Midrio Michele, Pierantoni Luca, Boscolo Stefano, Truccolo Davide, Mencarelli Davide
Opt Express. 2022 Feb 28;30(5):7017-7034. doi: 10.1364/OE.450020.
Solar rectennas are promising devices for energy harvesting. Capability of rectennas to convert incident light into useful energy depends on the antenna efficiency, that is the ratio between the power transferred to the load vs the incoming power. In this work, we first emphasize that for the efficiency to be calculated accurately, antennas need to be treated as receiving devices, not as transmitting ones. Then, we propose an arrangement of antennas that differs from those published so far in three respects: (1) the proposed arrangement is formed by an array of nano-antennas with sub-wavelength inter-element spacing, (2) it comprises a reflecting mirror, and (3) it allows for dual polarization operation. Through numerical simulations, we show that the small lattice pitch we use is responsible for frequency flattening of the lattice impedance over the whole solar spectrum, eventually allowing for excellent matching with the antennas' loads. Also, the small pitch allows for a smooth dependence of the receiving efficiency on the angle of incidence of sunlight. Finally, we show numerically that the reflecting mirror also allows for an almost complete cancellation of light scattered by the receiving antennas. The final result is a polarization insensitive receiving theoretical efficiency larger than 70% over the whole 300-3000 nm spectral range, with a less than 10% energy wasting due to back-scattering of sunlight.
太阳能整流天线是很有前景的能量收集装置。整流天线将入射光转换为有用能量的能力取决于天线效率，即传输到负载的功率与入射功率之比。在这项工作中，我们首先强调，为了准确计算效率，天线应被视为接收装置，而非发射装置。然后，我们提出了一种天线排列方式，它在三个方面与迄今已发表的排列方式不同：（1）所提出的排列由具有亚波长元件间距的纳米天线阵列构成；（2）它包括一个反射镜；（3）它允许双极化操作。通过数值模拟，我们表明我们所使用的小晶格间距导致了晶格阻抗在整个太阳光谱上的频率平坦化，最终实现了与天线负载的极佳匹配。此外，小间距使得接收效率对太阳光入射角具有平滑的依赖性。最后，我们通过数值模拟表明，反射镜还能几乎完全消除接收天线散射的光。最终结果是，在整个300 - 3000纳米光谱范围内，极化不敏感接收理论效率大于70%，由于太阳光的反向散射造成的能量浪费小于10%。
