Biochar obtained from sewage sludges are adopted for biogas cleaning. Sewage sludges are treated considering temperature, dwell time, activating agent, heating, and flow rate. The best performances achieved are registered considering the char produced at 400 °C using CO₂ as an activating agent with a dwell time of 2 h. The adsorption capacity for the biogas cleaning CH₄/CO₂/H₂S (20 ppm(v)) increased from 1.3 mg/g to 5.9 mg/g with the bed height. Future research with chemical activation processes will be made to improve the adsorption capacity achieved to produce cheaper sorbents than commercial ones.

Summary: Latent heat thermal energy storages (LHTES) are a promising technology with a wide range of applications in the framework of energy efficiency improvement. Phase change materials provide a big storage capacity, but their thermal conductivities are always extremely low. The use of finned tube heat exchangers is nowadays the best solution to enhance PCMs thermal performances. This allows significant charging and discharging rates. The major challenge concerns the balance between thermal performances and high material costs. A proper design of the heat transfer surfaces is essential to limit the system overall cost. Two different heat exchangers solutions, with radial and longitudinal fins are here examined. The design of the LHTES is performed by deploying a simplified FEM numerical model specifically developed for the application. A validation procedure based on laboratory tests with a small LHTES prototype was also carried out. The obtained results confirmed the reliability of the numerical model and justify its adoption as a tool for the design phase. The FEM model allows to effectively simulate the system thermal behaviour and assess the impact of the different HEX geometrical parameters on thermal performances. Based on this information it was possible to perform the optimization of the heat transfer surfaces and to derive the best heat exchanger layout in terms of material usage. The results showed that the solution with longitudinal fins is the most efficient, with 215 kg of steel less required for the realization of the finned heat exchanger.

With reference to the province of Novara in northwest Italy, this study aims to raise awareness about the environmental benefits that can derive from the use of alternative rice straw management practices to those currently in use, also highlighting how the use of these straws for energy purposes can be a valid alternative to the use of non-renewable resources. Using the LCA (Life Cycle Assessment) method, the two rice straw management practices currently in place (open field combustion and straw incorporation) were compared with an alternative strategy consisting in their collection and removal. The results show that removal of straw allows reducing the emissions of pollutants significantly: about one-hundredth of the PM (Particulate Matter) formation compared to the open-field burning and about one-tenth of the ozone depletion (CFCs, HCFCs, halons, etc.) compared to both the other two practices. Moreover, the LCA results show how the use of rice straw to produce energy as an alternative to conventional fuels helps to reduce the global warming potential of rice cultivation.

The current energy transition highlights the importance not only of energy production, but also of its efficient storage, for which lithium-ion batteries are currently the leading technology. In many applications, these devices operate outdoors at temperatures below 0 °C, and consequently, their performance is reduced due to the lower mobility of the ions. With the aim of evaluating this decrease in performance, measurements were carried out on a commercial LiFePO₄ module in the temperature range −20–+55 °C. The results show that the battery capacity decreases by 15% compared to the value measured at room temperature when the operating temperature drops to approximately −10 °C, and by 35% at approximately −20 °C. The paper also introduces a modified version of the Arrhenius kinetic model that allows for the analytical evaluation of the change in battery capacity as a function of temperature. The modified model proposes a quadratic dependence of the activation energy on the temperature through a temperature coefficient that for the two tested modules is equal to 8.0 × 10⁻⁵ eV/K² and 6.7 × 10⁻⁵ eV/K², respectively.

Current rice straw disposal practices have serious repercussions on the environment and, in addition, do not consider its energy potential. On the contrary, the anaerobic digestion of rice straw makes it possible to produce renewable energy and to reintroduce into the soil the nutrients present in the digestate, at the same time, reducing greenhouse gas emissions from paddies. For rice straw of different geographical origin, by applying a mass balance method to the digester, the minimum requirements in terms of conditioners (nitrogen, phosphorus and potassium) and water, which allow obtaining the maximum production of methane, were calculated. The results obtained show that after the first 30 days (hydraulic retention time) for each ton of rice straw digested, the daily water consumption varies considerably from one country to another, from a minimum value of 1.5 m³/d to a maximum of 4.3 m³/d. After the same time, the addition of nitrogen and phosphorus is only required for the optimal anaerobic digestion of Indian rice straw. The low presence of these elements in Indian straw requires an addition of 3 kg/d of urea and 1.5 kg/d of superphosphate to compensate for the lack of nitrogen and phosphorus, respectively. In all the examined cases, the concentration of potassium, even if higher than the optimal value, does not reach levels that can significantly affect the methane production.

The significant changes resulting from the ongoing energy transition highlight the importance of energy sources and vectors. Among the latter, the electron is certainly the most important, therefore its efficient storage is a fundamental task. In this regard, lithium-ion batteries are currently the leading technology. In many applications these devices operate outdoors at temperatures below 0°C showing reduced performance due to lower ionic mobility. In recent years, several researchers have experimentally reproduced these operating conditions, looking for solutions that guarantee the maintenance of the desired performance. Based on this approach, an experimental set up was created to study these effects on commercial devices consisting of a single cell. The paper presents a preliminary investigation of a commercial LiFePO4 module with nominal voltage of 3.2 V and capacity of 23 Ah. For this module, in the temperature range -20 ÷ +55 °C, the open circuit voltage and the internal resistance were experimentally determined, both in the charging and discharging phases. Furthermore, in the temperature range between -20 °C and +10 °C, the improvements in performance resulting from the application of localized electric heating to the above-mentioned cell were evaluated.