Journal of Sustainable Energy

5

Authors: KLADISIOS P., SAGIA A.

Supercritical water gasification is a promising and environmentally friendly biomass conversion method. Compared to conventional gasification, it is capable of handling biomass with high moisture and displays higher conversion efficiency and decreased tar formation. Through supercritical gasification, organic feedstock in the presence of supercritical water is converted into a mixture of H2, CO2, CO, CH4 and traces of other gases over shorts periods of time. The composition and yield of the final gas mixture depends highly on reaction temperature, feed concentration and nature of catalyst in use. Reaction pressure and residence time play a less important role. Despite being appealing for the production of hydrogen from an inexpensive source, hydrothermal gasification suffers from decisive technical challenges, with corrosion and efficiency being the most critical.

6

Authors: EL FARRI. H, BOUACHRI. M, FAHOUME. M

In this paper, the performance of CIS Based solar cells was investigated, using a simulation program named SCAPS-1D Software (Solar Cells Capacitance Simulator). CIS cell structure is based on Cu(In, Ga), (Se,S)2; which is a semiconductor compound as an absorber layer; un-doped Zinc Oxyd (i) ZnO as a window layer, and Sulfide Cadmium as a Buffer layer, with an efficiency of ƞ=17%. We studied the influence of different layers’ thickness and their defect densities, working temperature and absorber carrier density on the CIS based solar cells. The photovoltaic parameters have been calculated, and we have obtained the optimal values of every constraint cited above. As a result, we obtained a new high efficiency value of 19.71%, under air mass (AM) 1.5 and 100 mW/cm2 illumination and the area of this device was 0.15 cm2 [8].

8

Authors: TIRUNEH A.T., DEBESSAI T., NKAMBULE S., BWEMBYA G.

The performance of compound parabolic solar concentrators (CPC) is extended through the provision of additional external reflectors that increased the angle of acceptance and hence achieve concentration for longer part of the day. The modified setup increased the angle of acceptance by over 70% while achieving comparatively close concentration ratio ranging between 90-100% of the maximum attainable. For construction of geometry of the reflector profile, an approach involving coordinate transformation has been used. Satisfactory performance of the solar concentrator has been observed for applications involving grey water treatment, production of struvite and drying of fecal matter from urine diversion dry toilets and compost.

10

Authors: FELEA. I., MOLDOVAN V., BUNDA. S., LIBOR L., ILE I.

Knowing the level of energy efficiency is essential for substantiating investment decisions, operation and maintenance of energy consuming equipment and machines. Urban public transport is an important consumer of energy and, at the same time, an important source of pollution of the urban environment with greenhouse gases and micro particles. The present paper is aimed to identify the level of the energy performance of a public transport car fleet, having buses equipped with Diesel engines. The analysis methodology and the mathematical model used are applicable to other similar structures. The obtained results are valid for the analyzed car fleet, highlighting the values of the energy performance indicators, on the whole, by bus categories and for each bus from the park component. Based on the results obtained within the energy audit, comparisons are made for the level of energy performance with similar consumers, and feasible measures to improve energy efficiency are identified.

3

Authors: OHAJIANYA A. C., MBAMALA E. C., AMAKOM C. M., AKUJOR C. E.

Zinc-Chlorine battery received huge attention from researchers in the 1970s and 1980s due to its simplicity and low cost of basic materials. But the additional materials in the existing designs which are meant to enable the battery to operate with a reasonable level of efficiency; have considerably increased the complexity and cost of the battery. This led to a loss of interest by researchers as literature revealed that there has not been researched work in this battery for many years now. We hereby present a new and simple design for Zinc-Chlorine battery that does not use ion exchange membrane, pump, cooler, and heater. The designed electric cell was constructed and tested. It produced an open-circuit voltage of 2.14 V after charging for 2 hours with a dc source voltage of 5.0 V. A maximum current of about 12 mA/cm2 was realized from the electric cell

5

Authors: NANA TWUM DUAH, PRINCE KOFI ASAMOAH.

The use of electricity and heat are essential in our daily life activities. They areused domestically for heating, lighting, washing, cooling, and cooking. Commercially, it is used in transportation, heating, cooling, manufacturing and processing. In view of this, there is the need to use energy (electricity and heat) efficiently to reduce the waste from energy such as heat and CO2 released into the atmosphere. The efficient use of energy makes the environment safe and maintains a high quality of lives of people. The majority of electricity generated in the world today is from thermal, which has a low efficiency ranging between 30-37% and combines cycle gas turbine (CCGT) having approximately 47%. A high percentage of the primary fuel used to generate power is converted to waste as heat into the environment. Therefore, the need arises to recover the heat and used for another purpose to enhance efficiency. To attain higher efficiency and effective use of primary fuel, Combined Heat and Power (CHP) is employed in recovering of waste heat to be reused, therefore, increasing productivity. This paper highlights the working principles, application, factors influencing the selection of CHP and economic importance of installing CHP. It further uses a Salford hospital as a case study to explain the economic benefits of installing CHP.

7

Authors: MD. ABDULLAH AL ZAMAN, H. M. A. R. MARUF, RIFAT AMIN, M. R. ISLAM, MD. MEHEDY HASAN TANVIR

The growingdisposition of livestock resources as well as the poultry sector with the corroborating weather conditions in Bangladesh encourages an auspicious future of bioenergy. In this paper, existing energy situation of Bangladesh and noteworthy activities associated with renewable energy has been mentioned. After presenting the potential of livestock resources of Bangladesh, the Union based biogas plant model has been explained. The model has been employed to study the potential of generating biogas as well as electricity in Chattogram division of Bangladesh. Under this model, each union can contribute 552 m3 of gas or 0.75 MW of electricity daily and in total 3.2×105 m3 of gas or 435 MW of electricity can be generated in Chattogram division. Union based biogas plants will be beneficial for the rural development but difficult in implementation. Therefore, several issues that required reconciling before installations have been indicated.

7

Authors: FELEA. I., RANCOV N., ALBUT-DANA D.

Knowing energy performance level of an energy consumer is essential for substantiating the decisions for development, operation and maintenance. Energy performance level is highlighted through consecrated indicators which are obtained by means of energy balance. The present paper is a synthesis of electric energy balance that was done within a mixed fodder factory (MFF). In the first part a short presentation of the consumer (MFF) is presented and also analysis methodology. After that we refer to specificities regarding the energy balance model (EB) applied and to characterization elements of typical processes for MFF. An important part of the paper is dedicated to present the obtained results and the energy performance level. In the last part of the paper we present the conclusion of energy audit (EA) and the recommendations to improve the energy performance level.

3

Authors: POPESCU V.

At the current stage, in electrical distribution systems from Republic of Moldova, take place a significant number of unplanned disconnections, which considerably reduce quality and continuity of the distribution process and power supply. Knowing the evolution of these disconnection for long periods, offers the possibility to elaborate a credible prognosis, which helps to establish solutions to ensure the reliability of these systems. In this work, is presented a study regarding evolution of unplanned disconnections from electrical republican distribution systems and the results of this study allow developing the insurance mechanism of the reliability indicators and quality of power supply, forRepublic of Moldova.

5

Authors: MATEESCU C., DIMA A.D.

Romania benefits from adequate geo- climatic conditions that allow for the development of a complex agriculture; the share of Romanian agriculture in the national GDP of 4.8% is the highest in Europe, compared to the average of 1.3% in the EU-28 countries. Agriculture and agro-industries generate huge amounts of solid organic waste, sludge and wastewaters that can be used in the energy sector for biogas production, thus providing energy bioresources without creating political and economic controversies regarding the use of agricultural land for the production of biofuels in the detriment of food. This paper proposes innovative ideas of non-polluting technologies for the recovery of agro-zootechnical waste in decentralized biogas systems. The referred technologies are the result of some experimental research carried out by INCDIE ICPE-CA specialists within national and bilateral research projects; these achievements are intended to be applied for waste water treatment and organic sludge neutralization or transferred to beneficiaries from rural areas. Innovative elements that ensure an advanced recovery of the organic component and the production of biogas with high energy value are presented. Also, the paper makes a brief analysis of the economic, social and environmental benefits that such systems can bring to rural communities and companies generating organic waste. Finally, the results regarding technology transfer to the producer, and the main barriers responsible for the very slow growth of biogas technologies in regions with high agricultural potential are pointed out.

6

Authors: ERCHAN F., RIMSCHI, V., NANTOI, O.

The article is devoted to the analytical solution of the telegraph equations for a semi-infinite line with losses with an arbitrary form of input voltage. An exact analytical solution for a semi- infinite line with losses with an arbitrary input voltage form is proposed as model. The results of model calculations are given, which clearly illustrate the lack of alternatives to PaPuRi, an algorithm presented in the form of a computer program in the Matlab application environment.

10

Authors: LAWAL O., IKPO R.C.

Oil spills are hazardous due to their impact on the people, the environment and economic wellbeing of the society. The study examined the space-time trend and pattern of oil spills in the Niger Delta (2006-2016). Data were sourced from the National Oil Spill Detection and Response Agency (NOSDRA). Mann-Kendal trend and Getis-Ord Gi* statistics were used to identify the spatial and temporal trend. A total of 6,487 incidents were identified, about 31% were recorded on Tuesday and Wednesday while the highest number (10%) of incidents occurred in May. The average nearest distance among events indicates spatial clustering, as the observed mean distance (0.29km) is significantly (Z-score -121.69, P < 0.01) smaller than expected mean distance (1.39km). Of the 8,900 total locations (grid size of 2.8km, 132 months), 941 (10.57%) contain at least one incident for at least one-time step interval. These 941 locations comprise 124,212 space-time bins of which 4,262 (3.43%) have incident counts greater than zero. These resulted in trend statistics of 10.61 (P<0.05), indicating that there is a statistically significant increase in point counts over time (monthly). Statistically significant event grids (62) were found to be hot spots. These hot spot clusters are spread across Bayelsa (4), Delta (2) and Rivers (3) States. The results gave a clear indication of the areas where over time and space oil spills are prominent. Thereby, identifying statistically significant space-time pattern of incidents which could inform mitigation measures and facilitate the implementation of adequate risk management and contingency planning.

10

Authors: OSEI-APPIAH N.A., DIOHA M.O.

To reduce environmental degradation and improve energy security in Ghana, waste-to-energy (WtE) technologies will play a key role. This paper assesses the feasibility of municipal solid WtE technologies in Ghana using Accra as a case study. Technical feasibility, economic feasibility, and barrier analysis have been carried out to assess the feasibility of municipal solid WtE conversion technologies. Data from the Environmental Protection Agency of Ghana is used for the techno-economic analysis and a face-to- face interview is used to assess the barriers to the deployment of WtE technologies in the country. A power generation potential (PGP) of 530 kW/tMSW and an energy recovery potential (ERP) of 41.68 kWh/tMSW is recoverable from the waste in Accra when biochemical energy conversion is applied and a PGP of 1320 kW/tMSW and an ERP of 106 kWh/tMSW is recoverable when thermochemical energy conversion is applied. The economic analysis showed that the initial investment cost of WtE technologies is high, however, implementation of this technology is likely to have a good payback period of 8 years for the thermochemical processes and 4 years for the biochemical process. Additionally, the net present value and the sensitivity analysis conducted shows that WtE technologies are economically feasible in Ghana. The barrier analysis suggests that the main hindrance to the deployment of WtE technologies in Ghana is the high upfront cost.

4

Authors: ERHAN F.

The power electric distribution systems (PEDS) possess a great dynamics of development. Thanks to this phenomenon in the power electric distribution systems (PEDS) the probability of apparatus of asymmetrical regimes increase monotonously. As a result of this reliability of the functioning of the power electric equipment installed in the electric knots changes. The asymmetrical regimes in the power electric distribution systems (PEDS) accompanied by the short circuit current are a function of a row determinate is a vague factor of probabilistic nature. Coming from it follows that the investigation of the influence of the asymmetrical regimes accompanied by the current of the short circuit on the reliability of the Power Electric Distribution Systems (PEDS) is one of the most important problems of the development the Power Electric Distribution Systems. The short circuit currents influence the structural and functional reliability of distribution networks and at the reliability of electrical equipment installation

5

Authors: BUNDA Ș

An important component of the variable renewable generation (VRG) integration in Romanian power grid represents the wind and solar curtailment energy due to the impact it can have on economics. This paper performs a quantitative assessment of both VRG penetration and curtailment ratio in Romanian grid using the new tool proposed in specialty literature named “C-P map”. It was only calculated the penetration ratio, for the curtailment ratio only being made interesting scenarios due to the lack of official data. This has allowed obtaining images of principle regarding near future tendency for the national power network, providing help in planning and decision making in order to optimize the VRG curtailment level and secure grid operating.

7

Authors: ÖZDEMIR M. H., TIMOR M.

Energy is an indispensable and ever- growing need in our daily lives. Due to the finite nature of our planet’s resources, the importance of renewable energy sources is increasing in tandem. For example, wind power plants (WPPs) are growingrapidly in use. In this studywehave calculated the relative efficiencies of 22 Turkish WPPs. As these WPPs are of different sizes, an initial cluster analysis was performed using data collected in the 2014-2016 period. For each cluster, data envelopment analysis (DEA) was conducted to calculate the relative efficiencies of the WPPs. DEA-derived weightings were then used to rank WPPs by TOPSIS (Technique for Order Preference by Similarity to Ideal Solution). Finally, DEA and TOPSIS rankings were compared.

8

Authors: ROSCA V.M., MIRCEA P.M., BUTOARCA E., MIRCEA I.,MARIN I., BRATU C., CIONTU M.

The paper proposes to present the way through which the neutral treatment method influences the performance indicators of an electrical energy distribution service. In the paper are presented both the calculation methods for all indicators as well as their evolution using as reference two different electric stations pertaining to Distribuţie Energie Oltenia (DEO), stations which during 2017 have had their neutral treatment method changed. The indicators regarding the quality of the transport and distribution service, as well as the quality of the electric energy distributed through the electrical transport network (RET) and the electrical distribution network (RED) represent an essential factor in the substantiation of the technical and economic elements related to the execution/ modernization of the electric networks and influence greatly the economic efficiency of the users’ activity. In the category of users of the electric networks are included the consumers of electric energy, the distribution operator, the producers and other network operators connected to the networks of the national electrical system (SEN)

3

Authors: NICUSOR I.A., GROSU F.

Discharging reactive power distribution networks contributes to reducing active energy losses and increasing electricity transit capacity. Inappropriate management of reactive power sources in distribution networks, including those from network users, leads to uncontrolled reactive power circulation with effects on voltage levels and losses. Considering that to date the charging of the electricity distribution service is made through simple (monome) rates expressed in RON / Mwh, without considering billing power absorbed and maximum consumption time, the only element by which the user is warned over network behavior is the reactive energy billing mode. Regulatory changes to reactive energy can also lead to changes in addressing technical aspects of installations at the managed delimitation point. Both the change of retailer's revenue from reactive energy and the penalty mode impacts has an impact on the quality of the distribution service. Switching from full billing to capacitive reactive energy (energy sent to the grid) upon admission of an unanswered reactive injection equivalent to 48.44% of active energy is a technical and financial relaxation for users with consequences for distributors. The lack of analyzes or studies related to regulatory changes allow us to present some considerations regarding reactive energy in distribution networks

6

Authors: OCTAVIAN C., SILVIU D.

The increase in domestic electricity consumption have forced the power industry to examine its health. The context is: The climate change exigencies and his threat to the survival of humanity is real; the fossil resources are mostly, politically controlled; In return, the rise of renewable technologies and its the democratic geographical distribution feature is a huge advantage: sun shines everywhere for everyone! Conclusion: mankind is at the turning point of its energy future. And the future power systems sould be a tissue of intelligent energy cells. In Romania (3GW wind and 1,3GW solar - large plant) it is a fear about more renewables, special wind. One root of this fear could be the gap between Romanian authorities: one authorithy establish rules without considered facts and the other authority must oparate in a hostile „enviromnent”. To get an independently opinion about these facts we’ll look on SEN. More, we had to compare the German toward Romanian legislation in the matter of renewables. Further we compare the actual SEN with a future one that is the actual national energy system with an added 1,7GW photovoltaic. Here, this new added photovoltaic are like the other 1,3GW active now în SEN. Another step further, we will model this hipothetical SEN with new 1,7Gw, but not large but small residential photovoltaic cell with storages. From here two conclusions comes out!

8

Authors: MAHJOUBI A.

In this paper, we have studied the solar radiation data available at two meteorological stations located in the south of Tunisia. Measurements of global solar radiation on horizontal surface are compared to predictions made by different methods. The first method is based on Angström-Prescott formula which correlates relative global solar radiation H/H0 to corresponding relative duration of bright sunshine SS/SS0. The second method, a model due to Mechlouch et al., uses cloud cover N, the hours of the day t and the quantum of the year q. The third method, an empirical relation due to Sivkov, uses the monthly sunshine duration nm and the noon altitude of the sun h. The models are compared and tested on the basis of statistical error tests (MBE, RMSE, MPE and R2 ) and the results are presented.

10

Authors: KLADISIOS P., SAGIA A.

Hydrothermal carbonization (HTC) is characterized by simplicity and relatively low reaction temperature and pressure (subcritical water conditions). It is also capable of processing organic material with high moisture content. The combination of the above justifies the growing interest around this specific pre-treatment method of biomass. However, the properties of hydrochar, the main product of HTC, are significantly affected by the process conditions (temperature, residence time, water-to- biomass ratio, feedstock composition etc.). In addition, the exact reaction mechanism is currently partially understood. That is the reason why only the hydrothermal carbonization of specific types of biomass under distinct conditions has been investigated. The purpose of this paper is to highlight the advantages of hydrothermal carbonization, describe the general reaction mechanism and examine the dependence of the products to the process parameters. Representative cases of reaction kinetics modeling based on experimental data were selected for demonstration. The paper concludes with an overall evaluation along with suggestions to improve the efficiency of the process.