Google’s Bay View Campus facility outside San Francisco may be the largest thermal pile installation in the US. Thermal piles combine the use of geothermal heating and cooling with the deep foundation system to improve energy efficiency. An article in FastCompany indicates that the heat pumps utilizing the loops in the thermal piles will provide all of the heating and 95% of the cooling necessary for the building, cooling towers will be needed for the other 5% on the hottest days of the year. This will save approximately 8 million gallons of potable water every year.
Many geothermal heat pump projects use separate borehole fields to create the network of ground loops needed to extract and reject heat to the ground. The beauty of thermal piles is that the holes were already needed for the foundations, so the incremental cost is really just the additional tubing. This facility utilizes approximately 4,000 piles each 80 feet long. Only about 2,500 of those piles will be thermal piles because of spacing constraints. If the thermal piles are too close together, there is the potential to over-cool, or more likely, overheat the ground making the system less efficient.