Year round performance of double pass solar air heater with packed bed

Cyclic operation of molten-salt thermal energy storage in thermoclines for solar power plants

“…A low-cost filler material compatible with molten salts, 10 such as quartzite rock [5], is used to occupy most of the volume of the thermocline 11 and acts as the primary thermal storage material. This helps greatly reduce the 12 amount of the relatively more expensive molten salt that is required in a two-tank 13 storage system. It was shown in system studies [6,7] that a TES thermocline may 14 offer the lowest-cost energy storage option, saving 35% of cost compared to the 15 two-tank system.…”

“…In order 10 to improve the Rankine cycle efficiency to a level higher than 40%, the desired 11 storage medium must withstand temperatures above 450C [2] while featuring low 12 vapor pressures. Pressurization of the solar thermal power system for use with 13 current synthetic oils above 400°C is cost-prohibitive. 14 Molten salts are likely ideal candidates as storage media with increased storage 15 temperatures close to 500C and extremely low vapor pressures.…”

“…The influence of the 11 interstitial heat transfer rate and the filler thermal conductivity were discussed in [19]. 12 The effect of non-adiabatic boundaries on the thermal performance of thermocline 13 tanks was explored in terms of the internal flow structure and resulting discharge 14 efficiency in [20]. Thermal ratcheting of the tank wall caused by temperature 15 variations and the settling of the filler particles was analyzed with a comprehensive 16 thermomechanical model in [21].…”

“…12 Mawire et al [14] developed a simplified one-dimensional single-phase model for an 13 oil-pebble TES system to examine the thermal performance of three different pebble 14 materials; a high ratio of the total exergy to the total energy stored was suggested as a 15 good measure of thermal performance of the pebble material. A feedforward 16 internal model control (IMC) structure for controlling the charging temperature of 17 such a TES system for a solar cooker was also presented; thermal stratification was 18 observed in the storage tank [15].…”

“…Assuming that the distributor regions are properly designed so that uniform 12 flows are achieved at the inlet and outlet of the filler bed [18], and the molten salt 13 temperatures from the collector field T h and from the preheater T c are constant, the 14 boundary conditions may be specified as follows: 15 a) At the top exit of the filler bed, molten salt at the temperature of the upstream flow 16 exits the tank in the discharge period; in the charge period, on the other hand, molten 17 salt at T h ( l = 1) from the collector field flows into the tank. Therefore, the 18 nondimensional flow and thermal conditions are given as: 14 In the discharge half-cycle (0 <  < 1):…”