(612g) Modelling of a Small Scale Solar Central Receiver with Pressurized Water for Heat Collection

This paper presents a methodology to model a small scale Central Receiver System (CRS) for the purpose of heating water in a pressurized system with the intent to supply industrial heating loads. The methodology couples a heliostat field model with the receiver model, especially when evaluating the transient optical performance and predicting the heat flux. The study develops a design guide and thermal evaluation of a pressurized water system in a medium temperature environment using a tubular external receiver and determine its geometry with optimum thermal efficiency. The receiver-heliostat field model is implemented in a friendly user interface via Visual Basic while the transient optical performance and heat flux mapping are carried out using Monte Carlo Ray Tracing (MCRT) technique. The receiver model is validated against two reference solar plants with molten salt (i.e. SolarTwo and GemaSolar Plants) and the outputs have achieved a satisfactory match for the receiver thermal rating, receiver geometry and receiver’s efficiency under reported design conditions. The proposed heliostat field consists of 617 units; each has an area of 4 m² in a spiral biomimetic pattern located in Tucson, Arizona. The transient incident flux maps showed an excellent agreement with the design allowable heat flux having peak incident flux not exceeding 600 kW/m². An analysis of several parameters' effects on receiver’s performance was conducted and it was found that a Reynolds number of 60,000 will give the optimum receiver efficiency of 87.6% and accordingly the geometry shall be 6 panels, each has 21 tubes, with 22 mm inner diameter and 4 mm thickness. The tower height effect was evaluated on both field efficiency and average incident heat flux via MCRT where 40 m was the optimum value.