Assessing District-Heating Sustainability – Case Studies of CO2 Mitigation Strategies and Environmental Cost Accounting
Doctoral thesis, 2012

District heating (DH) may play an important role in achieving the EU goal of a secure, competitive and sustainable energy supply. Integrated energy solutions based on technologies, such as biomass gasification for transport fuel, electricity and heat production and heat-driven absorption cooling, create new optimisation possibilities through the linkage between heat, power, cooling and transport fuel markets which may reduce the global warming contribution of the energy sector. With increasing focus on climate change impacts of greenhouse gas emissions, the environmental effects of other air pollutants should not be neglected. To achieve both a competitive and a sustainable energy supply, it is necessary to integrate environmental considerations into economic policies. Through accounting for external costs of air pollution in energy system modelling and analysis, sustainability aspects may be integrated into DH assessments. The aim of this thesis is to develop, apply and evaluate methodologies for assessing conventional and new technology solutions in a DH system; the assessments are made from a DH perspective with respect to two factors – cost-effectiveness and environmental impacts – which are either assessed separately or integrated through external cost accounting. Various CO2 mitigation strategies are evaluated with regard to the robustness of the DH system in meeting future developments of energy market prices and policies. The studies are performed using a systems approach by using the simulating DH supply model MARTES as applied to the DH system of Göteborg, Sweden. This thesis concludes that the integration of biomass gasification technology and absorption cooling technology in DH systems has the potential for cost-effective CO2 emission reduction, in line with other EU goals to increase the share of renewable sources in energy use and to increase energy efficiency. Accounting for external costs of not only climate change but also other environmental impacts of air pollution may strongly influence least-cost operations of DH systems, especially in systems that include combined heat and power plants. However, case study results show that effects on cost-effectiveness of annual DH generation are generally minor. Applying life cycle thinking to economic and environmental analyses of energy systems proves to be of great importance to the outcome and reliability of DH assessments. This thesis emphasises the importance of paying attention to environmental impacts of airborne emissions other than CO2, including emissions from upstream processes. As life cycle processes, pollutants and impact categories are covered in external cost accounting to a greater extent, the more accurate the results will be, while the accounting process will be more complex and time-consuming. However, this thesis illustrates that an external cost accounting based on a simplified approach may be as accurate as employing a more comprehensive approach.

absorption cooling

biomass gasification

bio transport fuel

policy instruments

carbon dioxide

external costs

combined heat and power

district heating and cooling

HA3-salen, Hörsalsvägen 4, Göteborg
Opponent: Prof. Henrik Lund, Department of Development and Planning, Aalborg Universitet, Denmark


Elsa Fahlén

Chalmers, Energy and Environment, Energy Technology

Befolkningsökning och ekonomisk tillväxt resulterar i ett kraftigt ökande globalt energibehov med ökade koldioxidutsläpp som följd, något som kan leda till förödande klimatförändringar. Genom möjligheten att utnyttja energiinnehållet i samhällets restprodukter, såsom brännbart avfall och spillvärme, kan fjärrvärmesystem bidra till att minska behovet av primära bränslen och undvika emissioner från förbränning av dessa. Avhandlingen visar att integration av biobränsleförgasning för drivmedel-, el- och värmeproduktion kan leda till reducerade koldioxidutsläpp och förbättrad ekonomi i ett svenskt fjärrvärmesystem. Istället för att kyla bort överskottsvärme från värmegenerande processer under perioder med lågt värmebehov kan överskottsvärmen nyttjas till att driva absorptionskylmaskiner och därmed ersätta eldriven kylproduktion, något som skulle kunna begränsa klimatpåverkan av ett väntat ökat kylbehov. Förutom klimatpåverkan av utsläpp av koldioxid och andra växthusgaser bidrar energiaktiviteter till luftföroreningar som har en negativ påverkan på ekosystem och människors hälsa. I avhandlingen tillämpas en metod för att ta hänsyn till de skadekostnader som uppstår på grund av luftutsläpp från hela livscykeln. Dessa kostnader inkluderas i den ekonomiska modelleringen av ett fjärrvärmesystem för att bedöma befintliga styrmedels inverkan på produktion, kostnadseffektivitet och miljöprestanda. Metoden är komplex, men avhandlingen visar att en förenklad metod kan vara tillräcklig.

Population and economic growth result in steadily increasing world energy demand and global carbon dioxide emissions, something that may cause catastrophic climate change impacts. By utilising the energy content in waste products from society, such as waste and excess heat, district-heating systems can contribute to reduce the need of primary fuels at the same time as emissions from combustion of other fuels can be avoided. This thesis shows that integrating biomass gasification for transport fuel, electricity and heat generation into a Swedish district-heating system may cost-effectively lead to reduced carbon dioxide emissions. Instead of wasting excess heat from heat-generating processes during low demand periods, the excess heat can be utilised in heat-driven absorption chillers to replace electricity-driven cooling generation and, thereby, lower climate change impacts from expected increase in cooling demand. Apart from climate change impacts of emissions of carbon dioxide and other greenhouse gases, energy activities contribute to air pollution that causes damage on ecosystems and human health. This thesis applies a method to account for damage costs of air pollution from the entire life cycle of district-heating generation to assess how policy instruments influence the production, cost-effectiveness and environmental impacts. The method is complex, but this thesis evidences that a simplified approach may be sufficient.

Driving Forces

Sustainable development

Subject Categories

Other Engineering and Technologies not elsewhere specified

Areas of Advance




Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie

HA3-salen, Hörsalsvägen 4, Göteborg

Opponent: Prof. Henrik Lund, Department of Development and Planning, Aalborg Universitet, Denmark

More information