Monday, September 7, 2009

Winter and Summer charging ideas


7 Sept 2009: Talking to my architect friend in Cardiff, Alan Gillard, he described how he has used reverse cycle heatpump in a scheme in Wales, that is in effect, charging the earth. Using the reverse cycle, the underfloor heating can be underfloor cooling, so that excess summer heat from the buildings is dumped into the borehole... where it is retrievable in the evening, or in the colder seasons. He knows of schemes in Europe that use reverse cycle this way.
   The last two UK summers have not been hot enough for this to be activated, but its a great idea for hotter climates, instead of air conditioning.

He also discussed the idea of the solar thermal water tank being also a buffer for ground charging in my previous blog article. He suggested that it could be made even more efficient if the tank was charged with surplus heat from a winter / night-time source such as the backboiler pipes in a woodburning stove. So that all year round and in the evenings the tank could be getting heat from somewhere  - (summer=solar, winter=woodburning stove) and that whenever the temperature rises above a target temp like 30 or 35, the remaining heat is sunk into the ground loop to charge the earth - this stops the tank ever from overheating.

1 comment:

  1. Yes - the use of reversible heat pumps is widespread in Europe, particularly in office blocks. In terms of underfloor heating in a residential setting, the use of a concrete floor provides great benefits through its thermal mass. When the outside air temperature is such that no heating is required, then it may be the case that the room starts to get too warm. However, the floor slab can be held at a moderate temperature by passive cooling with the underfloor heating system. The high thermal mass of the floor in most cases ensures that high peak temperatures are not reached - hence active (active:when the heat pump compressor is running) cooling is not needed in most cases. Passive cooling works by circulating both the underfloor heating circuit and the ground loop circuit - they then exchange heat in a heat exchanger. If the room air temperature is say 25deg C and the deep ground is say 12deg C then ultimately the slab is cooled and the humans in the room feel the benefit! Effectively this is also recharging the ground but passively (not entirely passive as the circulation pumps must run but some PV will offset this!)

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