Hybrid Cascade Heat Pump and Thermal-Electric Energy Storage System for Residential Buildings: Experimental Testing and Performance Analysis

Valeria Palomba,Luisa F Cabeza,Efstratios Varvaggiannis,David Vérez,André Groβe,Francesco Sergi,Birgo Nitsch,Antonino Bonanno,Nelson Koch,Ralph Herrmann,Sotirios Karellas,Giovanni Brunaccini,Nikolaos Barmparitsas,Andreas Strehlow,Gabriel Zsembinszki,Davide Aloisio,Andrea Frazzica,Giuseppe E Dino

doi:10.3390/en14092580

Abstract

The need for innovative heating and cooling systems to decarbonize the building sector is widely recognized. It is especially important to increase the share of renewables at building level by maximizing self-consumption and reducing the primary energy demand. Accordingly, in the present paper, the results on a wide experimental campaign on a hybrid system are discussed. The system included a sorption module working as the topping cycle in a cascade configuration with a DC-driven vapor compression heat pump. A three-fluids heat exchanger with a phase change material (PCM), i.e., RT4 with nominal melting temperature of 4 °C, was installed on the evaporator side of the heat pump, for simultaneous operation as thermal storage and heat pumping purposes. The heat pump was connected to a DC-bus that included PV connection and electricity storage (batteries). Results showed that the energy efficiency of the heat pump in cascade operation was double compared to compression-only configuration and that, when simultaneously charging and discharging the latent storage in cascade configuration, no penalization in terms of efficiency compared to the compression-only configuration was measured. The self-sufficiency of the system was evaluated for three reference weeks in summer conditions of Athens climate and it was found that up to 100% of the electricity needed to drive the system could be self-produced for a modest cooling demand and up to 67% for the warmer conditions with high cooling demand.

Highlights

Climate change mitigation is calling for integrated solutions that act at different levels to reduce the energy consumption at grid scale, as well as at residential level, through the increase of self-consumption of renewables [1]
Several possible paths were proposed, including passive solutions such as innovative materials for use as insulation and in façades and windows [2,3,4], active solutions with latent storages based on phase change material (PCM) slabs and panels [5,6,7], and energy systems based on solar energy
The present paper presents the results of the experimental testing on a hybrid thermal-electric system, developed in the course of the EU-funded project HYBUILD, including a cascade sorptioncompression reversible heat pump with built-in PCM storage and a DC-bus for battery and PV connection optimized for operation in warm climates for a high level of renewables-powered operation

Summary

Introduction

Climate change mitigation is calling for integrated solutions that act at different levels to reduce the energy consumption at grid scale, as well as at residential level, through the increase of self-consumption of renewables [1]. Among the solar systems for residential applications for maximization of self-consumption, a common solution is the use of a reversible heat pump powered by PV (photo-voltaic) panels that supply the electricity needed to drive the compressor [13,14], or a heat pump connected to PV/T panels that can supply the evaporation heat during winter season. This is highlighted by several authors considering different layouts, such as direct expansion [15], gas-driven [16], water-source [17], dual-source [18]. Their application in combination with solar-assisted systems can either be on the high temperature side of the thermally-driven chiller/heat pump [26] or on the low-temperature side of the system, being charged by the vapor compression heat pump [27,28]

Methods

Results

Discussion

Conclusion