Journal of Sustainable Energy

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)