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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,
Georgios C. Christoforidis, Aggelos S. Bouhouras
Western Macedonia University of Applied Sciences, Kozani, Greece,
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
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
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
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
/year for residential buildings and ii) 125
/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.
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
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.
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
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,
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
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
Thermal / Cooling
Electrical Energy
Building Needs
Pow er
Electricity pricing
policy, e.g. ToU
Utility Features
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
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
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
Battery converter
PV inverter Common AC-bus
PV panel
Hybrid PV con verter
PV panel
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
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.
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.
P1 Aristotle University of Thessaloniki, Greece
P2 Technological Research Centre of Western Macedonia,
P3 University of Cyprus, Cyprus
P4 Electricity Authority of Cyprus, Cyprus
P5 Energy Agency of Plovdiv, Bulgaria
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
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framework”, Communication COM(2013) 169, 27/03/2013.
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penetration on voltage profiles in residential neighborhoods," IEEE
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The European Union’s energy and climate policies are geared on reducing carbon dioxide emissions and advancing sustainable energy, focusing on a faster propagation of renewable energy sources to decarbonize the energy sector. The management of locally produced energy, which can be implemented by a microgrid capable of either being linked to the main grid or operating independently, is equally crucial. Additionally, it seems that electricity storage is the only practical way to manage energy effectively within a microgrid. Energy storage is hence one of the main technological parameters upon which future energy management has to be based. Especially during crisis periods (such as the COVID-19 pandemic or the ongoing energy crisis), storage is a valuable tool to optimize energy management, particularly from renewables, in order to successfully cover demand fluctuation, hence achieving resilience, while at the same time reducing overall energy costs. The purpose of the paper is to analyze and present, in brief, the state-of-the-art of the energy storage systems that are available on the market and discuss the upcoming technological improvements of the storage systems and, in particular, of batteries. The analysis will focus on the storage systems that can be used within a stand-alone community such as a microgrid, but not limited to it. In the analysis, short- and long-term storage options are discussed, as well as varying storage capacities of the different technologies. The analysis is based on contemporary optimization tools and methods used for standalone communities. Understanding the state-of-the-art of energy storage technology is crucial in order to achieve optimum solutions and will form the base for any further research.
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Decarbonizing the building stock is of utmost importance for achieving sustainability as buildings are holding an important role for the clean energy transition. In this paper, the impact on the electrical consumption and building related CO2 emissions are analysed through real measurements by taking the effect from the implementation PV plus battery energy storage hybrids within 5 residential buildings in Plovdiv area. Increased self-sufficiency rates are quantified for a period of 3 years under pure self-consumption mode, where no power sells are taking place. Indicators such as monthly and yearly self-sufficiency rates with and without storage are compared. Building`s related CO2 avoidance are also compared in two scenarios-with and without battery energy storage system.
The current climate and energy policies of the European Union aim at achieving carbon dioxide emissions reduction and the promotion of clean energy. The priorities set concentrate on decarbonizing the energy sector, mainly by promoting renewables. At the same time, it is of great importance to effectively manage the energy generated in-situ within a community. That community can be approached as a micro-grid able either to be connected to the main grid or to be independent. In addition to this, storage of electricity seems the unavoidable solution for the effective energy management with the micro-grid. Due to the technological developments and the reduction in production costs that are expected to decrease even further in the coming years (50% reduction), batteries are a crucial factor for the effective integration of renewables on a residential scale. Thereafter, the proper size of a battery system plays an important role for the total minimization of system's cost during its lifetime. The purpose of the paper is to present a mathematical tool, able to manage the energy produced by residential photovoltaic panels, the energy stored in the batteries and the energy purchased from the main grid. Continuing with the energy management, the framework should come up with an optimized life cycle cost solution, regarding both the energy management within the grid and the optimum size of energy battery system. Main findings of the paper indicate that storage is a feasible option, whenever selling electricity to the main grid is not applicable, as for that case the battery capital cost should decrease to 400 (€/kWh); this is a 20% cost reduction compared to current prices and 30 (€/kWh).
Electricity demand for building-related activities is steadily increasing due to urbanization. Combined with the increasing penetration of renewable energy, this trend brings new challenges to distribution network operators in maintaining nodal voltage and minimizing active power losses. At the same time, building operators require more effective methods of reducing building operational costs. Therefore, as a critical step towards smart cities, it is imperative to optimally manage and coordinate the resources across building and power distribution networks to improve the overall system's efficiency and reliability. To this end, this paper develops a novel framework for Buildings-to-Distribution-Network (B2DN) integration. The framework couples commercial, residential buildings, and DERs, including photovoltaic (PV) generation and battery energy storage systems (BESS), with the power distribution network, enabling buildings and the distribution networks to be optimized simultaneously while respecting both building and distribution network constraints. The proposed B2DN framework is implemented in a receding horizon manner by solving a quadratically constrained quadratic programming (QCQP) problem. The framework’s capabilities are demonstrated on the IEEE 13-, 33-, and SB 129-node distribution networks integrated with 90, 192, and 481 buildings and DERs. The simulation results reveal that the B2DN controller successfully minimizes distribution network active power losses and enhances voltage regulation while at the same time minimizing building energy costs and maintaining occupant's comfort in comparison with decoupled designs, where buildings and distribution networks are independently managed. Finally, uncertainty analysis shows a minimal decrease in the B2DN controller's performance in the presence of randomness in weather variables, building internal heat gains, and distribution network nodal base demands.
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Building microgrids have emerged as an advantageous alternative for tackling environmental issues while enhancing the electricity distribution system. However, uncertainties in power generation, electricity prices and power consumption, along with stringent requirements concerning power quality restrain the wider development of building microgrids. This is due to the complexity of designing a reliable and robust energy management system. Within this context, hierarchical control has proved suitable for handling different requirements simultaneously so that it can satisfactorily adapt to building environments. In this paper, a comprehensive literature review of the main hierarchical control algorithms for building microgrids is discussed and compared, emphasising their most important strengths and weaknesses. Accordingly, a detailed explanation of the primary, secondary and tertiary levels is presented, highlighting the role of each control layer in adapting building microgrids to current and future electrical grid structures. Finally, some insights for forthcoming building prosumers are outlined, identifying certain barriers when dealing with building microgrid communities.
Conference Paper
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Photovoltaic systems are increasingly integrated into the low voltage (LV) distribution grid and are particularly installed on buildings. This trend is expected to continue in the following years as new buildings should be Nearly Zero Energy ones that will necessarily incorporate renewables. This situation has already started to produce significant challenges to distribution system operators, such as overvoltages, reverse power flows, etc. There are several methods proposed in the literature to mitigate the overvoltage issues caused by high Photovoltaics (PV) integration and Renewable Energy Sources (RES) intermittency. In this work, we contribute to the existing literature by investigating the impact of the Self-Consumption Rate (SCR) on the voltage quality of LV radial networks. The SCR is an indicator of the amount of energy produced which is directly consumed on-site. This paper uses a benchmark IEEE LV feeder and randomized load profiles, and performs various simulations to find out how the SCR of the prosumers affect the voltage quality in a LV feeder. Results show that there is a marginal SCR value for a certain feeder, above which no overvoltages are observed. However, this is feeder-sensitive and strongly depends on feeder parameters.
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Following Europe's 20:20:20 objective, this case study investigates refurbishment scenarios in order to achieve Nearly Zero Energy houses, in Cyprus. The study investigates amongst other aspects of the European recast, two approaches that will be decisive for the development of the building sector in Cyprus: The measures and techniques to be implemented in order to achieve nearly Zero Energy Houses (nZEB) in Cyprus and the analysis of cost optimisation. The research focuses on the Multi-Family House typology as classified in the framework of EU project EPISCOPE. The building was modelled using the official governmental software iSBEM_cy tool, according to the European Directives 2002/91/EC and 2010/31/EC. The aim was to upgrade it into a nearly Zero Energy Building (nZEB) by investigating the effectiveness of the energy refurbishment both in terms of energy savings and payback period. Two scenarios were developed in order to evaluate the energy efficiency and the cost effectiveness of the conservation measures. Through analysis of the results, the efficiency of each strategy and technique employed towards minimising the energy consumption and the greenhouse gas emissions was evaluated, in terms also of its cost effectiveness. Furthermore, the results of the research were investigated in order to assess whether the nZEB requirements, as developed by the MECIT, are appropriate for the existing Multi-Family houses in Cyprus and whether alternative strategies may be employed in order to meet the target of nZEB and to reduce effectively the energy consumption and the CO2 emissions.
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The photovoltaic market has recently experienced an enormous expansion, mainly due to the generous Feed-in-Tariffs (FiTs) adopted by many countries. However, in the recent years FiTs have been considerably reduced or even disappeared as their role in the PV deployment has ended. One of the alternatives is the Net-Metering (NEM) policy, which has attracted the interest of stakeholders as it provides a basis for the efficient collaboration between generation and the consumption profiles of the consumer. Currently, there is a lack of a universal policy harmonizing the respective legislations of the E.U. member countries. This paper proposes a novel generalized methodology for the techno-economic assessment of different NEM policies in terms of profitability for the prosumer. The methodology is tested in a formulated case study based on the current NEM policy in Greece. The method proposed uses as inputs the averaged load profiles constructed from real measurements collected from 31 consumers in the Thessaloniki area and evaluated PV production. The current NEM policy and four alternatives are examined, using as additional input the average system marginal prices of the year 2013. The results show that the proposed methodology is capable of evaluating a wide variety of NEM policies and can lead to suggestions for policy adaptation in order to establish a win-win contract between all interested stakeholders.
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Active Network Management schemes are being developed to accommodate larger volumes of renewable generation within distribution networks. Approaches typically manage only single technical constraints or are highly complex with extensive sensing and communications needs that bring cost, deployment, and operational risks. This work offers an alternative, decentralized approach for real-time management of local voltage and thermal constraints that avoids extensive sensing and communications. It controls generator active and reactive power output to overcome voltage and thermal issues near the point of connection. Results from time-series analyses reveal its effectiveness in managing both constraints and allowing greater production. It represents a potentially effective and fast-to-deploy alternative to more complex, integrated solutions.
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The objective of this paper is to provide an assessment on voltage profiles in residential neighborhoods in the presence of photovoltaic (PV) systems. The network was modeled in PSCAD using common feeder characteristics that Canadian system planners use in suburban residential regions. A simulation study was performed to investigate potential voltage rise issues in the network up to 11.25% total PV penetration in the feeder and LV transformer capacity penetration up to 75%. Results indicate that the PV penetration level should not adversely impact the voltage on the grid when the distributed PV resources do not exceed 2.5 kW per household on average on a typical distribution grid. Moreover, the role of feeder impedance, feeder length, and the transformer short circuit resistance in the determination of the voltage rise is quantified.
The paper reviews different approaches, technologies, and strategies to manage large-scale schemes of variable renewable electricity such as solar and wind power. We consider both supply and demand side measures. In addition to presenting energy system flexibility measures, their importance to renewable electricity is discussed. The flexibility measures available range from traditional ones such as grid extension or pumped hydro storage to more advanced strategies such as demand side management and demand side linked approaches, e.g. the use of electric vehicles for storing excess electricity, but also providing grid support services. Advanced batteries may offer new solutions in the future, though the high costs associated with batteries may restrict their use to smaller scale applications. Different “P2Y”-type of strategies, where P stands for surplus renewable power and Y for the energy form or energy service to which this excess in converted to, e.g. thermal energy, hydrogen, gas or mobility are receiving much attention as potential flexibility solutions, making use of the energy system as a whole. To “functionalize” or to assess the value of the various energy system flexibility measures, these need often be put into an electricity/energy market or utility service context. Summarizing, the outlook for managing large amounts of RE power in terms of options available seems to be promising.
The interest in self-consumption of PV electricity from grid-connected residential systems is increasing among PV system owners and in the scientific community. Self-consumption can be defined as the share of the total PV production directly consumed by the PV system owner. With decreased subsidies for PV electricity in several countries, increased self-consumption could raise the profit of PV systems and lower the stress on the electricity distribution grid. This review paper summarizes existing research on PV self-consumption and options to improve it. Two options for increased self-consumption are included, namely energy storage and load management, also called demand side management (DSM). Most of the papers examine PV-battery systems, sometimes combined with DSM. The results show that it is possible to increase the relative self-consumption by 13–24% points with a battery storage capacity of 0.5–1 kW h per installed kW PV power and between 2% and 15% points with DSM, both compared to the original rate of self-consumption. The total number of papers is however rather limited and further research and more comparative studies are needed to give a comprehensive view of the technologies and their potential. Behavioral responses to PV self-consumption and the impact on the distribution grid also need to be further studied.
For future energy supply systems the effects and benefits of battery storage systems in households with photovoltaic (PV) generators and the effects on distribution and transmission grids need to be identified and analyzed. The development of grid relieving management strategies for the storage system in due consideration of self-consumption is a necessary step forward in order to analyze the potential of private home battery storage systems to reduce stress on the power supply system. A MATLAB-based model of a lithium-ion storage system has been developed. The model is applicable for a wide range of PV generator sizes, different battery storage systems and diverse management strategies. In order to identify the potential of grid relieving forecast strategies, without discharging the storage into the grid, a management strategy based on persistence forecasts of solar radiation and household load demand has been implemented and analyzed. To minimize forecast uncertainties a proportional plus integral controller has been developed. The persistence forecast management strategy is applicable in real-life PV-battery-systems and due to the simple forecast it is easy to equip existing systems with such a management system with only low effort. As a result it will be shown that a storage system management based on forecasts has a significantly higher potential to relieve the grid than a system that only maximizes self-consumption as it is usually used nowadays. Besides, such a management strategy is able to unload the grid more than a static power reduction to 70% of the nominal power rating according to the current German Renewable Energy Sources Act (EEG). At the same time, the self-consumption can be retained at nearly the same level as by using a management strategy to purely maximize the self-consumption. Even less energy is wasted then with the feed-in limitation. See:
Because traditional electric power distribution systems have been designed assuming the primary substation is the sole source of power and short-circuit capacity, DR interconnection results in operating situations that do not occur in a conventional system. This paper discusses several system issues which may be encountered as DR penetrates into distribution systems. The voltage issues covered are the DR impact on system voltage, interaction of DR and capacitor operations, and interaction of DR and voltage regulator and LTC operations. Protection issues include fuse coordination, feeding faults after utility protection opens, impact of DR on interrupting rating of devices, faults on adjacent feeders, fault detection, ground source impacts, single phase interruption on three phase line, recloser coordination and conductor burndown. Loss of power grid is also discussed, including vulnerability and overvoltages due to islanding and coordination with reclosing. Also covered separately are system restoration and network issues.
On the Energy Performance of Buildings. Directive 2010/31/EU of the European Parliament and of the Council (recast)
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.