Thursday, September 30, 2010

Photovoltaic Anniversary 2009-2010

30 Sept '10: Today is the completion of the first full year of PV, so it is a chance to review the result.

  • In the previous 2 years, since moving to this house, the annual total electrical import was 8,500 kWh. 
  • In the year 1 Oct'09 to 1 Oct'10, the electric import was precisely 6,090 kWh, a saving of 2,410 kWh - pretty good. 
  • The roof panels harvested 3,325 kWh in that time. 
  • Part of the reduction is a general tightening of lifestyle. We were good before about turning off lights, but perhaps we have tried even harder this year to make sure that lights and standby devices are off. Metering daily has the effect of making you try harder to do better next time.
  • The Sunboxes have worked since mid March'10 so that will also have contributed, but as that has been mostly over summer, it won't have shown up significantly. The loft pump has used 73 kWh, but that is mostly in the day and covered by the PV roof.

Wednesday, September 29, 2010

Insulation meeting on 19 Oct

Eco adaptation isn't only about putting PV roofs up and fitting heat pumps. The NUMBER ONE and TWO things are to
  • improve insulation! and to 
  • control draughts!
Please come to a meeting at South Notts College (Ruddington site) 19th October for a good presentation and discussion about these. One of the guest speakers will be David Hill of Carbon Legacy, a sponsor of Rushcliffe Solar, and an associate in the Charging-The-Earth project.
For new buildings, these two principles are also the leading principles in 'Passivhaus' design.

Tuesday, September 28, 2010

Nottingham Evening Post features Rushcliffe Solar

28 Sept '10: Many thanks to the Nottingham Evening Post (and Jon Robinson) for a well written article on the Rushcliffe Solar project.

Quite often when you see something about you written in the media, you are grinding your teeth at the inaccuracies, but Jon is an experienced writer on environmental matters and has written it perfectly. I am glad to see that he got a comment there from a member of Rushcliffe BC.

So, congratulations to Jon on a good write up, and I have only one small addition which is to add that people wishing to get a free PV survey from Rushcliffe Solar should use the website and leave their details on the ENQUIRE Tab.

I am very happy to see that the photographer, Jemma Cox, included the Surya Sunboxes prominently, and I hope that they will run a feature in January when the winter is biting deep and people are more interested in discussion about heating systems. If you want a copy of the photo above (but why would you unless you are in my family), it is reference C260910JC1-2
Rushcliffe Solar is a Photovoltaic campaign jointly initiated by Rushcliffe BC, Transition West Bridgford, Energy Saving Trust and University of Nottingham, with subsequent sponsorship by ten solar installers.

Watts per Square Metre?

27 Sept '10: Someone on Navi tron forum said I was claiming more heat capture than the sun could provide. Errr?
 What I have been averaging from the sunboxes is about 1.1 kW when the pump is working - day or night, sun or cloud. Best days are averaging 1.7 kW during the day, and about 0.8 kW on a poor day. If conditions are worse, the thermostat doesn't let the pump run. There are four square metres of black collector facing south, vertically mounted. Averaging at 1.1 kW, that is 275 W/sqm. As my panels are vertical, there is a natural bias for them to collect less in summer (I don't want so much of that anyway...) and to collect more in winter (when it is more desirable).
  According to my solar radiation meter on the roof, the peak insolation at the best of the middle of the day in summer is 900 watts/sqm, on the very best day of the year, 17 June. The average for the days seems to be about 275-300 w/sqm, and we have to consider that the sunbox pump sometimes works for 5-12 hours a day. As I have 4 sqm, I am getting an average of 275 w/sqm, and of course this ought to be impossible, suggesting that on average, they collect everything that the sun is sending.
  However!  the panels are also getting much of their heat from the air temperature, indeed, on cloudy days, all of their heat is from the air (and it is helped by sky brightness). Their efficiency is enhanced by the fact that there is a powerful water pump driving chilled glycol through them and the ground loop when the heat pump is working, exploiting the delta-T whenever there is one. (when the heat pump is not running, the circulation is reduced to a humble 30W water pump).
   If I had convector fins on the back like you have on a steel radiator, the capture might be even better! The side panels of the sunboxes are transparent, so they pick up sunlight when it is at a slanting angle earlier than one that has opaque sides.
   When the sun does shine, their output boosts to well over 1.0 kW, and the recent addition of the mirrors has boosted their sunny performance even more, to nearly 2.0 kW.

Monday, September 27, 2010

Adjusting the Trigger during winter

26 Sept: Trigger Temperature - this is the temperature in the Sunbox, which is enough to start the sunbox pump going.

On the programmable thermostat. I reduced the trigger air temperature to 19ºC a week ago, and this week, I adjusted it to 18ºC. As the winter progresses and the ground chills, the delta-T should remain at 5-7 degrees - I can review this every week. During the summer, when the ground is static at just over 13º I used 20º in the Sunbox as the trigger. A week ago with the ground at 12.6º, I reduced the trigger to 19ºC. This week, I adjusted it to 18º and the ground was 12.1º. As long as there is a difference of more than 5 degs, it is worth adjusting the trigger weekly. To be consistent when I take the ground temperature, the heat pump is off from 10pm onwards, and the ground temperature measurement is taken at between midnight and 1am - having had time for the ground to rest.

Sunday, September 26, 2010

Strutting the sunboxes

26 Sept: Notice that a week or two ago, I balanced a ladder against the centre point of the sunboxes, to fix the aluminium mirrors. It was a bit risky and bouncy, and not good for the panels either.
   I had a dizzying time today, up the ladder again, now fitting a compressive member (strut) in the centreline level with the top rail, that supports the front panel from deflecting if a ladder is loaded against it.
   I don't know what else I shall need to do up there for a while, but it feels a lot safer up there with a metal strut. I also replaced a few of the Screws with Rivets. So much time was wasted trying out different screws and different hole sizes for the screws, what a pity that I didn't try riveting before. The connections are firmer, neater, and quicker to do, will not come undone, and can allow me to use thinner aluminium, if the section is non structural.
   Sorry, while high up there (best not to look down....), I didn't feel like taking a picture...

Saturday, September 25, 2010

Welcome the Winter!

25 Sept: Welcome to Winter? This seems a very odd thing to say, but for this research project, I am eager to see how the system performs in winter. Today is clear and sunny, but at 9º outside, it's the coldest day of the half year and similar to many days in February or March.
   Looking at it this morning, during a heating cycle, I see that it is 22º in the sunboxes, the GSHP is sending them glycol at 6.8º and the glycol is returning at about 9º and is coming back up from the ground at 12.0 - the exact figures fluctuate, as the collectors are cooling the sunbox interior, and then as the sun is still climbing in the sky and swivelling to the south at 10am, it warms them a bit more, and the air temp goes up again, the HP adjusts its temperature down a bit.
    If you are geeky enough, it is an interesting process to watch. We must now get the datalogger going again - it has been going all summer actually, but I need Blaise here to check it on his laptop to make sure that all the sensors are still connected, attached, and transmitting!
   During this cold day, it was actually one of the best of the autumn for sunshine with 15 kWh of photovoltaic energy harvested, and our roof galloped through and beyond the annual 3,300 kWh barrier. Having expected only 2,850 in a year, this is particularly satisfying. I guess today's score is helped by the cold air temperatures in the morning.
  At the end of the day, I noted that the Surya Sunbox energy harvest was well up - perhaps it is due to the mirrors, as it was sunny day, and the sunboxes were averaging 1.69 kW/hour when running which is so high that it is almost abnormal!

Friday, September 24, 2010

Dissertations ahoy!

24 Sept: I am getting enquiries from students about topics for dissertation. Last year, I had two, but both of them were handicapped by the fact that the Sunboxes only started in Mid-March, so some of their writing was hypothetical. Now we have a fully working and monitored system, so there is much more to discuss. What is even more interesting for them is that the Peveril Solar is no longer an isolated project, we are building the other in Leicestershire, which is similar but with slightly different parameters, so we all have a basis for comparison. Noting these variations (below) we will compare figures at various points during the winter. The weather is now cold enough for the heating to be needed, so we will be having performance figures even in the month of October. We are are planning to have the East Leake scheme running during October.

Differences between Peveril Solar and East Leake:

1. Metal collectors not Plastic – using radiators not swimming pool panels - better admittance, but narrower pipe diameters.
2. Stack the collectors vertically, not widthways – taller box, more stack effect at top of sunbox.
3. More airtight construction of sunboxes, although still constructed with hinging faces to make panels fully accessible. (production models can be more sealed.)
4. Not using mirror concentrator – unnecessary with a tall sunbox, necessary with a wide sunbox.
5. Position lower down on wall, almost reaching the ground (no scaffolding)
6. Plumbing to be on the ‘Trickle-while-we-work’ basis not on the ‘Trickle-and-Whoosh’ basis – but using same thermostatic control system.
7. Larger host heat pump and house twice the size, and borehole twice the length as on my house.
8. Hot water heating supplemented by 48 solar vacuum tubes.
9. House heating supplemented by Heat Recovery.
10. Brick behind the collectors in Peveril, but timber boarding in East Leake, No thermal capacity in wall - so how do we compensate? thin metal sheet behind to enhance air temperature in the box?

A really important similarity is that the weather pattern is near enough the same: 12 miles away, we will have matching sun, cloud and rain patterns, so the spreadsheet can be directly compared.

Thursday, September 23, 2010

Design resolved for East Leake

22 Sept '10: Here is a 3D model in ArchiCAD of the Surya Sunbox 2 as it should appear on David's wall.
    The front could be done of one enormous sheet, but there are transport and erection problems with that, and a bigger problem if one has to hinge it out for maintenance. So it is in two easily hinging out panels, just a bit larger than on the Peveril House.
  We will not use the reflective solar concentrators as the aspect ratio of the Sunbox is vertical and the mirrors would be less useful than on a wider aspect ratio, as on the Peveril. If the mirrors on my house prove to add 5% or 10% to the harvest (this will be difficult to tell as we haven't got the previous Winter's figures to compare), they can be added to David's Sunbox next year.
  We have a finalised cutting list for Polycarbonate and David is about to order. Then I will order the aluminium sections. As David's company is Carbon Legacy, heat pump installers, I can safely leave the fixing of the radiators and the connections to his team, providing they follow the simple circuit diagram.
  The illustration below shows what Three 60m deep boreholes look like at 5 metre spacing, relative to the size of the building that the Sunbox is attached to. These have a combined volume of 6,500 m3, about 13,000 tons of soil.

  Meanwhile we are having a lively discussion about value engineering.
  1. Prototypes always cost more than production models, so how cheaper can this be made? Does it need to be? - considering that it is a fraction of the cost of a solar water heating array of 4sqm, and producing more kWh/yr than that. 
  2. Although the metal radiators might capture more energy, we are storing it in a very fuzzy unmeterable store, the deep earth, so why not accept and use the much cheaper plastic panels for production models? In the meantime, use the metal rads in the interests of research. 
  3. Glass is the same or slightly cheaper than Polycarbonate, but there are about 5-6 reasons why we can't do it with glass.
  4. What happens to the 3,000-3,800 kWh that these may produce in a year? Well if David has to PULL 12,000 kWh/yr out of the ground, and these PUT down 3,000 kWh, then those poor little kWh do not have time to escape before they are being pulled back up - making it 100% efficient (unless there is a nasty groundwater bearing gravel layer that may lose some of the heat).
  5. There has been a lot of bad press recently about GSHPs (since the Energy Saving Trust report of early Sept) and it is rumoured that they are not as good as expected, nor as well installed. Do they deserve grants or any kind of Feed in Tariff in such an inefficient form? 
  6. So, if Heat pumps need a bit of help to improve their credibility, do these Sunboxes represent a lifeline, perhaps an 'essential' add-on that should be included to make them more cost effective, and attract a higher Feed in Tariff?

Tuesday, September 21, 2010

Design advancing for the 2nd Sunbox installation

20 Sept: I have had some good iterative discussions with my friend David Hill about a Surya Sunbox installation in Leicestershire. He has his own team of Plumbers and electricians, and already has a Dimplex ground source heat pump supplying a house twice the size of mine, with a triple borehole - so it is a challenge.
  David comes on board as an associate in the research work, paying for materials, while I provide the system information and spec freely, as part of the research.
  I only have to design and specify the components and his team can build most of it. My only physical building task will be to build the actual polycarbonate and aluminium Surya Sunbox. David will record weekly achievements of the system, comparing the numbers with previous year's numbers.
So far the design is 2D like this, but will be 3D soon....
We were going to fix the Sunbox central and high up on the gable, but there is a permanent Trampoline close to the building which would be dangerous for anybody jumping on it. So the Sunbox is to one side and low down, requiring only a trestle for construction, not scaffolding. It will follow a similar pattern as the Surya Sunboxes mark 1, but will vary, in the direction of my uncompleted Savita design. That is, we are using 4x Metal Radiators 1800x600 arranged horizontally in 2 stacks of two, vertically organised with a 2050 x 2900x6 front panel. All the plumbing will be within the Sunbox.
   I wish I had made a larger single box for the ones on my house. If I can find a way to recycle the old polycarbonate I am tempted to the very expensive idea of putting up scaffolding next year, and doing just that! - the Payback is impossibly long, but the Research is more important.

  The Surya Sunbox 2 in East Leake will show a number of things :
David [whose house this will be heating] is also
the leader of Carbon Legacy,
renewable technology installers
  1. How metal compares with plastic - both are 4 square meters. 
  2. Whether stack effect can be exploited, thanks to the vertical arrangement. 
  3. How one large box instead of two could be more efficient.
  4. Whether the components of the Sunbox can be prepared as a kit form off site, for quick final assembly on site.
  5. Whether a heat pump installer team can instal this quickly working from a set of drawings instead of me standing there with my spanner and blowlamp puzzling it out.
  6. Doing it entirely in 22mm copper and some curvy flexible piping instead of the large diameter pipes in Peveril.
  7. This one will not work by total diversion of the flow through the Sunbox as happens at Peveril, we shall be working on a partial bypass, whereby a proportion of the flow is diverted, based on the speed we set for the bypass pump.
  8. The use of the mirror is less likely as the overall box shape is vertical and the mirror only helps the upper part - whereas for a predominantly horizontal arrangement as on my house, the mirror is more influential.

    Friday, September 17, 2010

    House of Mirrors

    17 Sept: First day at work, and the mirrors have clear sunny skies. Photo is taken early morning when the sun is on the PV panels but not much on the thermal - although the interior temperature zoomed to more than 10 degs higher than the ambient air later in the afternoon.
    Some people would think these are ugly - I like them.
    They make the previous panels more complete somehow.
    If the mirrors have no effect I shall be philosophical, they cost very little, the main 'cost' was the time and risk of being 7m up a ladder for a couple of hours. But Hey!, 500,000 users of Solar ovens in India can't be wrong, so I have confidence that there will be a percentage increase in heat gain in the middle hours 1100-1400. On the first day of operation, it pulled in 14.4 kWh on a day of wintry temperatures but clear morning skies. I shall have to get used to the idea that the concentrators (mirrors) only work when the sun shines...

    Thursday, September 16, 2010

    Magic with Mirrors!

    With brackets prefixed, these are ready to lift
    16 Sept: This is a special day as I have been wanting to do the eyebrow mirrors for some time now, and only just today had a couple of hours available. Can't sleep thinking about it (anticipating the problems) so wanted to do one now, get it out of my system, discover the difficulties, and then do the second one more quickly. 
    One up, and one more to go!
      The mirrors were both ready with their brackets attached and predrilled the night before. Even lying on the ground, there is terrific reflection from them, bright and hot! (the blue colour is the protective plastic skin on them). They are 1.6mm bright alloy, with no additional stiffening required, and can be fixed at 90º to the rooflets of the sunboxes for a perfect Equinox and Winter angle. Under the plastic covering, they really are very shiny!
       Getting them up there is a bit dodgy as I have to use a ladder and tried to drill and fix them from the side, but this will not work, and is too unsafe. I am riveting them on, but you still need to get a firm grip on the riveter with both hands at the moment of truth - dangerous!
      I tried the ladder at the centre of each of the sunboxes, the safest location for working, and boy am I glad I built them strongly, of 6mm skin and stout 25x25x3mm aluminium angle across the top front face. I customised a little wooden worktable to fit in the top of the boxes so the panels don't have to take my weight, or be bouncy once I am up there. It is quite firm once the table is in position. Because the face of the sunboxes is glassy, there is nothing to stop the ladder falling sideways, so the first thing to do up there is to fasten a line to the wall brackets, and fasten myself to the same brackets. 
      Once up there, it was a case of locally drilling a hole in the roofs for the eight brackets, and then using the longest available rivets to fasten the mirrors down. Peel off the blue plastic sheet, and then get down to safety!

    Now for the important bit! Before doing this, and earlier in the day, the temperature in the boxes was about 24-25ºC.  The temperature sensor is in the east panel, the one I have done first. the sensor is shrouded in reflective foil to ensure it measures air temperature, not just solar irradiation.
       Within 5 mins of re-sealing the panels and washing the top glass, the air temperature inside zoomed up to 33.5º. The temperature of liquid coming down from the panels went up. A five to eight degree jump is what I had been hoping for. 
    It really is high up there!
    Later, it rained, so I gave up, but suddenly was clear at about 7pm, so I got up there quickly (having established a working method) and got the west panel fitted during twilight. Tomorrow is a clear day, so I hope to see how the direct sunshine will perform, and I will take a photograph.
    The benefit of these should only be when the sun is shining, strong or weakly. On completely overcast days, there will be no downward reflection. But I keep a weather record, as does my roof, so there is an indication of correlation between sunniness and improved harvest.

    Another prototype of Surya Sunbox

    15 Sept: It is important to get a comparator system to match my Surya Sunboxes on the Peveril Solar house, and I now may be able to install one.
       I have spent a couple of hours today with a friend in N Leicestershire who has a large house and office with a heat pump in the garage - he has a south facing gable wall and he is a heat pump installer already - with an intense interest in seeing how this works on a larger house with a greater area of collector. The plumbing can be done by his own team. Although part of the wall is a timber frame, the benefit is that the heat pump is just behind the wall, so the pipes will only be a few metres long. Instead of being 6m up in the air, this is on a garage wall, and needs minimal scaffolding. He already has a triple borehole serving his Dimplex heatpump.
      I will write more about it as time goes on. We are having a discussion about whether to use polypropylene or metal collectors, and I might try to angle the front face, in the style of my Savita panel design. The house that is being heated is over twice the floor area of mine, but has a heat reclaim ventilation system, so the total heating load is probably the same or lower than my house.
      As we don't know what size of radiators he might get, I can't yet design the sunbox structures yet, but will do this soon. It will be a 3D CAD model first, then we will discuss it, and if it looks good, the parts can be ordered.

    Wednesday, September 15, 2010

    Energy Foundations commendation

    9 Sept: Chris Wood's work with Bullivants was highly recommended in the Lord Stafford technology innovation prizes in 2010. See the video on the Lord Stafford site. This is about solar charging of foundations. Chris's work is based on the build up of heat in roof tiles. See the Lord Stafford page and movie You have to click on the Sustainability award, and the coverage of Chris's work is from 3:50 to 7:00.

       I strongly recommend Chris to include Sunboxes in his next project, although of course these require some smart architectural incorporation (being on the wall), whereas the roof tiles are visually 'invisible'. For the rooftiles, it seems to me that the plumbing must be a bit complicated, with many small pipes and joints! But chris assures me it is done with very long loops of small bored plastic piping similar to that used in under floor heating.
      Actually, you should also checkout the preceding minutes of the same video, as the housing scheme shown is also using solar heat in the foundations, but forming insulated boxes below the slab. We are all moving in the right direction!

    Tuesday, September 14, 2010

    Surya's little face

    13 Sept: One of my Indian students gave me this before leaving UK to return to Mumbai. She says it should give good luck to my sunboxes.... I guess it must be Surya!

    He hangs in my bedroom window, just below the West Sunbox. I wonder if anyone has noticed yet.

    Mirrors for the PV panels

    14 Sept: Thinking about the idea of mirrors on the Sunboxes, I toyed with the idea of putting mirrors at the north end of the PV Array. It could be done with relative ease (apart from being so high on a ladder) using 1300x500 rectangles of very shiny aluminium sheet, riveted into the strong long edge extrusion of the PV panels.

      Here is a rendering of how it would look from the South, the sun azimuth at midday. It would increase the height of my installation above the 200mm that gets free Planning Permission - but I know that Rushcliffe are supportive of the solar experiments. 

    The harvest from our roof is very poor in Winter because of Sharphill and Wilford Hill behind the house. Our sunrise is a whole hour later than for people on flat ground, and the sunset correspondingly earlier. The idea is to provide a diffuse back glow when the Sun is at a very low angle in the winter. This view here is from the due south. It would not work if the mirrors were optically perfect, but aluminium is brightly scattering. 

    I am aware that the end panels could get more advantage. I asked EvoEnergy about this. They point out that as the panels are string as a direct current series, they have to work equally, so the panels working better at the end would have less effect than I hope. If one panel has a shadow on it, e.g. my TV Aerial at the south end casting a shadow after 1pm, the whole string can be affected.

    I suppose that if the mirror was the same height as the length of the panels, i.e. 9 metres, we might be talking... but I would have a very big planning application problem ! :)

    It is very unlikely I will do this, but I would still like to know Sharp's idea about it. EvoEnergy will send them the rendering for an opinion. The other issue is that of warranty - first it is an alteration by someone who is not an unauthorised installer. Secondly, although the side extrusion has no electrical effect and is strong enough to be drilled, perhaps there is a chance of wind damage in extreme wind)

    Let the Payback begin!

    14 Sept 2010: We talk a lot about Payback on Photovoltaic roofs, but does it ever come? Well I had a letter from Good Energy, and I have to send them my Generating Meter reading for 14th September - for the first payment. I have sent it off!
    That payment will come soon, I hope!

    January 2011 Postscript: We had the payment sometime in November for the April to September period (was over £ 1000 !), and we have been asked for a reading for the December PV harvest. I guess they will pay about about 3-monthly intervals.

    Monday, September 13, 2010

    Praying for Rain?

    12 Sept: Small things count and water saving is one of them! We never use tap water for anything in the garden - we have nice clean soft rainwater from 200 litres of storage off the roof and conservatory.
       My near-neighbour is elderly and feels guilty about using tap water to water the plants with after a spell of dry weather. She has only one rainwater pipe at the rear of the house, and there is no space for a water butt. Also if a water butt was built some way away with an extension pipe, it would be below the window and too low to reach easily for watering can filling.
      Therefore, I used some of my stock aluminium (it seems to accumulate, left over from previous things) and knocked up a custom make aluminium frame - it has to be very durable and very strong. The heavy 100 kilo weight of the tank is off centre, so the base must be resistant to racking - and capable of fitting between the concrete wall and the house wall. Having discovered the joys of pop-rivetting, it is now so easy to think something up, and hours later, it is made. Drill just one hole, instead of two different ones as with self tapped screwing. The result is a nice tight joint. If you have made a mistake, you can easily drill out the rivet. You can get ones of different lengths to suit - perfect! We bought a Water Butt from B and Q, and it now fits perfectly, with a handy concrete ledge so support the watering can while it is being filled!

    Riveting was easy..... Most of the labour was in cutting. Previously I have had all sizes pre-cut by the guys in stores, so to make a custom object is tiresome having only a plumber's hacksaw for cutting - quite unsuitable for thicker metal sections. Therefore I have also bought an Angle Grinder from Screwfix, that can easily cut thicker metal sections. Soon I shall feel about it how I now feel about the riveter and the portable drill - how did i ever manage without it?

    It is ironic that while I was erecting the water butt, cutting into the rainwater downpipe to fit the water catcher, I could hear my near neighbour's neighbour filling a paddling pool in the back garden from tap water - hundreds of litres!

    Wednesday, September 8, 2010

    Heat pumps, the solution but also the problem

    If I could be permitted to comment on the BBCs choice
    of picture, it would seem that the ground loop
    is far too shallow!
    8 Sept 2010: Report in the BBC Website - reporting on Heat Pumps, in the Science and Technology section from an Energy Saving Trust report. 47-50% of a house's energy demand is in Space Heating, 22% in Hot water.
      They say that Heat pumps are the way of the future, especially for people off the gas grid and looking to manage without oil, or to manage with electricity only.
      However, they also say that too many heat pump installations are done poorly, many installations are difficult to fit into existing houses, the companies in the UK are still fragmented into different operators (eg, most UK heat pump suppliers don't do the plumbing, electrics or the hole drilling, the customer has to find those); related technologies like underfloor heating are not always suitable; and existing Heat pump installation are not being sufficiently monitored for their efficacy and efficiency.
       It seems that in other countries, like Sweden, the industry is more holistic, so you the customer are not left flailing about trying to Google for hole drillers and plumbers with GSHP knowledge, like we were in 2006. In the UK, there are few people off the gas grid.

    See also, the New Energy Focus article on the same story.

    I ask: "What is the motivation for people to have heat pumps? is the only reason because they are off the gas grid, and they see the heat pump merely as a boiler replacement? Do they think that because the heat comes from the ground or air, they can actually waste more energy than before when they used oil? Or do they recognise that if they tune their lifestyle accordingly, they can use the heat pump for a genuine carbon saving? And if they think that, do they want to see their heat pump working more efficiently, and perhaps even capable of benefitting from an augmentation system like sunboxes?"

    I admit that when we first had ours installed, we thought "Great, we are getting free heat from the ground, four times as much as we burn, so can have plenty of hot water etc" As time went on, it became clear that the consumption was far more than anticipated, the ground chilled significantly during the winter, and over the first two years, the COP appeared to be an average of 2.65, not the hoped for 4. The COP in a stand-alone lab condition may well be 4, but the COP that matters to us is the performance in practical working application, in which there are many heat transfers and longish pipes, and there are system losses. In a house, heat loss from circulating pipes helps with incidental heating, but heat loss in a trench between your house and the garage (if you keep your heat pump there) is a total loss.
       I have heard of people putting Heat pumps (usually air source) into buildings too large for the capacity of heat pump, and not well enough insulated, and then doing no energy monitoring thereafter. And, as I found with mine, there are things you can and perhaps need to do to make it work more efficiently - lifestyle adaptations as well as technological fixes. Don't believe salesmen who mention COP above 3! And DO MONITOR the consumption!

    Aluminium Eyebrows on the way!

    7 Sept: I have ordered two large aluminium sheets from the Faculty Engineering stores, so my aluminium reflectors will happen!
       The angle will be 60º, so that in Midsummer Midday, they point their edges directly at the sun, and therefore there is no effect. That is what I want, the idea is to avoid overheating in high summer. Earlier and later than midday, the Sun is lower, there will be some reflection and some beneficial gain.
       The optimum angle for Equinox and Winter is between 64º and 54º, so I am hoping for a good earning of heat whenever sun shines in those seasons.
      They won't heat up the black collectors significantly as the sunlight is angled perpendicular to the black panels, but they will heat up the air inside, and air-heat is what triggers the thermostat to start pumping, and is responsible for a good proportion of our thermal capture.
      I am wondering about lining the bottom panel of the boxes with shiny aluminium too. I noticed that the bottom panel has quite a build up of dust, so perhaps the upward reflection from a bottom panel is too marginal to be worth getting. If I find that the upper shiny eyebrows produce a noticeable benefit, then I would chase further efficiency by adding the bottom panels.
      The reflectors are flat, not curved, so there is no risk of focusing and causing local extreme temperatures. 2mm alloy is very stiff and should not bend in the wind..... famous last words.

    Saturday, September 4, 2010

    Lifestyle 'load shifting'

    Did I really have to die for you to run
    your washing machine?
    4 Sept: I had an email from a reader of this blog asking if a PV roof prompts alterations in lifestyle. Well it does, in summer for sure. The purpose of our PV roof is to reduce the amount of fossil fuel burning in Ratcliffe-on-Soar (coal fired) power station. Our motive wasn't the Feed in Tariff, but it was our catalyst, our enabler to do an action that we had wanted to do for 3 years.
       If we use electricity at night, some poor little piece of coal, far away, grown from a fine forest tree 60 million years ago, is glowing red, and then finally fading to ash... all because of us. It has to be imported - so I prefer to grow my own. Perhaps this is akin to vegetarians not being able to bear the thought of animals being slaughtered for food.... :)
       So if we have to do something that uses electricity, we time our usage to meet the peak of the roof productivity - our peak is 1030-1100 because the roof is east facing. The heat pump is delayed by a time clock so that it cannot start until 0900, even in winter. If we have a clothes wash to do, we will delay the washing machine that till 1000. If the dishwasher needs running, this never goes at the same time (because it might exceed the output of the roof), so that might be timed for 1100. Then if there's a bit of ironing to do, that might occur at 1200. The washing machine or dishwasher also stimulate the heat pump into further action due to the use of Hot Water, but this is when the roof is producing. Always use A-rated appliances if you can.
      At some point, we might want a damn good cup of coffee, so the kettle is on for a minute (actually, when I replace the kettle it will be an 'Eco-kettle' - of course 'elevenses' coincides perfectly with the roof power peak.
      We still turn off standby items, and avoid leaving inessential items powered up - so more gets exported.

    What does this all mean? Well, as we are an electrically heated household, due to the heat pump, it means we are using more like 70-75% of what our roof produces, not the normally expected 50% - so our ratio of Saving to Sale is highly advantageous. In the Winter, we use every tiny watt it produces, and we continue to use every kilowatt in the spring Equinox. We are only exporting (big time) in the Summer and Autumn Equinox.
        In the first year, we have generated 3,300 kWh, and in the same time period reduced our annual electricity import by 2,500 kWh from the previous annual average. That suggests a 75% ratio of usage, but if we have got also some saving from tuning of the heat pump (Sunboxes and timeclocks), that figure might be more like 70%. Financially that means that in addition to £1,360 from the Feed in Tariff, estimated Savings are worth £325, and Sales are worth £24. That totals £1,700 a year.

    Friday, September 3, 2010

    The Solar Oven

    Box cooker
    3 Sept'10: I have dissertation students on my Master course, and most of them are from India and write on 'sustainability' issues. So recently I became aware of a solar thermal device that exists by the million in India and Africa - the Solar Oven. Humble, cheap, portable, cheap, but if you have enough Sunshine and patience, they can be very energy saving.

    Collapsible card and baking foil cooker
    I realise that there is a very close analogy between the Surya Sunboxes and the Solar oven, and it has given me ideas for improving their performance, in Winter and in Summer. If you can cook a full chicken in 4 hours using a solar oven homemade from waste materials, we should be able to use REFLECTION to increase the temperature in the Sunboxes. There are plenty of websites telling you how to make your own oven from cardboard boxes, a sheet of glass or plastic and reflective windshield protectors, or other reflective metal. No great cost is involved.
    If it is hot enough to safely cook food, it is hot enough to increase the air temperature inside my Sunboxes.


    Solar Oven ideas for Surya Sunboxes

    Where does this Solar Oven idea lead?
    I have established that the 'greenhouse effect' works, but can something be done to enhance this?

    I have access to bright aluminium sheeting from the engineering faculty stores, so it has set me thinking for ways to enhance the performance of my sunboxes - I propose to instal mirror/ reflector/ concentrators around the sunboxes to capture even more solar heat, as it is not possible to enlarge the boxes themselves.
    • I am reluctant to get scaffolding back again, but if the changes are modest, they could be done from a well set up builders' ladder.
    • I wish I had made the existing boxes more airtight. The upper polycarbonate panel is too perfect a fit, and would have been better with about 2cm of overhang all round. The lower louvre is surrounded by a 5mm air gap, and in my Mark2 design, I have an overhang on the upper panels, and on the lower, I have rebated the detail to remove this gap. I am thinking of buying more polycarbonate to replace the upper louvres, but it will be difficult to do from ladders.
    • But I could also modify the bottom louvre to be upwardly reflective aluminium, bouncing light to the solar collectors. Equally, I could make them black painted aluminium, so they got very hot, and increased the air temperature. What a pair of extremes I have to balance there! 
    • The back surface is presently Brick Wall, and that does reasonably work well to retain heat. But should one instead fit bright reflective sheets over it to reflect heat back, which would remain inside the box because the waveform is changed and it does not reflect through the front polycarbonate panels. Alternatively black painted sheets of metal fastened to the wall might build up much higher air temperature (this is how solar ovens work, the interior has to be blackened.) Being light in weight, this would be high performance when heat is available, and cool quickly in the dark - could be a good thing as it would reduce the amount of wasted pump time in the darkness. But the boxes fit so tightly to the black panels that there is not really enough wall visible for this to be worth doing. And the metal sheet would stop the brickwork warming up.

    There is a similar argument in the Solar Oven community. The theory is that if the Pot with the food is dark, and if the interior of the box is reflective, the heat bounces around until it is absorbed by the pot. It doesn't escape through the glass because the wavelength is changed by reflection.
    • For the polycarbonate top louvre of the sunboxes, I already built an elaborate hinging mechanism that had a summer, equinox and winter setting for air flushing to prevent over-heating, but I have found this all to be unnecessary - simply, SHUT is the best option. But I could adapt the same idea and have bright metal reflector hinging above the sunbox that has three angle settings - the midday sun angle varies from 14º (winter solstice) to 37º (equinox) to 60º (summer solstice), so the reflector could be adjusted at intervals to improve the performance. This would reflect sunlight vertically downward, thus not shining onto the flat surface of the black collectors, but it could considerably raise the air temperature in the boxes. If this did not confuse the thermal probe in the upper zone, it could be useful to have higher air temp.
        I would definitely like to try this on the NEXT one I do, but feel that without scaffolding, this would be too difficult to apply to the ones on my house. It would be nice if these had an effect like those winglets on the end of aeroplane wings - a small change, but one that produces real economies. In fact, the bottom louvre could be replaced with reflective aluminium. There is no case for vertical reflectors at the sides as sun is orbiting 15º an hour, and with a solar cooker, the people adjust the angle, but I have to put up with fixed angles.
       Actually... thinking about it.... if they are simply 90º bracketed to the existing tilting rooflets, that would do for averaging winter and summer angles - and with my riveting tool instead of screwing, it would be easy to fix from a Ladder! Bright Winglets of 300mm by 1800 long would add one full additional square metre to the theoretical area of the panels! So I will order some Aluminium sheeting next week!

    April '11 Postscript: Despite my comments above, I did add some vertical corner mirrors in December '10, to help with morning capture. It costs almost nothing to do and is worth trying, to overcome morning reflection off the front faces of the boxes. And I have been round the boxes with clear tape, making them more airtight at the junctions.

    Thursday, September 2, 2010

    Good Energy Case Study - published!

    2 Sept: DNC writes: wow! I am really happy that Good Energy (renewables-based electricity supplier) have written a case study about the PV roof on my house and the research on the Sunbox project.
    See the Greenenergyrepublic Page

    Anybody got a Ground Source Heatpump?

    2 Sept: Had a long discussion with David Atkins of Ice Energy about moving the Sunboxes to another level - for them to be included in heat pump installations, it would help to get MCS accreditation, and have a value engineered kit, with defined list of parts, instructions for plumbers, electrician etc.

    Does anybody reading this have a Ground Source Heat pump?
    that they are willing to consider trying a Surya Sunbox installation for? If it will save 20-30% of the annual electricity consumption that is quite a saving over a few years. We want a comparator system to balance with the prototype (Peveril Solar House), so I would provide a free system design, and Sunbox build, your cost would be for the engineering cost of the materials and component parts only, with instructions to your plumber on installing and setting up the thermostat. We would also provide additional advice on Tuning your heatpump.

    I am incredibly happy with the performance of mine, and the reduction in running cost is already visible - it isn't only about cost/payback, it is also less fossil fuel burning at some distant power station, less carbon emission. People who walk past the house are always complimentary about the elegant simplicity of the architectural addition.
    The actual saving is made slightly difficult to compute due to the strong performance of my PV roof, but I can see from the special meter on the GSHP that we are getting good reductions on consumption every month, something like 40% during the summer months - and we hope for 20% during the winter season.
    Enquire of

    Wednesday, September 1, 2010

    Bjorn Lomborg turns at last

    31 Aug: a few years ago, the Climate Change debate was countered by the energetic influence of Bjorn Lomborg, a Danish academic who gave cheer to all the deniers, such as Nigel Lawson. In more recent times I read that he now believed in Climate Change, but now felt that it was too late and too expensive to do anything about it (having no remorse it seems for his part in having things go beyond the tipping point).
      In today's Guardian, the front page story leads with his total U-Turn, in which he now agrees that its the most important thing to make a major international investment in - countering Climate Change.

    Converting GAS to Kilowatt hours

    Since the article on Metering, I have had some questions on how to compute GAS energy equivalents. Actually, the gas bills are usually quoted in both, but this is quarterly. If you read your meter daily, you want an easy way to convert daily. Using a spreadsheet, it can all be soooo easy.
       Your Gas meter is usually in Cubic Metres. Multiply by the Calorific value, which for the gas delivered to my area is 39.4979. Multiply by a Volume Correction  1.022640. To get Kilowatt hours, now divide by 3.6.
      What this all means simply, is that if you have cubic metres,  multiply by 11.02. One cubic metre equals 11.02 kilowatt hours. Simples!
     Actually it could be more complicated. If you have an old meter showing it in Hundreds of Cubic Feet, your simple calculation is to multiply by 31.3 to get Kwh.
      Incidentally, only 56% of the cost of gas is for the gas itself. 22% of your payment is towards storage and delivery, 8% towards operating overheads, 7% to VAT and tax, 2% is the renewable obligation (e.g. paying for the Feed in Tariff and other grants for renewables), and 5% is profit for the company.
      To someone like me who has lived without gas for 4 years, it seems insane on health and safety grounds that we pipe highly explosive inflammable gas into the majority of urban homes in the UK.

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