• Energy Research
• Renewable Energy close
• Netherlands close

This paper shows a detailed analysis of a biomass HTL process by considering changes in three main reaction variables (i.e. catalysts (water, Na2CO3(aq.), and Fe(aq.)), temperature (280–340 °C), and catalysts/biomass mass ratio (0–0.33 kg catalysts/kg biomass)), and by assessing their influence on the techno-economic and GHG emissions performance. This analysis is based on Aspen Plus® simulations, process economics and life-cycle GHG assessment on SimaPro (using Ecoinvent 2.2). Results showed that the lowest production cost for biocrude oil is achieved when HTL is performed at 340 °C with Fe as catalyst (450 €/tbiocrude-oil or 13.6 €/GJbiocrude-oil). At these conditions, the biocrude oil produced has an oxygen content of 16.6 wt% and a LHV of 33.1 MJ/kgbiocrude-oil. When the hydrotreatment and hydrogen generation units are included, the total production costs was 1040 €/tupgraded-oil or 0.8 €/Lupgraded-oil. After fractionation, the estimated production cost was 1086 €/tbiojet-fuel or 25.1 €/GJbiojet-fuel. This value is twice the commercial price of fossil jet fuel. However, the allocated life cycle GHG emissions for renewable jet fuel were estimated at 13.1 kgCO2-eq./GJbiojet-fuel, representing only 15% the GHG emission of fossil jet fuel and therefore, indicating a significant potential on GHG emission reduction.

We compare the available wind resources for conventional wind turbines and for airborne wind energy systems. Accessing higher altitudes and dynamically adjusting the harvesting operation to the wind resource substantially increases the potential energy yield. The study is based on the ERA5 reanalysis data which covers a period of 7 years with hourly estimates at a surface resolution of 31 x 31 km and a vertical resolution of 137 barometric altitude levels. We present detailed wind statistics for a location in the English Channel and then expand the analysis to a surface grid of Western and Central Europe with a resolution of 110 x 110 km. Over the land mass and coastal areas of Europe we find that compared to a fixed harvesting altitude at the approximate hub height of wind turbines, the energy yield which is available for 95% of the time increases by a factor of two. 28 pages, 10 figures

Geothermal energy is gaining momentum as a renewable energy source. Reservoir simulation studies are often used to understand the underlying physics interactions and support decision making. Uncertainty related to geothermal systems can be substantial for subsurface and operational parameters and their interaction with regards to the output in terms of lifetime, energy and economic output. Specifically, for geothermal systems with the fault acting as the main fluid pathway the relevant field development uncertainties have not been comprehensively addressed. In this study we show how the produced energy, system lifetime and NPV are affected considering a range of subsurface and operational parameters as uncertainty sources utilizing an ensemble of 16,200 3D Hydraulic-Thermal (HT) reservoir simulations, conceptually based on the Rittershoffen field. A well configuration with oblique angles with respect to the main permeability anisotropy axes results in higher system lifetime, generated energy and NPV. A well spacing of 600 m consistently yields a higher economic efficiency (€/MWh) under all uncertainty parameters considered. More robust development options could be utilized in the absence of fault permeability characterization to ensure improved output prediction under uncertainty. Studies based on the methodology presented can improve investment efficiency for field development under subsurface and operational uncertainty. Renewable Energy, 171 ISSN:0960-1481 ISSN:1879-0682

Small satellites are receiving increased recognition in the space domain due to their reduced associated launch costs and shorter lead time when compared to larger satellites. However, this advantage is often at the expense of mission capabilities, such as available electrical power and propulsion. A possible solution is to shift from the conventional solar photovoltaic and battery configuration to a micro-Organic Rankine Cycle (ORC) and thermal energy storage system that uses the waste energy from a solar thermal propulsion system. However, limited literature is available on micro-ORC systems, which are capable of producing a few hundred Watts of electrical power. This paper describes the proposed system layout and model of the integrated micro-ORC system, for various working fluids such as Toluene, Hexamethyldisiloxane (MM), and Octamethylcyclotetrasiloxane (D4). Toluene has been identified as a promising working fluid candidate resulting in a power generation system volume fraction of 18% for a 215 kg Low Earth Orbit satellite. The micro-ORC system is capable of producing 200 W of electrical power. The design provides high specific energies of at least 500 Wh/kg but, has a low shared specific power of 10 W/kg. A preliminary design of the micro-turbine provides a conservative total-to-static efficiency of 57%.

It was recently shown that the Arctic has been warming much faster than the rest of the globe during the last decades. This warming has reduced the ice extent significantly, which will strongly impact the wave climate in the Arctic regions, thus affecting the design of marine structures, operations, and energy resources. This study focuses on the higher latitudes, and uses the advanced wave hindcast NORA3, which covers a big part of the North Atlantic and the whole Arctic Ocean, to analyze the spatio–temporal properties of wave height and wave energy flux during the last three decades. The most energetic waves in the Arctic Ocean are observed in the Greenland Sea and the Barents Sea. The study shows that the substantial diminishing of sea ice in the Arctic induces local and regional changes in both mean and extreme wave conditions. In the Arctic Ocean the changes in extreme wave height are more pronounced compared to changes in mean wave conditions. The results also indicate a strong positive trend in the extreme wave heights in the Arctic regions of the Barents Sea, the Kara Sea, the Laptev Sea, the East Siberian Sea, the Chukchi Sea, and the Beaufort Sea. ; Offshore Engineering

Abstract The present paper focuses on the determination of optimum layouts for linear arrays of heaving Wave Energy Converters (WECs) in front of a vertical wall. Optimum layouts maximize the annual averaged absorbed energy at a given marine site and satisfy spatial constraints. For achieving this goal, we developed an efficient optimization numerical framework, where a genetic algorithm solver is appropriately coupled with a frequency-domain hydrodynamic model, while, furthermore, a numerical wave model is utilized to determine the local wave climate conditions at the site of interest. The context is applied for an array of five semi-immersed, oblate spheroidal heaving WECs deployed at five near-shore sites of mild wave environments in the Aegean Sea, Greece. For each site, different optimization cases are solved, facilitating the investigation of different aspects of the examined problem. The largest annual energy absorption ability is observed for optimum layouts, characterized by the placement of the array close to the wall and the formation of clusters of closely-positioned WECs near the wall edges. Compared to arrays employed at sites in south-eastern Aegean, optimally-arranged arrays at central Aegean locations showed reduced energy absorption ability due to milder local wave conditions and/or the existence of quite limited water depths.

An economical way to harvest tidal energy is by integrating free stream turbines in coastal infrastructure. While numerous studies have investigated how turbines should be arranged in idealized geometries to optimize their performance, only a few have considered the influence of realistic bed features. This research investigates the influence of a hydraulic structure on the performance of a tidal turbine, using the combination of field monitoring of full scale turbines installed in a Dutch storm surge barrier - comprising a weir and pillars - and by developing a corresponding theoretical model. The observed production by the turbines was large compared to situations with an unconstrained flow for two reasons. Firstly, the flow contraction by the weir increased the mass flux through the rotor plane. Secondly, the turbine suppressed energy losses in the recirculation zone downstream of a weir. The proposed model provides a quantitative estimate of these effects and is validated against field data. The model can be used as a design tool or parametrization of turbines in a large scale shallow water model, providing performance estimates covering a range of turbine-weir configurations. The work contributes to efficiently exploiting tidal energy with turbines in coastal bridges or flood defenses.

Onshore wind potentials are commonly mapped with site selection criteria that either fully include or exclude land for wind farms. However, current research rarely addresses the variability of these criteria, possibly resulting in overly conservative or optimistic potentials. This paper proposes a method to account for the variability of site selection criteria in resource assessments. We distinguish between static and flexible, non-binary criteria and assess onshore wind's technical and economic potential with bias-corrected ERA5 data, 28 turbine power curves, and a turbine-specific cost model. For Indonesia, we show that our flexible mapping approach improves the transparency of resource potential assessments and could contribute to more informed and useful recommendations. These recommendations could address the (1) calibration of site exclusion thresholds, (2) dilemmas of preferring one land type over others, (3) location-specific challenges of wind farm deployment, and (4) more direct support schemes for affected stakeholders and wind farm operators. We report a technical potential of 207–1,994 TWh/year in Indonesia, which could cover more than 50% of 2030 electricity demand on all islands. LCOEs range between 5.8 and 24.5 US¢(2021)/kWh with an economic potential of 16 TWh/year, which improves to 31–212 TWh/year with a carbon tax of 100 US$(2021)/tCO2e. ; Energie and Industrie ; Wind Energy