Silver is a strategic material for renewable energy. Among other applications related to PV, it is used as reflective layer in solar mirrors for concentrated solar power (CSP), thanks to its high reflectance in the whole solar range. CSP plants require large mirror areas, typically in the 0.1 to 1 km². However the estimated reserves of silver do not exceed 20 years. To sustain the deployment of CSP as a valuable input in the future energy mix, silver must be replaced with a less critical material, ideally low cost. In this theoretical study we propose to replace silver by aluminum, adding a dielectric multilayer coating on top, to reach similar optical performance. This design is inspired by Bragg mirrors but differs in that the stack parameters (layer thicknesses) are individually optimized, so as to maximize solar reflectance. A thin aluminum layer with MgF₂/TiO₂ aperiodic stack on top can theoretically reach solar reflectance of 96.1%, higher than silver (95.5%). Other materials are also found suitable: SiO₂, ZnO, ZrO₂. A reasonable number of layers (〈20) not only enhances the optical performance of metallic reflectors, but also allows tuning said performance, which is not possible with classical mirrors relying on a single metal reflective layer. For instance, one can optimize the stack to reach a better performance than silver at typical mean incidence angles of solar light in CSP plants, for different locations. A solar mirror without rare or precious materials and more effective than traditional silver mirrors is thus obtained.

白银是可再生能源的战略材料。在与光伏相关的其他应用中，由于其在整个太阳能范围内的高反射率，它被用作聚光太阳能 (CSP) 的太阳能反射镜中的反射层。CSP 工厂需要大的镜像区域，通常在 0.1 到 1 km ². 然而，白银的估计储量不会超过 20 年。为了维持 CSP 作为未来能源组合中有价值的投入的部署，白银必须替换为不太重要的材料，理想情况下成本低。在这项理论研究中，我们建议用铝代替银，在顶部添加介电多层涂层，以达到类似的光学性能。这种设计的灵感来自布拉格反射镜，但不同之处在于堆栈参数（层厚度）是单独优化的，以便最大限度地提高太阳反射率。顶部具有 MgF ₂ /TiO ₂非周期性堆叠的薄铝层理论上可以达到 96.1% 的太阳反射率，高于银 (95.5%)。其他材料也被发现是合适的：SiO ₂、ZnO、ZrO ₂. 合理的层数 (<20) 不仅增强了金属反射器的光学性能，而且还允许调整所述性能，这对于依赖单个金属反射层的经典反射镜是不可能的。例如，可以优化堆栈以在不同位置的 CSP 工厂中太阳光的典型平均入射角下达到比银更好的性能。从而获得一种没有稀有或珍贵材料且比传统银镜更有效的太阳镜。