A Novel Idea for Improving the Efficiency of Green Walls in Urban Environment (an Innovative Design and Technique)

Sorption-Based Atmospheric Water Harvesting: Materials, Components, Systems, and Applications

Freshwater scarcity is a global challenge posing threats to the lives and daily activities of humankind such that two-thirds of the global population currently experience water shortages. Atmospheric water, irrespective of geographical location, is considered as an alternative water source. Sorption-based atmospheric water harvesting (SAWH) has recently emerged as an efficient strategy for decentralized water production. SAWH thus opens up a self-sustaining source of freshwater that can potentially support the global population for various applications. In this review, the state-of-the-art of SAWH, considering its operation principle, thermodynamic analysis, energy assessment, materials, components, different designs, productivity improvement, scale-up, and application for drinking water, is first extensively explored. Thereafter, the practical integration and potential application of SAWH, beyond drinking water, for wide range of utilities in agriculture, fuel/electricity production, thermal management in building services, electronic devices, and textile are comprehensively discussed. The various strategies to reduce human reliance on natural water resources by integrating SAWH into existing technologies, particularly in underdeveloped countries, in order to satisfy the interconnected needs for food, energy, and water are also examined. This study further highlights the urgent need and future research directions to intensify the design and development of hybrid-SAWH systems for sustainability and diverse applications.

Improving the Efficiency of Green Roofs Using Atmospheric Water Harvesting Systems (An Innovative Design)

Conventional green roofs, although having numerous advantages, could place water resources under pressure in dry periods due to irrigation requirements. Moreover, the thermal efficiency of green roofs could decrease without irrigation, and the plants could get damaged. Therefore, this study aims to improve the efficiency of conventional green roofs by proposing a new multipurpose green roof combined with fog and dew harvesting systems. The analysis determined that the average water use of green roofs in the summer (in humid regions) is about 3.7 L/m2/day, in the Mediterranean regions about 4.5 L/m2/day, and in arid regions about 2.7 L/m2/day. During the dry season, the average fog potential in humid regions is 1.2 to 15.6 L/m2/day, Mediterranean regions between 1.6 and 4.6 L/m2/day, and arid regions between 1.8 and 11.8 L/m2/day. The average dew potential during the dry season in humid regions is 0.1 to 0.3 L/m2/day, in the Mediterranean regions is 0.2 to 0.3 L/m2/day, and in the arid regions is 0.5 to 0.7 L/m2/day. The analysis of the suggested multipurpose green roof combined with fog/dew harvesting systems, in the summer, in three different climates, show that fog harvesting could provide the total water requirement of the green roofs, and that dew harvesting by PV (photo-voltaic) panels could provide 15 to 26% of the water requirements. Moreover, it could show a higher thermal impact on the building, higher efficiency in stormwater management, less dependence on the urban water network, and greater efficiency in decreasing urban air, water, and noise pollution. Finally, the novel green roof system could consume less water due to the shaded area by mesh and solar PVs and maximize the utilization of the roof area, as solar panels could be applied on the same green roof.

Efficiency Improvement of Photovoltaic Modules via Back Surface Cooling

Crystalline silicon photovoltaics are a cardinal and well-consolidated technology for the achievement of energy efficiency goals, being installed worldwide for the production of clean electrical energy. However, their performance is strongly penalized by the thermal drift, mostly in periods of high solar radiation where solar cells reach considerably high temperatures. To limit this aspect, the employment of cooling systems appears a promising and viable solution. For this purpose, four different cooling systems, working on the photovoltaic (PV) panel back surface, were proposed and investigated in an experimental set-up located at the University of Calabria (Italy). Hourly electrical output power and efficiency were provided accounting for different meteorological conditions in several months of the experimental campaign. The results demonstrated that a simple spray cooling technique can provide an absolute increment of electrical efficiency of up to 1.6% and an average percentage increment of daily energy of up to 8% in hot months. More complex systems, based on ventilation or combining spray cooling and ventilation, were demonstrated not to be a viable option for PV performance improvement.