Exploiting renewable energy is an extremely effective strategy for alleviating and addressing the energy issues. To effectively harvest renewable energy, the investigations of fundamental thermodynamics resources of the sun and outer space have attracted significant attentions and various attempts have been carried out for energy-related applications. The key of effective energy harvesting and conserving from the sun and outer space relies on the precise manipulation of the electromagnetic responses including selective reflection, transmission, and absorption/emission in particular frequency ranges, which plays a critical role in various practical applications. According to the utilization of spectral bands, the electromagnetic responses are summarized into the single-band and multi-band characteristics. The single-band applications including the photovoltaic and photothermal conversion, thermal photons radiation, radiation cooling, and smart windows coatings, enable individually the utilization of the solar energy or the thermal radiation. In addition, the hybrid photovoltaic-thermal system and solar absorber/thermal emitter subtly synergize the photovoltaic and photothermal or thermal radiation through multi-band spectral modulation. In order to figure out the basic mechanisms of existing renewable energy technologies based on various electromagnetic responses, herein, we briefly summarize the optical characteristics from the perspective of spectral tuning and review their corresponding practical technologies. This article aims to provide a perspicuous mainline for existing spectral controlling work and to inspire other innovative optical tuning for potential energy applications.

开发可再生能源是缓解和解决能源问题的极为有效的策略。为了有效地收集可再生能源，对太阳和外层空间的基本热力学资源的研究引起了极大的关注，并且已经进行了与能源相关的应用的各种尝试。从太阳和外层空间有效收集和保存能量的关键取决于对电磁响应的精确控制，包括在特定频率范围内的选择性反射，透射和吸收/发射，这在各种实际应用中起着至关重要的作用。根据频谱带的利用，将电磁响应概括为单带和多带特性。单波段应用包括光伏和光热转换，热光子辐射，辐射冷却和智能窗户涂层，可分别利用太阳能或热辐射。此外，混合光伏热系统和太阳能吸收器/热辐射器通过多波段光谱调制巧妙地协同了光伏和光热或热辐射。为了找出基于各种电磁响应的现有可再生能源技术的基本机理，在这里，我们从光谱调谐的角度简要总结了光学特性，并回顾了其相应的实用技术。