Performance Analysis of Flat Plate Solar Collector Networks in Batch Operation Considering Scaling

In this study, the batch operation of a solar system equipped with flat plate collectors, considering the effects of scaling fouling is investigated. During this process, the heat extracted from the working fluid as it leaves the collector field is combined with water in a storage tank. Subsequently, this mixture is recirculated through the solar network, repeating the cycle until the desired target temperature is attained. The duration of this process can vary based on the operating period and environmental conditions, and it may extend beyond a single day. Different network structures, which are represented by combinations of series-parallel arrangements with a fixed number of solar collectors are investigated. The objective of this study is to identify the network design that achieves the target temperature and the required thermal load in the shortest possible time, thereby positively impacting pumping costs. As a case study, a solar thermal plant with 40 collectors is analysed. The original structure of the collector field contains 4 lines, each line consists of 2 subsections connected in series, and each subsection includes 5 parallel-connected collectors (referred to as 4Lx5p-2s). The findings indicate that modifying the original structure to a 4Lx2p-5s (4 lines, 5 subsections by line connected in series each one with 2 collectors connected in parallel) arrangement achieves the thermal objective more efficiently, resulting in reduced operating costs, reducing the time to reach the desired temperature in one hour, which results in the increase of the number of batches that can be processed per year from 200 to 216. Over time, scaling builds up in the collectors, leading to increased pressure drops and reduced heat transfer capacity. It is demonstrated that under fouled conditions, an 8Lx5s arrangement yields a system with improved thermohydraulic performance as the batch time is reduced by almost 4 h and the number of batches that can be processed per year increases from 140 to 170.