26.4.2017

Science Blog: Groundwater as an Energy Resource in Finland

Teksti:
Teppo Arola, Chief Expert

GTK’s Chief Expert Teppo Arola tells in this blog text about groundwater energy potential in Finland.

Groundwater can be seen as an option for renewable energy utilisation and not only a source of individual or municipal drinking water. Finland has multiple groundwater reservoirs that are easily exploitable, but groundwater energy is not commonly used for renewable energy production.

For this blog, I would like to briefly highlight the outcomes of my doctoral dissertation, which was published in December 2015. The articles of the thesis were published in 2014 and 2016. The purpose of the work was to explore the groundwater energy potential in Finland, a region with low temperature groundwater. Firstly, the national groundwater energy potential was mapped for aquifers classified for water supply purposes that are under urban or industrial land use. Secondly, the urbanisation effect on the peak heating and peak cooling power of groundwater was investigated for three Finnish cities, and finally, the long-term groundwater energy potential was modelled for 20 detached houses, 3 apartment buildings and a shopping centre. Hydrological and thermogeological data were used together with accurate data on the energy demands of buildings. Hence, this study connected scientific information on hydro- and thermogeology with the energy efficiency of buildings to produce accurate information concerning groundwater energy utilisation.

Approximately 20% to 40% of annually constructed residential buildings could be heated utilising groundwater from classified aquifers that already are under urban land use in Finland. These aquifers contain approximately 40 to 45 MW of heating power. Urbanisation increases the heating energy potential of groundwater. This is due anthropogenic heat flux to the subsurface, which increases the groundwater temperatures in urbanised areas. The average groundwater temperature was 3 to 4 °C higher in city centres than in rural areas. Approximately 50% to 60% more peak heating power could be utilised from urbanised compared with rural areas. Groundwater maintained its long-term heating and cooling potential during 50 years of modelled operation in an area where the natural groundwater temperature is 4.9 °C. Long-term energy utilisation created a cold groundwater plume downstream, in which the temperature decreased by 1 to 2.5 °C within a distance of 300 m from the site. Our results demonstrate that groundwater can be effectively utilised down to a temperature of 4 °C.

Groundwater can form a significant local renewable energy resource in Finland. It is important to recognise and utilise all renewable energy reservoirs to achieve the internationally binding climatological targets of the country. Groundwater energy utilisation should be noted as one easily exploitable option to increase the use of renewable energy resources in a region where the natural groundwater temperature is low. The methods presented in this thesis can be applied when mapping and designing groundwater energy systems in nationwide- to property-scale projects. Accurate information on hydro- and thermogeology, together with the energy demands of buildings, is essential for successful system operation.

See full text: Arola T. 2015. Groundwater as an energy resource in Finland. University of Helsinki, Department of Geosciences and Geography A36. Unigrafia. Helsinki. https://helda.helsinki.fi/handle/10138/158293

Figure 1. Potential aquifers for groundwater energy utilisation in Finland. Each dot represents a single aquifer. The dot colour indicates the categorized amount of heat (G). Numbers from 1 to 20 indicate the location of the 20 aquifers with the largest potential. (Basemap database © Esri, DeLorme, Navteq and Natural Earth). Reprinted with permission from Springer.

 

With this picture I aim to remind the reader to think of renewable energy, local energy and sustainable development together with flowing groundwater. Groundwater can provide a solution for all three of these wonderful topics.

 

Teppo Arola

Teksti: Teppo Arola

Dr Teppo Arola started to work as a chief expert at the geoenergy unit of the Geological Survey of Finland on 1 September 2016. Before joining the Geological Survey, Teppo worked for 17 years for the consulting company Golder Associates Oy. His research topics are related to geothermal energy utilisation and development.