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Solar-driven interfacial evaporation technologies for food, energy and water

Solar-driven interfacial evaporation technologies use solar energy to heat materials that drive water evaporation. These technologies are versatile and do not require electricity, which enables their potential application across the food, energy and water nexus. In this Review, we assess the potential of solar-driven interfacial evaporation technologies in food, energy and clean-water production, in wastewater treatment, and in resource recovery. Interfacial evaporation technologies can produce up to 5.3 l m–2 h−1 of drinking water using sunlight as the energy source. Systems designed for food production in coastal regions desalinate water to irrigate crops or wash contaminated soils. Technologies are being developed to simultaneously produce both clean energy and water through interfacial evaporation and have reached up to 204 W m–2 for electricity and 2.5 l m–2 h–1 for water in separate systems. Other solar evaporation approaches or combinations of approaches could potentially use the full solar spectrum to generate multiple products (such as water, food, electricity, heating or cooling, and/or fuels). In the future, solar evaporation technologies could aid in food, energy and water provision in low-resource or rural settings that lack reliable access to these essentials, but the systems must first undergo rigorous, scaled-up field testing to understand their performance, stability and competitiveness.

Advancing robust all-weather desalination: a critical review of emerging photothermal evaporators and hybrid systems

All-weather solar-driven desalination systems, integrating photothermal evaporators with hybrid technologies, present a sustainable, cost-effective, and high-efficiency strategy for freshwater production. Despite significant advancements, previous reviews have predominantly focused on daytime evaporation, neglecting the broader scope of all-weather seawater evaporation. This review provides a comprehensive examination of the current status of all-weather seawater evaporators and their hybrid systems. Initially, the review details the system’s composition and operating principles, as well as the design criteria for high-performance evaporators. It then goes over various common photothermal conversion materials for seawater desalination, with a particular emphasis on those materials tailored for all-weather applications. It also offers an in-depth overview to the developed photothermal hybrid systems for all-weather seawater evaporation, including their working principles, the efficiency of evaporation across the day-night cycle, and their practical applications. Lastly, the existing challenges and potential research opportunities are thoroughly discussed.

Unequal roles of cities in the intercity healthcare system

Cities are increasingly interdependent regarding healthcare provision and demand. However, the intercity healthcare system (IHS) behind the nationwide patient mobility remains insufficiently understood. Here, leveraging human mobility big data, we reveal cities’ roles in providing and demanding quality healthcare within the IHS of China. We find that 8% of Chinese cities are national and regional hubs that address the healthcare shortage of cities deprived of quality healthcare, while 63% of the cities that are unnoticed compensate for migrant workers being denied healthcare rights in megacities. The IHS generates new structural inequalities in healthcare access exhibiting a Matthew effect. The few cities (12%) that are already rich in healthcare resources benefit more and can strengthen their advantages in providing healthcare to local populations (32% of China’s total population). The many cities (35%), while facing healthcare shortages, are further disadvantaged in ensuring adequate healthcare for their local populations (26% of China’s total population).

The decreasing housing utilization efficiency in China’s cities

‘Ghost cities’ are a well-known phenomenon of (almost) complete vacancy of urban living space in China. Underutilization of urban living space, however, is far more common than complete vacancy. Here we propose the concept of housing utilization efficiency (HUE) and present the following findings: (1) the overall HUE in China’s highly urbanized areas decreased from 84% in 2010 to 78% in 2020, (2) the HUE in central, old urban areas was generally lower than that in the outer layers of urban areas and declined more from 2010 to 2020 and (3) four development types are found to represent different patterns of urban population movement, urban housing growth and HUE change at the intraurban level. These findings provide comprehensive insight into the discrepancies between urban housing supply and demand in China and highlight their connections to the country’s particular urbanization characteristics and policies, which are crucial for future housing development and planning.

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