Could ground heat and geothermal energy be the answer to climate change prevention and energy demand?

Abstract

Global warming has caused and will continue to cause an increasing amount of extreme weather phenomena. Science has shown that the risks for irreversible and catastrophic changes will rise considerably if the climate warms up by more than 1.5 or even 2 degrees Celsius. The City of Helsinki bears its responsibility in mitigating climate change. The aim is to make Helsinki carbon neutral by 2035. The operating environment of energy produced by ground heat wells is changing in Finland - recently the interest in boring large energy well fields and deeper energy wells has increased considerably. There are two types of geothermal energy wells: wells based on a closed loop system and EGS wells, operating with the help of a network of clefts in the bedrock. EGS power stations are always associated with an earthquake risk, as they alter the stress state in the bedrock. The traditional ground heat wells are currently more cost-effective in Finland than the geothermal energy wells when their construction costs are compared with the value of the energy generated by them. The construction costs of geothermal energy solutions will most likely decrease along with future mass production. Geothermal energy wells will also bring many benefits compared with ground heat wells. In terms of underground construction, it is better to have fewer boreholes. Unlike traditional ground heat wells, geothermal energy will never run short over the years. The energy production of ground heat wells is typically calculated for a period of 20 to 50 years. Cooling also known as recharging will increase the lifespan of a ground heat system for some decades. The energy production of a two-kilometre deep geothermal energy well in the bedrock of Helsinki has been modelled for the next 1,000 years. The energy production of a two-kilometre deep geothermal energy well will initially reach 800 MWh annually and still be as high as 640 MWh annually after 1,000 years. Helsinki also aims to utilise renewable energy on a regional basis, and not only for individual building lots. Our intention is to integrate the utilisation of ground heat and geothermal energy as part of land-use planning. The pilot sites will include both new production and complementary development. This work is part of the background research for the Helsinki Underground Master Plan 2021.