Energy Saving Potential of Radiant Floor Heating Assisted by an Air Source Heat Pump in Residential Buildings

Yu-Jin Hwang,Jae-Weon Jeong

doi:10.3390/en14051321

Abstract

The objective of this research is to establish an appropriate operating strategy for a radiant floor heating system that additionally has an air source heat pump for providing convective air heating separately, leading to heating energy saving and thermal comfort in residential buildings. To determine the appropriate optimal operating ratio of each system taking charge of combined heating systems, the energy consumption of the entire system was drawn, and the adaptive floor surface temperature was reviewed based on international standards and literature on thermal comfort. For processing heating loads with radiant floor heating and air source heating systems, the heating capacity of radiant floor heating by 1 °C variation in floor temperature was calculated, and the remaining heating load was handled by the heating capacity of the convective air heating heat pump. Consequently, when the floor temperature was 25 °C, all heating loads were removed by radiant floor heating only. When handling all heating loads with the heat pump, 59.2% less energy was used compared with radiant floor heating only. Considering the local discomfort of the soles of the feet, the floor temperature is expected to be suitable at 22–23 °C, and 31.5–37.6% energy saving compared with those of radiant floor heating alone were confirmed.

Highlights

In East Asian countries, the air heating approach with an air source heat pump as a residential heating system is attracting much interest because it has been considered as a renewable energy technology in Europe [1]
Radiant floor heating systems have an advantage in terms of thermal comfort, but their slow response to heating load variation [3,4] is undesirable in current buildings as a heating system because it requires a fast or immediate response to the space heating demand [5]
As the floor temperature increased by 1 ◦ C, these components consumed more energy with a linear dimensional change, but the energy consumption of the boiler did not affect the low floor temperatures (i.e., 21 ◦ C and 22 ◦ C) because the boiler was affected by the turndown ratio

Summary

Introduction

In East Asian countries, the air heating approach with an air source heat pump as a residential heating system is attracting much interest because it has been considered as a renewable energy technology in Europe [1]. In Korea, hydraulic radiant floor heating with a gas-fired boiler releasing flue gas to the atmosphere has been commonly used for heating in most residential buildings, including high-rise apartment houses [2]. Radiant floor heating systems have an advantage in terms of thermal comfort, but their slow response to heating load variation [3,4] is undesirable in current buildings as a heating system because it requires a fast or immediate response to the space heating demand [5]. Imanari et al [7] conducted numerical simulations and experiments and concluded that a radiant ceiling panel system creates a more thermally comfortable environment. As Lin et al [10] and Sun et al [11] argue, a convective heating system with a quick reaction is more comfortable than several other types of radiant heating systems; there are still some arguments against this idea and further studies are being conducted for its verification [12]

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Conclusion