Modeling of the temperature field in the soil massive for different operating modes of the ground source heat pump

Abstract

The paper considers modeling the influence of the operating modes of the ground source heat pump for heating and air
conditioning systems using geothermal source of energy from borehole on the temperature of the soil formation around the borehole
with the account of climate conditions of Ukraine. The proposed methodology of modelling of the ground source heat pump with the
account of reversible direction of heat flow for heating and cooling work modes contributes to the field of energy system models.
The ultimate goals are to obtain criterion dependencies for calculating the operating parameters of a geothermal borehole and to
develop a methodology for designing geothermal boreholes taking into account their long-term operation in a cyclic mode. The idea
behind the method allows high spatial and temporal resolution as well as the inclusion of the technical details of the power system
and formation the temperature of the soil massive around the borehole for the climate conditions of the Ukraine and South-East
Regions of Europe. The novelty of this method is the usage of a parametric approach is chosen to analyze different reversible
operating modes of the ground source heat pump for heating and cooling. This provides insights on the systematic effects of ground
source heat pump operation with regeneration with limitation on reaching negative temperatures at the bottom of the borehole, which
can lead to ice formation, an increase in the volume of soil massive during freezing and destruction of pipelines. The article describes
the change in the temperature of the soil mass under the operating conditions of a heat pump in two modes - stationary and with
alternating "heat supply - cooling (air conditioning)" for long-term operation. Based on the obtained results it was revealed that when
a geothermal borehole operates with an alternating direction of heat flow (with regeneration), the long-term consequences of
operation associated with the deviation of the soil massive temperature from the background value are reduced. The additional
novelty aspect of modelling was obtained for the operating parameters of a geothermal source of energy with the account of longterm reversible operating mode of the heat pump. The energy balance model is well suited for the analysis of temperature in the
bottom part of the geothermal boreholes was revealed for heating and air conditioning systems due to the non-stationary thermal
loads determined by climatic conditions of the Ukraine and South-East Regions of Europe. The obtained results may serve as a new
approach to optimization technical and economic indicators of geothermal boreholes during operation of the ground source heat
pump operating with the account of reversible direction of heat flow for heating and cooling work modes to have continuous
improvement of energy efficiency.