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  • Past, present, future of solar cooling: Technical and economical considerations
    Sol. Energy (IF 4.018) Pub Date : 2018-01-08
    R.M. Lazzarin, M. Noro

    A large fraction of cooling demand depends on solar radiation intensity, therefore a strong attention was directed toward solar cooling immediately after the 1973 energy crisis. Whereas pilot solar cooling plants were built up and experimented, this technology never really took off. A recent survey reported something more than 1000 plants operating, a very modest number with respect the great potential of solar cooling. A review of technologies as they developed in the past, operate in the present with a forecasting for the future is here proposed to follow how the technology evolved during almost half a century regarding the solar section and the relative refrigeration equipment. The analysis allows to take stock of the situation selecting solar sections, cooling machines and their coupling which seem nowadays more suitable for wide application in the near future.A study is proposed at the end to put together some energy evaluations in different climates and much more difficult economical evaluations to investigate whether a possible fossil fuel parity cost can be attained, if not today, in a near future.

    更新日期:2018-01-08
  • Production of polycrystalline silicon from silane pyrolysis: A review of fines formation
    Sol. Energy (IF 4.018) Pub Date : 2017-12-26
    Pan Zhang, Jihai Duan, Guanghui Chen, Jianlong Li, Weiwen Wang

    Silane is a major silicon source gas for production of polycrystalline silicon. Production of polysilicon from silane has several benefits: lower energy consumption, much easily obtaining electronical polysilicon and less impact on the environment. There is, however, a major challenge that silane homogenous decomposition may result in amorphous silicon powders (fines) formation. In this review we focus on the fines formation with silane as feed gas. Firstly, this paper reports the situation of the production of silane source gas, the mechanism of the silane decomposition and fines formation. The reactor design, operation parameters and carrier gas, all of these would affect fines formation. This study also reviews on emerging trends in these aspects in outcome studies.

    更新日期:2017-12-27
  • Short-term solar irradiance forecasting via satellite/model coupling
    Sol. Energy (IF 4.018) Pub Date : 2017-12-01
    Steven D. Miller, Matthew A. Rogers, John M. Haynes, Manajit Sengupta, Andrew K. Heidinger

    The short-term (0–3 h) prediction of solar insolation for renewable energy production is a problem well-suited to satellite-based techniques. The spatial, spectral, temporal and radiometric resolution of instrumentation hosted on the geostationary platform allows these satellites to describe the current cloud spatial distribution and optical properties. These properties relate directly to the transient properties of the downwelling solar irradiance at the surface, which come in the form of ‘ramps’ that pose a central challenge to energy load balancing in a spatially distributed network of solar farms. The short-term evolution of the cloud field may be approximated to first order simply as translational, but care must be taken in how the advection is handled and where the impacts are assigned. In this research, we describe how geostationary satellite observations are used with operational cloud masking and retrieval algorithms, wind field data from Numerical Weather Prediction (NWP), and radiative transfer calculations to produce short-term forecasts of solar insolation for applications in solar power generation. The scheme utilizes retrieved cloud properties to group pixels into contiguous cloud objects whose future positions are predicted using four-dimensional (space + time) model wind fields, selecting steering levels corresponding to the cloud height properties of each cloud group. The shadows associated with these clouds are adjusted for sensor viewing parallax displacement and combined with solar geometry and terrain height to determine the actual location of cloud shadows. For mid/high-level clouds at mid-latitudes and high solar zenith angles, the combined displacements from these geometric considerations are non-negligible. The cloud information is used to initialize a radiative transfer model that computes the direct and diffuse-sky solar insolation at both shadow locations and intervening clear-sky regions. Here, we describe the formulation of the algorithm and validate its performance against Surface Radiation (SURFRAD; Augustine et al., 2000, 2005) network observations. Typical errors range from 8.5% to 17.2% depending on the complexity of cloud regimes, and an operational demonstration outperformed persistence-based forecasting of Global Horizontal Irradiance (GHI) under all conditions by ∼10 W/m2.

    更新日期:2017-12-14
  • Improved satellite-derived PV power nowcasting using real-time power data from reference PV systems
    Sol. Energy (IF 4.018) Pub Date : 2017-11-22
    Jamie M. Bright, Sven Killinger, David Lingfors, Nicholas A. Engerer

    Rapid growth in the global penetration of solar photovoltaic (PV) systems means electricity network operators and electricity generators alike are increasingly concerned with the short-term solar forecasting (nowcasting) of solar irradiance. This paper proposes a methodology that considers a varying number of available reference PV systems for supporting satellite-derived PV power real-time nowcasting. We evaluate conventional satellite-only and upscaling-only PV fleet estimate methodologies and compare them to two newly developed correction and hybrid cases. When using only a single reference PV system to estimate the aggregated power of 48 independent target PV systems for the location of Canberra, Australia; we show that the newly proposed correction or hybrid cases improve the performance of the satellite-derived PV power estimate medians in terms of MBE, rMBE, RMSE and rRMSE from 0.031  W / W p , 7.46 % , 0.079  W / W p and 23.4 % , down to 0.006  W / W p , - 0.711 % , 0.068  W / W p and 20.0 % , representing relative improvements of 80.6%, 90.5%, 13.9% and 14.5%, respectively. Similarly, when using 30 reference PV systems, we report median improvements from 0.036  W / W p , 8.25 % , 0.083  W / W p and 24.8 % , down to 0.01  W / W p , 1.41 % , 0.049  W / W p and 11.4 % , representing relative improvements of 72.2%, 82.9%, 41.0% and 54.0%, respectively. We discuss the fundamental challenges facing the use of reference PV systems, satellite-derived power estimates, combining the two data sources, and the knowledge required to address these issues. We ultimately conclude that combining satellite-based PV power estimates with data from reference PV systems is always more beneficial than either on their own.

    更新日期:2017-12-14
  • Application of a single wire-mesh sensor in a parabolic trough facility with direct steam generation
    Sol. Energy (IF 4.018) Pub Date : 2017-10-03
    A. Hoffmann, E. Schleicher, L. Keller, J. León Alonso, R. Pitz-Paal

    The direct steam generation process can contribute to increase the cost-effectiveness of line-focused solar thermal power plants. The current research focuses on the once-through mode as very promising option for large-scale commercial plants. However, the existing pool of knowledge about the steam–water flow in the horizontal receiver pipes reveals knowledge gaps. The present contribution aims to experimentally investigate the two-phase flow in the receiver pipes of the DISS test facility at the Plataforma Solar de Almería, Spain, by an invasive measurement device for the first time. Therefore, a conductance wire-mesh sensor is employed in the low-quality evaporation section of the DISS test facility. This measurement device measures the local instantaneous void fraction that is used to describe the prevailing flow pattern under different pressures and mass flow rates. The results show slug flow, roll waves, wavy flow, and stratified-wavy flow in the horizontal receiver pipes within pressures of 30–80 bar. The probability of slug flow or large-amplitude waves decreases with higher pressures. The findings provide a valuable knowledge about the flow structure within the receiver pipes and confirm the proof of function of the wire-mesh sensor under conditions of the direct steam generation process.

    更新日期:2017-12-14
  • Analyzing wind cleaning process on the accumulated dust on solar photovoltaic (PV) modules on flat surfaces
    Sol. Energy (IF 4.018) Pub Date : 2017-09-30
    Yu Jiang, Lin Lu, Andrea R. Ferro, Goodarz Ahmadi

    In this study, the particle resuspension theory was used to estimate the wind cleaning process of the dust particles deposited on flat solar photovoltaic (PV) module surfaces. The model includes the effects of adhesion force, as well as, the hydrodynamic force and torque for rolling detachment model in the analysis. The required shear velocity and actual wind velocity for resuspension of particles with diameter ranging from 0.1 to 100 µm were evaluated, varied from 0.23 to 57.56 m/s and 0.82 to 2219.8 m/s, respectively. The effect of particle size and composition on the required removal velocity was also analyzed. Verified with the experimental deposited dust size distribution, large particles with diameter larger than 1 µm were effectively removed by wind. However, wind cleaning process for small particles was found not to be effective due to the large required shear velocity for detachment. In addition to particle sizes, the influence of compositions on the wind cleaning process can be negligible.

    更新日期:2017-12-14
  • Optimization of the Sudoku based reconfiguration technique for PV arrays power enhancement under mutual shading conditions
    Sol. Energy (IF 4.018) Pub Date : 2017-06-08
    Majid Horoufiany, Reza Ghandehari

    The low relative position of the fixed PV arrays can lead to the mutual shading between them. This shading decreases the overall energy produced by PV systems due to the mismatch losses. In this paper, the fixed reconfiguration technique is optimized bases on Sudoku puzzle pattern to reduce the effects of this shading. In the optimized technique, the physical location of modules in a total cross tied (TCT) connected PV array are rearranged based on new modified Sudoku dispersion rules. For this purpose, the mutual shadow (MSH) pattern is initially determined in the PV plants that have collectors with the same tilt and direction. Then, the weaknesses of the usual Sudoku dispersion rules against these shadows are explained and the MSHs that can lead to the non-optimal conditions are presented. For optimization of the Sudoku-based reconfiguration technique, the new rules will be merged to the usual Sudoku dispersion rules. Finally, the improvement resulting from the modified technique with respect to the non-modified and some other methods is demonstrated by extensive simulation results.

    更新日期:2017-12-14
  • Short-term solar irradiance forecasting via satellite/model coupling
    Sol. Energy (IF 4.018) Pub Date : 2017-12-01
    Steven D. Miller, Matthew A. Rogers, John M. Haynes, Manajit Sengupta, Andrew K. Heidinger

    The short-term (0–3 h) prediction of solar insolation for renewable energy production is a problem well-suited to satellite-based techniques. The spatial, spectral, temporal and radiometric resolution of instrumentation hosted on the geostationary platform allows these satellites to describe the current cloud spatial distribution and optical properties. These properties relate directly to the transient properties of the downwelling solar irradiance at the surface, which come in the form of ‘ramps’ that pose a central challenge to energy load balancing in a spatially distributed network of solar farms. The short-term evolution of the cloud field may be approximated to first order simply as translational, but care must be taken in how the advection is handled and where the impacts are assigned. In this research, we describe how geostationary satellite observations are used with operational cloud masking and retrieval algorithms, wind field data from Numerical Weather Prediction (NWP), and radiative transfer calculations to produce short-term forecasts of solar insolation for applications in solar power generation. The scheme utilizes retrieved cloud properties to group pixels into contiguous cloud objects whose future positions are predicted using four-dimensional (space + time) model wind fields, selecting steering levels corresponding to the cloud height properties of each cloud group. The shadows associated with these clouds are adjusted for sensor viewing parallax displacement and combined with solar geometry and terrain height to determine the actual location of cloud shadows. For mid/high-level clouds at mid-latitudes and high solar zenith angles, the combined displacements from these geometric considerations are non-negligible. The cloud information is used to initialize a radiative transfer model that computes the direct and diffuse-sky solar insolation at both shadow locations and intervening clear-sky regions. Here, we describe the formulation of the algorithm and validate its performance against Surface Radiation (SURFRAD; Augustine et al., 2000, 2005) network observations. Typical errors range from 8.5% to 17.2% depending on the complexity of cloud regimes, and an operational demonstration outperformed persistence-based forecasting of Global Horizontal Irradiance (GHI) under all conditions by ∼10 W/m2.

    更新日期:2017-12-07
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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