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Three cascade solar cells with graded band-gap layer on the base of GaAs-AlGaAs heterosystem
07 Alternative
energy sources (wind energy)
A simple. low-cost solar water heater has been developed for operation in Mediterranean Europe or regions of similar latitude (40-45” north). It takes the form of a trapezoidal-shaped water store in direct contact with an inclined flat-plate solar collector ;~ssemhly. This cross-section induces thermal stratification in the water store. and pi-oxides sufficient energy storage to meet typical daily ho-water demand. Its thermal performance is critically dependent on the w*ater\ide convective hcattransfer coefficient on the backward-reclining collector plate; prcviously evaluated by earlier studies. In the current design, the absorber plate inclination to the horizontal was fixed at 45 (close to the local latitude) in order to yield maximum solar gain over a typical year. The energy saving provided by the solar collector/thermal Store demonstrator largely depends on the amount of thermal stratification within the trapezoidal storage cavity. This was evaluated via both computation and measurements of the temperature field. A thermal network analysis model was then used to assess the energy-saving potential of the composite system. It indicated that a 30-70% reduction in daily load could be obtained in contrast to direct. electrical or gas, heating: the
Wind energy 03101312 Adding wind energy to hydropower BClanger, C. and Gagnon. L. Energy Policy, 2002, 30, (14), 1279-1284. Studies were conducted on wind performance within a mainly hydroelectric system. Because windpower provides only intermittent electricity, the studies aimed at answering the two following questions: First, does windpower development require the installation of additional backup capacity, thereby imposing a hidden cost somewhere in the electricity system? Second, does windpower increase the environmental impacts of the hydro-facilities providing the backup when wind is down? To answer these questions, wind/hydra combinations were simulated using hourly real data (1990-1996) of patterns of electricity demand, wind speeds and hydraulic flows in Quebec. The simulations show that windpower requires backup capacity to compensate for wind fluctuations. In large networks, it may not be necessary to build additional capacity, because reliability could be maintained by other tools, such as buying ancillary services from other generators. However, this also represents a hidden cost of windpower. When hydropower is the option used to compensate for wind fluctuations, a relatively large development of windpower could have significant effects on river flows. It could reduce the minimum flow during dry season and increase the intensity of short-term flow
238
Fuel and Energy Abstracts
July 2003
tluctuations. These conclusions do not mc;,n that umtlpu\~cr dc\clrlpment is not justified. but simply that its assessment should include the impact of backup gcncrati~lli
03101313 Design of wind-driven generator made up of dynamos assembling Valdis, L.-.C. and Darque. J. /
03101314 Hourly wind velocity exceedence maps of Turkey Ahin, A. D. Enrry!, Cor~v~~~sionn& ,~~/f~tr,~ern~c,rl/. 2003. 44. (4). 549 557. Risk analysis is one of the very important topics in engineering applications and scientific researches. In wind engineering, the possible extreme wind velocities constitute the basic targets in risk evaluations. In practice, lower extremes are significant for low energy generation possibilities and for power-cut risks, depending on the turbine type. However. upper extremes endanger the stability of the wind turbines. Additionally, the maxima of wind velocity variations have fundamental importance in engineering structural designs. Besides. from the meteorological point of view, maximum wind velocities directly relate to storms and thunderstorms. In this paper, wind velocity exceedence maps over IO, I?. 15 and 20 m/s are produced for Turkey. and the necessary interpretations are given. These maps show that especially the western part of Turkey and. particularly, coastal areas arc risky locations for structural stability and wind erosion.
03/01315 farms Akhmatov.
Modelling
and transient
stability
of large wind
V. PI al. Ir~trrr~rrionul Jol~r~rcrl of’E/e<~/rir~rrlPower & Energ~~
.yy.awLF, 2003. 75. (2). 123-144.
The paper is dealing with modelling and short-term voltage stability considerations of large wind farms. A physical model of a large offshore wind farm consisting of a large number of windmills is implemented in the dynamic simulation tool PSSIE. Each windmill in the wind farm is represented by a physical model of grid-connected windmills. The windmill generators are conventional induction generators and the wind farm is ac-connected to the power system. Improvements of short-term voltage stability in case of failure events in the external power system are treated with use of conventional generator technology. This subject is treated as a parameter study with respect to the windmill electrical and mechanical parameters and with use of control strategies within the conventional generator technology. Stability improvements on the wind farm side of the connection point lead to significant reduction of dynamic reactive compensation demands. In case of blade angle control applied at failure events, dynamic reactive compensation is not necessary for maintaining the voltage stability.
03/01316 Prospects of wind power plants in Libya: a case study El-Osta, W. and Kalifd, Y. Re!/clu&/r Enrrg.r. 2003. 28, (3). 363-37 I. This paper presents a pre-feasibility study for a proposed demonstration wind farm of about 6 MW in Zwara, 125 km west of Tripoli. This study is based on previous work, which will be modified according to the latest developments in wind energy converter system sizes. It includes an economic evaluation for this project based on different assumptions for the financial parameters. RETSceen software was used for the economic evaluation of this demonstration project. Three different sizes of WECSs (0.6. I and 1.5 MW) were studied as candidate sizes to be proposed for this demonstration wind farm. The pre-feasibility study indicated that the project is economically feasihle for the three cases.
03101317 Wind energy in Adamaoua and North Cameroon provinces Tchinda, R. and Kaptouom, E. Energy Conversion cm/ Mann~mrnt. 2003, 44, (6). 845.-857. From the wind speed data recorded over 9 (1990-1998) and 10 (19901999) years, as observed in the main meteorological stations, called synoptical stations, of the observation network of the National Meteorology Department, located in the Adamaoua and Northern Cameroon provinces, an estimation of the wind energy available has been made for each station. For this use, the wind speed frequencies in the period are considered. Daily, monthly and annual mean wind speeds and wind energy available were determined. The possible applications of this energy for each station are discussed.
energy sources (wind energy)
A simple. low-cost solar water heater has been developed for operation in Mediterranean Europe or regions of similar latitude (40-45” north). It takes the form of a trapezoidal-shaped water store in direct contact with an inclined flat-plate solar collector ;~ssemhly. This cross-section induces thermal stratification in the water store. and pi-oxides sufficient energy storage to meet typical daily ho-water demand. Its thermal performance is critically dependent on the w*ater\ide convective hcattransfer coefficient on the backward-reclining collector plate; prcviously evaluated by earlier studies. In the current design, the absorber plate inclination to the horizontal was fixed at 45 (close to the local latitude) in order to yield maximum solar gain over a typical year. The energy saving provided by the solar collector/thermal Store demonstrator largely depends on the amount of thermal stratification within the trapezoidal storage cavity. This was evaluated via both computation and measurements of the temperature field. A thermal network analysis model was then used to assess the energy-saving potential of the composite system. It indicated that a 30-70% reduction in daily load could be obtained in contrast to direct. electrical or gas, heating: the
Wind energy 03101312 Adding wind energy to hydropower BClanger, C. and Gagnon. L. Energy Policy, 2002, 30, (14), 1279-1284. Studies were conducted on wind performance within a mainly hydroelectric system. Because windpower provides only intermittent electricity, the studies aimed at answering the two following questions: First, does windpower development require the installation of additional backup capacity, thereby imposing a hidden cost somewhere in the electricity system? Second, does windpower increase the environmental impacts of the hydro-facilities providing the backup when wind is down? To answer these questions, wind/hydra combinations were simulated using hourly real data (1990-1996) of patterns of electricity demand, wind speeds and hydraulic flows in Quebec. The simulations show that windpower requires backup capacity to compensate for wind fluctuations. In large networks, it may not be necessary to build additional capacity, because reliability could be maintained by other tools, such as buying ancillary services from other generators. However, this also represents a hidden cost of windpower. When hydropower is the option used to compensate for wind fluctuations, a relatively large development of windpower could have significant effects on river flows. It could reduce the minimum flow during dry season and increase the intensity of short-term flow
238
Fuel and Energy Abstracts
July 2003
tluctuations. These conclusions do not mc;,n that umtlpu\~cr dc\clrlpment is not justified. but simply that its assessment should include the impact of backup gcncrati~lli
03101313 Design of wind-driven generator made up of dynamos assembling Valdis, L.-.C. and Darque. J. /
03101314 Hourly wind velocity exceedence maps of Turkey Ahin, A. D. Enrry!, Cor~v~~~sionn& ,~~/f~tr,~ern~c,rl/. 2003. 44. (4). 549 557. Risk analysis is one of the very important topics in engineering applications and scientific researches. In wind engineering, the possible extreme wind velocities constitute the basic targets in risk evaluations. In practice, lower extremes are significant for low energy generation possibilities and for power-cut risks, depending on the turbine type. However. upper extremes endanger the stability of the wind turbines. Additionally, the maxima of wind velocity variations have fundamental importance in engineering structural designs. Besides. from the meteorological point of view, maximum wind velocities directly relate to storms and thunderstorms. In this paper, wind velocity exceedence maps over IO, I?. 15 and 20 m/s are produced for Turkey. and the necessary interpretations are given. These maps show that especially the western part of Turkey and. particularly, coastal areas arc risky locations for structural stability and wind erosion.
03/01315 farms Akhmatov.
Modelling
and transient
stability
of large wind
V. PI al. Ir~trrr~rrionul Jol~r~rcrl of’E/e<~/rir~rrlPower & Energ~~
.yy.awLF, 2003. 75. (2). 123-144.
The paper is dealing with modelling and short-term voltage stability considerations of large wind farms. A physical model of a large offshore wind farm consisting of a large number of windmills is implemented in the dynamic simulation tool PSSIE. Each windmill in the wind farm is represented by a physical model of grid-connected windmills. The windmill generators are conventional induction generators and the wind farm is ac-connected to the power system. Improvements of short-term voltage stability in case of failure events in the external power system are treated with use of conventional generator technology. This subject is treated as a parameter study with respect to the windmill electrical and mechanical parameters and with use of control strategies within the conventional generator technology. Stability improvements on the wind farm side of the connection point lead to significant reduction of dynamic reactive compensation demands. In case of blade angle control applied at failure events, dynamic reactive compensation is not necessary for maintaining the voltage stability.
03/01316 Prospects of wind power plants in Libya: a case study El-Osta, W. and Kalifd, Y. Re!/clu&/r Enrrg.r. 2003. 28, (3). 363-37 I. This paper presents a pre-feasibility study for a proposed demonstration wind farm of about 6 MW in Zwara, 125 km west of Tripoli. This study is based on previous work, which will be modified according to the latest developments in wind energy converter system sizes. It includes an economic evaluation for this project based on different assumptions for the financial parameters. RETSceen software was used for the economic evaluation of this demonstration project. Three different sizes of WECSs (0.6. I and 1.5 MW) were studied as candidate sizes to be proposed for this demonstration wind farm. The pre-feasibility study indicated that the project is economically feasihle for the three cases.
03101317 Wind energy in Adamaoua and North Cameroon provinces Tchinda, R. and Kaptouom, E. Energy Conversion cm/ Mann~mrnt. 2003, 44, (6). 845.-857. From the wind speed data recorded over 9 (1990-1998) and 10 (19901999) years, as observed in the main meteorological stations, called synoptical stations, of the observation network of the National Meteorology Department, located in the Adamaoua and Northern Cameroon provinces, an estimation of the wind energy available has been made for each station. For this use, the wind speed frequencies in the period are considered. Daily, monthly and annual mean wind speeds and wind energy available were determined. The possible applications of this energy for each station are discussed.