Journal of Sustainable Energy

3

Authors: CÂRLAN M., CSUZI. I., COSTEA M

The paper presents three operative models whose purpose is to improve the practice of preventive maintenance to a wide range of technical installations. Although the calculation criteria are different, the goal is the same: to determine the optimum time between two consecutive preventive interventions. The optimum criteria of these models are: - the maximum share of technical entity operating probabilities, in the case of the Ackoff - Sasieni [1] method; -the optimum time interval for preventive verification depending on the preventive-corrective maintenance costs imposed by the deciding factor, for the AsturioBaldin [2] model; - the minimum number of renewals – preventive and/or corrective maintenance operations [3].

5

Authors: BUZATU G. C., STAN IVAN F. E., MIRCEA P.M., MIRCEA I

The paper is structured in three parts. In the first part of the paper, are presented some theoretical notions regarding the sound, noise, the sound insulations materials. Also in the first part of the paper are presented some characteristic regarding the insulation materials and there effects. In the second part it is described an calculation example for a homogeneous wall with double structure in order to determine the attenuation index curve "Ri(f)". The example calculation contains 10 steps that must be followed and the final results are presented in table 7 and figure 3. The last part of the paper is represented by conclusions, where the authors tried to explain the importance of the curve "Ri(f)" for reducing the noise in the buildings.

6

Authors: DINU R.C., POPESCU D.

Currently, many building managers record complaints from homeowners regarding the indoor climate. The main issue is that some rooms never have the desired temperature. After changing the load, room temperatures vary, particularly at small and medium loads. The design capacity can not be transmitted during the start of the heating system after setting and operation under a week-end or night. Such problems arise when the installation has an incorrect heat flow which prevents proper functioning of regulators. Considering that flow and pressure regulators ensure effective control when flows prevail in the plant project, this paper presents two solutions with differential pressure in heating with radiators. These solutions consist in the use of automatic differential pressure regulators or proportional relief valves.

4

Authors: CARAMITU A., VOINA A., RUS T., LINGVAY I.

Determining the working life of the anticorrosive protection layers is of great importance for electro-energetic installations. In order to assess the durability of the paint layers have been achieved films of 100 ÷ 120µm from six different commercial types of paint. After polymerization/drying, the dielectric characterization of the obtained films has been achieved by dielectric spectroscopy - both before and after their exposure to controlled doses of UV radiation. The experimental results have been revealed that the polymer matrix of the painting materials, over a critical dose of UV radiation (specific commercial sort), suffers a complex process of aging after which the anticorrosive insulation capacity decreases.

5

Authors: STAN IVAN F.E., MIRCEA I

The paper includes a simplified economical and financial analysis of the buildings rehabilitation solutions, for heating and lighting. The most important economic and financial indicators analyzed and determined are: economic return on investment and payback period of investment in dynamic form, net present value, and internal rate of return economic residual value of the investment on thermal insulation, building maintenance costs, energy costs. In order to reduce the electricity consumption: the methods consisted in replacing inefficient lighting with some efficient energy and for heat consumption: the proposed solution was building rehabilitation (exterior wall insulation, floor insulation board). The analysis consists in determining the economical and financial indicators before and after the building rehabilitation. The 3 rooms apartment is located in Craiova town, (wind zone IV), 2nd floor, orientation is S.

5

Authors: VOINA A., RADU E., CARAMITU A.R., LINGVAY M. , ALECU G.

By dielectric spectroscopy and specific microbiological techniques have been studied the development (cell multiplication) of Saccharomyces cerevisiae and Aspergillus niger growing and multiplication - both on culture media with sucrose and on those with starch. The experimental results have been revealed that the biochemical processes of the studied biomasses have significant changes in certain frequencies in the range 1 - 160Hz, characteristic of the different species/metabolized carbon source, respectively species/ metabolized carbon source/ development phase. It has also been found that in the case of Saccharomyces cerevisiae, the electric field of 50 Hz up to 20V/cm reduces the length of the LAG time and increases the growth rate of intensive increasing phase. Cultures of Aspergillus niger on culture medium with sucrose are stimulated (increasing the spores production by approx. 50% and reducing the maturity time) of 50Hz signals up to 15V/cm. Electric fields higher than 30 V/cm in all media and investigated cultures carry on to the growth reduction / multiplication - up to a complete inhibition of growth at approx. 50V/cm.

3

Authors: CÂRLAN M., CSUZI. I., COSTEA M.

This paper is presenting a method used to confirm the necessity of practicing maintenance works for two vehicles, tramways, whose operational statuses, defined by the levels of exploitation parameters, proved to be in precarious condition. Wear and tear has been the main cause leading to the occurrence of unnumbered moments when the vehicles were unavailable. Studies performed on data collected during a compelling enough period of time are highlighting, a tendency to increase the failure frequency with more than 10%. The wear and tear of the analyzed technical equipment is expressed by the status probabilities that are related to a later moment, and determined by using Markov chain theory, and entropic level - unit of measure for incertitude or chaos - phenomenons that are specific for system degradation - to be determined based on Shannon entropy concept[7],[11]. Based on these two sizes, the decision-maker may impose the optimal strategy regarding the maintenance works practice.[1]

5

Authors: BERINDE I., BRAD C.

Integration of wind power plant in medium voltage grid is comply with the same regulations as conventional plants. To realize in the point of common coupling grid, reactive power levels as close to zero is necessary to use reactive power compensators and ensuring the compensation. Static compensators STATCOM shunt satisfy this requirement very well, by absorption / injection of reactive power from / to grid based on the voltage amplitude the point of common coupling at grid. The article presents the behavior of wind power plant, which is connected to the compensator STATCOM, on medium voltage fault and the importance using it in the wind power plant

7

Authors: RUGINĂ V., BADEA A.

The paper presents the importance of evaluating energy efficient use that is explicitly stipulated in the strategic and legislative documents adopted at the national and international level, including the Directive 2012/27/EU and the Law 121/2014. Energy intensity frequently that is used in international evaluations and comparisons of energy efficient use is also used in Romania. The topic is approached both by specialists and politicians, newspapermen, representatives of the public opinion etc. This indicator has acquired axiomatic valences and its values are presented as unquestionable arguments for incontestable truths. Nevertheless, besides correct and well-balanced approaches one may come across distorted presentations and exaggerations resulting from superficially knowing the problem. The information and data presented in the paper can bring clarifications on this field. In the first place, energy intensity characterizes the economic efficiency of energy utilization and only to little extent the technical efficiency. Its value is directly linked to macroeconomic parameters, among which the parity between the national currency and the currencies in international circulation, the structure of the national economy etc. The paper presents different variants for the interpretation and calculation of the energy intensity indicator value, including the corresponding mathematical models. Based on the primary information obtained from reliable sources (National Institute of Statistics, EUROSTAT data base) values of this indicator are calculated in different variants that are considered and comparisons between the obtained results are made. Choosing the variant for defining and calculating energy intensity, respectively, depends on the purpose of the analysis to be carried out and needs to be explicitly presented together with the results obtained. The paper includes recommendations on how the calculation variants and the results obtained by carrying out these analyses according to their purpose (carrying out international comparisons, analyzing the evolution of internal situation in a certain period of time etc) should be used.

4

Authors: SETEL A, ANTAL C., BADEA G.

The paper presents the possibility of using geothermal energy in drying wood materials - a complex system with automatic control of the drying process.

5

Authors: RODEAN I., OLTEAN M.N., SEVASTRE I., BĂLAN V., MORAR N.D.

Using new technologies to equipment maintenance have a number of advantages well known. By applying these technologies work will achieve significant increases economic efficiency only if applied properly. In this sense it must be adequately trained staff, both maintenance operators and operational operators. CNTEE "Transelectrica" SA, through its policy, proposes the use of new technologies and LW technologies (live working). To develop and promote LW technologies and new technologies, the Company promoted the foundation of a centre for the training of personnel and development of new technologies. The centre will aim to promote new technologies and prepare personnel for the correct application of new technologies in our company and to increase readiness and effectiveness of actions taken by its own staff and authorize them for LW and other technology. Also the Centre can attest companies and their services and technologies. This paper presents some aspects of the Centre and how personnel receive the training services for more effective implementation of these technologies.

6

Authors: KILYENI ST., BARBULESCU C., DEACU A., AGAPE C.P

The paper tackles the artificial neural networks (ANN) based load forecasting issue. It aims to define a set of "standard" load curves. They are representing the background to perform a prognostic regarding the forecast quality based on known data set. A case study is used as an example. Daily load curves forecasting is performed. A software tool has been developed in Matlab environment. The results are compared with the ones obtained for "standard" load curves.

7

Authors: FELEA I., RANCOV N. , CHIREA V. , BOJA I., ȘINCA A., ALBUȚ D., FELEA A.I.

The paper is about de level of electricity quality in the power network and at power consumers from an urban area. The analysis was done at the request of local electricity company. After highlighting the importance of preoccupations, electricity nonquality effects and regulatory framework, in the paper is presented the working methodology and results synthesis. The last part of the paper contains the conclusions of the study.

3

Authors: JOIAN R., PETREUȘ D., PALAGHIŢĂ N., HORGOŞ M.

This paper point out some of the experimental determinations that must be made in the achieving of a hidro - wind hybrid system. It highlights the design and implementation of a1 kW ballast resistor and 48 V nickel-chromium wire, with the diameter of 60 three millimeters and connecting cable at the wind turbine by electric panel. Thus, this experimental stand CHHE includes a wind turbine 1 kW, placed on the roof of the Technical University of Cluj Napoca (this place is favorable because the wind has high speeds at great height) and hydro turbine type Pelton 1 kW power. The experimental stand for the study of CHHE hybrid energy system will allow the determination of more experimental conclusive on the impact of the achievement of an energy balance of the physical model.

6

Authors: VASIU I.

Thermal energy demand for district heating in the city of Oradea is supplied at present, almost at whole, by the Cogeneration Thermal Power Plant, based on classical fuels, mainly consisting of low grade coal and natural gas, with a small contribution of the geothermal energy. Geothermal resource at low enthalpy, located within the city area of Oradea, available at an estimated level of 250 GWh/year, exploited at present by 12 production wells, can provide a share of 55 GWh/year for district heating, representing at present about 7 % from the overall thermal demand at the end users inlet. Geothermal energy is delivered by means of 3 main thermal stations, in order to prepare, especially household warm water, but sometimes also secondary agent for space heating, using additionally heat, based on natural gas. At present, in the city area of Oradea, more than 7,000 dwellings are supplied by geothermal stations with warm water and in addition for about 3,400 dwellings is assured simultaneously warm water and space heating. Even if the geothermal energy provides at present only a small part of the overall heating requirement at the city level, nevertheless by increased financial support, in the near future is expected its much more contribution, as an alternative to polluting energy of coal and natural gas.

6

Authors: CLODNIȚCHI R., TANȚĂU A.D.

Romania is one of Europe’s traditional producers of energy from renewable sources. After the regime change 1989 nothing happened in this market until 2008 when the Romanian renewable sector went through a remarkable boom. 5.000 MW new capacities were installed mainly in wind, PV and biomass plants but almost none in biogas plants. There is plenty of substrate available, some of it for free, and the support mechanism is also very generous when it comes to biogenic gas, so how come today there are less than 15 MW installed in biogas capacities? This question lies at the base of our research covering several company intern and extern aspects. This particular article addresses the risks induced by technology vs. the market risks on the basis of a study case from Romania. We analyse the profitability indicators of the first landfill gas recovery facility from Romania which was after implementation less profitable than expected.