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Despite voluminous research on barriers to exporting, knowledge on the inhibiting role of specific obstacles confronted by firms when exporting via cross-border e-commerce (CBEC) is virtually absent. Using data from a cross-industry sample of 1256 firms located in 25 different European countries, we shed light on this issue by examining the organizational determinants and performance outcomes of CBEC barriers. The results revealed these barriers are more evident in the case of firms with smaller size, lacking experience, and having no affiliation with other companies. It was also found that all different types of CBEC barriers, namely financial complexities, coping with foreign markets, supplier restrictions, technical difficulties, and product limitations, are negatively affecting online export performance. Finally, both the home country’s level of digital infrastructure and the foreign market’s Internet penetration rate exhibited a strong moderating effect on the association between CBEC barriers and export performance.

Shallow Geothermal Energy (SGE) systems find application through the use of Ground Source Heat Pumps (GSHPs) for space heating and cooling. GSHPs provide a higher performance over the alternative conventional Air Source Heat Pump (ASHP) systems, and have seen an increased interest with the continuous energy price increase and the need for lowering the CO2 emissions to meet the European Union “Fit for 55” targets. The high initial capital required for the GSHP systems in the residential sector is the main preventive factor for the GSHP systems. Recent studies revealed that with the nearly Zero Energy Buildings (nZEB) EU derivative in effect, the residential dwellings are built with a higher insulation on the building’s envelop and therefore with a lower heating and cooling demand; hence the potential payback period of such systems is increased.Geothermal energy District Heating (DH) on the other hand could make these systems more viable with the advantage of lower carbon emissions, lower maintenance and a lower cost, but at the moment the infrastructure and availability are mainly present in central and northern Europe, where a higher heating demand is required compared to the southern EU. Having a central unit for distribution however, requires a large plant area, and of course the need for infrastructure and insulated pipes. An alternative to these solutions could be the use of SGE systems at a micro scale level.To this extent, this research aims to computationally investigate the possibility and potential of SGE systems for a micro-scale urban environment. A theoretical case study is developed, with the inclusion of residential blocks categorized as “islands” for the production, use and distribution of SGE as a form of 5th generation (5G) DH and Cooling (DHC) with Mediterranean climate in the island of Cyprus. The case study includes either multiple multi-story residential buildings with nZEB characteristics or multiple detached residential buildings within a residential block, typical for the island of Cyprus. The heating and cooling demands, as well as the peak loads are estimated and the Ground Loop Design (GLD) software is used to size the required vertical Ground Heat Exchangers (GHEs) with different configurations. The effect of the unbalanced ground temperature and the temperature gain/ loss from the heat distribution is examined with the use of COMSOL Multiphysics software. Results indicate a potential advantage of the use of GSHP systems at a residential use micro-scale in terms of costs reduction and promotion of the geothermal energy use.

Despite the significant role played by family business firms in the economy, society, and environment of almost every country, there is limited knowledge as to their socially responsible conduct. This article presents the results of a study focusing on the drivers and outcomes of both internal and external CSR strategies adopted by these firms. Based on a sample of 193 family business firms in Cyprus, we confirm that certain dynamic capabilities, namely sensing, adaptive, and strategic flexibility, have a favorable effect on the development of both internal and external CSR strategy in family business. The implementation of these CSR strategies was also found to generate a social-based competitive advantage, which was conducive to heightened market performance. This impact of social-based advantage on market performance was revealed to be positively moderated by both competitive intensity and social public concern.

Editorial

Ground Source Heat Pumps (GSHPs) are used for space heating and cooling, where the Ground Heat Exchangers (GHEs) are used to extract or reject heat from/to the ground. GHEs come in various configurations, vertical or horizontal. Compared to Air Source Heat Pumps (ASHPs), GSHPs, albeit having a higher installation cost, achieve a better coefficient of performance (COP) and, hence, electricity savings. This reduction in consumed energy is translated to a reduction in fossil fuels and environmental “harmful” gas emissions. As the environmental impact does not lie in a single aspect, it would be useful not to stop the discussion in terms of COP and cost, but to identify whether a GSHP system is indeed a sufficiently overall greener solution. Hence, a more comprehensive investigation on the environmental impact of different types of GHEs as part of a GSHP compared to an ASHP system is attempted in the current study. A case study of a residential building with a fixed heating and cooling load is considered for moderate climate conditions. Using GLD software, a GSHP system is studied for various GHE configurations. The system undergoes a Life Cycle Analysis (LCA), with the yearly heating and cooling load as functional unit, for a direct environmental impact comparison between the GHE configurations and an ASHP system. The openLCA software is used for the application of two different methods, namely CML2001 and Eco-Indicator99 for seven and three impact categories respectively. It is concluded that the ASHP system exhibits the highest impact for all the main categories, while among the GSHP systems the vertical coaxial GHE configuration exhibits the highest impact and the horizontal GHEs the lowest, at times significantly below the ASHP impact. The largest reduction among all categories for the vertical and horizontal GHEs respectively is about 22% and 24% for the CML2001, and 17% and 21% for the Eco-Indicator99.

Building on Emotion Regulation Theory, we examine the role of an exporter's emotional intelligence (EI) in enhancing the quality and boosting the long-term orientation of the working relationship with its import buyers. Using data gathered from 262 Greek exporters, we confirm that the proper use of EI helps to improve trust, commitment, cooperation, and satisfaction in the relationship with their importers, which subsequently contribute to its long-term orientation. This favorable effect of EI on relationship quality dimensions is amplified when exporters deal with importers located in countries with cultures characterized by low power distance, low individualism, low masculinity, high uncertainty avoidance, and high (national) long-term orientation.

PurposeAnchored on the broaden-and-build theory and the circumplex model, the authors develop and test a conceptual model in which satisfaction, influenced by an effective handling of communication, cooperation, conflict, and opportunism, is set as the predictor of inter-partner creativity in the relationship between hotels and their foreign travel agents under the Covid-19 pandemic.Design/methodology/approachThe conceptual model was tested with data collected from 190 randomly selected hotel units located in Greece, using both online and drop-in questionnaire methods. Data were analyzed using SEM analysis.FindingsSatisfaction with the working relationship was found to be enhanced by improving communication and cooperation, as well as by keeping conflict and opportunism at low levels. This was a strong predictor of inter-partner creativity, although less pronounced under high levels of relational distance and rigidity.Research limitations/implicationsThe study should be extended to other country settings, replicated at different levels of crisis severity, and use dyadic data. Additional environmental factors could be used as boundary conditions, while our model could be expanded to include additional drivers and consequences of inter-partner creativity.Practical implicationsTo generate inter-partner creativity, there is a need to maintain high levels of satisfaction through proper communication, enhanced cooperation, conflict minimization, and avoidance of opportunistic actions. Also, to better translate satisfaction into inter-partner creativity, interacting parties should keep distance at low levels, while at the same time demonstrate greater flexibility.Originality/valueThe study unveils the role of effectively managing behavioral factors in inter-firm relationships to develop creative solutions to the Covid-19 crisis challenges, an issue neglected by prior research. The study also sheds light on the contingent effects of distance and rigidity, two important factors moderating relationships under crisis. The study applies for the first time two psychological-based theories, the broaden-and-build theory and the circumplex model, to an international marketing crisis situation.

Geothermal energy finds application with Shallow Geothermal Energy (SGE) systems for space heating and cooling. Ground Source Heap Pumps (GSHPs) constitute the main systems used in SGE when coupled with Ground Heat Exchangers (GHEs). GHEs are essentially a network of tubes that extract or reject heat to and from the ground. GSHP systems have recently gained more attention and are recruited for the reduction of fossil fuels and CO2, as an alternative to Air Source Heat Pump (ASHP) systems. However, recent advancements of the ASHP systems through the improvement of their coefficient of performance (COP) classify these at a very competitive scale against GSHP systems.The directive of the European Union (EU) on the nearly Zero Energy Buildings (nZEB) is already in effect, and requires the residential buildings to have better insulation on the building’s envelop, leading to a reduced heating and cooling demand. Such cases could further weaken the higher energy performance of GSHPs and make these systems a not so attractive alternative compared to ASHP systems. This research aims to investigate such scenarios using seven case studies, at seven different locations across Europe. The same residential building is used in all cases with nZEB technical characteristics. To this extent, a Life Cycle Analysis (LCA) is performed for the environmental evaluation using the ReCipe impact method from a midpoint perspective. The openLCA software is considered, coupled with the Ecoinvent 3.6 dataset for the impact methods and databases. A comparison is made of the case studies through an analysis of the global warming potential impact category. The results show that the northern European countries exhibit a better comparison performance between the ASHP and GSHP systems, compared to the southern European countries.

Many people may be interested in Paleontology since the subject allows for large amounts of imagination and freedom in the creation of scenes. Dinosaurs draw the biggest interest because of their diversity in peculiar forms and often unusually large size of many species. There are people like artists who help the field paleontologists to describe, interpret and reconstruct fossils, and others that create drawings, restorations, sculptures and, most recently, computer animations for science, art and joy. To this end, a successful professional should have specific knowledge that will allow them to produce high-quality work. The current paper aims at: 1) providing knowledge on various topics of Paleontology, in order to understand the time scale of life on earth, its evolution and diversity; 2) generating appreciation for the evolution of climatic conditions, continental plates and movement and the Mesozoic environment in which dinosaurs evolved; 3) offering an understanding of scientific nomenclature used in Paleontology, and interpretation of drawings and meanings; 4) helping one to realize how scientists extract information from bones, tracks, eggs, embryos and other remains; 5) examining the physiology of dinosaurs, their metabolism, behaviors, growth rates estimated lifetime and diet; and 6) leading to the understanding of the relations between different dinosaur species and how Paleontologists complete missing parts from uncomplete skeletons. Examining the evolution of life, we observe that life began about 3.8 billion years ago in the deep sea. The first simple animals such as worms and jellyfish appeared in the oceans around 600 mya. The crust of the earth continuously moves to produce changes in the land masses and changes in the climatic conditions that affect the evolution of life. The life of the earth is divided into geological eras. At the end of each geological era, a major event of extinction occurred, which every time obliterated important groups of life. Dinosauria was one of the most successful clades of animals that lived on terrestrial ecosystems for over 160 million years, but was extinct at one of the major extinction events 66 mya. The remains of animals allow scientists and artists to recreate their forms usually in great detail and extract a lot of information about their lives. The paper describes in detail how and where to find information and explains how to interpret them in order to understand the meanings. The paper presents all the above in a simplified way giving the required knowledge without using difficult scientific terms and provides the essential knowledge to the interested person to appreciate the science of Paleontology.

This paper addresses the topic of site characterization for the design of Shallow Geothermal Energy (SGE) systems, namely of thermoactive geostructures, which are geotechnical structures, such as piles, retaining walls and tunnel linings, also used as heat exchangers as part of closed-loop SGE systems. Such solutions, being increasingly adopted for buildings’ and infrastructures’ heating and/or cooling, are considered sustainable and cost effective. For the design of the primary circuit of the SGE system, which is embedded within the superficial soil layers, a comprehensive knowledge of the ground condition at the site is mandatory. This includes the evaluation of the energy features and whether the system can provide the required energy needs during the operational period, as well as the verification of the structural and geotechnical safety and functionality requirements. The site characterization for SGE systems involves different stages, from desk studies to detailed characterization, including in-situ trials, laboratory testing of undisturbed soil samples and the study of possible interferences. The specific aspects that will be addressed are: (i) the assessment of the site undisturbed ground temperature and its hydrogeological features; (ii) the thermal and thermomechanical characterization of the different soil layers; (iii) the investigation of the ground-heat exchanger thermal resistance; (iv) the collection of information related to the environmental constraints and to potential interferences among multiple users, which are related to the service life of the structure. The overall aim is to ensure a proper design of the SGE system for guaranteeing its sustainability in the long term.

The authors propose a conceptual model of the drivers, moderators, and outcomes of a firm's effective import strategy, anchored on the dynamic capabilities and industrial organization theories. Whereas the former theory explains the mechanism through which dynamic capabilities facilitate import strategy effectiveness, which boosts competitive advantage and ultimately enhances financial performance, the latter theory sets the foundation for explaining the contingency role of both competitive intensity and environmental uncertainty on translating effective import strategy into competitive advantage. The model was tested using a sample of 151 small and medium-sized British importers, with results indicating that high levels of certain dynamic capabilities of a generic (i.e., adaptive and entrepreneurial) and import-specific (i.e., source identification and market development) nature are conducive to import strategy effectiveness. Study results also revealed that import strategy effectiveness generates both a product-differentiation advantage and a low-cost advantage, although this is contingent on the degree of competitive intensity and environmental uncertainty prevailing in the importer's home market. Finally, the study confirmed that both productdifferentiation advantage and low-cost advantage have a favorable impact on the importer's financial performance.

The increasing penetration of renewable energy technologies causes major problems in the power network, as their generation cannot be totally predicted. Along with fluctuations in the generation of renewables due to weather uncertainties, storage is very important for mitigating several problems that may arise, affecting the stability and reliability of the grid. In particular, in recent years there has been an emphasis on residential storage applications (behind-the-meter storage), with the aim of increasing the energy self-consumption and therefore reducing electricity bills. The proposed model consists of a 3 kWp rooftop solar photovoltaic (PV) system connected to the grid through converters and a battery-supercapacitor hybrid energy storage system. The model is developed and simulated in the MATLAB/Simulink software environment, based on mathematical analysis and average modeling. The supercapacitor handles rapid changes that occur within 0.2 s, and this can relieve the battery stress and extend the battery lifetime. The building’s electricity demand is satisfied through the PV, hybrid energy storage and/or grid. A new filtration-based power management algorithm (PMA) is proposed here, prioritizing the utilization of the PV and battery-supercapacitor instead of the grid, thus achieving a reduced power exchange between the building and the grid and increasing the PV self-consumption and self-sufficiency of the building. The dynamic performance of the proposed model is verified through several simulations over short time periods (10–30 s) for different scenarios that could occur. The obtained results show that the model works properly and responds extremely fast during the different mode transitions, exhibiting a very fast DC-bus voltage regulation with a very small ripple voltage of up to 5 V (a maximum of ± 0.625%). Additionally, both battery and supercapacitor remain between their minimum and maximum limits. Finally, an effective power sharing is achieved between the PV, the battery-supercapacitor storage, the building load and the grid.

This work presents an in-depth analysis, identifies and derives the modulation processes in the Thyristor controlled Reactor by applying the Switching Function technique. The basic expressions of the circuit for current and voltage are derived as a function of the Switching Function. Hence the steady state analysis is performed, and the large signal mathematical models are derived. The model has the advantage of incorporating both the switching action of the thyristors and its triggering behaviour. Such a model can be used to investigate the current harmonics in a dynamic environment. Furthermore, the derived model is verified using the PSIM simulation software. The mathematical model results and the circuit simulation results are both analysed and discussed. As the results show, the proposed mathematical model correctly predicts the order and magnitude of the current harmonics with minimal error; less than 0.4% up to the fifth harmonic. Finally, it is worth noting that the switching function mathematical model is simple and its speed of execution is improved significantly by investigating specific range of harmonics.

The increased penetration of renewables and the variable behavior of solar irradiation makes the energy storage important for overcoming several stability issues that arise in the power network. The current paper examines the design and stability analysis of a grid-connected residential photovoltaic (PV) system with battery–supercapacitor hybrid energy storage. The battery and supercapacitor packs are connected to the common 400 V DC-bus in a fully active parallel configuration through two bidirectional DC–DC converters, hence they have different voltage levels and their power flow is controlled separately. A detailed small-signal stability analysis is considered for the design of the current controllers for the bidirectional converters of the battery and supercapacitor. An important contribution here is that a detailed stability analysis is performed for both the boost and the buck mode of operation for the battery and supercapacitor converters, resulting in more accurate tuning of the controllers. Moreover, the small-signal stability analysis of the voltage source inverter (VSI) is considered in order to design the DC-bus voltage controller, where a reference output current is obtained using a phase-locked loop (PLL) for grid synchronization. The proposed model is developed and simulated in the MATLAB/Simulink software environment, based on mathematical analysis and average modeling. The simulation results verify the dynamic performance of the proposed model, through several rapid changes in PV generation and in load demand. Also, the model works properly and responds extremely fast during different mode transitions, exhibiting a very fast DC-bus voltage regulation with a very small ripple voltage (a maximum of ± 0.625%). Finally, the supercapacitor handles the rapid changes occurring within 0.2 s, hence this can relieve the battery stress and extend the battery lifetime.

© 2019, The Joint Center on Global Change and Earth System Science of the University of Maryland and Beijing Normal University. Ground heat exchangers in conjunction with shallow geothermal energy system applications have received significant attention in the case of renewable energy. Soil thermal properties such as thermal conductivity and specific or volumetric heat capacity are important aspects for the design of such systems, affecting the performance. They can be obtained with the use of empirical prediction models, laboratory tests and/or in situ tests. Laboratory tests can be performed either under steady-state or under transient conditions and have the advantage of requiring small volumes of soil and producing fast results. There are many types of heat probes commercially available, with limited—though—comparative assessment available in the literature. The current paper deals with the assessment of ground characteristics of seven samples of soil and rock collected from a certain area in the Mediterranean island of Cyprus. Such properties are the thermal conductivity, the thermal diffusivity, the volumetric heat capacity, but there are some other physical properties also. The laboratory testing was done under transient conditions and included measurements taken by two needle probes and one surface probe from two different commercial apparatuses. Comparison of the obtained results for the thermal properties of the samples was made and was also supported by numerical simulations using the COMSOL Multiphysics software through a finite element analysis method on the convection–diffusion equation for heat transfer. Laboratory testing on physical properties of the samples such as moisture content, specific gravity, permeability and particle size distribution was also performed, yielding useful results related to the assessment of the thermal properties.

Energy in buildings covers a major and wide range of subject, which has attracted a great interest of the academic sector in recent years. Due to the high share of the global primary energy consumption associated with buildings, many studies have been published toward energy efficient buildings and the reduction of their primary energy consumption and energy management and optimization, for both Renewable Energy Sources (RES) and non-RES. As a result, a plethora of methods for managing the energy consumption and optimizing the integration of the RES in buildings have been proposed. The optimized dispatch of battery energy seems a promising method for managing the energy consumption profiles within buildings and achieving energy targets such as nearly Zero Energy Buildings (nZEBs). The current paper attempts a review of various studies related to convex mathematical optimization techniques for reducing the energy consumption in buildings, in real-time and via storage, either with or without integrated RES.

The paper focuses on the methodology for modeling the thermal response of vertical Ground Heat Exchangers (GHEs), when imposing underground water flow and a temperature gradient on the numerical model to represent the temperature of the depth profile. Four underground layers with different properties were studied, in order to identify their contribution in the total response of the GHE. In more detail, vertical GHEs in water saturated and dry soils, with or without water flow, are modeled with the equations that govern the heat transfer being presented. The numerical solution of the equations is based on the Finite Element Method (FEM) with boundary values. The model is validated with actual data of a Thermal Response Test (TRT) carried out in Lakatameia, Cyprus. Using the validated model, the heat injection rate of a GHE is investigated by determining the effect of the (a) summer and winter mode of operation, (b) underground temperature variation in depths smaller than 7 m due to daily and seasonal changes, (c) borehole radius, (d) borehole grout properties, (e) U-tube diameter, (f) U-tube leg and borehole centers distance, and (g) groundwater flow velocity.

It is an undoubted fact, within the scientific community, that the global temperature has increased by about 0.7°C over the last century, a figure that is considered disproportionally large. With the whole world being alarmed, the scientific community has assumed the task to explain this warming phenomenon. This has resulted in the formation of basically two schools of thought with two opposing theories. The first theory (the most popular one) claims that the prime guilty for the recent temperature increase is the release of greenhouse gases – mainly Carbon Dioxide (CO2) – coming mostly from the burning of fossil fuels, the clearing of land and the manufacture of cement. Due to these anthropogenic activities the concentration of CO2 has increased by about 35% from its ‘pre-industrial’ values, with all the resulting consequences. There are though other factors – besides the greenhouse gases – that affect the global temperature, like changes in solar activity, cloud cover, ocean circulation and others. Therefore, the ‘second’ theory claims that it is the Sun’s activity that has caused the recent warming that, incidentally in this theory, is considered to be in the generally expected limits of the physical temperature variation throughout the aeons. One assumption on how the Sun is affecting the climate is that the magnetic field and the solar wind modulate the amount of high energy cosmic radiation that the earth receives. This in turn affects the low altitude cloud cover and the amount of water vapor in the atmosphere and thus regulates the climate. (It must be noted that water vapor is considered as the main greenhouse gas.) In the sequel both of the above-mentioned theories are examined and conclusions about their soundness are drawn. Firstly (section 2), an analysis in past time of the temperature of the Earth is presented, showing that today’s temperatures are not in any way extraordinary, unnatural or exceptional, contrary to what many scientists claim. In fact, on large time scale today’s temperatures agree with what was expected for this geologic period, while on a small time scale the higher temperatures observed are the result of a natural recovery of the planet from the global coldness of the Little Ice age. In section 3, the view of the Intergovernmental Panel on Climate Change (IPCC) on the effect of the accumulation of the CO2 in the atmosphere is presented. Then, in section 4 the CO2 accumulation effect during the past is examined on large and small time scales. Note that Florides & Christodoulides (2009) using three independent sets of data (collected from ice-cores and Chemistry) presented a specific regression analysis and concluded that forecasts about the correlation between CO2-concentration and temperature rely heavily on the choice of data used, making it very doubtful if such a correlation exists or even, if

Shallow Geothermal Energy Systems (SGESs) constitute Renewable Energy Systems (RES), which find application in the residential sector through the use of Ground Source Heat Pumps (GSHPs). GSHPs are associated with Ground Heat Exchangers (GHEs), whereby heat is gained/lost through a network of tubes into the ground. GSHPs have failed to flourish in the RES market due to their high initial costs and long payback periods. In this study, the use of Energy Geo-Structure (EGS) systems, namely, the foundation (or energy) piles and the foundation bed of a residential building in Cyprus, was computationally modeled in the COMSOL Multiphysics software. First, the single-houses’ trend in number of units and area in Cyprus was examined and a theoretically typical house with nearly Zero Energy Building (nZEB) characteristics was considered. The heating and cooling loads were estimated in the TRNSYS software environment and used as inputs to investigate the performance of the GSHP/GHE systems. Both systems were shown to exhibit steady performance and high Coefficient of Performance (COP) values, making them an alternative RES solution for residential building integration. Next, the systems were economically evaluated through a comparison with a convectional Air Source Heat Pump (ASHP) system. The economic analysis showed that the cost of the suggested conversions of the foundation elements into GHEs had short payback periods. Consequently, either using the foundation piles or bed as a GHE is a profitable investment and an alternative to conventional RES.

Shallow geothermal energy systems (SGES) may take different forms and have recently taken considerable attention due to energy geo-structures (EGS) resulting from the integration of heat exchange elements in geotechnical structures. Still, there is a lack of systematic design guidelines of SGES. Hence, in order to contribute towards that direction, the current study aims at reviewing the available SGES modeling options along with their various aspects and practices. This is done by first presenting the main analytical and numerical models and methods related to the thermal behavior of SGES. Then, the most important supplementary factors affecting such modeling are discussed. These include: (i) the boundary conditions, in the form of temperature variation or heat flow, that majorly affect the predicted thermal behavior of SGES; (ii) the spatial dimensions that may be crucial when relaxing the infinite length assumption for short heat exchangers such as energy piles (EP); (iii) the determination of SGES parameters that may need employing specific techniques to overcome practical difficulties; (iv) a short-term vs. long-term analysis depending on the thermal storage characteristics of GHE of different sizes; (v) the influence of groundwater that can have a moderating effect on fluid temperatures in both heating and cooling modes. Subsequently, thermo-mechanical interactions modeling issues are addressed that may be crucial in EGS that exhibit a dual functioning of heat exchangers and structural elements. Finally, a quite lengthy overview of the main software tools related to thermal and thermo-hydro-mechanical analysis of SGES that may be useful for practical applications is given. A unified software package incorporating all related features of all SGES may be a future aim.

Underfloor heating systems provide comfort due to the natural heat flow distribution by a network of pipes, conventionally connected to a heat pump operating at low temperatures. To this extent, a renewable energy source could be an alternative solution. Acting as a case to investigate such systems, the Mediterranean island of Cyprus with a plethora of sunny days points to solar energy as the obvious solution. In this study, solar collector systems are recruited to supply the required heat for a typical Cypriot house, with the building&rsquo, s foundation acting as a thermal energy system (TES) unit. The heat supply to the building can then be distributed with natural convection from the TES. The solar collectors and the building&rsquo, s foundation system are studied with the aid of two software programs, namely TRNSYS and COMSOL Multiphysics. The former is used for the calculation of the heating and cooling load of the house as well as to estimate the energy provided by the flat plate solar collectors at specific conditions. The latter is then used to examine the TES unit with the heat gain/loss of the building. The obtained results, including analyses on the solar collectors&rsquo, area and the foundation thickness indicate that the suggested system would be able to sufficiently cover, partially or fully, the building&rsquo, s heating load.

Shallow Geothermal Energy, a Renewable Energy Source, finds application through Ground Source Heat Pumps (GSHPs) for space heating/cooling via tubes directed into the ground. There are two main categories of Ground Heat Exchanger (GHE) types: the horizontal and the vertical types. Ground Heat Exchangers (GHEs) of various configurations, extract or reject heat into the ground. Even though GSHP have higher performance in comparison to the Air Source Heat Pumps (ASHPs), the systems high initial costs and long payback period have made it unattractive as an investment. GSHP systems can also be utilized in the buildings foundation in the form of Thermo-Active Structure (TAS) systems or Energy Geo-Structures (EGS), with applications such as energy piles, barrette piles, diaphragm walls, shallow foundations, retaining walls, embankments, and tunnel linings. Energy piles are reinforced concrete foundations with geothermal pipes, whereby the buildings foundations are utilized to provide space heating and cooling. Apart from energy piles, another EGS system can be achieved by the incorporation of the building’s foundation bed as a GHE. Foundation piles are not required in all constructions, but a building’s foundation bed is mandatory. This configuration is still based on the principles of the energy pile.Energy piles have yet to be applied in Cyprus and, thus, a preliminary assessment considered and investigated before application would be useful. The potential of the GSHP systems by utilizing the building’s foundation through energy piles is considered here, for a moderate climate such as Cyprus, towards a Zero Energy Building. Typical foundation piles geometry in Cyprus consists of a 10m depth, a 0.4m diameter and reinforced concrete as a grout material, which is used at the foundation bed of the building. A typical dwelling in Cyprus is selected to be numerically modelled in this study. It is a three-bedroom, two-storey house with a 190m2 total floor area, matching the thermal characteristics of a Zero Energy Building (i.e., U-values of 0.4W/m2/K on all walls and ceiling and 2.25 W/m2/K on all doors and windows, respectively). A full-scale model is developed in COMSOL Multiphysics software, to examine the energy rejected or absorbed into the ground by taking the heating and cooling loads of the typical dwelling in Cyprus. The convection-diffusion equation for heat transfer is used with the three-dimensional conservation of heat transfer for an incompressible fluid on all domains except the pipes, where a simplified equation is used. Different months in winter and summer are accounted for the simulations and the fluid-in – fluid-out temperature difference is presented. Finally, an economic evaluation of the systems examined above is presented, in order to check its viability. It is concluded that utilizing the dwelling’s foundations can be a better investment than using GHEs in boreholes.

Renewable Energy Sources have been growing rapidly over the last few years. The spreading of renewables has become stronger due to the increased air pollution, which is largely believed to be irreversible for the environment. On the other hand, the penetration of renewable energy technologies causes major problems to the stability of the grid. Along with the fluctuations of the renewable energy technologies production, storage is important for power and voltage smoothing. Energy storage is also important for energy management, frequency regulation, peak shaving, load leveling, seasonal storage and standby generation during a fault. Thus, storage technologies have gained an increased attention and have become more than a necessity nowadays. This paper presents an up to date comprehensive overview of energy storage technologies. It incorporates characteristics and functionalities of each storage technology, as well as their advantages and disadvantages compared with other storage technologies. Comparison tables with several characteristics of each storage method are included, while different applications of energy storage technologies are described as well. Finally, several hybrid energy storage applications are analyzed and different combinations of energy storage technologies are reviewed.

The advancement of technology and renewable energy systems (RES) have evolved considerably through the years. Geothermal energy was first introduced in Italy in 1904 and has ever since dramatically increased in efficiency. One of the main types of RES, Ground Source Heat Pumps (GSHPs), are used for heating and cooling a space when coupled with Ground Heat Exchangers (GHEs). GSHPs extract or reject heat to the Earth via a network of tubes. The closed loop system, either vertical or horizontal, is the most common of the configurations. Alternatively, pipes can run all the way down to utilize natural underground water sources, when present, in an open loop configuration. GHEs have significantly higher performance over conventional air-to-air heat exchanger systems and the reduction of their cost and the improvement of their overall efficiency through their design are crucial in research. In this paper are presented and reviewed the design aspects of GHE systems. In particular are discussed the types of GHEs such as open or closed loop systems, vertical or horizontal, U-tube or spiral, energy piles and hybrid systems. A comparative analysis through the literature of the various geometrical aspects of GHEs and the geothermal investigation of the ground environment and the materials used in the construction of GHEs are also presented. Then is analyzed the modeling – experimental and mathematical – of GHEs, with terms that have been extensively studied, like borehole thermal resistance, thermal characteristics, thermal response test, line-source and cylindrical-source models, discussed in detail. Next a demonstration of designing a numerical model of a GHE system through a software, taking into consideration the thermal characteristics, is given. Finally, a comparative detailed list in the form of a table of more than 30 mathematical and/or experimental GHE studies is provided, focusing on the important factors analyzed and findings of each. The overall aim of the current review study is to help improve the efficiency and the total manufacturing cost of GHEs.

Industrial processes are currently responsible for almost 26% of European primary energy consumptions (275 Mtoe/yr). Furthermore, most of the energy sources that drive the industrial sector are fossil fuel based. Every industrial process is characterised by a multitude of waste heat streams at different temperature levels whose recovery would undoubtedly contribute to the enhancement of the sustainability of the industrial sites and their products. Waste heat recovery systems can offer significant energy savings and substantial greenhouse gas emission reductions. For the latter to materialise technological improvements and innovations aimed at improving the energy efficiency of heat recovery equipment and reducing installation costs should take place. This paper outlines the opportunities and the potential for industrial heat recovery in the European Union by identifying and quantifying primary energy consumption in the major industrial sectors and their related waste streams and temperature levels. Through a systematic analysis considering waste heat and Carnot’s potential estimation, detailed results are given for all industrial sectors, temperature ranges and EU countries. The ‘big picture’ is rather promising with regards to the estimated total waste heat potential. The research presented in this paper has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 680599. Aspects of the work are also funded by the Centre for Sustainable Energy Use in Food Chains (CSEF). CSEF is an End Use Energy Demand Centre funded by the Research Councils UK, Grant No: EP/K011820/1.

We present second-order expressions for the free-surface elevation, velocity potential and pressure resulting from the interaction of surface waves in water of arbitrary depth. When the surface waves have nearly equal frequencies and nearly opposite directions, a second-order pressure can be felt all the way to the sea bottom. There are at least two areas of applications: reflective structures and microseisms. Microseisms generated by water waves in the ocean are small vibrations of the ground resulting from pressure oscillations associated with the coupling of ocean surface gravity waves and the sea floor. They are recorded on land-based seismic stations throughout the world and they are divided into primary and secondary types, as a function of spectral content. Secondary microseisms are generated by the interaction of surface waves with nearly equal frequencies and nearly opposite directions. The efficiency of microseism generation thus depends in part on ocean wave frequency and direction. Based on the second-order expressions for the dynamic pressure, a simple theoretical analysis that quantifies the degree of nearness in amplitude, frequency, and incidence angle, which must be reached to observe the phenomenon, is presented.

Thermal processes account for 70% of the EU industry final energy, with 30% thereof being wasted through losses. This fact has been a motivating factor toward applying various technologies and methods for waste heat recovery. Already such technologies exist and are applied in many industrial sectors, while some “new” technologies have also been tested or suggested. It is therefore useful to obtain insight information into such processes, together with their temperature ranges and, hence, assess the potential market for each industrial sector. Here such an attempt is made, based on existing literature. Estimates on the total energy that can be recovered through the EU industry are given and a special case study on the important Iron and Steel industry is presented. This kind of information can be useful for the improvement of existing and the development of “new” technologies or techniques.

EU has seen an increasing demand for both nearly zero energy buildings (nZEBs) and building integrated Photovoltaic (BIPV) systems in the last decade. This stems from the energy-driven regulations relating to building efficiency improvements, requiring more realistic and smarter techniques to strengthen their employment and overall performance. Apart from the passive energy-efficiency measures of nZEBs (such as thermal insulation, energy saving appliances, etc.), more advanced and sophisticated energy management mechanisms have to take place in order to accommodate and support their crucial contribution to sustainable development. This paper presents the daily optimum dispatch of a battery, in a building with PV, using Linear Programming (LP) driven by Genetic Algorithm (GA), aiming the minimization of the building’s net energy. The obtained results show that there is a high potential of using such approaches for maintaining the net grid energy levels of a building as minimum as possible.

The increased penetration of renewables in power system generation has introduced several stability issues to existing power systems. Their intermittent nature in combination with the lack of rotational inertia made system operation even more difficult and frequency/voltage fluctuations larger. Storage systems have been identified as an ideal solution for mitigating these problems since their integration across the grid can reduce generation-load imbalances and assist in primary frequency regulation. Considering the importance storage systems have gained during the last years, in this paper we propose an energy management algorithm for a grid-connected PV system with battery storage. This model contains a Building Integrated Photovoltaic (BIPV) system connected to the grid through a DC-DC boost converter, a DC-AC inverter and a battery storage system in active parallel configuration. Considering that the consumption of the building is satisfied from either the PV, the low voltage grid and/or the battery storage system, a specific energy management algorithm is presented for this model, in order to provide an efficient power flow between the aforementioned sources and the building load. The proposed model is implemented and verified through several simulations in Matlab/Simulink.

The recent evolution of the Ground Source Heat Pumps (GSHPs) has initiated the debate whether it is economically feasible to install a GSHP as an alternative to an Air Source Heat Pump (ASHP). A typical house heating/cooling load for moderate climates is presented and discussed for comparison purposes. For this purpose, the thermal response of the Ground Heat Exchanger (GHE) and the estimated characteristics of the GSHP, based on existing experimental data and simulations in summer and winter through a CFD model are presented. The computed power rejected to the ground from the GSHP is discussed in relation to the HP characteristics at different operating temperatures, which affect the efficiency. More than one borehole for the GHE may be needed for the reduction of the temperature. Finally, a cost analysis is presented for different length GSHP systems and a comparison of the total energy savings is obtained. ASHP systems with the specifically designed, inverter technology ducted series HP are proven to be highly competitive with GSHP systems, which fail to be a clear viable investment for energy saving.

Previous studies in Cyprus classified the island in the category of low enthalpy with high potentials in the usage of geothermal energy for space air-conditioning. Due to the little existing information about the underground thermal properties, an extended geological sampling has been carried out on the island. Measurements of thermal properties have been performed in the laboratory at room temperature for all the collected samples both in their dry and water-saturated state. The impact on thermal conductivity of water in samples, the mineralogical composition, and the geological age of samples have been the objectives of the current study. Laboratory results of each rock type in Cyprus are found within certain ranges for each thermo-physical property as follows. Thermal conductivity values for dry rock samples vary between 0.4 and 4.2 W m−1 K−1, thermal diffusivity values range between 0.3 and 1.9 × 10−6 m2 s−1 and specific heat capacity values range from 0.5 to 1.5 J K−1 kg−1. Results also show that thermal conductivity and thermal diffusivity under moisture conditions increase for most of the lythotypes. The notable exception is Gypsum (Kalavaso Formation), which exhibits higher thermal response under dry conditions. Measured thermal properties also present a difference between thermal properties of the lithologies of the Troodos Ophiolite and the Circum Troodos Sedimentary Succession in Cyprus. Mean values of thermal conductivity and thermal diffusivity for dry samples and water-saturated samples have higher values for the lithologies of the Troodos Ophiolite than measured values for the lithologies of the Circum Troodos Sedimentary Succession, mostly due to their mineralogical composition. Moreover, the geological age of a lithology has been shown to affect its thermal response. Thermal conductivity of reef limestone and calcarenite rocks increases with the geological age of the lithology. In order to understand and visualize all measured data the Thermal Conductivity and the Thermal Diffusivity Maps of Cyprus have been compiled with the use of a Geographic Information System (GIS) to be available to engineers as a powerful tool for use in the design of thermal engineering systems. From the obtained maps Troodos Ophiolite can be visualized as a separate part by having the highest values.