Page 65 - European Energy Innovation - Summer 2016 publication
P. 65

Summer 2016 European Energy Innovation  65

                                                                     GEOTHERMAL ENERGY

systems, energy thermoactive              Working principles
geostructures or energy geostructures     of energy piles
are recently experiencing exponential
growth. This category includes all the             Heat
ground-embedded structures, such as                pump
tunnels, anchors and linings, shallow
foundations, piles and diaphragm walls,     Heat
used to exchange heat with the ground.      exchanger
In general, a geotechnical structure can    piles
be thermally activated by embedding
polyethylene pipes in its concrete
body. The fluid flowing in the pipes
constitutes the means to transfer heat
from the ground to the buildings or
vice versa thanks to heat pumps.

Since the beginning of the 1980s,         geostructures induced by temperature       The disparities highlight the need
geothermal energy has been                variations, structural aspects should be   to synthesize research and practice-
increasingly obtained from foundation     to be considered as well.                  based knowledge from across national
elements, at first from base slabs,                                                  and disciplinary boundaries in order
then from piles, diaphragm walls and      Despite the significant number of          develop better understanding
tunnels. Energy geostructures have        operating energy geostructures in          and more widespread use of this
been increasingly constructed in          Europe, the development of specific        technology. In the future, the deeper
Europe. The design of these energy        design rules and dimensioning              understanding of heat exchanges in
systems is inherently interdisciplinary   approaches has been slow. Attempts         the ground and their application to a
and involves geology, hydrogeology,       to provide a set of recommendations        wide range of geotechnical structures
geotechnical engineering and              for piles subjected to temperature         can improve this technology for more
thermal engineering. A vast amount        variations were carried out starting from  efficient and streamlined application.
of information across several fields      2005 in Switzerland, Germany, United       One of the critical contributions
is needed for a successful design:        Kingdom and France. However, most          expected is a better methodology to
thermal, mechanical and hydraulic         of this documentation provides only        assess interaction among multiple
properties of the soil, as well as        general indications and does not allow     thermoactive geostructures within
the concrete, assessment of local         the adoption of this technology across     urban districts. City managers
atmospheric conditions, definition        Europe for a wider range of projects.      need methods to predict the effect
of the operating system thermal           An international comprehensive             of multiple systems operating
action, and overall energy demand         document addressing in detail              concurrently to minimize interferences
for the building or the facility to be    the mechanical design of energy            and provide a planning guidance for
conditioned. Integration of all these     geostructures is much needed.              permitting purposes. It is expected
aspects is required to optimize the                                                  that the COST Action GABI will foster
system performance.                       The heterogeneous development              the development of thermoactive
                                          of applications and research on            geostructures and will be a big step
The energy efficiency performance         thermoactive geostructures in              towards future market development
of these systems depends on the           European countries is the main             and widespread usage of this
exchange mode between the ground          reason to launch a COST Action.            innovative technology. l
and the thermoactive geostructure.
Currently, heat exchange is estimated     OTHER INFORMATION
based on operating assumptions,
but accurate modelling needs to           COST Association web page:
be substantially improved to allow        COST GABI web page:
a precise calculation. The thermo-        LinkedIn address:
mechanical effects also need to be        Facebook address:
assessed in order to ensure system
operation without affecting safety and
functionality. Indeed, due to expansion
and contraction of the thermoactive
   60   61   62   63   64   65   66   67   68   69   70