水伏科学与技术的召唤

水覆盖了约71%的地球表面,占人体重量约70%,在细胞里的含量可达80%。水与能量相生,维持着大至地球系统的能量循环,小至生物体的温度平衡,是天然的吸能器、储能器、换能器和传能器。水吸收了太阳辐射到达地表能量的近70%,在地球上动态吸纳释放能量的年平均功率高达60万亿千瓦(1015 瓦),比全人类目前年平均能量消耗功率高3个数量级。水以热能、动能的形式存储所吸收的热量,更以蒸发、凝结、形云布雨、兴风作浪的形式,把存储的太阳能转化成机械能等多种形式的能量。更为重要的是,水在热处将太阳能吸收,经过蒸发、对流等过程在冷处凝结释放,再经沉降、径流而成川入海,无时无刻不在转移着巨大的能量。水因其能量过程主导全球气候变化,让地球成为生命的家园,如《道德经》云“上善若水,几近于道”。

从水的储能和换能过程中提取对人类有用的能量一直是人们的追求。人类利用水能的历史可追溯到春秋时期的水车或更早,随着电磁学诞生发展了水电技术。然而,传统技术主要利用水流的动能产生有用的机械能,并间接发电。纳米材料具有显著的量子效应和表面效应,可与各种形式的水发生耦合而输出显著的电信号,如石墨烯可通过双电层的边界运动将拖动和下落水滴的能量直接转化为电能(拖曳势)、也可将海水波动能转化为电能(波动势)。更具里程碑意义的发现是,廉价的碳黑等纳米结构材料可通过大气环境下无所不在的水的自然蒸发,持续产生伏级的电能。我们将这类直接转化水能为电能的现象称为“水伏效应”(hydrovoltaic effect)。水伏效应为全链条式捕获地球水循环的水能开辟了全新的方向,提升了水能利用能力。

水伏效应的理论与技术研究目前还处于萌芽期,但其发展势头、巨大潜力和应用前景,足以引起各学科领域的高度关注和大力探索。当前广泛研究的可再生能源,如太阳能、风能,其捕获不仅受时间、地域限制,而且需要晶体硅等光吸收能力好的半导体或特殊有机物等特种材料,其存储、并网更给相关储能技术提出了巨大挑战,而风能和太阳能本身的不稳定性也制约着产业的发展。与之相比,水蒸发无处不在,不受天气、时空的影响,而且可结合风能、太阳能、废热等显著提高蒸发发电量,使得蒸发能利用在理论上具有比光伏技术更大的发展空间。而且,大海深水储存的热能会以百年的长周期稳定地球表面水能的转化和分布,可谓取之不竭。

同步内容

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Climb atop shoulders and wait for funerals. That, suggested Newton and then Planck, is how science advances (more or less). We've come far since then, but many notions about how people and practices, policies, and resources influence the course of science are still more rooted in traditions and intuitions than in evidence. We can and must do better, lest we resign ourselves to “intuition-based policy” when making decisions and investments aimed at driving scientific progress. Science invited experts to highlight key aspects of the scientific enterprise that are steadily yielding to empirical investigation—and to explain how Newton and Planck got it right (and Einstein got it wrong). —Brad Wible Read more

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Low-dimensional materials exhibit many exceptional properties and functional-ities which can be efficiently tuned by externally applied force or fields. Here wereview the current status of research on tuning the electronic and magnetic prop-erties of low-dimensional carbon, boron nitride, metal-dichalcogenides, phos-phorene nanomaterials by applied engineering strain, external electric field andinteraction with substrates, etc, with particular focus on the progress of computa-tional methods and studies. We highlight the similarities and differences of theproperty modulation among one- and two-dimensional nanomaterials. Recent breakthroughs in experimental demonstration of the tunable functionalities intypical nanostructures are also presented. Finally, prospective and challenges forapplying the tunable properties into functional devices are discussed.Read more

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Moving a liquid–gas boundary along a piece of graphene can induce a waving potential of up to 0.1 V. This waving potential arises from charge transfer in graphene driven by a moving boundary of an electric double layer between graphene and ionic solutions.Read more