Performance Investigations of the Charging and Discharging Processes in a 3-Tank Thermal Energy Storage System

Swalehe Tusiime, Karidewa Nyeinga, Denis Okello, Ole J. Nydal


The paper presents a 3 tank thermal energy storage system. The system consists of cold oil reservoir, heat storage tank, and a residual drainage tank. Cold oil flows by gravity into a heating chamber and after being heated to the required temperature, a mechanical thermostat opens allowing the hot oil to flow into a heat storage tank. The storage tank was discharged through the cooking unit by boiling 0.5 litres of water. The used oil flowed by gravity to the drainage tank. The discharge flow rates of 0.5, 2.1, 2.8 and 6.5 g/s were considered. A charging efficiency of 51.3% and overall discharging efficiency range of 15.3 34.7% were achieved. Charging efficiency increased when the source was embedded in the storage tank. The instantaneous discharge power had a peak value for each flow rate. The adopted cooking unit had a thermal transfer efficiency range of 34.7 57.6%. A method for sizing oil based TES systems was proposed and illustrated based on the obtained discharge results.

Keywords:    3-tank; sizing; discharging; efficiency; thermal energy.

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