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Originally developed and validated at the Cabauw (Netherlands) topographically flat onshore location, the alpha-I wind resource extrapolating method was tested at the FINO3 offshore site in the North Sea (Germany). The aim was to prove its validity also when applied over a substantially different environment in terms of surface characteristics and stability conditions. Data from local mast at 30, 80, and 100 m were used, with extrapolations to 80-m and 100-m turbine hub heights accomplished based on 30-m turbulence intensity observations. Trained over a 2-year period (2011-2012), the method was validated on year 2013. Similarly to the onshore application, the method was reliable in extrapolating wind speed to both 80 m and 100 m, with bias within 5%, NRMSE = 0.20 and r = 0.94. Conversely, scores were largely better than at the onshore site in predicting the annual energy yield, biased by 0.41-1.02% at 80 m, and 1.12-1.36% at 100 m. The method proved to be highly sensitive to the stability classification, as not considering this option increased its biases to 4.51-5.93% at 80 m, and 7.46-8.23% at 100 m. Method's reliability might suitably help reduce the number of masts installed throughout a large offshore area.

The reversible dissociation/carbonation of metal carbonates, performed in fluidized bed reactors, is one of the most promising technological solution for thermochemical energy storage (TCES) in concentrating solar power plants (CSP). In this framework, the SrCO3/SrO system is receiving increasing interest due to its high energy density (4 GJ/m3) and working temperatures (up to 1200 ?C). As the more investigated CaCO3/CaO couple, also SrO undergoes a dramatic drop of reactivity over multiple carbonation/calcina- tion cycles due to sintering. Even though the potentiality of this system has already been proved by thermo-gravimetric analyses, its actual reaction performances in a fluidized bed are strongly dependent on the gas-solid contact efficiency and heat/mass transfer between the gaseous and solid phase. In this work, the cyclic carbonation/calcination of the SrO/SrCO3 system for TCES-CSP has been investigated by thermo-gravimetric analysis and, for the first time, in a lab-scale fluidized bed rig, thus providing useful applicative insights. A new Al2O3-stabilized composite has been synthesized, i.e. Al2O3 has been added to SrO/SrCO3 system as both sintering inhibitor and flow conditioner. In particular, composite materials with different Al2O3/SrO composition have been synthesized to investigate the ef- fect of the inhibitor amount on both the fluidizability and energy storage performances.

Based on a 3-year (2011-2013) dataset of 10-min records collected at 10, 20, 40, and 80 m from the met mast of Cabauw, a time-varying investigation of the wind shear coefficient (WSC) relationship with atmospheric stability was addressed. WSC interdaily and interannual variability was analysed according to a 2-D combined representation, which confirmed a clear oval-shaped "solar shadow" caused by solar warming observed during diurnal unstable hours, and large WSCs occurring under strong stable conditions during the summer nights.Three different power law based approaches were compared to extrapolate wind resource to the turbine hub height according to the following WSC settings: (i) site's previously measured overall yearly average; (ii) site's previously measured stability-varying yearly averages; (iii) 10-min theoretically predicted values by applying the Panofsky and Dutton (PD) model. The latter proved to be the finest approach, providing extrapolated wind resource biased by 1-5% and energy yield by 5.51-10.57%, and showing the highest accuracy occurring under the most frequent (and most energetic) neutral conditions, when Weibull distribution's tail including the highest wind speed bins is particularly finely reproduced.This work confirmed how instrumental availability of detailed information on site's atmospheric stability classification is for wind energy studies.

Artículos en revistas Hybrid microgrids are expected to play an important role in the expansion of access to electricity in developing countries. While most of these systems are operated with dispatch strategies which do not make use of predictions about the load or about the availability of renewable energy resources, forecast-based strategies have recently gained attention as an alternative to bring down operation costs. In this work, we develop a framework to assess this potential under a range of assumptions about the quality of load and photovoltaic generation forecasts. The application of the methodology to a village of 600 households reveals cost savings ranging between 2% and 7% depending on the forecast quality and the composition of the microgrid. We also show that sizing microgrid components under the assumption of a predictive operation strategy results in a design with a higher share of intermittent generation. info:eu-repo/semantics/publishedVersion

This paper presents a multidisciplinary methodology to estimate the underground heat-exchange potential for Borehole Heat Exchangers (BHEs) coupled with Ground Source Heat Pumps (GSHPs) over wide areas. The proposed methodology was tested in four sites in western Sicily (southern Italy) where the shortage of subsurface geological data, in addition to the undefined authorization processes for this kind of system, is probably the main barrier to planning and exploiting geothermal heat for heating and cooling purposes. Reliable high-resolution 3D geological and petrophysical models were built based on the integration of airborne electromagnetic data and laboratory measurements of the thermal properties of rock samples. A GIS-based procedure was applied to assess the geothermal heat-exchange potential using 3D models of thermal conductivity as the main input. The results of the analyses are represented by thematic maps of the underground heat exchange potential for BHEs coupled with GSHPs. The study areas show a generally high suitability for the use of this technology and several municipalities in the area could take advantage of the resulting maps for energy planning.

Exploitation of solar energy is becoming increasingly popular thanks to the potential saving on energy costs and to widespread environmental friendly policies. In this context, solar cooling is particularly interesting since greater cooling loads are usually needed in areas where the solar radiation is more abundant and during sunny seasons. The present work aims to evaluate the potential benefits of integrating a traditional vapour compression cycle with a solar powered ejection cycle, in order to take advantage of solar energy without prejudicing the possibility of cold production during night or cloudy days. A numerical model is implemented in order to simulate the behaviour of solar capitation circuit, ejection cycle and traditional cycle. Considering weather data and global plant performance, the model is thereafter used to estimate a set of global performance parameters.

In this work, a novel enhanced deep borehole heat exchanger (EDBHE) was proposed to improve heat extraction efficiency based on the jet grouting method. By means of this technology, a soilcrete zone with high thermal conductivity was built near the wellbore. To analyze the feasibility and efficiency of this method, we firstly constructed a validated deep borehole heat exchanger (DBHE) model based on the field experimental data. Numerical simulations were carried out to investigate the 30-year production performance of EDBHE. Results demonstrated that the jet grouting method is an efficient way for improving thermal output of DBHE. It is evaluated that the average annual heat production rate over a 30-year heating period of EDBHE is 463.2 kW, which is 1.27 times as that of DBHE. Sensitivity analyses indicate that the heat production rate and outlet temperature mainly depend on the height and radius of the artificial soilcrete zone. However, thermal output is not sensitive to thermal conductivity of the soilcrete zone due to the higher thermal resistance of the geological formation. For the experimental site used in this work, the recommended height, radius, and thermal conductivity of the soilcrete are 1000 m, 1.0 m, and 50 W/m °C, respectively.

Generic proposals for an effective integration of renewable energy sources in the urban environment are frequently carried out by project developers, local governments and media, although an in-depth knowledge of the technical and energetic limitations is often missing. In particular, the installation of small wind turbines on the rooftops of tall buildings is considered to represent an attractive solution thanks to the supposed possibility of exploiting local flow accelerations induced by the building façades. The real feasibility of this scenario has, however, yet to be proved, both in terms of real energy harvesting and of compatibility of the machines with a densely populated area. In this study, a critical examination of the flow conditions on the rooftop of a building in an urban environment has been carried out by means of CFD simulations. The main goal of the analysis was the assessment of some general criteria to evaluate the convenience of a microeolic turbine installation on the roof of a selected building as a function of both its geometrical features and those of its upwind building along the prevailing wind direction. In each configuration, the flow velocity and skew angle on the rooftop area of the installation building were calculated for different incoming wind profiles and compared to their levels in the undisturbed flow. Finally, an energy-based comparison between the flow potentials in the investigated environment is provided and some general tendencies are outlined.