Innovative methodology for optimized design and thermo-economic analysis of pillow-plate latent heat thermal energy storage: a case study on heat recovery in the brewing industry

Abstract

This paper investigates the novel class of pillow-plate latent heat thermal energy storage (PP-LHTES) systems based on the combined use of phase change materials (PCM) of pillow plate heat exchanger technology. Despite recent studies highlighting the promising thermal and economic performance of PP-LHTES systems, their investigation remains limited. In particular, there is a lack of comprehensive thermo-economic analyses to support informed decision-making, especially during the design phase. To address this gap, this paper systematically explores the thermo-fluid and economic performance of PP-LHTES systems by analyzing their design space. An innovative procedure for the optimal design of these devices was developed. The proposed methodology consists of two models: a 1D analytical discretized stationary model, called the design model, and a 1D analytical discretized dynamic model, named the dynamic model. The former is used to determine the design parameters and costs, while the latter is used to validate the designed system under dynamic conditions. The two models are validated against relevant experimental studies taken from the literature and show good performances with errors in the order of 10 % for the design model and 2 % for the dynamic model. A total of 27 configurations were evaluated for potential industrial applications, considering energy storage capacities between 5 and 25 MWh and heat transfer rates ranging from 1 to 5 MW. Representative case studies and operating maps highlight the effects of inlet and outlet temperatures and PCM properties on performance. The layer thickness of the storage material and the channel length depend on discharge time, while the channel count remains constant at a fixed heat transfer rate. The heat exchange area, however, varies with energy storage capacity and heat transfer rate. Additionally, cost maps are systematically examined in terms of energy capacity cost ($/kWh) and power capacity cost ($/kW), highlighting the critical relationship between key PP-LHTES design parameters and the overall cost-competitiveness of the technology. Systems designed for higher temperature differentials (ΔT) demonstrated superior thermal and economic performance, reducing the required heat exchange area and lowering both energy and power capacity costs. An exemplar case study is developed, starting from a reference case in the literature, to illustrate the effectiveness of the proposed methodology. This case study outlines the process of gathering input parameters and demonstrates how the outputs of the two models should be processed to achieve the final design. Ultimately, PP-LHTES emerges as a promising and viable solution for industrial applications at the medium and large scales, with energy capacity costs ranging from 30 to $90 per kWh.