Volume 5, Issue 1-6 - Special Issue: Chemical Energy Conversion. Status and Perspectives

MAXNET Energy is an initiative of the Max Planck society in which eight Max Planck institutes and two external partner institutions form a research consortium aiming at a deeper understanding of the electrocatalytic conversion of small molecules. We give an overview of the activities within the MAXNET Energy research consortium. The main focus of research is the electrocatalytic water splitting reaction with an emphasis on the anodic oxygen evolution reaction (OER). Activities span a broad range from creation of novel catalysts by means of chemical or material synthesis, characterization and analysis applying innovative electrochemical techniques, atomistic simulations of state-of-the-art x-ray spectroscopy up to model-based systems analysis of coupled reaction and transport mechanisms. Synergy between the partners in the consortium is generated by two modes of cooperation – one in which instrumentation, techniques and expertise are shared, and one in which common standard materials and test protocols are used jointly for optimal comparability of results and to direct further development. We outline the special structure of the research consortium, give an overview of its members and their expertise and review recent scientific achievements in materials science as well as chemical and physical analysis and techniques. Due to the extreme conditions a catalyst has to endure in the OER, a central requirement for a good oxygen evolution catalyst is not only its activity, but even more so its high stability. Hence, besides detailed degradation studies, a central feature of MAXNET Energy is a standardized test setup/protocol for catalyst stability, which we propose in this contribution.

The aim to develop active photocatalysts based on abundant elements for solar energy conversion reactions has sparked wide interest in manganese oxides as visible light-absorbing alternative to TiO 2 . Today, a multitude of different routes are available for the synthesis of MnO x species with specific stoichiometry, crystal structure, morphology, size or surface properties. Still, even for the bulk manganese oxides, some controversy remains, for example, with respect to the band gap, which hinders the targeted development of specific manganese oxide catalysts for photocatalysis. In classical heterogeneous catalysis and electrocatalysis, manganese oxides have been successfully used for a wide range of reactions, in particular in the field of (selective) oxidations. Photocatalytic applications have also been reported, but a true photocatalyst for the famous water-splitting reaction, deep insight into the prevailing mechanisms and an understanding of the involved processes has yet to be found. With this review, we aim to give a comprehensive overview over the structural, physical and catalytic properties of manganese oxides, together with an overview over suitable synthesis procedures. This will then serve as a basis for the discussion of the state of the art in the application of manganese oxides in catalysis and photocatalysis.

The role of chemical energy storage and solar fuels as key elements for the sustainable chemical and energy production is discussed in this concept paper. It is shown how chemical energy storage, with the development of drop-in carbon-based solar fuels, will play a central role in the future low-carbon economy, but it is necessary to consider its out-of-the-grid use, rather than being limited to be a tool for smart grids. Related aspects discussed are the possibility to: (i) enable a system of trading renewable energy on a world scale (out-of-the-grid), including the possibility to exploit actually unused remote resources, (ii) develop a solar-driven and low-carbon chemical production, which reduces the use of fossil fuels and (iii) create a distributed energy production, going beyond the actual limitations and dependence on the grid.

After a brief review of the conflicting statements made recently concerning the time it will take for the energy and chemical industries to prosper using only renewable sources, an account is given of three distinct new ways in which the current super-abundance of available CO 2 may be used as feedstock for important new reactions. In particular, attention is focused on the recent work (2015) of Sastre et al., Ozin et al. and Kanan et al.

Lubricants act as anti-friction media and facilitate smooth operations, maintain machine reliability and lead to reduction in the risk of frequent failures. Around the globe, petroleum-based reserves are depleting which results in price hike, creating concern about environmental pollution. The researchers are focusing on developing and using an eco-friendly lubricant derived from renewable resources. Non-edible vegetable oil-based bio-lubricants are eco-friendly due to their biodegradability, non-toxicity and net zero greenhouse gas emission. This study presents the potential of using non-edible vegetable-based bio-lubricants in the automotive sector. The first part of the study discusses about the resources, properties, as well as advantages and application of the bio-lubricants. In the second part of this paper, the potential of non-edible oil-based bio-lubricants as alternatives are discussed. The final part includes the description about the global lubricant market and prospects for the future. Non-edible vegetable oil-based bio-lubricants have enhanced lubricity, high viscosity, good anti-wear property, high viscosity index, increased equipment service life, high load carrying ability, low evaporation rates and low emission of metal traces into the atmosphere.

Wise utilization of today’s new solar energy technologies provides buildings with new aesthetic value which is no longer in conflict with efficiency in solar energy conversion. We outline the criteria for incorporating solar photovoltaic (PV) and solar thermal (ST) technologies in the building design in Sicily’s built environment. Better education in solar energy and in solar architecture of architects and civil engineers, as well as better communication efforts of solar energy companies, will be instrumental to afford the long-awaited local and global boom in the adoption of building-integrated PVs.

Provided that LED street lighting is guided by quality principles, outdoor illumination using light-emitting diodes will have a significant global impact helping to reduce carbon dioxide emissions, save relevant amounts of electricity and enhance the quality of life in cities as well as in remote areas. This study summarizes recent findings providing guidelines for further progress in this crucially important technology on the common pathway to sustainable development.

This paper estimates the monthly, seasonal and yearly optimal tilt angles that maximize solar irradiation received on an inclined surface, thus enhancing the energy harvested. The uncertainties in global and diffuse radiations on the horizontal surface are accounted using stochastic analysis of their daily statistical measured data. The measured data is taken over a seven-year time span. The study is carried out for south-facing flat plate solar collectors at the Bangkok site, Thailand, situated in the northern hemisphere. The position of the sun at any time and location is predicted by the mathematical procedure of Julian dating. Further, four isotropic and anisotropic sky models are used to evaluate the ratio of diffuse solar radiation on an inclined surface to that on a horizontal surface. The best sky model is opted by using the ranking method of errors and is used for further analysis. Moreover, the frequency distributions of global and diffuse radiations are studied using four types of probability density functions (PDFs), viz., Weibull, lognormal, gamma and beta. Kolmogorov–Smirnov (K-S) test is used as a criterion to find the best fit among the aforementioned PDFs. The proposed optimization problem is solved using particle swarm optimization with time-varying acceleration coefficients (PSO-TVAC). The monthly tilt angles obtained are found to be varying with respect to the corresponding latitude angle, suggested by the thumb rule. The collected energy using this tilt angle over a period of one year is found to be 588MJ/m2$588 \,{\rm{MJ/}}{{\rm{m}}^2}$ in excess to that harvested using the latitude angle.