scholarly journals A Selective Solar Absorber for Unconcentrated Solar Thermal Panels

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 900
Author(s):  
Davide De Maio ◽  
Carmine D’Alessandro ◽  
Antonio Caldarelli ◽  
Daniela De Luca ◽  
Emiliano Di Gennaro ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
High Vacuum ◽  
Optimization Procedure ◽  
Energy Transition ◽  
Spectral Emissivity ◽  
Thermal Conversion ◽  
Stagnation Temperature ◽  
Solar Absorber ◽  
Analytical Formulas ◽  
Set Up

A new Selective Solar Absorber, designed to improve the Sun-to-thermal conversion efficiency at mid temperatures in high vacuum flat thermal collectors, is presented. Efficiency has been evaluated by using analytical formulas and a numerical thermal model. Both results have been experimentally validated using a commercial absorber in a custom experimental set-up. The optimization procedure aimed at obtaining Selective Solar Absorber is presented and discussed in the case of a metal dielectric multilayer based on Cr2O3 and Ti. The importance of adopting a real spectral emissivity curve to estimate high thermal efficiency at high temperatures in a selective solar absorber is outlined. Optimized absorber multilayers can be 10% more efficient than the commercial alternative at 250 °C operating temperatures, reaching 400 °C stagnation temperature without Sun concentration confirming that high vacuum flat thermal collectors can give important contribution to the energy transition from fossil fuels to renewable energy for efficient heat production.

scholarly journals Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity

2020 ◽  
Author(s):  
Davide De Maio ◽  
Carmine D'Alessandro ◽  
Antonio Caldarelli ◽  
Marilena Musto ◽  
Daniela De Luca ◽  
...  
Keyword(s):  
Thermal Model ◽  
High Vacuum ◽  
Analytical Formula ◽  
Optimization Procedure ◽  
Spectral Emissivity ◽  
Thermal Conversion ◽  
Stagnation Temperature ◽  
Solar Absorber ◽  
Set Up

This study refers to the optimization of a Selective Solar Absorber to improve the Sun-to-thermal conversion efficiency at mid temperatures in high vacuum flat thermal collectors. Efficiency has been evaluated by using analytical formula and a numerical thermal model. Both results have been experimentally validated using a commercial absorber in a custom experimental set-up. The optimization procedure aimed at obtaining Selective Solar Absorber is presented and discussed in the case of a metal dielectric multilayer based on Cr2O3 and Ti. The importance of adopting a real spectral emissivity curve to estimate high thermal efficiency at high temperatures in selective solar absorber is outlined. Optimized absorber multilayers can be 8% more efficient than the commercial alternative at 250 °C operating temperatures and up to 27% more efficient at 300 °C. Once the multilayer has been optimized the choice of a very low emissivity substrate such as copper allows to further improve efficiency and to reach stagnation temperature higher than 400 °C without Sun concentration.

scholarly journals Efficiency of Selective Solar Absorber in High Vacuum Flat Solar Thermal Panels: The Role of Emissivity and Cut-Off Wavelength

2020 ◽  
Author(s):  
Davide De Maio ◽  
Carmine D'Alessandro ◽  
Antonio Caldarelli ◽  
Marilena Musto ◽  
Daniela De Luca ◽  
...  
Keyword(s):  
High Vacuum ◽  
Analytical Formula ◽  
Optimization Procedure ◽  
Thermal Conversion ◽  
Metallic Substrate ◽  
Stagnation Temperature ◽  
Solar Absorber ◽  
Proper Design ◽  
Low Emittance

A multilayer structure on a metallic substrate has been optically simulated and the optimization procedure aimed at obtaining Selective Solar Absorber (SSA) is discussed. This study refers to flat high vacuum thermal collectors and the overall Sun-to-thermal conversion efficiency has been evaluated using analytical formula and numerical thermal model. Both methods are in agreement and they have been validated using experimental results on a commercial absorber. The importance of a low emittance value to obtain high thermal efficiency at high temperatures and high stagnation temperature in selective solar absorber is highlighted. Optimized absorbers can be 8% more efficient than the commercial alternative at 250 °C operating temperatures and up to 27% more efficient at 300 °C. A stagnation temperature higher than 400 °C can be reached without Sun concentration if the proper design is adopted.

scholarly journals Multilayers for Efficient Thermal Energy Conversion in High Vacuum Flat Solar Thermal Panels

2021 ◽  
Author(s):  
Davide De Maio ◽  
Carmine D'Alessandro ◽  
Antonio Caldarelli ◽  
Daniela De Luca ◽  
Emiliano Di Gennaro ◽  
...  
Keyword(s):  
Fossil Fuels ◽  
High Vacuum ◽  
Energy Transition ◽  
Thermal Conversion ◽  
Stagnation Temperature ◽  
Optical Analysis ◽  
Sputtering Deposition ◽  
Solar Absorbers ◽  
Thermal Energy Conversion ◽  
Operating Temperatures

Multilayer absorbers based on Cr2O3 and Cr, designed to improve the Solar-to-thermal conversion efficiency at mid temperatures in high vacuum flat thermal panel, are fabricated via sputtering deposition on bulk copper substrates and characterized by thermal and optical analysis. The refractive index of the single layers has been measured and used to estimate absorber thermal efficiency at the operating temperatures. Multilayers have been produced via sputtering deposition on bulk copper substrates. The absorber multilayers can be 10% more efficient than the commercial alternative at 250 °C operating temperatures, reaching 380 °C stagnation temperature without Sun concentration. The thermal stability has been checked at temperature of 400 °C in vacuum for four hours. High vacuum flat thermal collectors, equipped with the produced selective solar absorbers can obtain unprecedented performances and can give important contribution to the energy transition from fossil fuels to renewable energy for efficient heat production.

Pulp pumping efficiency II – Designing of a pulp pump

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Qihua Zhang ◽  
Shun Kang ◽  
Zhiang Xie ◽  
Li Cao ◽  
Zhaoxu Yan ◽  
...  
Keyword(s):  
Optimization Procedure ◽  
Tip Clearance ◽  
Impeller Blade ◽  
Pumping System ◽  
Pumping Efficiency ◽  
Erosion Corrosion ◽  
Efficiency Increase ◽  
Set Up ◽  
Designing Method ◽  
Optimal Designing

Abstract Based on the loss model of pulp pump set up in the I part of this research, an efficient designing method is proposed by taking account of the influences of head reduction by small blade number, leakage loss via tip clearance, and erosion-corrosion wears in pumps separately. Further, a two-stage optimal designing approach was proposed to tackle the oversized design. The pump designing was performed by coupling with a CFD-based optimization procedure. An efficiency increase of near 10 % was achieved on the pump model validated in laboratory. It was proved that performance could be improved by increasing the impeller blade width and enlarging the impeller blade outlet angle. It was further shown that the erosion-corrosion wear in pulp pump was relatively lighter when compared to particle-impingement wear in slurry and sewage pump. Adoption of composite material showed potential in energy-saving in the pumping system.

scholarly journals Set-up of a high-resolution 300 mK atomic force microscope in an ultra-high vacuum compatible 3He/10 T cryostat

2016 ◽  
Vol 87 (7) ◽  
pp. 073702 ◽  
Author(s):  
H. von Allwörden ◽  
K. Ruschmeier ◽  
A. Köhler ◽  
T. Eelbo ◽  
A. Schwarz ◽  
...  
Keyword(s):  
High Resolution ◽  
Atomic Force Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Atomic Force ◽  
Set Up

Effect of Nanosized Filler on Matrix Dominated Properties of Fiber Reinforced Epoxy

2011 ◽  
Author(s):  
Yuanxin Zhou ◽  
Shaik Jeelani
Keyword(s):  
Compression Strength ◽  
High Speed ◽  
High Vacuum ◽  
Trapped Air ◽  
Nano Fiber ◽  
Open Hole ◽  
Set Up ◽  
Mechanical Agitator ◽  
Laminar Shear ◽  
Nanosized Filler

In this study, a high-intensity ultrasonic liquid processor was used to obtain a homogeneous molecular mixture of epoxy resin and carbon nano fiber. The carbon nano fibers were infused into the part A of SC-15 (diglycidylether of Bisphenol A) through sonic cavitations and then mixed with part B of SC-15 (cycloaliphatic amine hardener) using a high-speed mechanical agitator. The trapped air and reaction volatiles were removed from the mixture using high vacuum. Nanophased epoxy with 2 wt.% CNF was then utilized in a vacuum assisted resin transfer molding (VARTM) set up with carbon fabric to fabricate laminated composites. The effectiveness of CNF addition on matrix dominated properties of composites has been evaluated by compression, open hole compression and inter-laminar shear. The compression strength, open hole compression strength and ILS were improved by 21%, 23% and 15%, respectively as compared to the neat composite.

scholarly journals Co-Movements between Eu Ets and the Energy Markets: A Var-Dcc-Garch Approach

Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1787
Author(s):  
Pilar Gargallo ◽  
Luis Lample ◽  
Jesús A. Miguel ◽  
Manuel Salvador
Keyword(s):  
Fossil Fuels ◽  
Spillover Effect ◽  
Warning System ◽  
Energy Transition ◽  
Clean Energy ◽  
Stock Index ◽  
Phase Iii ◽  
Response Analysis ◽  
Eu Ets ◽  
The Eu

This paper analyzes the co-movements of prices of fossil fuels, energy stock markets and EU allowances. This analysis is conducted in order to identify the spillover effect of volatility and correlation among these financial markets, and to provide a scientific basis that shows the interest of incorporating sustainable assets in the design of minimum risk strategies of investment. To achieve this goal, we have used a Vector Autoregressive-Dynamic Conditional Correlation-Generalized Autoregressive Conditional Heteroscedasticity (VAR-DCC-GARCH) model that also incorporates a stock index of industrial companies as a leading indicator of the level of economic activity. In addition, the paper conducts an impulse response analysis to determine how unexpected shocks to prices are propagated along time, and, in particular, how they affect prices of the others, both in mean, variance and correlation. Therefore, the results of this one- and two-dimensional analysis allow for the study of short and long run dynamics of the relationship among those prices, thus, providing greater meaning and information for investors, which has implications for building their portfolios. The analyzed period was from January 2010 to February 2021, so that the data include half of phase II, full phase III and the onset of phase IV of the EU ETS, as well as the COVID-19 outbreak in the European context. We also analyzed whether the EUA price impulses the demand of clean energy stocks, which has important implications for the objective of triggering the investment in clean energy. Our results show the transmission mechanism of all of those prices, which are relevant not only for investors but also for policymakers to construct an early-warning system, revealing the most important transmission channels. Moreover, from an investment viewpoint, we observe a decline in dirty energies and a rise in the clean energy market, which might be an indication of the progress towards the energy transition to renewables sources within a circular economy perspective. Therefore, this shows that the EU ETS is achieving its goals, and that clean energy companies, aligned with their role towards socially responsible initiatives, are also gaining acceptance in terms of investments, which would be beneficial for the environment.

scholarly journals Energy Transition and Climate Change in Decision-Making Processes

2021 ◽  
Vol 13 (23) ◽  
pp. 13404
Author(s):  
Georgios Tsantopoulos ◽  
Evangelia Karasmanaki
Keyword(s):  
Climate Change ◽  
Decision Making ◽  
Fossil Fuels ◽  
Fossil Fuel ◽  
Energy Transition ◽  
Decision Making Processes ◽  
Fuel Technology

Humans have been using fossil fuels for centuries, and the development of fossil fuel technology reshaped society in lasting ways [...]

scholarly journals Device for calibration of low pressure gauges development

2002 ◽  
Vol 2 (4) ◽  
pp. 189-195
Author(s):  
Z.D. Nikitovic
Keyword(s):  
High Vacuum ◽  
Low Pressure ◽  
Calibration Procedure ◽  
Vacuum System ◽  
Molecular Collision ◽  
Gas Discharges ◽  
Dry Air ◽  
Vacuum Region ◽  
Set Up ◽  
Made In

Vacuum system set-up is presented and used for calibration of pressure gauges in the region of rough vacuum, from 103 mbar to 10-1 mbar, with dry air. The capacitance manometer is used for the calibration of piezoresistant manometer, oil, mercury and mercury micrometers U manometers. The applicability of the experimental set-up and obtained results for the low pressure gauges calibration in the medium and high vacuum region is approved. It was shown how calibration of some cheaper pressure gauges might be performed and reliable measurements of the pressure may be made in the region that is of interest for atomic and molecular collision physics and low-pressure gas discharges. It was also shown that mentioned calibration procedure could be used for calibration of different U manometer types in order to renormalize older atomic and molecular collision data.

scholarly journals Should Countries Fire Sell their Oil & Gas Assets? Addressing the Mis-conceptions Surrounding the Continued Role of Fossil Fuels in the Energy Transition Era

2021 ◽  
Vol 11 (2) ◽  
pp. 432-440
Author(s):  
Victoria R. Nalule ◽  
Xiaoyi (Shawn) Mu
Keyword(s):  
Fossil Fuels ◽  
Energy Transition ◽  
Low Carbon ◽  
Energy Access ◽  
Poverty Eradication ◽  
Low Carbon Economy ◽  
Tackle Climate Change ◽  
Oil Gas ◽  
Carbon Economy

Access to modern energy such as electricity is key in the economic development of any country, and yet over 600 million people remain with no access to electricity in developing countries. It is true that both renewable energy and fossil fuels are key in the achievement of the United Nations Sustainable Development (UN SDG) Goal 7 and Goal 1 on energy access and poverty eradication respectively. However, the current global efforts to transition to a low carbon economy, and tackle climate change as stipulated in the SDG 13 and the 2015 Paris Agreement, have created a lot of tension on fossil fuel developments in recent years.This commentary article is presented as a question and answer session aimed at addressing the misconceptions surrounding the achievement of SDG 7 and SDG 13 in this energy transition era. The paper is of interest to oil producing countries. The article follows the various questions raised by policymakers during an online seminar delivered by both the authors entitled, ‘Fossil Fuels in the Energy Transition Era’.

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