Public defence in Mechanical Engineering, M.Sc. Tomi J. Lindroos

Replacing fossil fuels in district heating – modelling investments, impacts and uncertainties

Heating and cooling consume half of the EU's final energy, with only 20% from renewable sources. Despite ambitious 2030 climate targets, progress has been slow, with renewable share only increasing from 17% to 23% between 2010 and 2020. The current rate seems insufficient to meet 2030 targets, especially in Central Europe, requiring urgent action to boost decarbonization. Nordic and Baltic countries use less fossil fuel for heating due to higher DH shares and larger biomass resources. 

District heating and cooling can significantly accelerate decarbonization by integrating diverse energy solutions, managing demand, and balancing electricity generation. This study examines the development of DH as part of energy system decarbonization, focusing on technology options, system-level impacts, investment uncertainties, and local conditions. It includes five publications modeling case studies in different regions and cities, analyzing decarbonization pathways, system integration, biomass value chains, and reducing dependence on imported fossil fuels and electricity.

The main outcomes of the research were following: 

Bioenergy use in the EU has grown but is limited by decreasing forest sinks and biodiversity concerns. Even biomass-rich countries like Finland cannot fully decarbonize their DH sectors with domestic biomass alone. While biomass can replace fossil fuels in smaller DH systems, larger systems require a range of different solutions. 

Electrification, including direct electric heating and heat pumps, offers a scalable route for decarbonizing district heating. These technologies can take advantage of fluctuating electricity prices and provide balancing capacity for variable renewable energy sources. Excess heat from new industrial processes and hydrogen production can also be utilized, though challenges remain, such as distance between heat sources and DH grids. 

Accelerated emission reduction targets could change the decarbonization pathway. Emerging technologies like nuclear heat only reactors, bioenergy with carbon capture, and hydrogen-boosted biorefineries show promise but face challenges with technology development, legislation, and public acceptance. Requirement for rapid decarbonization targets may limit the investments of these technologies.

Doctoral Student: Tomi J. Lindroos

Opponent: Prof. Eeva-Lotta Apajalahti, LUT

Custos: Prof. Sanna Syri, Aalto University School of Engineering, Department of Mechanical Engineering

The public defense will be organized in Lecture Hall E, Otakaari 1

The thesis is publicly displayed 10 days prior to the defense in the publication archive Aaltodoc of Aalto University. 

Contact information of doctoral student:

Doctoral theses in the School of Engineering: https://aaltodoc.aalto.fi/handle/123456789/49