Application of a New Wireless Instrument to Characterize Thermal Properties of Ground Coupled Heat Exchangers

In this work, we report the design and laboratory test of a new instrument to measure the temperature of the heat transfer fluid along the borehole exchanger (BHE) by autonomous wireless sensor. The instrument consists of a device, which inserts and extracts miniaturized wireless sensors in the borehole with a mechanical subsystem, composed by a circulating pump and two valves. This device transmits to the sensors the acquisition configuration, and downloads the temperature data measured by the sensor along its way through the borehole heat exchanger. Each sensor is included in a sphere of 25 mm diameter and contains a transceiver, a microcontroller, a temperature sensor and a power supply. This instrument allows the collection of information about the thermal characteristics of geological structure of soil and its influence in borehole thermal behaviour, in dynamic regime, and facilitates the implementation of thermal response test (TRT) more easy and reliable.