Sweco carried out an extensive survey on geothermal heat potential in Helsinki – first of its kind in Finland

The City of Helsinki is currently in the process of preparing a new underground master plan. By 2050, Helsinki will have 200,000 more residents than it does now, which must be taken into account in all energy and land use planning. This is why the City commissioned Sweco to carry out Finland’s first extensive survey on the potential of geothermal heat.

The City of Helsinki aims to reduce its emissions by 60% by 2030. Geothermal heat has also been integrated into the Carbon Neutral Helsinki 2035 Action Plan.

“Carrying out a survey on geothermal heat became necessary while we were preparing the planning principles and policies of the new underground master plan,” says Project Manager Pekka Leivo from the City of Helsinki’s Technical and Economic Planning Unit.

The purpose of the geothermal heat survey is to steer the planning of geothermal wells in Helsinki. One of the unanswered questions was how the utilisation of geothermal heat relates to the inner city’s constantly growing need for underground construction. “We also assessed how much of the city’s total heating needs could be covered with geothermal heat,” states land use specialist, Architect Maritta Heinilä from Sweco.

New kind of survey required multidisciplinary expertise

A survey of geothermal heat potential as extensive as this has never been prepared before, and the underground master plan is only the second of its kind: the first was prepared for the City of Helsinki in 2011. The information gathering was multi-staged and -layered.

“In this type of work, it is essential to examine things from multiple perspectives. Sweco has very broad subject matter expertise in regard to land use planning and the background surveys needed for it,” Leivo says.

The Helsinki’s new master plan defines further planning of underground spaces, such as tunnels, and how to densify the urban structure in Helsinki by transferring some functions underground.

“The aim is to increase the use of underground space. The proposition of the new master plan is completed at the end of this year,” adds Eija Kivilaakso, Unit Manager from the City of Helsinki, responsible of the new master plan.

The land use planning included environmental impact assessment and geographic information surveys. In addition to this, Sweco’s experts also sought to resolve legal issues. “The equal treatment of landowners is very important in the planning of geothermal heat systems, as it is in all land use planning,” Heinilä emphasises.

The survey also required extensive planning expertise in regard to geothermal heat and energy systems. “We carried out energy simulations and assessed total heating needs by examining single-family houses, offices and blocks of flats from different eras in different parts of Helsinki,” says Sweco’s Lifecycle Design Project Manager Niina Laasonen.

The planning of geothermal wells was approached from a fresh angle. “The simulation of geothermal heat fields usually progresses one building at a time. Our survey, however, covered all of Helsinki, due to which we decided to examine entire blocks or residential areas at a time,” says geothermal heating system specialist Mika Penttinen.

Greatest geothermal heat potential found in the city’s outskirts

Combining building services data with geographic information allowed the space requirements of geothermal heat systems to be compared to the objectives of Helsinki’s master plan. This revealed the places with sufficient space for geothermal heat systems.

“The greatest potential lies in single-family house areas,” Laasonen says. The efficient building necessitated by the City’s master plan is often at odds with the spatial requirements of geothermal heat systems. “In the inner city, building needs are so great that there is simply no room for geothermal heat systems. The same problems can be seen underground.”

According to the survey, the optimal approach would be to consider energy production at the block level and also reserve space in the master plan for local energy solutions. “Large blocks could have their own geothermal heat centres, similar to transformer substations,” Heinilä says. “Public park areas could also be used for the more permissive placement of geothermal wells.”

“It was an important discovery for us that focus should be shifted from property-specific geothermal heat systems to larger, local ones,” Leivo states. “The information on the impact of building stock of varying ages on energy consumption is also important in regard to further planning.”

The building of geothermal wells must be started now

According to the survey, geothermal heat systems can help achieve Helsinki’s climate goals and produce 14–18% of the city’s heating needs by 2035. However, there is only enough geothermal heat capacity for this if heating needs are successfully kept at the current level.

“If heating needs increase, the building of the necessary geothermal wells is estimated to take 18 years, in which case they will not be completed in time to contribute to the Carbon Neutral Helsinki objectives,” Laasonen says. In other words, harnessing the potential of geothermal heat requires immediate action. “It is crucial to improve the energy efficiency of buildings and start the large-scale building of geothermal wells as early as this year.”

Have you already found Sweco’s Urban Insight reports on energy transition? Read more!