Hanasaari B is a coal-fired cogeneration power plant in Kalasatama, Helsinki. The plant started operation in 1974 and, after 50 years of operation, is being decommissioned in 2023. Decommissioning the plant is a vital step in the City of Helsinki’s ambitious goal of becoming carbon neutral by 2035. Due to its large size and architectural quality, Hanasaari B has become a landmark in the Helsinki skyline and the heart of residential developments in the Kalasatama area. The present vision involves preserving architect Timo Penttilä’s original buildings – including subsequent additions and alterations – as well as new compositions.
Timo Penttilä successfully lightened the appearance of the massive power plant by placing the heaviest functions at the centre of the plant. He grouped secondary facilities such as offices, coal conveyors and service buildings in smaller units around the generator building. As a result, the cubic structures focusing on vertical façade surfaces rise like a great urban sculpture in Helsinki’s industrial cityscape.
Energy production and consumption, as well as sustainability, form the common threads for future use of the power station and connect it to the neighbouring Energyblock. The landside buildings, facing the city will be conserved to a large extent. The seaside buildings will be demolished and replaced with modern constructions. Existing and new additions form an outer ring within the existing building perimeter. The additions are placed to keep balance with the existing symmetrical composition, assuring the value of Penttilä’s work. The height limit for the new structures is tied to approximately half of the central chimney’s height, a structure that must be preserved under all circumstances.
Mixed use of the Hanasaari B structures guarantees a sustainable future for the premises in two ways: firstly, diverse functions address a wider audience and therefore find a broader consensus. Secondly, this strategy allows realisation in stages with different stakeholders and developers. It is a flexible approach adaptable to changing external conditions. Demolition, additions and new structures can be carried out step by step at the speed most appropriate to develop Kalasatama.
1. Saving and preserving old power plant as a city quarter composition Opening the full length of the ground floor to the street edge. This will make the quarter and buildings approachable and to create diverse ways to accesses to the core space.
2. Saving and preserving old Timo Penttilä Power plant as a city quarter composition Placing new volumes on top of and in the voids between the power plant structures. This will strengthen the landmark and its silhouette.
3. Partly perserving the power plant Preserving the structural skeletons of the larger buildings and replacing their closed façade surfaces with modern materials. This will ensure a flexible and contemporary functions.