An investigation on factors influencing dust accumulation on CSP mirrors

Abstract

Abstract..The profitability of a CSP plant is highly affected by the efficiency of the solar field: it is essential to maintain mirrors' reflectivity at high level to avoid thermal power loss. Dust fouling is the main cause of reflectivity loss and cleaning of mirrors is a crucial activity to restore economical level of reflectivity. However, the high cost of cleaning operations requires the study and identification of a balanced plan for the dust removal. The dust generation and transport to the plant site is the first mechanism that needs to be modelled to identify the optimal schedule for cleaning operations and it is highly dependent on weather conditions. Several studies have suggested a dependency of reflectors performance with humidity level, frequency of rainfalls, wind and mirrors' tilting angle, however rarely quantitative correlation studies have been performed to validate these hypotheses. The aim of this research is to provide an in-depth insight on interaction between the main parameters and airborne dust concentration, providing quantitative information for the development of future mirror dusting models. Outcomes evidence the crucial role of high winds responsible of dust concentration in conjunction with higher wind direction frequencies in the range 60-120°. Actually, in this scenario a perfectly monotonic increase of dust accumulation in the air has been observed with high correspondence of wind direction. A very low effect is provided by the ambient temperature as the contribution of the barometric pressure.

Dust impact on concentrated solar power: A review

“…To sum up, dust deposition is non-negligible and can cause energy losses up to 88% [107] and reflectivity losses up to 80% [102], the soiling rate depends upon the wind direction and the exposure direction of the reflectors [36,46,108], and their placement within the solar field, in particular, first-row reflectors suffer from uniform soiling and are soiled more than the rest of the solar field [96,102,103]. These are important factors to consider when planning optimal cleaning schedules that keep the efficient reflectors' performance at good levels.…”

“…precipitations [36,108], wind speed and direction [108], and relative humidity [53]. Tilted reflectors are less soiled, and glass mirrors -compared to other materials-lose their reflectivity faster and restore it better after cleaning, these properties are helpful in sites where frequent cleaning is possible [36,46,98].…”

“…Defect rates for glass reflectors are smaller than those for aluminum ones. Pennetta et al [108] Australia, 1 year Strong correlation between the deposition of dust and the wind's speed and direction. Soiling starts at wind speeds of 3 m/s.…”

A review of the application performances of concentrated solar power systems

“…Soiling is the deposition of sand and dust on the surface of solar panels, resulting in reduced performance. Yu et al [74] detected the main variables that contribute to dust accumulation: temperature, speed and wind direction.…”

Aluminium Nitride Doping for Solar Mirrors Self-Cleaning Coatings

“…Concentrating solar power could become the cheapest form of energy production in many regions of the word, with the only problem of maintaining the solar field performance [1]. In particular, the areas of the global sunbelt, where concentrated solar power plants are typically located, suffer from high soiling due to dust accumulation, and this reduces the amount of solar energy received (and hence electricity produced), increasing LCOE [2]. The energy yield loss per day can exceed 20% if mirrored surfaces are not cleaned [3].…”