Proceedings, 2020, WEF 2020

This paper presents a critical and analytical description of an ongoing research program aimed at the implementation of an expert system capable of monitoring, through an Intelligent Health Control procedure, the instantaneous performance of a cogeneration plant. The expert system is implemented in the CLIPS environment and is denominated PROMISA as the acronym for Prognostic Module for Intelligent System Analysis. It generates, in real time and in a form directly useful to the plant manager, information on the existence and severity of faults, forecasts on the future time history of both detected and likely faults, and suggestions on how to control the problem. The expert procedure, working where and if necessary with the support of a process simulator, derives from the available real-time data a list of selected performance indicators for each plant component. For a set of faults, pre-defined with the help of the plant operator (Domain Expert), proper rules are defined in order to establish whether the component is working correctly; in several instances, since one single failure (symptom) can originate from more than one fault (cause), complex sets of rules expressing the combination of multiple indices have been introduced in the knowledge base as well. Creeping faults are detected by analyzing the trend of the variation of an indicator over a pre-assigned interval of time. Whenever the value of this ‘‘discrete time derivative’’ becomes ‘‘high’’ with respect to a specified limit value, a ‘‘latent creeping fault’’ condition is prognosticated. The expert system architecture is based on an object-oriented paradigm. The knowledge base (facts and rules) is clustered—the chunks of knowledge pertain to individual components. A graphic user interface (GUI) allows the user to interrogate PROMISA about its rules, procedures, classes and objects, and about its inference path. The paper also presents the results of some simulation tests. Full article

In order to support the development of a novel linear engine generator (LEG), the characteristics of ammonia/hydrogen premixed combustion are studied by using a detailed chemical kinetics mechanism. The ammonia combustion mechanism is identified among several mechanisms and validated with published experimental data. A parametric analysis is carried out under LEG typical working conditions to study the effects of equivalence ratio (0.80–1.60), hydrogen blending ratio (0.0–0.6), initial temperature (300–700 K) and initial pressure (1–20 bar) on premixed laminar flame speed, ignition delay and key flame species concentrations. It is shown that an equivalence ratio of around 1.10–1.20 is beneficial to both ammonia flame stability and lower NOx emission. Ignition delay is reduced with the increase in hydrogen blending ratio, initial temperature and initial pressure. At a certain initial temperature and initial pressure, the effects of hydrogen blending ratio can be negligible for over 50% hydrogen in the fuel. Under higher pressure (>10 bar), the initial pressure has a minor influence on the ignition delay reduction. It is also found that the high-pressure high-temperature environment contributes to reducing NO emission considerably in ammonia/hydrogen combustion, which implies the potential of a low NOx LEG fuelled by ammonia/hydrogen. Full article

In the recent past, several examples of the application of Exergy Analysis (ExA) to Very Large Complex Systems, including entire countries, have been published, and it can be fairly said that—while the goals of the individual authors were completely consistent—the results, the conclusions and the recommendations diverge. There are several contingent reasons for this, but the underlying problem is that a purely thermodynamic analysis cannot reproduce the complex influence that monetary, social, political and technological factors have on the purely “material” or “energetic” streams. Clearly, ExA represents a substantial improvement with respect to the “Material and Energy Balance Reports” published annually by most industrialized countries, because the exergy flow diagram unequivocally demonstrates how and at what penalty the primary exergy inflow (fossil fuels, renewables, ores, harvested food and other primary goods) is transformed into final energy, such as diesel fuel, electricity or other commodities. The issue here is, though, that the so-called Externalities (Capital, Labor and Environmental Effects) are, in spite of some opinion to the contrary, completely left out of the picture. It turns out though that ExA can be extended by including the exergy equivalents of the externalities. The theory is called Extended Exergy Accounting (EEA) as a reminder of the inclusion of monetary, labor and environmental “exergy costs” in the global budget. The scope of the study presented in this paper is twofold: First, the introduction of a novel approach based on the exploitation of a very disaggregated dataset, in order to perform the EEA of a whole country; second, the analysis of the results of the application of the method to the Italian society, over a five-year (2013–2017) window of observation, to extract new insights that could be useful to critically assess the trend of the exergy destruction of Italy vs. that of the GDP. Full article

Preheated Schizochytrium sp. raw microalgae oil (MAO) was evaluated as a fuel in a single-cylinder four-stroke diesel engine to produce a comparative study of MAO and diesel oil (DO) critical parameters. In particular, brake power, brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), in-cylinder pressure (CP), exhaust gas temperature (EGT), both nitrogen oxides (NOx) and carbon monoxide (CO) emissions were investigated. Additionally, an engine durability test for longevity was undertaken over a 30-h period, using raw MAO as the fuel. The study demonstrated that the preheated MAO could be successfully used in a diesel engine smoothly. The use of MAO reduced the engine brake power by 26% and increased brake-specific fuel consumption by 20%. The most significant finding from this research study is that there was a significant reduction in NOx and CO emission by 42% and 60% when using raw MAO, respectively. Therefore, these findings demonstrate that algae oil is a highly credible fuel for use in diesel engines and offers a promising solution to diesel engine emissions. Full article

The paper discusses the principle of power amplification, as it can be found in many systems powered by PV panels and buffered by batteries. Under different categories of application examples, one is compacting containers for plastic or other waste materials. The main goal of such systems is to supply high-power intermittent systems from low-power sources. The studied example discusses an energy harvesting system using a low-power solar PV collection system dedicated to energize a specific application, sequentially operated at high power. The transformation of the power level is achieved using intermediary storage, where the charging sequence is characterized by a very low power level for a longer time, followed by a shorter discharge sequence of the storage means with a much higher instantaneous power. The performance of the PV harvesting system is discussed from the point of view of its energy efficiency. Several solutions are discussed, and finally, a new two-stage harvesting system is introduced. The requirement of a multistage amplification system is related to the power amplification ratio itself. The design method for the system relies on the concept of the so-called “modified Ragone representation”, MRR, that is shortly introduced in the paper. A prototype realization of the two-stage system is also presented. Full article

This research aims to test the feasibility of a prototype of a newly designed thermal engine for a hybrid propulsion vehicle. This study consists of the implementation of an innovative supercharger for city car ICE (900 cc). The preliminary proposal presented here is to mechanically disconnect the compressor/turbine device, supporting the rotation of the compressor with a dedicated electric motor and connecting a turbine to a generator. Mechanical decoupling will allow both machines to be designed for operating closer to their maximum performance point, for most of the expected real field of operation. Specifically, the turbine is likely to have a slightly lower rotation speed than the original group and will, therefore, be slightly larger. The advantage is that, while in the current supercharger groups the surplus at high regimes is discharged through the waste-gate valve without expanding in a turbine, in the configuration proposed, all the energy of the combustible gases is used by the turbine to generate electrical power that can be used where required. Once the motorization of the vehicle (999 cc) has been fixed, the two turbomachines will have to be studied and designed, looking, where possible, for commercial components. Finally, a CFD will be needed to verify the validity of the choice, followed by careful experimentation campaigns. Full article

The building sector plays a vital role in Switzerland’s climate policy. In order to support the energy transition in the building sector, Rolle, a suburban area located along the shore of Lake Geneva is considered in this study to understand the promising future scenarios for integration of renewable energy technologies. The area is clustered into 12 clusters and a distributed energy system is designed for each cluster. Subsequently, three energy systems with contrasting densities are taken for further comparison to understand the impact of urban density on the design of the distributed energy system. The study reveals that urban density will influence the peak as well as the annual energy demand of the energy hubs. The study reveals that the energy technologies used in the energy hubs are strongly influenced by the capacity of the system (peak and annual energy demand). Energy systems with higher capacities are less sensitive to the market changes when compared to the systems with lower capacities (leading to sparse suburban areas). Full article

The continuous quest for improving the performance of heat exchangers, together with evermore stringent volume and weight constraints, especially in enclosed applications (engines, electronic devices), stimulates the search for compact, high-performance units. One of the shapes that emerged from a vast body of research is the disc-shaped heat exchanger, in which the fluid to be heated/cooled flows through radial, often bifurcated, channels inside of a metallic disc. The disc, in turn, exchanges heat with the heat/cold source (the environment or another body). Several studies have been devoted to the identification of an “optimal shape” of the channels: Most of them are based on prime principles, though numerical simulations abound as well. The present paper demonstrates that, for all engineering purposes, there is only one correct design procedure for such a heat exchanger, and that this procedure depends solely on the technical specifications (exchanged thermal power, materials, surface quality): The design, in fact, reduces to a zero-degree of freedom problem! The argument is described in detail, and it is shown that a proper application of the constraints completely identifies the shape, size and similarity indices of both the disc and the internal channels. The goal of this study is not that of “inventing” a novel heat exchanger design procedure, but that of demonstrating that -in this as in many similar cases- a straightforward application of prime principles and of diligent engineering rules may generate “optimal” designs. Of course, the resulting configurations may be a posteriori tested as to their performance, their irreversibility rates, their compliance with one or the other “techno-economical optimization methods”, but it is important to realize that they enjoy a sort of “embedded” optimality. Full article

The decarbonisation of the energy sector is probably one of the main worldwide challenges of the future. Global changes urge a radical transformation and improvement of the energy-producing systems to meet the decarbonisation targets and a reduction of greenhouse gas emissions. The hydrocarbon industry also contributes to this transition path. In a mature stage of oil and gas fields, the production of hydrocarbons is associated with formation waters. The volume of produced water increases with the maturity of the assets and the geothermal repurposing of depleted oil and gas wells could be an alternative to the mining closure. In the described transition scenario, the geothermal energy seems very promising because of its wide range of applications depending on the temperature of extracted fluids. This flexibility enables us to propose projects inspired by a circular economic vision considering the integration in the territory and social acceptance issues. In Italy, since 1985, 7246 wells have been drilled for hydrocarbon, of which 898 are located onshore with a productive or potentially productive operational status. This paper presents a preliminary investigation of oil and gas fields located onshore in Italian territory based on the available information on temperature distribution at different depths. Then, taking into account the local energy demand, existing infrastructure, and land use of the territory, a conversion strategy for the producing wells is proposed for three case studies. Full article

In recent years the climate change issue, coupled with the concern of resource depletion, is favoring the blossoming of renewable energy conversion systems. Particularly, the development of new technologies for the combustion of biomass has drawn special attention to the possibility of coupling thermoelectric modules with stove-fireplaces. The current thermoelectric generators have many attractive points, such as a solid structure, absence of noise, and no maintenance required; however, due to their very low efficiency (4–8%), they are still economically non-attractive. However, if the modules are applied to a heat source, which otherwise would be wasted, the interest in the solution certainly grows. In this study, an exergy analysis of a stove-fireplace coupled with thermo-electric modules is performed, with the aim of identifying the critical issues of the overall system. The obtained exergy efficiency of the whole system resulted to be of 36.2%. A sensitivity analysis on the main parameters affecting the second law efficiency of the system (such as number of cells, dimension of the stove fireplace, heat input …) is also carried out. Full article

Currently, the Radio-Frequency Corona Ignition systems represent an important solution for reducing pollutant emissions and fuel consumption related to Internal Combustion Engines, while at the same time ensuring high performance. These igniters are able to extend the lean stable limit by increasing the early flame growth speed. Kinetic, thermal, and ionic effects, together with the peculiar configuration of the devices, allow the combustion process to start in a wider region than the one involved with the traditional spark. In this work two corona igniters, namely a Barrier Discharge Igniter and a Corona Streamer Igniter, were tested in a single-cylinder research engine fueled with gasoline at different engine loads in order to investigate the igniters’ performance through indicated analysis and pollutant emissions analysis. For each operating point, the devices’ control parameters were set to ensure maximum energy releasement into the medium with the aim of investigating, at the extreme operating conditions, the capability of the devices to extend the lean stable limit of the engine. The corona igniters were tested on a constant volume calorimeter as well, reproducing the engine pressure conditions at the corresponding ignition timing. The target was to give an estimation of the thermal energy released during the discharge and then to compare their capability to provide high-stability energy. Full article

The Renewable Community Empowerment in Northern Territories (RECENT) project intended to enhance the utilization of unused assets in remote and sparsely populated areas and communities. The objectives were to enhance energy efficiency, implement renewable energy solutions and help communities to have more resilient and energy efficient public infrastructures capable of handling climate change related risks. The nexus approach was used to promote the efficient management of resources, i.e., water, waste and energy, while considering the interdependencies between them. The project developed 25 pilots related to energy, energy efficiency, waste, and water solutions across five Northern Periphery and Arctic Programme (NPA) partner regions (Finland, Sweden, Northern Ireland, Ireland, and Scotland). The project assessed energy generation and reduction potential; investment costs and payback times of the pilots. A sustainability assessment tool was also developed, to assess the environmental, social and long-term sustainability of the pilots. The combined benefit of the 25 pilots was 20 GWh/year renewable energy and saving 6070 t of CO₂/year. The sustainability assessment also highlighted the social benefits to the community. The project established opportunities for new ways of providing environmental goods and services and supporting innovative infrastructures based on the nexus approach of water-energy-waste-land resources. These innovative infrastructures would be based on decentralized systems which allow for synergies between different assets. These synergistic solutions can contribute significantly to the reduction of resource consumption and related emissions and to the sustainable development of European communities. Full article

The properties of the entropy production in convecting–radiating fins were analyzed. By taking advantage of the explicit expression for the distribution of heat along the fin, we investigated the possibility of assessing the efficiency of these devices through the amount of entropy produced in the heat transfer process. The analysis was performed both for purely convecting fins and for convecting–radiating fins. A comparison with standard definitions of efficiency is given. Full article

Solar thermal technologies are already available on the market, and they are robust and relatively cheap. Unfortunately, solar heat is seldom used in the industrial processes, and the main obstacle of solar heat diffusion is often the lack of adequate predictive modelling of solar plant integration that identifies its energy potential, economic feasibility, and environmental benefits. In this paper, we aim to investigate and evaluate the possibility of supplying solar heat to the pasta-drying process located in the northeast of the Italian Alps (“Felicetti”). The methodology proposed is structured with the combination of several software, namely, PVGIS^®, Matlab^®, Dymola^®. The methodology developed is tested, considering solar thermal energy as the primary source, in different geographical contexts. Full article

The objective of this work is to develop a framework related to energy storage systems implementation. The work focuses on a Brazilian scenario and applies information regarding demographic changes, economic, governmental and energy resources studies to establish the opportunities and barriers for a battery deployment in the country. This information is classified into organization, technology, and standards fronts, enabling to schedule the human resources and deal with possible gaps. Besides this, the framework organizes the information to enable a constant review of work fronts and activities, as the implementation scenario changes, and new stakeholders are added. A use case regarding an implementation of a multisource energy system composed by different sources and a battery allows to verify the proposed framework viability. As a result, it is expected that the framework enables medium-sized energy consumers to implement a similar infrastructure, reducing risks and gaps and maximizing the opportunities regarding a battery deployment. Full article

The advance of the distributed generation in Brazil makes it essential to investigate the applications and transformations that the use of these new arrangements may entail. The use of non-centralized generation technologies associated with energy storage is interesting for several sectors of the energy market, even if the market is in the process of maturing these technologies. In the context of the time-of-use rate, these changes have allowed the consumer to use strategies to save energy bill costs, especially when its moment of most considerable consumption coincides with that of the highest tariff. In this paper, a Battery Energy Storage System (BESS) is used to perform commercial peak load reduction in a microgrid in connected mode. The microgrid also has a Photovoltaic (PV) Generator Farm as Renewable Energy Sources (RES) to provide load consumption and also to assist BESS in the peak shaving operation. The modeling and simulation of the system are performed by MATLAB/Simulink. The analysis demonstrates that the peak load reduction produces the expected financial benefits under a Brazilian time-of-use rate known as White Rate, in addition to carrying out the operation in a manner consistent with the technique from an electrical point of view. The software Homer Grid validates the potential savings. Thus, the results showed that the use of energy storage associated with renewable generation under a peak shaving strategy allows greater freedom for the consumer in the face of costs with main grid purchases. Full article

Amongst the various alternatives for hot water production for domestic use, instantaneous heaters are still widely used in many markets such as the Portuguese market. In this system, a gas boiler converts the chemical energy of the gas (Liquefied Petroleum Gas, Natural Gas) to a water stream, as it is used. The complexity of such devices ranges from those with a natural convection to those with full pre-mixing of the air-fuel. The tightening of the legislation targeting these appliances is promoting an increase in efficiency, pollutant emission reduction and an increase in the safety features. The purpose of this work was to test the thermal performance of a water heater prototype with 22 kW of nominal heat output, running on Propane. Changes were made to the plate with orifices that limit the air supply to the burner flutes, where the pre-mixture with the fuel is partially made. Four different plates with different orifice diameters were built and tested in real case scenarios, taking into special consideration the pollutant emission and the fuel consumption verified. From the results, it was concluded that the best configuration in terms of efficiency is the original one, followed by the “−0.5 mm” and “−1 mm” plates. On the other hand, the best plate in terms of CO emission was the “−1 mm” plate. Concerning the plates with larger diameters to the manufacturer’s original configuration, flame instability was verified as a result of the greater primary airflow. Under the same test conditions, it was noted that the introduction of a nozzle into the fan inlet led to the suction of a larger amount of air. Finally, it was also concluded that the reduction in the orifice diameters of the plates reduces the split of primary air, resulting in an increased pressure drop in the flutes and in the overall pressure drop of the system. Full article

The energy production future is dominated by renewable energy sources driven by global warming problems and aiming at the reduction of fossil fuel dependence. Wind energy is becoming competitive with fossil fuels considering its less price and less CO₂ emission production. Wind turbines consist of different types, including Doubly Fed Induction Generator (DFIG) which is a variable speed wind turbine and operates at varying speeds corresponding to the varying wind speeds from the cut-in speed through the rated wind speed to the cut-out speed. In the case of grid failure, the network voltage drops; consequently, the rotor current and DC link voltage increase which leads to damage of the rotor windings and power electronics device. Some protections are applied to the machine in order to help the Low Voltage Ride-Through (LVRT) ability of the doubly fed induction generator. In this root, the crowbar protection circuit is used widely in wind power plants. However, crowbar protection should be sized carefully due to its effects on both DC link voltage and rotor currents. In this paper, a doubly fed induction generator with crowbar protection is studied and the optimum value for the crowbar protection is derived; then, a Simulink model of a doubly fed induction generator protected by a crowbar protection is developed and used to analyze the effect of crowbar protection value on the DC link voltage and rotor currents. The results show a significant improvement in the LVRT ability of the DFIG. Full article

The use of mobile data has increased and will continue to increase in the future, because more data is moving to wireless networks such as 5G. Cooling energy need is also expected to increase in indoor telecom rooms, and can be as high as the equipment’s own power consumption. The world’s first liquid Base Transceiver Station (BTS) was adopted into commercial use in 2018, in Helsinki, Finland. Conventional air-cooled BTS hardware was converted into liquid-cooled BTS equipment. Heat from the BTS was pumped out of the site room, and thus ventilation or air conditioning was not needed for the heat load from the BTS. Heat stored in the liquid was released into the ventilation duct of the building, still providing annual cooling energy savings of 70%, when compared to air cooling. In the future, 80% of the total dissipated energy, 13450 kWh/a in total, can potentially be used for heating purposes. In terms of CO₂ emissions, adapting liquid cooling showed an 80% reduction potential when compared to air cooling. Full article

The geothermal sector has a strength point with respect to other renewable energy sources: the availability of a wide range of both thermal and power applications depending on the source temperature. Several researches have been focused on the possibility to produce geothermal energy without brine extraction, by means of a deep borehole heat exchanger. This solution may be the key to increase the social acceptance, to reduce the environmental impact of geothermal projects, and to exploit unconventional geothermal systems, where the extraction of brine is technically complex. In this work, exergy efficiency has been used to investigate the best utilization strategy downstream of the deep borehole heat exchanger. Five configurations have been analyzed: a district heating plant, an absorption cooling plant, an organic Rankine cycle, a cascade system composed of district heat and absorption chiller, and a cascade system composed of the organic Rankine plant. District heating results in a promising and robust solution: it ensures high energy capacities per well depth and high exergy efficiency. Power production shows performances in line with typical geothermal binary plants, but the system capacity per well depth is low and the complexity increases both irreversibilities and sensibility to operative and source conditions. Full article

The purpose of this work is to determine internal and external factors affecting the cooling energy demand of a building. During the research, the impact of weather conditions and the level of hotel occupancy on cooling energy, which is necessary to obtain indoor comfort conditions, was analyzed. The subject of research is energy consumption in the Turówka hotel located in Wieliczka (southern Poland). In the article, the designer of neural networks was used in the Statistica statistical package. To design the network, a widely used multilayer perceptron model with an algorithm with backward error propagation was used. Based on the collected input and output data, various multilayer perceptron (MLP) networks were tested to determine the relationship most accurately reflecting actual energy consumption. Based on the results obtained, factors that significantly affect the consumption of thermal energy in the building were determined, and a predictive energy demand model for the analyzed object was presented. The result of the work is a forecast of cooling energy demand, which is particularly important in a hotel facility. The prepared predictive model will enable proper energy management in the facility, which will lead to reduced consumption and thus costs related to facility operation. Full article

Similar to many other Western countries, Belgium has committed to internationally set climate goals, such as the reduction in primary energy consumption and the increase in the share of renewable energy production in the total energy mix. Additionally, Belgium has decided to phase out its nuclear energy production, the nation’s largest source of low carbon electricity. In this paper, the role of Belgian business parks and industrial clusters in contributing to the climate goals is investigated, based on the experiences of the authors on several business parks and industrial clusters. The concepts of cogeneration, advanced thermal grids, and local energy communities are discussed and applied on pilot clusters. Their effectiveness towards achieving the climate goals is evaluated, and finally, some policy recommendations are proposed. The results are based on the Belgian situation but are valid for other countries facing similar challenges. Full article

Atmosphere is one of the most significant factors in the thermal decomposition of biomass. In domestic or industrial biomass boilers, ambient oxygen concentration varies through time, which means that the reaction will change from pyrolysis to combustion. In this way, to analyze and compare each thermochemical conversion process, a simple analytical method, the non-isothermal thermogravimetric analysis, is carried out under oxidative (air) and non-oxidative (argon) environments at 10 °C/min and as a function of different flow rates (2 to 150 mL/min). Additionally, this work was complemented by a kinetic analysis considering a first-order reaction to each conversion stage and using the Coats–Redfern method. The effect of the atmosphere on the thermal decomposition behavior was evident. It was observed that the thermal decomposition of pine wood particles varied from three to two stages when the oxidative or inert atmosphere was applied. The presence of oxygen changes the mass loss curve mainly at high temperature, around 350 °C, where char reacts with oxygen. The maximum mass loss rate from experiments with the oxidative atmosphere is 15% higher than in an inert atmosphere, the average char combustion rate is approximately 5 times higher and the heat released reaches levels 3.44 times higher than in an inert atmosphere. Ignition and combustion indexes were also defined, and results revealed that particles are ignited faster under oxidative atmosphere and that, on average, the combustion index is 1.7 times higher, which reinforces the more vigorous way that the samples are burned and how char is burned out faster in the experiments with air. Regarding the kinetics analysis, higher activation energies, and consequently, lower reactivity was obtained under the oxidative atmosphere for the second stage (~125 kJ/mol) and under the inert atmosphere for the third thermal conversion stage (~190 kJ/mol). Full article

Within a broader national project aimed at the hybridization of a standard city car (the 998 cc Mitsubishi-derived gasoline engine of the Smart W451), our team tackled the problem of improving the supercharger performance and response. The design concept is that of eliminating the mechanical connection between the compressor and the turbine. It turned out that it is also possible to modify both components to extract extra power from the engine and to use it to recharge the battery pack. First, the initial configuration was analyzed on the basis of the design data provided by the manufacturer. Then, a preliminary performance assessment of the turbocharged engine allowed us to identify three “typical” operating points that could be used to properly redesign the turbomachinery. It was decided to maintain the radial configuration for both turbine and compressor, but to redesign the latter by adding an inducer. For the turbine, only minor modifications to the NGV and rotor blades shape were deemed necessary. Fully 3-D CFD simulations of the rotating machines were performed to assess their performance at three operating points: the kick-in point of the original turbo (2000 rpm), the maximum power regime (5500 rpm) and an intermediate point (3500 rpm) close to the minimum specific fuel consumption (SFC) for the original engine. The results presented in this paper demonstrate that the efficiency of the compressor is noticeably improved for steady operation at all three operating points, and that its choking characteristics have been improved, while its surge line has not been appreciably affected. The net energy recovery was also calculated, and demonstrated interesting returns in terms of storable energy in the battery pack. Full article

The motivation for this article was to describe the creation of a battery electric drive of a smaller excavator of a well-known manufacturer. The aim of the excavator electrification research was to replace its internal combustion engine with an electric motor. The innovated excavator does not burden its surroundings with gas exhalations and excessive sound emissions, so that it can work in confined spaces or protected areas. Simulation models of electric and hydraulic parts of the drive were created to select the most suitable solutions verified or predicted by simulations in a Matlab/Simulink environment. Tests have shown that the excavator is capable of operating for at least 7 h without recharging the battery. The other main achieved results of the project are a functional model of zero emissions of mini-excavator exhalation gases with significantly reduced noise, a proven control algorithm in the form of software, and its utility model according to the patent application 2018-35127 adopted by the Industrial Property Office of the Czech Republic. Innovation of the solution of the excavator was awarded the Gold Medal at the Brno International Engineering Fair in 2018. Full article

Burundi faces low access to electricity and low quality of service. It depends on the interconnected networks constructed in the decade of 1980. Despite the different reforms relating to the liberalization and reorganization of the electricity sector, the REGIDESO remains the public company in charge of the production and distribution of electricity. It has also the responsibility to pump, treat, and supply drinking water in the main and secondary urban centers. This paper makes a review of the policies, reform, and organization of the electricity sector in Burundi. We estimate the performance of the electricity sector using descriptive analysis, on the basis of secondary data collected in East Africa and from the World Development Indicators (WDI), and qualitative data obtained through semi-structured interviews and text analysis. Our results show that despite the different reforms undertaken in 2000 and 2015, the electricity sector remains mainly a natural monopoly of the state. As a result, access to electricity and consumption per capita remain the lowest of East Africa and Sub-Saharan Africa as a whole. The electricity sector is also characterized by the poor quality of service due to technical and non-technical losses. Among the non-technical losses, the unpaid bills especially for the public sector are very high. The study recommendation is to implement the reform undertaken in 2000 by splitting the public services of water and electricity, and the one of 2015 by unbundling the electricity sector. Policy implying private participation in the electricity sector and prioritizing regional projects for interconnection to facilitate cross-border trade of electricity are highly recommended. Full article

The solar receiver is a critical component of concentrated solar power technology; it works as a heat exchanger, transforming the concentrated solar radiation into high-temperature heat. Volumetric receiver technologies, using air as a heat transfer fluid, are designed to reach higher temperatures than the current receiver technology, which is limited by material resistance and fluid instability. The higher temperature, up to 1200 K, could be used in high-temperature industrial processes or a high-temperature thermodynamic cycle. A correct radiation propagation is essential to develop their performances, reducing reflection and emission losses and promote the heat transfer to the fluid. In this study, the optical behaviour of a hierarchical volumetric receiver (HVR) developed in Bruno Kessler Foundation (FBK) has been studied using Monte Carlo ray tracing (MCRT) simulations. The simulations have been validated in an experimental setup that evaluates the light transmissivity of the HVR porous structure. Two different HVR structures are evaluated with MCRT simulations that use a real solar dish geometry to configure a complete concentrated solar power (CSP) plant. Results show that frontal and rear losses are, respectively, 12% and 3% of the incoming concentrated radiation. Inside the HVR, 15% of the incoming power is propagated trough the lateral void spaces. Therefore, the power spreading avoids the overconcentration of the centre of the focalized area. The HVR optical behaviour has been investigated, showing an optical efficiency of 85%. Full article

This paper explores the advantages of using relative free energy instead of exergy to build a mathematical theory of thermodynamic costs to diagnose malfunctions in thermal systems. This theory is based on the definition of a linearized characteristic equation that represents the physical behavior of each component. The physical structure of the system described by its energy interrelationships is called “primal”, and its derivatives are the costs and consumptions. The obtained cost structure is the mathematical “dual” of its primal. The theory explains why the F and P cost assessment rules and any other suggestion may (or may not be) rational under a given disaggregation scheme. A result of the theory is a new thermodynamic function called the relative free energy and a new parameter called deterioration temperature, which due to a component’s deterioration cause and is characterized by an h–s thermodynamic trajectory describing the effects on the exiting stream. The relative free energy function allows for an exact relationship between the amount of used resources and the increase in entropy generation caused by the deterioration path of the component. This function allows the obtaining of, for the first time, an appropriate characteristic equation for a turbine and a new definition of efficiency that does not depend on the environmental temperature, but on the deterioration temperature. In addition, cost with relative free energy instead of exergy may open a new path for more precise and straightforward assessments of component deterioration. Full article

Simulations of two incineration processes, with and without flue gas recirculation, have been carried out performing an exergy analysis to investigate the most critical equipment unit in terms of second-law efficiency. Flue gas from the economizer outlet is employed to partially replace secondary combustion air to reduce, at the same time, incinerator temperature and oxygen concentration. Conversely, in the proposed configuration, the recirculated flue gas flow rate is used to control incinerator temperature, while the air flow rate is used to control the oxygen content of the fumes, leaving the incinerator as close to 6% as possible—i.e., the minimum allowed for existing plants to ensure completion of the combustion reactions and according to environmental regulations—and determines the corresponding minimum flue gas flow rate. The flue gas recirculation guarantees a larger level of energy recovery (up to +3%) and, at the same time, lower investment costs for the lower flow rate of fumes actually emitted if compared to the plant configuration without flue gas recirculation. Various operating parameters were varied (incinerator’s effluent gas temperature, air flowrate and flue gas recirculation flowrate) to investigate their influence on process exergy efficiency. Exergy analysis allowed the individuation of the equipment units characterized by larger exergy destruction and demonstrated that the flue gas recirculation led to an overall process exergy efficiency increase of about 3%. Full article

The objective of this work is to analyze, through environmental vulnerability (EV), disturbances in the environment caused by anthropic activities for the production of energy resources, focusing on the power generation sector. Methodologically, hydrocarbons (oil and gas) and solar are considered through a qualitative and quantitative analysis of environmental impacts, including the research in Environmental Impact Studies and procedures like EIA/RIMA (institutional Environmental Impact Reports in Brazil). This study focuses on operation and demobilization of offshore drilling activity, and installation and operation of the Santos Basin pre-salt oil and gas production and disposal activity Stages 1, 2, and 3. The criteria addressed in the EIA/RIMAs are used, focusing on those that correlate with EV and the production of electricity. Impacts for long-term, permanent, partially reversible, or irreversible disturbances are filtered, totaling 53 impacts (31 effective/21 potential). We concluded that the criteria and methodologies of EIAs vary between stages. At times, the variation is so drastic that the same impact can have a completely different rating from one stage to another, despite referring to the same area. This condition makes it impossible to define a single vulnerability index for the pre-salt venture. For a final analysis, we propose a cleaner energy production through distributed photovoltaic systems as a more adequate alternative for São Paulo’s energy supply in terms of its impact on EV. Full article

In the race for energy production, supplier companies are concerned by the thermal rating of offshore cables installed in a J-tube, not covered by IEC 60287 standards, and are now looking for solutions to optimize this type of system. This paper presents a numerical model capable of calculating temperature fields of a power transmission cable installed in a J-tube, based on the lumped element method. This model is validated against the existing literature. A sensitivity analysis performed using Sobol indices is then presented in order to understand the impact of the different parameters involved in the heating of the cable. This analysis provides an understanding of the thermal phenomena in the J-tube and paves the way for potential technical and economic solutions to increase the ampacity of offshore cables installed in a J-tube. Full article

This study addresses passive adaptation strategies to reduce the effects of global warming on housing, focusing on low-income houses, for which passive adaptation strategies should be prioritized, aiming for environmental sustainability. The passive strategy chosen is thermal mass for cooling, through the adoption of earth-sheltered walls in contact with the ground. Thus, the goal of this study is to evaluate the thermal load and thermal impact of implementing a thermal mass strategy for cooling, using bermed earth-sheltered walls in bedrooms, for a building located in a tropical climate region. For that, a base scenario (1961–1990) is considered alongside two future scenarios: 2020 (2011 to 2040) and 2050 (2041 to 2070), both considering the effects of climate change, according to the Fourth Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). The methodologies adopted are (i) the computational simulation of the annual thermal load demand and (ii) the quantification of the Cooling Degree-Hours (CDH) with the subsequent comparative analysis. The results show that in both the 2020 and 2050 scenarios there will be an increase in the thermal loads for cooling and the CDH, regardless of using a bermed earth-sheltered wall. Nonetheless, it is shown that this passive strategy works as a global warming adaptation measure, promoting building sustainability in tropical climate regions. Full article

A State-of-Charge (SOC) real-time estimation plays an essential role in effective energy management. This paper proposes the use of an Artificial Neural Network (ANN) to design a state-of-charge estimator for a Graphite/LiCoO2 lithium-ion battery pack. The software MATLAB was used to develop and test several network configurations to find the ideal weights for the ANN. The results demonstrate that the Mean Squared Error (MSE) achieved renders the ANN as an effective technique. Thus, it predicted the battery bank’s SOC values with accuracy using only voltage, current, and charge/discharge time as inputs. Full article

To meet the global demand of energy requires an alternative source, preferably with a lower concern of climate change. Biochar production from agricultural biomass waste by pyrolysis creates a unique solution for producing a useful source of green energy. Biochar is a carbon-rich product with a high heating value which is comparable with our primary energy sources (fossil fuels). Biochar can be utilized for various purposes such as energy production and soil enhancement. Biochar can be more suitable for steelmaking, in view of their chemical and thermo-chemical characteristics including low ash, higher heating values (HHV), and high surface area. Biochar can also be utilised selectively for soil amelioration, C-sequestration, and waste water treatment, in view of the suitability of their characteristics (such as higher values of pH, mineral content, and surface area) for meeting the requirements for a particular purpose. This study associates the characteristics of biochar produced by slow pyrolysis at 800 °C for two biomass residues: corn cob and coconut shell. These results can be used to establish ideal utilization means of biomass for energy and/or biochar production. Full article

A crucial way to reach a future sustainable society concerns the path towards nearly zero-energy buildings because of large amounts of energy at stake. The present work proposes an approach for the optimal integration of small-scale technologies (renewable and traditional) to enhance the pathway of existing and inefficient buildings towards low-carbon systems in a cost–benefit effective manner. Operation optimization, as well as an innovative combined design, is investigated with the goal of selecting the capacity of the technologies to be installed depending on the expected operations. The renewable technologies are integrated with proper storage units, such as batteries and latent thermal storage, which allows for reducing the space required for the installation. Two different non-linear programming approaches are used with the aim of finding an optimal solution. The optimization allows for reducing operation costs of 22% for renewable energy sources (RES)-fed dwellings. The combined operation and design optimization lead to a reduction in installation and operating costs by 7%. In the analyzed case, the adoption of the advanced optimization approach shows that latent heat storage is more suitable to be installed than electric storage (−2.5% cost). Full article

In this century, with increasing society’s population and Gross Domestic Product (GDP) trend, energy demand is increased in the countries of the whole world. Nowadays, the use of different Renewable Energy Sources (RESs) in the network has become commonplace and, of course, has been challenged. In this way, forecasting energy demand plays a key role in the development of different parts of a country. In this study, firstly a prediction of consumption and fluctuations in the sources of energy is made, and secondly, regarding different parts of the industry, agriculture, and households, two different scenarios have been analyzed to provide this demand in the future. An Artificial Neural Network (ANN) method has been used to predict energy consumption level, and also the two factors of the increase in population and GDP have been considered. Prediction of population increase rate, with respect to its statistical complexities, is derived from a literature review of other references; the GDP prediction is derived with a conventional method of the Grey method. Then, with the prediction of the aforementioned factors, energy consumption is predicted by a metaheuristic algorithm. Afterwards, scenarios related to the energy consumption are predicted and priorities are given, such as environmental impacts, in order to provide the predicted consumption level. Scenarios will considerably show that the supply and demand should be managed by fossil fuel energy production replaced with RESs in the supply side, and providing products with higher energy efficiency in the demand side. Full article

The paper develops generalizing entropic approaches of irreversible closed cycles. The mathematical models of the irreversible engines (basic, with internal regeneration of the heat, cogeneration units) and of the refrigeration cycles were applied to four possible operating irreversible trigeneration cycles. The models involve the reference entropy, the number of internal irreversibility, the thermal conductance inventory, the proper temperatures of external heat reservoirs unifying the first law of thermodynamics and the linear heat transfer law, the mean log temperature differences, and four possible operational constraints, i.e., constant heat input, constant power, constant energy efficiency and constant reference entropy. The reference entropy is always the entropy variation rate of the working fluid during the reversible heat input process. The amount of internal irreversibility allows the evaluation of the heat output via the ratio of overall internal irreversible entropy generation and the reference entropy. The operational constraints allow the replacement of the reference entropy function of the finite physical dimension parameters, i.e., mean log temperature differences, thermal conductance inventory, and the proper external heat reservoir temperatures. The paper presents initially the number of internal irreversibility and the energy efficiency equations for engine and refrigeration cycles. At the limit, i.e., endoreversibility, we can re-obtain the endoreversible energy efficiency equation. The second part develops the influences between the imposed operational constraint and the finite physical dimensions parameters for the basic irreversible cycle. The third part is applying the mathematical models to four possible standalone trigeneration cycles. It was assumed that there are the required consumers of the all useful heat delivered by the trigeneration system. The design of trigeneration system must know the ratio of refrigeration rate to power, e.g., engine shaft power or useful power delivered directly to power consumers. The final discussions and conclusions emphasize the novelties and the complexity of interconnected irreversible trigeneration systems design/optimization. Full article