Nearly Zero Energy Communities

The sustainability challenges involve the built environment responsible for a large share in the total energy consumption. Steps toward a sustainable path were formulated and started to be implemented all over the world and, it is important to notice that the technical focus is mainly set on the energy production and consumption. Thus starting from the already formulated concept of Nearly Zero Energy Buildings (nZEB) and from the lessons learned when implementing it, this paper presents a study on the development of a Nearly Zero Energy Community (nZEC). The Community of the R&D Institute of the Transilvania University of Brasov was built starting with 2009 till 2013 and consists of 12 low energy buildings hosting 29 R&D Centers. The energy consumed in 2015 and 2016 in this community was monitored and a seasonal variation was registered for both, electrical and thermal energy. It was observed that the variability in the thermal energy demand is much larger and has a specific trend for each year. This community has partially installed renewable energy systems and their output is registered and discussed, considering the consumption variability over the year aiming at delivering a preliminary assessment of the renewable energy systems that can insure the Nearly Zero Energy (nZEC) status to this micro-community. The results show that the electrical energy produced should give full use of the current existent transportation and distribution infrastructure, while the thermal energy should be well managed at the micro-community level, to reduce the losses. An average share of 50% renewable energy was found to be able to cover the total energy demand in the laboratory buildings and in the R&D micro-community, confirming its goal as nZEC.

This study presents some results of an recent closed European Project, RePublic_ZEB [1], where an extensive analysis was conducted for identifying cost-optimal refurbishment solution an sets of solutions applied to exiting public buildings, towards nearly Zero Energy Buildings (nZEB) performance. The analysis was applied to 12 reference buildings identified in 8 countries participants in the project and for different building typologies. A cost-optimal solution sets matrix of the 12 buildings is presented together with the results of nZEB energy performance.

This paper highlights the implementation possibility of automated embedded systems for energy management into insular clusters of homes or off-grid buildings that can harness multiple renewable energy sources. As the embedded technologies and the Internet of Things concept are starting to merge stronger and faster from one year to another, we can ow acknowledge the new possibilities for energy efficiency and energy harvesting that are becoming mainstream. Traditional worldwide companies that provides IT&C services and electronic products solutions, have now a mature portofolio for IoT data communication and devices automation. In this respect, Cisco predicted that by the year 2020, at least 50 billions of devices will share a common communication network, thus any electronic device will be able to communicate with another in an automated manner. If by this time we were talking about the “Internet of People”, where people communicated with other people, now the paradigm have changed into the “Internet of Things” which enables devices communicate with other devices. To no surprise, this is a natural evolutionary step that aims to minimise the human efforts, accelerate information transmission, processing and execution, optimise and correct human errors and even provide the best alternatives to complicated problems by the help of AI (Artificial Intelligence). Regarding the energy sector, these smart systems have the purpose of providing energy efficiency, components compatibility, low carbon footprint and further exploit the renewable energies potential to a higher degree by hybridization.

In the near future, buildings will have to meet strict energy consumption standards in order to get as close as possible to the concept of nZEB (nearly Zero Energy Building), which means that buildings need to produce to a very large extent (10% for Romania) of their energy demand using renewable systems (RES) mounted on or near them. These standards can be met by at least three paths, simultaneously implemented: (a) reducing buildings losses, (b) designing renewable energy systems (RES) according to the constructive and architectural restrictions of the implementation location and (c) optimally managing the energy consumed by the building so that all available renewable sources are used at their maximum potential and only a minimum amount is consumed from conventional sources (fossil fuels). Implementing all described RES at building level (in order to meet nZEB standards) can raise real problems due to space or renewable source limitations. On the other hand, at district or even at city level the solutions for implementing all types of RES are more diverse and may support the local inhabitants to directly benefit from the advantages of nearly Zero Energy Communities (nZEC), if appropriate energy management systems (EMS) are used. The paper describes the basic principles of EMS focusing mainly on electrical energy, presents the renewable energy systems available in a newly established research community and proposes a management algorithm able to efficiently use the produced electrical energy considering local restrictions.

Within this article is presented a prototype house called EFDEN which is a research and educational project that represented Romania at Solar Decathlon Europe 2014 in Versailles France. The constructed solar house was built as a Positive Energy Building implementing multiple passive (phase change materials, greenhouse, solar shadings, heat recovery) and active (air-water heat pump for heating, cooling and hot water; vacuum tube collectors - for hot water and heating; cold water tank; heating water tank; hot water tank; heating/cooling coil; radiant panels-radiant heating and cooling in ceiling and walls; heat recovery unit - maximum efficiency above 90% for the fresh air treatment; BMS automation system, PV array for electric energy production) energy efficient strategies. The building total habitable surface is of 115 m2 and the total heated/cooled volume is 400 m3. Since 2014 the house was monitored in terms of the indoor climate parameters and energy consumption. It was found that indoor air quality is great with low values of CO₂ (<800 ppm) and also low radon levels (measured values with RadonScout <100 Bq/m3). As concerns the active systems among the most important elements it is mentioned the PV array with an installed power of 5.5 kW–22 polycrystalline moduls of 250 Wp each. During the year 2016 the PV array produced 7069 kWh while the energy consumed was 4156 kWh. Maximum values of production were recorded in June and July with 930–935 kWh/month. Beside measurements also multiple simulations of the system were also realized.

Architects have always been fascinated by light. So much that the most well-known definition of architecture, given by Le Corbusier refers to volumes and light: “Architecture is the masterly, correct and magnificent game of the volumes brought together under the light”. The great architect, Lous Kahn, considered that “The Sun does not realise how wonderful it is until after a room is made.” Accommodating natural light in the building is an architectural approach that leads to a passive gain as, by design, natural light is brought into dark spaces by means of architectural elements or specialized construction systems. Solar light pipes (seem to) have been the oldest systems and were used in Ancient Egypt, as means to bring light into dark places. The principle, forgotten for centuries, reappeared sometime in the mid-nineteenth century, was again forgotten and is once again reinvented today, being used in different buildings and spaces, with the same scope: to bring natural light into dark spaces. Not only the characteristics of natural light are beneficial for the living beings - animals and plants - but bringing daylight in (otherwise) dark spaces also saves energy- as we deal with passive systems - while creating new characteristics of the architectural space and image. The aim of the paper is to present a general view on the passive solar daylighting systems in architecture as well as a case study finalized in Romania.

Energy business shifts from the centralized organizations to networks of producers and consumers labelled as distributed energy generation. This global paradigm shift on energy markets is analyzed with focus on the European Union. The changes evolved during last three decades when the neo-liberal ideology dominated policies. The analysis is that imperfections caused by the vested interests on energy markets have motivated innovators to pursue downscaling of energy technologies based on the local, renewable resources. The innovative efforts invoked numerous local energy initiatives. Their motivations are presented. Local energy initiatives created conditions for adoption of the renewable energy technologies in communities entailing adaptations to the local conditions, which enabled the distributed energy systems. The energy enterprises constituted the fastest growing business in the European Union during 2008–2014. This growth can be attributed to policy support of the renewable energy supplies and to market demands for the distributed energy systems.

The paper represents a detailed analysis of the annual specific energy consumption’s variation according to the efficiency of the building’s utility services, the building’s usage pattern, the architectural concept and the thermal performance of the construction materials that make up the envelope. The methodology used to evaluate the energy consumption in a building is based on the degree-day concept, considering the latest meteorological data for the geographical locations considered. The results of the analysis performed on a building configured considering different hypothesis for the design choices and usage patterns are graphically presented to emphasize the weighing of the different factors that contribute to the annual energy consumption and to emphasize the way in which these weightings are changing along with each hypothesis.

The structure of electrical consumption in Bulgaria is changing dramatically after moving from centralized to market economy. The closure of a number of large industrial factories, removal of state and cooperative enterprises in the field of agriculture, etc. led to increased role of the household systems in the forming of the country energy balance. On the other hand a number of European and national documents require a sharp improvement of the energy characteristics of buildings, which would lead to low energy consumption or to nearly zero-energy buildings.In the present study the state of this matter in Bulgaria and the possible approaches to reach the requirements of the mentioned documents are discussed.The country’s regulations have been looked into, including the National plan for nearly zero-energy buildings 2015–2020, based on article 9, paragraph 1 from the Directive 2010/31/EU for energy characteristics of buildings. The size of the building stock, the types and characteristics of buildings have been analyzed. Considering the parameters of solar radiation, the application of photovoltaic arrays, installed on and close to the objects (facade, roof and other types of construction) has been justified. The necessity to change the curriculums related to the training of experts in the field of the new energy-efficiency technologies, including energy management and smart microgrid systems, is pointed out.

The energy demand is increasing at global level and also does the related greenhouse gas emissions. Solutions to mitigate their effects on the climate are intensively investigated and among the studies, the implementation of Renewable Energy Systems (RES) at the building level to harvest the renewable energy sources as solar, wind and geothermal are currently in top. These systems are efficient when the building has enough available surfaces, optimal positioned for their installation. In the case of communities with high buildings density, barriers can occur in terms of the lack of available surfaces, self-shadowing, self-shielding and mutual influences between the RES. The paper aims to evaluate the possibilities to extend the implementation of the RES at community level, using the available areas on- or nearby the buildings and nearby the community, maximizing thus the renewable useable potential. Numerical simulations are performed in TRNSYS to evaluate the yearly heating energy demand for a range of residential buildings, starting from a single-family residential building (considered as an unit with 100 m2) to a multi-family residential building (16 units each having 100 m2) highlighting the decrease of the energy demand when increasing the units number in a building. Further on, the yearly energy demand for domestic hot water and lighting is evaluated for each building. An energy mix based on geothermal, solar thermal and photovoltaic systems is simulated in TRNSYS, to mitigate the energy consumption from fossil fuels. The surface/depth of the geothermal heat exchanger is evaluated along with the electrical energy demand to drive a ground coupled heat pump assisted by solar thermal and photovoltaic system. The amounts of renewable energy obtained installing RES on the available buildings’ rooftop, facades and nearby surfaces are comparatively analysed, for these buildings gathered in small communities.

Today, more than half of the urban population in Romania lives in collective housing units based on standard typologies built from large prefabricated reinforced concrete panels. These units were built on a large scale between the early 60s and 90s in order to rapidly provide housing for a large number of workers coming from the rural areas due to the intense expansion of the industries near the cities. With the evolution of technology and social routines, these housing units are now outdated and consume significant amounts of energy for heating, cooling and ventilation while, not being able to meet modern living needs. Based on the main aspects of sustainable development, a retrofitting scenario of these building is proposed, i.e.: (1) social, by rethinking the space configuration within the apartments, accessibility and transforming the inner courtyards, now occupied by cars, into a positive space; (2) economic, by offering a new building envelope based on a ventilated facade system and by improving the existing facilities for heating, ventilation and cooling; (3) environment, by integrating renewable energy systems and passive design strategies - a new extension module is placed on top of the buildings that behaves as an active core and house a solar panel array and energy distribution networks. With the transition of the existing power grids to the so-called “smart grids”, such buildings can become, consumers as well as suppliers, and the possible energy losses on the grid to be eliminated.

Reducing the energy demand in the building sector is a priority in all EU strategies related to energy efficiency, climate and resources. The Energy Performance of Buildings Directive (EPBD recast 2010/31/EU) and Energy Efficiency Directive (2012/27/EU) constitute the key legislation of the EU in terms of reducing the energy consumption of buildings and their release of greenhouse gas emissions. According to recast EPBD, starting from January 2019 new buildings occupied or owned by public authorities should be Nearly Zero Energy Buildings (nZEB), while from 2021, this requirement applies to all new buildings and is likely to greatly increase the quantities of insulation materials, used in the construction sector. In this context, the paper presents general properties of thermal insulation materials from renewable sources, with the aim to raise awareness on the necessity of these products on Romanian/European market and to increase the interest of the producers for these materials, also for technologies required for using renewables in nZEB. The paper focuses on the straw and sorghum as materials from local agricultural waste that could be integrated into insulation products, and provides additional information for these materials in order to facilitate their use as materials for nZEB.

Five variants of material compositions of sloping roofs were analyzed from environmental perspectives. They were designed to fulfil the requirement from thermal transmittance (U = 0.10 W/m K) for nearly zero-energy buildings. The environmental impacts were expressed by indicators such as embodied energy (EE) from non-renewable resources, CO_2eq. emissions (GWP, global warming potential) and SO_2eq. emissions (AP, acidification potential) as well as environmental indicator ΔOI3. They represented the equivalent emissions within the LCA boundary - cradle to gate and input data were extracted from the LCA database - IBO. The final values were compared by using methods of multi-criteria decision analysis. The lowest value of embodied energy of 745.52 MJ/m2 achieved variant with lower thickness of mineral wool thermal insulation. Highest values of embodied energy of 1408.455 MJ/m2 achieved variant with additional thickness of mineral wool thermal insulation. The best alternative from CO₂ emissions (−106.1 kgCO_2eq./m2) was the variant defined as green roof but concurrently it achieved the highest value of SO₂ emissions (0.617 kgSO_2eq./m2). The worst variant from regarding CO₂ emissions (57.75 kgCO_2eq./m2) consisted of mineral wool thermal insulation.

Excessive urbanization, and, at the same time, lack of “green” land inside big cities are the reasons that have led to the need for enveloping buildings with vegetation. The present work proposes the presentation of the advantages of using succulent plants for green envelopment and of creating optimal microclimate conditions, thus improving the air quality, the environment and reducing energy consumption, by managing and using rainwater and by filtering out pollutants. Succulent plants are plants resistant to weathering, especially in drought periods, with a good water retention capacity, with a reduced root system, less demanding in relation to environmental conditions. They can ensure the retention of meteoric water, while in dry seasons. The absorbed water is evaporated and the surrounding air temperature is significantly reduced. Gray water, coming from rain can be used on a larger scale for regional planning, by irrigating green. As a consequence, we consider this approach a turning point in developing sustainability policies with environmental, social and economic effects.

A Building Integrated Photovoltaic (BIPV) façade is formed by PV panels integrated to a second skin forming an air gap between the two skins. The air gap is responsible for cooling the PVs and for removing the excess heat, to avoid building overheating. The ventilation of the air gap can be natural or mechanical. The system investigated in this study is a vertical, naturally ventilated system. This has a number of advantages, the most important being the avoidance of energy to power the fans, the operation with no noise and the avoidance of overheating which can happen when the fan stops in an active system. A BIPV system is designed in COMSOL simulations software in 3D geometry and tested by varying the temperature on the various surfaces of the system for different air velocities from 0.02 m/s to 2.5 m/s. Additionally, experimental tests are carried out to validate the model. The results show a good agreement between the simulated and measured values.

This paper is dealing with the development of a shell-structured solar tile collector for the use of solar energy in buildings especially to make domestic hot water. The idea of the new type of collector based on its energetic usefulness, but also on the aesthetic considerations were seriously taking into consideration. During the modelling and simulation steps of the solar collector system the thermal efficiency issues were also studied. The temperature distribution on the collector surface was measured and validated by an infrared camera recording. The developed roof integrated tile elements can be recommended in the course of planning new building for the renovation of the existing buildings, as well.

The present paper describes one theoretical model, used for designing the optimal structure of the one heating system, developed for new or thermal rehabilitated buildings. The model can be used for evaluating of the total heat demand for the building and to the establishing the optimal structure for bioenergy value chain, where the feedstock is the biomass wood chips produced on energy willow plantations. The studied model used in this design technique is for one high efficient type boiler, which is controlled by one PLC unit, creating in this way the autonomy of the system. The paper starts with the element of biomass and bioenergy value chain presentation. The second part is focused to presenting the theoretical algorithm for designed the optimal structure of the heating system and with the establishing the fuel needs and the used marginal land area where this type of feedstock can be produced. In finally is presented the cost benefits analyses for one model for sustainable biomass feedstock production on the short rotation plantation, which can be used and implemented in rural area for supplying the principal local authorities building with heat energy, produced by sustainable technology and creating in this way the first step to energy independency of the village. In this evaluation and modelling technique one solar thermal conversion unit are integrated in order to reduce the biomass consumption with 15–30%.

In this paper, a 1 kW closed sorption heat storage prototype is presented. The two main processes (charging and discharging) occur under reduced pressure. During the charging process, the thermal energy produced by the solar collectors in summer is used to partially vaporize the water contained in a diluted sodium hydroxide solution (NaOH). Then, the concentrated aqueous sodium hydroxide solution and the water are stored at room temperature in separate tanks until the discharging process. During discharging, ground heat is used as a heat source to evaporate the stored water under sub-atmospheric pressure in the evaporator. In a separate chamber, heat is produced during the exothermic process of water vapor absorption into the concentrated NaOH solution. The heat is then transferred to a working fluid that can be used, for example, in floor heating applications. Sodium hydroxide has a high water affinity; nevertheless, the fluid wetting on the heat and mass exchanger influences the absorption process efficiency. Different experimental methods to improve the surface wetting like surface modifications (structuring, use of ceramic foams) and fluid properties tuning (use of surfactants) are presented. The development of the structured surfaces and ceramic foams enhances the heat transfer and thus reduces the size of absorber unit.

The residential built environment is responsible for at least 40% of the entire energy consumption in EU out of which, at least 60% is required for heating, cooling and DHW, generating more than 24% of the overall CO₂ emissions. Through the EPBD and EED directives, the European legislation demands nearly Zero Energy Buildings (nZEB) or Low Energy Buildings (LEB) for all new or refurbished public buildings starting with 2019 and for all the other new or refurbished buildings starting with 2021. As EU partner, Romania has harmonized the national legislation and standards on energy efficiency and performance; however a series of complementary applicable measures need to be implemented in order to reduce the level of the thermal energy demand, and finally, using various renewable energy sources, the legal frame can be implemented with acceptable and feasible costs. This paper aims to conduct a comparative study of the energy demand calculated using the standard method and the TRNSYS-Weather Data method, to outline the influence of weather data accuracy on the thermal energy demand of a building. A case study of a new collective household (block of flats) located in Brasov City, Romania (45°67′ N; 25°60′ E and 598 m altitude), will be analysed using weather data interpreted with the Meteonorm software as input data in the TRNSYS software, in order to create various scenarios and to assess the technical solutions from the point of view of their feasibility and degree of acceptance.

Recent developments in solar-thermal energy conversion systems are focused on obtaining solar selective absorber materials with high selectivity and durability and asked for cost-effective and environmentally friendly synthesis techniques (e.g. sol-gel and chemical spray pyrolysis). In this context, the paper gives an overview on the state-of-the-art of the research reported till now on different types of black and colored absorber coatings for solar thermal collectors obtained world-wide. Some results obtained by the group active in the R&D Centre Renewable Energy Systems and Recycling are also reported and they are related to the development and optimization of black (NiS_x) and red (Fe₂O₃) absorber coatings, as active components in solar thermal collectors. These results are considered promising for novel, market-competitive solar-thermal collectors, with increased architectural acceptance, for facades integration in Nearly Zero Energy Buildings.

A large variety of methods and techniques are nowadays used to protect the flat plate solar-thermal collectors against overheating occurring during stagnation periods. The overheating leads to increased temperatures in the collector over the design values and negative effects on the absorber plate conversion efficiency, fast aging of system components and heat thermal fluid degradation can be involved, reducing the collector durability, safety and reliability. Many of the known solutions for avoiding overheating are applied only after the heat was generated and thus the thermal stress is still acting on the collector. The authors proposes the new approach of inverse tracking that allows to minimize the input solar radiation coming into the collector in stagnation, consequently limiting the heat production and implicitly the collector’s temperature. The procedure of inverse tracking is proved in the paper as an efficient and affordable solution for protecting against overheating the already tracked collectors, based on theoretical results well complying with experimental data registered in an outdoor testing setup.

Solar energy is commonly used in heating systems as unconventional heat source. Assuming that in low solar radiation day, temperature obtained from collectors haven’t desired value for space heating, presented paper reveal the solution of a heat pump system, to satisfy heating demand, using the heat accumulated in active collectors period. The system considered work in both hypotheses, firstly in two distinct periods, charging and discharging of accumulated energy, and secondly in a mixt activity when the heat pump can start working in same time with heat accumulation due to collectors running. Day parameters, in terms of solar radiation and external ambient temperature, will be used to simulate the system functioning and different results are presented to reveal the working conditions, the energy balance between solar and electrical energy used by heat pump and advantages of such system. High COP_CD for 2 March was obtained, with values greater than 7.85 for 120 L/m2 specific volume.

This work takes into account the implementation and analysis of a Fuzzy Logic Controller (FLC) based on Maximum Power Point Tracking (MPPT), in order to optimize the output parameters and efficiency of a photovoltaic system (PV), as well as its integration in specific applications of LED lighting. The obtained results prove the effectiveness of the FLC and MPPT able to reduce fluctuations in terms of output parameters and to have a quick response for electrical load against variations of solar radiation. By this approach the complex PV system behavior was analyzed on short, medium and long term.

Since the transient effects produced by clouds are manifest at sub-minute intervals, the accurate assessment of the performance of photovoltaic and solar-thermal systems requires high temporal resolution solar irradiance data. Different statistical quantifiers that describe the variability in solar irradiance time-series have been developed for characterizing the solar radiative regime over a given time interval. In this paper, two improved quantifiers for characterizing the stability of the solar radiative regime are proposed and assessed in relation to the traditional ones. A comparative study on the ability of these indicators to classify the days according to their stability is performed. The conclusions are illustrated with measurements performed on the Solar Platform of the West University of Timisoara, Romania at equal time intervals of 15 s.

Graphene as a single-atom-thick honeycomb lattice of carbon atoms has extraordinary optical and electrical features like high electron mobility (100 times greater than silicon). This makes it an attractive material for applications in photovoltaic devices. However, such extremely conductive quality negatively impacts on life-time efficiency in photovoltaics’ life cycle, when accordingly incorporated. The present challenge is to design and exploit semiconductor-graphene (SG), with controlled conductivity that assuring the desired energy conversion also maintains the long life using photovoltaics. Accordingly, two new forms of graphene are studied and employed, as new classes of n-doped, and p-doped semiconductors, so producing the so called, e-SG (electron-type semiconductor graphene, based on topological defective Graphene, as appeared by inherent Stone-Wales topological rotations in pristine Graphene 0-G) and h-SG (hole-type semiconductor graphene, when the structurally defective graphene is present), see figure. This way, the new controlled photovoltaic systems may be composed from various layers of pristine and semiconductor graphenes, passing from the fashioned generation of i-/p-/n-semiconductor based heterojunctions photovoltaics to the new generation of e-/h-SG controlled photovoltaics based on defective semiconductor graphenes - for a long-life use. The efficiency of photovoltaic materials with 0-G, e-SG, and h-SG heterojunctions may be explored by using computational quantum chemistry methods.

One of the greatest concerns nowadays is the growth of the world population. This is the main reason for the continuously increase of the electrical and thermal energy demand and consumption. It is a fact that the reserves of fossil fuels are limited and the exponentially pollution expansion imposes the development and the implementation of renewable based energy production technologies. Thus, the solar energy use represents one of the most promising of the available answers. The solar energy conversion into electricity or heat for remote area applications with different functionalities imposes the design and implementation of transportable (mobile) based on stand-alone photovoltaic modules and solar thermal systems. The paper evaluates the availability of the solutions for this type of products. The research formulates a set of design criteria through constructive and functional design quality requirements meant to generate novel concepts for mobile solutions. The paper proposes several concepts for deployable mobile units for photovoltaic and solar thermal conversion systems. The concepts of mechanisms suitable for deployable PV and solar thermal arrays are developed through embodiment design by using 3D CAD tools. The analysis and the conceptual design process results lead to the conclusion that the use deployable/transportable systems is covering a wide range of applications starting with telecommunication systems up to domestic lighting, heating etc., washing facilities and several concepts are proposed in the paper.

The paper focuses on the sustainable recycling of silicon-photovoltaic (Si-PV) modules by developing innovative composites entirely based on wastes of plastic materials (PVC, HDPE) and rubber, through low cost compression molding technique. In the first part of this study low amount of Si-PV modules powder (up to 3% mass weight) is embedded in polymer matrix and the interfacial and mechanical properties are investigated; two series of samples being obtained, the first Si-PV module without glass and the second one with all Si-PV modules (so including the glass cover of the PV module). The results have proved that the samples series with all Si-PV module powder exhibits higher mechanical performance (2.4 N/mm2 in tensile strength, Young’s modulus of 17 N/mm2) than Si-PV module without glass. In the second part of this study, up to 45 wt% of all Si-PV modules is incorporated in the polymer matrix. The output properties were measured in terms of tensile, compression and impact strength. The structural and conformational modification were evaluated by using Fourier Transform Infrared Spectroscopy (FTIR), the crystalline structure with X-ray diffraction (XRD), while surface morphology was studied by AFM and SEM techniques. The best mechanical properties were recorded for sample with 30% Si-PV with tensile strength of 2.02 N/mm2 and 45% Si-PV composite with compression strength of 39.35 N/mm2. Therefore, novel mechanical performance composites with recycled Si-PV modules could be designed for specific applications.

In this study a method for cost-efficient investments in PV generators at residential buildings has been presented. It takes into consideration all the initial investment and maintenance costs as well as the potential benefits, based on the mean hourly solar energy production for each month of the year in Ruse, Bulgaria. The variation of the net present value as well as the return on the investment are investigated for different scenarios, using a typical daily energy consumption distribution at residential buildings. The obtained results show that for properly sized installations the investment could pay off for approximately 8 years. On the other hand the annual money loses from oversized investments increase significantly and could be approximated with a quadratic equation.

The paper presents the idea of an extensive study, starting on the one side from the main features of molecular machines and on the other side from the applicability of Fredholm integral in electrochemistry. To this aim, the chemical reactivity could be expressed as a link between electronegativity (χ), number of exchanged/carried/transported electrons/charges (N) and the total energy of the system, dynamically evolving under potential V, respectively through the differential equation $$ \chi \, = \, - \left( {\partial E/\partial N} \right)_{V} $$ and/or by its integral form $$ E\, = \, - \int {\chi \left( N \right)_{V} dN} $$. This way, the complementary electrochemistry processes, i.e. electrode interfaces’ processes (such as deposition, corrosion, oxidation, reduction processes, etc.) and the electrolyte solution phenomena (diffusion, dispersion, recombination processes, etc.), may be either interchanged and/or separately controlled. In this context, one may employ the conceptual mix between electronegativity (chemical reactivity) driving the charge transfer in an electrochemical cell with the molecular machine’s inner conversions and light activated features, the so called modular electrochemical reactivity laws are established. Remarkably, such modular controlling of electrochemical processes applied to self-organized molecular machines may control and eventually enhance the life-cycle of photovoltaics, by designing the appropriate electro-molecular modular photovoltaics machine with the inner electrochemistry modularly controlled.

An objective and more accurate assessment of a photovoltaic (PV) electric system efficiency can be achieved through continuous monitoring of electrical parameters of this for a long period of time (at least one year) and correlating the results with the local particular conditions such as the geographic position (solar irradiance and incidence angle of the radiation flux, day length, number of hours of sunshine on the sky) but also other random weather conditions and, finally, taking into account all the technical-economic details specific for the domain. According to the results presented in the paper, a PV system with 50 kW nominal power, installed in the area of Banat/Romania may provide a considerable amount of energy (55629 kWh/year) that can cover largely the consumption of the building under study. For the summer months, from May to September, the system was able to ensure the whole energy for household consumption. The conclusions drawn in the paper could be extended to all regions from Romania benefiting from solar energy at radiation intensity over 1300 kWh/m2/year.

Proper knowledge of the I-V characteristics of a PV module is a key requirement for accurate estimation and forecast of energy production. By using the scarce information provided in the manufactures’ datasheet (short circuit current, open circuit voltage and the maximum power point), the mathematical description of the I-V characteristic is always a challenge. In this paper two procedures for extracting the I-V characteristics in standard test conditions (STC) are discussed. The procedures, based on the Taylor’s series expansion of the current equation, are developed within the frame of the one diode model. The results are assessed by using the datasheets of four different crystalline PV modules, commercially available. The estimated parameters are also compared with the ones previously reported for the same PV modules. Generally, the results show that while the models reproduce accurately the I-V characteristics, the parameters values experience a large dispersion.

Part of the renewable energy systems (based on solar, wind or hydroelectric power) generates electricity in an intermittent way, depending on the weather conditions that are difficult to predict and control. These disadvantages can be overcome by integrating two or more renewable sources that can counterbalance each other. In this case, the hybrid systems based on combinations of renewable energies are preferred to meet the required energy. These systems are often used in remote areas, but their design and analysis are difficult to be performed due to the variability of the renewable sources. A possible option for the off-grid systems can be the combination/operation of PV modules (PV platform) with one or more wind turbines in parallel. The paper presents two algorithms for the design and operation of an off-grid hybrid system, whereby electric energy is obtained from the conversion of solar and wind energy, with a conventional generator as a backup source. The algorithm is exemplified in the case study: the energy supply of a photoreactor used for wastewater treatment. Further, conclusions and recommendations for the design of PV-wind hybrid systems are formulated based on the previous results.

Renewable energy conversion systems require high performance DC-DC power converters, for power flow control between the primary energy sources, storage elements, different DC buses and loads.For high conversion voltage ratio, new hybrid structures can be used for energy conversion in single or bidirectional power flow, obtained by introducing commutated inductive and capacitive cells in the buck and boost DC-DC converters. In these new configurations, the voltage conversion ratio is larger, at the same duty cycle, compared with the classical converters. In the same time, some advantages are obtained regarding the active components voltage and current stresses.The paper presents a synthesis of the author contributions in two DC-DC hybrid converters structure study and implementation.PV and wind energy conversion systems and DC microgrids, are the applications where these converters were implemented in order to prove the proposed structures viability.Circuit diagrams, analytical descriptions, and experimental results are presented, regarding the analyzed hybrid converters and their applications.

Considering the recent pressures in the energy sector at global level, in close relation with the conventional fuel availability, climate change, public interest and the overall debate for more sustainable energy sources, there is an acute need for instruments, capable to identify and measure in a coherent framework how various changes in the energetic systems lead to progress/challenges, in terms of environmental impacts and sustainability. In this context, Life Cycle Assessment (LCA) is a standardized methodology, capable of analysing complex systems, as well as to identify and quantify various environmental impacts of products for their entire life cycles. The main objectives of this study are to perform a life cycle evaluation of the Romanian energy sector for electricity production, in order to identify, quantify and update the associated environmental impacts and to investigate the sustainability of future scenarios. The LCA is focused onto 1 kWh of electricity produced in Romania, considering the indigenous resources mix: coal and gas-fired power plants, hydropower, wind turbines, nuclear power, solar panels and biomass, as well as imports and exports. The assessment is based on the ReCiPe impact assessment methodology, which enables the use of 18 environmental impact categories. By applying the LCA methodology, the Romanian energy mix environmental impact profiles can be compared for 4 years: 1990 (reference year), 1997, 2010 and 2015. Furthermore, the 2030 and 2050 scenarios were analysed. The results show how the changes in the electricity production mix have positive changes in the environmental profile.

An efficient conversion of kinetic energy of river water into mechanical or electrical energy without building barrages is provided by micro-hydropower stations. Increased efficiency is achieved by an optimum position of the blades with hydrodynamic profile. The micro hydro power plant is posted in the river water flow. The position of blades compared to the water level is ensured by the Archimedes forces that react on the floating blades. The efficiency of the micro-hydro power stations as conversion systems of renewable energy sources kinetic energy of flowing river depend mostly on profiles of the hydrofoils used in the rotor’s construction for interaction with fluid. The main goal of this paper consists in the elaboration of the modified hydrodynamic blades with modular structure, and based on them of the turbines with increased conversion efficiency. According to the opinion of authors, the constructive solutions of the micro hydro power plant presented in this work correspond to a great extent to the requirements advanced to the performance hydrodynamic rotor. This fact imposes the designing and execution of some experimental prototypes, which would validate the expectations. The industrial models of micro hydro power plant with modified hydrodynamic rotor and with indicated power of 4 kW have been projected, and fabricated. In present the hydro power plant are in testing stage.

The wind energy conversion systems could play a significant role in the production of mechanical, electrical and thermal energy in the Republic of Moldova, in particular for providing the individual consumer with energy using wind turbines of low power (until 30 kW). In order to redress the situation of the energy sector, the Government of the Republic of Moldova, through the agency of the Supreme Council for Science and Technological Development (Academy of Sciences of Moldova), initiated several National Programs, addressing the elaboration of renewable energy conversion systems as well. This paper describes some research and application of the industrial prototypes of horizontal axis wind microturbines with power of 10 kW, which include some new elements comparative to the already existing systems (wind orientation mechanism, thermal generator). These wind turbines are intended to be installed in different geographic areas of the Republic and tested. Some results are included in this paper.

The project sets to develop a new energy autonomous system based on electrochemical sensors for detection of different ionic species in natural water sources and ultra-thin solar cells (UTSC). It focuses on three directions: high efficiency, new materials in solar energy harvesting and fabrication of small UTSC and the power stabilizing device able to supply the needed voltage to the sensors and electronic module; new microsensors for detection of nitrites/nitrates and heavy metals in water; low cost autonomous energy system integration and fabrication. The harvester will include a UTSC (<300 μm thick), a dedicated storage, a power stabilizing device. The materials to be optimized are SnO₂, TiO₂ and ZnO for the sensors while for the solar cells two routes are proposed: (a) TiO₂, ZnO and CuxS, and (b) CZTS, CuxS and TiO₂. Polymeric membranes deposited on the working electrode will act as sensing material for the ionic species mentioned. Bacterial flagellar filaments will be investigated and engineered as sensitive biolayer for heavy metal detection. The project will provide a technology demonstrator and water monitoring system prototype.

Recent research on heterogeneous photocatalysis is focused on producing new efficient TiO₂ - based photocatalysts deposited on fabrics with increased adaptability and facile implementation as self-cleaning/self-decontamination, antimicrobial fabrics or in other photocatalytic applications as wastewaters treatment or air purification. This paper gives an overview on the R&D results obtained within the Renewable Energy Systems and Recycling Centre on the development of stable photocatalytic dispersions for fabrics coating, based on sol-gel TiO₂. The challenges in the components development - the photocatalytic nanoparticles, the dispersion and the coated fabric are discussed considering TiO₂ Degussa P25 based products as reference. Sustainable, optimized solutions in terms of stability and functionality (photocatalytic properties) are provided. Photocatalytic fabrics deposited at room temperature by spraying from polyethylene glycol or chitosan stabilized dispersions based on ultrasound assisted sol-gel TiO₂ best meet the stability criteria and the photocatalytic properties (efficiency higher that 75% in methylene blue removal and over 95% in mustard gas decomposition) Recommendations in the design of self-cleaning/self-decontamination fabrics are provided.

The paper is a comprehensive review on the wastewater treatment processes focused on the energy performance and energy efficiency. Extensive studies reported in literature, including results from our Renewable Energy Systems and Recycling R&D Center, are selected to give a clear view on the advantages and disadvantages of traditional and advanced wastewater treatment processes, from the energy consumption perspective. The challenges in terms of energy saving, process optimization and sustainable materials are presented. The traditional processes used in the wastewater plants have limited efficiency for removing the new organic pollutants and usually require environmental aggressive procedures (e.g. chlorination). Advanced wastewater treatments using common raw materials and renewable energy sources represent a sustainable answer to the problem raised by the resilient organic pollutants. So, the paper outlines that advanced wastewater treatment represents a suitable part of the strategy for planning nearly zero energy communities (nZEC).

Recycling the biodegradable waste by composting represents a sustainable solution for developing new ecological compost-type substrates, useful both as biofertilizers and as sorbents for the removal of heavy metals from wastewaters. By this paper we aim to present an overview of our studies related to using composted biomass from biodegradable wastes, as viable solution for biofertilizers or sorbents for heavy metals removal from the environmental. The novelty of our studies consists of the new materials that were prepared by composting together different biomass wastes. Aerobic fermentation was used to obtain sixteen different composts from vegetables waste, sewage sludge, beech sawdust and beech ash, in different mixing ratio, and the composting process was monitored. Based on their composition, three of these mature and stable composts were selected, while their capacity as nutrients and suitability as bio-fertilizers were analyzed in terms of C/N ratio, germination tests. Furthermore, one of these composts was also demonstrated to be suitable as low-costs sorbent, specifically to remove heavy metals from polluted waters. For this application the topography and morphology of compost substrates were determined, before and after sorption of metal cations. The sorption parameters (contact time, ratio of wastewater volume: sorbent compost mass) were optimized. Both, kinetic and thermodynamic sorption mechanisms were discussed and the results were further correlated with the structural properties of the compost substrate. The advantaged of biodegradation wastes by composting different raw biomaterials for preparation of ecological soil fertilizers and sorbents to remove heavy metals from contaminated waters, as low cost and environmental friendly solutions were also discussed.

The composite materials were obtained from fly ash, collected from the electro filters of the Central Heat Power Plant from Brasov, Romania. This fly ash doesn’t aggregate in water and can form a new composite together with TiO₂ and Al₂Si₂O₇.2H₂O. The raw ash combined with titanium oxide and silicate was modified by hydrothermal treatment under alkaline conditions. The new composites were characterized in terms of crystallinity (XRD), surface properties such as: morphology (SEM, AFM), wettability (contact angle measurements) and specific surface (BET). Simultaneous removal of heavy metals (Cd2+, Cu2+), dye (methylene blue - MB) and surfactant (sodium dodecylbenzene sulfonate - SDBS) pollutants was investigated by adsorption and photodegradation ontwo composites (FUS-DAl1 and FUS-DAl2). The adsorption parameters (contact time and amount of substrate) were optimized for obtaining a maximum efficiency and were further used in kinetic studies, comparatively discussed with the photocatalysis optimized operating parameters. The UV-photocatalytic properties of the obtained materials were evaluated in pollutant systems containing three (Cd2++MB+SDBS, Cu2++MB+SDBS) and four pollutants (Cd2++Cu2++MB+SDBS).

Resource efficiency is seen as a constituent of sustainable production and consumption, where yesterday’s waste is today’s raw material. In this context, our main goal is to track eco-innovative ways in the framework of circular economy to reuse production waste as eco-designed smart new products. The corrugated board and cardboard packaging manufacturing was found as one of the most available and proficient industries in applying the circular way to extend the life cycle of raw materials and save energy by combining economic and environmental targets in an eco-efficient manner. We have identified the need of a Romanian Manufacturer (RM), equipped with modern facilities and technologies to produce corrugated board and packaging, and also opened for knowledge transfer focused on the generation of economic benefits and environmental advantages by closing the production loop through reusing the production waste generated in the form of cardboard strips, edges and other production waste. Then, we developed and applied a challenging work-plan to create a new environmentally friendly and sustainable re-engineered product required by the market, by extending cardboard waste life cycle based on an eco-innovative approach, put in practice by following eco-design principles. In order to enable RM decision making process, we have performed Life Cycle Analysis (LCA) and Life Cycle Cost Analysis (LCCA) to identify and assess: (i) the environmental impacts induced by the reuse of waste production as raw materials for the product redesigned based on eco-innovation and eco-design concepts; (ii) the total cost performance in terms of materials and energy of the alternative proposed to be implemented in corrugated board and packaging manufacturing. These tools would enable the valorization of production waste so as to close the loop and extend the life cycle of cardboard in an eco-efficient way. In perspective, these production wastes are intended to be revalorized as subassemblies for building sectors.

Sustainability is a term that defines the ability of a system to function for an indefinite time. From the definition given in the Brundtland report in 1987 - as the “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” - the approach received different nuances and new facets, as today the term refers not only to the environmental development - that includes the natural resources - but also to the economic, social, cultural, safety aspects. Sustainability cannot be accomplished by actions coming from only one direction, all aspects that were mentioned above having to be studied and matched in a sustainable approach. Why this introduction? Because the architectural approach needs to be a complex one, that deals not only with building materials and building principles but also with traditions, culture, history, economy, sociology. In a very large sense, the architect is an educator and a mediator in the contemporary society and not only a builder. This paper intends to put a light on the relation between architecture and sustainability and the role of the architect in the contemporary society.

According with the Research and Markets [1] analysis, the growing demand of reliable online learning solutions and technologies is the driving force of Massive Open Online Course (MOOC) market. The industry forecast for MOOC market size is to grow from USD 1.83 Billion in 2015 to USD 8.50 Billion by 2020, at a compound annual growth rate (CAGR) of 36.0%. Adoption of device-based computing, increased connectivity of platform, and emergence of online and collaborative learning and personalization of technology are some of the prominent factors driving the adoption of MOOC platform and services. The authors of this paper intend to share some insights of a recent approved project financed within Kic Innoenergy framework, project EBA, Energy in Buildings Academy, with the main objective to offer a unique online educational offer on Energy Management in Buildings.

Although legal obligations are provided in the National legal framework by transposing the provisions of the 2010/31/EU Directive, the Nearly Zero Energy Building (nZEB) concept does not seem to be easily applicable yet in Romania. One of the main barriers for this consist in the skills gaps experienced by the building sector, the current qualification courses and training schemes being generally not satisfactory and underdeveloped to face the challenge of effective nZEB implementation. This paper presents the preliminary developments of the Train-to-nZEB project, namely the setting up of Building Knowledge Hubs (BKH) for practical trainings of construction workers and specialists for the design and construction of NZEBs. Building on the results of the BUILD UP Skills initiatives and Passive House principles, the BKHs will provide capacity for conducting practical trainings for on-site professionals, high level specialists and decision makers. To a large extent, the BKH training centres aim to satisfy the existing demand for practical training of trainers and teachers, to provide opportunities for organization of courses to certify builders of NZEBs and to update existing skills. As a major functional goal, BKHs will provide courses for continuing qualification and training for architects, engineers and building managers and other building professionals with the goal to improve the existing classroom-based training schemes with practical trainings using the new developed facilities.

The project’s priority is the creation of the knowledge triangle, based on education, research and innovation; which includes collaboration between universities and enterprises, supporting the entrepreneurship, thanks to the support of research. This first choice is motivated by the fact that research, innovation and education, can ensure competitiveness in a global context in which other competitors, such as the emerging countries, can count on cheap labor or primary resources. Moreover, through this project, the idea is to innovate the methodological approach of the sustainable design: innovation means “produce, assimilate and exploit innovations successfully in the socio-economic sector.”PAES Project is focused on the development of vocational training according to high-quality work by sharing experiences, knowledge, skills and international qualifications in a common virtual space, creating a replicable model of cooperation between Training Institutions and Operators of the construction sector. The project, aimed at spreading the Sustainable Building, is perfectly in line with the Europe 2020 strategy that prioritizes sustainable growth: for a more efficient economy in terms of resources, greener and more competitive economy.

It is an undeniable reality that new energy sources and conversion technologies related are “stars” of any energy policy of the XXI-th century. Few people know, however, that the between the conversion technologies, the most lifetime long technology is hydro (estimated between 50–100 years). With the condition that power output should not be less than 80% of rated power, lifetime of a wind turbine is estimated at 20 years and for solar panels at 25 years while estimation for hydro technologies is between 50 and 100 years. Also, corroborating prices per MWh installed and lifetimes, maintenance programs that we propose to implement only proactive type of maintenance, and that means monitoring and optimization. In this article the authors highlight the fact that, in the context of sustainable development is necessary to pay more attention to education in the field of renewable energy. For more than a decade in Romania, in the energy engineering field, is studying Renewable Energy Sources, in particular by approach the systems and equipment to capture and converse to renewable energy, sustainable development and resource management, the environment and ensuring health ambient space with RES etc. The authors show that is required a new approach in academic education regarding RES, focusing on operation and maintenance of capture and conversion systems, with new technologies and future trends in the field. The new methods and schemes in terms of educational approach, to address the needs of 21st century sustainable energy are proposed.

Considering that the impact of the irresponsible use of the planets’ natural resources became visible, combined with the effects of the pollution produced by the unreasonable exploitation of resources, the European Union decided through the Directives 2010/31 and EU 2012/27 of the European Parliament and the Council to issue documents of commitment of the Member States for assuming the overall program of meeting the requirements that, after December 2018, all buildings belonging or managed by public institutions to be nZEB, as well as all new buildings constructed later than December 2020. As a member of the European Union, Romania pledged to comply with nZEB building concepts by 2020 for all newly constructed buildings. Despite this, we find that in practice, throughout the country, the concepts of designing and building responsible according to sustainable principles are not yet widespread and respected. The sad reality on the field is that professionals (both designers and builders) are not even aware that it is mandatory to produce such buildings. Meanwhile, good quality architecture is awarded and promoted in Romania but somehow the sustainability of the design doesn’t usually make it to the criteria list. Since the theory behind the building of sustainable houses should be rapidly assimilated and that the change of this situation overnight is not possible, we consider that any form of communication and explanation of the European legal framework and of the possible approaches of meeting the Energy Performance of Buildings Directive’s requirements is necessary and also urgent. This paper presents principles of sustainable buildings and the state of the art in Romania.

A multi-functional product is covering more functions during its use stage. Usually, these functions are achieved by using several products. Starting with a short presentation of the ecodesign principles versus the traditional design, defining the lifecycle of a product, the paper demonstrates that the impact of the multi-functional products on the environment is lower than in case of using single function products to fulfil the same functions: less resources, less waste and emissions during the production and packaging, transport and distribution stages and at the product end-of life, less waste to be processed. During the multi-functional product use stage, the energy used is comparable with the sum of energy resources needed to act the corresponding single function products. The paper presents as a case study a new and fresh design for a coffee maker to take over the functions of three other devices: classic infusion coffee maker, syphon coffee maker and tea maker. The benefits of this new device, branded as “BRWR”, concerning its relation with the environment, is appreciated as a good example of a multi-functional product.

Lately, it has been demonstrated that the use of “serious game” in the education of children and youth can open new opportunities for transmission of information and development of technical skills. For this, increasingly more educational environments apply to the transmission of information, knowledge and technical systems development by making practical or virtual applications, like “serious game”, in which our children or students can dynamically participate. In this paper, in the first part, the principles of the concept of partnership development through mentoring by which wanted students involvement in educational effective and understanding practical activities, also application aspects of environmental protection and efficient use of sources of green energy are presented. In the second part of paper, the concept was materialized in the design, implementation and use of checkerboard constructed from recoverable materials and green energy sources. Youth participation, both in design and in finding practical solutions for construction and the propagation of information about the environment or energy sources, for young students having the same age with them were the main objectives of this approach. Chess, with all its qualities became the mean by which can realize the objective of the educational process. In the final part of paper, conclusions recorded from carrying out of this project are presented.