dark glass Seagram Buildings or their descendants which litter the boulevards of Dubai. We don't need experts saying that fitting a condensing boiler into an uninsulated brick house is suddenly making us eco-efficient.
      We need an integration of well performing environmental design with passive and smart technologies that make best use of a new generation of active technologies, and reduce the emission of carbon to zero. To compensate for the millions of inadequately insulated houses, new ones should go beyond Carbon zero and generate more power than they use. 

Include hot water in Carbon zero equation?

2 April '11: I have to write this on the second to avoid the reader thinking this is an April Fool. I am now convinced we have achieved Carbon Zero for the Space Heating AND the Hot water (DHW).
    PV roofs are generally limited to 4 kW by the Feed in tariff system, and with a south facing roof, this might capture 3,600 kWh at best, and for our house with an east facing roof, we seem to be averaging 3,250 kWh, so this provides the target to beat.
   Following the Transition movement's motto of "Power Up, Power Down" we need to do both - to achieve a good power generation up to a target figure, and to reduce our heating requirements down to or below the same figure.  The efficiency of the GSHP has improved now that the deep soil below is warmer, so there has been a continuous improvement in performance, week by week and the figures are converging. (and we are being helped by the Spring weather being unusually benevolent!).

   Sometime last year, beginning of October, the annual totals of the PV roof managed 3,325 kWh and the GSHP consumed just under 4,000 kWh. Assuming that the space heating is 75% of the effort, that would be 3,000 kWh, which is below the capture of the PV roof, ergo, the space heating was carbon zero - we put electricity into the Grid, and we draw less than that total from the Grid. The Sunboxes had 6 months of work to this point, so I didn't really expect it to get better.

I found some more ways to make improvements in reducing power consumption:
At that point, I fitted the aluminium mirrors and voltage regulation. Earlier, I had added more insulation to the internal water tank in the GSHP. During the winter, I fitted a cylinder thermostat to stop the IVT's persistent water overheating problem. My wife decided that we would have the thermostat turned up for the winter by a degree, but in return agreed that if she wants to sleep in the bedroom with the window open even on the coldest nights, the bedroom door could be closed (bargain!)

  We then had the coldest November and December in weather history, and somewhat depressingly, the annual PV fell to 3,236 and the annual GSHP rose to 4,245, and for a while we had zero input from the Sunboxes (and the meter went wrong for a short while). Our 'annum' included the double winters of 2010, the unusually cold Jan, Feb and Mar, and the exceptionally cold Nov and Dec.

During the Spring of 2011, we have had mild weather and things cheered up. At this moment, we are getting close to 3,500 for the GSHP and the PV seems to have settled to a safe annual average of 3,250. My dissertation student Lyndsey pointed out that I should deduct the consumption of the floor pump to arrive at a more accurate figure for the GSHP. In fact, I propose to buy a meter specially for this pump, so it can be deducted precisely.
  I calculate that the underfloor heating circulating pump uses 250-300 kWh during a winter. Deducting that now brings the consumption of the GSHP itself down to equal to or less than the PV roof. That is its entire effort, including the domestic hot water.  3,250 equals 3,250 !
   There is another 6 months before the anniversary of the mirrors, so I hope that further improvements in efficiency will be achieved.

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