Numerical Investigation on a Packed-Bed LHTES System Integrated into a Micro Electrical and Thermal Grid

Vittorio Tola,Mario Cascetta,Giorgio Cau,Simone Arena

doi:10.3390/en13082018

Abstract

Currently, energy storage systems are considered a key solution when mismatch occurs between energy supply and demand, allowing a more efficient energy deployment and use. The present paper is focused on the study of a latent heat thermal energy storage (LHTES) system based on a packed bed of encapsulated phase change material (PCM) of spherical shape, conceived as an auxiliary component of a micro-grid to be built in a Research Center located in southwestern Sardinia (Italy). The main purpose of this work was to perform numerical simulations for predicting the performance of the TES system, designed to store the surplus thermal energy produced during the weekend by a heat pump fed by a photovoltaic (PV) plant. The stored energy would then be utilized during the weekdays to integrate the air-conditioning system supply. The numerical simulations were based on a one-dimensional (1-D) two-equation transient model, able to return the thermocline profile of the water and the PCM separately. The behavior of the LHTES device during charge and discharge phases was reproduced, as well as during the standby periods. Finally, two characteristic indexes of the PV system were evaluated, to investigate the effect of TES on grid interchanges, self-consumption, and self-sufficiency.

Highlights

In recent decades, both climate change and depleting conventional energy sources in relation to a growing increase in energy demand have led to the development of high-efficiency energy conversion technologies
This paper investigated the performance of an latent heat thermal energy storage (LHTES) system based on a packed bed of encapsulated spherical phase change material (PCM) integrated into a micro-grid to be built in a Research Center located in Sardinia (Italy)
System based on a packed bed of encapsulated spherical PCM integrated into a micro-grid to be built in a Research Center located in Sardinia (Italy)

Summary

Introduction

Both climate change and depleting conventional energy sources in relation to a growing increase in energy demand have led to the development of high-efficiency energy conversion technologies. According to the IEA, the building sector accounts for almost 41% of the world’s energy consumption, about half of which is caused by air conditioning systems, generating approximately one-third of annual greenhouse gas emissions [2] In this framework, the concept of micro-grid is one of the most attractive key aspects in research efforts to attain a global energy reduction based on an efficient use of interconnected devices in a network [3]. A micro-grid is composed of distributed generators as well as load, energy storage, and protection control devices, with the aim of becoming an integrated system of energy generation, transmission, distribution, and use In this scenario, the viability of renewable energy sources as a desirable solution to overcome environmental issues becomes evident. An efficient use of non-programmable renewable energy sources needs an integration of proper thermal energy storage (TES) units, due to their intermittent and variable nature [4]

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