Indian Journal of Science and Technology

Abstract

Objective: To find out how energy storage capacity and energy holding capacity changes at different concentration and the effects of each salt on these factors. Method/Statistical Analysis: This system utilises a mixture of nitrate salts in water as primary medium for storing sensible heat.A mixture (300 gm) of Sodium Nitrate (NaNO3 ) and Potassium Nitrate (KNO3 ) at different wt% (60/40, 50/50, 40/60) in 1 litre of distilled water were used for experiments. Each sample was heated until its boiling point was reached and time was noted for each 1-degree rise. Findings: In this study a Thermal Energy Storage system for low-grade heat recovery is being proposed. As the atomic size of salt increases calorific value of mixture decreases & overall energy storage capacity decreases. But temperature increment of system is faster. But, for energy holding capacity KNO3 has shown better results than NaNO3 . Its reason could be the atomic weight of the salt molecule. Among all 50 : 50 solutions have the maximum amount of energy stored and 60 : 40 solution has the slowest rate of heat loss among all. Applications/Improvements: This system can be used for applications like space heating, water heating etc. and for power generation also in conjunction with Organic Rankine Cycle (ORC) turbines which can operate at temperatures as low as 70°C.

Keywords: Heat Capacity, Heat Loss Rate, Low-Grade Heat, Specific Heat Capacity, Waste Heat Recovery, KNO3 ,NaNO3