Georgios C Christoforidis

University of Western Macedonia | UOWM · Department of Electrical and Computer Engineering

The participation of photovoltaic (PV) power into the energy market requires the development of accurate forecasting models to alleviate the imbalance penalties and ensure the viability of the investments. Several forecasting models have been proposed, focusing on different forecasting horizons. However, their implementation does not consider the e...

In this paper, the harmonic distortion (HD) of the 3rd, 5th and 7th harmonic currents is utilized along with other common electrical features that commercially available smart electrical energy meters could extract from the main feeding panel of a household’s electrical installation. A two-stage event-driven end-cloud Support Vector Machine (SVM) N...

DC microgrids are exposed to diverse disturbances that can cause DC bus voltage instability and power quality issues. Renewable volatility and fault occurrence on the power lines are considered as high-impact variations, which jeopardize the resilience of the microgrid. Therefore, the deployment of a battery storage system can improve the robust op...

Employment of properly controlled energy storage technologies can improve power systems’ resilience and cost-effective operation. However, none of the existing storage types can respond optimally under all circumstances. In fact, the performance of a standalone storage solution is limited mainly by its energy and power density, response speed, life...

The integration of Photovoltaic (PV) power into energy market requires the development of accurate PV power forecasting models. Apart from the prediction model the selection of the proper optimizer may contribute towards the forecasting accuracy increment. At this paper, we propose a hybrid Adam-Unified Particle Swarm Optimization (UPSO) optimizer...

In this paper, the economic viability of PV-battery systems integrated in pubic buildings is assessed, considering the various financial parameters met in countries of the Mediterranean region, such as systems cost and electricity tariffs. Specifically, a detailed techno-economic model that takes into consideration the flexibility of building loads...

n this paper, a residential Energy Management System (EMS) for prosumers is presented to schedule optimally the operation of both the schedulable appliances and the Battery Energy Storage System (BESS). The target of this model is the minimization of the electricity cost and the reduction of both the imported and exported power peaks. Through this...

This article is a narrative and systematic review on the electromagnetic optimization literature of superconducting solenoidal magnets and coils. Superconducting solenoids are the basis of magnetic resonance imaging machines and superconducting energy storage systems. As the literature has evolved and many optimization techniques have been used, in...

The energy storage systems are considered the prime candidates to increase the stability and penetration of renewable energy sources. However, their cost and reliability may prove to be significant obstacles for their development. A solution that is gaining momentum and can augment performance and reduce costs is hybrid energy storage systems (H-ES...

Employment of a battery energy storage system to compensate for the generation-consumption mismatch is a vital element for a resilient microgrid. However, the frequent (i.e., short-term) cyclic activity and the abrupt current variations (i.e., high di/dt) have adverse effects on the energy-type battery’s lifespan. On the other hand, the power-type...

Here, an efficient Energy Management System (EMS) for residential installations is proposed. The EMS handles on site Photovoltaic (PV) power production along with Battery Energy Storage System (BESS) and performs load shifting under a Demand Side Management (DSM) scheme that considers user comfort. The goal of the proposed methodology is the minimi...

This paper presents the methodology followed for the thermal and electromagnetic design of a superconducting coil at the University of Western Macedonia, aimed to be used in a unique SMES system for laboratory education and research purposes. Firstly, we discuss the design constraints of the coil and select its dimensions using both electromagnetic...

In this paper the problem of congestion management in the power grid under the application of the day-ahead dispatch schedule, is faced based on developing a day-ahead guideline regarding the required modifications to the power units’ output to yield a more uniform loading to the grid’s lines. These modifications result by comparing the dispatch sc...

The increased installation of photovoltaic (PV) systems raises the necessity for the development of Digital Twins (DT), in order to simulate the PV power output and ensure the normal operation of the systems. To this point, at the present paper we propose a data-driven DT based on a hybrid ensemble FFNN-LSTM model. To examine the efficiency of the...

This paper focuses on the initial testing, by using a DC variable load, of the laboratory scale Superconducting Magnetic Energy Storage (SMES) system developed in the University of Western Macedonia. The SMES is built using a single-pancake coil (SPC) made of 12mm YBCO tape. It is cooled to 40 K using a cryocooler. The objective is to utilize the c...

In this paper, the harmonic distortion (HD) of the 3rd, 5th, and 7th harmonic currents is utilized in order to improve the load identification performance in addition to common electrical features that are usually applied in NILM applications. The evaluation of the proposed feature employment is achieved under a multi-label consideration through a...

Energy Management Systems (EMSs) have gained significant attention over the last years, considering the integration of Renewable Energy Sources and the flexibility provided by the storage systems and the schedulable household appliances. In this paper a residential EMS with two different approaches is proposed. The formulation of the first and the...

The increased installation of photovoltaic (PV) systems has triggered several issues in power systems, due to their intermittent nature. Therefore, the development of accurate day-ahead PV generation forecasting models is vital to overcome planning and dispatching issues. The present paper presents a day-ahead PV energy forecasting model based on T...

Resilient operation of DC microgrids is seriously endangered by the unpredictable and volatile renewable generation, arbitrary load variations and unplanned disconnections from the utility grid. These instabilities can cause DC bus voltage fluctuations and significant power quality issues. Therefore, employing a robust, quick-responsive energy stor...

Nowadays, there is a growing need to increase the penetration of distributed renewable energy sources (DRESs) in electrical distribution grids in an attempt to decarbonize the energy sector. Nevertheless, the intermittent nature of DRESs introduces several challenges towards the secure and reliable operation of distribution grids, and especially of...

European Union’s target to achieve climate neutrality until 2050, along with the increase in energy costs, boosted the interest on improving energy efficiency (EE) in companies and especially in the small and medium-sized enterprises (SMEs). The SMEmPower Efficiency project, a HORIZON 2020 funded project, aims to address this issue by proposing a o...

This paper presents two Optimization Schemes (OS) formulated under respective objective functions aiming to exploit the Photovoltaic and Battery Energy Storage Systems (BESS) in installations with Demand Side Management. The first one is locally applied within the prosumer installation to minimize electricity cost, while the second one is centrally...

This paper presents the methodology and the implementation of the monitoring and targeting (M&T) and monitoring and verification (M&V) tools that were developed in the context of the SMEmPower Efficiency Horizon 2020 project. The tools were built to allow energy managers and energy experts of Small and Medium Enterprises (SMEs) to store and organiz...

Robust operation of DC microgrids is seriously jeopardized by renewable energy sources fluctuations and intermittency, abrupt load changes and unscheduled disconnections from the utility grid. These disturbances can cause DC bus voltage instability and power quality issues. Therefore, utilization of properly controlled energy storage systems, plays...

In order to ensure the viability of Photovoltaic (PV) systems' installation, several Operation and Maintenance (O&M) strategies are followed, such as preventive, corrective and predictive maintenance. Even if these strategies can indirectly increase the profitability of PV systems, none of them deal with the actions that should be followed when mul...

In this paper, a sizing method is proposed for Photovoltaic (PV) and Battery Energy Storage Systems (BESS) for buildings with Demand Side Management capability. Three objective functions (OF) are defined, describing the Self-Sufficiency of the building, the Net-Present Value of the investment in PV and BESS, and their combination in a joint express...

Smart Home Energy Management Systems can manifest energy consumption reduction targets in the residential sector and can be viewed as an approach to transform the consumer into an active prosumer. The present paper presents a smart home energy management system that includes flexible appliances, electric vehicles, and energy storage units. Efficien...

The largest parts of energy demand within the residential sector are used for space heating (SH), domestic hot water (DHW) and space cooling (SC). The thermal and electrical needs can be mainly covered by energy systems that consist of Photovoltaics (PVs), solar thermal collectors (STCs), heat pumps (HPs) and flexibility sources, e.g. battery energ...

This paper deals with the problem of energy losses in Distribution Networks (DNs) under Electric Vehicle (EV) penetration. The problem of charging overlaps causing severe power losses and voltage drops is faced under appropriate EV charging. An optimization EV charging schedule is proposed under EV time-of-arrival consideration. The solution algori...

In this paper a sizing tool is proposed for Photovoltaic (PV) and Battery Energy Storage Systems (BESS) in installations with Demand Side Management capability. Three objectives functions are defined, describing the Self-Sufficiency Rate, the Net-Present Value of the investment in PV and BESS, and their combination in a joint expression, respective...

The development of robust photovoltaic (PV) power forecasting models is essential for the secure and economic integration of PV power into the intra-day and day-ahead energy markets. Since the day-ahead solar power forecasting is a more challenging procedure, at the present paper a Deep Learning approach and more specifically the Long-Short Term Me...

A key component in superconducting magnetic energy storage (SMES) system design is the cooling system. A well-designed cooling apparatus allows a SMES to work with higher critical currents, have less AC losses and work in a stable way. Acknowledging the importance of cooling systems in a SMES and that there have been many different designs presente...

In this paper, an unsupervised non-intrusive load monitoring approach is proposed in order to encounter the disaggregation problem for Non-Intrusive Load Monitoring (NILM) methodologies, using odd harmonic current amplitudes. The problem has been contemplated as a multi-class multi-label one and for the combinations examined the number of appliance...

Superconducting magnetic energy storage systems (SMES) store energy in the form of magnetic field generated by a DC current flowing through a superconducting coil which has been cooled at a low temperature, typically less than 77 K. Therefore, the optimization of the coil and the design of the thermal design are crucial. In this paper the first ste...

Abstract—Integration of Photovoltaics (PV) with Energy Storage Systems (ESS) and Demand Side Management (DSM) is an innovative way that could transform a building into a self-sufficient nanogrid. Such an approach could act as an energy rehabilitation solution and contribute to alleviating the technical problems posed to the electrical grid from hig...

The extensive integration of the large-scale Photovoltaic (PV) plants into the power grid requires the development of new forecasting methods, for the prediction of the PV output with high accuracy. Despite the statistical and the Machine Learning (ML) approaches which have been extensively studied in the literature, the Deep Learning (DL) methods...

This work presents a generic optimization framework based on linear Mixed Integer Programming to assess energy storage options' influence on the operational scheduling and the economic performance of a given power system with high penetration of intermittent renewable energy sources. In particular, three power markets-clearing algorithms with diffe...

The increasing penetration of photovoltaic (PV) systems into the electrical energy systems brings forward several technical and economic issues that mostly relate to their unpredictable nature. A promising solution to many of these is the implementation of robust PV generation forecasting models. In this paper a novel hybrid Ensemble Long Short-Ter...

This work presents an optimization framework based on mixed-integer programming techniques for a smart home’s optimal energy management. In particular, through a cost-minimization objective function, the developed approach determines the optimal day-ahead energy scheduling of all load types that can be either inelastic or can take part in demand re...

In contemporary energy markets, the Retailer acts as the intermediate between the generation and demand sectors. The scope of the Retailer is to maximize its profits by selecting the appropriate procurement mechanism and selling price to the consumers. The wholesale market operation influences the profits since the mix of generation plants determin...

The integration of photovoltaics (PVs) in low-voltage (LV) grids is expected to rise within the following years posing technical challenges to the reliable operation of the electrical system. To tackle these challenges, distributed energy storage systems (ESSs) coupled with PVs at prosumer side arise as a promising solution. Therefore, during the l...

Due to the importance of photovoltaics (PV) generation forecasting in managing the PV output, in contemporary research community various machine learning approaches have been proposed. Deep learning is a sub-category of machine learning where a neural network is composed by more hidden layers, and thus, better training can be accomplished. The topi...

This paper examines how Low Voltage Distribution Networks (DNs) can optimize their voltage profile and minimize their energy losses through the planning ofcharging of Electric Vehicles (EVs).We consider variations concerning the charger and battery capacity of the EVs and we formulate two objective functions. A Particle Swarm Optimization (PSO) alg...

A presentation in the framework of the 3rd webinar organized by the Interreg MED RES Community in the frame of the cycle "Discovering the ETU Toolbox”. Link: https://renewable-energies.interreg-med.eu/news-events/news/detail/actualites/designing-energy-storage-systems-for-residential-photovoltaics-from-stores-project/

Over the last few decades, there is a constantly increasing deployment of solar photovoltaic (PV) systems both at the commercial and residential building sector. However, the steadily growing PV penetration poses several technical problems to electric power systems, mainly related to power quality issues. To this context, the exploitation of energy...

Three load matching indicators (self-consumption rate, self-sufficiency rate, loss of load probability) and the CO 2 emissions were evaluated for 55 Cypriot households with 3 kWp rooftop photovoltaic (PV) generators. The calculations were performed using 30-minute generation and consumption data from a large scale smart meter project in Cyprus. To...

During the last two decades, the use of residential photovoltaic systems (PVs) has been widely promoted by governments through various support mechanisms such as feed-in-tariffs, net-metering, net-billing, etc. These support schemes have developed a secure investment environment, increasing the penetration level of PVs in low-voltage distribution g...

Micro‐grids as ‘micro‐graphs’ of the power systems involve the management of small loads, either isolated or connected to the main grid. Load forecasting is a tool of fundamental importance in power systems design and operation. During the last years, many types of research have focused on aggregated system loads. However, few studies deal with sma...

Over the last decades, the growing energy consumption of commercial and residential buildings has considerably increased the energy-related carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) emissions. At EU level, the Energy Performance of Buildings Directive (EPBD) has intro...

--- The paper has been published: DOI: 10.1016/j.renene.2020.01.061 --- Over the last few decades, there is a constantly increasing deployment of solar photovoltaic (PV) systems both at the commercial and residential building sector. However, the steadily growing PV penetration poses several technical problems to electric power systems, mainly rel...

Scope of this paper is to examine the performance of two disaggregation schemes for NILM algorithms based on the utilization of current harmonic vectors. The analysis is based on measurements performed on real residential installation and the utilized features regarding the formulation of the load signatures of the appliances refer to the odd harmo...

The performance of neural networks in load forecasting tasks is highly influenced by the selection of the inputs. This selection is either problem specific or is relied on the literature. The scope of the present study is to compare two features (i.e. inputs) selection methods based on metaheuristics. Thus, the inputs selection process is treated a...

Significant harmonic voltage induction levels can be caused by distribution power lines, especially in distribution networks of North America. To investigate the harmonic voltage induction caused by overhead distribution lines to underground insulated conductors, it is critical to calculate accurately the mutual earth impedance between the conducto...

The scope of the present study is the assessment of a Particle Swarm Optimization (PSO) method for optimal input selection for Short-Term Load Forecasting (STLF) tasks. The test case involves the STLF of a high to medium voltage transformer, where a Feed-Forward Neural Network (FFNN) is trained and applied. An effective training process is crucial...

In order to determine the most suitable storage system for buildings with photovoltaic generators (PVs), a holistic analysis of the energy consumption is often required. In that sense, this paper provides a comparative assessment of thermal and battery storage in the context of nearly zero energy buildings (NZEBs). A NZEB with a PV, heat pump and a...

In this paper, a thorough analysis is performed to evaluate the impact of the battery energy storage systems (BESSs) on the electrical behavior of the prosumers. Its distinct feature is the use of real measurements acquired from three pilot case studies located at the region of Northen Greece. Two types of BESS technologies are examined, namely the...

This paper examines the application of machine learning techniques in NILM methodologies based on the first three odd harmonic order current vectors as the only attributes of the appliances. Proper formulation of the measured current waveform of appliances’ combinations is also presented. We apply our methodology on performed measurements of typica...

The penetration of Electric Vehicles (EVs) is rapidly increasing at the Low Voltage (LV) level, thus increasing the electrification rate of transport. Moreover, Photovoltaic (PV) systems at the LV level have been constantly increasing as well. Buildings with PVs on their roof and EVs as the main transport means may well become the norm the followin...

Natural gas is considered as a crucial power source both for electrical and thermal loads. Natural gas markets are continually expanding, a fact that raises the need of formulating new energy services to the end-users. The aim of the present paper is to develop a two-stage clustering process that leads to the formation of natural gas demand profile...

In this paper, a novel version of the Optimal Distributed Generation Placement (ODGP) problem regarding the siting and sizing of Renewable Energy Sources (RESs) units is presented, called Optimal RES placement (ORESP). Power losses constitute the objective function to be minimized, subject to operational constraints. The simultaneous installation o...

In the smart home context, one of the features that most users would desire is the knowledge of the operation of each electrical appliance without the need to install expensive smart plugs or measuring equipment at each outlet-appliance. The Non-Intrusive Load Monitoring (NILM) idea is an alternative method where only one meter is utilized. However...

Increase of photovoltaic (PV) systems penetration in distribution networks is being challenged by technical barriers, especially in low voltage (LV) networks, such as over-voltages caused by reverse power flows and high PV power injection to the grid. Among other solutions for over-voltage mitigation, active power management can be a highly effecti...

Decentralized energy storage systems (ESSs) can provide great advantages to low-voltage (LV) distribution networks, enhancing the further penetration of photovoltaic (PV) systems in existing electrical grids. An ESS can locally absorb the PV produced energy during periods of high solar irradiation, thus alleviating potential overvoltages in distrib...