Sugar alcohols have interesting thermodynamic properties that make them good options as heat storage materials (HSMs) to be used in solar cookers. Among sugar alcohols, xylitol is affected by severe supercooling that can significantly alter its usefulness in thermal energy storage (TES) systems. To overcome the supercooling issue, in this work the thermal behavior of a xylitol-based TES installed in a portable solar box cooker was investigated experimentally. The solar cooker has a 4.08 concentration ratio and the TES is a double-pot system filled with 2.5 kg of commercial-grade xylitol. The TES includes a manual mixing device that can be used to trigger the nucleation of xylitol. The effectiveness of the TES system with and without triggering was assessed through several outdoor tests, divided into heating and cooling phases, using silicone oil as absorbing media. It was found that the average load cooling time, in the temperature range of the test fluid from 110 to 80 °C, increased by about 346% when the solar cooker was equipped with the xylitol-triggered TES. The mixing device can therefore be considered an effective solution for regarding xylitol as an actual and performing phase change material.

Technologies that can contribute to the reduction of greenhouse gases are mandatory, and those based on solar energy are good candidates to achieve this. In this sense, massive solar thermal collectors are suitable technologies for supplying the primary energy demand of buildings. To design these devices, it is necessary to fully understand the physics of the problem before proposing any new optimized solution. This review aims to briefly summarize significant aspects regarding the current state of development of these solar technologies. Attention is paid to works devoted to experimental studies to analyze the behavior of these systems, as well as numerical models to predict the physics of the problem. Furthermore, the future directions and prospects in the field of massive collectors are briefly described. The main novelty of this review is to provide a comprehensive overview that summarizes the works done so far in the field over the past 30 years, which allows the reader to delve deeper into the topic. According to the reviewed works, it can be concluded that these technologies can contribute to the reduction of greenhouse gases while at the same time being excellent examples of the integration of solar energy devices with buildings.

In this study, a novel solar dryer is presented and analyzed experimentally and numerically. The proposed device is a small, passive, indirect solar dryer that works in an unconventional way. The product is mainly heated by irradiation from the walls of the drying chamber, while its moisture is removed by an airflow caused by natural convection. In addition, it is a low-cost solar dryer made of readily available materials and has a variable geometry that allows it to increase its thermal performance. Two types of experimental tests were conducted to analyze its performance. Thermal tests without load were carried out to assess the suitability of the drying chamber temperatures. Load tests with various masses and types of food were carried out to evaluate its drying performance. The results of the experimental tests demonstrated that the solar dryer achieved temperatures suitable for food drying and was able to dry the tested foods. Finally, a Computational Fluid Dynamics (CFD) model was developed to predict the performance of the proposed solar dryer. The validation of the numerical model with experimental data confirms their reliability in accurately predicting the temperatures within the dryer.