Course objectives: Students will be introduced to a relatively new term of thermogeology and therefore will be able to understand the principles of designing ground heat exchangers in order to use low enthalpy geothermal resource and heat pumps as part of the thermotechnical system. Also, students will be able to evaluate impact of specific thermogeological parameters, such as thermal conductivity, thermal diffusivity, density, moisture and ground/rock permeability, on system (borehole heat exchanger or very shallow heat exchanger) design. During the course, the students will be able to perform practical measuring of thermal conductivity and undisturbed ground temperature on coaxial borehole heat exchanger installed on the Faculty premises, according to ASHRAE method and using thermal response test apparatus.

Course content:

• Deep and shallow geothermal energy;
• Direct and indirect utilization of thermal energy;
• Shallow geothermal energy potential and definitions of fundamental parameters;
• Fundamental thermodynamic and technological characteristics of heat pumps with ground and groundwater as a heat source;
• Overview of equipment and technology;
• Ground source heat pump working modes as a necessary asset to utilize low enthalpy geothermal potential;
• Theoretical fundamentals of modelling borehole heat exchangers as a low enthalpy geothermal source for heat pump;
• Defining the working cycle of the ground source heat pump, calculations of fundamental parameters in TS diagram;
• Analytical solution to cylindrical heat transfer model;
• Analytical solution to line source heat transfer model;
• Calculations of fundamental thermogeological and physical variables of source rock and fluid necessary for heat pump;
• Kavanaugh’s numerical model for temperature distribution surrounding the borehole, based on solution to cylindrical heat transfer;
• Eskilson’s numerical model for long-term temperature response of the borehole heat exchanger;
• Graphoanalytical analysis of undisturbed ground temperature and its depth;
• Defining fundamental input parameters necessary for evaluating shallow geothermal potential;
• Modelling borehole heat exchanger field using RETScreen program;
• Modelling borehole heat exchanger field as a function of specific input parameters, part I: borehole heat exchanger field design and sizing as a function of its life cycle, impact of distance on sizing borehole heat exchanger field, impact of entering source temperature and leaving load temperature on sizing and design on borehole heat exchanger field;
• Modelling borehole heat exchanger field using GLD and GHX programs;
• Measuring thermal conductivity using thermal response test (TRT) apparatus on inclined coaxial borehole heat exchanger, located on Faculty premises;
• Calculation and analysis of thermal conductivity obtained via thermal response test;
• Modelling of inclined coaxial borehole heat exchangers based on known thermogeological parameters;
• Analysis of data obtained via TR test and step TR test – evaluating borehole thermal resistance, skin factor and extraction rates;
• Modelling very shallow geothermal heat exchangers, up to 2 m in depth;
• Using ground stored solar energy;
• Overview of available technology and techniques of installation;
• Technoeconomical analysis of cost effectiveness of using ground and groundwater heat pump;
• Overview of energy sources, calorific values, pricing and energy savings;
• Reducing CO₂ by using ground source or groundwater source heat pumps compared to conventional energy systems;
• Comparison in RETScreen program.

Learning outcomes at the level of the course:

• Formulate thermodynamic laws of conductive heat transfer;
• Assess influence of thermogeological parameters on shallow geothermal energy exploitation;
• Design geothermal borehole heat exchangers field, up to few hundred meters in depth, recommend drilling method and grout type, based on thermogeological data;
• Analyse impact of hydrogeological, geological and climate parameters on heat exchanger efficiency;
• Evaluate thermogeological energy potential of a given location by analysing thermal response test data;
• Elaborate working principles of a heat pump, with ground as a thermal source, describe mechanical elements, evaluate coefficient of performance;
• Evaluate required borehole heat exchanger length using analytical methods.