Viability of a Packed Bed Thermal Storage Integrated with Evacuated Glass Tube Solar Air Heater for 30° to 300℃

摘要

Periodic and intermittent nature of solar radiations needs thermal storage to take care of temporal mismatch of energy supply and demand. This paper presents the design of pebble bed thermal energy storage unit viability using different insulation materials and issues related to its integration with a high temperature solar air heater. The study deals with optimization of bed design and operational parameters viz. pebble size (dp), bed size (db), air mass velocity (Ga), void fraction (εb), flow phenomenon (Re) and pressure drop (△p). Transient response of solid media, bed heat transfer and air / pebble temperature variations with time and location is studied assuming that TES is coupled to a high temperature solar air heater developed at Heat Pump Laboratory, ⅡT Bombay. In storage analysis, pebble diameter affects surface area available for heat transfer, transport coefficient, pressure drop and bed temperature. It is observed that major portion of stored heat can be recovered at temperature very close to the maximum temperature due to temperature stratification along bed length. Development cost of the thermal energy storage unit is estimated which is a small fraction of the cost of the solar collector and so would be worth integrating.