Showing papers in "Journal of Solar Energy Engineering-transactions of The Asme in 2017"

Deterministic and Stochastic Approaches for Day-Ahead Solar Power Forecasting

Abstract: Photovoltaic (PV) power forecasting has the potential to mitigate some of effects of resource variability caused by high solar power penetration into the electricity grid. Two main methods are currently used for PV power generation forecast: (i) a deterministic approach that uses physics-based models requiring detailed PV plant information and (ii) a data-driven approach based on statistical or stochastic machine learning techniques needing historical power measurements. The main goal of this work is to analyze the accuracy of these different approaches. Deterministic and stochastic models for dayahead PV generation forecast were developed, and a detailed error analysis was performed. Four years of site measurements were used to train and test the models. Numerical weather prediction (NWP) data generated by the weather research and forecasting (WRF) model were used as input. Additionally, a new parameter, the clear sky performance index, is defined. This index is equivalent to the clear sky index for PV power generation forecast, and it is here used in conjunction to the stochastic and persistence models. The stochastic model not only was able to correct NWP bias errors but it also provided a better irradiance transposition on the PV plane. The deterministic and stochastic models yield day-ahead forecast skills with respect to persistence of 35% and 39%, respectively.

10-MW Wind Turbine Performance Under Pitching and Yawing Motion

Abstract: The possibility of a wind turbine entering vortex ring state (VRS) during pitching oscillations is explored in this paper. The work first validated the employed computational fluid dynamics (CFD) method, and continued with computations at fixed yaw of the NREL phase VI wind turbine. The aerodynamic performance of the rotor was computed using the helicopter multiblock (HMB) flow solver. This code solves the Navier–Stokes equations in integral form using the arbitrary Lagrangian–Eulerian formulation for time-dependent domains with moving boundaries. With confidence on the established method, yawing and pitching oscillations were performed suggesting partial vortex ring state during pitching motion. The results also show the strong effect of the frequency and amplitude of oscillations on the wind turbine performance.

On the Spatio-Temporal End-User Energy Demands of a Dense Urban Environment

Abstract: Krarti Ahmed1, Luis E. Ortiz2, J.E. González2 1Ecole Polytechnique, Paris, France 2Mechanical Engineering Department, The City College of New York, NY 10031 Abstract Many growing major metropolitan centers face increased peak electrical load, especially during extreme heat events. This impacts the reliability of the electric grid raising the costs for energy demands. It is therefore imperative to better understand the energy consumption profile in the building sector for scales of large cities. This understanding is not only paramount to users to avoid peak demand charges but also to utilities to improve load management.

Integrating health into buildings of the future.

Abstract: The health and wellbeing of building occupants should be a key priority in the design, building, and operation of new and existing buildings Buildings can be designed, renovated, and constructed to promote healthy environments and behaviors and mitigate adverse health outcomes This paper highlights health in terms of the relationship between occupants and buildings, as well as the relationship of buildings to the community In the context of larger systems, smart buildings and green infrastructure strategies serve to support public health goals At the level of the individual building, interventions that promote health can also enhance indoor environmental quality and provide opportunities for physical activity Navigating the various programs that use metrics to measure a building's health impacts reveals that there are multiple co-benefits of a "healthy building," including those related to the economy, environment, society, transportation, planning, and energy efficiency

Aerodynamic Analysis of an Airfoil With Leading Edge Pitting Erosion

Abstract: Leading edge erosion is a considerable threat to wind turbine performance and blade maintenance, and it is very imperative to accurately predict the influence of various degrees of erosion on wind turbine performance. In the present study, an attempt to investigate the effects of leading edge erosion on the aerodynamics of wind turbine airfoil is undertaken by using computational fluid dynamics (CFD) method. A new pitting erosion model is proposed and semicircle cavities were used to represent the erosion pits in the simulation. Two-dimensional incompressible Reynolds-averaged Navier-Stokes equation and shear stress transport (SST) k-omega turbulence model are adopted to compute the aerodynamics of a S809 airfoil with leading edge pitting erosions, where the influences of pits depth, densities, distribution area, and locations are considered. The results indicate that pitting erosion has remarkably undesirable influences on the aerodynamic performance of the airfoil, and the critical pits depth, density, and distribution area degrade the airfoil aerodynamic performance mostly were obtained. In addition, the dominant parameters are determined by the correlation coefficient path analysis method, results showed that all parameters have non-negligible effects on the aerodynamics of S809 airfoil, and the Reynolds number is of the most important, followed by pits density, pits depth, and pits distribution area. Meanwhile, the direct and indirect effects of these factors are analyzed, and it is found that the indirect effects are very small and the parameters can be considered to be independent with each other.

Design And Characterization Of A 7.2 KW Solar Simulator

Abstract: A 7.2 kW radiative solar simulator was designed in order to perform accelerated testing on absorber materials for concentrating solar power (CSP) technologies. Computer-aided design (CAD) software integrating a ray-tracing tool was used to select appropriate components and optimize their positioning in order to achieve the desired concentration. The simulator comprises four identical units, each made out of an ellipsoidal reflector, a metal halide lamp and an adjustable holding system. A single unit was characterized and shows an experimental average irradiance of 257 kW m−2 on a 25.4 mm (1 inch) diameter spot. Shape, spot size and average irradiance are in good agreement with the model predictions. The innovative four-lamp solar simulator potentially demonstrates peak irradiance of 1140 kW m−2 and average irradiance of 878 kW m−2 over a 25.4 mm diameter spot. The costs per radiative and electric watt are calculated at $2.31 W−1 and $1.99 W−1, respectively.Copyright © 2015 by ASME

Equalizing Aerodynamic Blade Loads Through Individual Pitch Control Via Multiblade Multilag Transformation

Abstract: Control algorithms for rotor load mitigation are today generally adopted by industry. Most of them are based on the Coleman transformation, which is easy to implement and bears satisfactory results when the rotor is balanced. A multitude of causes, e.g., blade erosion, dirt, and especially pitch misalignment, may create significant imbalances. This gives birth to undesirable vibrations and reduced control performance in terms of load mitigation. In this paper, an alternative transformation is introduced, able to detect and quantify the rotor load harmonics due to aerodynamic imbalance. Next, a control algorithm, capable of targeting rotor imbalance itself and simultaneously lowering rotor loads, is presented. The effectiveness of the proposed solution is confirmed through simulations in virtual environment. [DOI: 10.1115/1.4037744]

Dye-Sensitized Solar Cell Using Saffron Petal Extract as a Novel Natural Sensitizer

Abstract: Natural dye extract of the saffron petal, purified by solid-phase extraction (SPE) technique, has been studied as a novel sensitizing dye to fabricate TiO2 nanoparticles-based dye-sensitized solar cells (DSSC). The extract was characterized using ultraviolet–visible (UV–Vis) and Fourier transform infrared (FTIR) spectroscopies to confirm the presence of anthocyanins in saffron petals. The typical current–voltage and the incident photon to current efficiency (IPCE) curves were also provided for the fabricated cell. The saffron petal extract exhibited an open-circuit voltage (Voc) of 0.397 V, short circuit current density (Jsc) of 2.32 mA/cm, fill factor (FF) of 0.71, and conversion efficiency of 0.66%, which are fairly good in comparison with the other similar natural dye-sensitized solar cells. These are mainly due to the improved charge transfer between the dye extract of saffron petal and the TiO2 anode surface. Considering these results, it can be concluded that the use of saffron petal dye as a sensitizer in DSSC is a promising method for providing clean energy from performance, environmental friendliness, and cost points of view. [DOI: 10.1115/1.4034908]