Thermal energy storage (TES) is a technology that stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used at a later time for heating and cooling applications and power generation. TES systems are used particularly in buildings and in industrial processes. This paper is focused on TES technologies that provide a way of valorizing solar heat and reducing the energy demand of buildings. The principles of several energy storage methods and calculation of storage capacities are described. Sensible heat storage technologies, including water tank, underground, and packed-bed storage methods, are briefly reviewed. Additionally, latent-heat storage systems associated with phase-change materials for use in solar heating/cooling of buildings, solar water heating, heat-pump systems, and concentrating solar power plants as well as thermo-chemical storage are discussed. Finally, cool thermal energy storage is also briefly reviewed and outstanding information on the performance and costs of TES systems are included.

A ground-coupled heat pump (GCHP) system used to provide the space heating for an office room is a renewable, high performance technology. This paper discusses vapour compression-based HP systems, briefly describing the thermodynamic cycle calculations, as well as the coefficient of performance (COP) and CO₂ emissions of a HP with an electro-compressor and compares different heating systems in terms of energy consumption, thermal comfort and environmental impact. It is focused on an experimental study performed to test the energy efficiency of the radiator or radiant floor heating system for an office room connected to a GCHP. The main performance parameters (COP and CO₂ emissions) are obtained for one month of operation of the GCHP system, and a comparative analysis of these parameters is presented. Additionally, two numerical simulation models of useful thermal energy and the system COP in heating mode are developed using the Transient Systems Simulation (TRNSYS) software. Finally, the simulations obtained from TRNSYS software are analysed and compared to the experimental data, showing good agreement and thus validating the simulation models.

Ground-coupled heat pumps (GCHPs) are an efficient thermal energy production system that can satisfy the gap between heating and air-conditioning. Be that as it may, exploratory research on GCHPs is still lacking. The first objective of this article is to describe a utilitarian energy-efficiency improvement device for a vertical GCHP system that includes a buffer tank (BT) between the heat pump unit and the fan coil units and user supply, utilizing the quantitative regulation of water flow rate with a variable-speed circulation pump. At that point, the investigative estimations are utilized to test the performances of the GCHP system in various operating modes. Fundamental efficiency parameters (coefficient of performance (COP) and CO₂ emission) are achieved for one month of running utilizing two control strategies of the GCHP—standard and optimized regulation of the water pump speed—and a benchmarking of these parameters is achieved. Exploratory research has indicated higher efficiency of the system for the flow regulation solution utilizing a BT and programmed control equipment for the circulation pump speed compared with the standard regulation solution (COP_sys with 7–8% higher and CO₂ emission level 7.5–8% lower). The second objective is to elaborate a simulation model of the necessary heat/cold in heating and air-conditioning periods, utilizing the Transient Systems Simulation (TRNSYS) program. Finally, the simulation, acquired utilizing the TRNSYS program, is analyzed and compared with experimental information, leading to a good agreement and, along these lines, the simulation model is approved.