Definition: Siloxanes are among the most technologically troublesome trace compounds present in biogas. As a result of their combustion, hard‐to‐remove sediments are formed, blocking biogas energy processing devices and reducing the efficiency of biogas plants. This entry can help to choose the optimal technology for the adsorptive removal of volatile methylsiloxanes (VMSs) from biogas and to identify adsorbents worth further development. Both the already implemented methods of adsorptive VMSs removal from landfill and sewage gases—e.g. using activated carbon and silica gel—and the ones being under development—e.g. using polymer resins—are presented, and their advantages and drawbacks are analyzed. The methods of obtaining adsorbents and the parameters of adsorption processes are discussed, and possible ways of regenerating spent adsorbents are evaluated. Especially promising adsorbents seem to be some zeolites—which can also be used for biogas desulfurization—and adsorbents based on polymer resins, as being particularly active towards VMSs and most amenable to multiple regeneration.

Abstract: Rechargeable alkali metal-air batteries have enormous potential in energy storage applications due to their high energy densities, low-cost and environment friendliness. Membrane separators determine the performance and economic viability of these batteries. Usually, porous membrane separators taken from lithium-based batteries are used. Moreover, composite and cation-exchange membranes have been tested. However, crossover of unwanted species (such as zincate ions in zinc-air flow batteries) and/or low hydroxide ions conductivity are major issues to be overcome. On the other hand, state-of-art Anion-Exchange Membranes (AEMs) have been applied to meet the current challenges with regard to rechargeable zinc-air batteries, which has received the most attention among alkali metal-air batteries. The recent advances and remaining challenges of AEMs for these batteries are critically discussed. Correlation between the properties of the AEMs and performance and cyclability of the batteries has been established.

Definition: Aerogel has entered the construction field in the last two decades as a component of many insulation products, due to its high thermal performance. Aerogel-based plasters allow the matching of high thermal performance and limited thickness. This makes them suitable when retrofitting an existing building and also when restoring a heritage building. This entry presents the state of the art of the research on aerogel-based plasters as a part of the aerogel-products for the building sector.

Definition: Because of the near-term risk of extreme weather events and other adverse consequences from climate change and, at least in the longer term, global fossil fuel depletion, there is worldwide interest in shifting to noncarbon energy sources, especially renewable energy (RE). Because of possible limitations on conventional renewable energy sources, researchers have looked for ways of overcoming these shortcomings by introducing radically new energy technologies. For wind energy, a possible alternative is airborne wind turbines.

Definition: All-solid-state batteries (SSBs) are one of the most fascinating next-generation energy storage systems that can provide improved energy density and safety for a wide range of applications from portable electronics to electric vehicles. The development of SSBs was accelerated by the discovery of new materials and the design of nanostructures. In particular, advances in the growth of thin-film battery materials facilitated the development of all solid-state thin-film batteries (SSTFBs)—expanding their applications to microelectronics such as flexible devices and implantable medical devices. However, critical challenges still remain, such as low ionic conductivity of solid electrolytes, interfacial instability and difficulty in controlling thin-film growth. In this review, we discuss the evolution of electrode and electrolyte materials for lithium-based batteries and their adoption in SSBs and SSTFBs. We highlight novel design strategies of bulk and thin-film materials to solve the issues in lithium-based batteries. We also focus on the important advances in thin-film electrodes, electrolytes and interfacial layers with the aim of providing insight into the future design of batteries. Furthermore, various thin-film fabrication techniques are also covered in this review.

Definition: Ammonia is the second-largest global chemical products, utilized as agricultural fertilizer, food production, industrial materials, refrigerants, and additives. Recently, the utilization of ammonia as the energy carrier (secondary energy source) has attracted many interests, due to its high volumetric hydrogen density, low storage pressure,high stability for long-term storage, high auto-ignition temperature,low condensation pressure, and lower gas density than air. in general,ammonia production includes the currently adopted thermochemical (Haber–Bosch), electrochemical, and photochemical cycle processes.

Definition: Anaerobic digestion is a well-known technology with wide application in the treatment of high-strength organic wastes. The oxidation of the organic material is carried out in the absences of oxygen by microorganisms leading to the release of biogas with methane and carbon dioxide being the main components. The microbial process also produces a slurry known as digestate. This stream contains recalcitrant compounds, complex polymeric substances and biomass residual material .

Definition: Asphaltenes is the heaviest and most polar fraction of petroleum not yet wery well characterized and only presently define by they solubility.

Definition: Bibliometric studies can also be applied to energy research topics, in particular, it is presented in this entry the analysis of the state of the art and publication trends on the topic of ISCC (Integrated Solar Combined Cycles) for the period covering 1990 to July 2020. The Web of Science (WOS) database was consulted, and 1277 publications from 3157 different authors and 1102 different institutions, distributed among 78 countries, were retrieved as the corpus of the study. The analysis performed in this entry concluded that the main publication source for ISCC research was Energy Conversion and Management, in terms of the total number of publications (158), but Solar Energy had the highest number of citations on the ISCC topic (4438). It was also found that China was the most productive country in terms of ISCC publications (241), and the Chinese Academy of Sciences was the most productive institution (52). Nevertheless, the author with the most publications on ISCC was I. Dincer, from Ontario Tech University (24). Based on publication keywords, a series of recommendations for future developments in the ISCC topic were derived, as well as the ways in which those ideas are connected to the global state of solar energy research.

Definition: CO2 methanation has recently emerged as a process that targets the reduction in anthropogenic CO2 emissions, via the conversion of CO2 captured from point and mobile sources, as well as H2 produced from renewables into CH4. Ni, among the early transition metals, as well as Ru and Rh, among the noble metals, have been known to be among the most active methanation catalysts, with Ni being favoured due to its low cost and high natural abundance. However, insufficient low-temperature activity, low dispersion and reducibility, as well as nanoparticle sintering are some of the main drawbacks when using Ni-based catalysts. Such problems can be partly overcome via the introduction of a second transition metal (e.g., Fe, Co) or a noble metal (e.g., Ru, Rh, Pt, Pd and Re) in Ni-based catalysts. Through Ni-M alloy formation, or the intricate synergy between two adjacent metallic phases, new high-performing and low-cost methanation catalysts can be obtained.