Cooling techniques for PV panels: A review

Solar energy is considered one of the most dominant renewable energy sources. It can be used to produce electricity through PV panels. Unfortunatly, this technology is subject to limitations. High operating temperature exceeding 25°C, causes the PV panels to overheat, reducing their lifetime and efficiency. Various approaches to PV cooling are used to overcome these challenges.This paper presents a comprehensive overview of different cooling techniques to increase the performance of PV panels. Passive and active PV cooling systems are analysed using air, water, phase change materials (PCMs) and nanofluids as working agents. A review analysis showed that water cooling is better than air cooling. PCMs, which have recently been gaining in popularity, also deserve attention

The effect of the topmost layer and the type of bone morphogenetic protein-2 immobilization on the mesenchymal stem cell response

Recombinant human bone morphogenetic protein-2 (rhBMP-2) plays a key role in the stem cell response, not only via its influence on osteogenesis, but also on cellular adhesion, migration, and proliferation. However, when applied clinically, its supra-physiological levels cause many adverse effects. Therefore, there is a need to concomitantly retain the biological activity of BMP-2 and reduce its doses. Currently, the most promising strategies involve site-specific and site-directed immobilization of rhBMP-2. This work investigated the covalent and electrostatic binding of rhBMP-2 to ultrathin-multilayers with chondroitin sulfate (CS) or diazoresin (DR) as the topmost layer. Angle-resolved X-ray photoelectron spectroscopy was used to study the exposed chemical groups. The rhBMP-2 binding efficiency and protein state were studied with time-of-flight secondary ion mass spectrometry. Quartz crystal microbalance, atomic force microscopy, and enzyme-linked immunosorbent assay were used to analyze protein-substrate interactions. The effect of the topmost layer was tested on initial cell adhesion and short-term osteogenesis marker expression. The results show the highest expression of selected osteomarkers in cells cultured on the DR-ended layer, while the cellular flattening was rather poor compared to the CS-ended system. rhBMP-2 adhesion was observed only on negatively charged layers. Cell flattening became more prominent in the presence of the protein, even though the osteogenic gene expression decreased