The potential of using groundwater as a heating/cooling energy source in the Vaasa city region of Finland

Groundwater accounts for 1.69% (0.76% as fresh and 0.93% as saline) of the total percentage of water in the world and comprises 99% of the earth's available water. The effects of climate change on the temperature increase in groundwater make it much more useful as a heat source, if it is not deeply located or near the ground surface. Hence there is a growing interest in extracting and storing thermal energy from groundwater and aquifers to contribute to the global clean renewable energy transition. In the Vaasa region of western Finland, the current knowledge of groundwater and unconfined aquifers is limited. To fill in this gap to examine and deepen the knowledge of groundwater and aquifer investigation techniques, defining groundwater effects on the energy borehole, and understanding the aquifers and groundwater, the literature review is conducted based on Tritonia library resources and internet documents using a systematic literature review method. A case study was initiated to explore the appearance of groundwater and aquifers during the drilling operations. It is expected that there is a connection between the aquifers under the sea and the groundwater on land. The possibilities of using groundwater as a heat energy source with groundwater energy utilization systems (GEU) are investigated. The key contribution of this paper is the critical assessment of the factors influencing the drilling process of boreholes that can be generalized to other regional sites. Our review shows that groundwater quality protection is of essential value because of its ecological, hydrological and economic significance.