## 2 Special Issue Findings
The results showed that parabolic trough collectors combined with H\({}_{2}\)O-LiBr provided lower design aspects and minimum rates of hourly costs (5.2 USD/h), followed by evacuated tube collectors with H\({}_{2}\)O-LiBr (5.6 USD/h). Furthermore, it was found that H\({}_{2}\)O-LiBr provided a lower thermo-economic product cost (0.14 USD/GJ) compared with NH\({}_{3}\)-H\({}_{2}\)O (0.16 USD/GJ). The thermal ratio (absorption refrigeration cycle coefficient of performance) was between 0.5 and 0.9. 4. The authors of the fourth article ([PERSON]; [PERSON]; and [PERSON], from the Technical University of Darmstadt, Germany, and Can Tho University, Vietnam) developed an Aspen plus model for steam gasification of biomass to investigate the influence of operating parameters on the gasification process under steady-state conditions [6]. To consider the hydrodynamic, reaction kinetic decomposition of biomass and pyrolysis yield distribution, external FORTRAN codes were written and implemented in the developed model. The numerical results were compared with the measurement obtained from a 5 kW\({}_{\text{th}}\) bubbling fluidised bed test rig, showing good agreement. A slight discrepancy between the simulation model and the measured data was observed, which is due to the limitations of the model, i.e., simplified calculations of the hydrodynamics and kinetics of the bed and the absence of tar decomposition reactions. The authors claimed that the gasification process is favoured at higher temperatures. Under such conditions, hydrogen production and carbon conversion efficiency increased, while the percentage of carbon monoxide and methane in the product gas decreased. Increasing the amount of steam in the reactor promoted biomass gasification performance. The ratio of steam to biomass increased the content and yield of hydrogen in the product gas and significantly improved the gas yield and carbon conversion efficiency. 5. The fifth contribution included in this Special Issue is by [PERSON]; [PERSON] [PERSON]; and [PERSON], from the University of L'Aquila, Italy [7]. This study investigated the chemical looping gasification of wheat straw pellets as part of the European research project entitled Chemical Looping Gasification for Sustainable Production of Biofuels (CLARA; G.A. 817841 [8]). The focus was on wheat straw pellet pre-treatment, i.e., torrefaction and torrefaction-washing. After pre-treatment, the devolatilisation of individual pellets was carried out in a laboratory-scale fluidised bed of sand at 700, 800, and 900 \({}^{\circ}\)C to both quantify and analyse the product gas released from differently pre-treated types of biomass. The experimental data were evaluated using integral average parameters such as gas yield (H\({}_{2}\)/CO mole ratio) and carbon conversion. For all biomasses, increasing the devolatilisation temperature between 700 and 900 \({}^{\circ}\)C improved the thermochemical conversion in terms of gas yield, carbon conversion, and H\({}_{2}\)/CO mole ratio in the product gas. As for the pre-treatments, the main evidence was observed in the overall improvement in product gas quality (i.e., composition) and quantity compared with the untreated pellets. Negligible differences were observed between the different pre-treatments, mainly owing to the peak quantities that showed an improvement in the H\({}_{2}\)/CO mole ratio in correlation with the increase in torrefraction temperature from 250 to 270 \({}^{\circ}\)C.
* 6. The authors of the sixth article published by [PERSON]; [PERSON]; [PERSON]; [PERSON]; and [PERSON], from the Technical University of Darmstadt, Germany, and the University of Technology, Iraq, developed a dynamic process simulation model to improve the efficiency of parabolic trough power plants and their associated control structures [9]. The model was created using advanced process simulation software (APROS) [10] and validated against an existing Andasol II solar power plant in Spain.