Numerical Investigations of the Thermal State of Overhead Lines and Underground Cables in Distribution Networks

As part of extensive activities on the reduction of CO2 emissions, a rapid expansion of power generation using new more fuel efficient technologies (large, medium and embedded scale with combined heat and power (CHP) projects) and renewable energy (wind, biomass, solar PV) is currently taking place in numerous European countries, including the UK. The research presented in this thesis is a part of a UK government funded project, which aims to find answers to how to accommodate increased renewable energy into the distribution network. Current ratings, which are limited by the temperature of the conductors used in the distribution network, are based on worst case scenario conditions and are conservative. The temperature limits can be lifted if one takes into consideration the dynamic changes in the surrounding environmental conditions of the conductors. Implementation of real-time thermal rating of existing power systems could result in greater installed capacities of distributed generation (DG). This research aims to provide new insights into the thermal state of overhead line conductors (OHL) and underground cables (UGC) by using Computational Fluid Dynamic methods. An algorithm consists of building the geometry of the calculation domain, meshing, choosing a model, inputting initial conditions, initiation of the calculation, and analysing results. A part of the UK power system was chosen by Scottish Power Energy Networks for monitoring essential data of OHL conductors in order to validate results of the temperatures of the conductors

Development of a small solar thermal power plant for heat and power supply to domestic and small business buildings

The small solar thermal power plant is being developed with funding from EU Horizon 2020 Program. The plant is configured around a 2-kWel Organic Rankine Cycle turbine and solar field, made of Fresnel mirrors. The solar field is used to heat thermal oil to the temperature of about 240°C. This thermal energy is used to run the Organic Rankine Cycle turbine and the heat rejected in its condenser (about 18-kWth) is utilised for hot water production and living space heating. The plant is equipped with a latent heat thermal storage to extend its operation by about 4 hours during the evening building occupancy period. The phase change material used is Solar salt with the melting/solidification point at about 220°C. The total mass of the PCM is about 3,800kg and the thermal storage capacity is about 100kWh. The operation of the plant is monitored by a central controller unit. The main components of the plant are being manufactured and laboratory tested with the aim to assemble the plant at the demonstration site, located in Catalonia, Spain. At the first stage of investigations the ORC turbine will be directly integrated with the solar field to evaluate their joint performance. During the second stage of tests, the Latent Heat Thermal Storage will be incorporated into the plant and its performance during the charging and discharging processes will be investigated. It is planned that the continuous field tests of the whole plant will be performed during the 2018-2019 period

Novel Twin-Screw Stirling Cycle Machine for Cryogenic and Refrigeration Applications

This paper describes design and principles of operation of a novel rotary type Stirling cycle machines based on rotary positive displacement mechanisms such as twin-screw, gate rotor screw, scroll, and conical screw compressors and expanders. When these mechanisms are used as separate expanding or compressing machines, the flow of the gas is one-directional with volumes of chambers varying in accordance with a saw-tooth type function. The proposed design solution combines at least two units of gas-coupled compressor and expander arrangements with a required shift in the shaft angle. Every unit has a series of gas channels for timing the connection of its compressor and expander parts. Units are connected to each other via a set of heat exchangers, which are conventional for Stirling cycle machines: recuperative cooling and warm heat exchangers with a regenerator, built between them. The operational capability is demonstrated using three-dimensional CFD simulations. Computational results demonstrate reciprocating flow of the gas between units, as in conventional Stirling machines, and functioning of the proposed design as a multi-cylinder, double acting Stirling machine. The suggested design makes it possible to achieve full dynamic balancing, especially in the case of twin-screw and gate rotor mechanisms, due to the rotation of screws around their axes. It also eliminates a number of problems, which are specific to Stirling machines with reciprocating pistons and their kinematic drive mechanisms

A novel small dynamic solar thermal desalination plant with a fluid piston converter

An innovative small dynamic water desalination plant was developed and tested under laboratory conditions. The system is a combination of a heat pipe evacuated tube solar collector, conventional condenser and novel fluid piston converter. Saline water is boiled and turned into vapour in the manifold of the solar collector. A small fraction of the solar energy supplied to the plant is used to drive the fluid piston converter. Oscillations of the fluid piston periodically change the volume and pressure in the plant. For the duration of approximately half of the periodic cycle the pressure in the plant drops below the atmospheric level causing flash boiling of saline water in the manifold of the solar collector. Generated vapour is turned into fresh water in the condenser which is surrounded by a cooling jacket with saline water. The flash boiling effect improves the fresh water production capacity of the plant. Additionally, the fluid piston converter drives a pump which provides lifting of saline water from a well and pumps this through the cooling jacket of the condenser to a saline water storage tank. This tank replenishes saline water in the manifold of the solar collector. Experimental investigations demonstrated the saline water self-circulation capability of the plant and increase in the fresh water production compared to the static mode of operation. Experimental data was also used to calibrate the mathematical model of the plant. Comparison of theoretical and experimental information demonstrates that the model accurately predicts the performance of the plant. The proposed novel system with greater fresh water production capacity has a simple design and is easy to manufacture using low cost materials and therefore can be mass deployed for small scale saline water pumping and desalination across different regions with the relatively high solar radiation and shortage in the drinking water supply

CFD analysis of the thermal state of an overhead line conductor

At present commercial CFD packages such as Fluent, ANSYS CFX, and Star-CD are widely used for investigation of heat and mass transfer processes in various fields of engineering. These codes can also be successfully applied to estimate the thermal state of major components of electrical distribution networks, such as overhead lines, underground cables and transformers. This paper presents some results obtained from numerical modelling of the temperature field in the Lynx overhead conductor in both cross and parallel wind conditions using 2-D and 3-D CFD models. The CFD results obtained demonstrate that for an applied load of 433 A and considering the summer rating (Lynx conductors ER P27 [1]) the maximum temperature in the conductor is considerably lower (16 degrees) than the prescribed design conductor temperature. This indicates that there is headroom for increasing the ampacity of the conductor

УПРАВЛЕНИЕ МОТИВАЦИЕЙ ТРУДА МУНИЦИПАЛЬНЫХ СЛУЖАЩИХ (НА ПРИМЕРЕ ОПРОСА ПЕРСОНАЛА АДМИНИСТРАЦИИ г. ШАХТЫ РОСТОВСКОЙ ОБЛАСТИ)

The authors studied the theoretical and methodological framework for the assessment of enterprise competitiveness. Novelty - Evaluation of an anonymous survey of employees the Rostov region on the theme: "The satisfaction of working conditions and their impact on the competitiveness of the enterprise". There are challenges "points" to the sustainable development and competitiveness of the enterprise in a competitive environment.Purpose: identification of influence of working conditions on productivity of work of employees.Methodology: anonymous questioning.Results: a number of practical actions for a sustainable development of the organization are offered.Practical implications: the staff of the organizationВ статье авторами предложены инструменты для повышения мотивации сотрудников. Новизна – комплексная оценка удовлетворенности муниципальных служащих условиями труда по результатам анонимного опроса сотрудников Администрации  г.Шахты Ростовской области, и выявление влияния данных факторов на результативность их работы. Предложен  ряд практических мероприятий для устойчивого развития организации.Цель выявление влияния условий труда на результативность работы сотрудников.Метод: анонимное анкетирование.Результаты: предложен  ряд практических мероприятий для устойчивого развития организации.Область применения: коллектив организации

Melting and solidification of PCMs inside a spherical capsule: A critical review

To date, numerous phase change materials (PCM) have been developed for application in latent heat storage systems. There are many issues in the process from the development of PCM to using them in storage systems, which should be resolved. The problem of heat transfer in PCMs during the phase change process is the most important one. Latent heat storage containers usually have simple geometrical forms such as a sphere, cylinder, cylindrical annulus, rectangular enclosure, etc. A large number of papers were published on melting and solidification processes in PCMs. Therefore, there is a pressing necessity for generalizing the art of the state in this field and establish how accumulated knowledge meets practical requirements. The present review considers the current state in investigations of heat transfer in a spherical shell. Heat transfer in PCMs during constrained melting (solid PCM fixed inside the vessel), unconstrained (unfixed) melting and solidification, and phase change in finned shells are analyzed. It is shown that currently, there is no satisfactory description of the constrained melting process. For unconstrained melting and solidification, some correlations are suggested, describing these processes. The applicability range of the proposed correlations, as well as their accuracy were investigated and established. To intensify the process of phase change inside the spherical container, the use of orthogonal fins is appropriate option compared to the employ of circumferential fins

CFD thermal modelling of Lynx overhead conductors in distribution networks with integrated Renewable Energy Driven Generators

Results presented on application of a CFD technique for determination of the thermal state of a Lynx overhead conductor, used in power distribution networks. The thermal state of the Lynx conductor is mainly defined by the magnitude of the transmitted electrical current, ambient temperature, wind velocity and its direction and also by solar radiation. CFD modelling provides engineers with a capability to fully reflect in the process of numerical simulations variations of the above parameters over a range which is typical for real exploitation conditions. Results for both the steady-state and transient responses have been obtained and compared to those predicted by industrial standards and available from experimental data. Time constant values were obtained for various scenarios in which there was an instantaneous change in the magnitude of the electrical current or wind velocity. Analysis of numerical results demonstrate that the CFD technique provides an adequate level of accuracy in predicting the thermal state of the overhead conductor and could be a viable option for the dynamic analysis of distribution networks with a number of renewable energy generators, operating under varying electrical load and weather conditions

Prediction of the time constant of small-scale concentrated solar CHP plants

The operation of a power plant based on solar energy can vary significantly with time because of the intrinsic intermittency of the energy resource. Hence, a smart management is required to deal with the complex dynamic variations of the different subsystems. In order to do that, different control logics can be implemented but their effectiveness strictly depends on the temporal evolution of the parameters considered. For a given plant configuration, their exact estimation can be obtained through experimental tests during the commissioning of the plant. However, any change in the design parameters of the plant reflects in a different time constant, whose preliminary knowledge may be of support in tuning the control logic of the plant during the design stage. Therefore, based on the configuration of a small-scale concentrated solar combined heat and power plant as designed and built under the EU funded project Innova MicroSolar by several universities and companies, in this study a prediction of the time constant of several plant configurations with varying solar multiple and size of the storage tank is performed. By making use of the dynamic simulator previously developed by some of the authors, an estimation of such characteristic is assessed in case of potential redesign of the plant, providing also useful suggestions into the design of the control logic