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1 Sep 2009

Volume 1, Issue 5, Articles (05xxxx)

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Recent advances in direct solar thermal power generation

Yue-Guang Deng and Jing Liu

J. Renewable Sustainable Energy 1, 052701 (2009); http://dx.doi.org/10.1063/1.3212675 (23 pages) | Cited 1 time

Online Publication Date: 2 October 2009

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The recent energy crisis and environmental burden are becoming increasingly urgent and drawing enormous attention to solar-energy utilization. Direct solar thermal power generation technologies, such as thermoelectric, thermionic, magnetohydrodynamic, and alkali-metal thermoelectric methods, are among the most attractive ways to provide electric energy from solar heat. On the one hand, these methods have the potential to be more efficient than traditional ways since they can convert heat to electricity directly without experiencing the conventional intermediate mechanical energy conversion process; on the other hand, these electricity generators are generally silent, reliable, and scalable, making them very suitable to serve as a distributed power generation system for certain specialized fields, such as military and space applications. A lot of effort has been devoted to investigate the energy conversion theory and practical applications thus far. This paper is intended to present a thorough review on recent advances in developing the thermoelectric, thermionic, magnetohydrodynamic, and alkali-metal thermoelectric technologies for direct solar thermal power generation. Both the fundamental issues and latest application research are illustrated and critical issues are discussed. The paper concludes with a description of future developments expected in the subjects covered.
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88.40.-j Solar energy
07.87.+v Spaceborne and space research instruments, apparatus, and components (satellites, space vehicles, etc.)
88.05.-b Energy analysis
84.60.Rb Thermoelectric, electrogasdynamic and other direct energy conversion
84.60.Lw Magnetohydrodynamic conversion
84.60.Ny Thermionic conversion
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Energy use and environmental impacts: A general review

Abdeen Mustafa Omer

J. Renewable Sustainable Energy 1, 053101 (2009); http://dx.doi.org/10.1063/1.3220701 (29 pages) | Cited 3 times

Online Publication Date: 18 September 2009

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Globally, buildings are responsible for approximately 40% of the total world annual energy consumption. Most of this energy is for the provision of lighting, heating, cooling, and air conditioning. Increasing awareness of the environmental impact of CO2 and NOx emissions and chlorofluorocarbons triggered a renewed interest in environmentally friendly cooling and heating technologies. Under the 1997 Montreal Protocol, governments agreed to phase out chemicals used as refrigerants that have the potential to destroy stratospheric ozone. It was therefore considered desirable to reduce energy consumption and decrease the rate of depletion of world energy reserves and pollution of the environment. One way of reducing building energy consumption is to design buildings that are more economical in their use of energy for heating, lighting, cooling, ventilation, and hot water supply. Passive measures, particularly natural or hybrid ventilation rather than air conditioning, can dramatically reduce primary energy consumption. However, exploitation of renewable energy in buildings and agricultural greenhouses can also significantly contribute toward reducing dependency on fossil fuels. Therefore, promoting innovative renewable applications and reinforcing the renewable energy market will contribute to preservation of the ecosystem by reducing emissions at local and global levels. This will also contribute to the amelioration of environmental conditions by replacing conventional fuels with renewable energies that produce no air pollution or greenhouse gases. The provision of good indoor environmental quality (IEQ) while achieving energy and cost efficient operation of the heating, ventilating, and air-conditioning plants in buildings represents a multivariant problem. The comfort of building occupants is dependent on many environmental parameters including air speed, temperature, relative humidity, and quality in addition to lighting and noise. The overall objective is to provide a high level of building performance, which can be defined as IEQ, energy efficiency (EE), and cost efficiency (CE). IEQ is the perceived condition of comfort that building occupants experience due to the physical and psychological conditions to which they are exposed by their surroundings. The main physical parameters affecting IEQ are air speed, temperature, relative humidity, and quality. EE is related to the provision of the desired environmental conditions while consuming the minimal quantity of energy. CE is the financial expenditure on energy relative to the level of environmental comfort and productivity that the building occupants attained. The overall CE can be improved by improving the IEQ and the EE of a building. The increased availability of reliable and efficient energy services stimulates new development alternatives. Anticipated patterns of future energy use and consequent environmental impacts (acid precipitation, ozone depletion, and greenhouse effect or global warming) are comprehensively discussed in this paper. Throughout the theme several issues relating to renewable energies, environment, and sustainable development are exam-ined from both current and future perspectives. It is concluded that renewable environmentally friendly energy must be encouraged, promoted, implemented, and demonstrated by full-scale plant especially for use in remote rural areas.
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88.05.Sv Energy use in heating and cooling of residential and commercial buildings
88.05.Tg Energy use in lighting
89.30.-g Fossil fuels and nuclear power
89.60.-k Environmental studies
92.60.Sz Air quality and air pollution

A novel pulse width modulation for grid-connected multilevel inverter

J. Selvaraj and N. A. Rahim

J. Renewable Sustainable Energy 1, 053102 (2009); http://dx.doi.org/10.1063/1.3204460 (15 pages)

Online Publication Date: 18 September 2009

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This paper presents a single-phase five-level grid-connected photovoltaic inverter with a novel dual reference modulation technique. Two reference signals identical to each other with an offset equivalent to the amplitude of the triangular carrier signal were used to generate pulse width modulation (PWM) signals. The inverter consists of a full-bridge inverter and an auxiliary circuit comprising of four diodes and a switch. The inverter produces output voltage in five levels: 0, +1/2Vdc, Vdc, −1/2Vdc, and Vdc. A digital proportional-integral (PI) current control algorithm is implemented in DSP TMS320F2812 to keep the current injected into the grid sinusoidal and to have high dynamic performance with low total harmonic distortion (THD). The validity of the proposed inverter is verified through simulation and is implemented in a prototype. The experimental results are compared to conventional single-phase three-level grid-connected pulse width modulation (PWM) inverter in terms of THD.
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84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
84.60.Jt Photoelectric conversion
88.40.mp Grid-tied solar electric systems
84.30.Jc Power electronics; power supply circuits

Comparison of the recently proposed super-Marx generator approach to thermonuclear ignition with the deuterium-tritium laser fusion-fission hybrid concept by the Lawrence Livermore National Laboratory

F. Winterberg

J. Renewable Sustainable Energy 1, 053103 (2009); http://dx.doi.org/10.1063/1.3253693 (12 pages) | Cited 1 time

Online Publication Date: 29 October 2009

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The recently proposed super-Marx generator pure deuterium microdetonation ignition concept is compared to the Lawrence Livermore National Ignition Facility (NIF) Laser deuterium-tritium fusion-fission hybrid concept (LIFE). In a super-Marx generator, a large number of ordinary Marx generators charge up a much larger second stage ultrahigh voltage Marx generator from which for the ignition of a pure deuterium microexplosion an intense GeV ion beam can be extracted. Typical examples of the LIFE concept are a fusion gain of 30 and a fission gain of 10, making up a total gain of 300, with about ten times more energy released into fission as compared to fusion. This means the substantial release of fission products, as in fissionless pure fission reactors. In the super-Marx approach for the ignition of pure deuterium microdetonation, a gain of the same magnitude can, in theory, be reached. If feasible, the super-Marx generator deuterium ignition approach would make lasers obsolete as a means for the ignition of thermonuclear microexplosions.
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28.52.Cx Fueling, heating and ignition
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

Reduction of NOx in the exhaust gas of DI- diesel engine fueled with mahua methyl ester along with exhaust gas recirculation

V. J. J. Prasad, N. Hari Babu, and B. V. Appa Rao

J. Renewable Sustainable Energy 1, 053104 (2009); http://dx.doi.org/10.1063/1.3255043 (14 pages)

Online Publication Date: 30 October 2009

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Biodiesels are alternative fuels for petroleum-based diesel without major modifications of engine. In the environmental aspect, also biodiesel gives fewer pollutants than petroleum diesel. However, the NOx level is slightly higher. To reduce NOx, some of the methods are being used, which include direct injection, turbocharging, air-to-air intercooling, combustion optimization with and without swirl support, multivalve cylinder head, advanced high pressure injection system, i.e., split injection or rate shaping, and electronic management system. However, technologies such as exhaust gas recirculation (EGR), soot traps, and exhaust gas after treatment are gaining emphasis to cater to the challenges posed by increasingly stringent environmental emission legislations. In this work, experimentation was conducted on a single cylinder diesel engine with mahua methyl ester (MME) in the neat form along with the cooled EGR and performance, combustion pressure, and emission parameters are collected by using suitable instrumentation. Same experimentation was repeated for the petroleum diesel and a comparison was made to evaluate the applicability of MME along with EGR without major modifications. After the analysis of results, it was found that 5% EGR is recommendable with neat biodiesel (MME) run, and in most of the situations, it proved its merit over neat diesel run.
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89.20.Kk Engineering
89.60.-k Environmental studies
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