Performance analysis and improvement of geothermal binary cycle power plant in oilfield

In order to improve the efficiency of a geothermal power plant, oil wells in the high water cut stage were used as geothermal wells, thereby improving the recovery ratio and economic benefit. A new function that reflects both the technical and economic performances was put forward and used as the objective function. An organic Rankine cycle (ORC) was analyzed through the energetic and exergetic analyses, and the reasons for low efficiency were pinpointed. Results indicate that geothermal water directly transferring heat to the working fluid reduces energy dissipation and increases cycle efficiencies. The net power output with an internal heat exchanger (IHE) is averagely 5.3% higher than that without an IHE. R601a and R601 can be used to replace R123 for geothermal water below 110℃. Moreover, the modified ORC dramatically outperforms the actual one.

First-Principle Studies on Conductive Behaviors of P-Type ZnO Codoped by N and B

Using a first-principle method, the electronic structures and the impurity formation energy of ZnO, ZnO （N）, ZnO （N＋B）, and ZnO （2N＋B） have been calculated, based on which the feasibility to obtain p-type ZnO ＆ discussed. According to the results, when ZnO is single doped by N, the acceptor level is deep, and the formation energy is negative, so the ideal p-type ZnO can not be obtained by this way. On the contrary, when 2N＋B are codoped into ZnO, the acceptor level becomes much lower, and the formation energy is positive, so it is a better way to obtain p-type ZnO.

Microstructure, texture and tensile properties of Mg-1 OSn alloys extruded in different conditions

Indirect extrusion of Mg-10%Sn (mass fraction) alloys was performed at three different working temperatures. The effect of working temperature on the microstructure, texture and tensile properties of the extruded alloys was investigated by optical microscope (OM), scanning electronic microscope (SEM), X-ray diffraction (XRD) and a standard universal testing machine. Grain size, area fraction of second phase particles and texture of the alloys are found to be significantly influenced by working temperature. The grain size refinement is greatly dependent on processing conditions with the low working temperature being the most effective. While the high working temperature results in a coarser grain size and a stronger fiber texture and the reason for this phenomenon was examined in terms of second phase particle, grain type and dynamic recrystallization mechanism. Tested in the different conditions, the tensile strengths of the Mg-10Sn alloys extruded at the high working temperature are remarkably better than those of the other studied alloys. This significant improvement in tensile properties is mainly due to the particle strengthening and texture strengthening resulted from the more and finer primary dispersed particles and stronger texture, respectively.

Effects of Large-Scale Wind Energy Base on Power Grid Company

The first stage project of Jiuquan wind energy base with 5.5-GW installed capacity is about to be completed. However, there exist several technical issues such as power transfer capability, electricity accommodation, frequency control and peak load regulation as well as system stability. In addition, the high capital cost and operation cost of the supporting transmission project invested and constructed by the Gansu Provincial Power Company will definitely have significant impacts on the management and economic profit of the Company. Through analysis of the construction and operation cost changes resulting from the wind power collection and delivery project, the author carried out research into the effects of developing large-scale wind power base on the management and economic benefits of power grid enterprises and proposed corresponding suggestions to make the related policies perfect.

Status in quo and future of geothermal energy in China

Energy saving and CO2 emissions reduction are critical tasks currently,and great effort has been made by Chinese government. Renewable energy consumption and CO2 emissions and reduction plan in China are introduced in this paper. Analysis is also made on present status and prospect of geothermal power generation and direct use in China respectively. Now,there is a new understanding of geothermal resources,and hot dry rock,considered as the future of geothermal resources,is likely used to generate electricity.

Alternative Solutions to Mitigate Problems due to Neutral Conductors Theft in MV （Medium Voltage） Power Distribution Systems

This paper aims at analyzing the impact of the neutral conductor absence at specific sections over the performance of the power distribution lines, and proposing alternative solutions to mitigate the problems caused by the neutral conductor theft. Simulations are made by the software lnterplan and show that the absence of neutral conductor at specific sections of power distribution lines may increase the neutral-to-ground voltages, which compromises the system＇s safety. The solution developed keeps the technical performance of the power distribution system at satisfactory levels, regarding the voltage profile, or, at least, close to the level before the neutral conductor＇s theft.

Geospatial Solutions in Practice for Smart Grids

Recently, smart grid solutions have started to extend the visibility of the electrical grid to the entire network; including high voltage transmission lines, medium voltage distribution networks, and the low voltage networks to households. The typical data monitored includes： voltage, current, phase, and power measurements, together with network events and alarms. This paper analyses the key challenges facing smart grid solutions in providing effective access to large volumes of sensory data that is distributed over a large geographic area. A case study is described that outlines how the use of geospatial technology together with Web 2.0 technologies may be applied to improve user access and control to this data. The results show that a geospatial solution provides an effective mechanism for visualizing telemetry data monitored within the smart grid.

The tragedy of the commons and energy price depression of China

This article indicates by example about power price of Henan province that the energy resources of Henan province are ＂the commons＂. According to analysis of the game of ＂the tragedy of the commons＂, this article demonstrates that, whether under complete information or not, energy commons are abused. Based upon the situation, the author gives out the strategy to solve ＂the tragedy of the commons＂ of China energy sources.

The Environmental Factors and Strategic Priorities in Northwest Power Development

Based on the energy distribution and economy status In the Northwest Region in China, this paper analyzes the probability of power sources complementation between Northwest Power Grid and the adjacent regional power grids, and points out that the strategic emphases for Northwest power development are to speed up 750 kV transmis-sion system construction, expand the Regional power market, rolling-develop hydrdpower stations on the Upper Yellow River, speed up thermal power bases construction and boost the interconnection between Northwest and North China, etc.

Quasi-Horizontal Arrangement of Solar Panels in Equatorial Zones： Problems and Proposed Solutions

Solar panels are oriented to the North （South） when the site is in the South （North） with a tilt angle close to the latitude. In the equatorial zone, the panels are quasi-horizontally arranged. This situation caused some problems： the panel is more rapidly covered with dust or salty mud that decreases its performance and degrades the protective glass. To overcome these difficulties, we evaluated theoretically and practically the energy lost by an incorrect tilt. The results are rather encouraging. Just 1.5% of total energy is lost when we tilted the panel at 10.0°. In practice, we realized that the loss of energy is fewer than we calculated it because of the reflected solar rays.

Optimizing Geothermal Energy Resource

Unlike other types of renewable energy resources, geothermal energy provides a stable source of energy as it can be exploited regardless of meteorological conditions. Using organic cycle, geothermal energy can be utilized for power generation. In such systems, the heat is exchanged between the surrounding rock mass and transport fluid. Consequently, the temperature of extracted geofluid from the well decreases with the time in accordance with the working parameters. Those parameters includeenergy extraction rate, temperature difference between inlet and outlet of the well, and the thermal conductivity of the ground. Current work, aims to develop a reliable computer model to specify the optimal working parameters so that the geofluid temperature will not reach a low value that is not acceptable for electricity generation, and the energy availability of geothermal resource is maximized. In the current study the ground thermal properties, the geothermal gradient and well dimensions are based on realistic data in Qatar and neighboring countries. The proposed model was developed for different heat extraction rate, different ground thermal properties, and for varied temperature difference between inlet and outlet of the well. Simulation shows that selecting the optimal working parameters can increase the availability of geothermal resource significantly.

Concentrating Solar Power in Europe, the Middle East and North Africa： Achieving Its Potential

CSP （concentrating solar power） is a commercially available renewable energy technology capable of harnessing the immense solar resource in southern Europe, the MENA region （Middle East and North Africa）, and elsewhere. This paper summarises the findings of a study by the European Academies Science Advisory Council which has examined the current status and development challenges of CSP, and consequently has evaluated the potential contribution of CSP in Europe and the MENA region to 2050. It identifies the actions that will be required by scientists, engineers, policy makers, politicians, business and investors alike, to enable this vast solar resource to make a major contribution to establishing a sustainable energy system. The study concludes that cost reductions of 50%-60% in CSP electricity may reasonably be expected in the next 10-15 years, enabling the technology to be cost competitive with fossil-fired power generation at some point between 2020 and 2030. Incorporation of storage delivers added value in enabling CSP to deliver dispatchable power. Incentive schemes will be needed in Europe and MENA countries to enable this point to be achieved. Such schemes should reflect the true value of electricity to the grid, effectively drive research and development, and ensure transparency of performance and cost data.

Comparative Study on Telecommunications Base Stations＇ Power Supply Systems on Remote Sites in the Northern Part of Cameroon

The TBS （telecommunications base stations） on remote sites in the northern part of Cameroon are mainly supplied by a system of two generating units. Only a few TBS located in the Waza and Benue National Parks are powered by a PV （photovoltaic） solar system to avoid any disturbance to wildlife. It is against this background that we decided to do a comparative study on these two systems. This study focuses on the reliability of electrical quantities, the environmental impact and the installation and operating costs of these two major systems namely the GU （generating unit） system comprising two generating units and the PV system. In conducting this study, we took a sample of TBS including those located in the Badjouma and Waza localities. After collecting data from mobile telephony operators, measurements of electrical quantities on the sites for twelve consecutive months and updating costs, their operation reveal indicators that are surprising, to say the least. Concerning the reliability index, the PV system is estimated at 99.9% as against 97.8% for the GU system. As for environmental impact, the mass of CO2 released by the GU system reached 1,707.5 tons in 25 years for a single TBS while the PV system produced no emissions. In addition to its contribution to climate change, the GU system pollutes its immediate environment through the spillage of waste and production of deafening noise. On the other hand, economic analysis shows mixed results. The GU system has a lower installation cost of $6,640 as against $174,550 for the PV system, whose investment cost is its main handicap. Regarding operating costs, the GU system peaks at $923,940 in 25 years while the PV system requires only $487,550 for the same duration.

Maps of International Research Collaboration in Clean Energy

Clean energy is the most promising technology for sustainable growth. The development of clean energy requires a considerable amount of R ＆ D （research ＆ development） expenditure and various core technologies, and therefore, international research collaboration is necessary for prompt and efficient development. The study is aimed at establishing a knowledge base that can help to prepare international research collaboration policies for solving global challenges effectively. The authors demonstrate the research capacity and international research collaboration in solar cell and fuel cell technologies, using global research network diagrams gathered from 35,322 and 33,136 academic papers, respectively. The diagrams include the data of research competency and co-authorship. More than 6,000 institutions and 100 countries are involved in each field. Based on the diagrams, the technologies are compared and international collaboration is analyzed. A valley of research collaboration in Asia is identified for both technologies. Then, science and education policies that influence the structures are discussed.

Renewable Energy Sources and Pricing of Electrical Power

This report deals with some characteristics of the electric power system of Bulgaria. Emphasis is put on the benefits of joining the small photovoltaic plants in the tourist areas of the country. As an example of that the town of Pomorie is examined. Data on the quality of the consumed electric energy and the price per a four-member family are presented. The amount of the solar radiation for the town of Pomorie is audited through the PVGIS （Photovoltaic Geographical Information System）. Discussed are the types of photovoltaic panels offered on the market by manufacturers in terms of the received power efficiency. Developed is a model of creating a photovoltaic system on the roof of a house, inhabited by several families. Calculations are made on the cost of the electricity generated by the proposed system. Compared is the cost of the electricity supplied by the electricity provider EVN （Energie Verntinftig Nutzen） in the town of Pomorie to the one that will be obtained using the proposed PV-system.

Taiwan Residents Learners＇ Motivation and Attitude Towards Completing an Online Distance Education Course During a One Year Industrial Placement

This mixed methods study investigated language learning motivation in an one-year e-learning course for technological university students to bridge the geographical divide between students on industrial placements when studying graded readers using an e-learning course to improve their English competence and to pass the General English Proficiency Test. Data was collected through questionnaires and course feedback. The results of this study extend Gardner＇s socio-educational model in an e-learning environment by adding the new category, Computer Attitudes, which was proven to be highly correlated with Motivation. Although the low proficiency English students had good computer skills, their habits of using the computer for entertainment and their lack of the skill of ＂technological communication efficacy＂ caused increased anxiety when using computers and thus provided them with a lower computer confidence over time. Consequently, it is recommended that sound e-learning training should be provided to all of the students prior to embarking on an e-leaning course so that these learners can benefit from online language learning in the future.

A new capacitive borehole tiltmeter for crustal deformation measurement and its performance analysis

Borehole inclinometers are important observation instruments used to measure ground tilt movement and monitor crustal deformation of solid tides and geological landslide disasters.They are widely used in oil exploration,mineral resource drilling,well logging,exploration and other fields.There is potential for development of rock stress strain monitoring tools.Many types of tiltmeters have been installed,such as SQ-7,FSQ,VS and JB.However,these tiltmeters are generally installed in a deep cave to avoid the interference of temperature,humidity,and human activities.With the urbanization of human society,suitable installation locations are difficult to find.To solve the problem,a two-component borehole tiltmeter,named the CBT-type tiltmeter,is proposed in this paper.It can be installed in a borehole less than500 m deep to eliminate environmental influences.The tiltmeter is composed of two sophisticated gravitational swing and two capacitive transducers.From preliminary theory and experiment analysis,its linear correlation coefficient is higher than 0.99,its co-seismic response is rapid and its noise level is up to 10 4arc seconds in practice.

回顾与展望

在邓小平同志和党中央、国务院直接关怀下建立起来的广播电视大学,已走过了十个年头。回顾十年成就,展望未来事业,深深感到中央关于建立和发展广播电视大学的决策非常正确,也深感今后的任务光荣而艰巨。

Electron dynamics and wave activities associated with mirror mode structures in the near-Earth magnetotail

We report the observation of mirror mode structures by Cluster spacecraft at around X^-16 RE in the Earth’s magnetotail.The wavelength of the mirror structure is larger than 7000 km,corresponding to tens of ion gyroradii.Features of the mirror structures are similar to those detected in the magnetosheath:the anti-correlation between the magnetic field strength and plasma density,zero phase velocity in the plasma rest frame and linear polarization.The structures were observed in a region bounded by two dipolarizations during a substorm intensification.Thus,the dipolarization process may provide a plasma condition facilitating the growth of the mirror mode structures.Another interesting feature is the electron dynamics within the mirror structures.Thermal electron energy flux has an enhancement at 0°and 180°pitch angles inside the magnetic dips of the first three mirror structures and an enhancement at 90°pitch angle inside the magnetic dip of the last structure.The different electron distribution inside the mirror structures might be a result of different evolution stages of the mirror wave.The last structure may be in the nonlinear stage of the mirror instability,whereas the three others with quasi-sinusoidal waveforms may be in the linear stage.In addition,we found that intense whistler waves were confined within the magnetic dips.We conjecture that whistler waves observed in the first three dips were generated in a remote region,then they were trapped in the mirror mode troughs and transported toward the spacecraft;while the whistler wave detected in the last dip was excited locally by the electron anisotropy instability.

An analysis of the correlation between the fluxes of high-energy electrons and low-middle-energy electrons in the magnetosphere

The variation of the flux of energetic electrons in the magnetosphere has been proven to be strongly related to the solar wind speed. Observations of GEO orbit show that the flux of low-energy electrons is not only modulated by the solar wind speed, but, if a time delay is added, is also positively correlated to the flux of high-energy electrons. This feature provides a possible method to forecast the flux of high-energy electrons in GEO orbit. In this study, the correlations of the fluxes between the high-energy electrons and low-middle-energy electrons obtained at different L values and in different orbits are investigated to develop the application of this feature. Based on the analysis of long–term data observed by NOAA POES and GOES, the correlations between the fluxes of high-energy electrons and low–middle–energy electrons are good enough at different L values and in different orbits in quiet time, but this correlation is strongly affected by CME–driven geomagnetic storms.