What did we consider?
Prior to commencing any feasibility assessment we perform a due diligence check on the heating requirement figures that we receive. Our initial analysis revealed that for a building of this type and construction, a much larger heating and lower cooling requirement was required. We presented our findings to EDF’s M&E supplier and after reappraising their figures, they identified a peak heating load of 450kW and a peak cooling load of 350kW.
Our next challenge concerned the proposed drilling area. Our initial assessment was that the patch of land in front of the car park was simply not large enough to accommodate the size of groundloop that would be required for this heating/cooling requirement, without thermal bridging occurring and the performance of the system being compromised.
We understood that there was a reluctance to allow drilling in the car park area of the site, due to concerns about costs of reinstatement of the tarmac. We explained the drilling process and that the car park tarmac would not require to be re-laid as a result of our activities and obtained permission to consider the potential of using the whole car park area in the borehole array designs.
Finally we looked at the geology for the site. It was noted that the site was located within close proximity of a major fault line (the Crawley Fault). It is important to understand the nature of geological faults, and the uncertainties which attend their mapped position at the surface. Faults are planes of movement (not necessarily vertical) along which adjacent blocks of rock strata have moved relative to each other.
They commonly consist of zones, perhaps up to several tens of metres wide, containing several to many fractures. The portrayal of such faults as a single line on the geological map is therefore a generalisation. In addition to this, the geological observations on which the placement of this particular fault had been based were ambiguous and could be interpreted differently in the context of this location. Depending on which side of the fault a borehole was drilled, the geological sequence encountered may have differed considerably, as shown in the diagram opposite.
The presence of the fault would have posed some complications to the final ground-loop length and borehole array layout, with a number of test boreholes being required to ascertain ground conditions for a final design.