无动力制冷（passive cooling），由德国法兰克福的考斯特博士（Dr. Helmut Köster）首创的概念，通过改变百叶窗表面的形状，在导入太阳光作为室内自然光源的同时，又能够有效将紫外线与太阳热能阻挡在了室外，使得室内温度不会随着太阳光的导入而急速提升，从而降低了室内对于制冷能耗的需求。只有7%-10%的能量以光和热的形式被导入室内，考斯特博士发明的“回复技术”，可有效将太阳热能反射回天空，不会对室内造成额外的制冷负担，同时阳光的纵深导入亦不会受到影响，获得“清爽自然”的天然光源。

Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or nil energy consumption. This approach works either by preventing heat from entering the interior (heat gain prevention) or by removing heat from the building (natural cooling). Natural cooling utilizes on-site energy, available from the natural environment, combined with the architectural design of building components (e.g. building envelope), rather than mechanical systems to dissipate heat. Therefore, natural cooling depends not only on the architectural design of the building but how it uses the local site natural resources as heat sinks (i.e. everything that absorbs or dissipates heat). Examples of on-site heat sinks are the upper atmosphere (night sky), the outdoor air (wind), and the earth/soil.