Solar energy for clean water and beyond
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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.
On-chip solar power source for self-powered smart microsensors in bulk CMOS process
Enhancing the photoelectric conversion efficiency of on-chip solar cells is crucial for advancing solar energy harvesting in self-powered smart microsensors for Internet of Things applications. Here we show that adopting a center electrode (CE) layout instead of a ring electrode (RE) effectively reduces the shadowing effect of surface electrodes. Using a standard 0.18 μm CMOS process, we fabricated a 0.01 mm² segmented triple-well on-chip solar cell with CEs and highly doped interconnections. Measurements demonstrate a photoelectric conversion efficiency of 25.79% under solar simulator illumination, a 17.49% improvement over conventional designs. This on-chip solar cell is used for on-chip energy harvesting, achieving a maximum end-to-end conversion efficiency of 10.20%, referring to the overall efficiency from incident light power to load power output. The proposed energy harvesting system reliably provides a stable 1 V output to the load, even under varying illumination and load conditions.
Greenhouse gases reduce the satellite carrying capacity of low Earth orbit
Anthropogenic contributions of greenhouse gases in Earth’s atmosphere have been observed to cause cooling and contraction in the thermosphere, which is projected to continue for many decades. This contraction results in a secular reduction in atmospheric mass density where most satellites operate in low Earth orbit. Decreasing density reduces drag on debris objects and extends their lifetime in orbit, posing a persistent collision hazard to other satellites and risking the cascading generation of more debris. This work uses projected CO2 emissions from the shared socio-economic pathways to investigate the impact of greenhouse gas emissions on the satellite carrying capacity of low Earth orbit. The instantaneous Kessler capacity is introduced to compute the maximum number and optimal distribution of characteristic satellites that keep debris populations in stable equilibrium. Modelled CO2 emissions scenarios from years 2000–2100 indicate a potential 50–66% reduction in satellite carrying capacity between the altitudes of 200 and 1,000 km. Considering the recent, rapid expansion in the number of satellites in low Earth orbit, understanding environmental variability and its impact on sustainable operations is necessary to prevent over-exploitation of the region.
Impact of green bonds on CO2 emissions and disaggregated level renewable electricity in China and the United States of America
Green financial products have emerged that can benefit economic actors in financing green initiatives to promote renewable energy and enable carbon neutrality. Against this backdrop, the study examines the impact of green bonds (GBs) on carbon dioxide (CO2) emissions and renewable electricity generation (EG) in China and the USA, the leading countries in terms of GB issuance and CO2 emissions. To this end, the study conducts a disaggregated-level analysis by applying novel nonlinear quantile methods between January 2, 2019, and July 31, 2023. The results demonstrate that at higher quantiles; (i) GBs mainly have a dampening impact on CO2 emissions from the transportation sector in China and the USA; (ii) GBs have a stimulating impact on solar and wind EG in China; (iii) GBs have a diminishing impact on all types of EGs in the USA. Thus, GBs have an impact on carbon neutrality and renewable energy, which differs by quantiles, sectors, and EG sources. Accordingly, various policy implications are discussed in terms of further contributions of GBs to carbon neutrality and renewable energy in China and the USA.
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