lab271 \ academic rigor, plugged in

Research

Published, reviewed, repeatable. Peer-reviewed work at the intersection of software engineering, sustainability and digital transformation, plus the articles we write along the way.

sustainable software engineering \ digital transformation \ it governance and sourcing \ ai research and practice

e ≈ 2.71828 \ the growth constant

papers \ peer-reviewed

Published work

2026ICSE-SEIP 2026

Green LLM Techniques in Action: How Effective Are Existing Techniques for Improving the Energy Efficiency of LLM-Based Applications in Industry?

Pelin Rabia Kuran, Rumbidzai Chitakunye, Vincenzo Stoico, Ilja Heitlager, Justus Bogner

\doi\pdf

Abstract

The rapid adoption of large language models (LLMs) has raised concerns about their substantial energy consumption, especially when deployed at industry scale. While several techniques have been proposed to address this, limited empirical evidence exists regarding the effectiveness of applying them to LLM-based industry applications. To fill this gap, we analyzed a chatbot application in an industrial context at Schuberg Philis, a Dutch IT services company. We then selected four techniques, namely Small and Large Model Collaboration, Prompt Optimization, Quantization, and Batching, applied them to the application in eight variations, and then conducted experiments to study their impact on energy consumption, accuracy, and response time compared to the unoptimized baseline. Our results show that several techniques, such as Prompt Optimization and 2-bit Quantization, managed to reduce energy use significantly, sometimes by up to 90%. However, these techniques especially impacted accuracy negatively, to a degree that is not acceptable in practice.

2026 IEEE/ACM 48th International Conference on Software Engineering (ICSE-SEIP '26), Rio de Janeiro, Brazil, 12 pages

BibTeX
@inproceedings{Kuran2026,
  author = {Kuran, Pelin Rabia and Chitakunye, Rumbidzai and Stoico, Vincenzo and Heitlager, Ilja and Bogner, Justus},
  title = {Green LLM Techniques in Action: How Effective Are Existing Techniques for Improving the Energy Efficiency of LLM-Based Applications in Industry?},
  booktitle = {2026 IEEE/ACM 48th International Conference on Software Engineering: Software Engineering in Practice (ICSE-SEIP '26)},
  pages = {554--565},
  year = {2026},
  publisher = {ACM},
  doi = {10.1145/3786583.3786896}
}

2025Designs

Navigating Digital Transformation in Asset-Intensive Companies: A Process Model Informed by Design Science

Ilja Heitlager, Bernard Jenniskens, A. Georges L. Romme

\doi\pdf

Abstract

Companies in asset-intensive industries, such as aviation and railways, face unique digital transformation challenges due to the misalignment between the rapid evolution of digital technologies and decades-long asset lifecycles. This paper investigates how asset-intensive companies can systematically integrate digital technologies, while fully complying with regulatory constraints and safety requirements. We employ a design science approach in a study of Nederlandse Spoorwegen (NS), the Dutch national railway operator, focusing specifically on the implementation of AI-driven CCTV systems. We develop six design propositions and the Iterative Development & Adoption Model (IDAM) that operationalizes market maturity assessment through market readiness levels to guide make-or-buy transitions across four iterative phases: ideate, assess, realise, and review.

Designs 2025, 9(6), 136

BibTeX
@article{Heitlager2025,
  author = {Heitlager, Ilja and Jenniskens, Bernard and Romme, A. Georges L.},
  title = {Navigating Digital Transformation in Asset-Intensive Companies: A Process Model Informed by Design Science},
  journal = {Designs},
  volume = {9},
  number = {6},
  pages = {136},
  year = {2025},
  doi = {10.3390/designs9060136}
}

2024ICSA 2024

Experimental Evaluation of Energy Efficiency Tactics in Industry: Results and Lessons Learned

Markus Funke, Patricia Lago, Esther Adenekan, Ivano Malavolta, Ilja Heitlager

\doi\pdf

Abstract

Integrating (and evaluating) energy efficiency tactics into daily industrial practice is challenging. This paper addresses the experimental evaluation of energy efficiency tactics in industrial contexts. Based on different real-world scenarios, we assess five energy efficiency tactics for cloud-based software through individual experiments conducted across two companies. The results of the experiments show significant improvements in energy efficiency for three tactics, with two others showing enhanced efficiency albeit without statistical significance. Our results could guide practitioners in selecting and applying the most suitable tactic for their individual context.

IEEE 21st International Conference on Software Architecture (ICSA), Hyderabad, India, pp. 170-181

BibTeX
@inproceedings{Funke2024,
  author = {Funke, Markus and Lago, Patricia and Adenekan, Esther and Malavolta, Ivano and Heitlager, Ilja},
  title = {Experimental Evaluation of Energy Efficiency Tactics in Industry: Results and Lessons Learned},
  booktitle = {2024 IEEE 21st International Conference on Software Architecture (ICSA)},
  pages = {170--181},
  year = {2024},
  doi = {10.1109/ICSA59870.2024.00024}
}

2024GREENS @ ICSA-C 2024

Unveiling Key Performance Indicators for the Energy Efficiency of Cloud Data Storage

Pouyeh Banijamali, Iffat Fatima, Patricia Lago, Ilja Heitlager

\doi\pdf

Abstract

This paper explores metrics to evaluate the energy efficiency of cloud data storage and represents them as Key Performance Indicators (KPIs) for organizational monitoring. We present a framework for systematically identifying, categorizing, and applying KPIs that enable organizations to monitor and optimize the energy efficiency of their cloud storage infrastructure.

8th International Workshop on Green and Sustainable Software (GREENS), at ICSA-C 2024, Hyderabad, India, pp. 222-229

BibTeX
@inproceedings{Banijamali2024,
  author = {Banijamali, Pouyeh and Fatima, Iffat and Lago, Patricia and Heitlager, Ilja},
  title = {Unveiling Key Performance Indicators for the Energy Efficiency of Cloud Data Storage},
  booktitle = {2024 IEEE 21st International Conference on Software Architecture Companion (ICSA-C)},
  pages = {222--229},
  year = {2024},
  doi = {10.1109/ICSA-C63560.2024.00047}
}

2022ICT4S 2022

Architectural Tactics to Optimize Software for Energy Efficiency in the Public Cloud

Sophie Vos, Patricia Lago, Roberto Verdecchia, Ilja Heitlager

\doi\pdf

Abstract

From a cloud consumer perspective, migrating software to the cloud promises to improve quality attributes like availability, scalability, flexibility, and carbon efficiency. However, this migration might be misinterpreted as delegating the fulfillment of these QAs to the cloud provider. This paper started addressing this problem by defining, or rethinking, architectural tactics for energy efficiency. We provide a catalog of tactics that software architects can apply to optimize their cloud-based applications for energy efficiency.

2022 International Conference on ICT for Sustainability (ICT4S), Plovdiv, Bulgaria, pp. 77-87

BibTeX
@inproceedings{Vos2022,
  author = {Vos, Sophie and Lago, Patricia and Verdecchia, Roberto and Heitlager, Ilja},
  title = {Architectural Tactics to Optimize Software for Energy Efficiency in the Public Cloud},
  booktitle = {2022 International Conference on ICT for Sustainability (ICT4S)},
  pages = {77--87},
  year = {2022},
  doi = {10.1109/ICT4S55073.2022.00019}
}

2010Global Sourcing 2010

Evolving Relationship Structures in Multi-sourcing Arrangements: The Case of Mission Critical Outsourcing

Ilja Heitlager, Remko Helms, Sjaak Brinkkemper

\doi\pdf

Abstract

This paper explores the evolution of relationship structures in multi-sourcing arrangements for mission critical IT services. Based on a longitudinal case study at a major financial services provider, we analyze how relationship structures between client and multiple vendors develop over time, identifying key patterns and governance mechanisms that enable successful multi-vendor orchestration in high-stakes environments.

4th International Workshop on Global Sourcing, Zermatt, Switzerland. Lecture Notes in Business Information Processing, vol 55, pp. 168-185. Springer

BibTeX
@inproceedings{Heitlager2010,
  author = {Heitlager, Ilja and Helms, Remko and Brinkkemper, Sjaak},
  title = {Evolving Relationship Structures in Multi-sourcing Arrangements: The Case of Mission Critical Outsourcing},
  booktitle = {Global Sourcing of Information Technology and Business Processes},
  series = {Lecture Notes in Business Information Processing},
  volume = {55},
  pages = {168--185},
  year = {2010},
  publisher = {Springer},
  doi = {10.1007/978-3-642-15417-1_10}
}