The new methodology promoted by the researchers of the School of Engineering (ETSE) of the Universitat de València and the Universitat Politècnica de València will be useful to know the thermal conductivity of the subsoil geological layers, and to localise the most efficient ones in the heat release or absorption. The design of heat pump exchangers could be much more efficient, since this technique can save up to 70% of the consumed energy in comparison to conventional pumps.

It was carried out from standard experimental tests (TRT), increased with the temperature measurement at different depths, carried out for a simple procedure and in known locations. Until now, the standard measuring methods of the capacity of extracting or injecting heat to the subsoil only permitted the obtaining of an average value of the surroundings where the heat transference took place. However, the most efficient zones could not be identified.

Why is it important to study the subsoil geological layers one by one? 

According to Nordin Aranzabal, researcher of the Department of Electronic Engineering of the Universitat de València ‘this detailed knowledge is very important in the design of geothermal heat exchangers, since the use of these data in the design can achieve the reduction of installation costs in order to make the most of the zones with the most exchange capacity, the reduction of the  period for the return on investment and the maximisation of economical and energetic savings’.

 ‘Around 40% of the consumed energy in buildings is dedicated to conditioning’, says Aranzabal. For this reason it is a great advance the fact that geothermal heat exchangers, used together with heat pumps for conditioning, show savings of 70% of the electric energy in comparison to conventional heat pumps.

 The advantages of this do not end here. Researchers of the ETSE quote, also, the reduction of the impact on buildings- since they do not need heat exchangers with air nor cooling towers- the reduction of risks for our health due to legionella, as well as the reduction of carbon footprint.

This type of installations are very important for a sustainable usage of energy because, thanks to the presented efficiency, they receive the consideration of renewable energy. It is already used in cooler countries of Europe and America due to their weather conditions. Thanks to this type of works, its usage is being extended to regions with warmer climates. The construction of the exchanger, however, is restricted in less rigorous climate areas such as the Mediterranean, where other technologies can be cheaper.

The confirmation of the lack of detailed data about the heat exchange process of the buried tubes in the subsoil and the impossibility us using layers with a high humidity and water flux content, is the factor that lead the researcher to the development of tools for the obtaining of additional measures to characterise better the heat exchanges in the drilling.

From the implementation of these measure procedures on an experimental geothermal exchanger we will obtain the data, temperature profiles in an auxiliary observer tube, that allowed to adjust the thermal characteristics of the subsoil in a simulation model reproducing the behaviour of the installation.

Simulations used a three-dimensional model of the exchanger that, with the finite elements technique, reproduced the behaviour of the measured data during the Thermal Answer Test (TRT), and adjusted, for this reason, the capacity of heat exchange with the depth of the surrounding area.

Design of Digital Systems and Communications Group (DSDC)

The Design of Digital Systems and Communications Group (DSDC) of the Universitat de València is specialised in the design and development of electronic systems, from the definition of specifications to the pre-commercial prototype. Created in 1996, it displayed initially electronic systems of high performances for the generation and processing of data from the great detectors of the European Organisation for Nuclear Research (CERN) of Geneva.

Nowadays, its capacities are developed in nuclear, automation and digital medicine, energy efficiency, ambient intelligence and radiation detectors. It works with integrated digital systems, wireless communication technologies, high-speed digital design or digital electronic developments based on microcontrollers. The DSDC is composed of four full-time professors and four doctoral students. The facilities of the ETSE group include two laboratories.

Seven members participated in this research, recently published in Applied Thermal Engineering. Five of them researchers of the Universitat de València of the Department of Electronic Engineering, and two researchers of the Universitat Politècnica de València. The full article is available here.