Need for Automatic Bypass Control to Improve the Energy Efficiency of a Building Through the Cooperation of a Horizontal Ground Heat Exchanger with a Ventilation Unit During Transitional Seasons: A Case Study

摘要

One of the ways to improve the energy balance of buildings is through the use of local,renewable energy sources,for example,ground air heat exchanger.This article continues the study on improving energy efficiency of an EAHX working in cooperation with a ventilation unit.In the previously reported study(Romanska-Zapala et al.,2017),performed during the summer of 2016,it was found that in the summer,the continuous operation of these exchangers is not optimal.Furthermore,there is a need for dynamic control of the ventilation unit's fresh air source.This is due to changes in the exchanger's operating status between heating and cooling,as a result of external temperature fluctuations.This article presents the results of in situ measurements of the horizontal,tubular EAHX which supports maintaining the desired temperature in a building by preheating or precooling the inlet air of the cooperating ventilation unit during transitional seasons of the climatic conditions of southern Poland.In particular,this article provides details on the experimental verification of the 2017 thesis regarding the ineffective work of an EAHX during transitional seasons.The influence of the exchanger on changes in the ventilation unit's inlet air temperature is presented.Numerous,unfavorable changes were registered in the state of the exchanger's work,either heating or cooling the flowing air,depending on the relation of outside air temperature to the achieved output air temperature.This indicated that the work of the exchanger was ineffective for buildings.The key to optimal,energy efficient EAHX-ventilation unit system operation during transitional seasons is the dynamic selection of a fresh air source depending on external conditions and the required output air temperature of the ventilation unit(air supplied to rooms),accounting for the increase of electric energy consumption for the fan drive during EAHX operation.