Energy Conversion and Management-X最新文献

Wind energy plays a pivotal role in the ongoing effort to reduce carbon emissions in the energy sector. With the increasing evidence of climate change, there is a growing concern regarding the planning and operation of wind energy resources. Accurate forecasts are essential to understand the frequency distribution of wind speed data in a given area and, consequently, to estimate energy production. This paper aims to analyze the wind resources under climate change, assess their potential, and create zoning maps for wind energy production in the island of Ireland. For this objective, wind speed data from 31 general circulation models (GCMs) and two climate change scenarios were utilized for both hindcast and forecast periods in 1981–2010 and 2021–2050, respectively. The GCM outputs were first bias-corrected and then post-processed using various (non–)parametric statistical distributions and 3 Copula families. The results indicate an expected decrease in the average wind speed in the region up to ∼ 21 % by 2050, contingent on the climate scenarios under consideration and the target point. Ultimately, this study concludes by presenting wind power density maps specifically to the study region, offering valuable insights for sustainable energy planning.

Macroalgae blooms have been observed along the coastal zones of the Baltic Sea in recent decades, possibly as a result of global climate change. Excess algae biomass washed ashore the beaches reduces their attractiveness for recreational activities, produces greenhouse gases, and causes secondary pollution. To assess the most promising technology for processing excess beach-cast seaweed biomass into liquid biofuel, researchers conducted an inventory and a life cycle assessment analysis (LCA) of two thermochemical technologies: hydrothermal liquefaction (HTL) and pyrolysis. The resulting liquid fuels are expected to be used as heavy fuel oil (HFO) or fuel oil grade 6 in accordance with ASTM D396 in a mixture with HFO from fossil sources. The production of HFO from fossil sources was used as a basic comparison scenario. If one considers the possibility of replacing part of fossil hydrocarbons with synthetic fuels from seaweed biomass, the most climate-neutral would be Ulva sp. pyrolysis (GWP100 884.3 kg CO2-Eq per 1 Mg of fuel), but HTL would have GWP100 only for 9.6 % higher (969.6 kg CO₂-Eq per 1 Mg of fuel). Environmental and climatic impacts of pyrolysis and HTL are very sensitive to the type of electricity used, so shifting from a traditional electricity source to wind energy leads to GWP100 decreasing to a level of 838 and 628 kg CO2-Eq per 1 Mg of fuel for pyrolysis and HTL, respectively, and HTL becoming a technology with less environmental impact. In baseline scenario the ozone depletion potential for the two processes under consideration is almost equal (difference is only 2.4 %). HTL is more sustainable in comparison with pyrolysis in term of human toxicity (HTL potential is 1.6 times lower) and terrestrial acidification (HTL potential is 1.9 times lower).

In this paper, we introduce a novel two-degree-of-freedom piezoelectric stack hybrid energy harvester including a piezoelectric stack and a set of piezoelectric layers. By incorporating a mechanical stopper and bending leaf springs to achieve frequency up-conversion, we significantly enhance the voltage response of the system. We compare the output performance of prototypes with different spring stiffness. The experimental results show that, at a frequency of 7.8 Hz and an acceleration of 0.8 g, the piezoelectric layers on the lower beam of bending leaf springs generate a peak voltage of 18.92 V, and its instantaneous output power is 32 mW. Meanwhile, the piezoelectric stack produces a peak voltage of 28.56 V, with an instantaneous output power of 3.83 W. Moreover, an increase in the stiffness of the bending leaf spring leads to a decrease in voltage response and power output. This research can facilitate the development of hybrid piezoelectric self-powered applications.

As the world addresses the increasing demand for sustainable energy solutions, biodiesel has surfaced as a viable alternative to conventional fossil fuels. The expansion of biodiesel feedstock plantations, particularly palm oil in tropical regions, can lead to deforestation, loss of biodiversity, and significant carbon emissions from the destruction of carbon-rich ecosystems. That is why this article focuses on biodiesel production from waste sources in order to maintain balance in the ecosystem. This review paper discusses the global energy landscape and the need for renewable and environmentally friendly alternatives. It explores the various waste sources in depth that are investigated for biodiesel production, comprising waste cooking oil, animal fats, algae, and other organic residues. Each feedstock is analyzed for its viability, challenges, and economic feasibility in biodiesel production. A critical assessment of different biodiesel production methods, such as transesterification, pyrolysis, thermochemical conversion, anaerobic digestion, thermal cracking, hydro-treating and enzymatic processes, is presented, highlighting the key factors influencing their efficiency and scalability. Recent developments to enhance waste-derived biodiesel production’s sustainability and economic viability to meet UN Sustainable Development Goals are also highlighted. Furthermore, the environmental impact of biodiesel, including greenhouse gas emissions and land use, is discussed to provide a holistic understanding of its ecological footprint. The biodiesel from waste sources can significantly increase the brake thermal efficiency of the engine along with a substantial decrease in emissions like CO and HC. However, the NOx and CO₂ emissions are increased with the application of biodiesel from waste sources. The CO₂ and NOx emissions can be reduced by exhaust gas recirculation and selective catalytic reduction techniques. The paper also addresses regulatory frameworks and standards governing biodiesel production from waste sources, emphasizing the need for harmonized policies to encourage widespread adoption. The paper concludes by outlining future research directions and potential breakthroughs that could further enhance biodiesel production’s effectiveness, sustainability, and scalability from waste sources. Waste Cooking Oil (WCO) and animal fats are currently the most economically feasible options for biodiesel production due to their low cost and established collection and processing infrastructure. Algae present high potential but require technological advancements and cost reductions to become economically viable. This review aims to assist researchers, policymakers, and industry stakeholders in advancing the utilization of waste materials for biodiesel production, promoting a more sustainable energy landscape.

Electricity generation will need to reach net zero emissions globally in 2050. This will require an increase in share of renewable energy and the implementation of a controllable carbon-free base-load source. Nuclear fusion is a promising option to decarbonize base-load electricity production but its capital cost still doubles the one of technologically more mature alternatives such as large photovoltaic fields or off-shore wind installations. Within this framework, the retrofit of a dismissed power-plant could allow significant cost savings, thus facilitating the realization of a fusion electricity demonstrator. Among fusion reactors, stellarators are a valid alternative to tokamaks thanks to the higher blanket temperature and inherent continuous operation. In this scenario, we posit the challenge to use a nuclear fusion stellarator-based reactor to retrofit conventional power plants (PPs). Specifically, we select a nuclear fission plant in France and a supercritical coal fired site in Italy, by constructing 4 different retrofit scenarios as a function of the re-used components. We compare each option with a greenfield and optimized plant with the same reactor thermal power. through a thermodynamic, economic, and investment analysis.

The results proves significant savings by retrofitting an existing plant, with a CapEx reduction up to $50\%$ compared to the greenfield plants. Specifically, the most convenient retrofit strategy is to select a site that already implements cutting edge thermodynamic parameters while reusing the most existing systems (i.e. buildings, steam cycle, electricity generation, and heat rejection). This is the case of the 2 x 660 MW_e supercritical coal-fired plant in Italy. Therein, the LCOEs are 39 $/MWh and 51 $/MWh, calculated with an interest rate of $2.7\%$ and $6\%$, respectively, and compare with the conventional energy technologies. Moreover, such costs are competitive in the current European energy markets and yield significant net present values at the plant end of life.

The reversible reaction Ca(OH)₂ + 104.4 kJ/mol ⇌ CaO + H₂O offers several advantages as energy storage system. For example, it possesses a higher energy density than lead-acid or nickel–cadmium batteries. In addition, it has proven cyclability, low cost and worldwide availability. For this reason, it is suitable for seasonal heat storage applications. However, the raw powder material displays properties that represent a major challenge for the design of reactors that decouple power from capacity e.g. low thermal conductivity, cohesivity and tendency to form agglomerates. In order to overcome these drawbacks, different approaches to stabilize the Ca(OH)₂/CaO particles have been investigated e.g. shaping, micro encapsulation, macroencapsulation, etc. The assessment of the stabilized products, however, has limitations in terms of amount of mass and reaction conditions as it is carried out in TA (thermal analyzer). Furthermore, it does not allow to analyze the structural decay and agglomeration of stabilized particles in-situ. For this reason, a more comprehensive assessment of a bulk of material under reactor conditions is necessary. In this work, a reaction chamber is developed to enable the observation of a bulk of storage material (0.1 L) during thermal cycling. Thus, two samples were subject of 20 cycles of dehydration and rehydration. The experiments were carried out at a temperature range of 350 °C – 500 °C and water vapor pressure of 0 – 1 bar. The analysis of images and post experiment tests (e.g. thermogravimetric analysis (TGA), dynamometry, X-ray diffraction (XRD) analysis) prove that the mechanical strength and structural integrity resulted enhanced for both samples. In addition, it allows to further understand the bulk behavior of Ca(OH)₂ granules and thus important implications for the design of technical scale reactors can be derived.

This study provides a comprehensive evaluation of the techno-economic and environmental performance of six hybrid energy systems (HESs) in Kunder Char, Bangladesh, incorporating both conventional (diesel and natural gas) and renewable energy sources (solar and wind). Using HOMER Pro software, a comparative analysis of five off-grid systems and one on-grid system are conducted for assessing their cost-effectiveness, energy efficiencies, and environmental impacts under various sensitivity conditions. After thorough evaluation the on-grid system has emerged as the most economically viable option, with a levelized cost of energy (LCOE) of $0.0436/kWh and a net present cost (NPC) of $1.43 million. It also produced minimal waste energy (0.381 %) but with high CO₂ emissions. In contrast, the PV-Battery setup, though the most expensive with an LCOE of $0.266/kWh and an NPC of $3.36 million, offered the benefit of zero emissions and generated 40 % excess electricity. Sensitivity analyses highlighted the influence of solar radiation (4.45 kWh/m²/day), wind speed (4.81 m/s), and fuel price (Diesel: $1/L) on these systems, providing insights into their operational dynamics under varying environmental and economic scenarios. The findings highlight the trade-offs between cost, sustainability, and efficiency, promoting energy solutions customized to meet the specific needs of remote regions like Kunder Char. This study also helps in understanding the potential of hybrid systems to meet energy demands sustainably in challenging geographical and economic landscapes.

Closed-loop systems enable circular economy systems and applications in the food and beverage sector to enhance decarbonisation. Whiskey distillation by-products are amenable to anaerobic digestion and thus facilitate resource recovery and circularity. Furthermore, biochar derived from whiskey barrels can be used as a carbonaceous additive within anaerobic digestion to enhance biomethane production. In this paper, biochar produced from the pyrolysis of discarded whiskey barrels at 300 °C, was shown to enhance biomethane production by up to 15 %. A kinetic analysis revealed that the biochar reduced the biomethane lag time by up to 42 %. The mass and energy balance of this integrated anaerobic digestion-pyrolysis system was evaluated. The overall system efficiency was assessed at 68 % of all input energy (expressed on a primary energy basis); utilisation of renewable electricity could increase this efficiency to 71 %. Biochar from discarded whiskey barrels can provide a decarbonisation pathway for whiskey distilleries but may be constrained by the total resource available.

SiC-based duplex claddings, consisting of monolithic SiC and SiC/SiC fiber composite, are emerging as a promising candidate for accident-tolerant fuel (ATF) systems in nuclear reactors. To analyze the performance of ATFs with SiC-based duplex claddings, a comprehensive computational analysis framework is presented that captures the essential properties and behaviors of the UO₂-SiC fuel system. Utilizing a previously developed continuum damage model, the pseudo-ductile behavior of SiC/SiC fiber composites is accurately modelled, connecting damage evolution parameters to instantaneous stiffness matrix degradation. This framework is used to investigate the performance of UO₂-SiC fuel rods under normal operating conditions and a typical Loss of Coolant Accident (LOCA) scenario. We assess the effects of the thickness ratio of the monolithic SiC and SiC-based composite layers, as well as pellet-clad cold gap thickness on the failure and leakage probabilities of the cladding. These claddings, with a thickness ratio ranging from 0.25 to 0.75, demonstrated minimal failure and leakage probabilities for both the original and reduced pellet-clad gap thickness (82.5/70 µm). When the gap thickness was further reduced to 57.5 µm, pellet-cladding mechanical interaction was observed and this greatly elevated the failure probability of the MSiC layer, thus giving rise to a loss of hermeticity. This research underscores the significant role of varying individual layer thicknesses in shaping fuel rod safety and offers potential for optimization across diverse operational conditions.

Photovoltaic-thermoelectric hybrid devices aim at harvesting the entire solar spectrum via both direct photovoltaic conversion and subsequent thermoelectric conversion of the heat generated in the solar cell. One emerging strategy to improve their efficiency is to implement a photothermal interface between the photovoltaic cell and the thermoelectric module. Modeling such a complex system (photovoltaic cell, photothermal interface and thermoelectric generator) to design an optimal architecture is a challenging task, as it requires to take into account a large number of parameters in a multi-layered system, as well as the coupling between optical, thermal and electrical effects. To do so, we present here a multiphysics tool to predict the temperature distribution and power output of hybrid devices integrating a photothermal interface. Our model shows a good quantitative agreement with previous theoretical and experimental works from the literature using limited material parameters. We discuss the need for additional parameters for accurate modeling of experimental devices. We envision that our multiphysics modeling tool will be key for the design of optimal photothermal interfaces for efficient photovoltaic-thermoelectric hybrid devices.