Between 30.01-01.02.2019 in Paris, the GABI COST (Geothermal Energy Applications in Buildings and Infrastructures) program has concluded the four-year co-operation of leading academics and not only in the field of geothermal structures.
In the presentation of the final report for each country, the cooperation between academia and industry in Romania represented by University Cluj and Termoline has been particularly appreciated through the implementation of the research results of Oromolu Bucharest (the geothermal diaphragm walls in Piata Victoriei) and County Hospital – Emergency Unit Oradea (320 energy piles) along with other works of a smaller scale.
The European Cooperation in Science and Technology (COST) provides funding for the creation of research networks, called COST Actions. These networks offer an open space for collaboration among scientists across Europe (and beyond) and thereby give impetus to research advancements and innovation. COST provides networking opportunities for researchers and innovators in order to strengthen Europe’s capacity to address scientific, technological and societal challenges.
By providing an alternative to fossil fuels and reducing peak demand from the grid, they also provide an attractive tool towards energy independence and distributed generation with no adverse impact on the environment. However, the widespread application of this sustainable technology is currently hindered by the large heterogeneity in the development and regulatory framework in European countries.
By sharing knowledge and experiences, the use of thermoactive geostructures will increase, especially in countries with less experience. This newly created network will ensure an inclusive and open platform for scientific discussion to define European best practice rules for geothermal applications, promote public awareness and confidence in this technique, and foster advancement in knowledge through collaboration.
The program Horizon 2020 GABI (Geothermal Energy Applications in Buildings and Infrastructures) has proposed that in four years to provide an open platform for scientific discussion to define European standards on design best practices for geothermal applications, to promote awareness and public confidence in this technique and to develop the European network of geothermal applications for buildings and infrastructures. The thermoactive geostructures have the additional advantage of being based on local resources (land) and therefore do not require additional investment in infrastructure. Offering an alternative to fossil fuels, they provide an attractive tool for energy independence and no negative impact on the environment. However, the widespread application of this sustainable technology is currently hampered by the lack of “know-how” and regulations in European countries. The increased need for renewable energy sources has led to expansion of shallow geothermal applications for heating and/or cooling of buildings. The integration of heat exchangers in those elements of the structure that interface with the ground, such as foundations, tunnels and diaphragm walls, is particularly attractive because of the inherent cost saving involved in combining a required structural component with the harvesting of geothermal energy. Thermoactive geostructures present the additional benefit of relying on localized resources (the ground) and therefore do not need additional infrastructural investments. If a building is designed in structurally piles or walls diaphragm they are mounted manifold pipe HDPE or PE-Xa with low cost, these collectors become the primary source of heat for heat pumps ground-water provide heating – air conditioning of the building. Very important: Soil around the geothermal structures so built becomes an “energy accumulator” – during the winter, the low temperature will be lowered in the soil, which will be used in the next summer for air conditioning, including passive air conditioning, practically storing energy between seasons.
GEOTHERMAL STRUCTURES STUDIED:
I. GEOTHERMAL PROBES – are the most used geothermal systems – the primary source of brine to water heat pumps. The drill depths is usually 50-200 m and geothermal probes (PEHA or PE-Xa pipe diameter 32-40 mm) are inserted into the drilling. Geothermal probes provide thermal transfer with closed loop soil through which ethylene glycol circulates with a freezing temperature of -15 ° C.
II. PILOTI ENERGETICI – piles designed with a structural role for a building become energetic piles if it is mount inside PEHA pipe or PE-Xa pipe diameter 16-32 mm. Energy piles will be used as the primary circuit of the brine to water heat pumps used for heating – cooling the building for which they were designed. Within the GABI Cost project, both the theoretical considerations and the monitoring of the advantages / disadvantages of the 3 solutions, both in terms of energy performance and the geotechnical performance of the energy pilots, have been studied.
• they use the soil as a heat exchanger and energy storage medium;
• they add to their structural role of foundation piles the role of geothermal heating and cooling elements;
• the role of the fluid flowing inside the pipes is to transfer the heat of the soil to the primary circuit of the heat pumps; PEHA or PE-Xa pipes 16-32 mm in diameter are mounted on the W, UU or spiral.
– Only heat extraction – with heat pump (40-60 W / m; TEP = 2-15 ° C)
– Heat extraction and injection – with reversible heat pump (50-100 W / m; TEP = 25-35 ° C)
– The pipe configuration mainly characterizes both the energy performance and the geotechnical performance of the energy pilots;
– Designing the foundation on pilots is also essential for both energy performance and geotechnical performance of power pilots;
– The mass flow of fluids circulating in the pipe significantly influences energy performance only;
– Fluid rate variation seems more effective than changing the diameter of the pipe;
– To change the flow rate: increase fluid velocity:
• from 0.2 to 0.5 m / s => increase in heat transfer rate of 7%
• from 0.2 to 1 m / s => increase in heat transfer rate of 11%
III. DIAPHRAGM WALLS (SLURRY WALLS) – the diaphragm walls are designed with a structural design to protect the construction of a building by stabilizing the adjacent terrain. If the PEHA or PE-Xa pipe diameter 16-32 mm is mounted in the diaphragm walls, they become geothermal structures – the primary circuit of the brine to water heat pumps and the heat exchanger with the soil that reaches the storage medium. These geothermal structures will be used to operate the heat pumps that provide heating – cooling of the building for which they were designed.
Heat pumps on slurry walls – Oromolu Building / Piata Victoriei Bucharest
IV. TUNNELS – like the diaphragm walls, if in the tunnel walls (underground trains, underground passages, …), PEHA or PE-Xa pipe diameter of 16-32 mm is mounted on the reinforcement, they become geothermal structures – primary circuit of the brine to water heat pumps and heat exchanger with the soil. These geothermal structures will be used to operate heat pumps that provide heating – cooling of neighboring buildings, train stations, ….
GEOTHERMAL STRUCTURES – AN INNOVATIVE TECHNOLOGY
- Geothermal energy obtained from geothermal structures is an ecological technology, a solution for heating and cooling buildings with a significant reduction in CO₂ emissions and other greenhouse gas emissions;
- Ensure energy efficiency at the building level at the neighborhood / hour level, responding to the concept of sustainable city / town;
- It is complementary to any other renewable energy system being a local source of renewable energy (the natural heat present in the earth);
- No additional drilling is required, but minor changes in the design of the foundation and additional minimum installation costs;
- The use of geothermal structures ensures localization of the surrounding area that can be used for further expansions;
- The concept of geothermal energy can be adapted to spatial urban planning for cities of different sizes, with a different population density;
- Energy pilots form a large thermal battery (similar to night-storage heaters): they heat the soil during the summer to improve winter heating and cooling during the winter to increase cooling during the summer period by providing a storage system the energy otherwise difficult to achieve;
- Design of energy geostructures should be integrated into the design of conventional geotechnical structures through multidisciplinary real collaboration in all phases of the project. Geothermal analysis should be treated simultaneously with geotechnical issues in interaction with energy demand assessment. In the process, system interfaces must be handled with care.