The energy of saline gradients is a very promising source of non-intermittent renewable energy, the exploitation of which is hampered by the lack of viable technology. The most investigated harvesting methods rely on selective transport of ions or water molecules through semi-permeable or ion-selective membranes, which demonstrate limited power densities of the order of a few W m⁻². While in the last decade, single nanofluidic objects such as nanopores of nanotubes have opened up very promising prospects with power density capabilities in the order of kW or even MW m⁻², scale-up efforts face serious issues, as concentration polarization phenomena result in a massive loss of performance. We propose here a concept of a nanofluidic exchanger for power generation from saline gradients, focused on designing a nanoscale flow able to harvest the power at the output of the nanopores. We study analytically and numerically a simple exchanger made of a selective nanoslit fed by a nanofluidic assembly. One specific feature of such an exchanger relies on the non-linear ion fluxes through the nanoslit analytically expressed from the integration of the Poisson–Nernst–Planck equations. Such an elemental brick could be massively parallelized in stackable electricity-generating layers using standard technologies of the semi-conductor industry. We demonstrate here a scheme for rationalizing the choice of the exchanger parameters, taking into account the transport properties at all scales. The full numerical resolution of the three-dimensional device shows that net power densities of 300 W m⁻² and more can be achieved.

中文翻译：

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用于收集盐梯度能量的纳米流体交换器


盐水梯度的能量是一种非常有前途的非间歇性可再生能源，但由于缺乏可行的技术，其开发受到阻碍。研究最多的收获方法依赖于离子或水分子通过半透膜或离子选择性膜的选择性传输，这些膜表现出几 W ^m-2 量级的有限功率密度。虽然在过去十年中，单纳米流体物体（如纳米管的纳米孔）已经开辟了非常有前途的前景，其功率密度能力达到 kW 甚至 MW ^m-2 的数量级，但放大工作面临着严重的问题，因为浓度极化现象会导致性能的大量损失。我们在这里提出了一个纳米流体交换器的概念，用于从盐梯度发电，重点是设计一种能够在纳米孔输出处收集能量的纳米级流动。我们从分析和数值上研究了由纳米流体组件进料的选择性纳米狭缝制成的简单交换器。这种交换器的一个具体特征依赖于通过纳米狭缝的非线性离子通量，该磁通量由泊松-能斯特-普朗克方程的积分解析表示。这种元素砖可以使用半导体行业的标准技术在可堆叠的发电层中大规模并行化。我们在这里演示了一种合理化交换器参数选择的方案，同时考虑到所有尺度的传输特性。三维器件的全数值分辨率表明，可以实现 300 W m⁻² 或更高的净功率密度。