Seasonal effect of dust deposition on a field of evacuated tube collectors on the performance of a solar desalination plant

This paper reveals the results of a study aimed at identifying the seasonal influence of dust deposition on a large field of evacuated tube collectors associated with a multiple-effect distillation plant on the performance of the plant. The system is located near the city of Abu Dhabi, UAE, and the results are therefore relevant to this region. Seasonal dust measurements were made on the system and a mathematical model of the dust effect is incorporated within the SOLDES program, which predicts the performance of such systems, taking into consideration the prevailing dust influence and the frequency of collector cleaning. It was found that dust deposition has a strong seasonal effect on the plant performance with the strongest influence taking place during the summer months of June, July and August during which sand storms prevail in the plant location. It was found that dust deposition can cause a monthly drop in glass tube transmittance of 10-18%. The drop in transmittance of the glass tubes due to dust deposition can cause a large drop in plant production. For example, for a transmittance decrease from an initial value of 0.98 (clean glass condition) to a low value of 0.6, corresponding to a very dusty glass condition, production drops from 100% to 40% of the clean collector production level. The weekly cleaning frequency was found to result in the maximum annual water production for the particular location under consideration. It was found that dust deposition decreases the specific water production (m(3) of water per U of incident solar radiation) and increases the specific power consumption (kWh per m(3) water).