A study on groundwater heat pump usage for district heating/cooling
Creators: name: Sezer, Taha
Publisher: name: University of Surrey
Year: 2023

description: Nearly half of Europe’s total energy consumption is contributed to buildings. Heating and
description: cooling consist of a significant part of this consumption. Considering climate change and the
description: countries’ measures towards greenhouse gas emissions (i.e., European energy and climate
description: targets of achieving net-zero greenhouse gas emissions by 2050), it is crucial to implement
description: renewable energy sources such as geothermal energy based heating and cooling systems at
description: district to city scale. Many district-level heating and cooling systems have been established in
description: Europe. However, just a limited number of them are geothermal energy based. One of the most
description: efficient ways of heating and cooling supply is to use geothermal energy stored in ground water.
description: Groundwater heat pumps (GWHP) are highly efficient, environmentally friendly and low-carbon
description: technology that can supply heating and cooling to buildings on small or large scales by
description: benefitting from low-temperature sources between 0°C and 30°C.<br>
description: <br>
description: GWHPs have been extensively researched in recent years to understand the impact of thermally
description: affected zones (TAZ) using numerical and experimental methods. However, studies on the
description: utilisation of GWHP at a district scale, particularly in chalk aquifers, are relatively rare. The
description: implementation of district-scale geothermal heat pump (GWHP) systems poses several
description: challenges, including dealing with the scale and complexity of the systems, addressing
description: geological variability, managing high initial investments, balancing energy demand and
description: supply, ensuring proper maintenance and monitoring, and mitigating potential environmental
description: impacts. These challenges require careful consideration and strategic planning to ensure the
description: successful deployment and sustainable operation of these systems. The development of TAZ
description: and system performance depend heavily on the characteristics of the aquifer. This study focuses
description: on one of the largest GWHP systems in a confined chalk aquifer, and examines thermal plume
description: development, system performance, and sustainability.<br>
description: <br>
description: This study evaluates various factors that affect GWHP system design and performance, such
description: as groundwater flow, injection, and extraction rates. The effects of variations in these factors
description: on TAZ development and system performance have not been fully examined and have not been
description: reported in the literature. Therefore, this study investigates their impact through laboratory-based
description: experimental examination and numerical investigation, considering various scenarios.<br>
description: <br>
description: The numerical investigation has been carried out considering a field study called Northern
description: Gateway Heat Network, located in Colchester, UK. The results indicate that the space heating
description: operation, cold water injection, creates a thermal plume that primarily develops around the
description: injection wells. Additionally, the results show that the thermal energy gained from the
description: groundwater is about 11% lower than the designed value. The numerical study suggests that
description: the system can also supply direct cooling for two months or longer every year if required, which
description: would extend thermal feedback time. The study also suggests that incorporating an aquifer
description: thermal energy storage (ATES) system would improve system efficiency and long-term
description: sustainability. The numerical study further reveals that the injection and extraction create a
description: significant drawdown around the wells, which should be carefully analysed as the water level
description: might drop below the submersible pump. The groundwater flow has a significant impact on
description: thermal plume development, although the hydraulic gradient at the site is relatively small.<br>
description: <br>
description: The experimental study results demonstrate that incorporating the ATES system significantly
description: increases efficiency. The increase in the injection and abstraction rates increases the thermal
description: plume dimension, leading to a greater change in abstraction temperature. The study also
description: highlights that the groundwater flow rate has a significant impact on thermal plume
description: development, as it spreads the thermal plume in the direction of the groundwater flow. The
description: research suggests that the groundwater flow, injection, and extraction rates must be taken into
description: account during the design stage of a GWHP system.<br>