COVID 19 lockdown forced a general move of teaching activities from their on-site mode to remote producing different negative consequences for students. In this work, the use of Kahoot! platform was studied to keep students’ interest during online teaching. For this, Kahoot! games were carried out for the different topics of a university subject. The data analysis revealed that a high participation implies an improvement in the final marks. Additionally, questions response time was also extracted serving as a reference for remote exams. On the other hand, two surveys were carried out in which the students showed that the transfer from face-to-face to remote teaching had produced a general decrease in interest that can be mitigated by performing Kahoot! games.

Solar technologies constitute an excellent alternative for water treatment in low-income countries where the poverty of a large part of the population hinders their access to safe water. From a technical point of view, the use of compound parabolic collectors (CPC) has been consolidated in the last decades. However, the relatively high cost of tooling conventional manufacturing processes for these collectors makes them difficult to afford in the most impoverished regions. This work presents the development of low-cost CPC and parabolic through solar collectors (PTC) by 3D printing of the structure and the use of recycled reflective materials. Besides, open-source hardware has been used to control system operation, including a supplementary UV LED system to compensate for the operation under low solar irradiance. Regarding the tested reflective materials, an optimum is obtained using an aluminium adhesive sheet that leads to an efficiency of 80% compared to a commercial CPC made of high-quality anodised aluminium, being the cost 20 times lower. On the other hand, incorporating a low-cost solar tracking system in a printed PTC reactor could lead to efficiencies up to 300% compared to the commercial CPC, while the cost was 4.5 times lower. Finally, the LED compensation system was successfully validated, allowing the operation with a constant treatment capacity during operation in cloudy conditions. In conclusion, the developed collectors are high-performance solar water treatment systems with a significantly lower investment cost, making them affordable worldwide.