In the recent past, several examples of the application of Exergy Analysis (ExA) to 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 seem to diverge. There are several contingent reasons for this, but the underlying problem is that a purely thermodynamic analysis does not represent 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 feed)is transformed into final energy, such as diesel fuel, electricity or other commodities. The issue here is that the so-called Externalities (Capital, Labour 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, labour and environmental “exergy costs” in the global budget. Scope of the study presented in this paper is twofold: first, to discuss in a formally structured fashion a general procedure for performing the EEA of a “System Country”; second, to inspect the results to identify possible correlations between the “exergy efficiency” of a Country -i.e., its ability to exploit the incoming exergy flux with the minimum amount of losses (material, energy waste and irreversible exergy destruction)- and some of the most popular indicators used to assess the “degree of sustainability” of a system, bearing in mind a time frame of ten years (2007-2017).As an efficiency indicator we use the Exergy Footprint, a measure of the global primary exergy consumption of a system, which turns out to be also a very useful indicator of the “degree of unsustainability” of a Country. Our results confirm that the Gross National Product, already criticized for not representing the reality of the economy of a Country, is very weakly -if ever- correlated with the EF in the decade of observation. Other indicators display different degrees of correlation with the EF, and the reasons are critically analyzed.

Within a broader national project aimed at the hybridization of a standard city car (the 899 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 and to possibly 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 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 blades shape were deemed necessary.
A 3-D CFD simulation of the rotating machines was 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 sfc for the original engine.
The results demonstrate that the efficiency of the compressor is noticeably improved for steady operation at all three points, that its choking characteristics have been improved and that the surge line has not been appreciably affected. For the turbine, the efficiency displayed only little improvement with respect to the original configuration, but the introduction of variable nozzle guide vanes led to a much more stable performance.. The net energy recovery was also calculated, and demonstrated interesting returns in terms of storable energy in the battery pack.

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.

With the expansion of offshore wind farms and oil platforms, industrials are concerned about J-tubes and the thermal limiting point imposed to submarine cables installed inside. Nowadays, current rating of such cables is not covered by the scope of IEC 60287 [1, 2] and a de-rating coefficient of 0.88 is generally used to avoid overheating of cables, defined by ERA in 1988 [3]. Furthermore, load cycles and weather conditions create unsteady thermal behaviour inside the offshore cable.
Currently only a few works deal with this situation by using time consuming finite elements calculation, in steady state and transient [4, 5, 6]. Other works uses simple models based on 1D energy balance, reliable only in steady state, which return conductors temperature exclusively [7, 8, 9].
In this paper, we introduce a model based on Lumped Element Method, which is convenient to simulate an energy cable in different environment, especially here in a J-tube. This method relies on electrical-thermal analogy by representing heat flux through thermal conductances, allowing us to have access to 2D temperature field in the cable and J-tube using thermal nodes. In a first step, we validate this model by comparison with previous work in steady state, for a 132Kv SL-type XLPE insulated cable [9]. Then, we extend this work to transient by adding thermal capacitances to each node, and we study the cable thermal behaviour depending on weather conditions (sun, wind, ambient temperature). In addition, based on IEC 60853 standards [10], we study the effect of load cycles on the offshore cable, which are very present in offshore windfarm due to the fluctuation in the energy production (wind variability). A comparison is made with thermal measurements through a thermocouple in the cable installed in a J-tube on an offshore platform.

References
[1] IEC. IEC 60287 1-1 : Calcul du courant admissible - Equations de l’intensité du courant admissible (facteur de charge 100 %) et calcul des pertes – Généralités. 2014.
[2] IEC. IEC 60287-2-1 : Calcul du courant admissible - Calcul de la résistance thermique. 2015.
[3] M Coates. Rating cables in J-tube. Technical report, 1988.
[4] J. Pilgrim, S. Catmull, R. Chippendale, R. Tyreman, and P. Lewin. Offshore Wind Farm Export Cable Current Rating Optimisation. EWEA Offshore Wind, Conference, 2013.
[5] Richard Chippendale, Priank Cangy, and James Pilgrim. Thermal Rating of J tubes using Finite Element Analysis Techniques. Jicable 2015, (1):4–9, 2015.
[6] Lei You, Jian Wang, Gang Liu, Hui Ma, and Ming Zheng. Thermal Rating of Offshore Wind Farm Cables Installed in Ventilated J-Tubes. Energies, 11(3):545, 2018.
[7] Hartlein and Black. Ampacity of electric power cables in vertical protective risers. IEEE Transactions on Power Apparatus and Systems, PAS-102(6):1678–1686, 1983.
[8] George J. Anders. Rating of cables on riser poles. Jicable, pages 602–607, 1995.
[9] R. D. Chippendale, J. A. Pilgrim, K. F. Goddard, and P. Cangy. Analytical thermal rating method for cables installed in J-Tubes. IEEE Transactions on Power Delivery, 32(4):1721–1729, 2017.
[10] IEC. IEC 60853-2 : Calculation of the cyclic and emergency current rating of cables – Part 2: Cyclic rating of cables greater than 18/30 (36) kV and emergency ratings for cables of all voltages. 2008.

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 CLIPS environment and is denominated PROMISE as the acronym for PROgnostic and Intelligent Monitoring Expert System, 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 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, 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 in 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 PROMISE about its rules, procedures, classes and objects, and about its inference path. The paper also presents the results of some simulation tests.

Burundi is facing to low access to electricity and low quality of supply. The electricity sector relies on hydroelectric plants and high transmission lines constructed in the decade of 1980. The connection extension increased the number of customers without increasing the installed capacity. The electricity sector is managed by a public company, which is at the same time in charge of the production, the transport and the distribution of electricity, the pumping, the treatment and the supply of drinking water in the main centers urban and secondary centers. Since the beginning of the decade of 2000, the government of Burundi edicted policies and textbooks related to the electricity sector, aiming to liberalize and regulate the sector, in order to increase the access to electricity and the quality of supply. This paper makes a review of policies drivers, reform and organization of electricity sector in Burundi through the different national policies, strategies, laws and decrees. We estimate the performance of the electricity sector using the descriptive statistics. We discuss the results using semi-structured interviews carried with officials from the ministry responsible for energy, the Régie de Production d’Eau et d’Electricité (REGIDESO) and electricity users. Results show that few steps of reform were realized in electricity sector. Also, access to electricity remains low, while the quality of service is poor. We recommend attracting more investment in electricity generation and stabilize the national economy to increase electricity consumption.

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 capability 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.