The Hellenic Survey of Geology and Mineral Exploration (H.S.G.M.E.), within the framework of (a) its institutional responsibility for monitoring the country’s geothermal fields through the installation of recording stations, and (b) the implementation of the subprojects “Management Plans for Low-Temperature Geothermal Fields” (DIA.GEOTH.) and “Actions for the Rational and Sustainable Utilization of Geothermal Energy – GEOTHERM,” proceeded with the installation of four (4) new telemetric stations at the low-temperature geothermal field of Nea Apollonia, Thessaloniki, during the period of July 5–8, 2022, as part of the application of a Model Management Plan.
The installation of the new geothermal telemetric stations was carried out by a team from the Department of Geothermal and Thermal Mineral Resources (GEOTHE) of H.S.G.M.E., consisting of: (a) Dr. Apostolos Arvanitis, Geologist–Geothermal Specialist, Head of GEOTHE, (b) Markos Xenakis, Geologist, (c) Polyánthi Trimi, MSc Mining–Metallurgical Engineer, and (d) Christos Mylonas, Electronics Technician.
Each monitoring, recording, and telemetric data transmission station consists of: (a) sensors for the automatic recording of temperature and pressure, installed inside the boreholes (where no pumping system is present) with suitable modifications to the screwed cap (drilling of openings, placement of cable glands); (b) a monitoring and data transmission unit, which includes a data logger for recording the measured values, a battery, and a modem connected to the mobile network; and (c) connection cables linking the sensors with the data collection and transmission unit.
The new stations provide continuous, real-time monitoring, recording, and telemetric transmission of temperature and pressure (water level) parameters of the geothermal reservoir in the Nea Apollonia field. The sensors were placed at appropriate depths in selected boreholes to record variations in these parameters.
More specifically:
(a) Station APL-G1 was installed in borehole G1, with a depth of 14 m, located within the spa complex. Both the temperature and pressure sensors were placed at a depth of 13 m (the water level was at 0.82 m).
(b) Station APL-GV1P was installed in the old large-diameter research borehole GV-1P (depth 320 m), constructed by I.G.M.E. in 2003. The temperature sensor was placed at a depth of 301 m, and the pressure sensor at 65 m (the water level was at 52.80 m).
(c) Station APL-GV5P was installed in the old large-diameter research borehole GV-5P (depth 126 m), constructed by I.G.M.E. in 2004. The temperature sensor was placed at 70 m, where the maximum temperature is recorded, and the pressure sensor at 55 m (the water level was at 19.83 m).
(d) Station APL-K1 was installed in an abandoned private production borehole, approximately 56–60 m deep. The temperature sensor was placed at 56.1 m, and the pressure sensor at 22.36 m (the borehole had artesian flow).
In all the above telemetric stations, power supply is ensured through the use of solar (photovoltaic) panels, which charge each station’s battery via a charge controller.