Portugal is at the forefront of this technology’s research, being this an HVAC system using Geothermal heat pumps, thus consuming much less energy than conventional air conditioning equipment, with investments repayable in about 5 years

It’s a system that’s already widely used in Nordic countries, and there is and ongoing feasibility study in 8 European cities in southern Europe, including Portugal, namely Coimbra.

The experience is part of the European project GroundMed that, in collaboration with a team of researchers at the Institute for Systems and Robotics at the University of Coimbra, assessed the impact of this technology in regions along the Mediterranean.

Therefore, in the winter the objective goes through getting heat from the ground (which is at a temperature of 16 ºC), in the summer, it is the opposite takes place, which is to find cold  in the underground, since the soil keeps the same 16 ºC temperature.

On the pilot installation in Coimbra, various studies already carried out, show that the geothermal pump reduces electricity consumption by more than 50% compared to traditional alternatives: “On the ordinary oil heatings, a unit of electricity generates a unit of heat. With this technology, with one unit of electricity we generate six of heat”.

The studies carried out on the pilot installation of the Administração da Região Hidrográfica do Centro building, showed that in the summer, the air conditioning equipment installed, consumed on average, 62 kWh per day. With the geothermal pump technology, consumption has reduced to about 28 kWh per day.

“Geothermal heat pumps do not depend on the outdoor temperature (this in traditional heat pumps), but on the subsurface temperature (7 holes at 150 meters deep in the case of the pilot installation in Coimbra),” remain very stable throughout the year, being “possible to ensure the same comfort, using less electricity, and reducing the bill and CO2 emissions”.

The next stage of the project, funded in 4.3 million euros, goes through incorporating a cylindrical tank coated with Phase-Change Material (PCM), encapsulated, to store thermal energy – heat in the case of installation in Coimbra and cold at the facility on Septèmes-les-Vallons, in France.

Cientists believe that the implementation of the bombs in large buildings such as hospitals, where there is a high energy output, will bring great advantages.

In a simplified manner we can say that, for the integration of this system in buildings’ air conditioning it’s necessary to take into account that the thermal production values must be as close as possible to the desired temperature for indoor air, so the exchange surfaces should be large, then the options in choice of terminal units point to the use of radiant surfaces and fan coil units, or air handling units for the capture of geothermal energy can be used, whether coils are arranged horizontally or vertically, buried or in contact with large bodies of water or even resorting to aquifers. In the case of buried coils and laid out horizontally, those are more subjected to the fluctuations of the temperature of the outside air, so they’re used in low power applications. The vertical coils are made with holes ranging up to 150 meters of separation from each other and therefore are not subject to variations of the temperature of the outside air.

Types of caption:

As a way of advancing knowledge in Portugal in the field of geothermics, heat pumps and promote their proper dissemination and use, the Portuguese Platform of Superficial Geothermal Energy (PPGS) was created by four national entities: the General Administration for Energy and Geology (DGEG), the National Laboratory for Energy and Geology (LNEG), the Portuguese Association of Geologists (APG) and the Agency for Energy (ADENE).