Comparison of Different Strategies for Heliostats Aiming Point in Cavity and External Tower Receivers

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Marco Binotti ◽  
Paolo De Giorgi ◽  
David Sanchez ◽  
Giampaolo Manzolini
Keyword(s):  
Energy Production ◽  
Heat Fluxes ◽  
Optical Simulation ◽  
Potential Cost ◽  
Reference Case ◽  
Optical Efficiency ◽  
Input And Output ◽  
Solar Plant ◽  
Peak Heat Flux ◽  
Efficiency Increase

This paper investigates different strategies for the reduction of peak heat fluxes on the receiver of a solar tower plant through the variation of the heliostats aiming points. The analysis is performed for two different solar tower receivers and heliostat field layouts. The innovative aspect of the work is in the methodology proposed: the effect of different aiming points is evaluated at different sun positions, and the yearly optical efficiency is calculated to determine drawbacks in terms of energy production. The optical simulation of the solar plant is performed with delsol through a matlab suite to easily manage the input and output. Preliminary assessments showed that the most important displacement is the vertical one, and the variation of the aiming point is important for the rows that are closer to the tower. With the appropriate strategy, the peak heat flux can be reduced by about 40% with limited spillage increase compared to the reference case. This result is similar for the two investigated plants, and it is confirmed also at different sun positions. The yearly optical efficiency with the optimal aiming strategy is reduced by less than 0.5% points. Future analysis will assess potential cost reductions and thermal efficiency increase brought about by the proposed strategies.

Mooring Sense Project: A Risk-Based Integrity Management Strategy for Mooring System of Floating Offshore Wind

2021 ◽  
Author(s):  
Alessandro La Grotta ◽  
Róisín Louise Harris ◽  
Clive Da Costa
Keyword(s):  
Energy Production ◽  
Management Strategy ◽  
Offshore Wind ◽  
Risk Level ◽  
Mooring System ◽  
Inspection Planning ◽  
Potential Cost ◽  
Operational Costs ◽  
Floating Offshore Wind Turbines ◽  
Integrity Management

Abstract While Floating Offshore Wind (FOW) represents a significant opportunity to foster wind energy development and to contribute to remarkable CO2 emissions reductions, its associated operational costs are still substantially above grid parity, and significant innovation is needed. MooringSense is a research and innovation project which explores digitisation technologies to enable the implementation of risk-based integrity management strategies for mooring systems in the FOW sector with the aim to optimise Operations and Maintenance (O&M) activities, reduce costs, and increase energy production. As part of this project, a risk-based assessment methodology specific for the mooring system of Floating Offshore Wind Turbines (FOWT) has been developed; this allows the development of a risk-based Mooring Integrity Management Strategy that can result in more cost-effective inspection planning. The methodology shall utilise the information made available by numerical tools, sensors, and algorithms developed in the project to update the risk level of the mooring system and set the required plan to mitigate the risk. Leveraging the additional information from monitoring technologies and predictive capabilities to determine the mooring system condition and remaining lifetime, the strategy provides the criteria for optimal decision making with regards to selection of O&M activities. The risk-based strategy developed allows for optimal planning of inspection and maintenance activities based on dynamic risk level that is periodically updated through the interface with the Digital Twin (DT). The validation of the strategy will demonstrate potential cost saving and economic advantages, however, it is expected that the overall MooringSense approach can reduce FOW farm operational costs by 10-15% and increase operational efficiency by means of an Annual Energy Production increase by 2-3%. The MooringSense project comprises of the development and validation of innovative solutions coming from multiple disciplines such as numerical modelling, simulation, Global Navigation Satellite System (GNSS), Structural Health Monitoring (SHM), and control systems which will provide valuable input to the risk-based mooring integrity management strategy.

Rewetting Velocity of High-Temperature Vertical-Narrow-Annular Flow Passages Under Counter-Current Flow Condition

2003 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Masanori Tsukudo ◽  
Naoki Sakamoto
Keyword(s):  
Heat Flux ◽  
Annular Flow ◽  
Pool Boiling ◽  
Outer Wall ◽  
Heat Fluxes ◽  
Annular Gap ◽  
Wall Superheat ◽  
Peak Heat Flux ◽  
Inner Diameter ◽  
Counter Current

Quenching of a thin gap annular flow passage by gravitational liquid penetration was examined experimentally by using R-113. The outer wall was made of copper. The inner wall was made of copper or glass. The inner diameter of the outer wall of the annular flow passages was 40 or 41 mm and the annular gap clearance δ was 0.5, 1.0, 2.0 and 5.0 mm. The outer wall was heated initially up to 250 °C and also the inner wall was heated when the copper inner wall was used. The quenching was observed in δ ≥ 1.0 mm. When δ = 0.5 mm, the wall was just gradually cooled down. The relation between the wall superheat and the heat flux during quenching process was similar to the boiling curve of pool boiling. However, the peak heat flux as well as the heat flux in the film and the transition boiling was lower than those in the pool boiling. These heat fluxes became lower as the gap clearance became narrow. The rewetting velocity became slow as the gap clearance became narrow. The rewetting velocity seemed to have a unique relation for the Peclet number Pe = (ρSCSδSU/λS) and the Biot number Bi = hδs/λs ; Pe ∝ Bi which was the same as that of the Yamanouchi correlation. A decrease in the heat flux (the heat transfer coefficient) in the rewetting front region, which corresponds to the peak heat flux, results in a decrease in the rewetting velocity as the gap clearance becomes narrow.

An Application of Quadratic Programming to Electrical Energy Production

1977 ◽  
Vol 9 (3) ◽  
pp. 273-284 ◽  
Author(s):  
N D Uri
Keyword(s):  
United States ◽  
Quadratic Programming ◽  
Marginal Cost ◽  
Energy Production ◽  
Cost Savings ◽  
Electrical Energy ◽  
The United States ◽  
Potential Cost ◽  
Societal Welfare ◽  
Electrical Energy Production

The issue that is addressed concerns the potential cost savings to a portion of the United States if the economic advantages some regions possess in generating electrical energy are passed on to other regions. The basic conclusions include the argument that a misallocation of electrical energy among consumer sectors exists, that societal welfare could be increased if the industry were to operate from an aggregate power-system viewpoint, and finally that the industry, in the aggregate, is charging a price in excess of the marginal cost of supplying electrical energy.

Preliminary Investigations of the Feasibility of In-Vessel Melt Retention Strategies for a Small Modular Reactor Concept

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Lena Andriolo ◽  
Clément Meriot ◽  
Nikolai Bakouta
Keyword(s):  
Heat Dissipation ◽  
Analytical Calculation ◽  
Heat Fluxes ◽  
Reference Case ◽  
Pressurized Water ◽  
Vessel Steel ◽  
Small Modular Reactor ◽  
Lower Head ◽  
Water Reactors ◽  
The Impact

The study presented in this paper is part of the technological surveillance performed at the Electricité De France (EDF) Research and Development (R&D) Center, in the Pericles department, and investigates the feasibility of modeling in-vessel melt retention (IVMR) phenomena for small modular reactors (SMR) with the modular accident analysis program version 5 in its EDF proprietary version (MAAP5_EDF), applying conservative hypotheses, such as constant decay heat after corium relocation to the lower head. The study takes advantage of a corium stratification model in the lower head of the vessel, developed by EDF R&D for large-sized prospective pressurized water reactors (PWRs). The analysis is based on a stepwise approach in order to evaluate the impact of various effects during IVMR conditions. First, an analytical calculation is performed in order to establish a reference case to which the MAAP5_EDF code results are compared. In a second step, the impact of the lower head geometry, vessel steel ablation, and subsequent relocation on the heat flux has been analyzed for cases where heat dissipation through radiation is neglected (in first approximation). Finally, the impact of heat losses through radiation as well as the crust formation around the pool has been assessed. The results demonstrate the applicability of the MAAP5_EDF code to SMRs, with heat fluxes lower than 1.1 MW/m2 for relevant cases, and identify modeling improvements.

On-Sun Testing of a High Temperature Bladed Solar Receiver and Transient Efficiency Evaluation Using Air

2018 ◽  
Author(s):  
Jesus D. Ortega ◽  
Sagar D. Khivsara ◽  
Joshua M. Christian ◽  
Pradip Dutta ◽  
Clifford K. Ho
Keyword(s):  
Heat Transfer ◽  
Light Trapping ◽  
Heat Fluxes ◽  
Heat Transfer Fluid ◽  
Test Facility ◽  
Flow Loop ◽  
Solar Absorptance ◽  
Cfd Models ◽  
Efficiency Increase ◽  
Solar Receiver

Prior research at Sandia National Laboratories showed the potential advantages of using light-trapping features which are not currently used in direct tubular receivers. A horizontal bladed receiver arrangement showed the best potential for increasing the effective solar absorptance by increasing the ratio of effective surface area to the aperture footprint. Previous test results and models of the bladed receiver showed a receiver efficiency increase over a flat receiver panel of ∼ 5–7% over a range of average irradiances, while showing that the receiver tubes can withstand temperatures > 800 °C with no issues. The bladed receiver is being tested at various peak heat fluxes ranging 75–150 kW/m2 under transient conditions using Air as a heat transfer fluid at inlet pressure ∼250 kPa (∼36 psi) using a regulating flow loop. The flow loop was designed and tested to maintain a steady mass flow rate for ∼15 minutes using pressurized bottles as gas supply. Due to the limited flow-time available, a novel transient methodology to evaluate the thermal efficiencies is presented in this work. Computational fluid dynamics (CFD) models are used to predict the temperature distribution and the resulting transient receiver efficiencies. The CFD simulations results using air as heat transfer fluid have been validated experimentally at the National Solar Thermal Test Facility in Sandia National Labs.

An Experimental Study of Miniature-Scale Pool Boiling

2003 ◽  
Vol 125 (6) ◽  
pp. 1074-1086 ◽  
Author(s):  
Tailian Chen ◽  
Jacob N. Chung
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Boiling Curve ◽  
Feedback Control System ◽  
Electronic Feedback ◽  
Fundamental Understanding ◽  
Peak Heat Flux ◽  
Different Temperatures

By generating single bubbles on a micro-heater at different wall superheats, an experimental study of miniature-scale pool boiling heat transfer has been performed to provide a fundamental understanding of the heater size effect. In this study, the constant-temperature microheater is set at different temperatures by an electronic feedback control system. The heat transfer history during the lifetime of a single bubble which includes nucleation, growth, detachment and departure has been measured. The boiling curve obtained from the microheater is composed of two regimes which are separated by a peak heat flux. It is suggested that in the lower superheat regime, the boiling is dominated by liquid rewetting and micro-layer evaporation, while in the higher superheat regime, conduction through the vapor film and micro-convection plays the key heat transfer role as the heater is covered by vapor all the time. In general, boiling on microheaters is characterized by larger bubble departure sizes, smaller bubble growth rates due to the dryout of microlayer as the bubble grows, and higher bubble incipience superheat. As the heater size decreases, the boiling curve shifts towards higher heat fluxes with corresponding higher superheats.

Transient Heat Flux Measurements in a Divided-Chamber Diesel Engine

1985 ◽  
Vol 107 (2) ◽  
pp. 439-444 ◽  
Author(s):  
A. C. Alkidas ◽  
R. M. Cole
Keyword(s):  
Heat Flux ◽  
Diesel Engine ◽  
Fluid Motion ◽  
Local Heat ◽  
Relative Increase ◽  
Heat Fluxes ◽  
Main Chamber ◽  
Peak Heat Flux ◽  
Flux Measurements ◽  
Local Heat Flux

Transient surface heat flux measurements were performed at several locations on the cylinder head of a divided-chamber diesel engine. The local heat flux histories were found to be significantly different. These differences are attributed to the spatial nonuniformity of the fluid motion and combustion. Both local time-averaged and local peak heat fluxes decreased with decreasing speed and load. Retarding the combustion timing beyond TDC decreased the peak heat flux in the antechamber but increased the peak heat flux in the main chamber. This is attributed to the relative increase in the portion of fuel that burns in the main chamber with retarded combustion timing.

Effect of Velocity on Heat Transfer to Boiling Freon-113

1980 ◽  
Vol 102 (1) ◽  
pp. 26-31 ◽  
Author(s):  
Salim Yilmaz ◽  
J. W. Westwater
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Atmospheric Pressure ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Forced Flow ◽  
Film Boiling ◽  
Square Root ◽  
Peak Heat Flux

Measurements were made of the heat transfer to Freon-113 at near atmospheric pressure, boiling outside a 6.5 mm dia horizontal steam-heated copper tube. Tests included pool boiling and also forced flow vertically upward at uelocities of 2.4, 4.0 and 6.8 m/s. The metal-to-liquid ΔT ranged from 13 to 125° C, resulting in nucleate, transition, and film boiling. The boiling curves for different velocities did not intersect or overlap, contrary to some prior investigators. The peak heat flux was proportional to the square root of velocity, agreeing with the Vliet-Leppert correlation, but disagreeing with the Lienhard-Eichhorn prediction of an exponent of 0.33. The forced-flow nucleate boiling data were well correlated by Rohsenow’s equation, except at high heat fluxes. Heat fluxes in film boiling were proportional to velocity to the exponent 0.56, close to the 0.50 value given by Bromley, LeRoy, and Robbers. Transition boiling was very sensitive to velocity; at a ΔT of 55° C the heat flux was 900 percent higher for a velocity of 2.4 m/s than for zero velocity.

scholarly journals Wind Blade Twist Correction for Enhanced Annual Energy Production of Wind Turbines

2021 ◽  
Vol 13 (12) ◽  
pp. 6931
Author(s):  
Mohammed Debbache ◽  
Messaoud Hazmoune ◽  
Semcheddine Derfouf ◽  
Dana-Alexandra Ciupageanu ◽  
Gheorghe Lazaroiu
Keyword(s):  
Energy Production ◽  
Twist Angle ◽  
Power Coefficient ◽  
Blade Profile ◽  
Reference Case ◽  
Wind Speeds ◽  
Blade Section ◽  
Drag Ratio ◽  
Lift To Drag Ratio ◽  
Important Design

Blade geometry is an important design parameter that influences global wind turbine energy harvesting performances. The geometric characteristics of the blade profile are obtained by determining the distribution of the chord and twist angle for each blade section. In order to maximize the wind energy production, implying a maximum lift-to-drag ratio for each wind speed, this distribution should be optimized. This paper presents a methodology to numerically determine the change in the twist angle by introducing a range of pitch angles for the maximum power coefficient case. The obtained pitch values were distributed from the root to the tip of blade. The results prove that the power coefficient increases for wind speeds greater than the rated point, which improves the yearly production of energy by 5% compared to the reference case.

A freeform collimator lens design for the Natural Light Illumination System

2019 ◽  
Vol 52 (1) ◽  
pp. 141-150
Author(s):  
W-C Tseng ◽  
AJ-W Whang ◽  
Y-Y Chen ◽  
J-Z Chen ◽  
T-H Yang ◽  
...  
Keyword(s):  
Total Internal Reflection ◽  
Transmission Efficiency ◽  
Luminous Flux ◽  
Optical Simulation ◽  
Light Illumination ◽  
Natural Light ◽  
Lens Design ◽  
Optical Efficiency ◽  
Freeform Surfaces ◽  
Illumination System

This paper presents the design of a collimator lens for use with the Lightbrick that uses total internal reflection as well as convex and concave surfaces. The Lightbrick is a light collector for the Natural Light Illumination System. The collimator lens is constructed using freeform surfaces which can be calculated through geometric-optics. Verified by optical simulation, using the collimator lens can achieve 90.3% luminous flux within ±2°, and optical efficiency improves by 48% in the collimator lens output. The collimator lens converges the light distribution of the Lightbrick and enhances the transmission efficiency of the Natural Light Illumination System.

Sign in / Sign up

Export Citation Format

Share Document