Domestic Retrofit Assessment of the Heat Pump System Considering the Impact of Heat Supply Temperature and Operating Mode of Control—A Case Study

Muhammad Abid,Donal Cotter,Neil Hewitt,Ming-Jun Huang,Christopher Wilson

doi:10.3390/su131910857

Abstract

In this study, performance assessment of the variable speed compressor-based air source heat pump (ASHP) system as a domestic retrofit technology instead of fossil fuel-based heating technologies for the 1900s Mid terraced house is investigated. The assessment was conducted considering operating mode of control and heat supply temperature impact of the system. In the literature, ASHP system experimental development with variable speed mode (VSM) of control in comparison to fixed speed mode (FSM) of control at low to medium and high heat supply temperature in the context of UK was found with very limited number of studies, but without considering retrofit application. The focus of the earlier studies was on the individual components and performance improvement. The designed heat pump (HP), developed, and tested at constant heat load, simulating the real domestic heat demand under the controlled laboratory conditions and numerical modeling is utilized for the analysis purposes. The HP performance, energy demand, carbon emissions, and cost varies significantly due to changing heat supply temperature (35 °C, 45 °C, and 55 °C), control mode and accordingly the carbon emission and cost savings are achieved. The oil and gas boilers ranges from conventional to highly efficient type and evaluated in terms of annual running cost, energy consumptions, and carbon emissions in comparison with the HP system. Additionally, a comparative study with the existing retrofitted very high temperature ASHP inside the house is conducted. The developed HP at 55 °C could not defeat the very high heat supply temperature HP system (75 °C supply temperature) in performance and cost savings but become attractive at low supply temperature (35 °C). The HP system in VSM at low heat supply temperature instead of gas boiler (90% efficiency) could cut the annual carbon emissions by 59% but with additional 6% running cost for the Mid terraced test house in Belfast climatic conditions.

Highlights

Building’s sector is one of the major contributors to the global emissions and was responsible for 38% of greenhouse gas (GHG) emissions in 2019 [1]
The seasonal (S1, S2, S3, S4), annual house heat demand, electrical energy consumptions, co-efficient of performance (COP) values is summarized in Table 9 for the three considered cases, during the two mode of control
The COP values depends on the heat supply temperature, mean hourly ambient temperature of the climatic conditions, and control mode of operation

Summary

Introduction

Building’s sector is one of the major contributors to the global emissions and was responsible for 38% of greenhouse gas (GHG) emissions in 2019 [1]. In the UK, the residential sector consumes 29% of the total final energy consumption [2] and accounted for. 17% of the total carbon dioxide emissions [2]. Agency (IE(A) [3] says that the sale of new fossil fuel boilers should stop from 2025 to achieve net-zero emissions target by 2050. On the way to net zero emissions, multiple milestones are there and lags in any sector may results in failures to meet the target elsewhere. The energy and climate policy strengthening, and implementation is required by all government to achieve the global pathway to net-zero emissions. The UK as a signatory of this agreement has legislated and set the target of net-zero carbon emission by 2050 [4,5], banned sale of fossil fuel-based boilers by 2025 [6].

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