An application of seasonal borehole thermal energy system in Finland

Borehole thermal energy system is an important component of the future low temperature heating networks. Applications of such systems are available around the world presenting various configurations. However, the mobility of the system from solar assisted to industrial heat has not yet evaluated. A 3D model of borehole thermal energy system created similar to Drake landing solar community project configuration. This model is validated with experimental measurements. The accuracy of the model estimated at 95%. Experimental measurements further utilized to create an artificial neural network model to predict modes of operation (charging/discharging). The accuracy of the model calculated at 97%. This study presents a possible application of storing excess heat from combined heat and power plants in Sodankylä, Finland. The municipality of Sodankylä is planning construction of new combined heat and power plants. These plants systematically shutdown during summer season leaving 1.53 ​MW of excess heat. The heat surplus can be stored in a heat storage. Simulations reveal that the model has storage capacity between 250 ​kW and 285 ​kW. In addition, there is a potential of five borehole thermal energy storage to store the entire excess heat. The novelty of the study is to test the mobility of borehole thermal energy system from solar assisted storage to industrial excess heat storage. The model used in a standardized manner considering the conventional combined heat and power plants supply temperature for working configuration of heat storage.©2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

Applications of Thermal Energy Storage with Electrified Heating and Cooling

With a clear correlation between climate change and rising CO2 emissions, decarbonization has garnered serious interest in many sectors to limit the adverse effects of global warming. Heating and cooling systems have been a focus of decarbonization efforts, with heat pumps becoming more popular in the United States and abroad. In fact, heating, ventilation, and air conditioning accounts for nearly 27% of total energy use in the United States [1]. Ground source heat pumps (GSHP) utilizing borehole heat exchangers (BHE) have been shown to be an effective method of electrifying heating and cooling systems, maintaining some of the best performance for any electrified heating and cooling system currently available. Electrification, however, does come with some significant challenges. One of particular importance is the significant increase in peak demand during the heating season, which can result in a serious cost increase for the operator of the electric heating system, as well as adding operational complexities to grid operations by shifting from a summer peak to a winter peak as more heating loads are electrified. Thermal energy storage (TES) has been shown to be effective in mitigating the increase in peak demand that is seen with electrified heating and cooling systems. By storing thermal energy during off-peak hours, demand can be effectively shifted away from the peak hours. In this study, we investigate the potential of a ground source heat pump coupled with a TES system, in the form of water storage tanks, for the University of Massachusetts, as a way of decarbonizing the institution’s HVAC system while minimizing operating and installed costs

Performance evaluation and control scenarios for targeted heat injection and extraction in an existing geothermal borehole field in Norway

This work presents the calibration, validation, and analysis of a borehole thermal energy storage (BTES) in building performance simulation using operational data from an existing borehole field in Kalnes, Norway. The data used in this study comprises the results of a thermal response test as well as operational data from the borehole field, which is used to cover the heating and cooling load of a hospital complex. The first part of this study focuses on the calibration and validation of the borehole field model using the IDA ICE software. Then, the validated model is used to explore the impact of different operational strategies in which the charging/discharging of the three sections of the borehole field are prioritized in different orders and compared to the most recent operational strategy. This analysis is carried out on a single year and a 20-year perspective to evaluate long-term temperature trends. This investigation aims to evaluate the current and future impacts of the existing operational strategy and whether it could be improved given that the real-life system struggles with below zero brine temperature at the end of the heating season. The simulation results show that the outgoing brine temperature in each borehole section is strongly dependent on the mass flow rate used in the BTES but that the temperature in an individual section had little impact on the neighboring one. When a section was prioritized by the control logic for heat extraction or injection (both in terms of order and mass flow), there was a notable increase or decrease in the outgoing brine temperature, indicating that it was possible to have targeted heat injection/extraction. In the 20-year operational horizon, the simulation results predicted a gradual warming trend of the outgoing brine temperature of approximately 1 °C due to the additional heat injected in all three sections and regardless of the scenario. The study shows that the most recently implemented operational strategy, in which all sections are charged and discharged simultaneously, is the most viable operation scenario for the borehole thermal energy storage at Kalnes, thus confirming previous findings in literature. Since none of the sections had a superior storage or heat regeneration capacity, prioritizing sections would only lead to more significant temperature swings in the ground. On the other hand, the current operation strategy leads to an overall higher temperature in the ground and reduces the risk of low outgoing brine temperaturespublishedVersio