Page 65 - Analysis and Design of Energy Geostructures

Energy geostructures 35

compared to the latter. One final difference is that usually the bending radius of the
pipes in energy geostructures is greater compared to that characterising the pipes in
conventional geothermal heat exchangers. This fact involves a lower flow resistance of
the fluid circulating in the pipes, which results in a lower pumping power and thus in
a lower operation cost.
With reference to the purposes of the heat exchange that can be established with
energy geostructures various are the advantages compared to other technological sys-
tems. The use of energy geostructures for heating and cooling superstructures to reach
comfort levels in the built environment reduces the environmental impact of any con-
struction and can be exploited to get incentives for the design project and construction
of the superstructure. The use of energy geostructures for contributing to the produc-
tion of hot water for anthropogenic purposes reduces the costs compared to systems
entirely resorting to more conventional technologies and is again characterised by a
reduced environmental impact. When energy geostructures are employed for contrib-
uting to the production of hot water for agricultural or tank-farming uses, cost savings
can be achieved via lower operational costs and environmental impacts. The use of
energy geostructures for providing heat to prevent the icing of pavements and decks
of infrastructures such as roads, bridges, station platforms and airport runways involves
reducing the environmental and structural impacts of these applications because the
use of salts or grits is not necessary and hence chemical and mechanical degradation
phenomena that would otherwise be enhanced do not occur. The use of energy geos-
tructures for storing heat in the subsurface allows harvesting at a later time waste heat
that would be lost otherwise as well as establishing particularly effective and efficient
energy systems.

2.3 Energy geostructure operation modes
2.3.1 Possible operations

Two operation modes of energy geostructures involving a markedly different concep-
tual purpose can be employed: the heat exchange operation and the heat storage oper-
ation. Depending on whether energy geostructures are used for heat exchange or
storage purposes through the respective operations, so-called ground source heat
pump systems (GSHPS) and underground thermal energy storage systems (UTES) are
employed, respectively.

2.3.2 Heat exchange operation
In the heat exchange operation, the primary purpose of energy geostructures is to use
the ground as a heat reservoir. The heat present in the ground is typically extracted
and transferred to the superstructure in cool climates or cold seasons. In contrast the