Tuesday, January 10, 2012

Varisol Tubes

16 horizontal tubes make better use of that space, and keep the
plumbing compact too!
10 Jan 2012: Looking at options for evacuated tubes (ETs), I discovered Varisol tubes (by Kingspan) as recommended to me by Gerry Kennedy of MG Renewables. From this page you can download an installation manual.
   These ETs are very happy being laid horizontal (with a 2ยบ tilt) and are modularly connected, i.e. do not require a large boxy manifold, as each one has its own manifold component and they all connect together.
  Although I like the simplicity of the older type where you can just lift a tube out of the boxy manifold, these Varisols are extremely neat and close fitting, and get maximum capture from a square metre of tubes - which cluster closely, leaving no wasted space between.
showing how the tubes connect, with no
wasted space between.
   16 tubes, of a length 1950mm would give about 2.2 sqm of area.  They would occupy that 3m x 1.3m space with a bit of spare working space around.   Although these tubes would be facing East, I do not see an alternative. The South wall is busy enough already, and has the added risk of kids throwing a speculative stone from the field. The west roof is clear, but it faces 10 degrees north of west.
  I looked at my plumbing in the loft and found that I have already (how very kind and thoughtful of me!), provided dummy connections for future attachment of a second source of heat, either a tank or a solar panel, should it ever be thought of. It is downstream of the existing energy meter, so will not confuse my measurements of the amount produced by the Sunbox. The tube array can have its own energy meter, thermostat and pump.
  I am currently in correspondence with Kingspan Renewables, regarding these tubes.
In the foreground, there is a blue handled valve and
either side of that, a 22mm Feed and Return pipe.

  Logic: My main worry is that the three port Danfoss valve on the ground floor has to be commanded by one thermostat or the other. Logically, it seems to me that it should be the Sunbox thermostat that does that. On the good sunny days, I don't want it to be Either-Or, I want it to be Both sending heat into the borehole. If the SB has enough sun to kick off, then there will also be heat from the ETs. The SB works from air heat, e.g., at 0100 at night on summer nights, and in that time, we would not want to be sending liquid through the ETs. There might be cloudy bright days when the ETs have heat, but the SB does not. The risk is then heat wastage if ET heat is sent around the SB and is cooled. There are delta-T conditions when the SB is working, but there would be no ET action because the thermostat on the ETs would not command it. .... doh! It will all make sense as I think about it more. I have invited Gerry to call round for a discussion.
  At some future date, I have the option to fit a solar water tank up there, as the Kingspan tanks are 480mm wide including insulation and would fit easily through the loft hatch. Why not use a water tank now? well as explained earlier, the principle of delivering heat directly to the boreholes can been so very successfully proved that there is only a marginal benefit and a very high cost by adding a mains supply up to the loft and a large insulated tank. 

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