SOLAR THERMOCHEMICAL ENERGY-STORAGE SYSTEM (THERMOCHEMICAL BATTERY)

Abstract

This work aimed to investigate the potential of direct storage and restoration of solar energy in a chemical form and to construct a portable, rechargeable, and usable solar thermochemical battery for agricultural applications. Many attempts were conducted to select a suitable thermochemical storage material (TCM) among which are self-indicating silica gel (blue/pink), commercial white silica gel, and natural zeolite. During the experiments, moist TCMs samples were dried (energy-charged) by a one square-meter stainless-steel parabolic solar energy concentrator in three experimental configurations. An experimental aluminum thermochemical battery size 35×35×5 𝑐𝑚 filled with 3.5 𝑘𝑔 of TCMs working as a heat-exchanger and a portable energy charging/discharging thermal battery was evaluated. Energy restoration (discharging) was achieved by applying forced humid air generated from an ultrasonic mist generator and an air-circulation fan through a set of perforated pipes located inside the thermochemical battery. Results showed that TCM self-indicating silica gel was able to store 165 Wh/kg of solar energy at the charging process compared to natural zeolite (124 𝑊ℎ/𝑘𝑔) and white-silica gel (80 𝑊ℎ/𝑘𝑔). The energy discharging efficiency of the self-indicating silica gel was 57.7%, while the efficiency of the natural zeolite and white silica gel was 45.8% and 39%, respectively. Direct storage and use of solar energy in a thermochemical (TCM) form can reduce costs and maintenance of renewable energy applications compared to the high-cost photovoltaic systems. TCMs thermochemical batteries, like traditional electrical batteries, can act as energy master-key for different agricultural applications, as well as in thermo-sensitive processing and treatment.