Borehole Thermal Energy Storage emerges as a key solution in the context of decarbonizing heating and cooling and pushing district energy efficiency to new frontiers.
The integration of heat pumps, chillers, district energy initiatives, and Thermal Energy Storage systems is already established as a winning strategy for moving forward. In this scenario, a borehole system offers distinct opportunities for balancing seasonal energy loads, as well as reducing total CO2 emissions.
What is Borehole Thermal Energy Storage
Borehole Thermal Energy Storage (BTES) is a type of TES technology that is based on performing vertical holes drilled into the ground for storing and restoring thermal energy.
As such, BTES is able to store excess heat or cooling energy (generated during low-demand periods) and liberate it during peak-demand periods, benefitting from the fact that certain depths in soil are not influenced by seasonal temperature shifts.
BTES emerges as a key solution among thermal energy storage technologies for resolving the misalignment that often occurs between energy production and energy consumption. While all TES technologies address this issue, Borehole Thermal Energy Storage can present distinct advantages for certain projects, including lower initial costs and fewer environmental drawbacks.
All in all, BTES is praised for facilitating balance in energy loads, reducing operational costs, and significantly reducing the overall environmental impact of cooling and heating infrastructure.
How does Borehole Thermal Energy Storage work?
At the heart of BTES is a borehole heat exchanger, a system in charge of exchanging heat between the ground and a heat transfer fluid through a closed-loop system. This process is, in turn, facilitated by U-tubes filled with the heat transfer fluid.
Boreholes typically present a diameter of between 10-15 cm, and depths of between 20 to 300 meters. Additionally, if ground temperatures allow it, certain projects employ horizontal tubes.
Integration of BTES in District Heating and Cooling systems
Borehole Thermal Energy Storage presents various applications, with its incorporation into district heating and cooling infrastructure being particularly noteworthy.
In short, BTES represents another option for integrating Thermal Energy Storage into district energy, a combination that has been praised for a number of benefits:
- Lower overall cost of the installation, as it allows refrigeration plants to be designed for average loads, not peak loads.
- Supports the move towards low-temperature energy grids and 5th generation district heating and cooling, thus supporting greater efficiency.
- Reduced operational costs thanks to avoiding high electrical tariff periods during peak consumption.
- A boost to operational efficiency that helps reduce CO₂ emissions.
Applied to district energy, BTES allows for excess heat that is generated during the summer (for example, from solar panels) to be stored in boreholes and used to heat buildings in winter. Likewise, cold air from winter can be stored for summer cooling.
Borehole Thermal Energy Storage has been successfully integrated with solar thermal infrastructure, as well as waste heat sources, such as in urban wastewater heat recovery schemes.
Throughout all these models, careful design based on precise modeling and simulations must be ensured in order to successfully integrate Borehole Thermal Energy Storage. So much so that the system’s performance can be significantly enhanced when the following aspects are considered:
- The thermal conductivity and conditions of the surrounding rock mass
- Seasonal temperature shifts (atmospheric and ground temperatures)
- Thermal resistance of grouting material
- Thermal resistance of material selected for U-tubes
- Borehole configuration
- Potential energy demand parameters
- The network temperatures BTES will be operating with
Adequate design software and methodologies for modeling should ensure all these aspects are taken into account for any successful proposal. Additionally, the resulting model can consider the addition of supporting technologies for enhanced performance, such as heat pumps and systems for short-term thermal storage.
Sustainability and efficiency: the impact of BTES
BTES and the reduction of CO2 emissions
Borehole Thermal Energy Storage is being praised along with the rest of TES technologies for its capacities to significantly improve district energy infrastructure and thus boosting its decarbonizing potential.
Research initiatives are showing how adequate design can lead to reductions in emissions up to 43% compared to standard air-source systems, thanks to the optimization capacities brought along by BTES in district heating.
Additionally, Borehole Thermal Energy Storage is at the center of enabling an efficient incorporation of renewable, clean energy sources. This includes solar thermal energy initiatives, which have historically been limited by this energy source’s inherent intermittency. Combined with BTES, solar thermal energy can cover a high percentage of heating and cooling demand, overcoming this intermittency.
Urban waste heat models have also been successfully integrating Borehole Thermal Energy Storage, thus introducing a circular paradigm that further enhances this model’s sustainability potential. Urban sewage water and waste heat from industrial installations stand out as key options for powering district heating systems that benefit from implementing BTES, as an addition aiming at reducing uncertainty around the availability of energy in such projects.
The potential for a reduction in emissions and the incorporation of renewable and circular energy sources stand out as the key sustainability advantages of borehole systems. At the same time, the environmental impact of BTES on groundwater resources and ecosystems must be taken into account when planning and designing this infrastructure.
Efficiency and operational costs in District energy systems
One of the crucial operational cost reductions emerges from the capacity of BTES to decrease overall system temperatures in district energy infrastructure and heat pump technologies, leading to significant efficiency improvements.
But that’s not all: Borehole Thermal Energy Storage also reduces costs by enabling local energy storage.
Available research showcases this potential for cost reduction. For instance, a study analyzing a solar community that incorporated BTES in Finland concluded overall costs could be reduced by 20% in projects where large heat storage can be implemented.
ARANER: BTES system implementation
At ARANER, we’re at the forefront of cutting-edge thermal engineering that is shaping the heating and cooling initiatives of the future. A future that is both sustainable and cost-efficient, thanks to the intersection of advanced technologies, innovation, and thermal engineering expertise.
As such, our state-of-the-art TES technology solutions are leading the way for optimizing heating and cooling systems by reducing energy demands and decarbonizing infrastructure.
While Thermal Energy Storage is already considered a fine-tuned approach to improve district energy’s efficiency, at ARANER we’re committed to take this potential one step further in each of our projects. As such, our efforts are focused in bringing breakthrough innovation to TES technologies, and that includes the design and development of advanced Borehole Thermal Energy Storage initiatives.
As part of our TES technologies line, we offer a wide range of solutions. Sensible heat storage, latent heat storage and thermochemical storage are all in our catalog, which also includes innovative solutions such as phase-change materials.
In fact, we aim to provide value through our tailor-made solutions, which adjust to each project’s needs and potential, having sustainability and reducing operational and capital costs as priorities. Thus, we develop one-of-a-kind models for our clients, which include the world’s largest thermal energy storage system.
Among our key success stories is the development of a TES tank for the world-famous Qatar Football stadium. Our naturally-stratified 30,000 TR·h TES tank was able to meet peak load demands, accommodate small load variations, and act as a backup for chillers, all while meeting the project’s efficiency goals and guaranteeing peak load demand was covered.
The Farah Hospital, located in Amman, represents another success story of ARANER’s TES technology incorporation. As one of the largest hospitals in the Middle East, their planned expansion involved Thermal Energy Storage to enhance their efficiency. The project succeeded in achieving its goals, and the TES system was a crucial piece of the puzzle for accomplishing the project’s LEED Certification for Green Building.
All in all, continuous innovation in TES technologies is allowing for initiatives that take the potential of the TES approach to new frontiers. In this quest, precise calculations, design, and modeling set the right foundations for efficiency. This is precisely where our thermal engineering expertise comes in.
Want to learn more about Borehole Thermal Energy Storage, its potential for district energy, and whether or not it is the right approach for your project? At ARANER, we’re committed to pushing sustainability and efficacy in TES technologies to new frontiers. Get in touch with us and speak to our team about how we can help you.
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