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Ajouter le résultat dans votre panierThermo-economic comparisons of different types of solar desalination processes / Mohamed A. Sharaf in Transactions of the ASME. Journal of solar energy engineering, Vol. 134 N° 3 (Août 2012)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 10 p.
Titre : Thermo-economic comparisons of different types of solar desalination processes Type de document : texte imprimé Auteurs : Mohamed A. Sharaf, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : solar organic cycles; solar desalination technologies; thermo-economic; SDS software package Index. décimale : 621.47 Résumé : Many types of desalination technologies are widely used around the worldwide. Thermal and membrane types dominated the market share among the other technologies (freezing, electrodialysis, and ion-exchange). Currently, multistage flash considered the power house of desalination technologies; however, in the last few decades, multi effect distillation and reverse osmosis (RO) technologies were proven as reliable and cost efficient processes. But comparing and electing the most efficient type between conventional desalination technologies is still under scope. It is very hard to decide which type or technique is reliable and thermo-economically efficient. Also, it becomes harder to decide which type is thermo-economically efficient when desalination process is combined with solar energy. In this work, different types of solar desalination processes are thermo-economically compared and analyzed. Results revel that RO and multi effect distillation-thermal vapor compression are recommended according to specific solar area (SSA m2/(m3/d)), total water price (TWP $/m3), thermo-economic product cost (cp $/GJ), and the gain ratio (GR). The comparisons were performed based on two scenarios: (1) different operating conditions due to each individual technology and (2) uniform operating conditions. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Thermo-economic comparisons of different types of solar desalination processes [texte imprimé] / Mohamed A. Sharaf, Auteur . - 2012 . - 10 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 10 p.
Mots-clés : solar organic cycles; solar desalination technologies; thermo-economic; SDS software package Index. décimale : 621.47 Résumé : Many types of desalination technologies are widely used around the worldwide. Thermal and membrane types dominated the market share among the other technologies (freezing, electrodialysis, and ion-exchange). Currently, multistage flash considered the power house of desalination technologies; however, in the last few decades, multi effect distillation and reverse osmosis (RO) technologies were proven as reliable and cost efficient processes. But comparing and electing the most efficient type between conventional desalination technologies is still under scope. It is very hard to decide which type or technique is reliable and thermo-economically efficient. Also, it becomes harder to decide which type is thermo-economically efficient when desalination process is combined with solar energy. In this work, different types of solar desalination processes are thermo-economically compared and analyzed. Results revel that RO and multi effect distillation-thermal vapor compression are recommended according to specific solar area (SSA m2/(m3/d)), total water price (TWP $/m3), thermo-economic product cost (cp $/GJ), and the gain ratio (GR). The comparisons were performed based on two scenarios: (1) different operating conditions due to each individual technology and (2) uniform operating conditions. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Titre : Next-day daily energy consumption forecast model development and model implementation Type de document : texte imprimé Auteurs : Li Song, Auteur ; Ik-seong Joo, Auteur ; Subroto Gunawan, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : thermal storage systems; cooling consumption; autoregressive model; linear regression model; control algorithm Index. décimale : 621.47 Résumé : Thermal storage systems were originally designed to shift on-peak cooling production to off-peak cooling production in order to reduce on-peak electricity demand. Recently, however, the reduction of both on- and off-peak demand is a critical issue. Reduction of on- and off-peak demand can also extend the life span and defer or eliminate the replacement of power transformers. Next day electricity consumption is a critical set point to operate chillers and associated pumps at the appropriate time. In this paper, a data evaluation process using the annual daily average cooling consumption of a building was conducted. Three real-time building load forecasting models were investigated: a first-order autoregressive model (AR(1)), an autogressive integrated moving average model (ARIMA(0,1,0)), and a linear regression model. A comparison of results shows that the AR(1) and ARIMA(0,1,0) models provide superior results to the linear regression model, except that the AR(1) model has a few unacceptable spikes. A complete control algorithm integrated with a corrected AR(1) forecast model for a chiller plant including chillers, thermal storage system, and pumping systems was developed and implemented to verify the feasibility of applying this algorithm in the building automation system. Application results are also introduced in the paper. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Next-day daily energy consumption forecast model development and model implementation [texte imprimé] / Li Song, Auteur ; Ik-seong Joo, Auteur ; Subroto Gunawan, Auteur . - 2012 . - 08 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Mots-clés : thermal storage systems; cooling consumption; autoregressive model; linear regression model; control algorithm Index. décimale : 621.47 Résumé : Thermal storage systems were originally designed to shift on-peak cooling production to off-peak cooling production in order to reduce on-peak electricity demand. Recently, however, the reduction of both on- and off-peak demand is a critical issue. Reduction of on- and off-peak demand can also extend the life span and defer or eliminate the replacement of power transformers. Next day electricity consumption is a critical set point to operate chillers and associated pumps at the appropriate time. In this paper, a data evaluation process using the annual daily average cooling consumption of a building was conducted. Three real-time building load forecasting models were investigated: a first-order autoregressive model (AR(1)), an autogressive integrated moving average model (ARIMA(0,1,0)), and a linear regression model. A comparison of results shows that the AR(1) and ARIMA(0,1,0) models provide superior results to the linear regression model, except that the AR(1) model has a few unacceptable spikes. A complete control algorithm integrated with a corrected AR(1) forecast model for a chiller plant including chillers, thermal storage system, and pumping systems was developed and implemented to verify the feasibility of applying this algorithm in the building automation system. Application results are also introduced in the paper. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 10 p.
Titre : Effects of terrain slope on nacelle anemometry Type de document : texte imprimé Auteurs : Khaled Ameur, Auteur ; Christian Masson, Auteur Année de publication : 2012 Article en page(s) : 10 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : wind turbine; nacelle anemomerty; escarpment; 3D RANS; atmospheric boundary layer Index. décimale : 621.47 Résumé : A numerical analysis of the effects of sloped terrain on the reading of a nacelle anemometer is investigated. Simulations of the turbulent flow around a 2.5 MW wind turbine in an atmospheric boundary layer are made by resolving 3D RANS equations. In addition to flat terrain, four escarpments (at slopes of 7.5%, 11%, 14%, and 20%) are studied for various inlet velocities in three cases: terrains with no wind turbine, with nonoperating turbines and with operating turbines. The slope of the ground has two major effects on flow: speed-up and an increase in flow inclination. The presence of the nacelle enhances the flow speed-up caused by the escarpment, especially outside the anemometer's position. However, the horizontal velocity at the location of the anemometer tends to decrease with increasing ground slope. This trend is due in large part to the nacelle wake. This disturbed area is characterized by the presence of separated flow and two opposing vortices which are sensitive to the flow inclination. The evaluated nacelle transfer function is influenced by the terrain slope but this sensitivity is reduced by displacing the position of the anemometer upward the nacelle body. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Effects of terrain slope on nacelle anemometry [texte imprimé] / Khaled Ameur, Auteur ; Christian Masson, Auteur . - 2012 . - 10 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 10 p.
Mots-clés : wind turbine; nacelle anemomerty; escarpment; 3D RANS; atmospheric boundary layer Index. décimale : 621.47 Résumé : A numerical analysis of the effects of sloped terrain on the reading of a nacelle anemometer is investigated. Simulations of the turbulent flow around a 2.5 MW wind turbine in an atmospheric boundary layer are made by resolving 3D RANS equations. In addition to flat terrain, four escarpments (at slopes of 7.5%, 11%, 14%, and 20%) are studied for various inlet velocities in three cases: terrains with no wind turbine, with nonoperating turbines and with operating turbines. The slope of the ground has two major effects on flow: speed-up and an increase in flow inclination. The presence of the nacelle enhances the flow speed-up caused by the escarpment, especially outside the anemometer's position. However, the horizontal velocity at the location of the anemometer tends to decrease with increasing ground slope. This trend is due in large part to the nacelle wake. This disturbed area is characterized by the presence of separated flow and two opposing vortices which are sensitive to the flow inclination. The evaluated nacelle transfer function is influenced by the terrain slope but this sensitivity is reduced by displacing the position of the anemometer upward the nacelle body. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 09 p.
Titre : Start-up modeling for annual CSP yield calculations Type de document : texte imprimé Auteurs : Tobias Hirsch, Auteur ; Jan Fabian Feldhoff, Auteur ; Heiko Schenk, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : solar thermal power plant; CSP; start-up; modeling; simulation Index. décimale : 621.47 Résumé : In solar thermal power plants, at least the solar part undergoes a daily start-up process. Since duration and energy consumption of the start-up depend on irradiance and temperature boundary conditions, differences occur between the individual days and especially between the seasons. For a good representation in annual electricity yield calculations, the start-up process should be modeled on a daily basis. This paper presents a closed approach for the calculation of start-up and cool-down in solar thermal power plants especially designed for annual calculations. It is demonstrated by one example how the required parameters can be obtained and how the methodology is applied. A sensitivity analysis reveals the large impact of start-up consumption on the annual yield. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Start-up modeling for annual CSP yield calculations [texte imprimé] / Tobias Hirsch, Auteur ; Jan Fabian Feldhoff, Auteur ; Heiko Schenk, Auteur . - 2012 . - 09 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 09 p.
Mots-clés : solar thermal power plant; CSP; start-up; modeling; simulation Index. décimale : 621.47 Résumé : In solar thermal power plants, at least the solar part undergoes a daily start-up process. Since duration and energy consumption of the start-up depend on irradiance and temperature boundary conditions, differences occur between the individual days and especially between the seasons. For a good representation in annual electricity yield calculations, the start-up process should be modeled on a daily basis. This paper presents a closed approach for the calculation of start-up and cool-down in solar thermal power plants especially designed for annual calculations. It is demonstrated by one example how the required parameters can be obtained and how the methodology is applied. A sensitivity analysis reveals the large impact of start-up consumption on the annual yield. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 09 p.
Titre : Optimal design and operation of a solar energy receiver and storage Type de document : texte imprimé Auteurs : Amin Ghobeity, Auteur ; Alexander Mitsos, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : solar energy receiver; thermal energy storage; thermal analysis Index. décimale : 621.47 Résumé : Optimization of design and operation is presented for a solar energy receiver combined with a thermal energy storage. The concentrated solar power on-demand (CSPonD) concept, which can be described, in brief, as a volumetric solar energy receiver system combined with a modified raft thermocline concept, is considered. The CSPonD concept is assumed to be providing heat for a general cogeneration scheme where power production is the main product of the cogeneration. With a constant power production, a secondary process is assumed to consume the process heat from the CSPonD and power cycle. Models are developed for thermal analysis of the energy storage, taking into account hourly and seasonal variations in the solar energy as well as the heliostat field efficiency. Nonlinear programming (NLP) is used for optimization of the design and operation. The sequential method of optimization and a heuristic approach (parallel computing) are implemented using an equation-oriented modeling environment and gradient-based local solvers. A strategy is presented to design and operate the plant, considering the significant seasonal variations in the solar energy. Three case studies are presented. The first one optimizes the design based on a design day and a desired thermal duty. The other two address optimal yearly operation of the plant. The results of the optimization case studies show that (a) the CSPonD concept aids in handling variations (hourly, daily, and seasonal) in solar energy, (b) CSPonD is a promising concept for cogeneration, (c) the mass of salt required in the CSPonD concept is not significantly lower than the salt required in a single-tank thermal energy storage system. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Optimal design and operation of a solar energy receiver and storage [texte imprimé] / Amin Ghobeity, Auteur ; Alexander Mitsos, Auteur . - 2012 . - 09 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 09 p.
Mots-clés : solar energy receiver; thermal energy storage; thermal analysis Index. décimale : 621.47 Résumé : Optimization of design and operation is presented for a solar energy receiver combined with a thermal energy storage. The concentrated solar power on-demand (CSPonD) concept, which can be described, in brief, as a volumetric solar energy receiver system combined with a modified raft thermocline concept, is considered. The CSPonD concept is assumed to be providing heat for a general cogeneration scheme where power production is the main product of the cogeneration. With a constant power production, a secondary process is assumed to consume the process heat from the CSPonD and power cycle. Models are developed for thermal analysis of the energy storage, taking into account hourly and seasonal variations in the solar energy as well as the heliostat field efficiency. Nonlinear programming (NLP) is used for optimization of the design and operation. The sequential method of optimization and a heuristic approach (parallel computing) are implemented using an equation-oriented modeling environment and gradient-based local solvers. A strategy is presented to design and operate the plant, considering the significant seasonal variations in the solar energy. Three case studies are presented. The first one optimizes the design based on a design day and a desired thermal duty. The other two address optimal yearly operation of the plant. The results of the optimization case studies show that (a) the CSPonD concept aids in handling variations (hourly, daily, and seasonal) in solar energy, (b) CSPonD is a promising concept for cogeneration, (c) the mass of salt required in the CSPonD concept is not significantly lower than the salt required in a single-tank thermal energy storage system. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Titre : Productivity enhancement of solar still using water heater and cooling fan Type de document : texte imprimé Auteurs : Ahmed Z. Al Garni, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : solar still; productivity enhancement; water heater; external cooling fan Index. décimale : 621.47 Résumé : In the present work, an attempt is made to enhance the productivity of a double slope solar still by using an immersion type water heater. The effect of using an external fan to cool the glass surface is also examined. Experiments were carried out for winter season in Saudi Arabian climatic conditions at latitude 26 deg N. A solar still with 35 deg glass slope angle is chosen in our study. Since the yield of a solar still is more for low water depths, the water level in the base tank was maintained at 1 cm. The experimental results showed that the productivity increased by a significant 370% when two water heaters each having 500 W capacities was used. When external cooling fan was used the productivity was found to decrease by 4% and 8% for wind speeds of 7 m/s and 9 m/s, respectively. Thermal modeling was also done using the heat and mass transfer relations, and then, numerical simulations were carried out to validate with the experimental results. A good agreement between experimental and numerical results was found. The present study is partial implementation of two patents submitted in this field. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Productivity enhancement of solar still using water heater and cooling fan [texte imprimé] / Ahmed Z. Al Garni, Auteur . - 2012 . - 08 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Mots-clés : solar still; productivity enhancement; water heater; external cooling fan Index. décimale : 621.47 Résumé : In the present work, an attempt is made to enhance the productivity of a double slope solar still by using an immersion type water heater. The effect of using an external fan to cool the glass surface is also examined. Experiments were carried out for winter season in Saudi Arabian climatic conditions at latitude 26 deg N. A solar still with 35 deg glass slope angle is chosen in our study. Since the yield of a solar still is more for low water depths, the water level in the base tank was maintained at 1 cm. The experimental results showed that the productivity increased by a significant 370% when two water heaters each having 500 W capacities was used. When external cooling fan was used the productivity was found to decrease by 4% and 8% for wind speeds of 7 m/s and 9 m/s, respectively. Thermal modeling was also done using the heat and mass transfer relations, and then, numerical simulations were carried out to validate with the experimental results. A good agreement between experimental and numerical results was found. The present study is partial implementation of two patents submitted in this field. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Titre : Numerical simulation of wind distributions for resource assessment in southeastern Eritrea, east Africa Type de document : texte imprimé Auteurs : B. Lebassi-Habtezion, Auteur ; R. Van Buskirk, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : wind energy resources; simulation; low level jet; stratified marine layer; Eritrea Index. décimale : 621.47 Résumé : We present the results of a simulation study of the wind energy resources of southeastern Eritrea. In this study, we simulate the three dimensional wind fields during typical, steady conditions of the Southern Red Sea southeast monsoon season. The simulations verify the existence of a low level jet (LLJ) contained within the highly stratified marine layer over the Southern Red Sea. The LLJ is caused by the channeling and the acceleration of marine layer flow as it passes through the strait of Bab el Mandeb on its way from the Indian Ocean to the Eastern Sahara. The LLJ extends from 12.5 deg to 14.5 deg N latitude in the Southern Red Sea and has peak velocities at 300–600 m elevation above the sea. Sea-land breezes advect the high speeds of the LLJ onshore along a 200 km stretch of southeastern Eritrean coastline, producing an excellent wind energy resource that peaks daily at 3 p.m. LST. This resource is currently under development for both grid-connected and decentralized village wind energy applications. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Numerical simulation of wind distributions for resource assessment in southeastern Eritrea, east Africa [texte imprimé] / B. Lebassi-Habtezion, Auteur ; R. Van Buskirk, Auteur . - 2012 . - 08 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Mots-clés : wind energy resources; simulation; low level jet; stratified marine layer; Eritrea Index. décimale : 621.47 Résumé : We present the results of a simulation study of the wind energy resources of southeastern Eritrea. In this study, we simulate the three dimensional wind fields during typical, steady conditions of the Southern Red Sea southeast monsoon season. The simulations verify the existence of a low level jet (LLJ) contained within the highly stratified marine layer over the Southern Red Sea. The LLJ is caused by the channeling and the acceleration of marine layer flow as it passes through the strait of Bab el Mandeb on its way from the Indian Ocean to the Eastern Sahara. The LLJ extends from 12.5 deg to 14.5 deg N latitude in the Southern Red Sea and has peak velocities at 300–600 m elevation above the sea. Sea-land breezes advect the high speeds of the LLJ onshore along a 200 km stretch of southeastern Eritrean coastline, producing an excellent wind energy resource that peaks daily at 3 p.m. LST. This resource is currently under development for both grid-connected and decentralized village wind energy applications. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 11 p.
Titre : Novel experimental power curve determination and computational methods for the performance analysis of vertical axis wind turbines Type de document : texte imprimé Auteurs : Jonathan M. Edwards, Auteur ; Louis Angelo Danao, Auteur ; Robert J. Howell, Auteur Année de publication : 2012 Article en page(s) : 11 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : vertical axis wind turbine (VAWT); computational fluid dynamics (CFD); torque measurement; aerodynamics; particle image velocimetry (PIV) Index. décimale : 621.47 Résumé : Through novel experimental and computational methods, this paper details a study into the performance aerodynamics of a small-scale vertical axis wind turbine (VAWT). A novel experimental method is first developed and validated before the results are compared to those of a computational fluid dynamics (CFD) study. The computational study is further validated by comparing the flow field to PIV data. The CFD simulations are then analyzed to explain the aerodynamics in further detail, including a discussion of the effect of the streamwise induction on the local angle of attack on the blade. The University of Sheffield's three-bladed NACA0022 small-scale VAWT experimental rig is mounted within the University's Low-Speed Wind Tunnel. Tests at tip speed ratios up to 5 were carried out, where the blade Reynolds number (based on rotational speed) ranged from 37,500 to 75,000. The same test conditions are simulated using unsteady computational fluid dynamics. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Novel experimental power curve determination and computational methods for the performance analysis of vertical axis wind turbines [texte imprimé] / Jonathan M. Edwards, Auteur ; Louis Angelo Danao, Auteur ; Robert J. Howell, Auteur . - 2012 . - 11 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 11 p.
Mots-clés : vertical axis wind turbine (VAWT); computational fluid dynamics (CFD); torque measurement; aerodynamics; particle image velocimetry (PIV) Index. décimale : 621.47 Résumé : Through novel experimental and computational methods, this paper details a study into the performance aerodynamics of a small-scale vertical axis wind turbine (VAWT). A novel experimental method is first developed and validated before the results are compared to those of a computational fluid dynamics (CFD) study. The computational study is further validated by comparing the flow field to PIV data. The CFD simulations are then analyzed to explain the aerodynamics in further detail, including a discussion of the effect of the streamwise induction on the local angle of attack on the blade. The University of Sheffield's three-bladed NACA0022 small-scale VAWT experimental rig is mounted within the University's Low-Speed Wind Tunnel. Tests at tip speed ratios up to 5 were carried out, where the blade Reynolds number (based on rotational speed) ranged from 37,500 to 75,000. The same test conditions are simulated using unsteady computational fluid dynamics. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 14 p.
Titre : Optical analysis of the fixed mirror solar concentrator by forward ray-tracing procedure Type de document : texte imprimé Auteurs : Ramon Pujol Nadal, Auteur ; Víctor Martínez Moll, Auteur Année de publication : 2012 Article en page(s) : 14 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : FMSC; IAM; ray-tracking; heating process; mobile focus Index. décimale : 621.47 Résumé : The fixed mirror solar concentrator (FMSC) is a mobile focus concentrator whose design emerged in the 1970s in an effort to reduce electricity production costs in solar thermal power plants. This geometry has not yet been analyzed with 3D ray-tracing procedures. The geometry of FMSC is defined using three parameters: the number of mirrors N, the ratio of focal length and reflector width F/W, and the intercept factor gamma (in order to represent different receiver widths). For the analysis, a 3D ray-tracing code that allows the characterization of solar concentrators was developed. A standard evacuated tube was used as a receiver. The geometric concentration ratio, the optical efficiency, and the transversal and longitudinal incidence angle modifier (IAM) curves for different values of design parameters were calculated. High concentrations imply low F/W values and for high efficiencies, large intercept factor values are required. Increasing the F/W ratio has a positive effect on the transversal IAM, yet a negative one for the longitudinal IAM. Increasing the number of mirrors has a negative effect on both IAM curves due to the self-shadowing between the adjacent steps. Increasing the intercept factor only has a significant positive effect on the longitudinal IAM. The goodness of the IAM factorization approach was analyzed, and it was found that it can be used as long as a new correction factor to account for the focus displacement is introduced. The results presented in this paper provide information, in form of curves, regarding the optical behavior of the FMSC in terms of different design parameters in order to know the possibility to use the FMSC in medium range temperature applications. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Optical analysis of the fixed mirror solar concentrator by forward ray-tracing procedure [texte imprimé] / Ramon Pujol Nadal, Auteur ; Víctor Martínez Moll, Auteur . - 2012 . - 14 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 14 p.
Mots-clés : FMSC; IAM; ray-tracking; heating process; mobile focus Index. décimale : 621.47 Résumé : The fixed mirror solar concentrator (FMSC) is a mobile focus concentrator whose design emerged in the 1970s in an effort to reduce electricity production costs in solar thermal power plants. This geometry has not yet been analyzed with 3D ray-tracing procedures. The geometry of FMSC is defined using three parameters: the number of mirrors N, the ratio of focal length and reflector width F/W, and the intercept factor gamma (in order to represent different receiver widths). For the analysis, a 3D ray-tracing code that allows the characterization of solar concentrators was developed. A standard evacuated tube was used as a receiver. The geometric concentration ratio, the optical efficiency, and the transversal and longitudinal incidence angle modifier (IAM) curves for different values of design parameters were calculated. High concentrations imply low F/W values and for high efficiencies, large intercept factor values are required. Increasing the F/W ratio has a positive effect on the transversal IAM, yet a negative one for the longitudinal IAM. Increasing the number of mirrors has a negative effect on both IAM curves due to the self-shadowing between the adjacent steps. Increasing the intercept factor only has a significant positive effect on the longitudinal IAM. The goodness of the IAM factorization approach was analyzed, and it was found that it can be used as long as a new correction factor to account for the focus displacement is introduced. The results presented in this paper provide information, in form of curves, regarding the optical behavior of the FMSC in terms of different design parameters in order to know the possibility to use the FMSC in medium range temperature applications. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 13 p.
Titre : Experimental study to characterize the performance of combined photovoltaic/thermal air collectors Type de document : texte imprimé Auteurs : Véronique Delisle, Auteur ; Michaël Kummert, Auteur Année de publication : 2012 Article en page(s) : 13 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : characterization; equivalent cell temperature; performance; PV/T collector; testing Index. décimale : 621.47 Résumé : Combined photovoltaic/thermal (PV/T) collectors show great potential for reaching the objective of net-zero energy consumption in buildings, but the number of products on the market is still very limited. One of the reasons for the slow market uptake of PV/T collectors is the absence of standardized methods to characterize their performance. Performance characterization is a challenge for PV/T collectors because of the interaction between the thermal and electrical yield. This study addresses this particular issue for PV/T air collectors used in either closed-loop or open-loop configurations. In particular, it presents the potential of the equivalent cell temperature method to determine the temperature of the PV cells in a PV/T air collector and validates models to predict the thermal performance and cell temperature for this particular type of solar collector. Indoor and outdoor experimental tests were performed on two c-Si unglazed PV/T modules. The indoor part of this procedure provided the thermal diode voltage factor and the open-circuit voltage temperature coefficient, two parameters that are essential in the calculation of the equivalent cell temperature. The outdoor procedure consisted of acquiring simultaneous electrical and thermal measurements at various inlet temperatures and flowrates. For the collector used in a closed-loop configuration, thermal efficiency models using the fluid inlet, outlet, or average temperature in the calculation of the reduced temperature provided similar results. For an open-loop configuration, a thermal efficiency model as a function of the fluid outlet flowrate was found to be more appropriate. Using selection of variable methods, it was found that a multiple linear regression model using the fluid inlet temperature, the irradiance, and the fluid outlet temperature as predictive variables could be used to estimate both the PV module back surface average temperature and the equivalent cell temperature. When using the PV temperature predicted by these models in the electrical efficiency model, both PV temperatures showed similar performance. In collectors where the PV back surface temperature is not accessible for temperature sensors mounting, the equivalent cell temperature provides a valuable alternative to be used as the PV temperature. The PV/T collector thermal and electrical performance in either closed-loop or open-loop configurations was found to be encapsulated with a series of five-plots. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Experimental study to characterize the performance of combined photovoltaic/thermal air collectors [texte imprimé] / Véronique Delisle, Auteur ; Michaël Kummert, Auteur . - 2012 . - 13 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 13 p.
Mots-clés : characterization; equivalent cell temperature; performance; PV/T collector; testing Index. décimale : 621.47 Résumé : Combined photovoltaic/thermal (PV/T) collectors show great potential for reaching the objective of net-zero energy consumption in buildings, but the number of products on the market is still very limited. One of the reasons for the slow market uptake of PV/T collectors is the absence of standardized methods to characterize their performance. Performance characterization is a challenge for PV/T collectors because of the interaction between the thermal and electrical yield. This study addresses this particular issue for PV/T air collectors used in either closed-loop or open-loop configurations. In particular, it presents the potential of the equivalent cell temperature method to determine the temperature of the PV cells in a PV/T air collector and validates models to predict the thermal performance and cell temperature for this particular type of solar collector. Indoor and outdoor experimental tests were performed on two c-Si unglazed PV/T modules. The indoor part of this procedure provided the thermal diode voltage factor and the open-circuit voltage temperature coefficient, two parameters that are essential in the calculation of the equivalent cell temperature. The outdoor procedure consisted of acquiring simultaneous electrical and thermal measurements at various inlet temperatures and flowrates. For the collector used in a closed-loop configuration, thermal efficiency models using the fluid inlet, outlet, or average temperature in the calculation of the reduced temperature provided similar results. For an open-loop configuration, a thermal efficiency model as a function of the fluid outlet flowrate was found to be more appropriate. Using selection of variable methods, it was found that a multiple linear regression model using the fluid inlet temperature, the irradiance, and the fluid outlet temperature as predictive variables could be used to estimate both the PV module back surface average temperature and the equivalent cell temperature. When using the PV temperature predicted by these models in the electrical efficiency model, both PV temperatures showed similar performance. In collectors where the PV back surface temperature is not accessible for temperature sensors mounting, the equivalent cell temperature provides a valuable alternative to be used as the PV temperature. The PV/T collector thermal and electrical performance in either closed-loop or open-loop configurations was found to be encapsulated with a series of five-plots. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 06 p.
Titre : Comparative study in predicting the global solar radiation for Darwin, Australia Type de document : texte imprimé Auteurs : Wai Kean Yap, Auteur ; Vishy Karri, Auteur Année de publication : 2012 Article en page(s) : 06 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : solar radiation prediction; linear regression analysis; angstrom-prescott-page; artificial neural network Index. décimale : 621.47 Résumé : This paper presents a comparative study in predicting the monthly average solar radiation for Darwin, Australia (latitude 12.46 deg S longitude 130.84 deg E). The city of Darwin, Northern Territory (NT), has the highest and most consistent sunshine duration among all the other Australian states. This unique climate presents an opportunity for photovoltaic (PV) applications. Reliable and accurate predictions of solar radiation enable potential site locations, which exhibit high solar radiations and sunshine hours, to be identified for PV installation. Three predictive models were investigated in this study—the linear regression (LR), Angstrom–Prescott–Page (APP), and the artificial neural network (ANN) models. The mean global solar radiation coupled with the climate data (mean minimum and maximum temperatures, mean rainfall, mean evaporation, and sunshine fraction) obtained from the Australian Bureau of Meteorology (BoM) formed the basis of the dataset. Using simple and easily obtainable climate data presents an added advantage by reducing model complexity. Predictive results showed the root mean square errors (RMSEs) obtained were 6.72%, 13.29%, and 8.11% for the LR, APP, and ANN models, respectively. The predicted solar exposure from the LR model was then compared with the satellite-derived data to assess the accuracy of the LR method. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Comparative study in predicting the global solar radiation for Darwin, Australia [texte imprimé] / Wai Kean Yap, Auteur ; Vishy Karri, Auteur . - 2012 . - 06 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 06 p.
Mots-clés : solar radiation prediction; linear regression analysis; angstrom-prescott-page; artificial neural network Index. décimale : 621.47 Résumé : This paper presents a comparative study in predicting the monthly average solar radiation for Darwin, Australia (latitude 12.46 deg S longitude 130.84 deg E). The city of Darwin, Northern Territory (NT), has the highest and most consistent sunshine duration among all the other Australian states. This unique climate presents an opportunity for photovoltaic (PV) applications. Reliable and accurate predictions of solar radiation enable potential site locations, which exhibit high solar radiations and sunshine hours, to be identified for PV installation. Three predictive models were investigated in this study—the linear regression (LR), Angstrom–Prescott–Page (APP), and the artificial neural network (ANN) models. The mean global solar radiation coupled with the climate data (mean minimum and maximum temperatures, mean rainfall, mean evaporation, and sunshine fraction) obtained from the Australian Bureau of Meteorology (BoM) formed the basis of the dataset. Using simple and easily obtainable climate data presents an added advantage by reducing model complexity. Predictive results showed the root mean square errors (RMSEs) obtained were 6.72%, 13.29%, and 8.11% for the LR, APP, and ANN models, respectively. The predicted solar exposure from the LR model was then compared with the satellite-derived data to assess the accuracy of the LR method. DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Titre : Online monitoring system for stand-alone photovoltaic applications : analysis of system performance from monitored data Type de document : texte imprimé Auteurs : M. Torres, Auteur ; F. J. Muñoz, Auteur ; J. V. Munoz, Auteur Année de publication : 2012 Article en page(s) : 08 p. Note générale : solar energy Langues : Anglais (eng) Mots-clés : SAPV systems; performance analysis; monitoring; LABVIEW; internet Index. décimale : 621.47 Résumé : The Guidelines for the Assessment of Photovoltaic Plants provided by the Joint Research Centre (JRC) and the International Standard IEC 61724 recommend procedures for the analysis of monitored data to asses the overall performance of photovoltaic (PV) systems. However, the latter do not provide a well adapted method for the analysis of stand-alone photovoltaic systems (SAPV) with charge regulators without maximum power point tracker (MPPT). In this way, the IDEA Research Group has developed a new method that improves the analysis performance of these kinds of systems. Moreover, it has been validated an expression that compromises simplicity and accuracy when estimating the array potential in this kind of systems. SAPV system monitoring and performance analysis from monitored data are of great interest to engineers both for detecting a system malfunction and for optimizing the design of future SAPV system. In this way, this paper introduces an online monitoring system in real time for SAPV applications where the monitored data are processed in order to provide an analysis of system performance. The latter, together with the monitored data, are displayed on a graphical user interface using a virtual instrument (VI) developed in LABVIEW®. Furthermore, the collected and monitored data can be shown in a website where an external user can see the daily evolution of all monitored and derived parameters. At present, three different SAPV systems, installed in the Polytechnic School of University of Jaén, are being monitorized and the collected data are being published online in real time. Moreover, a performance analysis of these stand-alone photovoltaic systems considering both IEC 61724 and the IDEA Method is also offered. These three systems use the charge regulators more widespread in the market. Systems #1 and #2 use pulse width modulation (PWM) charge regulators, (a series and a shunt regulator, respectively), meanwhile System #3 has a charge regulator with MPPT. This website provides a tool that can be used not only for educational purposes in order to illustrate the operation of this kind of systems but it can also show the scientific and engineering community the main features of the system performance analysis methods mentioned above. Furthermore, it allows an external user to download the monitored and analysis data to make its own offline analysis. These files comply with the format proposed in the standard IEC 61724. The SAPV system monitoring website is now available for public viewing on the University of Jaén. (http://voltio.ujaen.es/sfa/index.html). DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...] [article] Online monitoring system for stand-alone photovoltaic applications : analysis of system performance from monitored data [texte imprimé] / M. Torres, Auteur ; F. J. Muñoz, Auteur ; J. V. Munoz, Auteur . - 2012 . - 08 p.
solar energy
Langues : Anglais (eng)
in Transactions of the ASME. Journal of solar energy engineering > Vol. 134 N° 3 (Août 2012) . - 08 p.
Mots-clés : SAPV systems; performance analysis; monitoring; LABVIEW; internet Index. décimale : 621.47 Résumé : The Guidelines for the Assessment of Photovoltaic Plants provided by the Joint Research Centre (JRC) and the International Standard IEC 61724 recommend procedures for the analysis of monitored data to asses the overall performance of photovoltaic (PV) systems. However, the latter do not provide a well adapted method for the analysis of stand-alone photovoltaic systems (SAPV) with charge regulators without maximum power point tracker (MPPT). In this way, the IDEA Research Group has developed a new method that improves the analysis performance of these kinds of systems. Moreover, it has been validated an expression that compromises simplicity and accuracy when estimating the array potential in this kind of systems. SAPV system monitoring and performance analysis from monitored data are of great interest to engineers both for detecting a system malfunction and for optimizing the design of future SAPV system. In this way, this paper introduces an online monitoring system in real time for SAPV applications where the monitored data are processed in order to provide an analysis of system performance. The latter, together with the monitored data, are displayed on a graphical user interface using a virtual instrument (VI) developed in LABVIEW®. Furthermore, the collected and monitored data can be shown in a website where an external user can see the daily evolution of all monitored and derived parameters. At present, three different SAPV systems, installed in the Polytechnic School of University of Jaén, are being monitorized and the collected data are being published online in real time. Moreover, a performance analysis of these stand-alone photovoltaic systems considering both IEC 61724 and the IDEA Method is also offered. These three systems use the charge regulators more widespread in the market. Systems #1 and #2 use pulse width modulation (PWM) charge regulators, (a series and a shunt regulator, respectively), meanwhile System #3 has a charge regulator with MPPT. This website provides a tool that can be used not only for educational purposes in order to illustrate the operation of this kind of systems but it can also show the scientific and engineering community the main features of the system performance analysis methods mentioned above. Furthermore, it allows an external user to download the monitored and analysis data to make its own offline analysis. These files comply with the format proposed in the standard IEC 61724. The SAPV system monitoring website is now available for public viewing on the University of Jaén. (http://voltio.ujaen.es/sfa/index.html). DEWEY : 621.47 ISSN : 0199-6231 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000134000003 [...]
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