Soiling of solar collectors - Modelling approaches for airborne dust and its interactions with surfaces

This literature review deals with the well-known problem of soiling in solar plants, which it severely affects the energy yield of solar power plants. A loss of reflectivity due to soiling reduces the entire productivity of the plant by limiting the energy harvested (i.e. the incoming direct normal irradiance is not properly reflected towards the right focus). On the other hand, the costs of maintenance and cleaning of the collectors represent a significant component of the plant operational costs. Therefore, in this paper, a multi-disciplinary literature review is conducted with the aim of collecting existing models for the key processes, organising them into a ‘dust life cycle’. This cycle is divided into four steps: Generation, Deposition, Adhesion, and Removal; with emphasis on the interaction between dust particles and solar collectors’ surfaces. Generation deals with the loading of atmosphere with dust particles, deposition concerns the processes that actually bring airborne dust onto the collectors’ surface, adhesion and removal represent the competing forces whose balance determine which particles remains adherent on the collectors and which are detached. The intent is to provide a complete framework for the development of a future physical model for the prediction and estimation of the actual soiling of the solar collectors, which engineers can implement in order to maximize the revenues of CSP plant, pushing towards more clean and sustainable energy production technologies