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02916 Spanish method of visual impact evaluation in wind farms
07 Alternative energy sources (ethers, including development, economics) density distributions), calculated from 12 months of hourly time series wind speed data. It is shown that the degree of suitability of a given function changes to a great extent with the parameter on which the judgement is based.
04/02915 Power regulation in pitch-controlled variablespeed WECS above rated wind speed Bianchi, F. D. et al. Renewable Energy, 2004, 29, (11), 1911-1922. In medium to large scale wind energy conversion systems (WECS), the control of the pitch angle of the blades is an usual method for power regulation above rated wind speed. However, limitations of the pitch actuator have a marked influence on the regulation performance. In variable-speed mode, the control of the generator torque is able to reduce the effects of the pitch actuator limitations. Nevertheless, in this case the system is multiple-input multiple-output (MIMO) and then the control design results more complex. In this situation advance control techniques, such as optimal control, are an interesting option for a systematic controller design. This work analyses variable-pitch power regulation above rated wind speed in the context of optimal control. The analysis is approached from a new point of view in order to establish a clear connection between the choice of the optimization criteria and the compromise between power regulation and pitch actuator limitations.
04/02916 Spanish method of visual impact evaluation in wind farms Hurtado, J. et al. Renewable and Sustainable Energy Reviews, 2004, 8, (5), 483-491. The present Spanish laws on the procedure to evaluate the environmental impact of wind farms are ambiguous, especially those pertaining to visual impact. There is no specific national law but only regional laws. The main targets of these laws are the conservation of the environment (protected animals and plants), and the noise generated. The focus of this paper, the visual impact, is not taken into account in a direct way in these laws. This work develops a methodology to predict, before its construction, the visual impact that a wind farm can have. This could be used as a consulting tool to analyse and evaluate wind projects, both government-run and private. The developed methodology is quick, concise and clear.
04•02917 Wave energy transmission system concepts for linear generator arrays Thorburn, K. et al. Ocean Engineering, 2004, 31, (11 12), 1339 1349. Wave energy is a renewable source, which has so far not been exploited widely. Many of the various schemes in the past consist of large mechanical structures, often located near the sea surface. This article presents a range of systems with point absorbers on the surface and linear generators placed on the seabed, converting the wave motion into electrical power. Electrical power components are combined in different ways to obtain solutions suitable for various conditions. Different topologies for the electrical system transmitting power to the grid are discussed. Qualitative case studies are used to exemplify system options and connection schemes.
Others, including development, economics 04/02918 A limited LCA comparing large- and small-scale production of rape methyl ester (RME) under Swedish conditions Bernesson, S. et al. Biomass and Bioenergy, 2004, 26, (6), 545-559. Production of rape methyl ester (RME) can be carried out with different systems solutions, in which the choice of system is usually related to the scale of the production. The purpose of this study was to analyse whether the use of a small-scale R M E production system reduced the environmental load in comparison to a medium- and a large-scale system. To fulfil this purpose, a limited LCA, including airemissions and energy requirements, was carried out for the three plant sizes. For small plants and physical allocation, the global warming potential was 40.3 g CO2-eq/MJfuel, the acidification potential 236 mg SO2-eq/MJfuel, the eutrophication potential 39.1 mg PO4 3--eq/MJ~u~l, the photochemical oxidant creation potential 3.29 mg C2H4-eq/MJfue] and the energy requirement 295 kJ/MJfu~l. It was shown that the differences in environmental impact and energy requirement between small-, medium- and large-scale systems were small or even negligible. The higher oil extraction efficiency and the more efficient use of machinery and buildings in the large-scale system were, to a certain degree, outweighed by the longer transport distances. The dominating production step was the cultivation, in which production of fertilizers, soil emissions and tractive power made major contributions to the
412
Fuel and Energy Abstracts November 2004
environmental load. The results were, however, largely dependent on the method used for allocation of the environmental burden between the R M E and the by-products meal and glycerine. This indicates that when different biofuels or production strategies are to be compared, it is important that the results are calculated with the same allocation strategies and system limitations.
04•02919 A patent for generation of electrolytic hydrogen by a cost effective and cheaper route Viswanath, R. P. International Journal of Hydrogen Energy, 2004, 29, (11), 1191-1194. The electrolysis of water has been studied using polished platinum as electrodes in a divided electrolytic cell. The cell is divided into two compartments using a chemically treated disc separator. The separator allows only the current to pass through and does not permit the ions to move from one compartment to the other. This permits one to apply chemical bias. With this set-up it has been demonstrated that water can be split into hydrogen and oxygen at as low a potential as ~1.0 volt. Based on these studies a patent has been applied.
04/02920 A review on phase change energy storage: materials and applications Farid, M. M. et al. Energy Conversion and Management, 2004, 45, (910), 1597-1615. Latent heat storage is one of the most efficient ways of storing thermal energy. Unlike the sensible heat storage method, the latent heat storage method provides much higher storage density, with a smaller temperature difference between storing and releasing heat. This paper reviews previous work on latent heat storage and provides an insight to recent efforts to develop new classes of phase change materials (PCMs) for use in energy storage. Three aspects have been the focus of this review: PCM materials, encapsulation and applications. There are large numbers of phase change materials that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. Paraffin waxes are cheap and have moderate thermal energy storage density but low thermal conductivity and, hence, require large surface area. Hydrated salts have larger energy storage density and higher thermal conductivity but experience supercooling and phase segregation, and hence, their application requires the use of some nucleating and thickening agents. The main advantages of PCM encapsulation are providing large heat transfer area, reduction of the PCMs reactivity towards the outside environment and controlling the changes in volume of the storage materials as phase change occurs. The different applications in which the phase change method of heat storage can be applied are also reviewed in this paper. The problems associated with the application of PCMs with regards to the material and the methods used to contain them are also discussed.
04/02921 A standard method for specifying the response of hydroelectric plant in frequency-control mode Jones, D. I. et al. Electric Power Systems Research, 2004, 68, (1), 19-32. The paper proposes a specification for the transient and steady-state responses of a hydroelectric power station operating in frequencycontrol mode. It can be used during design, testing and commissioning as well as forming the basis for contractual agreement on performance during normal operation. The specification gives a generic definition of how the electrical power should respond to step, ramp and random changes in frequency. The rationale for the proposed specification is discussed. A prototype transfer function is proposed as an aid to formulating a step response specification. The length of record required during random testing is discussed. The use of the specification is illustrated by considering the response of the Dinorwig pumpedstorage hydroelectric station.
04•02922 Analytical estimates of the energy yield potential from the Alderney Race (Channel Islands) using marine current energy converters Bahaj, A. S. and Myers, L. Renewable Energy, 2004, 29, (12), 19311945. Energy from marine currents offers the promise of regular and predictable electrical generation at higher power densities than other renewables. The marine current resource is potentially large but mainly concentrated in a number of sites around the world. The power density for a horizontal axis turbine operating in such currents has a similar form to that of a wind turbine and is dependent on the cube of the velocity and the fluid density which for water is about 1000 times that of air. These two factors imply that the power density for marine current energy converters will be appreciably higher than that of wind generators resulting in smaller and hence more manageable size turbines. In the UK, for example, tidal races which exist in the waters around the Channel Islands and the 'Sounds' off the Scottish west coast are well known. The energy density at such sites is high due land mass constrictions which result in large current velocities at depths which are suitable for the installation of multiple arrays of turbines. This study was undertaken for the purpose of quantifying the potential of
04/02915 Power regulation in pitch-controlled variablespeed WECS above rated wind speed Bianchi, F. D. et al. Renewable Energy, 2004, 29, (11), 1911-1922. In medium to large scale wind energy conversion systems (WECS), the control of the pitch angle of the blades is an usual method for power regulation above rated wind speed. However, limitations of the pitch actuator have a marked influence on the regulation performance. In variable-speed mode, the control of the generator torque is able to reduce the effects of the pitch actuator limitations. Nevertheless, in this case the system is multiple-input multiple-output (MIMO) and then the control design results more complex. In this situation advance control techniques, such as optimal control, are an interesting option for a systematic controller design. This work analyses variable-pitch power regulation above rated wind speed in the context of optimal control. The analysis is approached from a new point of view in order to establish a clear connection between the choice of the optimization criteria and the compromise between power regulation and pitch actuator limitations.
04/02916 Spanish method of visual impact evaluation in wind farms Hurtado, J. et al. Renewable and Sustainable Energy Reviews, 2004, 8, (5), 483-491. The present Spanish laws on the procedure to evaluate the environmental impact of wind farms are ambiguous, especially those pertaining to visual impact. There is no specific national law but only regional laws. The main targets of these laws are the conservation of the environment (protected animals and plants), and the noise generated. The focus of this paper, the visual impact, is not taken into account in a direct way in these laws. This work develops a methodology to predict, before its construction, the visual impact that a wind farm can have. This could be used as a consulting tool to analyse and evaluate wind projects, both government-run and private. The developed methodology is quick, concise and clear.
04•02917 Wave energy transmission system concepts for linear generator arrays Thorburn, K. et al. Ocean Engineering, 2004, 31, (11 12), 1339 1349. Wave energy is a renewable source, which has so far not been exploited widely. Many of the various schemes in the past consist of large mechanical structures, often located near the sea surface. This article presents a range of systems with point absorbers on the surface and linear generators placed on the seabed, converting the wave motion into electrical power. Electrical power components are combined in different ways to obtain solutions suitable for various conditions. Different topologies for the electrical system transmitting power to the grid are discussed. Qualitative case studies are used to exemplify system options and connection schemes.
Others, including development, economics 04/02918 A limited LCA comparing large- and small-scale production of rape methyl ester (RME) under Swedish conditions Bernesson, S. et al. Biomass and Bioenergy, 2004, 26, (6), 545-559. Production of rape methyl ester (RME) can be carried out with different systems solutions, in which the choice of system is usually related to the scale of the production. The purpose of this study was to analyse whether the use of a small-scale R M E production system reduced the environmental load in comparison to a medium- and a large-scale system. To fulfil this purpose, a limited LCA, including airemissions and energy requirements, was carried out for the three plant sizes. For small plants and physical allocation, the global warming potential was 40.3 g CO2-eq/MJfuel, the acidification potential 236 mg SO2-eq/MJfuel, the eutrophication potential 39.1 mg PO4 3--eq/MJ~u~l, the photochemical oxidant creation potential 3.29 mg C2H4-eq/MJfue] and the energy requirement 295 kJ/MJfu~l. It was shown that the differences in environmental impact and energy requirement between small-, medium- and large-scale systems were small or even negligible. The higher oil extraction efficiency and the more efficient use of machinery and buildings in the large-scale system were, to a certain degree, outweighed by the longer transport distances. The dominating production step was the cultivation, in which production of fertilizers, soil emissions and tractive power made major contributions to the
412
Fuel and Energy Abstracts November 2004
environmental load. The results were, however, largely dependent on the method used for allocation of the environmental burden between the R M E and the by-products meal and glycerine. This indicates that when different biofuels or production strategies are to be compared, it is important that the results are calculated with the same allocation strategies and system limitations.
04•02919 A patent for generation of electrolytic hydrogen by a cost effective and cheaper route Viswanath, R. P. International Journal of Hydrogen Energy, 2004, 29, (11), 1191-1194. The electrolysis of water has been studied using polished platinum as electrodes in a divided electrolytic cell. The cell is divided into two compartments using a chemically treated disc separator. The separator allows only the current to pass through and does not permit the ions to move from one compartment to the other. This permits one to apply chemical bias. With this set-up it has been demonstrated that water can be split into hydrogen and oxygen at as low a potential as ~1.0 volt. Based on these studies a patent has been applied.
04/02920 A review on phase change energy storage: materials and applications Farid, M. M. et al. Energy Conversion and Management, 2004, 45, (910), 1597-1615. Latent heat storage is one of the most efficient ways of storing thermal energy. Unlike the sensible heat storage method, the latent heat storage method provides much higher storage density, with a smaller temperature difference between storing and releasing heat. This paper reviews previous work on latent heat storage and provides an insight to recent efforts to develop new classes of phase change materials (PCMs) for use in energy storage. Three aspects have been the focus of this review: PCM materials, encapsulation and applications. There are large numbers of phase change materials that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. Paraffin waxes are cheap and have moderate thermal energy storage density but low thermal conductivity and, hence, require large surface area. Hydrated salts have larger energy storage density and higher thermal conductivity but experience supercooling and phase segregation, and hence, their application requires the use of some nucleating and thickening agents. The main advantages of PCM encapsulation are providing large heat transfer area, reduction of the PCMs reactivity towards the outside environment and controlling the changes in volume of the storage materials as phase change occurs. The different applications in which the phase change method of heat storage can be applied are also reviewed in this paper. The problems associated with the application of PCMs with regards to the material and the methods used to contain them are also discussed.
04/02921 A standard method for specifying the response of hydroelectric plant in frequency-control mode Jones, D. I. et al. Electric Power Systems Research, 2004, 68, (1), 19-32. The paper proposes a specification for the transient and steady-state responses of a hydroelectric power station operating in frequencycontrol mode. It can be used during design, testing and commissioning as well as forming the basis for contractual agreement on performance during normal operation. The specification gives a generic definition of how the electrical power should respond to step, ramp and random changes in frequency. The rationale for the proposed specification is discussed. A prototype transfer function is proposed as an aid to formulating a step response specification. The length of record required during random testing is discussed. The use of the specification is illustrated by considering the response of the Dinorwig pumpedstorage hydroelectric station.
04•02922 Analytical estimates of the energy yield potential from the Alderney Race (Channel Islands) using marine current energy converters Bahaj, A. S. and Myers, L. Renewable Energy, 2004, 29, (12), 19311945. Energy from marine currents offers the promise of regular and predictable electrical generation at higher power densities than other renewables. The marine current resource is potentially large but mainly concentrated in a number of sites around the world. The power density for a horizontal axis turbine operating in such currents has a similar form to that of a wind turbine and is dependent on the cube of the velocity and the fluid density which for water is about 1000 times that of air. These two factors imply that the power density for marine current energy converters will be appreciably higher than that of wind generators resulting in smaller and hence more manageable size turbines. In the UK, for example, tidal races which exist in the waters around the Channel Islands and the 'Sounds' off the Scottish west coast are well known. The energy density at such sites is high due land mass constrictions which result in large current velocities at depths which are suitable for the installation of multiple arrays of turbines. This study was undertaken for the purpose of quantifying the potential of