Journal: Renewable Energy

Abbreviation

Renew. Energy

Publisher

Elsevier

Journal Volumes

ISSN

0960-1481
1879-0682

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Publications 1 - 10 of 52
  • Global water footprint assessment of hydropower
    Item type: Journal Article
    Scherer, Laura; Pfister, Stephan (2016)
    Renewable Energy
  • Experimental investigation of the applicability of a 250 kW ceria receiver/reactor for solar thermochemical hydrogen generation
    Item type: Journal Article
    Thanda, Vamshi Krishna; Fend, Thomas; Laaber, D.; et al. (2022)
    Renewable Energy
    Solar thermochemical water splitting via a two-stage redox cycle has been subjected to numerous theoretical and experimental studies since a couple of decades. It has been considered as a promising technology to generate green hydrogen as it is feasible to directly convert concentrated solar radiation into storable chemical energy. The present article describes the results of an experimental campaign, which has been carried out to further demonstrate the feasibility of this technology. Based on the prior experience from solar gas turbine projects, a combined receiver/reactor has been designed and built up operating at temperatures between 1400 °C and 1000 °C using radiative power of up to 150 kW generated by a large-scale solar simulator (Synlight). The reactor has a total volume of 90 L with open porous ceramic foam structure. Additionally, high-performance heat exchangers have been used to recover the heat content of the product gases. Typical necessary durations for the sub-cycles, reduction and oxidation as well as durations for the corresponding necessary heating and cooling phases have been determined. By producing up to 8,8 g of hydrogen per cycle it could be shown that the production of hydrogen in a medium scale structured reactor is possible.
  • Impact of forested fetch on energy yield and maintenance of wind turbines
    Item type: Journal Article
    Zendehbad, Mohsen; Chokani, Ndaona; Abhari, Reza S. (2016)
    Renewable Energy
  • Nonlinear model predictive pitch control of aero-elastic wind turbine blades
    Item type: Journal Article
    El-Baklish, Shaimaa K.; El-Badawy, Ayman A.; Frison, Gianluca; et al. (2020)
    Renewable Energy
    This paper proposes a Nonlinear Model Predictive Controller (NMPC) for pitch control of Horizontal-Axis Wind Turbines (HAWTs) in Region 3 to avoid flutter aero-elastic instability. First, an aero-elastic HAWT rotor model was derived based on extended Hamilton’s principle using the coupled flap-wise and torsional motions of each blade. As for the aerodynamic loading, expressions for lift and pitching moment are obtained based on modifications of Theodorsen’s fixed wing strip theory for a rotating HAWT blade. The model is spatially discretized using the Assumed Modes Method with the first three flap-wise and two torsional mode shapes for the fixed cantilevered blade under free loading. This was applied to the 5-MW NREL (National Renewable Energy Laboratory) reference HAWT. The time-domain response under aerodynamic loading of the developed model was compared to FAST (Fatigue, Aero dynamics, Structure and Turbulence) aero-servo-elastic HAWT simulator. Then, an NMPC pitch controller was designed using the developed model for prediction. This was compared to another NMPC pitch controller which used a lumped-mass drive-train model as a prediction model and to the baseline gain scheduled PI pitch controller.
  • A stochastic framework for uncertainty analysis in electric power transmission systems with wind generation
    Item type: Journal Article
    Sansavini, Giovanni; Piccinelli, Roberta; Golea, Lucia R.; et al. (2014)
    Renewable Energy
  • Ground energy balance for borehole heat exchangers: Vertical fluxes, groundwater and storage
    Item type: Review Article
    Rivera, Jaime A.; Blum, Philipp; Bayer, Peter (2015)
    Renewable Energy
  • Potential analysis of pumped heat electricity storages regarding thermodynamic efficiency
    Item type: Journal Article
    Roskosch, Dennis; Venzik, Valerius; Atakan, Burak (2020)
    Renewable Energy
  • The feasible onshore wind energy potential in Baden-Württemberg: A bottom-up methodology considering socio-economic constraints
    Item type: Journal Article
    Jäger, Tobias; McKenna, Russell; Fichtner, Wolf (2016)
    Renewable Energy
    Detailed information about the potential and costs of renewable energies is an important input for energy system models as well as for commercial and political decision-making processes. Especially wind energy with its increasing locally installed capacity and hub heights plays an important role when it comes to meeting climate targets and optimizing electricity networks. Recently however, wind energy has faced more and more social barriers and land use constraints which can negatively impact both political goals and investment decisions. Therefore this work presents a bottom-up methodology to estimate these effects by calculating the feasible potential and the associated costs for the German federal state of Baden-Württemberg as a case study. Landscape aesthetical aspects are considered and an algorithm applied based on graph-theoretical considerations to include spatial planning rules such as separation distances between wind farms. By means of spatially high-resolution land use data and techno-economic parameters, possible wind turbines are placed considering wind direction and variable spacing between turbines. In a further step, possible farm sites are located and assessed, and the result is presented in the form of cost-potential curves. The feasible potential is found to be between a third and a half of the technical potential and is between 11.8 and 29.1TWh, with costs between 6.7 and 12.6€ct/kWh. In addition, a substantial spatial shift in the location of future wind energy production can be observed when wind farm spacing is taken into account. The quality of the algorithm is tested against already existing wind farms and areas that are approved by regional authorities for the use of wind energy, and a very good correlation is observed. The focus in future work should lie on the development of an economic criterion that, unlike the levelized cost of electricity (LCOE), is able to account for the system costs of a widespread wind energy development, including network expansion, balancing power and reserve energy costs. Further, visibility analysis could be implemented using digital elevation models to consider the topography for optimal wind farm spacing.
  • Aerodynamics of wind turbine wakes in flat and complex terrains
    Item type: Journal Article
    Subramanian, B.; Chokani, Ndaona; Abhari, Reza S. (2016)
    Renewable Energy
  • A novel design and performance optimization methodology for hydraulic Cross-Flow turbines using successive numerical simulations
    Item type: Journal Article
    Mehr, Goodarz; Durali, Mohammad; Khakrand, Mohammad H.; et al. (2021)
    Renewable Energy
    This paper introduces a new methodology for designing and optimizing the performance of hydraulic Cross-Flow turbines for a wide range of operating conditions. The methodology is based on a one-step approach for the system-level design phase and a three-step, successive numerical analysis approach for the detail design phase. Compared to current design methodologies, not only does this approach break down the process into well-defined steps and simplify it, but it also has the advantage that once numerical simulations are conducted for a single turbine, most of the results can be used for an entire class of Cross-Flow turbines. In this paper, after a discussion of the research background, we explain the design process used and the ANSYS®-based CFD model of the turbine in detail. The design process consists of three steps. First, designing nozzle geometry; second, optimizing runner parameters; and third, enhancing turbine performance by analyzing various load conditions. A turbine designed using this process in a simulation case study achieves a peak hydraulic efficiency of 91% and peak overall efficiency of 82% that is maintained for volume flow rates as low as 14% of the nominal value and water head variations up to 30% of the nominal value.
Publications 1 - 10 of 52