The top heat losses that constitute the major losses from the box type solar cooker have a strong influence on the thermal performance. To predict or evaluate the thermal performance of a cooker, the top heat loss coefficient U,w for a water loaded cooker must be known. In the present study, several indoor and outdoor experiments were performed on a solar cooker to develop a correlation for the variable Utw as a function of pot water temperature, wind speed and ambient air temperature. The proposed correlation for Utw is employed to obtain heating characteristic curves or predict the thermal behaviour of the cooker for different quantities of water, solar radiation levels and wind speeds. The investigations reveal that the pot water requires less time to reach a certain temperature with an increase in solar radiation level, while it takes a longer time with higher values of load of water in the pots, as expected. However, the effect of wind speed on the time required for certain rise in pot water temperature is marginal.

04/01428 Use of artificial neural networks for mapping of solar potential in Turkey S6zen, A. et al. Applied Energy, 2004, 77, (3), 273-286. Turkey has sufficient solar radiation intensities and radiation durations for solar thermal applications since Turkey lies in a sunny belt, between 36 ° and 42°N latitudes. The yearly average solar-radiation is 3.6 kWh/ m 2 day, and the total yearly radiation period is ~2610 h. The main focus of this study is to determine the solar-energy potential in Turkey using artificial neural-networks (ANNs). Scaled conjugate gradient (SCG), Pola-Ribiere conjugate gradient (CGP), and Levenberg- Marquardt (LM) learning algorithms and a logistic sigmoid transfer function were used in the network. In order to train the neural network, meteorological data for the last 3 years (2000-2002) from 17 stations (namely cities) spread over Turkey were used as training (11 stations) and testing (six stations) data. Meteorological and geographi- cal data (latitude, longitude, altitude, month, mean sunshine duration, and mean temperature) are used as inputs to the network. Solar radiation is in the output layer. The maximum mean absolute percentage error was found to be less than 6.7% and R2values to be about 99.8937% for the testing stations. However, the respective values were found to be 2.41 and 99.99658% for the training stations. The trained and tested ANN models show greater accuracies for evaluating solar resource possibilities in regions where a network of monitoring stations has not been established in Turkey. The predicted solar- potential values from the ANN were given in the form of monthly maps. These maps are of prime importance for different working disciplines, like those of scientists, architects, meteorologists, and solar engineers in Turkey. The predictions from ANN models could enable scientists to locate and design solar-energy systems in Turkey and determine the appropriate solar technology.

Wind energy

04•01429 A phenomenological model for the dynamic response of wind turbines to turbulent wind Rauh, A. and Peinke, J. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (2), 159-183. To predict the average power output of a wind turbine, a response model is proposed which takes into account: (i) the delayed response to the longitudinal wind speed fluctuations; (ii) a response function of the turbine with arbitrary frequency dependence; (iii) wind fields of arbitrary turbulence intensity. In the limit of low turbulence intensity, the dynamical ansatz as proposed in 1992 by Rosen and Sheinman is reproduced. It is shown, how the response function of the turbine can be obtained from simulation experiments of a specific wind turbine. For two idealized situations the dynamic effect of fluctuating wind is estimated at turbulence intensities 0 _< I, _< 0.5. At the special mean wind speed V = 8 m/s, the turbine response function is determined from simulation data published by Sheinman and Rosen in 1992 and 1994.

04/01430 An investigation of flow fields around flanged diffusers using CFD Abe, K.-I. and Ohya, Y. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (3-4), 315-330. Numerical investigations are carried out for flow fields around flanged diffusers to develop small-type wind turbines under 1.5 kW. In the calculations, an advanced closure approximation is adopted, within the framework of non-linear eddy-viscosity modelling, which aims specifi- cally at an improved representation of turbulence anisotropy. Com- parison of the computed results with the corresponding experimental data shows that the present calculation has the capability of providing reasonable predictions for the present complex turbulent flows. Furthermore, by processing the computational results, the input-power coefficient is estimated under various conditions of diffuser opening

07 Altemative energy sources (wind energy)

angle and loading coefficient. It is shown that the performance of a flanged diffuser strongly depends on the loading coefficient as well as the opening angle because it greatly affects the nature of the separation appearing inside the diffuser. The present investigation suggests that the loading coefficient for the best performance of a flanged diffuser is considerably smaller than that for a bare wind turbine.

04/01431 Assessment of wind-generation potentiality in Jordan using the site effectiveness approach Ammari, H. D. and AI-Maaitah, A. Energy, 2003, 28, (15), 1579-1592. Wind data gathered over 3-10 years is used for a feasibility analysis of optimum future utilization of wind-generator potentiality in 22 sites covering all landscape types and regions in Jordan. The yearly mean wind speed and the yearly average available wind energy flux were computed for each site. Yearly mean wind speeds at a height of 24 m could reach as high as 7.6 m/s and available wind energy flux close to 3 MWh/mZ/year could be attained. Detailed technical assessment for the nine most promising potential wind sites was made using the site effectiveness approach. The maximum site effectiveness and its corresponding cut-in speed were indicated, both of which depended on the site. The investigation was performed assuming three models of small and medium size wind machines representing different ranges of characteristic speeds and rated power suitable for water pumping and electric supply. The results show that small and medium wind turbines could be installed in the highlands and desert regions and utilized for water supply and electrical power generation, provided the correct wind machine-site is selected.

04•01432 Confidence limits for extreme wind speeds in mixed climates Cook, N. J. Journal of Wind Engineering and Industrial Aerodynamics, 2004, 92, (1), 41-51. A recent paper updated the methodology for the analysis of extreme wind speeds in mixed climates originally proposed in 1978 by Gomes and Vickery (GV) to take advantage of recent improvements in methodology and available data records. This involved the separation of independent sub-annual maxima by storm mechanism, determining the Weibull shape parameter k, preconditioning for fastest convergence using k, fitting each mechanism to the Fisher-Tippet Type I distribution and synthesizing the composite extreme-value distribution. That work did not address the confidence of the composite distribution. In this paper, the 'bootstrap' method was used to derive the confidence limits of the composite distribution for the revised methodology, as well as for the original GV methodology, illustrated by data from Onslow and Brisbane in Australia. It is shown that the composite distribution can be directly fitted to the observations, without prior separation by storm mechanism, when each mechanism is adequately represented in the observations. However, separation by causal mechanism prior to analysis should always be the preferred option when suitable data records are available.

04•01433 Experimental investigation on the dynamic response of a moored wave energy device under regular sea waves Rapaka, E. V. et al. Ocean Engineering, 2004, 31, (5-6), 725-743. This paper attempts to provide a better understanding of the hydrodynamic behaviour of a floating multi-resonant oscillating column wave energy device which combines the concept of a floating breakwater and a wave energy device. Experiments were conducted on a 1:20 scale model of the floating wave energy device moored by six mooring lines to study the dynamics of the device under regular waves for various scopes. The effect of non-dimensionalized wave frequency parameter on the motion response and mooring force are reported and discussed in detail in this paper.

04•01434 Parametric investigation concerning dimensions of a stand-alone wind-power system Kaldellis, J. K. Applied Energy, 2004, 77, (1), 35-50. A detailed parametric analysis is carried out concerning the optimum sizing of a stand-alone wind-power system, used to ensure the electricity supply of several remote consumers. This study initially analyses the impact of the available wind-potential quality on the dimensions of the main system's components. Accordingly, the influence of the specific wind-power curve - utilized on the proposed configuration sizing - is also examined. In addition, the system's minimum acceptable reliability contribution is investigated for deter- mining the minimum cost stand-alone system dimensions. Finally, the consumer size effect is taken into consideration during the best choice selection process. Thus, by incorporating the proposed parametric analysis results in an appropriate decision-taking procedure, a significant reduction of the system dimensions may be realized, leading to a remarkably diminished first installation cost.

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