Free-cooling thermal energy storage using phase change materials in an evaporative cooling system

Phase Change Materials (PCMs) offer a means of storing thermal energy when efficiently available and returning it when required. Evaporative cooling systems are considered to be efficient and environmentally friendly. This paper studies the application of PCMs to an industrial Evaporative cooling system to enable the capture and storage of night-time sensible free-cooling, as a means of reducing energy costs and improving demand-side management. The stored cooling is subsequently utilised in the cooling water system during a day-time peak demand to achieve the required cooling capacity at the required temperature, resulting in a reduction of the day-time refrigeration requirements. A computer model has been created using Matlab/Simulink, to simulate the operation with and without the PCM. The PCM, Chiller and Circulation Pump were simulated using manufacturer's data. The Cooling Tower performance was approximated from historical weather data and recorded electrical data. The output of the model demonstrates that the system is functional and successfully achieves a 67% reduction in chiller peak-time operation. It also calculates the power requirement and energy cost of both scenarios. The cost savings were determined along with an estimate of the capital investment required. A commercial viability sensitivity analysis has also been performed. (C) 2013 Elsevier Ltd. All rights reserved.