The need for large-scale energy storage in the context of renewable electricity production worldwide is evident. Among the various energy storage methods, thermal energy storage stands out. It is independent of geographical location, allows high storage capacities, does not require scarce materials, and is cheaper than its direct competitors. Currently, several technologies are being intensively developed. In some of them, packed-bed systems play a central role: a heat transfer fluid heats up or releases heat from a porous solid that acts as a thermal energy reservoir. This work compiles their application to concepts such as concentrated solar power, pumped thermal energy storage, and compressed or liquid air energy storage. Different physical models with diverse refinement degrees and the corresponding computational schemes are comprehensively presented. Comparison with previous experimental works includes gas or liquid heat transfer fluids, sensible or latent heat transfers, and a wide range of temperature levels. It is shown that the continuous 1D solid phase model solved with an implicit Euler method provides satisfactory results with a reasonable computing time for various systems. The influence of time step and spatial mesh is surveyed, as well as that of pressure drops. Efficiencies and stored energies are calculated for some particular cases, and sensitivity analysis is presented, including parameters such as fluid velocity in discharge and storage time. Concerning the latter, discharge efficiencies for long-time storage (between 10 and 15 h) are fairly good, between 0.39 and 0.20.

Parabolic dish collectors (PDCs) focus solar radiation onto a small area, minimizing the heat-loss area of the solar receiver and improving the heating of the working fluid. This fluid usually drives a Stirling-like or micro-gas turbine (Brayton-like) power generator. PDCs, initially intended for small-capacity applications, are well-suited for electricity and heat generation in remote rural areas, working alone and/or as parabolic dish arrays. PDCs have received considerable attention among solar thermal collectors due to their high concentration ratios and the high temperatures they achieve. However, nowadays, they are the least developed and least commissioned among concentrated solar power configurations, lacking a well-established technology. This review aims to compile the evolution of research on PDCs over recent years from a global perspective and is mainly focused on the subsystems constituting a PDC plant, their integration, and overall system optimisation, thereby addressing a gap in the current literature. Methodological tools used in the field are comprehensively revised, and recent related projects are summarized. Some innovative and promising applications are also highlighted.

In celebration of 50 years of the endoreversible Carnot-like heat engine, this work aims to link the thermodynamic success of the irreversible Carnot-like heat engine with the stability dynamics of the engine. This region of success is defined by two extreme configurations in the interaction between heat reservoirs and the working fluid. The first corresponds to a fully reversible limit, and the second one is the fully dissipative limit; in between both limits, the heat exchange between reservoirs and working fluid produces irreversibilities and entropy generation. The distance between these two extremal configurations is minimized, independently of the chosen metric, in the state where the efficiency is half the Carnot efficiency. This boundary encloses the region where irreversibilities dominate or the reversible behavior dominates (region of success). A general stability dynamics is proposed based on the endoreversible nature of the model and the operation parameter in charge of defining the operation regime. For this purpose, the maximum ecological and maximum Omega regimes are considered. The results show that for single perturbations, the dynamics rapidly directs the system towards the success region, and under random perturbations producing stochastic trajectories, the system remains always in this region. The results are contrasted with the case in which no restitution dynamics exist. It is shown that stability allows the system to depart from the original steady state to other states that enhance the system’s performance, which could favor the evolution and specialization of systems in nature and in artificial devices.