Journal: Applied Energy

Abbreviation

Appl. Energy

Publisher

Elsevier

Journal Volumes

ISSN

0306-2619
1872-9118

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Publications 1 - 10 of 249
  • Control of thermally-activated building systems (TABS)
    Item type: Journal Article
    Gwerder, Markus; Lehmann, Beat; Tödtli, Jürg; et al. (2008)
    Applied Energy
  • Demonstration of thermal borehole enlargement to facilitate controlled reservoir engineering for deep geothermal, oil or gas systems
    Item type: Journal Article
    Kant, Michael; Rossi, Edoardo; Duss, Jonas; et al. (2018)
    Applied Energy
  • Energetically-optimal PEM electrolyzer pressure in power-to-gas plants
    Item type: Journal Article
    Tjarks, Geert; Gibelhaus, Andrej; Lanzerath, Franz; et al. (2018)
    Applied Energy
    Hydrogen production from renewable electricity in power-to-gas concepts is promising for future energy storage systems since hydrogen offers high energy density and can be used emission free. Economically viable power-to-gas applications require high efficiency and thus low specific energy demand of the hydrogen production. Energy is required for hydrogen production via water electrolysis, but also for gas conditioning. Gas conditioning includes mechanical gas compression to a defined storage pressure and gas drying to purify the raw hydrogen. The energy demand of gas conditioning can be reduced by operating pressurized electrolyzers. However, pressurized operation increases the energy demand of the electrolyzer. To determine the optimal operating pressure of the electrolyzer, the overall power-to-gas process has to be considered. In this paper, the energy demand of the overall power-to-gas plants is optimized considering compression and temperature swing adsorption (TSA)-drying of hydrogen. It is shown that an optimum pressure for each operating condition in the electrolyzer in relation to the efficiency exists. This optimal operating pressure depends on the current density in the stack and the hydrogen storage pressure. When operating the system with load adapted operating pressure efficiencies between 55% and 73% for the whole power-to-gas plant can be achieved. © 2018 Elsevier Ltd.
  • A critical reflection on modelling approaches for heat pumps and building envelope retrofits in local energy system optimisations
    Item type: Journal Article
    Hermann, Julian; Kachirayil, Febin; Lohrmann, Alena; et al. (2025)
    Applied Energy
    Integrating heat pumps and adopting building envelope retrofit (BER) measures is vital for decarbonising the built environment. This paper systematically reviews modelling approaches for these technologies within 84 local energy system optimisation studies. Our findings show that most studies simplify heat pump operation using a constant coefficient of performance (COP), perfect modulation, or a fixed heating capacity. While existing methods account for temperature-dependent COPs, only a few studies include more advanced approaches considering additional impacts. Two main approaches for modelling BER measures are identified: pre-defined retrofit sets with exogenous heat demand or an integrated retrofit selection with endogenous heat demand. While the pre-defined approach offers lower computational effort, it limits the BER solution space. The integrated approach achieves the opposite: a wider solution space but higher complexity. Moreover, only two studies consider the impact of BER measures on the heat supply temperature, an essential link between retrofit measures and heat pump efficiency. Based on our qualitative review, we derive recommendations for energy system modellers. For modelling heat pumps, we recommend using a temperature-dependent COP and heating capacity, as well as a lower modulation limit. Regarding BER measures, the integrated approach should be used for smaller scales (single buildings) while the pre-defined sets are suitable for larger scales. Finally, we propose a research agenda to address limitations and gaps in the current modelling approaches, such as addressing the performance gap between existing COP estimations and heat pump field performance and including a more detailed method for the heat supply temperature.
  • Designing multi-energy systems in Mediterranean regions towards energy autonomy
    Item type: Journal Article
    Terlouw, Tom Mike; Savvakis, Nikolaos; Bauer, Christian; et al. (2025)
    Applied Energy
    Decentralized multi-energy systems (MESs) are a key element of a future low-carbon energy supply. Here, we address the crucial role of grid-connected and off-grid MESs in achieving a low-carbon future, particularly relevant for regions like the Mediterranean with high renewable energy potential and carbon-intensive grid networks, using a mixed integer linear program for optimal economic and environmental MES design considering location-specific regulations. The results reveal that substantial cost (up to 30%, potentially saving 1.6 million) and greenhouse gas (GHG) emission reductions can be reached in Mediterranean regions with sufficient solar and wind energy resources currently relying on fossil fuel-based generators. However, our case study shows that the actual cost and emission reductions are most likely limited due to location-specific regulations (limiting cost savings to 0.8 million), especially those that constrain solar photovoltaic and onshore wind. Off-grid energy systems might be suitable decarbonization options in Mediterranean regions, to avoid absorbing current GHG-intensive power from the local power grid, under marginal cost increase (15%) compared to grid-connected cost optimization. However, off-grid MESs require substantial upfront investments and exhibit some environmental trade-offs, especially on material utilization, which could be overcome by balanced autonomy. Overall, truly sustainable and secure decentralized energy systems can only be reached by considering life cycle environmental impacts, social acceptance, and regulations during the design phase.
  • Cost of capital for renewables and enabling technologies: Measuring the multidimensional heterogeneity in Switzerland
    Item type: Journal Article
    Đukan, Mak; Steffen, Bjarne (2025)
    Applied Energy
    The cost of capital (CoC) is a critical parameter that significantly impacts the levelized costs of low-carbon energy technologies and cost-optimal decarbonization pathways. Nevertheless, empirical evidence on CoC differences between technologies and investor types is limited. Here, we study the heterogeneity among 11 technologies based on 193 CoC inputs from utilities, financial investors, and project developers in Switzerland. We find a wide range of CoC values across the technologies, averaging 3.6 % for small rooftop PV and 7.8 % for green hydrogen. Furthermore, we record an empirical variation of six percentage points even for assets of the same technology group, like solar PV, indicating differences between business models and investor types. Unlike neighboring countries that primarily rely on project finance for renewables, we find balance sheet financing to play an essential role for Swiss investors. Our results stress the need to differentiate CoC assumptions in energy system modeling and to consider not only technologies but also investor types and regional specificities as additional CoC dimensions.
  • Numerical analysis of the scavenge flow and convective heat transfer in large two-stroke marine diesel engines
    Item type: Journal Article
    Sigurdsson, E.; Ingvorsen, K. M.; Jensen, M. V.; et al. (2014)
    Applied Energy
  • Transforming decentralized energy systems: Flexible EV charging and its impact across urbanization degrees
    Item type: Journal Article
    Brodnicke, Linda; Kachirayil, Febin; Gabrielli, Paolo; et al. (2025)
    Applied Energy
    Electric vehicles (EVs) are critical to decarbonize personal transportation, yet they significantly increase electricity demands, challenging local energy systems. This study investigates the impact of various EV charging strategies on the optimal energy system design and operation across different degrees of urbanization. Using empirical data, electric vehicle driving behavior is captured within a municipal energy system optimization framework that models the transition to a net zero emissions energy system by 2050. Inflexible passive charging is evaluated against time-shifted smart charging and bi-directional vehicle-to-grid (V2G) across rural, suburban, and urban case studies in Northern Germany. This study identifies two main benefits of flexible EV charging. First, stationary storage requirements are significantly reduced compared to passive charging. The rural and suburban case studies, dominated by wind power, need less than 1 kWh of stationary storage per dwelling with passive charging in 2050 and eliminate storage needs with any kind of flexible EV charging. In contrast, the urban case study with limited wind potential and significant solar resources requires 11.5 kWh of stationary storage with passive charging, reduced by 20% with smart charging and by 35% with V2G. Second, while wind-dominated cases achieve higher self-consumption due to better alignment of EV charging with renewable generation, the urban case study benefits from earlier solar PV deployment with V2G, boosting self-sufficiency. These findings challenge the need for stationary storage in the presence of widespread flexible EV charging. Notably, V2G provides no significant advantage over smart charging in wind-dominated areas, emphasizing the need for context-specific EV integration strategies.
  • A holarchic approach for multi-scale distributed energy system optimisation
    Item type: Journal Article
    Marquant, Julien F.; Evins, Ralph; Bollinger, L. Andrew; et al. (2017)
    Applied Energy
  • Subtransmission grid control via online feedback optimization
    Item type: Journal Article
    Ortmann, Lukas; Maeght, Jean; Panciatici, Patrick; et al. (2026)
    Applied Energy
    The increasing electric power consumption and the shift toward renewable energy resources demand for new ways to operate transmission and subtransmission grids. Online Feedback Optimization (OFO) is a feedback real-time control method that can be employed to enable optimal operation of these grids. Such controllers can maximize grid efficiency (e.g., minimizing curtailment) while satisfying grid constraints like voltage and current limits. The OFO control method is tailored and extended to handle discrete inputs and it is explained how to design an OFO controller for the subtransmission grid. A novel benchmark is presented and published that corresponds to the real French subtransmission grid on which the proposed controller is analyzed in terms of robustness against model mismatch, constraint satisfaction, and tracking performance. It is shown that OFO controllers can help utilize the grid to its full extent, virtually reinforce it, and operate it optimally and in real-time by using the flexibility offered by renewable generators connected to distribution grids.
Publications 1 - 10 of 249