Energy production and storage have become key issues concerning our welfare in daily life. Present challenges for batteries are twofold. In the first place, the increasing demand for powering systems of portable electronic devices and zero-emission vehicles stimulates research towards high energy and high voltage systems. In the second place, low cost batteries are required in order to advance towards smart electric grids that integrate discontinuous energy flow from renewable sources, optimizing the performance of clean energy sources. Na-ion batteries can be the key for the second point, because of the huge availability of sodium, its low price and the similarity of both Li and Na insertion chemistries. In spite of the lower energy density and voltage of Na-ion based technologies, they can be focused on applications where the weight and footprint requirement is less drastic, such as electrical grid storage. Much work has to be done in the field of Na-ion in order to catch up with Li-ion technology. Cathodic and anodic materials must be optimized, and new electrolytes will be the key point for Na-ion success. This review will gather the up-to-date knowledge about Na-ion battery materials, with the aim of providing a wide view of the systems that have already been explored and a starting point for the new research on this battery technology.

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Sodium–sulfur (Na–S) battery technology has high potential for energy storage and load leveling in power systems, and it is one of the most developed types of high temperature battery. Owing to outstanding energy density, high efficiency of charge/discharge, low materials cost, and cycle life of up to 15 years, Na–S batteries are attractive for their use in relatively large‐scale energy storage system applications. However, there are several challenges to overcome for the safe operation of Na–S batteries, mostly related to the high operation temperatures. In this sense, the development of new solid electrolytes that possess high ionic conductivities at intermediate or room temperature is crucial. β‐Alumina and NASICON structure electrolytes are revised, and new alternatives, such as ceramic/polymer composites, are also gathered. There also exists novel focus on Na–S technology in order to increase the obtained capacity and cyclability consisting of using nanostructured carbon to host sulfur or to bind it to a polymer. In addition, hybrid technologies combining Na–S with ZEBRA or oxygen rocking‐chair batteries are currently arising as alternative storage devices. As Na–S technology was introduced in the mid‐1970s, a number of different patents have been developed. Trends observed in the new patents are twofold: on the one hand, they aim to integrate these batteries into the electrical grid in order to compensate the fluctuations of renewable energies; on the other hand, they show battery component improvements in order to obtain lower operating temperatures.

A sequential injection system to monitor glycerol in a Saccharomyces cerevisiae fermentation process was developed. The method relies on the rate of formation of nicotinamide adenine dinucleotide in its reduced form (NADH, measured spectrophotometrically at 340 nm) from the reaction of glycerol with NAD(+) cofactor, catalysed by the enzyme glycerol dehydrogenase present in solution. This procedure enables the determination of glycerol between 0.046 and 0.46 g/l, (corresponding to yeast fermentation samples with concentrations up to 50 g/l) with good repeatability (relative standard deviation for n = 10 lower than 2.2% for three different samples) at a sampling frequency of 25/h. The detection and quantification limits using a miniaturised spectrophotometer were 0.13 and 0.44 mM, respectively. Reagent consumption was of 0.45 mumol NAD(+) and 1.8 microg enzyme per assay, and the waste production was 2.8 ml per determination. Results obtained for samples were in agreement with those obtained with a high-performance liquid chromatography method.