Denmark has achieved remarkable success in renewable energy generation over the last several decades. However, the country's goals of meeting its 50% energy demand from renewable by 2030 and becoming independent of fossil fuel by 2050 are currently in jeopardy due to the COVID-19 pandemic, which emerged at the end of December 2019 in the Chinese city of Wuhan. This study, therefore, tries to see how COVID-19 affects renewable electricity generation in Denmark using the advanced econometric framework. Several nonlinear estimation techniques such as Fourier ADL cointegration analysis and Markov Switching regression are used to estimate the relationship between the three channels of COVID19 and renewable electricity generation. The result from the Markov Switching regression reveals that renewable electricity production in Denmark is adversely affected by the enforced lockdown as captured via the stringency index, economic support provided to tackle the pandemic, and daily confirmed deaths of COVID-19. Moreover, the causality test shows that the stringency index and daily confirmed deaths of COVID-19 are important predictors of renewable electricity, but the economic support index has weak causality with renewable electricity. The study finally presents some crucial policy suggestions for Denmark which can help the country achieve its renewable production goals. (c) 2021 Elsevier Ltd. All rights reserved.

Solar water heating provides domestic hot water with lower greenhouse gas emissions compared to more typical natural-gas water heating. Solar water heating has a long history, particularly in places where the climate is favorable, such as California where state-backed incentive programs have been successful in creating small bursts of adoption. However, widespread adoption of solar water heating has not occurred in California despite these conditions. This research surveyed 227 single-family households with solar water heating across the state of California to understand their motivations and experiences, and draw implications regarding barriers to adoption. The survey explored households' experiences across five stages of adoption, as outlined in Rogers' Diffusion of Innovation theory: Knowledge, Persuasion, Decision, Implementation, and Confirmation. Findings revealed challenges at each stage. Most notably, prevalent disappointment in lower-than-expected energy and bill savings (31%) and high rates of technical problems (41%) appear to be the most significant issues. (c) 2021 Elsevier Ltd. All rights reserved.

Active and durable electrocatalysts for the oxygen evolution reaction (OER), capable of replacing noble metal catalysts, are required to develop efficient and competitive devices within the frame of the water electrolysis technology for hydrogen production. In this work, we have investigated tantalum based catalysts supported on carbon nanofibers (CNF) for the first time. The effect of CNF characteristics and the catalyst annealing temperature on the electrochemical response for the OER have been analyzed in alkaline environment using a rotating ring disc electrode (RRDE). The best OER activity and oxygen efficiency were found with a highly graphitic CNF, despite its lower surface area, synthesized at 700 degrees C, and upon a catalyst annealing temperature of 800 degrees C. The ordering degree of carbon nanofibers favors the production of oxygen in combination with a low oxygen content in tantalum oxides. The most active catalyst exhibited also an excellent durability. (C) 2021 The Authors. Published by Elsevier Ltd.

In this study, three SBCs are developed as (i) SBC with phase change material (PCM: waste cooking oil and C4H4O3), (ii) a novel SBC with nanocomposite PCM (NPCM), and (iii) a SBC without NPCM. The novel proposed cooker integrated with NPCM (MgAl2O4/Ni/Fe2O3-PCM) was experimentally developed and its performance was evaluated using fuzzy logic and Cramer's rules, and image processing techniques. The results indicated that the implementation of a bar plate absorber coated with MgAl2O4/Ni-doped, Fe2O3 nanoparticles, and integrated with PCM increases the cooker's internal temperature up to 164.12 degrees C. The used nanocomposite materials were in the average particle size of 20 mu m. The cooking materials were verified with the temperature in the segmentation process. The NPCM indicated the SBC's thermal performance enhancement of 11% in comparison with the SBC with PCM and without NPCM. Additionally, the overall thermal performance of SBCs without NPCM, with PCM, and with NPCM was obtained as 24.90-33.90%, 24.77-45.20%, and 31.77-56.21%, respectively. Moreover, the temperature of the bar plate absorber was achieved as 163.74 degrees C, 147 degrees C, and 113.34 degrees C for the SBC with NPCM, PCM, and without NPCM, respectively, under the solar radiation of 1,037 W/m(2). (C) 2021 Elsevier Ltd. All rights reserved.

The catalytic co-pyrolysis of torrefied poplar wood sawdust (TPW) and high-density polyethylene (HDPE) was investigated over hierarchical HZSM-5. Compared with raw PW/HDPE, the bio-oil yield from co-pyrolysis of TPW/HDPE decreased gradually while the quality of bio-oil was upgraded. With increasing torrefaction temperature from 220 to 280 degrees C, the amounts of acids, furans, and anhydrosugars in bio-oil were significantly reduced due to the removal of hemicellulose, whereas the production of phenols and alkenes were improved due to the enhanced hydrogen transfer reaction. In the catalytic co-pyrolysis, increasing torrefaction temperature caused an enhanced production of mono-aromatics as well as the selectivity of BTX (benzene, toluene, and xylene). Nevertheless, severe torrefaction (280 degrees C) lead to a rapid reduction of aromatic yield and selectivity due to the loss of cellulose. Compared to parent HZSM-5, hierarchical HZSM-5 treated with alkaline concentration (0.2-0.3 mol/L) favored the formation of mono aromatics at the expense of polyaromatics. The maximum mono-aromatics yield of 71.75% was obtained during catalytic co-pyrolysis of 260-TPW/HDPE over 0.3-HZSM-5. The present work suggests that torrefaction pretreatment followed by the catalysis of hierarchical HZSM-5 is an efficient way to promote the production of valuable mono-aromatic hydrocarbons from biomass and plastic wastes. (C) 2020 Elsevier Ltd. All rights reserved.

At present study, carbon nanotube-graphene (CNT-G) supported PtAu, Au and Pt catalysts were prepared by microwave-assisted synthesis method to investigate the direct liquid-fed sodium borohydride/hydrogen peroxide (NaBH4/H2O2) fuel cell performance. Prepared catalysts were characterized by TGA, XRD, TEM, ICP-OES, cyclic voltammetry and rotating disc electrode (RDE) voltammetry. The catalysts were tested in a single NaBH4/H2O2 fuel cell with 25 cm(2) active area to evaluate fuel cell performance. The effects of temperature and fuel concentration on fuel cell performance were examined to observed best operating conditions. As a result of direct NaBH4/H2O2 fuel cell experiments, maximum power densities of 139 mW/cm(2), 125 mW/cm(2) and 113 mW/cm(2) were obtained for PtAu/CNT-G, Au/CNT-G and Pt/CNT-G catalysts, respectively. PtAu/CNT-G catalyst showed the enhanced NaBH4/H2O2 fuel cell performance, which was higher than the Pt/CNT-G catalyst and Au/CNT-G catalyst at 50 degrees C. The enhanced NaBH4/H2O2 performance can be attributed to synergistic effects between Pt and Au particles on CNT-G support providing a better catalyst utilization and interaction. These results suggest that the prepared PtAu/CNT-G catalyst is a promising anode catalyst for NaBH4/H2O2 fuel cell application. (c) 2020 Elsevier Ltd. All rights reserved.