Tuesday, November 30, 2010

Anneberg, an inspiring example

29 Nov '10: Sami (of Finland) just pointed me in the direction of Anneberg, a district near Stockholm which is an inspiring examples of interseasonal storage - better than I have yet seen (even more than Drake's Landing), and a huge vindication of what I have been doing here as a solitary adventurer, much maligned by some who don't believe it is possible. Chris Wood (who mentioned it to me a few weeks ago, but I didn't hunt down the details) points out that it has been going now for eight years.

This scheme uses interseasonal storage despite the much higher latitude - colder winters and lower sun angles in summer. There is a deeper technical discussion on this site, in english with some good diagrams:

  Quite remarkably, they are trying to do this without heatpumps, I guess trying to store enough energy to support their underfloor heating, and using electricity as a backup. The house designs are hugely dominated by the absolute imperative to face south and maximise the solar panel area.
  One of the most interesting diagrams I have seen is their attempt to guess at the losses underground and to provide enough solar thermal input to overcome this heat loss. This could be because their panel area is far larger per house than mine, and their expected ground temperature far hotter - the delta-T between their hot zone and the surrounding infinite ground will be far higher and encourage much faster leaking.
   As with mine, this cannot be measured, it can only be guessed at. My panels produce so little by comparison, that last summer, the maximum deep ground temperature reached was 14º, not significant enough for a large loss. I look forward to seeing next summer how high this goes, and will try to evolve a similar diagram with some estimate of loss. The earth should reach higher than that, as the mirrors will enhance the sunbox performance and the earth will be making a better standing start, assuming that the ground temp in March is higher than it was in 2010. Presently, it is more than 3 degrees better than in 2009.

  I have since learnt that Anneberg did not work well initially, mostly to do with technical problems from leakages, and the consequent reliance on direct electric heating. The decision to try to heat the ground to the temperature of a hot water tank so that there would be no need for heat pumps is bound to have problems, transmitting high temperature fluid a long way from each house to a distant store, and back again, and then doing the same with the fluid that is actually heating the house. It also accepts a far higher rate of loss to surrounding soil than I would be prepared to accept. 
   My sunbox system here is heating only the soil immediately below the house using existing pipe runs, and never higher than 25º even in summer. Re: using houses without heatpumps, I believe that it would be very difficult to market a house that had no heating system - its better to put something in that doesn't have to be used too often if the house performs well, but is there if it doesn't.
   However, I have also heard that the Anneberg system is working for some years now, since solving these teething problems. I have had enough problems too and it is all part of the evolution of a technology.

2 comments:

  1. David,

    I sent you a link a few weeks ago to a presentation by Prfo goran hellstrom of Lund University http://www.gshp.org.uk/documents/4LinkingGSHPwithsolarthermalanddistrictheating.pdf

    this includes the work at Anneberg and has now been running fine for nearly 8 years!

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  2. Yes, I should have chased it on that first occasion. His PPT shows the picture twice, the first time without a location caption, and the second time with the name of somewhere in Germany as the first location title and then Anneberg.
    It is impressive that they heat the ground so much that they try to manage without heat pump. But they use direct electric heating for the DHW, which is acceptable, I suppose if you harvested enough PV the previous summer, and if DHW use is light. An instant electric heater for a shower is likely to use less energy over a year than keeping a 160 litre tank at 51º for 24/7.
    Keeping the ground temperature up to a range of 35-45º seems to accept a high level of heat loss to the surroundings. In my case, the ground temp reached a max of 14 last summer, and I hope that in 2011, with the mirrors and starting from a warmer temp in March, it will get up to a higher temp. I didnt realise they had been going for as long as 8 years!

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