A Study on Solar Air Heating System with Pebble Bed Energy Storage

Abstract

A staggered type Solar Air Heater with aluminum absorber plate and selective coating was experimentally tested to know the performance parameters of the collector. It was found that the collector has maximum efficiency of around 65 % when operating at the air flowrate of 0.0645 kg/s while the efficiency reduced to around 34 % when the flow rate was reduced to 0.0344 kg/s. The parameters obtained from the experimentation processes was utilized to integrate the collector and study the solar heating system for a general living dwelling of Kathmandu having floor area 150 sq. ft. The collector was integrated with pebble bed energy storage for heating during night time and off sunshine hours. Since the performance of collector is major factor for effective solar heating system, the product of collector heat removal factor and transmission absorption product 𝐹𝑅 (𝜏𝛼) 𝑎𝑛𝑑 collector heat removal factor and overall heat loss coefficient 𝐹𝑅𝑈𝐿 values obtained from the experiments were utilized in the simulation to define the collector which therefore is the validated input for the major parameter of the simulation setup. The model for the solar heating system was developed in the simulation software TRNSYS. The performance of system for heating months ranging from October to March were considered. When utilizing the 4 𝑚2 collector area and 0.0645 kg/s flow rate in the collector loop for the pebble bed of length 1.5 m and cross sectional area 0.81𝑚2, the solar fraction covered by pebble bed was found to be ranging from 0.14 for the Months of January to around 0.59 for October when the heating load was minimum.