Publications
Publications
The value of storage in electricity distribution: The role of markets
DL, D. Deka, S. Shin, arXiv Preprint, 2025.
Summary: Electricity distribution companies deploy battery storage to defer grid upgrades by reducing peak demand. In deregulated jurisdictions, such storage often sits idle because regulatory constraints bar participation in electricity markets. Here, we develop an optimization framework that, to our knowledge, provides the first formal model of market participation constraints within storage investment and operation planning. In a Massachusetts case study, we find that market participation could deliver similar savings as peak demand reduction.
Themes: Policy optimization, Stochastic optimization.
ExaModelsPower.jl: A GPU-compatible modeling library for nonlinear power system optimization
S. Johnson, DL, S. Shin, F. Pacaud, arXiv Preprint, 2025. Submitted to Electric Power Systems Research.
Summary: As GPU-accelerated mathematical programming techniques mature, there is growing interest in utilizing them to address the computational challenges of power system optimization. This paper introduces an open-source modeling library for creating GPU-compatible nonlinear AC optimal power flow models and provides a high-level interface that automatically generates all necessary callback functions for GPU solvers. The library is designed for large-scale problem instances, which may include multiple time periods and security constraints. Our results show that GPU solvers can deliver up to two orders of magnitude speedups compared to alternative tools on CPU for problems with more than 20,000 variables.
Themes: Large-scale optimization.
Storage participation in electricity markets: Arbitrage and ancillary services
DL, L. Coté, X. A. Sun, arXiv Preprint, 2025.
Summary: Electricity storage is used for intertemporal price arbitrage and for ancillary services that balance unforeseen supply and demand fluctuations via frequency regulation. We present an optimization model that computes bids for both arbitrage and frequency regulation and ensures that storage operators can honor their market commitments at all times for all fluctuation signals in an uncertainty set inspired by market rules. This requirement, initially expressed by an infinite number of nonconvex functional constraints, is shown to be equivalent to a finite number of deterministic constraints. The model can account for intraday trading and, with a solution time of under 5 seconds, may serve as a building block for more complex trading strategies.
Themes: Policy optimization, Stochastic optimization.
Alternating methods for large-scale AC optimal power flow with unit commitment
M. Brun, T. Lee, DL, X. Chen, X. A. Sun, arXiv Preprint, 2025. Submitted to Operations Research.
Summary: Security-constrained unit commitment with alternating current optimal power flow (SCUC-ACOPF) is a central problem in power grid operations that optimizes commitment and dispatch of generators under a physically accurate power transmission model while encouraging robustness against component failures. SCUC-ACOPF requires solving large-scale problems that involve multiple time periods and networks with thousands of buses within strict time limits. We propose a decomposition scheme and a penalty alternating direction method to find high-quality solutions to this problem. To evaluate our algorithm, we use large-scale test cases from Challenge 3 of the U.S. Department of Energy's Grid Optimization Competition that resemble real power grid data under a variety of operating conditions and decision horizons. The experiments yield feasible solutions with an average optimality gap of 1.33%, demonstrating that our approach generates near-optimal solutions within stringent time limits.
Themes: Large-scale optimization.
F. Lopez Aguilar, DL, F. Vuille, D.B. Müller, Nature Communications, 2024. Featured in Anthropocene Magazine.
Summary: Based on dynamic material flow analysis, we show that equipping around 50% of electric vehicles with vehicle-to-grid or reusing 40% of electric vehicle batteries for second life each have the potential to fully cover the European Union’s need for stationary storage by 2040. This could reduce total primary material demand from 2020–2050 by up to 7.5% and 1.5%, respectively, which could ease geopolitical risks and increase the European Union’s energy and material security.
Themes: Material flow analysis, Policy optimization.
Reliable frequency regulation through vehicle-to-grid: Encoding legislation with robust constraints
DL, F. Vuille, D. Kuhn, Manufacturing & Service Operations Management, 2024. INFORMS ENRE 2022 Best Student Paper Award.
Summary: We formulate a robust optimization problem that maximizes a vehicle owner’s expected profit from selling primary frequency regulation and guarantees that market commitments are met at all times for all frequency deviation trajectories in a functional uncertainty set that encodes applicable legislation. Faithfully modeling the energy conversion losses during battery charging and discharging renders this optimization problem nonconvex. By exploiting a total unimodularity property of the uncertainty set and an exact linear decision rule reformulation, we prove that this nonconvex robust optimization problem with functional uncertainties is equivalent to a tractable linear program. We find that the prevailing penalties for nondelivery of promised regulation power are too low to incentivize vehicle owners to honor the delivery guarantees given to grid operators.
Themes: Policy optimization, Stochastic optimization.
Frequency regulation with storage: On losses and profits
DL, F. Vuille, D. Kuhn, European Journal of Operational Research, 2024.
Summary: Because of charging and discharging inefficiencies, storage operators lose energy on average when providing frequency regulation. We express the loss as an implicit function of the regulation power and show that it is decreasing in roundtrip efficiency and increasing in frequency dispersion. We find that the profits from frequency regulation over the lifetime of energy-constrained storage devices are roughly inversely proportional to the length of time for which regulation power must be committed.
Themes: Policy optimization, Stochastic optimization.
Vehicle-to-Grid for Reliable Frequency Regulation
DL, PhD Thesis, 2022. EPFL Thesis distinction award.
Themes: Policy optimization, Stochastic optimization.
A general framework for stock dynamics of populations and built and natural environments
DL, R.G. Billy, F. Vásquez, D.B. Müller, Journal of Industrial Ecology, 2021.
Summary: We develop a general mathematical framework for dynamic stock models. We use the framework to classify a variety of stock models from different disciplines and discuss their applicability. The framework provides a common language for the interdisciplinary analysis of coupled human–environment systems.
Themes: Material flow analysis.
E. Clédat, DL, Revue XYZ, 2018. Featured on Swiss national television.
Summary: The Swiss Train Challenge is to set foot in all 26 cantons of Switzerland in as little time as possible, using only public transportation. Relying on human intuition informed by a geographical information system to select the relevant train stations, and on computational power to solve the resulting mixed-integer linear optimization problem, we found a solution that beats the current record of 17 hours and 19 minutes, by 25 minutes. When testing our itinerary in practice, we made all connections but one for which the arriving train was 20 minutes delayed, a rare event in Switzerland. This is the first time that an algorithm has been used to calculate the Swiss Train Challenge itinerary.
Themes: Large-scale optimization.
S. Majerus, DL, J. Van Herle, Electrochemical Energy Conversion and Storage, 2018.
Summary: Solid oxide fuel cells are considered as a more efficient alternative for valorizing agricultural-derived biogas, which, at the moment, is vastly done with cheaper conventional engines. After an analysis of the economic merits, target farm sizes are recommended for each country. The low valorization of manure-derived biogas in Europe offers a big opportunity for the commercialization of solid oxide fuel cells and for a push toward mass production.
Cost requirements for a small-scale SOFC fed from agricultural biogas
S. Majerus, DL, J. Van Herle, Electrochemical Energy Conversion and Storage, 2017.
Summary: To date, less than 5% of the Swiss agricultural biogas potential is used. It is possible to increase this value up to 86% through the deployment of 2kWel engines. The small size of the Swiss farm requires biogas installations in the kW-range. Small-scale biogas facilities are not profitable yet: The main challenge is to bring down the lifetime cost of the fuel cells to 11,000 CHF/kWel (considering a lifetime of ten years) and to reduce the investment cost of small-scale biogas facilities to around 9500 CHF/kWch. In the kW-range, solid oxide fuel cells have higher electrical conversion efficiencies than internal combustion engines. We find that SOFCs become competitive over combustion engines if their investment cost decreases to below 13,000 CHF/kWel for an 11 year lifetime.
A review of the state of research on vehicle-to-grid (V2G): Progress and barriers to deployment
DL, F. Vuille, D. Kuhn, European Battery, Hybrid and Fuel Cell Electric Vehicle Congress, 2017.
Summary: Vehicle-to-grid (V2G) could lower the need for stationary distributed storage by capitalizing on the existing batteries of EVs that are parked most of the time. Given this apparent benefit, it may appear surprising that the V2G technology has not yet been deployed in a wider scale. To investigate this discrepancy, we review the status of research on V2G and the status of technical development and deployment. We assess the barriers to V2G deployment by identifying the main open research questions from a technical and economic point of view.
A linear programming approach to the optimization of residential energy systems
DL, P. Caliandro, J. Van Herle, D. Kuhn, Journal of Energy Storage, 2016. Received a 10,000 CHF start-up grant for commercialization.
Summary: A decision-support tool in the form of a linear program is developed to determine the optimal investment and operating decisions for residential energy systems. It shows how energy conversion units such as a cogeneration fuel cell, a heat pump, a boiler, photovoltaic panels and solar thermal collectors can be combined with energy storage devices, consisting of a battery and a hot water tank, to drive down total yearly energy costs and CO2 emissions while meeting space heat, hot water and electricity needs.
The Economy of Azerbaijan: Oil and Gas
DL, L. Stadler, T. Vuillemin, In T. Brunner, N. Hayoz, C.R. Famos (Eds.), States and Societies in Transition – History, Threats and Opportunities. The Case of Georgia and Azerbaijan (pp. 25–32), 2016.
Summary: Oil and gas play an indispensable role in Azerbaijan’s economy, its political system, and its foreign policy. However, as a result of its overwhelming dependence on these resources and their predicted depletion in the near future, the country’s political and economic systems are in desperate need of reorientation. The reason why the latter has so far failed to manifest itself is because a select few stand to benefit disproportionately from the status quo, a status quo which is rapidly approaching its expiration date.