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Enhancing Storage Integration in Buildings with
Photovoltaics (PV-ESTIA project)
Angelos I. Nousdilis, Georgios C. Kryonidis, Eleftherios O. Kontis, Grigoris K. Papagiannis
Power System Laboratory, School of Electrical & Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki,
Greece, grigoris@eng.auth.gr
Georgios C. Christoforidis, Aggelos S. Bouhouras
Western Macedonia University of Applied Sciences, Kozani, Greece, gchristo@teiwm.gr
George Georghiou, Stavros Afxentis
FOSS Research Centre for Sustainable Energy, University of Cyprus, Nicosia, Cyprus
Ioannis Papageorgiou
Electricity Authority of Cyprus (EAC)/Distribution System Operator (DSO), Nicosia, Cyprus
Sanja Veleva, Marija Kacarska, Vlastimir Glamocanin
Faculty of Electrical Engineering and Information Technologies, Ss. Cyril And Methodius University, Skopje
Petar Kisyov
Energy Agency of Plovdiv , Plovdiv, Bulgaria
Abstract—European Union’s energy targets for 2030 include
the transformation of the building stock to nearly zero energy
buildings (NZEBs). NZEBs are characterized by reduced net-
energy demand, since most of their energy needs are met by on-
site renewable energy sources, especially photovoltaics (PVs).
Consequently, in the following years, a considerable amount of
intermittent solar generators will be connected in the electrical
grid posing new challenges concerning the secure and reliable
grid operation. To effectively address these challenges, the
integration of energy storage systems (ESSs) in NZEBs is
considered as the most promising solution. Towards this
objective, the PV-ESTIA project ai ms to develop an innovative
management scheme for hybrid PV and storage systems in order
to promote the use of ESSs in the building environment. In the
framework of the project, the proposed management scheme will
be tested and validated under real-field conditions at pilot
installations placed in the Balkan Mediterranean (Balkan-MED)
region. Additionally, the distinct features and functionalities of
the proposed scheme will be further evaluated during the project
through the development of optimization tools. This paper
presents briefly the main activities and the expected outcomes of
the PV-ESTIA project, focusing on the conceptual analysis of the
foreseen management scheme for hybrid PV and storage systems.
Additionally, potential barriers related with the integration of
ESSs in buildings at the Balkan-MED region are identified and
discussed. Finally, a detailed analysis of the pilot installations
which will be developed in the framework of the PV-ESTIA
project is presented.
Keywords— Energy storage system, nearly zero energy
building, photovoltaic system, self-consumption.
I. I
NTRODUCTION
The transformation of the European Union (EU) building
stock to nearly zero energy buildings (NZEBs) has already
started. This tendency is expected to grow rapidly in the
following years, since the announced EU targets for 2030
require that both new and existing buildings should be NZEBs
[2]. The NZEB concept, which was firstly introduced in the
recast of the energy performance buildings Directive [1],
requires that the majority of thermal and electrical energy
needs of a building are locally covered, using on-site renewable
energy sources. The most suitable RES technology for
integration in buildings are photovoltaics (PVs), mainly due to
their modular structure and small installation space.
Consequently, a substantial amount of intermittent PVs is
expected to be connected to the electrical distribution networks
in the following years.
High PV penetration levels may result in unacceptable
stress on the electrical grids during hours with high solar power
generation. The most important technical challenges that may
arise include overvoltages [3], overloading of network
equipment [4], and fault protection issues [5]. For this reason,
distribution system operators (DSOs) may limit the installed
capacity in certain feeders where such problems are expected to
rise. These technical issues can be effectively tackled, using
energy storage systems (ESSs) to store locally the energy that
is not consumed during high generation periods [8].
This work has been co-funded by the European Union and National
Funds of the participating countries through the Balkan-MED Programme,
under the project “PV-ESTIA - Enhancing Storage Integration in Buildings
with Photovoltaics”.
2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republising this material for advertising or
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Citation Information: DOI: 10.1109/ENERGYCON.2018.8398760
Additionally, it is worth noticing that the installation of ESSs in
buildings with PVs can increase the self-consumption by
storing the surplus energy for later use [5], [7], and thus
provide relief to the stressed feeders [9]. To this end, there is a
strong need to develop a management scheme for the efficient
coordination among PV, ESS, and the energy needs of the
building.
Although the exploitation of ESSs is an important step
towards NZEB transformation, current policies and DSO
regulations concerning on-site RES and ESS do not always
promote the widespread use of such hybrid systems.
Specifically, on the Balkan–Mediterranean (Balkan-Med)
region, the use of the feed-in tariff (FiT) compensation policy
discourages the use of storage. Moreover, in some countries the
operation of ESS is currently prohibited by the DSO. To
efficiently overcome this problem, PV-ESTIA project aims to
study the current national regulations and legislations and to
propose new policies and recommendations for the countries of
the Balkan-Med region, in order to facilitate the integration of
PV and storage in the building stock. Furthermore, in the
framework of the PV-ESTIA project, an innovative energy
management scheme will be developed. The proposed scheme
targets to maximize the self-consumption of prosumers by
taking into account current and future DSO technical
regulations, consumption and generation profiles, electricity
pricing policies as well as thermal and electrical needs of the
building. The management system will be tested and validated
under real-field conditions in pilot installations, placed across
the Balkan-Med area. Results of the pilot installations will also
be used to develop policies and technical regulation
recommendations for the further integration of PVs and ESSs
in the region.
The remaining of the paper is structured as follows: In
Section II, the state of the art concerning current policies about
PVs, storage and NZEBs among the participating countries is
briefly described and discussed. An overview of the PV-ESTIA
project structure is presented in Section III. The conceptual
design of the proposed management scheme is analyzed in
Section IV. Section V describes the pilot installations, which
will be used for the evaluation of the proposed energy
management scheme, while Section VI analyzes the procedure
which will be adopted to further investigate the effectiveness of
the proposed scheme using simulation tools. Finally, Section
VII discusses the expected project outputs and concludes the
paper.
II. S
TATE OF THE
A
RT ON THE
B
ALKAN
-MED
R
EGION
Four countries of Balkan-Med region are participating in
this project. A list of the specific organizations that belong to
the Consortium can be found on the Appendix. This section
describes the current legislation framework with regard to PV
and storage integration in buildings, as well as the specific
NZEB definition per participating country.
• Greece. Owners of small-scale rooftop PV installations
can select between three subsiding policies, depending
on PV system capacity: a) Feed-in tariff (FiT)
programme for rooftop PVs of capacities lower than 10
kWp, referring to buildings used for households and
small businesses, b) net-metering compensation policy
with annual netting of produced and generated energy,
for PV installations with a capacity up to 500 kWp
[10], and c) virtual net-metering scheme, in which
generation and consumption installations can be
located in different places that belong to the same
owner. In this case, eligible owners are only public
authorities, social enterprises, education institutions
and farmers [11]. Considering ESS, storage installation
is currently permitted only for large-scale hybrid RES
applications in islands. Finally, a clear definition of an
NZEB is not yet included in the national legislation.
• Cyprus: PV installations of up to 5 kWp are eligible for
net-metering scheme, while an additional subsidy is
offered to vulnerable customers [12]. Industrial and
commercial owners of medium and large PVs can select
the self-consumption scheme. In the latter scheme, the
use of storage can lead to an increase of the maximum
allowable PV system capacity [12]. For a building to be
characterized as NZEB, the following basic criteria
should be fulfilled [13]: a) the energy efficiency should
be of Class A, b) 25 % of total consumption should be
derived from RES, and c) the maximum consumption
expressed as primary energy should be: i) 100
kWh/m
2
/year for residential buildings and ii) 125
kWh/m
2
/year for non-residential buildings.
• FYROM: Eligible PV owners receive a FiT via a power
purchase agreement with the market operator. Each
producer must submit production schedules and is
financially responsible for any deviations [14], [15].
The NZEB definition has not been incorporated into the
national legislation.
• Bulgaria: Small-scale PV installations are distinguished
according to their capacity when participating on the
current compensation policy. Two different FiTs are
available for PVs up to 5 kWp and for PVs from 5 kWp
up to 30 kWp, with a compensation limit at the total
yearly produced energy. Additionally, there is no
legislative framework for storage integration in
buildings. Finally, a building is characterized as NZEB
if the following two conditions are satisfied: a) Primary
energy consumption needs to meet energy efficiency of
Class A, and b) at least 55% from the energy
consumption must be produced by on-site or near the
building RES.
III. O
VERVIEW OF
Τ
ΗΕ
PV-ESTIA
P
ROJECT
The primary target of the PV-ESTIA project is to enhance
the integration of PVs and ESSs in the building environment,
facilitating in this way the transition towards the NZEB
concept. Specifically, the objective is to transform buildings
into a controllable energy source by proposing an innovative
management scheme of the hybrid PV-storage system. Within
the project an online user-friendly tool will be developed,
aiming to empower stakeholders and engineers to adequately
deal with this new type of system. Additionally, new joint
regulations and recommendations for the Balkan-Med region
will be proposed, paving the way for further integration of PV
and ESSs in buildings. Specifically, potential barriers that
appear on transnational level will be tackled using tools and
experience acquired on national level, giving more attention to
the specific needs and special characteristics of each separate
country. The outcome will contribute to understanding the
existing situation, creating in practice viable solutions that can
be widely applied, and producing regulation and policy
recommendations.
To achieve the above-mentioned targets, the following
tasks will be implemented in the framework of the PV-ESTIA
project: Initially, existing policies and regulatory frameworks
will be analyzed to identify potential barriers tackling the
integration of PVs and ESSs in the building stock. Afterwards,
a management scheme of hybrid PV-storage systems will be
developed to facilitate the integration of ESSs in the building
environment. Subsequently, online optimization tools will be
developed to investigate potential solutions for the identified
barriers as well as to evaluate the performance of the proposed
scheme under different electricity pricing policies, e.g. FiTs,
feed-in premium (FiP), net-metering, climatological conditions
and technical constraints. Finally, in the framework of the
project, pilot installations will be developed to optimally
calibrate the control parameters of the proposed scheme and to
thoroughly validate its performance under real-field conditions.
IV. P
ROPOSED
I
NNOVATIVE
M
ANAGEMENT
S
CHEME
The proposed scheme provides a new energy management
solution for residential and commercial buildings, taking into
consideration potential interactions with the electrical grid.
This is attained by exploiting the flexibility added to the energy
management of the building when investing in technologies
related to the use of ESSs, demand response techniques, and
smart management methods of cooling and thermal loads. In
Fig. 1, the conceptual design of the innovative management
scheme (IMS) is presented. As shown, the proposed IMS
requires two distinct groups of input data. The first group is
related to the in-house energy needs of the building, which can
be met using electricity or primary energy sources, e.g. natural
gas, biomass, etc. On the other hand, the second group of input
data includes the technical limitations posed by the DSOs
regarding the permissible voltage limits at the point of common
coupling (PCC), as well as the use of different electricity
pricing policies, such as the time of use (ToU) tariffs.
Scope of the developed IMS is to meet the energy needs of
the building in an optimal way by exploiting all the available
resources, while also satisfying the technical requirements
introduced by the local DSO. Although various objectives can
be considered in the proposed IMS, the most important one is
the maximization of the self-consumption rate (SCR) of the
building. Considering the economic point of view, another
alternative objective is the maximization of the net present
value of the above-mentioned investment. The main output of
the developed strategy consists of a unified and coordinated
management scheme, which optimally controls the ESS
operation, as well as the electrical, thermal, and cooling loads
of the building.
Furthermore, the proposed method includes the following
distinct functionalities:
• Peak load shaving. This is considered as an important
ancillary service provided to the local DSO to ensure
the safe and reliable network operation during
contingency periods.
Fig. 1. Conceptual design of the innovative management
scheme.
• Voltage and frequency support. Currently, prosumers
are obliged to implement specific control schemes for
voltage and frequency support according to the local
grid connection requirements. Considering European
countries, the basic guidelines are contained in the
Standard EN50160 and in the national grid codes for the
interconnection of distributed generation [16].
• Support dc or ac grid-tie operation. The proposed IMS
method is flexible by means of allowing different
configurations regarding the connection of the ESS,
namely ac-coupled or dc-coupled.
• Support different electricity pricing policies. The
proposed method foresees the use of different electricity
pricing policies, e.g. FiTs, FiP, net-metering policies,
etc.
• Back-up operation. Finally, in case of a sudden network
blackout, the proposed IMS method offers the ability of
short-term operation of the building by exploiting the
stored electrical energy of the ESS.
V. P
ERFORMANCE
E
VALUATION VIA
P
ILOTS
In the framework of the PV-ESTIA project, the
performance of the proposed IMS will be thoroughly evaluated
under real-field conditions. Towards this objective, two groups
of pilot installations are foreseen. The first group includes the
full implementation of the proposed IMS by installing ESSs in
buildings with existing or new PV installations. On the other
Network technical
constraints
ESS
PV
Thermal / Cooling
Energy
Electrical Energy
Building Needs
Pow er
Supply
Thermal
Supply
Electricity pricing
policy, e.g. ToU
Utility Features
IMS
hand, in the second group, measurement devices will be
installed on existing prosumers and consumers to create a
portfolio of typical consumption and generation profiles in the
Balkan-Med area.
A. First Group of Pilots
The detailed list of the pilot installations is presented
below:
• Thessaloniki. The research committee building of the
Aristotle University of Thessaloniki has been selected
as the most appropriate pilot site for the installation of
both 15 kWp PV system and 15 kWh ESS. This
building is equipped with a building energy
management system (BEMS), thus allowing the full
implementation and evaluation of the proposed IMS.
• Kozani. In this pilot site, a 20 kWh ESS will be
additionally installed to the existing 20 kWp PV
installation. The pilot site is located at the dormitories
building of the Western Macedonia University οf
Applied Sciences. This field trial has been selected to
investigate the performance of the IMS in large
buildings operating 24/7.
• Nicosia. Six ESSs with a nominal capacity of 7 kWh
will be installed in five different prosumers with
existing PV installations to evaluate the performance of
the developed management scheme in small scale
installations. Additionally, a 20 kWh ESS will be added
to the existing PV installation in the municipality
building of Nicosia to assess the effect that different
geographical conditions may have on the performance
of the proposed method.
• Plovdiv. Five prosumers will be selected for installing
an ESS with a nominal capacity of 7 kWh to validate
the performance of the proposed IMS.
• Skopje: Finally, a 7 kWh ESS will be established on the
main building of the University of Skopje.
The above-mentioned pilot installations have been carefully
selected to examine if and how the size of ESS and the
different geographical conditions affect the performance of the
proposed innovative management scheme.
B. Second Group of Pilots
The second group of pilots includes the installation of
Smart meters in prosumers and consumers installations located
at the cities of Thessaloniki, Kozani, and Skopje. More
specifically, measurement data will be acquired continuously
for a period of at least one year and an exhaustive statistical
analysis will be performed to derive typical consumption and
generation profiles for the Balkan-Med region.
C. Pilot Specifications
The first step towards the implementation of the pilot
installations is the proper selection of the pilot sites. Therefore,
the prosumers participating in the pilots will be selected based
on the following criteria: a) space sufficiency, b) proper
ventilation, c) new or existing PV systems, and d) balanced
production and consumption.
Considering the combined PV and ESS operation, two possible
configurations can be used, namely the ac-coupled and dc-
coupled system, as shown in Fig. 2 and Fig. 3, respectively. In
the ac-coupled ESS system, a battery converter is employed to
connect the battery to the ac side of the PV inverter. Therefore,
this configuration can be readily applied to existing PV
Fig. 2. Schematic diagram of an ac-coupled system.
Fig. 3. Schematic diagram of a dc-coupled hybrid system.
installations due to its modular structure, but it is not preferred
in cases of limited available space. On the other hand, in the
dc-coupled ESS system, the battery is connected to the
common dc-bus of the PV converter, thus presenting a higher
round trip efficiency due to the use of fewer components.
However, this approach offers limited expandability.
The type of the battery technology is a crucial factor for
the implementation of the proposed IMS. The most promising
battery technologies include the nickel-cadmium & lead-acid
and lithium-ion batteries. Among them, lithium-ion batteries
are more compatible with PV installations, but they present
higher cost and increased sensitivity to temperature compared
to
lithium-ion batteries. As a result, both types of batteries will be
used in the pilot installations to assess to what extent the
battery technology affects the performance of the proposed
IMS.
Battery converter
+
-
DC/AC
DC/AC
DC/DC
DC/DC
Grid
PV inverter Common AC-bus
Battery
PV panel
Building
Load
+
-
DC/DC
DC/DC
Grid
Hybrid PV con verter
Common
DC-bus
Battery
PV panel
Building
Load
DC/AC
VI. P
ERFORMANCE
E
VALUATION VIA
O
PTIMIZATION
T
OOL
To evaluate several energy management schemes, building
configurations, and network topologies, an online optimization
tool will be developed. Climatological conditions such as
temperature and irradiation as well as the electrical, thermal,
and cooling needs of the building will be imported as inputs to
the developed optimization tool. Additionally, the thermal or
cooling loads of the buildings, the electrical load, and the ESS
will be properly controlled according to the IMS of Fig. 1 to
meet the energy needs of building, while also maximizing its
self-consumption rate. Additionally, the developed
optimization tool will evaluate different electricity pricing
policies, e.g. FiTs, FiP, etc. Finally, another feature of the
online optimization tool will be the evaluation of the ESS and
PV system viability by calculating the payback period of the
investment.
VII. E
XPECTED
O
UTPUTS AND
C
ONCLUSIONS
The proposed innovative management scheme will be
installed at selected small and large buildings in each pilot
country to assess the performance of the ESS in terms of
maximizing the self-consumption rate. Additionally, problems
related to the secure and reliable operation of the grid, as well
as the ESS utilization will be effectively addressed to enhance
the resilience of the energy system.
The pilot installations are expected to be completed within
the second quarter of 2018. Furthermore, possible scenarios
that consider ESS as a promising solution will be shared with
among all participating stakeholders, i.e., DSOs and policy
makers. This will encourage the adoption of new policies and
technical regulations for the promotion of higher PV share in
the energy mix and will pave a novel way towards structuring a
resilient energy system.
A
PPENDIX
This project has been approved for funding by the Interreg
BALKAN-MED programme of the European Commission. It
will be implemented by a Consortium consisting of seven (7)
partners, based in four (4) different EU countries, as shown in
Table I.
TABLE I. P
ARTNERS OF THE
PV-ESTIA
PROJECT
P1 Aristotle University of Thessaloniki, Greece
P2 Technological Research Centre of Western Macedonia,
Greece
P3 University of Cyprus, Cyprus
P4 Electricity Authority of Cyprus, Cyprus
P5 Energy Agency of Plovdiv, Bulgaria
P6
Faculty of Electrical Engineering and Information
Technologies of SS. Cyril and Methodius University in
Skopje, FYROM
P7 Ministry of Environment and Energy/Directorate of
Renewable Energy Sources and Electricity, Greece
R
EFERENCES
[1] European Union, On the Energy Performance of Buildings. Directive
2010/31/EU of the European Parliament and of the Council (recast),
Official Journal of the European Communities, Brussels, May 2010.
[2] European Commission, “Green Paper: A 2030 climate & energy
framework”, Communication COM(2013) 169, 27/03/2013.
[3] R. Tonkoski, D. Turcotte, and T. H. M. El-Fouly, "Impact of high PV
penetration on voltage profiles in residential neighborhoods," IEEE
Trans. Sustain. Energy, vol. 3, no. 3, pp. 518–527, 2012.
[4] T. Sansawatt, L. F. Ochoa, and G. P. Harrison, “Smart decentralized
control of DG for voltage and thermal constraint management,” IEEE
Trans. Power Syst., vol. 27, no. 3, pp. 1637–1645, Aug. 2012.
[5] R. A. Walling, R. Saint, R. C. Dugan, J. Burke, and L. A. Kojovic,
“Summary of distributed resources impact on power delivery systems,”
IEEE Trans. Power Del., vol. 23, no. 3, pp. 1636–1644, 2008.
[6] P. D. Lund, J. Lindgren, J. Mikkola, and J. Salpakari, “Review of energy
system flexibility measures to enable high levels of variable renewable
electricity,” Renew. Sustain. Energy Rev., vol. 45, pp. 785–807, 2015.
[7] R. Luthander, J. Widén, D. Nilsson, and J. Palm, “Photovoltaic self-
consumption in buildings: A review,” Appl. Energy, vol. 142, pp. 80-94,
2015.
[8] J. Moshövel, et. al., “Analysis of the maximal possible grid relief from
PV-peak-power impacts by using storage systems for increased self-
consumption,” Appl. Energy, vol. 137, pp. 567–575, 2015.
[9] A. I. Nousdilis, A. I. Ch rysochos, G. K. Papagiannis, and G. C.
Christoforidis, “The impact of photovoltaic self-consumption rate on
voltage levels in LV distribution grids,” in Proc. Int. Conf. Comp.,
Power Electron. Power Eng. (CPE-POWERENG), April 2017.
[10] G. C. Christoforidis, I. P. Panapakidis, T. A. Papadopoulos, G. K.
Papagiannis, I. Koumparou, M. Hadjipanayi, G. E. Georghiou, "A
Model for the Assessment of Different Net-Metering Policies,"
Energies, vol. 9, no. 4, pp. 262, 2016.
[11] Official Gazette 1547/2017 of Greece, “Installation of PV stations by
self-producers applying net-metering or virtual net-metering
compensation, according to article 14A of Official Gazette 3468/2006,”
2017.
[12] Ministry of Energy, Commerce, Industry and Tourism Cyprus (MECIT),
“Solar Energy for All,” 2016.
[13] D.K. Serghides, M. Michaelidou, M. Christofi, S. Dimitriou, M.
Katafygiotou, “Energy Refurbishment Towards Nearly Zero Energy
Multi-family Houses, for Cyprus,” Procedia Environmental Sciences,
vol. 38, pp. 11-19, 2017.
[14] Official Gazette of FYROM No. 56/2013
[15] https://www.energy-
community.org/implementation/FYR_Macedonia/RE.html
[16] Voltage characteristics of electricity supplied by public distribution
networks, Standard EN 50160:2010.
