Friday, February 4, 2011

Discussion about System First

(Image from RB website)
4th Feb 2011: I was lucky enough to have a chance to talk to Dr Chris Wood today, who has just been awarded one of the Rushlight Awards, in the category of Ground Source Heat Pumps - against tough competition from some very good competitors. His particular research has been in 'energy foundations', a system of piling developed with Roger Bullivant that is another way for GSHP to get energy from the ground using the structure,  instead of a single deep borehole.
   Key to this is solar recharging of the ground under the building. It is based on the RB System First piling system, but it adds ground source loops into the piles. Typically, these would be 8 metres deep and with solar charging would form a bulb of heat under the building (reaching more deeply than some horizontal slinkies) benefitting from the high insulation of the slab. There might be 20 such piles under a typical house, quick to drill with RB's high speed rig, and causing the minimum of spoil compared with traditional trenches or trench fill - and using less concrete.
   I am designing some houses and flats at the moment for southern England, and am pretty determined to use this system, in tandem with Surya Sunboxes.

   Chris is also interested in the proposals for the skyscraper design in New York. One benefit of the RB energy foundations is that you have some comfort from the near infinite quantity of soil under the house. The natural energy content of the soil overrides the many variations such as the amount of heat gained or lost from the ground near the surface. If you wish to, you could add more solar panels.
   In the case of the skyscraper, with insulated thermal stores at high altitude, much more exact calculation is required:
- the matching of the area of solar panels incorporated into the facade
- the potential system losses from the delivery piping
- the volume and phase change temperature of the store
- the means of returning heat to the apartment
- allowance for heat loss from the store, or how to deal with overheating
All these have to be perfectly balanced, or there would have to be some direct electricity used to supplement the heating system which would undo the whole purpose of the scheme. The HQ building in Austria assumed it would take 7 yrs of solar heating to get the infinitely sized ground store up to steady state (in which heat gain equals heat loss and withdrawal). In the case of the skyscraper, with heavily insulated stores of finite size, there has to be a means of bringing the store up to temperature, depending on what time of year the building is commissioned and occupied. Because the stores are insulated, they would get to steady state within one full year. Perhaps there should be ancillary stores. Also, the temperature of the ancillary stores can be boosted with non-solar heat by using them to cool public spaces and other parts of the building in summer.
We hope that Chris will be available in March (after EcoBuild) to help us take this further.

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