Page 42 - Analysis and Design of Energy Geostructures

Energy and geotechnologies 11

The Energy Performance of Buildings Directives (Energy Performance of
Buildings Directive, 2002, 2010), the Carbon Neutral Design Project and the
ASHRAE Vision 2020 represent examples of key directives and initiatives for the
development of a low-carbon built environment. The goal of the referenced directives
and initiatives is to require (or to foster) the design and construction of so-called
“nearly zero-energy buildings (NZEB)”, “carbon neutral buildings”, and “net zero
energy buildings”, respectively, in the years to come.
For example the Energy Performance of Buildings Directives required all new
public buildingsconstructedinthe European Uniontobenearlyzero-energy from
2018, while all new general buildings are to be nearly zero-energy by the end of
2020. A NZEB is defined as “abuildingwithveryhighenergyperformance”,where
“the nearly zero or very low amount of energy required should be extensively
covered by renewable sources produced on-site or nearby” (Energy Performance of
Buildings Directive, 2010). The purpose to develop NZEB is to achieve construc-
tions with significantly reduced energy consumption combined with the increased
use of low-carbon energy sources to meet this consumption. The broad definition of
“NZEB” hasbeenadapted in variousMember Statesofthe European Unionwhile
considering the feasibility of implementing such a concept in their national contexts
(Buildings Performance Institute Europe, 2015). In Italy, for example the definition
of NZEB proposed by the Energy Performance of Buildings Directive (2010) has
been adopted and implemented in the construction sector by the national law 90/
2013. In France this definition has been extended to “positive energy building” and
will be adopted and implemented in the construction sector from 2020 by the tech-
nical document RT2020. The concept of positive energy building advances the con-
cept of energy consumption being close to zero that characterises NZEB by
referring to a building that produces more energy, for example from renewable
energy sources available on-site, than it consumes during a reference period of time
(e.g. 1 year).
Based on the aforementioned aspects, it appears abundantly clear that the concep-
tual development, analysis, design and application of environment-friendly technolo-
gies harvesting on-site renewable energy sources for targeting the supply of heating
and cooling energy to the built environment [i.e. aspect (3)] represent crucial contri-
butions to a sustainable development.

1.3 Geothermal energy
1.3.1 General
Geothermal energy is the natural thermal energy contained in the Earth’ssubsurface,
which can be divided into the crust, the mantle (subdivided into the upper and
lower mantle), and the core (comprising the outer and inner core). This natural heat