Optimization of Ground-Storage Heat Pump Systems for Space Conditioning of Buildings

Report, 2014

Ground-source heat pump systems use ground as a source or sink of heat for space heating and cooling of buildings. The use of these systems for space conditioning of buildings has increased manifold in the last decade or more. An obvious reason for this rapid growth is the high energy efficiency of these systems, which can reduce the purchased energy by a factor of 7-8 compared to district heating and cooling systems. The energy efficiency of the ground-source systems can be further enhanced by optimizing the design and operation of these systems. Most building energy simulation software available today offer limited capabilities to model ground-source heating and cooling systems for design and simulation purposes. This is because existing borehole heat exchanger models are mostly based on complex numerical methods, which makes their implementation into building energy simulation software quite challenging. There is also scarcity of mathematical models that can rapidly, yet accurately, simulate the dynamic thermal response of the borehole system. The lack of suitable dynamic ground heat exchanger models has also limited the development and implementation of appropriate controllers and control algorithms for ground-source system applications. In this project, various aspects of modelling for design, simulation and control of ground-source heat pump systems have been studied comprehensively. Specific focus has been placed on the development of analytical models and predictive tools for simulating and optimizing performance of ground-source systems. All models and methods developed in the project can be easily implemented in any building energy simulation software to optimize the design and overall performance of ground-source heat pump systems. Another important aspect studied in detail in this project is the analysis and evaluation of borehole systems. Several parameters critical to design and operation of ground-source heat pump systems have been identified and analysed using experimental and field studies. Over forty tests have been conducted in a state-of-the-art laboratory. Field studies have been carried out in various buildings including a single family house, a clubhouse, a police station, a university building and a shopping centre. Various recommendations have been suggested to improve the current design and operation practices of ground-source heat pump systems.