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European Geothermal Congress 2019
Den Haag, The Netherlands, 11-14 June 2019
1
Application of the UNFC classification to open-loop ground source heat pump
systems: a case study
Paolo Conti1, Marco Pellegrini2, Gioia Falcone3
1 University of Pisa - DESTEC, Largo Lucio Lazzarino, 56122, Pisa (IT)
2 University of Bologna - DIN, Via Fontanelle 40, 47121, Forlì (IT)
3 University of Glasgow, University Avenue, G12 8QQ, Glasgow (UK)
paolo.conti@unipi.it
Keywords: Resource classification, UNFC,
groundwater heat pump.
ABSTRACT
This paper presents the application of the United
Nations Framework Classification for Resources
(UNFC) to an open-loop ground source heat pump
(GSHP) in Italy. The UNFC is a universal classification
system aimed at facilitating the comparison and the
decision-making process for all the stakeholders
involved in a specific energy project.
The classification object is the expected geothermal
energy use following Project development. In this case,
we deal with the replacement of some methane boilers
in the office buildings of an electric transformation
station with three reversible open-loop heat pumps
(nominal capacity, 3x70 kWth) and one open-loop
chiller (nominal capacity, 55 kWth).
The paper provides a general view of the UNFC
application, showing the classification steps the
information needed to complete the classification of a
groundwater heat pump system, according to a
“scenario” approach. The final Project classification at
the date of evaluation (2018) is “Commercial Project,
approved for development”. The geothermal Resource
is 6.7, 11.6, 13.8 PJ in thirty years as low, best, and high
estimate, respectively.
The paper highlights the general applicability of the
UNFC scheme and the benefits in terms of reporting the
Project energy production in a consistent perspective
including technical, economic, social, environmental
elements, together with uncertainties and risks
assessment.
1. INTRODUCTION
The development of geothermal energy is not related
only to technical subjects (i.e. engineering and
geology). In recent years, many works and research
projects have dealt with the effects of non-technical
features, such as social acceptance, policy, regulatory,
and economic frameworks, as well as the relationships
with financial stakeholders. In this framework, the lack
of a plain universal framework to define, report and
communicate about geothermal energy is slowing
down the geothermal development at a global scale, in
favour of other renewable or non-renewable energy
sources.
The decision about planning and funding of any energy
infrastructure (included the geothermal one) involves
many heterogeneous subjects and competencies:
governments, field owners, industrial operators,
investors, development banks and aid agencies,
reserves auditors, insurance companies, international
energy associations, agencies and councils. Among
many other elements, a common universal-adopted
terminology and a classification system is thus
necessary to rank possible energy alternatives,
according to the needs of all involved stakeholders.
The question of standardizing the assessment of the
geothermal potential (in a general sense) is not new:
there have been several attempts to provide a universal
classification scheme using different criteria. The
definition of commonly-used terms as “geothermal
energy”, “geothermal resource”, “geothermal
potential” has been widely discussed and reviewed in
scientific reviews and reports. The most popular past
and present classification approaches refer to (Falcone
et al., 2013, Falcone and Beardsmore, 2015):
- Accessibility and Discovery;
- Level of Temperature, Use, Type and Status;
- Technical, economic, sustainable, developable
“Potential”;
- Exergy;
- Geological Confidence and “Modifying Factors”.
Together with different classification criteria, many
heterogeneous classification classes are currently used:
e.g., resources, reserves, inferred, economical,
Conti et al.
2
uneconomical, and others. Shortly, a universal
terminology and classification approach has never been
established: each of mentioned classification systems
has drawbacks and limitations, leaving the door open
for ambiguity and subjectivity (Falcone, 2015, Falcone
and Beardsmore, 2015).
This is also due to an intrinsic limit of the geothermal
energy, as it refers to a very large number of
multidisciplinary subjects (geology, geophysics,
mining and wells sciences, thermal and electrical
engineering), geological contexts, exploitation and
conversion technologies (power plants, wells, thermal
engineering), different regulatory, social, and
environmental contexts around the world. Additionally,
we mention the need for defining a common framework
or a bridging logic for other energy sources.
In this perspective and with such ambitious goals, the
United Nations Framework Classification for Fossil
Energy and Mineral Reserves and Resources 2009
(UNFC-2009) is intended to be a universally acceptable
and internationally applicable scheme for the
classification and reporting energy sources, including
renewables and geothermal ones (ECE, 2013). It
captures the common principles and provides a tool for
consistent reporting energy extraction and conversion
process, regardless of the energy source. The
classification target moves from the characterization of
what is available in nature to the actual topic of interest
for the stakeholders, namely to provide indicators on
the feasibility, viability, risk, and sustainability of the
energy exploitation. In other words, the classification
scheme does not classify and compare energy sources,
but it deals with actual and well-defined energy
conversion project, during a well-defined operational
period, in a well-defined context. Details on the
classification procedures are shortly presented in
Section 2. The UNFC-2009 is also attractive for its
generality and possible application to all energy
sources, such as hydrocarbons and minerals. It has
already been aligned with worldwide established
classification protocols as the CRIRSCO Template and
the PRMS (ECE, 2013).
The document “Specifications for the application of the
United Nations Framework Classification for Fossil
Energy and Mineral Reserves and Resources 2009
(UNFC-2009) to Geothermal Energy Resources”
(hereafter geospec) was released in 2016, in the
framework of a MoU signed between UNECE and IGA
(Falcone et al., 2016). It includes the “rules of
application” of the UNFC to Geothermal Energy
Resources, and it is intended to be used in conjunction
with the general UNFC documents and the
specifications for the application of UNFC-2009 to
renewable energy resources (Charpentier et al. 2016).
Besides, a set of 14 case studies from Australia,
Germany, Hungary, Iceland, Italy, Netherlands, New
Zealand, Philippines and Russian Federation is been
issued to facilitate the understanding of the
specifications and how to apply the UNFC scheme to
various geothermal resources and technologies, such as
hydrothermal systems, EGS, direct uses, and heat
pumps (Falcone et al. 2017). Currently, an ad-hoc sub-
committee of the IGA resources and reserves
committee is dedicated at promoting, testing and
keeping updated the geothermal specifications.
In this paper, we present the application of the UNFC
to an Aquifer Thermal Energy Storage system (ATES)
to analyse benefits, possible limits, and rooms of
improvement of current geospec regarding this
technology. We show how UNFC classification helps
the communication and the understandings of the actual
level of favourability of energy projects, in terms of
energy efficiency, viability, risk and uncertainties,
permitting and environmental sustainability.
2. UNFC CLASSIFICATION SCHEME:
PRINCIPLES AND DEFINITIONS
The UNFC classification scheme introduces some
relevant features in the classification scheme to ensure
the consistency of the classified quantities and the
coherence/comparability among different cases.
Classical energy classification schemes (e.g.,
McKelvey diagram) focuses on the characterization of
the energy source, evaluating the level of exploitability
in a general technical and economical perspective.
UNFC introduces some innovative elements to better
define the actual advantages and the risk in a well-
defined project-related context. The object of the
classification moves from the classical “energy source”
to the very specific energy conversion project and
related expected energy product. In other words, UNFC
does not aim only at reporting the characteristic of the
energy source as it is in nature, but it refers to the very
specific project and its capability to transform that
source in a useful/marketable energy product in a
precise technical, economic, legal, social, political, and
environmental context. A Geothermal Energy Product
is “... an energy commodity that is saleable in an
established market” (Falcone et al., 2016). Typical
Geothermal Energy Products are electricity and heat,
but also other secondary compounds can be included in
the evaluation. In that perspective, the resource is not
the total amount of the geothermal energy potentially
convertible in a marketable product, but it is the actual
cumulative quantities of the Geothermal Energy
Products that will be extracted from the Source by the
Project in a defined period (Falcone et al., 2016).
The Project is the core of the classification procedure,
as it represents the between the Geothermal Energy
Source and quantities of Geothermal Energy Products.
Its definition includes scopes, a defined activity (or set
of activities), the maturity and the implementation level
of the technical apparatus at the moment of the
evaluation. Project definition also provides the basis for
estimating both costs and potential revenues (economic
evaluation) and decision-making.
The classification procedure and project definition are
based on a consistent scientific and thermodynamics
Conti et al.
3
background. Even with a simplified approach, concepts
as control volume, system boundary, energy fluxes are
clearly identifiable in the procedure (see, for example,
Table X). This is functional to the correct
understandings of the conversion efficiency, mass and
energy fluxes. The so-called Reference Points is one of
the main elements of the classification procedures: it
consists of a specified point in the Project layout at
which declared quantities are measured or estimated. It
does not have a fixed position and it can be placed at
any location of the extraction, processing, or sales
operations. Once defined, it is the unique and clear
reference to “locate” the classified energy quantities in
the overall energy conversion process. If a project
produces multiple energy products, there may be
different reference points for each product stream.
The classified quantity is energy, not power. In fact, the
classification procedure does not refer to a
nominal/theoretical operating condition, but it requires
the description of the timespan over which the
quantities are referred. In a general sense, it goes “...
from the Effective Date of the evaluation forward till
the end of the Project Lifetime/Limit”. Further
specifications can be found in (Falcone et al., 2016)
The uncertainty level of presented quantities (and the
general Project) is declared, explained and classified
according to three possible methodologies, including
both probabilistic and deterministic approaches (ECE,
2013, Charpentier et al. 2016, Falcone et al., 2016).
Uncertainty analysis is a fundamental step of the UNFC
classification to ensure a proper decision on the part of
stakeholders about project feasibility, viability and risk
(in any sense).
2.1 The three-dimensional classification system,
categories and classes.
The energy quantities/figures are classified according
to three fundamental criteria/categories (named E, F
and G), which are combined in a three-dimensional
system, as shown in Figure 1. Each project has a mark
on each of the three axes/categories and sub-categories
with a numerical mark from 1 to 4. The combination of
the three marks (namely, categories and sub-categories)
gives the final class and sub-class of the project (see
Figures2 and 3).
The first set of categories (the E axis) designates the
degree of favourability of social and economic
conditions in establishing the commercial viability of
the project, including consideration of market prices
and relevant legal, regulatory, environmental and
contractual conditions. The lowest rating is at the origin
of the axis and the most favoured at the top. Specific
guidelines on social and environmental considerations
have been issued and are available (Elliott, 2018a,
Elliott, 2018b).
Figure 1: UNFC categories and examples of classes.
The second set (the F axis) designates the maturity of
studies and commitments necessary to implement the
project projects. It is not related to the technology
maturity or to technical difficulties in a general sense,
but it evaluates the progress of the project concept,
design, authorization, funding, development, or
operation. The valuation on the F axis discloses if the
project is at the early exploration phase (before a
deposit or accumulation has been confirmed to exist),
till the running period when the project is already
operating and selling an energy commodity. Shortly,
the F axis aims at making stakeholders aware of the
actual level of project development in a managing
perspective.
The third set of categories (the G axis) designates the
level of confidence in the presented figures, including
the geological assessment and potential recoverability
of the quantities. The G axis is intended to reflect all
significant uncertainties impacting the estimated
quantities (i.e. the resources) that are forecast to be
extracted by the Project. Typical uncentres for
geothermal energy system include geology (the
source), energy conversion efficiency (the plant),
economic and regulatory context, thermal demand to be
met (direct system). We stress that uncertainties include
also all variability in the energy source, energy loads,
efficiency of the extraction and conversion processes,
social, economic, and environmental operating context.
There are three methods to estimate G-axis value
including both deterministic and probabilistic
approaches, named “incremental”, “scenario”, and
“probabilistic”. Details on the three methods can be
found in (ECE, 2013, Charpentier et al. 2016, Falcone
et al., 2016). As a general concept, three different
project outcome quantities are evaluated: the as low,
best and the high estimate and characterized by a high,
moderate, and low level of confidence, respectively.
For instance, in the “probabilistic” approach, the three
estimates named as “low estimate” (P90), “best
estimate” (P50) and “high estimate” (P10) indicate the
90%, 50% and 10% of probability of exceeding the
declared quantity, respectively.
Conti et al.
4
Figure 2: UNFC categories and examples of classes.
Figure 3: UNFC-2009 Classes and Sub-classes
defined by Sub-categories
3. CASE STUDY
ATES is a technology with a worldwide potential to
provide sustainable space heating and cooling by
(seasonally) storage and recovery of heat in the
subsurface (Gao et al., 2017; Bloemendal et al., 2015;
Lee, 2010). Adoption of ATES varies strongly across
Europe, which is on the one hand due to differences in
climatic and subsurface conditions, but on the other,
due to local barriers for implementation of ATES. The
E-USE(aq) innovation project (Pellegrini et al., 2019),
financially supported by the European Institute of
Innovation and Technology and by the Climate KIC in
the frame of the Sustainable Land-Use theme, started
on June 1st 2015 and has brought together nine partners
(in particular, University of Bologna, Nomisma
Energia and ASTER for Italy). The project objectives
include the realization of six different ATES pilot
plants in the following countries: The Netherlands
(Delft and Utrecht), Spain (Nules), Italy (Bologna),
Belgium (Ham) and Denmark (Birkerod). Different
sites have been identified for the installation of an open-
loop ground source heat pump (GSHP) system in Italy,
and after a preliminary techno-economic analysis
(Bianchini et al., 2017) the Martignone electric station,
near Bologna, was identified as the most suitable site.
3.1 Current plant and description of the Project.
The ATES pilot plant is located in the electric station
of Martignone, owned by Terna, which is the Italian
operator in electricity transmission grids. The electric
station of Martignone is a transformation station 380
kV/132 kV. Moreover, the station includes two
buildings, one (letter A in Figure 4) hosting the
emergency teams that cover the ordinary and
extraordinary maintenance of 2,800 km of electric lines
and the other one (letter B in Figure 4) hosting offices
and remote control station. The heating and cooling
plants of buildings A and B are not integrated.
Figure 4: Wells positioning in the Italian pilot plant.
Inf= infiltration wells, Ext= extraction wells,
Mon = monitoring wells.
The A building, which is named “changing room
building”, is a single floor building which includes a
kitchen, two changing rooms, two shower rooms, three
bathrooms and one tooling. The conditioned rooms
have a volume of about 1,600 m3 and are currently
heated and cooled by a complex series of plants: a
methane boiler (nominal capacity 103.5 kWth), two
reversible heat pumps (nominal heating capacity: 10
kWth, nominal cooling capacity: 9 kWth); four electric
splits for air cooling, three iron cast radiators, four
radiant ceiling panels; six 100 lt electric boilers for the
production of domestic hot water.
The B building, which is named “office building”, is a
two-floor building which includes several offices, four
bathrooms, three data centres, one battery room, one
remote control station. The conditioned rooms have a
volume of about 3,800 m3 and are currently heated and
cooled by the following plants: one methane boiler
(nominal capacity: 109.7 kWth), one water-to-air chiller
(nominal cooling capacity: 162 kWth), four 50 lt electric
boilers for the production of domestic hot water. All
conditioned rooms are equipped with fan coils and are
fed by a methane boiler and liquid-air chiller, except for
data centre rooms, which are only cooled.
Conti et al.
5
The energy Project to be classified consists of the
installation of three reversible open-loop heat pumps
(two in building B, one in building A, each one of about
70 kWth), and one open-loop chiller with a nominal
cooling capacity of about 55 kWth in building B. The
Project delivers thermal energy to buildings A and B,
including also some data centre rooms in building B
which need cooling all over the year. Hot water for
heating purpose is produced up to 65 °C, while cold
water for cooling is produced at 7 °C. The new system
substitutes the existing methane boilers in buildings A
and B and realizes a centralized cooling system for
building A. The new plant is integrated by the existing
water-to-air chiller installed in building B, and with two
electric boilers of 57 kWth each (one for each building),
which are used as back-up unit of the ATES system for
space heating. Heat exchange with groundwater is
provided through plate exchangers and three couples of
extraction-injection wells.
3.3 Energy audits: buildings demand and current
system performances.
The peak requirements of heating and cooling power
were estimated as in Table 1 to correctly design the
open-loop GSHP. Heating peak has been computed
accordingly to EN 12831:2003 by the software
EdilClima. The external design temperature was fixed
at -5 °C, while the conditioned rooms temperature was
set at 20 °C. Cooling peak was estimated accordingly
to the Carrier-Pizzotti method through the software
EdilClima. The design has been done by considering an
external air temperature of 33 °C, while the temperature
of the conditioned room was set at 24 °C. One
interesting result is that cooling peak demand is higher
than heating one, and that it is concentrated in the office
building. Then, according to the monthly-average
climate data, an estimation of annual energy needs for
heating and cooling has been carried out, accordingly
to UNI EN ISO 13790:2008 and UNI/TS 11300-
1:2014. The results are the buildings energy demand of
170 MWh/yr for heating and of 49 MWh/yr for cooling.
Due to the oversizing of existing methane boilers, a
seasonal efficiency of about 80% has been attributed to
the existing plants, considering heat generation,
distribution, regulation and emission. The methane
consumption has been estimated to be about 25,000
Nm3/year. The latter value has been compared with the
billing data of the year 2013, showing an optimal
agreement (24,160 Nm3). The computation of past
electric energy consumption found different technical
obstacles. First, there is no separated computation of
electric energy consumption, i.e., there is one electric
energy meter for the whole Martignone station. The
presence of one meter is justified by the fact that Terna
has a special contract for energy consumption, so there
was no need to measure the consumption of different
subsystems fed by electric energy in the station.
Moreover, the larger quantity of electricity is consumed
by the electric station itself, and not by the buildings’
facilities, so there is no chance to make a seasonal
analysis of the whole electric consumption to identify
summertime consumption due to air conditioners.
However, following the data in Table 1 and assuming a
seasonal energy efficiency ratio of 3.0, the electricity
needed by the existing water-to-air chillers can be
estimated in 16,300 kWh.
Table 1: Estimated peak and buildings energy
demand for heating and cooling.
Building
A
Heating
Cooling
Peak
[kW]
Energy
[MWh/y]
Peak
[kW]
Energy
[MWh/y]
Tooling
16.8
20.0
0.0
0.0
Changing
room
11.8
14.0
13.1
4.0
Other
rooms
28.3
33.0
2.7
1.0
Total A
56.9
67.0
15.8
5.0
Building
B
Heating
Cooling
Peak
[kW]
Energy
[MWh/y]
Peak
[kW]
Energy
[MWh/y]
Ground
floor
43.1
51.0
68.7
22.0
Second
floor
44.7
52.0
71.2
22.0
Total B
87.8
103.0
139.9
44.0
TOTAL
(A+B)
144.7
170.0
155.7
49.0
3.4 Characterization and evaluation of the
geothermal/renewable source and possible
environmental issues.
Preliminary pumping test started on 19th September
2016 and was completed on 31st October 2016. Test
was carried on a 100 meters’ depth and 4’’ diameter
well through: a submersible centrifugal pump with a
vertical axis, a water volumetric flowrate meter, and a
phreatimeter used to measure the variation of the water
level. The preliminary pumping test was realized
accordingly to EN ISO 22282-4.
The results of the pumping test (Bianchini et al., 2017)
showed that the maximum water flow rate that can be
extracted from one well has to be set at 1.8 l/s (6,5
m3/h), otherwise the groundwater level in the well
would drop dramatically. During a following constant
rate test at 1.8 l/s, two nearby wells were used as
monitoring wells. The lowering of the aquifer was in
the order of centimetres. It was also noted that the
aquifer has very quick recharging, since, after the pump
was stopped, in less than two minutes the level turns
into the starting value. Since the flowrate potential
extraction from one well is limited, the minimum
number of wells to guarantee the satisfaction of the
peak thermal demand must be identified. Regional
permit allows a maximum temperature variation of
injected groundwater of 5 °C, and so, by considering
the peak demand (see Table 1), the minimum number
of extraction wells results equal to three.
Conti et al.
6
Further pumping tests were organized between October
2017 and February 2018 to verify the behaviour of the
aquifer in conditions similar to the peak demand
operating ones (i.e. three pumps extracting the
maximum groundwater flowrate from the three
extraction wells and injecting it back in the three
injection wells). The test completed on 2017 and 2018
substantially confirmed the preliminary test results.
The use of tracer dyes is a technically valid and cost-
effective method for characterizing contaminant fluxes
and hydraulic properties in complex hydrogeological
systems. In Terna site this method has been applied to
have relevant information about water flow direction
within the groundwater during pumping test at a
variable flow rate and with the maximum flow rate
allowed. A test has been realized with contemporary
water extraction from the three extraction wells and
water re-injection in the three injection wells. The
evaluation of water flow direction allows to better
evaluate the thermal short-circuit risk. No international
standards are available to determine how the test should
be carried on. The test has been arranged as follows: a
concentration of about 200 g/l of Sodium-Chloride
(NaCl) has been induced in one injection well – the
nearest one to extraction wells. Then, the three pumps
installed in the three extraction wells started pumping
at maximum flow rate. A three days continuous
monitoring has been completed: a conductivity
variation has been observed only in the nearest
injection/extraction well-couple, so it was concluded
that thermal short-circuit risk should be very low.
Finally, chemical-physical characteristics of the
groundwater were assessed to verify if the aquifer
contains some pollutants and to evaluate the clogging
potential of wells. The results of groundwater samples
analysis in 2016 showed a high manganese
concentration. After a brief literature survey, it was
found that high concentration of manganese and/or iron
is quite common in the area and it is not of
anthropogenic origin. Further samples have been taken
from the three extraction wells during the last pumping
test in 2017 and 2018. In particular, two different tests
were performed: redox potential, measurement of
manganese concentration in the sample and in the
filtered portion of the sample (0.45 micron filter), to
estimate the percentage of manganese presence in
colloidal form. Since the manganese is quite
completely unfiltered, it means that there is a negligible
fraction of not dissolved manganese, and so manganese
is present mainly in colloidal form, which is a good
result since clogging problems due to manganese
precipitation in the injection wells should be avoided.
3.5 Product type and reference point(s)
The classified energy quantity, i.e. the Resource,
consists of thermal energy exchanged with the ground
source, namely the “extracted” geothermal energy.
According to Falcone et al., 2016 and Falcone et al.,
2017, the classification of a GSHP Project requires the
presentation of the overall system energy balance and
associated energy quantities in four main points (see
Figure 5): the energy exchanged with the ground source
(point A), the thermal output of the heat pump unit
(point B), the driven energy (point C), and the total heat
delivered to the end-user system (point D).
In this assessment, point A is chosen as Reference Point
to report and classify the Geothermal Energy Resources
according to UNFC-2009. For the sake of clarity, all the
main energy quantities related to the project operation
are summarized in Table 2. Since the pilot plant can be
operated also in reversible mode (i.e. cooling), also the
energy “injected” in the ground source is considered: in
this case, the ground works as a heat sink more than an
heat source. This issue represents one of the limit of the
UNFC classification.
Figure 5: Schematic representation of the energy
fluxes and evaluation points in a groundwater
heat pump system (heating mode).
3.6 The “scenario” approach: expected energy
quantities and project lifetime.
According to UNFC (ECE, 2013), the degree of
uncertainty associated with the energy estimates must
be always reported and discussed. The so-called
“scenario” approach consists of generating three future
production profiles named low, best and high estimates.
A low estimate scenario is directly equivalent to a high
confidence estimate (i.e. G1), whereas the best estimate
scenario is equivalent to the combination of the high
confidence and moderate confidence estimates
(G1+G2). A high estimate scenario is equivalent to the
combination of high, moderate and low confidence
estimates (G1+G2+G3). Additionally, we recall that the
three scenarios can be associated to the same principles
of estimates derived from a probability analysis: the
quantities associated to the low, best, and high estimate
scenarios reflect the probability of 90%, 50%, and 10%
to be exceeded during the actual operation, respectively
(Charpentier et al., 2016).
- Low estimate. In this scenario, ATES system is
assumed to deliver the 70% of both heating and
cooling demands for 30 years (i.e., project lifetime).
This scenario is very unlikely, as the nominal water
flow rate, about 3.8 l/s, is lower than the proven
sustainable exploitation of the aquifer (5.4 l/s, see
Section 3.4), which is anyway able to satisfy a peak
demand. Additionally, both the three reversible heat
pumps and the chiller are oversized with respect to
the heating and cooling demands. The oversizing is
Conti et al.
7
justified by the specific nature of the site: an
electrical station which needs high requirements in
terms of operation guarantee, especially for the data
processing center. Due to these requirements, great
part of the plant components was oversized or
redundant. Therefore, a 70% of load coverage, can
be justified only in case of unexpected serious
system failures or forced stops. For example, if long
term impact on groundwater temperature is
produced by the plant, the regional authority may
decide to retire the authorization for groundwater
extraction/injection. This case is remote, also
because groundwater temperature will be monitored
to evaluate the seasonal impact of heating and
cooling extraction from the aquifer, and so
countermeasures can be quickly adopted. However,
assuming an average 2 °C temperature
increase/decrease of the extracted groundwater for
cooling/heating purpose over the project lifetime,
the mean seasonal COP and EER would be 3.7 and
8.0, respectively. Electric boilers efficiency is
estimated in 90%, while water-to-air chiller
seasonal EER is fixed at 3.0. The combination of
these two efficiencies and the assumed load ratio
between the GSHP and back-up generators lead to
a yearly electric energy consumption of about 98.1
MWh (88.9 MWh for heating and 9.2 MWh for
cooling, see Table 2).
- Best estimate. In this scenario the ATES system
meets the 85% of heating and cooling demand,
while the remaining 15% is supplied by back-up
units (electric boilers and water-to-air chiller). The
reduced working hours can be caused by the
clogging of the injection wells (i.e. manganese
precipitation, see Section 3.4), reduced groundwater
extraction capacity (i.e. water scarcity in
summertime), or components failure. Moreover, a
negative impact of thermal short-circuit between
extraction and injection wells is accounted: in the
case of an average 1 °C increasing/decreasing of the
extracted groundwater temperature during the
project lifetime (i.e., 30 years), the mean seasonal
COP and EER would be 3.9 and 8.3, respectively.
The result is a yearly electric energy consumption
that can be estimated in about 72.9 MWh (65.4
MWh for heating and 7.5 MWh for cooling, see
Table 2).
- High estimate. In the best scenario, groundwater
heat pumps are assumed to work with a seasonal
COP of about 4.0, while the seasonal EER of the
chillers have been estimated in about 8.5. The
system is considered as able to satisfy 100% of
heating and cooling demands (justified by plant
oversizing aforementioned) and no relevant
thermal short-circuit occurs between extraction
and injection wells (justified by preliminary test,
see section 3.4). The EER value is very high if
compared with water-to-air chiller since in
summertime the air can reach temperatures up to
35-40°C, while groundwater is more or less
constant under 20°C. Shortly, for the assumed 30-
year lifetime, yearly electric energy consumption
can be estimated in about 48.3 MWh (42.5 MWh
for heating and 5.8 MWh for cooling). The energy
fluxes are summarized in Table 2.
Table 2. Energy fluxes in MWh/year for the three scenarios analysed. Letters A, B, C refer to Figure 5.
4. UNFC CLASSIFICATION
The final classification for the Project is shown in Table
3. The geothermal Resource to be classified is the heat
extracted by the ground source in the reference point A.
The final class and sub-class are “Commercial Project,
approved for development”.
The assigned classification depends on the economic
evaluation that is the most critical element among the
features list considered in the E-axis (see the decision
trees in Falcone et al. 2016). The project has favourable
legal. regulatory, market access, social, political, and
authorization conditions. All the required permits, such
as water extraction and injection, have been released.
The environmental assessment shows a significant
reduction up to 11.7 tons of oil equivalent (TOE) and
of 35.8 tons of equivalent CO2 emissions with respect
to a traditional boiler/chiller. There is no air, water, soil
pollution or material disposal associated to the project
operation. Table 4 shows the economic figures of the
investment as a function of the scenarios: the
Scenario
Operation
Energy
exchange
with the
aquifer
(A)
Energy
delivered
to the
user
system
(B)
Electricity
input to
the
GSHPs
(C)
Energy
delivered
by the
back-up
units
Electricity
input to
the back-
up units
Total
electricity
consumption
High
Heating
127.5
170.0
42.5
0
0
42.5
Cooling
43.3
49.0
5.8
0
0
5.8
Best
Heating
107.4
144.5
37.1
25.5
28.3
65.4
Cooling
37.0
42.0
5.0
7
2.5
7.5
Low
Heating
86.8
119
32.2
51.0
56.7
88.9
Cooling
30.0
34.3
4.3
14.7
4.9
9.2
Last name of author(s); for 3 and more, use “et al.”
8
investment cost (including design, preliminary tests,
authorization process) is rather high and the annual
savings achievable are not able to make the investment
very attractive, since the payback time is quite long (12
– 14 years) in all the three scenarios.
Table 3. Final classification (reference time: 30 years, Reference point A*:).
Classification based on
UNFC classes
Classified
energy
quantity(ies)
Supplemental information
E1.2; F1.2; G1
9.3 TJ
(86.8 MWh/y)
- Nominal capacity of the GSHP system: 210/265 kWth
heating/cooling;
- Expected seasonal COP/EER: 3.7/8.0.
- Assumed Project lifetime: 30 years.
- Ground-coupled apparatus deliver about 75% of both
building and cooling load.
E1.2; F1.2; G1+G2
11,6 TJ
(107.4 MWh/y)
- Nominal capacity of the GSHP system: 210/265 kWth
heating/cooling;
- Expected seasonal COP/EER: 3.9/8.3.
- Assumed Project lifetime: 30 years.
Ground-coupled apparatus deliver about 85% of both building and
cooling load
E1.2; F1.2; G1+G2 + G3
13.8 PJ
(127.5 MWh/y)
- Nominal capacity of the GSHP system: 210/265 kWth
heating/cooling;
- Expected seasonal COP/EER: 4.0/8.5.
- Assumed Project lifetime: 30 years.
- Ground-coupled apparatus deliver about 100% of both
building and cooling load
Project Location: Bologna, Italy
Date: 2018
Date of evaluation: 2018
Quantification method: simulation and well-testing methods.
Estimate type (deterministic/probabilistic): deterministic scenario.
4.1 E category classification and subclassification
Category
UNFC definition
Brief
reasoning for
classification
E.1
Extraction and sale
have been confirmed
to be economically
viable
The high
investment
cost and the
long payback
period (longer
than 10 years)
may result not
attractive for
investors.
The payback
period can be
shortened if
subsidies are
considered.
E1.2
Extraction and sale
are not economic on
the basis of current
market conditions
and realistic
assumptions of future
market conditions,
but is made viable
through government
subsidies and/or
other considerations.
The high investment cost relates to the specific nature
of the site: an electrical substation with high standard
requirements regarding operation continuity. Due to
these requirements, great part of the construction works
is redundant to ensure constant energy production back-
up. The resulting higher investment costs affect the
economic figures. The high investment is also
influenced by the complex monitoring system to
measure with high accuracy both the thermal plant
performance and the impact of the pilot on the
groundwater. Furthermore, the investment includes the
retrofitting of existing distributing pipelines and
heat/cold terminals and the preliminary tests carried on
for the characterization of the aquifer, which may be
not necessary in similar installations.
Table 4. Main figures of the project economic
assessment (reference time: 30 years).
Category
Amount without subsidies
High
scenario
Best
scenario
Low
scenario
Investment
460 k€
460 k€
460 k€
Discount rate
4%
4%
4%
NPV
520 k€
480 k€
408 k€
Payback time
12 years
12 years
14 years
Amount with subsidies
High
scenario
Best
scenario
Low
scenario
Investment
460 k€
460 k€
460 k€
Discount rate
4%
4%
4%
NPV
618 k€
570 k€
472 k€
Payback time
8 years
9 years
11 years
Last name of author(s); for 3 and more, use “et al.”
9
The investment becomes more attractive if subsidies
are considered: payback period is shortened to 8 years
in the high scenario due to about 70.000€ of the whole
investment that can be fiscally deduced in ten years,
plus the benefits coming from white certificates selling.
On the other hand, Table 4 highlights the relatively low
impact of electric energy bills increasing from high to
low scenario: this is a specific condition of the site, that
has very low electric energy costs.
4.2 F category classification and subclassification
Category
UNFC definition
Reasoning for
classification
F.1
Feasibility of
extraction by a
defined
development
project or mining
operation has
been confirmed
All the
preliminary
studies and
analysis are
completed, as
well as the
Project design
and CAPEX
commitment.
F.1.2
Capital funds
have been
committed and
implementation
of the
development
project or mining
operation is
underway.
The project design, together with the environmental
and economic assessment, have been completed: the
construction operations are about to start as soon as
final authorizations will be received from local
authorities.. All the capital funds have been committed.
4.3 G category classification and subclassification
Category
UNFC definition
Reasoning for
classification
G1
Quantities
associated with a
known deposit that
can be estimated
with a high level of
confidence.
Low-estimate
See section 3.6
G2
Quantities
associated with a
known deposit that
can be estimated
with a moderate
level of
confidence.
Best-estimate
See section 3.6
G3
Quantities
associated with a
known deposit that
can be estimated
with a low level of
confidence.
High-estimate
See section 3.6
5. CONCLUSIONS
This paper presented the application of the United
Nations Framework Classification for Resources
(UNFC) to an open-loop ground source heat pump
(GSHP) in Italy. The classified Project concerned the
replacement of the methane boilers in two service
buildings in a 380kV/132kV electric transformation
station. The new thermal generators are three reversible
open-loop heat pumps (3x70 kWth) and one open-loop
chiller (55 kWth).
The final Project classification at the date of evaluation
is “Commercial Project, approved for development”.
The geothermal Resource is 9.3, 11.6, 13.8 PJ in thirty
years for the low, best, and high estimate, respectively.
The paper provided a general view of the UNFC
application, showing the all the steps needed to
complete the classification: definition of the Project
within a greater and complex energy system, the
description of the product type (i.e., the Resource), the
reference point, and project lifetime. The description
included both source experimental characterization and
thermal load evaluation, together with a clear
assessment of the energy conversion performances.
The paper showed the general applicability of the
UNFC scheme in a complex energy system made of
integrated generators and different energy
technologies. The final UNFC class and subclass
clearly summarize all technical, environmental, social,
regulatory, economy features, helping the
understanding of the actual level of development of the
project, expected energy and economical performances,
and associated uncertainties.
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