Potentials and effects of electricity cogeneration via ORC integration in small-scale biomass district heating system

Abstract

This study explores the potential and impact of electricity cogeneration using Organic Rankine Cycle (ORC) integrated with small-scale biomass boilers within district heating systems. An analysis is conducted on a 3 MW_th biomass-fired district heating plant in southern Sweden. Process monitoring data, collected over a one-year period from the plant, serves as the basis for simulation and analysis. The study examines operational changes and fuel usage at a local level, together with an extension to a regional scale considering both short-term and long-term energy system implications. The results show that integrating a 200 kW_e ORC unit with the existing boiler having a flue gas condenser is cost-optimal and could cogenerate approximately 1.1 GWh electricity annually, with a levelized electricity cost of €64.4 per MWh. This is equivalent to a system power-to-heat ratio of 7.5%. From a broader energy system perspective, this efficient integration could potentially reduce CO₂ emissions by 234-454 tons per year when the saved energy locally is used to replace fossil fuels in the energy system, depending on how biomass is utilized and what type of fossil fuels are replaced. Increasing installed capacity of ORC unit to maximize electricity co-generation could result in a carbon abatement cost ranging from €204 to €79 per ton CO₂. This cost fluctuates depending on the installed capacity, operation of the ORC units, and prevailing electricity prices. The study highlights the trade-off between financial gains and CO₂ emission reductions, underscoring the complex decision-making involved in energy system optimization.

Keywords

Biomass conversion / Small-scale boiler / Organic rankine cycle / District heating system / Primary energy use / Electricity cogeneration / GHG emissions

CRediT authorship contribution statement

Truong Nguyen: Writing - review & editing, Writing - original draft, Visualization, Validation, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Leteng Lin: Writing - review & editing, Writing - original draft, Visualization, Formal analysis, Data curation.

Disclaimer

The content of this publication is the sole responsibility of its authors and can under no circumstances be regarded as reflecting the position of the European Union, the Managing Authority or the Joint Secretariat of the Interreg South Baltic Programme 2021-2027.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We thank ITK Envifront AB, particularly Fredrik Albertson and Staffan Jansson, for their input on scrubber operation data. We also appreciate the support from Lessebo Fjärrvärme, with special thanks to Mike Lundström and Mikael Fredh for granting us access to the system and providing valuable process data.

The work of Dr. Leteng Lin was partially financed and supported by the Swedish Knowledge Foundation (grant number 20190090) and the DecarbonDHS project (grant number of STHB.02.01-IP.01-0009/23) co-financed from the Interreg South Baltic Programme 2021–2027 through the European Regional Development Fund.

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