Sunday, June 26, 2011

Idea for sloping front panel

26 June 2011: Comparing the Winter, Equinox and Summer performance, I can see that the vertical orientation of the boxes becomes a subject for discussion.
  My earlier motivations were six-fold:
  • You get automatic Planning Permission if you keep renewable technology devices down to equal or less than 200mm projection. As a wall-based system is highly visible, this would be a consideration in other installations in the future.
  • I only had a south facing wall, I don't have a south facing roof, so the wall was the only place.
  • Construction and maintenance are easier to a panel that is wall mounted as I can get access to every part of it from a scaffold or ladder.
  • I can improvise as I go along (while building it) making design decisions as they become needed, while the scaffolding was up.
  • They look neat and architecturally minimal, being compact rectangular structures, like rather unusual windows.
  • I thought that temperatures would get dangerously high in summer, and the vertical orientation would protect them from overheating.
Now that they have had a year and a quarter of operation, I have seen them working through two summers. They never overheat, and if there is good heat, then it is dumped underground. The top and bottom mirrors give the existing boxes a distinctive appearance, and they increase the capture of sunshine at low sun angles by increasing the apparent surface area. However, if the entire front face can be tilted like these illustrated, the angle incident to the sun is far more effective, and mirrors would not be needed. A 60º angle face will be better for Equinox and Summer sun angles. Also, when the sun does shine and the air temperature builds up, the volume of air in the boxes is greater, so that the chilling effect of the black panels is reduced. The volume of air is presently 1.2 m3 and it would be 2.48 m3 if enlarged in this way.
  This idea illustrated would project more than 200mm, but hey! this is research and we are trying to discover the best form - Rushcliffe BC have given me planning permission to project more than 200mm, so let's consider it further. 
  The slope can be accomplished with the existing (and expensive) sunbox fronts simply taken off and refitted with new structural polycarbonate side panels. The sloping underpanel will be insulated, to reduce heat loss downwards in winter, and the upper surface of the underpanel will be brightly reflective to add more heat to the black panels in summer. There will still be a polycarbonate soffit next to the wall (re-using the existing). The top rail can be of aluminium, and can probably support the existing top mirrors, repositioned at their present angle of 60º to enhance winter performance.
  I would like to make one long super box to enclose all four of the black panels but that would require me to waste the existing fronts, and to have too many modifications to the aluminium fixing rails. I am thinking about it though, because the existing fronts might be big enough to be cut into the structural side panels. They are of PalSun polycarbonate which is sun filtering and if I can get completely clear polycarbonate, then I might get a completely new long front panel, in 6mm or 4mm polycarbonate... and might consider two skinned PC, if that admits heat, but doesn't let it leave.

June reports

26 June 2011: Cool rainy week, ending with the hottest day of the year, with the evening air temperatures still well above 20º. Well after midnight, the sunboxes are still delivering heat into the ground! The Brickwork got nice and warm during the day, and released its heat slowly. The deep ground was warmed all day and at my midnight test, it was well over thirteen - 13.8ºC! The house and the GSHP consumption is yet again an all time low for the annual figure - but it won't be next week because a year ago we were on holiday and the GSHP used nothing for 2 weeks.
     At this time of year, the kilowatt rate is reduced because there's no Heat pump boosting the flow and increasing the delta-T. It's a long patient task of pumping liquid round at 5 litres/min, gradually burying that heat. In winter, the average capture is nearly 2 kilowatts, in summer it is more like 1 kilowatt. In Winter, the GSHP actually uses heat captured from the panels in real time, in summer, they settle into a comfortable routine of circulating the glycol at 15 or 17º.

19 June 2011: I am almost too knackered after doing the Great Notts Bike Ride to do anything.... but what the heck, if I can cycle over 70 miles in the day, I can perhaps find the energy to read the meters.... and yet again (bearing in mind that last June '10 was a hot month), the house meter and the GSHP again record all-time-Low record figures. Its getting tight, we are now getting to the 'incompressible', but the house is 5,301, and the GSHP is levelling off at 3,335 kWh per annum, measured this week. I'd like the ground temperature to be consistently above 13.0 now, but it is not, it is sticking at 12.9ºC. The vertical angle of the sunbox front faces means that at this time of solstice, the reflection off the glass at midday is more than the heat getting in. The top mirrors do nothing at this time, the bottom ones are perhaps helping a bit. The outer corner mirrors seem to do nothing, they were a mistake - should have been back against the wall (like the vertical centre mirrors), or not at all.
   The sunbox thermal capture is not an all time record.... I need to get up there and make them more airtight if that is possible. Any significant change to the boxes, eg changing the front panel from 6mm to 4mm plastic would require scaffolding.

12 June 2011: The spring-summer of good sunshine continues (although the week ended with a day of rain). Yet again, the House and GSHP meter weekly summaries were annual records, by modest margins. At this time of year, a whole week of house figures are equivalent to a bad day in the winter, and 2 weeks of GSHP figures are equivalent to a bad winter's day. Ground temperature was down slightly to 12.8ºC, we have had the heating on a bit due to heavy rain on Sunday.

5 June 2011: The House and GSHP meter weekly summaries were again annual records, but by so little that it is not significant. At this time of year, daily amounts are so small that even a day of north wind, or a bit of rain can shift it either way... we are in summer stasis. The real test will  be in the autumn when daily heat pump consumption metering resumes.

Ground Temperature: The deep ground temperature has reached 13.0ºC much earlier than last year - perhaps 12.9, perhaps 13.9. We have three ways of measuring and they vary from 13.3 to 12.8, so I take the middle or smaller. This is already above the base temperature that we would expect the ground to be after an entire summer of recuperation, normally. So, if we keep storing heat all through June and July, lets hope it will get higher. During a relatively cool June, the temps stayed mostly below 13, but finishing the month on a good high of over 13. 

Removed Corner Mirrors

25 June 2011: When the head and foot mirrors were added, there was an immediately palpable benefit. It coincided with the start of the heating season, so that may have been a helpful coincidence. We shall know better when we get to next September (the Equinox) and compare with the previous year's figures. They did pretty well in March and April.
    However, I have become increasingly convinced that the vertical corner mirrors have not been helping. They are on the wrong place, they should be at the rear of the boxes, not at the outer corners.
   I had hoped that the east corner mirror would give a helpful kickstart in the mornings - wishful thinking, mirrors are too small to make a difference.
   I had hoped that the west corner mirror would prolong the productivity of the box in the afternoon.... hmmm. This is more influenced by how warm the brickwork has got during the day, and also, the tree causes shadow when closer to sunset.
   So the sunboxes are back to looking how they were last October (2010) (except that in summer, the foot mirrors are tilted back to meet the higher summer sun angles)

Saturday, June 25, 2011

Condensation on the black panels

25 June 2011: I notice that the first black panel to receive cold glycol has streams of condensation running down the face after the panels have been working. It's not running down the face of the second panel, presumably because it's warmer than the first panel. The input of cold glycol is from a tee at the centre point between the sunboxes, as in this diagram [__]+[__]
   It is definitely not a leak of glycol because the reservoir bottle is at normal levels. the droplets are evenly distributed.
  Oh, and there's me at the top of the ladder taking the photograph.

Modifications to Sunboxes - Tape

25 June 2011: Chris Wood and I often debate the benefits of sunboxes and mirrors, and he is not as convinced as I am. His own use of the black polypropylene panels on his rig is to have them unglazed. If the ambient summer air temperature is above 21 degs and have a direct line of view to the sun, it is worth doing that. But I wanted something that would work in winter and equinox, and would not force the GSHP to work at very low temperatures.
  At this time of year there is a slight advantage to leaving the louvres open and letting air through them. The temperatures inside are not building up as high as they were in March/April, which is due I guess to the better Sun angle - I was seeing some daytime temperatures of over 40ºC in there, and now, on a good day, I am only seeing 30ºC. At the summer solstice, the declination of the sun at this latitude is 60º, very steep, with light bouncing off the face. On a sunny winter day, it is 14º, hitting the front face of the sunboxes almost directly.
  On the whole, averaged over a year, the boxes seem to do better if they are more airtight. So, I have applied duct tape along the bottom louvres to make them airtight along that face. I also added tape to the rooflets where there is an air gap. I will watch the daily temperatures and decide if that was right or wrong. It's easy to slit the tape if that was wrong.
   The risk here is that the black slabs act as chillers and without a source of fresh air, they cool the space more quickly than it can warm up from sky and sunlight. I see this happening, actually, with the air temperature falling once the slabs are working well.
  Notice that here, the foot mirrors are at reverse camber, pointing towards the panel faces, to catch the midday sun, when we have some!

Saturday, June 18, 2011

Solar Day 18 June

18 June.... well in the Northern Hemisphere anyway. See the page to read more about the mission of Solar Day. (it is 18 November in the Southern Hemisphere). DNC writes:

Face it....
• we have perhaps 50 yrs of declining oil and gas....
• if it wasnt for the smoky emission and the destruction of open cast mining we also have a lot of coal remaining below - enough for perhaps a couple of hundred years...
• but shouldn't we consider that the life of the Sun is measured in billions of years? Enough sunshine lands on the earth every day to cover our entire needs many times over if only we can develop the technology to capture and distribute it.

All energy sources cost something to exploit, I would prefer to see the money spent on a field full of Solar panels than a field converted into an open cast coal mine. (yes, people of Castle Donington!)
   Coming back to our own houses, what can we do? The upfront cost of a 4 kW PV array is only a fraction of the value of the house it goes onto, but will give a lifetime of cheap energy without emitting carbon, and an income for the first 25 years at least, more than enough to pay off the first cost.
   If the German government can project that the growth of renewable energy may be enough to decommission their nuclear power stations in 20 years, then that's an encouragement to us to try harder!

Tuesday, June 14, 2011

Fish farm in W Bridgford!

13 June 2011: One of DNC's students in the Tall Building design module at Nottingham University  has been doing a project on Vertical Farming. For his project he has developed a miniature 
ecosystem that can be repeated on a grand scale in his building. 

  Now that the University term is over, we have brought this system back and have parked it with Mark and Karina Wells, who live in West Bridgford, and who seem keen to have a working model of an aquaponic ecosystem in their conservatory.
  Currently there are 4 goldfish in the tank which is the right number for that size of tank and for that amount of hydroponic pebbles in a planting tray.
   The principles are explained in several websites, eg WikiHow . and in Backyard Aquaponics. In his building (designed for Singapore), fishfarms would alternate vertically with hydroponic vegetable farming (see here), through about 45 stories.
    Fish inhabit the water, and produce a certain amount of poo. Some of the water is trickled (with its rich nutrient from the fish) and feeds plants and fresh vegetables above or below in a base of volcanic pebbles. The water is thus purified and trickles on through to the next fish farm below. Algae is trapped in filters can can also be used productively.
    PV panels provide enough electrical power for the small amount of pumping required (a one minute trickle of water a few times a day, and some aeration of the water) . The only external input is fishfood - which could be obtained from organic sources, or processed from food waste from supermarkets and the vast restaurant industry of Singapore.
  This method can produce a way of producing edible fish and edible vegetables in one ecosystem! There are other by-products if it's done on a large scale, such as algae farming. Rainwater harvesting in a rainy place like Singapore means that it never requires imported fresh water. Land in Singapore is very limited and very expensive, so everything that gets built now has to be considered vertically! An eco-designed fish farm in West Bridgford would not need to be 45 stories! :)
  As the Singapore building would be productive enough on a small footprint, the remainder of the building is high quality residential apartments, enough to finance the initial construction cost of the tower.

Voltage Regulator replaced

13 June 2011: For some time now, the voltage optimiser above our consumer unit has not been displaying a light and has not been doing any optimising.
    Fortunately, it seems to have been designed so that when it ceases to work, the voltage reverts to normal, it doesn't do anything more alarming than just switch off the little green light.
   I hadn't noticed that it wasnt working, for a long time I just assumed it was until I showed it to a visitor to the house, and tried to measure the voltage with a meter - to find that the voltage was 250V everywhere!
  Ian from Midland Communications called in today and replaced the unit. I shall keep more of an eye on in future!

Thursday, June 2, 2011

Solar comparison mid 2010- mid 2011

Diagram from
2 June 2011 : Our PV roof has burst through the 5,000 kWh mark (since installation) and it is time to reflect. Looking at the monthly PV graphs for the last 12 months, one can match the curve against the weather trends. Our PV roof seems to be doing quite well at the moment.
  May 2011 was nearly as good as June of 2010, and April 2011 was nearly as good as July 2010. It would have been better if we had some snap thunderstorm to wash the panels, but they got dusty in a month long period with zero rain.
   December 2010 has a surprising amount of sunshine for such a cold month, but our roof had snow on it for some of the month, and the Sharp Hill nearby makes our sunrise an hour later than it should be elsewhere. As our PV roof faces east (morning), this causes a dip in the figures. December is so low that the entire month is equal to two good days in June. We get used to it, so if you look at the meter in December and found you made 3.6 kWh in a single day that is an occasion for jumping up and down! The worst day in Dec 2010 was Zero kWh - less than 100 watt-hours in a day is too small an amount to meter!
    As we move from Feb to Mar, the sun no longer rises from behind the hill, and the monthly figures zoom upwards. This is amplified by the fact that February with 28 days is 10% shorter than a typical month.
    The equinox is at the 2/3 point of the month, not halfway, so September 2010 was slightly better than March 2011.
    I now wait to see what June will bring. First two days, sunny so far! The first week of June 2010 was also very hot, so for the first time in months, I won't be seeing record annual figures... the annual summaries are now stabilising. All the figures have been helped by having had the coldest winter in 150 years followed by the warmest spring in 150 years. If we have a very warm autumn coming up to New year 2012, we will see exceptional annual figures.

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