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[en] Highlights: • Methods is outlined to improve the efficiency of heat-induced solar thermionic converter. • Optimization of materials and structure is summarized for photon-enhanced thermionic converter. • Combined systems with thermionic energy converters is proposed for concentrating solar power. • Roadmap of thermionic energy conversion for concentrating solar power is brought forward. - Abstract: Concentrating solar power (CSP) is a mainstream of solar energy utilization, and thermionic emission is a potential way to convert concentrated solar radiation into power with a theoretical efficiency of 50–70%, surpassing both Shockley-Queisser limit and photo-thermal limit. This literature attempts to provide a comprehensive understanding of and an insight into solar thermionic energy conversion. The fundamentals of electron emission from electrodes and electron transport in vacuum gap are presented, as well as the state of the art of solar thermionic energy conversion technologies, including heat-induced thermionics and photon-enhanced thermionics. The former is driven by thermal energy, whereas the latter takes advantage of both quantum photon energy and thermal energy. Burgeoning research indicates that photon-enhanced thermionic conversion is a promising technology for concentrating solar power due to the high efficiency and simple operating mode. Now, it is important to develop novel materials and coating technologies to facilitate electron emission and reduce space charge effect in interelectrode vacuum. Structural design of thermionic converters and top–bottom configuration of solar-electricity systems are suggested for practical applications.
[en] Highlights: • A novel portable solar collector mechanism is optimally designed. • Wireless power transfer is first applied to cooling systems. • A supercapacitor stores electricity and outputs a regulated supply. • The proposed cooling system shows high efficiency in a limited space. - Abstract: As the greenhouse effect becomes increasingly serious, cooling a vehicle cabin parked under the blazing sun without running the engine or using an electric vehicle’s power has received considerable attention. In this paper, we develop a novel portable, renewable, solar energy-powered cooling system with wireless power transfer (WPT) and supercapacitors to cool the vehicle cabin. The proposed system consists of a solar collector mechanism, an energy conduit, and a temperature control and cooling module. First, consisting of folding solar photovoltaic (PV) panels, the solar collector mechanism making the proposed system portable. Once collected, the solar energy is converted into electricity and stored in the supercapacitors through wireless power transfer without breaching the vehicle body. Automatic temperature regulation is achieved with the cooling device via the temperature control and cooling module. The experimental results indicate that a maximum output power of 2.181 W and a maximum WPT efficiency of 60.3% are achieved when the prototype loaded with 3 Ω and 5 Ω respectively. Meanwhile, the simulation shows the temperature inside the cabin is reduced by as much as 4.2 °C in average, demonstrating that the proposed solar energy-powered cooling system is effective and feasible in cooling a hot vehicle cabin.
[en] A brief summary of data collection and the creation of an actinometric database necessary for estimation of the solar energy potential of the Republic of Uzbekistan is provided. The results of the processing of four-year data from six meteorological stations of the Republic are presented in a graph form.
[en] In recent years, coincidence spectroscopy of photo and Auger electrons helped to investigate the de-excitation of atoms, molecules and solids. These techniques are, for example, used at synchrotrons to analyze the emission of multiple electrons due to Auger processes that follow the excitation or ionization of inner-shell electrons. The total kinetic energy of the emitted electrons allows to obtain information about the spectrum and population of the final states, while the individual electron energies reveal details about the intermediate states, and therefore the decay pathways of an Auger cascade.
[en] In Newtonian fluid dynamics simulations in which composition has been tracked by a nuclear reaction network, energy generation due to composition changes has generally been handled as a separate source term in the energy equation. Here, a relativistic equation in conservative form for total fluid energy, obtained from the spacetime divergence of the stress-energy tensor, in principle encompasses such energy generation; but it is not explicitly manifest. An alternative relativistic energy equation in conservative form—in which the nuclear energy generation appears explicitly, and that reduces directly to the Newtonian internal+kinetic energy in the appropriate limit—emerges naturally and self-consistently from the difference of the equation for total fluid energy and the equation for baryon number conservation multiplied by the average baryon mass m, when m is expressed in terms of contributions from the nuclear species in the fluid, and allowed to be mutable.
[en] Highlights: • Power generation is scheduled with wind power uncertainty and dispatchable loads. • Objectives are: max social welfare, min emission, and max renewable production. • A multi-objective stochastic scheduling model is formulated and tested. • Scheduling outcomes under different policies are discussed. - Abstract: Some areas in China are facing pressing air pollution problems. Measures from the power sector can be taken to cope with air pollution issues, including reducing emission levels of thermal units and integrating wind and solar power. Social welfare, emission, and renewable integration are three major concerns in modern power system operations. This paper describes three stochastic scheduling models aiming at maximizing social welfare (SW), minimizing emission (EM) and maximizing renewable production (RE). A multi-objective scheduling model (MT) is also proposed that properly balances the above objectives. Wind power uncertainty and dispatchable loads are considered in the model. The outcomes of the three models are compared through an illustrative example and a 57-node case study. Results show that model EM results in 36% of the social welfare of model SW, 27% of its emissions, and 43% of its wind spillage, while model RE results in 55% of the social welfare of model SW, 56% of its emissions and 28% of its wind spillage. Additionally, we analyze how the optimal generation scheduling is affected by the weights in model MT. This work provides insight to policy makers on how to balance social welfare, emissions and renewable production.
[en] The approach to the mathematical modeling of technological processes of production, manufacture and consumption energyresources on the property fund facilities and engineering networks is presented. This approach is defining the information support system analysis of the kinetic changes of thermodynamic parameters sequentially occurring thermal processes in the flows of heat transfer agent in a closed structures of heating energy working in the recycle mode of the heat flow. It is determined the possibility of setting and solving problems of energyefficiency on the objects with close cycle operating and working in the fluctuation mode of the environmental parameters. (paper)
[en] Highlights: • The positive effect of sawdust biochar on in-situ tar H2O reforming is not proportional to biochar amount. • Change of oxygen-containing functional groups on biochar surface is mainly caused by the C-O. • During in-situ tar H2O reforming at 650–800 °C, for biochar, Eapp is 35.03 kJ/mol and kapp is 1.8 × 104 m3 kg−1h−1. • The sawdust biochar promotes the cracking of large ring polyaromatic tar compounds to form 1-ring aromatic tars. - Abstract: In order to fully understand the catalytic activities of sawdust biochar on in-situ tar steam reforming in mild catalysis temperatures (650–800 °C), the experiment was carried out in a two-stage fluidized bed/fixed bed reactor. The structural characteristics of biochar were analyzed by the Raman and XPS spectroscopies. The results of in-situ tar steam reforming over biochar were performed by gas chromatograph/mass spectrometer (GC/MS). Kinetic aspects of tar steam reforming in mild temperatures were calculated to evaluate the catalytic effect of sawdust biochar on in-situ tar reforming. The results indicate that sawdust biochar has a positive effect on in-situ tar steam reforming, while the effect is not proportional to biochar amount. During the in-situ tar steam reforming over biochar, the changes of oxygen-containing functional groups on biochar surface are mainly caused by the C-O bonds. The first order kinetic rate constant of sawdust biochar for the heterogeneous reforming of biomass tar at 650–800 °C is found to have an apparent activation energy (Eapp) of 35.03 kJ/mol with the apparent pre-exponential factor (kapp) of 1.8 × 104 m3 kg−1h−1. The biochar structures were considerably transformed during the tar steam reforming. According to GC/MS analysis of biomass tar, the biochar seems to promote the cracking of large ring polyaromatic tar compounds to form 1-ring aromatic ones.
PurposeIn this paper, we summarize the discussion and present the findings of an expert group effort under the umbrella of the United Nations Environment Programme (UNEP)/Society of Environmental Toxicology and Chemistry (SETAC) Life Cycle Initiative proposing natural resources as an Area of Protection (AoP) in Life Cycle Impact Assessment (LCIA).
MethodsAs a first step, natural resources have been defined for the LCA context with reference to the overall UNEP/SETAC Life Cycle Impact Assessment (LCIA) framework. Second, existing LCIA methods have been reviewed and discussed. The reviewed methods have been evaluated according to the considered type of natural resources and their underlying principles followed (use-to-availability ratios, backup technology approaches, or thermodynamic accounting methods).
Results and discussionThere is currently no single LCIA method available that addresses impacts for all natural resource categories, nor do existing methods and models addressing different natural resource categories do so in a consistent way across categories. Exceptions are exergy and solar energy-related methods, which cover the widest range of resource categories. However, these methods do not link exergy consumption to changes in availability or provisioning capacity of a specific natural resource (e.g., mineral, water, land etc.). So far, there is no agreement in the scientific community on the most relevant type of future resource indicators (depletion, increased energy use or cost due to resource extraction, etc.). To address this challenge, a framework based on the concept of stock/fund/flow resources is proposed to identify, across natural resource categories, whether depletion/dissipation (of stocks and funds) or competition (for flows) is the main relevant aspect.
ConclusionsAn LCIA method—or a set of methods—that consistently address all natural resource categories is needed in order to avoid burden shifting from the impact associated with one resource to the impact associated with another resource. This paper is an important basis for a step forward in the direction of consistently integrating the various natural resources as an Area of Protection into LCA.