High-performance low-cost solar collectors for water treatment fabricated with recycled materials, open-source hardware and 3d-printing technologies.

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.

Optimization and parallelization of the discrete ordinate method for radiation transport simulation in OpenFOAM: Hierarchical combination of shared and distributed memory approaches.

This paper describes the reduction in memory and computational time for the simulation of complex radiation transport problems with the discrete ordinate method (DOM) model in the open-source computational fluid dynamics platform OpenFOAM. Finite volume models require storage of vector variables in each spatial cell; DOM introduces two additional discretizations, in direction and wavelength, making memory a limiting factor. Using specific classes for radiation sources data, changing the store of fluxes and other minor changes allowed a reduction of 75% in memory requirements. Besides, a hierarchical parallelization was developed, where each node of the standard parallelization uses several computing threads, allowing higher speed and scalability of the problem. This architecture, combined with optimization of some parts of the code, allowed a global speedup of x15. This relevant reduction in time and memory of radiation transport opens a new horizon of applications previously unaffordable.