A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning Unit

The decarbonization of residential cooling systems requires innovative solutions to overcome the mismatch between the renewable energy availability and demand. Integrating latent thermal energy storage (LTES) with heat pump/air conditioning (HP/AC) units can help balance energy use and enhance effic...

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Main Authors: Claudio Zilio, Giulia Righetti, Dario Guarda, Francesca Martelletto, Simone Mancin
Format: Article
Language:English
Published: MDPI AG 2025-07-01
Series:Energies
Subjects:
Online Access:https://www.mdpi.com/1996-1073/18/13/3485
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author Claudio Zilio
Giulia Righetti
Dario Guarda
Francesca Martelletto
Simone Mancin
author_facet Claudio Zilio
Giulia Righetti
Dario Guarda
Francesca Martelletto
Simone Mancin
author_sort Claudio Zilio
collection DOAJ
description The decarbonization of residential cooling systems requires innovative solutions to overcome the mismatch between the renewable energy availability and demand. Integrating latent thermal energy storage (LTES) with heat pump/air conditioning (HP/AC) units can help balance energy use and enhance efficiency. However, the dynamic behavior of such integrated systems, particularly under low-load conditions, remains underexplored. This study investigates a 5 kW HP/AC unit coupled with an 18 kWh LTES system using a bio-based Phase Change Material (PCM) with a melting temperature of 9 °C. Two configurations were tested: charging the LTES using either a thermostatic bath or the HP/AC unit. Key parameters such as the stored energy, temperature distribution, and cooling capacity were analyzed. The results show that, under identical conditions (2 °C inlet temperature, 16 L/min flow rate), the energy stored using the HP/AC unit was only 6.3% lower than with the thermostatic bath. Nevertheless, significant cooling capacity fluctuations occurred with the HP/AC unit due to compressor modulation and anti-frost cycles. The compressor frequency varied from 75 Hz to 25 Hz, and inefficient on-off cycling appeared in the final phase, when the power demand dropped below 1 kW. These findings highlight the importance of integrated system design and control strategies. A co-optimized HP/AC–LTES setup is essential to avoid performance degradation and to fully exploit the benefits of thermal storage in residential cooling.
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spelling doaj-art-cb55401fe831458485d43566e82d86da2025-08-20T03:16:42ZengMDPI AGEnergies1996-10732025-07-011813348510.3390/en18133485A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning UnitClaudio Zilio0Giulia Righetti1Dario Guarda2Francesca Martelletto3Simone Mancin4Department of Management and Engineering, University of Padova, 36100 Vicenza, ItalyDepartment of Management and Engineering, University of Padova, 36100 Vicenza, ItalyDepartment of Management and Engineering, University of Padova, 36100 Vicenza, ItalyDepartment of Management and Engineering, University of Padova, 36100 Vicenza, ItalyDepartment of Management and Engineering, University of Padova, 36100 Vicenza, ItalyThe decarbonization of residential cooling systems requires innovative solutions to overcome the mismatch between the renewable energy availability and demand. Integrating latent thermal energy storage (LTES) with heat pump/air conditioning (HP/AC) units can help balance energy use and enhance efficiency. However, the dynamic behavior of such integrated systems, particularly under low-load conditions, remains underexplored. This study investigates a 5 kW HP/AC unit coupled with an 18 kWh LTES system using a bio-based Phase Change Material (PCM) with a melting temperature of 9 °C. Two configurations were tested: charging the LTES using either a thermostatic bath or the HP/AC unit. Key parameters such as the stored energy, temperature distribution, and cooling capacity were analyzed. The results show that, under identical conditions (2 °C inlet temperature, 16 L/min flow rate), the energy stored using the HP/AC unit was only 6.3% lower than with the thermostatic bath. Nevertheless, significant cooling capacity fluctuations occurred with the HP/AC unit due to compressor modulation and anti-frost cycles. The compressor frequency varied from 75 Hz to 25 Hz, and inefficient on-off cycling appeared in the final phase, when the power demand dropped below 1 kW. These findings highlight the importance of integrated system design and control strategies. A co-optimized HP/AC–LTES setup is essential to avoid performance degradation and to fully exploit the benefits of thermal storage in residential cooling.https://www.mdpi.com/1996-1073/18/13/3485latent thermal energy storagePCMheat pumpresidential air conditioning
spellingShingle Claudio Zilio
Giulia Righetti
Dario Guarda
Francesca Martelletto
Simone Mancin
A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning Unit
Energies
latent thermal energy storage
PCM
heat pump
residential air conditioning
title A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning Unit
title_full A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning Unit
title_fullStr A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning Unit
title_full_unstemmed A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning Unit
title_short A Comparative Experimental Analysis of a Cold Latent Thermal Storage System Coupled with a Heat Pump/Air Conditioning Unit
title_sort comparative experimental analysis of a cold latent thermal storage system coupled with a heat pump air conditioning unit
topic latent thermal energy storage
PCM
heat pump
residential air conditioning
url https://www.mdpi.com/1996-1073/18/13/3485
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