• Energy Research
• Restricted close
• Open Source close
• DK close
• US close

The paper describes formation and spreading of dense shelf waters in the Adriatic Sea (North Adriatic Dense Water, NAdDW) during the winter of 2012 as a consequence of an intense and long cold air outbreak of northeasterly Bora winds. As a result, during February 2012 northern Adriatic Sea water temperature dropped to about 6 degrees C and density exceeded 1030 kg/m(3), most likely the maximum value since 1929. NAdDW dynamics has been investigated by means of a 3-D ocean-wave coupled model running on a high resolution and eddy-permitting grid. The numerical experiments have relied on the Coupled-Ocean-Atmosphere-Wave-Sediment-Transport (COAWST) system forced one-way with atmospheric forcings provided by the model COSMO-17. A suite of observational data has been used to characterize the Bora event and evaluate numerical model performance. At sub-basin scales, the newly formed waters flowing southerly have produced a water renewal of the northern Adriatic, as more than 50% of water volumes have left the basin. Dense waters volume transports, evaluated through different Adriatic cross-sections, have been modulated by tides (damped for the densest water masses) and reached about 1 Sv. The contribution of wave-induced forcings has been quantified and examined, indicating that these represent a major driving mechanism during NAdDW production and spreading phases. This work provides evidence that NAdDW is spread accordingly with two different mechanisms: at early stages of its formation, the wind-driven ocean circulation pushes newly formed waters to leave the northern basin with relatively high speeds (about 0.30 m/s). Later on, remaining NAdDW leaks slowly out (0.09 m/s as average) from the production site. Residence times of dense waters in the north, middle, and south Adriatic Sea are also documented. (C) 2014 Elsevier Ltd. All rights reserved.

Abstract The OECD/NEA Sandia Fuel Project provided unique thermal-hydraulic experimental data associated with Spent Fuel Pool (SFP) complete drain down. The study conducted at Sandia National Laboratories (SNL) was successfully completed (July 2009 to February 2013). The accident conditions of interest for the SFP were simulated in a full scale prototypic fashion (electrically heated, prototypic assemblies in a prototypic SFP rack) so that the experimental results closely represent actual fuel assembly responses. A major impetus for this work was to facilitate severe accident code validation and to reduce modeling uncertainties within the codes. Phase I focused on axial heating and burn propagation in a single PWR 17 × 17 assembly (i.e. “hot neighbors” configuration). Phase II addressed axial and radial heating and zirconium fire propagation including effects of fuel rod ballooning in a 1 × 4 assembly configuration (i.e. single, hot center assembly and four, “cooler neighbors”). This paper summarizes the comparative analysis regarding the final destructive ignition test of the phase I of the project. The objective of the benchmark is to evaluate and compare the predictive capabilities of computer codes concerning the ignition testing of PWR fuel assemblies. Nine institutions from eight different countries were involved in the benchmark calculations. The time to ignition and the maximum temperature are adequately captured by the calculations. It is believed that the benchmark constitutes an enlargement of the validation range for the codes to the conditions tested, thus enhancing the code applicability to other fuel assembly designs and configurations. The comparison of lumped parameter and CFD computer codes represents a further valuable achievement.

In the present work, a novel hybrid solar-based smart building energy system is introduced and studied. The system comprises innovative photovoltaic-thermal-cooling (PVTC) panels integrated with hot and cold storages with two-way interaction with electricity, heat, and cooling networks (if any). The proposed system is compared with PV-based systems integrated with battery and heat pump for a case study complex building in Aarhus, Denmark. The comparison is conducted by evaluating the performance and economic indicators and investigating the effect of significant parameters on each scenario via a parametric study. Furthermore, the optimal operating conditions and sizing of the proposed system are determined using the genetic algorithm method considering initial cost and traded energy with local energy networks as the objective functions. The comparison results show that the proposed solution is the most cost-effective scenario with the lowest initial cost of about 457,000 $ and a payback period of 6.6 years. This is mainly due to the simultaneous interaction with electricity/heat/cooling networks as well as the elimination of the battery and the heat pump, which are offered by the proposed scenario. It is shown that, in comparison to PV panels, the PVTC can produce 328.7 MWh and 125.6 MWh extra heat and cooling annually. The scatter distribution of significant parameters shows that the panel area and heat storage capacity are not sensitive parameters, and keeping the cold storage capacity at the lower bound is a techno-economically better option.

This study is based on assessing fecal indicator bacteria contamination along meteorological, hydrological and physical-chemical variables after high rainy events during the summer period. The study focused on four different coastal sites in the western and eastern Adriatic coast characterized by various geomorphological and hydrological features, levels of urbanization and anthropogenic pressures, with the aim of finding appropriate and effective solutions to ensure the safety and sustainability of tourism and public health. Detailed in-situ survey revealed a wide range of fecal indicator bacterial (FIB) across the different river mouths with concentrations of E. coli ranging from 165 to 6700 CFU 100 mL-1. It was found that nitrogen compounds track microbial load and acted as tracers for fecal contaminants. Further, a modelling tool was also used to analyze the spatial and temporal distribution of fecal pollution at these coastal sites. The integrated monitoring through high frequent survey in river waters and modeling framework allowed for the estimation of fecal indicator bacterial load at the river mouth and examination of fecal pollutant dispersion in recreational waters, considering different scenarios of fecal dispersion along the coast. This study formed the basis of a robust decision support system aimed at improving the management of recreational areas and ensuring the protection of water bodies through efficient management of bathing areas.

Abstract Sustainability is an important and difficult consideration for the stakeholders/decision-makers when planning a biofuel supply network. In this paper, a Mixed-Integer Non-linear Programming (MINLP) model was developed with the aim to help the stakeholders/decision-maker to select the most sustainable design. In the proposed model, the emergy sustainability index of the whole biodiesel supply networks in a life cycle perspective is employed as the measure of the sustainability, and multiple feedstocks, multiple transport modes, multiple regions for biodiesel production and multiple distribution centers can be considered. After describing the process and mathematic framework of the model, an illustrative case was studied and demonstrated that the proposed methodology is feasible for finding the most sustainable design and planning of biodiesel supply chains.

This paper investigates the frequency performance problem of microgrids (MGs) integrated with renewable employing an energy storage system (ESS) equipped with virtual inertial control (VIC) support. To tackle the uncertainties related to the system operation, a two-layer multiple model predictive control (TLMMPC) method, consisting of nominal and ancillary MMPCs, is proposed to submit effective control signals to the ESS for improving system frequency performance. The ancillary MMPC generates the control commands for the VIC-based ESS utilizing the signals provided by the nominal MMPC and the frequency deviation signal of the actual system considering uncertainties and operating constraints. The control commands are generated to attain the minimum value of frequency response error with the least control endeavor while considering various operational and physical limitations. The TLMMPC method has the capability to work with different state of charge (SoC) levels to obtain the desired SoC and highest efficiency from the ESS and preserve the ESS's longevity. The dynamic performance of the proposed TLMMPC technique is investigated on an islanded MG and compared to model predictive control (MPC), fractional-order MPC, and tilt-integral-derivative controllers under different scenarios. The results validate that the proposed TLMMPC technique significantly improves the system frequency response from viewpoints of settling time, peak overshoot, and undershoot and obtains the most efficient ESS compared to the other methods.

The east German energy system is in a process of being completely rebuilt. Unfortunately, the huge investments are not used for implementing a technical and institutional restructuring, which is needed in order to achieve energy efficiency. The energy system will, among others, maintain its inefficient structure with separate production of heat and power. The ongoing changes are limited to improvements of power plant efficiency in combination with a change from a system based on brown coal for both heat and power into a system in which the electricity production is still based on brown coal and heating is produced on oil and natural gas. This rebuilding will bring the CO2-emission down from 20 t/inhabitant in 1989 to 13 t/inhabitant in year 2010, which is still much higher than the EU average on 8 t/inhabitant. This article describes how a restructuring could bring the figure below 7 t/inhabitant. The lack of ability to implement this restructuring of the energy system is, among others, due to an ownership structure, where networks of companies own the entire production and distribution chain from oil and coal to electricity. In this ownership structure, energy restructuring strategies which decrease the consumption of oil and coal will reduce the profits. At the same time the potential regulator, the parliamentary system, is politically and economically interlinked with and dependent upon the established energy companies. Consequently, it is difficult to establish the regulation reforms which are necessary for restructuring of the energy sector. There is still a lot to be gained from a restructuring of the east German energy sector. This restructuring requires institutional reforms, where the public regulation processes become independent of the industry which should be regulated.

The direct-on-line start-up of a synchronous motor results in alternating torques which can excite the lowest torsional natural frequency of compressor trains used in the oil & gas industry. Considering a slip-dependent variation of the rotor parameters, an integrated electrical and mechanical simulation model is developed, providing an accurate estimation of the air-gap torque. The proposed approach is validated by an accurate testing campaign carried out during moto-compressor field test activities.