• Energy Research
• Closed Access close
• Restricted close
• Embargo close
• RS close

The economy is undergoing a radical transformation in all its structures, completely changing the methods of management. Changes are taking place on a global scale based on the digital technologies being implemented. The role of the state and executive authorities is being completely rethought. They are transforming themselves into “digital governments”, IT platforms, and forming their own digital structures with a list of services that are necessary for the population. In this study the following 4 directions of development of the public administration system were identified and reviewed in detail: digital reforms in the public administration system; long-term balance and sustainability of public administration; focusing on improving the quality and efficiency of public services; implementation of project management methods for the development and implementation of state programs. Based on the conducted research, current trends in public administration have been highlighted, and it was concluded that the trends in the development of modern economies include the mandatory participation of the state.

Abstract Further advance of glazed, healthy building's energy efficiency and sustainability is inextricable linked to the building's envelopes/facades fundamental physics study related to the dynamic control of sunlight and optimal control of solar heat gains. Relevant mathematical models and algorithms, as well as infrastructure/hardware and software integrated performance prediction and validation are studied. Reviewed is the most recent analytical and experimental research, current state of science and art, as well as some of the on-going R&D at the edge of new breakthroughs of the healthy buildings daylighting dynamic control's performance prediction and validation. It has been shown that, concerning the variability of the solar radiation spectra incident on the building's envelope, and also variability of outdoor and indoor air temperature differences, it is necessary tuning control of glazing's transmittance dependence on the solar radiation wavelength, with an aim to optimize daylighting with the reference to people needs (their health and comfort), and energy (thermal and electrical loads minimization). Finally, presented are elements of an analytical modeling approach, as initial results of study, aimed to reach a challenging research goal – Tuning control of buildings Glazing's transmittance dependence on the solar radiation wavelength to optimize daylighting and building's energy efficiency.

Abstract In this paper, a medium-term load forecasting model is proposed, intended to be used for the extrapolation of loads containing a small proportion of air conditioners. The main feature of the proposed model is the decomposition of weekly load observations into two independent components: trend line and seasonal variations. The trend line is described by the combination of the polynomial regression and the first-order autoregressive model. The parameters of this model are estimated with the aid of the generalized least-squares method. The seasonal component is modeled via a discrete model, where the weather sensitive cycle is separated from the weather insensitive one. A linear regression model is further proposed in order to associate weather sensitive variations with the exogenous weather variable (temperature). This procedure enabled a simple and efficient convolution of all load components into a single forecasting model. The whole methodology is verified on a real-life example of the peak-load consumption within the power system of former Yugoslavia.

Abstract Being widely used, personal computers (PCs) are, in relation to harmonics emission, very important within the category of non-linear low power loads (IL ≤ 16 A). A simultaneous operation of a group of PCs causes the distortion of the current waveform and negatively affects the supply of voltage. Therefore, the exact determination of current harmonics quantified with total harmonic distortion, THDI, is of great importance. The existing models and expressions for the THDI are not adequate in cases of large PC clusters. The aim of this paper is to present an improved analytical expression for the determination of the THDI dependence on the PC cluster size, suitable for practical engineering application. Based on the data available in references, the results of power quality measurements carried out in a computer centre on a group of 163 PCs, and the results of computer simulations, the THDI function on PC cluster size proposed in the paper is simple and easy to implement. The expression is suitable for engineering application for PC clusters up to 200 PCs per phase and for the most probable network connection of the cluster. It allows quick assessment of the current distortion, without the use of a simulation software. To improve the applicability, the influence of the stiffness of the grid is considered separately and then included in the enlarged expression. At the end, the effects of AC/DC power conversion, grid stiffness and cluster size on model application is further discussed. A direction for future research is also given.

This paper considers a unified problem of short-term operation planning and power exchange scheduling of large hydro-thermal power systems including: unit commitment, hydro power plant operation planning, pumped-storage hydro power plant operation planning and scheduling of power exchange with other power utilities. The criterion function is the total variable profit incurred by energy production, sales of energy to the users inside the power system, sales of energy to other power companies and purchase of energy from them, or from other sources. The overall problem is solved using the Lagrangian relaxation method. A decomposition technique is applied to solve the dual (mixed-integer) and primal (continuous programming) problem. Dynamic programming, feasible direction method and linear programming method are used for the solution of subproblems. The results of the application of the method to a numerical example are given. >

Transmission networks are being used more extensively to accommodate energy transactions that use the economic benefits of pooling. This paper evaluates the probabilistic wheeling capability of an interconnected power transmission system. Large electric power wheeling can degrade the reliability of the electric power network. This problem is also important for power system control and planning purposes. This paper discusses, from the viewpoint of power network reliability, the problem of power wheeling from Western Europe to Greece through the Yugoslav electric power system. The relative cost of the wheeling due to reliability indices is 2% of the production cost for the power wheeled. The calculation of reliability indices of wheeling enable more adequate estimation of the wheeling rate for power transactions between utilities. This paper describes an approach to calculate cost of the average energy not supplied and load curtailed due to wheeling. This cost can even be negative, which depends mostly on the amount of wheeling power and consumer loads. The reliability index EENS (expected energy not supplied) is more comprehensive than PI (performance index) for the contingency severity selection procedure. >

Abstract Due to space restrictions in Serbian cities near the city centers, additional storey may be constructed on the top of old multi-storey buildings that give new apartments. To investigate its influence to the heat consumption and the indoor air temperature in the below apartments, space heating of four buildings is investigated by using EnergyPlus simulations. All buildings are heated by using convection-type radiators with district hot water whose temperature is controlled by the outside temperature. The old building (5S) has 5 stories and does not have additional control of the hot water temperature. Each of other 3 new buildings presents the 5S plus the additional storey (a new-at-roof construction (NRC)) on top of it. The first 6-storey building (6S) is without any additional control of the hot water temperature. The second 6-storey building (6ST) has the additional control by thermostatic valves. The third 6-storey building (6S4T) has the additional control by thermostatic valves, and large radiators. The simulation of the 6S shows that the NRC increases the indoor air temperatures in the apartments and thus some heat is unnecessary wasted. The simulation of 6ST and 6S4T shows that the NRC may decrease the heating needs of the apartments below.

Abstract Green analytical chemistry is primarily directed towards minimization of the amount of waste associated with either the sample preparation or analysis. Among different chromatographic methods, liquid chromatography is considered the least green, allowing for various possibilities for greening. Using green solvents such as ethanol or acetone in RP-HPLC, as an alternative to acetonitrile, is recently attracting an attention. Both ethanol and acetone are characterized with low toxicity, with certain drawbacks limiting their regular use in RP-HPLC. Ethanol has low eluotropic strength and causes high backpressures, while acetone shows high UV cut-off, making it unsuitable for UV/Vis detection. To overcome the existing problems, Corona Charged Aerosol Detector was employed for development of RP-HPLC methods for separation of risperidone and its structurally related impurities with either ethanol or acetone as organic modifier. The methods were optimized by experimental design methodology, while optimal conditions for separation were determined using Derringer's desirability function. Detailed assessment of 3D surface plots of Derringer's desirability function enabled selection of 0.6 mL min−1 flow rate and 20% (v/v) organic modifier content as optimal when using ethanol, while in case of acetone mobile phase flow rate was 0.8 mL min−1 and organic modifier content 17% (v/v). Methods were validated and their eco-friendly character was confirmed through Green Analytical Procedure Index (GAPI). Although both methods are ecologically acceptable, the main drawback is reflected in the fact that no recycling or another waste treatment method exist. In the end, acetone was prioritized over ethanol, due to lower health hazard and decreased amount of generated waste.