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This paper analyzes the reality of sustainable energy supply (SEPS) from renewable energy sources (RES) as a totally green strategy of electric energy production. The paper is based on the Advanced International Policies (AIP) scenario of the European Renewable Energy Council agency forecast by the year 2040, which foresees the share of 82% of RES, extended to 100% of RES. The key element that creates conditions for achieving this ambitious scenario is an innovative solution of the so-called solar hydroelectric power plant (SHE) which is basically combined photovoltaic (PV) power plant and pump storage hydro (PSH) which can provide continuous supply of electric power and energy to consumers. Therefore, SHE is presented in this paper as the main building element of the future SEPS. For covering unit consumption of electric energy of 1 GWh in a power system, the paper calculates unit values of the SHE system: 0.73 MW of PV generator; 4,545 [m.sup.2] of PV generator; 0.36 h[m.sup.3] of reservoir volume, 0.21 GWh of PSH energy and 0.24 MW of PSH. In the case of the power system in Croatia, which is rich in solar and hydroenergy and whose climate conditions are very similar to those in the European countries, it has been shown that implementation of the green strategy of energy balance fulfilling can be realized with present day technology. Precisely, this fact shows that further increase of efficiency of SHE and other RES and their combining into RES+PHS power plants, along with increase in the cost of classic power fuels and the growing needs for environment protection, the proposed solution of SEPS realization could be widely important and thus become a serious alternative to the existing energy strategies and a guideline to decision makers in many countries. DOI: 10.1061/(ASCE)EY.1943-7897.0000027 CE Database subject headings: Sustainable development; Renewable resources; Solar power; Energy storage; Europe; Case studies. Author keywords: Sustainable development; Renewable resources; Solar energy; Photovoltaic; Energy storage; Energy policy.

This paper proposes a new kind of multifunctional energy system (MES) using natural gas and coal to more efficiently and more economically produce methanol and power. Traditional chemical processes pursue high conversion ratios of chemical energy o f fuels. The new MES focuses on the moderate conversion of the chemical energy of fuels. To do this, about 50% of the coal is partially gasified with pure oxygen and steam as oxidant, and then the unconverted residuals (char) and natural gas are utilized synthetically by char-fired reforming to generate syngas. The combustion of char drives the methane/ steam-reforming reaction. Here, the reforming reaction is also moderately converted, and the reforming temperature is decreased 100-150[degrees]C compared with that of the conventional method. The carbon-rich syngas from the partial gasifier of coal and hydrogen-rich syngas from char-fired reformer are mixed together and converted into methanol at a proper conversion ratio (lower than that of the conventional chemical process). Finally, the unconverted syngas is used in a combined cycle as fuel for power generation. As a result, the total exergy efficiency of the new system is 55-60%. Comparing to individual systems, including the integrated gasification combined cycle and the natural gas-based methanol synthesis plants, this new system can generate 10-20% more electricity with the same quantity of fossil fuel input and methanol output. In addition, the possibility of reducing the size of gasifier, reformer, and methanol synthesis reactor may reduce investment costs accordingly. These results may provide a new way to use coal and natural gas more efficiently and economically. [DOI: 10.1115/1.3205025]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2009.10.020 Byline: Bahman Shabani, John Andrews, Simon Watkins Keywords: Solar-hydrogen; PEM fuel cell; PEM electrolyser; Combined heat and power; Remote area; Cost analysis Abstract: A simulation program, based on Visual Pascal, for sizing and techno-economic analysis of the performance of solar-hydrogen combined heat and power systems for remote applications is described. The accuracy of the submodels is checked by comparing the real performances of the system's components obtained from experimental measurements with model outputs. The use of the heat generated by the PEM fuel cell, and any unused excess hydrogen, is investigated for hot water production or space heating while the solar-hydrogen system is supplying electricity. A 5kWh daily demand profile and the solar radiation profile of Melbourne have been used in a case study to investigate the typical techno-economic characteristics of the system to supply a remote household. The simulation shows that by harnessing both thermal load and excess hydrogen it is possible to increase the average yearly energy efficiency of the fuel cell in the solar-hydrogen system from just below 40% up to about 80% in both heat and power generation (based on the high heating value of hydrogen). The fuel cell in the system is conventionally sized to meet the peak of the demand profile. However, an economic optimisation analysis illustrates that installing a larger fuel cell could lead to up to a 15% reduction in the unit cost of the electricity to an average of just below 90c/kWh over the assessment period of 30years. Further, for an economically optimal size of the fuel cell, nearly a half the yearly energy demand for hot water of the remote household could be supplied by heat recovery from the fuel cell and utilising unused hydrogen in the exit stream. Such a system could then complement a conventional solar water heating system by providing the boosting energy (usually in the order of 40% of the total) normally obtained from gas or electricity. Author Affiliation: School of Aerospace Mechanical and Manufacturing Engineering, RMIT University, Melbourne, Australia Article History: Received 9 December 2008; Revised 3 August 2009; Accepted 26 October 2009 Article Note: (miscellaneous) Communicated by: Associated Editor S.A. Sherif

A new approach based on structured singular value is proposed for the robust decentralized Unified Power Flow Controller (UPFC) design. To achieve decentralization, using the schauder fixed point theorem the synthesis and analysis of Multi-Input Multi-output (MIMO) control system is translated into set of equivalent Multi-Input Single-Output (MISO) control system. Power systems such as the other industrial plants contain different kinds of uncertainties, which should be considered in controller design procedure. For this reason, the idea of [mu]-synthesis technique was used for designing of UPFC controllers. The proposed [mu]-based controller has a decentralized scheme and advantage of a decentralized controller design is reduction in the controller complexity and suitability for practical implementation. The effectiveness of the proposed control strategy was evaluated under operating conditions for damping low frequency oscillations in comparison with the classical controller to demonstrate its robust performance through nonlinear time simulation and some performance indices. Key words: UPFC, decentralized control, [mu]-synthesis, facts, power system stability and control, INTRODUCTION As power demand grows rapidly and expansion in transmission and generation is restricted with the limited availability of resources and the strict environmental constraints, power systems are today much [...]

This paper proposes an ac-linked hybrid wind/photovoltaic (PV)/fuel cell (FC) alternative energy system for stand-alone applications. Wind and PV are the primary power sources of the system, and an FC-electrolyzer combination is used as a backup and a long-term storage system. An overall power management strategy is designed for the proposed system to manage power flows among the different energy sources and the storage unit in the system. A simulation model for the hybrid energy system has been developed using MATLAB/Simulink. The system performance under different scenarios has been verified by carrying out simulation studies using a practical load demand profile and real weather data. Index Terms--Alternative energy, electrolyzer, fuel cell (FC), hybrid, photovoltaic (PV), power management, stand-alone, wind.

Measuring power loss accurately is of great importance for power electronics systems design and for assessing system performance and reliability. This paper reviews various power loss measurement techniques in power electronics systems. A brief overview of electrical methods for loss measurements is given. Calorimetric methods, which are considered the most accurate of this purpose, are described along with their implementations. The pros and cons of various techniques are discussed and compared for estimating the losses in integrated power electronic modules. Index Terms--Calorimetric methods, power loss measurement.

This paper presents a two-phase cooling method using the R134a refrigerant to dissipate the heat energy (loss) generated by power electronics (PEs), such as those associated with rectifiers, converters, and inverters for a specific application in hybrid-electric vehicles. The cooling method involves submerging PE devices in an R134a bath, which limits the junction temperature of PE devices while conserving weight and volume of the heat sink without sacrificing equipment reliability. First, experimental tests that included an extended soak for more than 850 days were performed on a submerged insulated gate bipolar transistor (IGBT) and gate-controller card to study dielectric characteristics, deterioration effects, and heat-flux capabilities of R134a. Results from these tests illustrate that R134a has high dielectric characteristics and no deterioration of electrical components. Second, experimental tests that included a simultaneous operation with a mock automotive air-conditioner (A/C) system were performed on the same IGBT and gate-controller card. Data extrapolation from these tests determined that a typical automotive A/C system has more than sufficient cooling capacity to cool a typical 30-kW traction inverter. Last, a discussion and simulation of active cooling of the IGBT junction layer with the R134a refrigerant is given. This technique will drastically increase the forward current ratings and reliability of the PE device. Index Terms--Power electronic (PE) cooling, thermal management, two-phase cooling.

The cost of electricity and operating reliability in heavy industry can be key in determining which processes and plants survive in today's competitive market. This paper will provide insight into the planning and implementation of several significant cost saving and reliability improvements at a turn-of-the-century steel mill in Ohio. A clear understanding of what to look for and how to proceed with such projects should provide motivation for others considering similar improvements.

The Superconducting Magnetic Energy Storage (SMES) technology has the capability to significantly improve electrical system operations within electric utility systems. This has been demonstrated by Bonneville Power Administration in a 30-MJ SMES demonstration unit (1). Savings in utility operations from improved system efficiency, increased reliability, and reduced maintenance requirements contribute to the economic justification of SMES. Beyond these benefits, there are additional benefits which in the long run may significantly outweigh the electrical operational benefits. These benefits are the energy conservation and environmental benefits. Since SMES can uncouple generation from load, it can shift generation around, thereby changing the operational characteristics of the system. The technology has the capability of reducing fuel consumption which can in turn reduce emissions. In a regional setting it can potentially shift emissions both in volumes and in physical areas to avoid problem situations. With its capability to strategically shift generation and significantly affect emissions and air quality it can 'stretch' clean energy generation options. With these attributes, SMES can be recognized as an energy and environmental management technology and tool.