Urban energy geostructure in highway tunnels as seasonal storage

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Models/Systems, Technologies and Building systems

DESCRIPTION:

The study, design, and testing of a system to retrofit and thermally activate an existing tunnel (in operation or abandoned) for an energy purpose not envisaged originally. The system includes a network of pipes capable of transporting a heat transfer fluid. A prototype of such a system is being investigated by means of preliminary numerical analyses with the final aim to install it in the Piedicastello tunnels within the Trento demo. The tunnels, today abandoned and devoted to an exhibition hall, will be turned into a heat exchanger with the ground and with the internal environment for road de-icing and/or heating and cooling purposes of an adjacent building to test the potential of the identified solution in a realistic operating environment.

BUSINESS ROUTE

Target Users

Citizens and NGOs, Constructors, Landlords, Local authorities, Real-estate developers, Research community, Social, public and cooperative housing providers

VALUE

The concept of assigning a double role, both structural and energetic, to structures in contact with the ground – so-called energy geostructures – has been spreading in the last years for contributing to the production of clean, renewable thermal energy. The system offers the opportunity to re-use an existing tunnel, built for different reasons (generally transport), also for the exchange of heat with the ground/inner air and, consequently, to heat or cool housing units, providing the buildings’ base load, or other potential users, such as stations, as well as for the de-icing of roads and highways, through a sustainable and renewable energy system. It also contributes to the achievement of the minimum percentage thresholds for energy supply from renewable resources to produce domestic hot water, winter and summer air conditioning established by legislation for new buildings and the renovation of civil/building works.

APPLICATION

The prototype in Piedicastello will demonstrate the feasibility of exchanging heat with the surrounding ground through the geostructure, namely the tunnel, for serving a specific building and/or infrastructure. However, metro tunnels and other types of underground structures very often exist in or close to urban centres. Therefore, the technology is optimal for a local harvesting and for widespread distribution of thermal energy at both single space and district scales and could be integrated in low-temperature district heating and cooling networks. The technology potential may be even enhanced by coupling it with other renewable energy-based systems, such as for instance solar collectors. This coupling can lead to interesting applications such as Underground Thermal Energy Storages (UTES). The integration of solar panels for hot water production with the geothermal loops can provide thermal storage abilities to the system and can be used as a thermal source for low-enthalpy energy storage in the ground. This innovative integrated system would allow to buffer differences between thermal supply/demand at a local level, which is particularly attractive due to the inherent asymmetry nature of intermittent renewable energy sources. Tunnels could thus benefit from a smart and sustainable approach and be retrofitted for transforming them into energy generators having positive impacts in terms of social and economic activities.