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Thermal energy storage includes sensible, latent and thermochemical heat storage. The latter is particularly interesting because the heat is stored as a chemical potential, which reduces heat loss in long-term applications. The viability of thermochemical storage systems strongly depends on the energy density of the storage material. The development of high energy density materials is thus essential to achieve compact systems suitable for a wide range of applications. A new sol-gel composite material is investigated here: it is composed of CaCl2 dispersed within a matrix of silica and PEG-600 polymer. Composite materials containing CaCl2 have the highest storage capacities and seem to be the most promising candidates. The aim is to develop a composite that is both efficient and stable. The suitability of the material depends on the ability of the PEG to stabilise calcium chloride and prevent its deliquescence and leakage. The experimental results are compared to those obtained using zeolite 13X, which is a reference adsorbent material.

Background and gaps. The topic of indoor air quality (IAQ) in low-energy buildings has received increasing interest over the past few years. Often based on two measurement points and on passive measurements over one week, IAQ studies are struggling to allow the calculation of pollutants exposure. Objectives. We would like to improve the evaluation of the health impacts, through measurements able to estimate the exposure of the occupants. Methodology. This article presents detailed IAQ measurements taken in an energy-efficient occupied house in France. Two campaigns were conducted in winter and spring. Total volatile organic compounds (TVOC), formaldehyde, the particle numbers and PM2.5, carbon dioxide (CO2), relative humidity (RH), temperature (T), ventilation airflows, and weather conditions were dynamically measured in several points. Laboratory and low-cost devices were used, and an inter-comparison was carried out for them. A survey was conducted to record all the daily activities of the inhabitants. IAQ performance indicators based on the different pollutants were calculated. Results. PM2.5 cumulative exposure did not exceed the threshold available in the literature. Formaldehyde concentrations were high, in the kitchen, where the average concentrations exceeded the threshold. However, the formaldehyde cumulative exposure of the occupants did not exceed the threshold. TVOC concentrations were found to reach the threshold. With these measurements performed with high spatial and temporal discretization, we showed that such detailed data allow for a better-quality health impacts assessment and for a better understanding of the transport of pollutants between rooms. [ABSTRACT FROM AUTHOR]

The potential of co-digestion mixing thickened secondary sludge (TS) from extended aeration wastewater treatment plant and locally available substrates (whey, grease and septage) has been studied in this work, using three steps. The first step was a batch test to determine the biological methane potential (BMP) of different mixtures of the three co-substrates with TS. The second step was carried out with lab-scale reactors (20 L), simulating anaerobic continuous stirred tank reactors, fed by three mixtures of co-substrates that were determined according to the previous step results. Modeling was applied in the third step, using ADM1 as a mechanistic model to help understand the co-digestion process. According to the BMP step, septage used as a co-substrate has a negative effect on performance, and the addition of 10–30% grease or whey would lead to a gain of around 60–70% in the production of methane. The results from the reactor tests did not validate the positive effects observed with the BMP assay but confirmed good biodegradation efficiency (> 85%). The main purpose of co-digestion in this scenario is to recover energy from waste and effluents that would require even more energy for their treatment. The protein and lipid percentages of particulate biodegradable COD are important variables for digester stability and methane production, as predicted by modeling. The results of simulations with the ADM1 model, adapted to co-digestion, confirmed that this model is a powerful tool to optimize the process of biogas production. [ABSTRACT FROM AUTHOR]

Abstract Processes based on non-thermal plasma (NTP) for indoor air treatment inevitably lead to the formation of toxic by-products such as ozone (O 3) and nitrogen oxides (NO x). Adding a step of heterogeneous catalysis in series with NTP could allow for the decomposition of the by-products. Therefore, different catalysts were developed based on transition metal oxides, such as NiO x , CoO x and MnO x with different weight percentage 1, 5 and 10 wt.%, deposited on a γ-Al 2 O 3 support. The O 3 removal efficiency (ORE) and the NO x removal efficiency (NRE) were very encouraging in dry air: about 65% and 80%, respectively, by using 2 g 5 wt.% MnO x /Al 2 O 3 catalyst under the experimental conditions. However, strongly negative effects of relative humidity (RH) on the catalytic decomposition performance were observed. To overcome this limitation, the catalyst surface was modified to make it hydrophobic using a cost-effective chemical grafting method. This treatment consisted in impregnating the 5 wt.% MnO x /Al 2 O 3 catalyst with different trichloro(alkyl)silanes (TCAS). The effects of different linker lengths and amounts of TCAS for the hydrophobicity and the decomposition performance of surface-modified catalysts under humid conditions were investigated. Our results show that the surface-modified catalyst with the shortest linker and 0.25 mmol/g cat of modifying agent represents the best catalytic decomposition performance for O 3. Its ORE is 41% at 60% RH, which is twice that of the non-modified catalyst. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The use of non-thermal plasma, corona discharge, was studied for indoor air applications. Toluene at a very low to moderate concentration (a few ppbv–1000 ppbv) was used as the target compound. Both degradation of toluene and generation of by-products (intermediates and ozone) were investigated. Because of the very low concentrations implemented in this study, high levels of removal efficiency were reached with very low specific density (a few J L −1 ). It was found that the polarity of the discharge was the parameter having the greatest influence: at 8.2 ppbv, removal efficiency could reach 98.2% under negative polarity while only 62% removal efficiency was achieved under positive polarity. This result is consistent with the lower ozone concentration in positive polarity and hence the lower plasma reactivity. The relative humidity of the air is another highly important parameter. It was found that the number of intermediates detected at the outlet of the plasma and removal efficiency both increased when increasing the relative humidity from less than 2%–40%. At higher relative humidity, toluene removal efficiency remained on the same order of magnitude (close to 80%), while the number and the amount of intermediates decreased. A higher oxidative rate was expected. [ABSTRACT FROM AUTHOR]

New types of Cu-doped spherical-shaped activated carbons were prepared by pyrolysis at 700 °C of chitosan hydrogels impregnated with KOH at ratios (m KOH /m chitosan) ranging from 22.5% to 135%. At KOH impregnation ratio lower than 63%, the precursor Cu doping allowed obtaining bead-shaped activated carbons (diameter ~ 2 mm) and the highest specific surface areas (1145 m2 g−1). The absence of copper doping yielded to activated carbon powders whatever the KOH impregnation ratio. As increasing the impregnation ratio higher than 63%, the materials porosity type turns from exclusively microporous to both microporous and mesoporous. The microporous volume, determined by N 2 adsorption at 77 K and CO 2 adsorption at 273 K, attains a maximum (about 0.5 cm3 g−1) for a 63% impregnation ratio. Scanning Electron Microscopy (SEM) images show a multi-scale porosity for a KOH impregnation ratio higher than 45%. Nanoparticles of Cu and CuO were identified by SEM and Transmission Electron Microscopy in the ACs beads prepared from copper-doped chitosan. Whatever the composition, the beads are formed of N-enriched carbons showing mainly pyridinic and pyrrolic groups evidenced by XPS. [Display omitted] • Activation at 700 °C of KOH impregnated chitosan hydrogels beads. • Preparation of new types of Cu-doped spherical-shaped activated carbons. • KOH impregnation ratio of 63% optimised to obtain the highest micro-mesopore volume. • Presence of Cu/CuO nanoparticles observed by electron microcopy methods. • N-enriched carbons showing mainly pyridinic and pyrrolic groups evidenced by XPS. [ABSTRACT FROM AUTHOR]