At present, a worldwide paradigm shift has become apparent, with more and more consumers consuming the energy generated by renewable energy sources (RES) systems, such as wind or photovoltaic (PV) ...energy, sometimes benefiting from appropriate incentives by individual governments. Consequently, it is necessary to carry out technical–economic assessments to understand the evolution of the viability of RES investments. Within the framework of an intelligent network control environment, the smart grid (SG) concept is associated with this model, and is an important tool in the management of energy distribution networks. This article aims to make a further contribution to this issue by analyzing the economic feasibility of investing in residential consumers, considering different RES configurations. Scenarios covered in this study include: “inject all on the low voltage network/consume all on the low voltage network”, self-consumption, net-metering, and storage systems. The economic study results in this article show that self-consumption with and without the injection of excess electricity into the grid is quite attractive. The bi-hourly tariff was found to be more profitable than other tariffs. Variable tariffs (bi or tri-hourly) are more profitable than fixed tariffs. It is also concluded that investment in storage systems is not yet an economically viable solution due to the high price of energy storage.
A gravitational sedimentation parametrization is presented, which sets the dynamic framework for the parametrization philosophy of linear combination of basis functions. The entire drop spectrum is ...represented as a linear combination of log‐normal distributions as part of an Eulerian simulation framework, in which all parameters of the distributions are calculated based on a prescribed set of three prognostic moments, thus eliminating the need of fixing any parameter to close the system of equations. The parametrization presents the advantage of avoiding the classification of water substance in artificial categories such as cloud water or rain water. Several experiments were performed, with an increasing number of distribution functions up to three, and with different sets of moments to establish which set performed the best. The comparison against the solution of an explicit sedimentation model shows that this parametrized approach is accurate enough to consider its inclusion in multi‐dimensional cloud models, achieving a better representation of the spectra with the use of a three‐member linear combination of basis functions.
An accurate gravitational sedimentation parametrization is presented, in which the entire droplet spectrum is represented as a linear combination of log‐normal distributions as part of an Eulerian simulation framework. All parameters of the distributions are calculated based on the first three moments of each member of the ensemble, presenting the advantage of avoiding the classification of water substance into artificial categories.
•We present an economic assessment of residential PV systems.•Different configurations including self-consumption and storage are investigated.•An increase of the profitability when self-consumption ...is considered is witnessed.•The solutions with battery storage are still not economically viable.
A progressive implementation of renewable microgeneration, mainly small sized Photovoltaics, in low voltage distribution networks is ongoing. In this context, self-consumption with storage allows to highlight the prosumer concept, bearing in mind that this strategy may be interesting both from a technical and economical perspectives. The intelligent network environment or Smart Grid comes close to this new model and may have a critical relevance in the management of intelligent power distribution networks, in the framework of a Smart Environment. This paper intends to give an additional contribution on the subject by investigating the economic profitability of different residential PV systems configurations. These include traditional “injects all into the network/consumes all from the network”, self-consumption, storage and net-metering. The joint operation of self-consumption and battery storage is particularly focused as it presents the current trend in residential PV systems. The results of the performed economic analysis point to the conclusion that self-consumption is already attractive, but storage is not a profitable solution, because battery investment is still too high, despite the cost reduction witnessed in recent years.
We present the final sample of 98 detached double white dwarf (WD) binaries found in the Extremely Low Mass (ELM) Survey, a spectroscopic survey targeting <0.3 M He-core WDs completed in the Sloan ...Digital Sky Survey footprint. Over the course of the survey we observed ancillary low-mass WD candidates like GD 278, which we show is a P = 0.19 day double WD binary, as well as candidates that turn out to be field blue straggler/subdwarf A-type stars with luminosities too high to be WDs given their Gaia parallaxes. Here, we define a clean sample of ELM WDs that is complete within our target selection and magnitude range 15 < g0 < 20 mag. The measurements are consistent with 100% of ELM WDs being 0.0089 < P < 1.5 day double WD binaries, 35% of which belong to the Galactic halo. We infer that these are mostly He+CO WD binaries given the measurement constraints. The merger rate of the observed He+CO WD binaries exceeds the formation rate of stable mass-transfer AM CVn binaries by a factor of 25, and so the majority of He+CO WD binaries must experience unstable mass transfer and merge. The systems with the shortest periods, such as J0651+2844, are signature LISA verification binaries that can be studied with gravitational waves and light.
The anomalous X-ray pulsar XTE J1810−197 was the first magnetar found to emit pulsed radio emission. After spending almost a decade in a quiescent, radio-silent state, the magnetar was reported to ...have undergone a radio outburst in 2018 December. We observed radio pulsations from XTE J1810−197 during this early phase of its radio revival using the Ultra-Wideband Low receiver system of the Parkes radio telescope, obtaining wideband (704-4032 MHz) polarization pulse profiles, single pulses, and flux density measurements. Dramatic changes in polarization and rapid variations of the position angle of linear polarization across the main pulse and in time have been observed. The pulse profile exhibits similar structures throughout our three observations (over a week timescale), displaying a small amount of profile evolution in terms of polarization and pulse width across the wideband. We measured a flat radio spectrum across the band with a positive spectral index, in addition to small levels of flux and spectral index variability across our observing span. The observed wideband polarization properties are significantly different compared to those taken after the 2003 outburst, and therefore provide new information about the origin of radio emission.
A parameterization for the collision–coalescence process is
presented based on the methodology of basis functions. The whole drop
spectrum is depicted as a linear combination of two lognormal ...distribution
functions, leaving no parameters fixed. This basis function parameterization
avoids the classification of drops in artificial categories such as cloud
water (cloud droplets) or rainwater (raindrops). The total moment
tendencies are predicted using a machine learning approach, in which one
deep neural network was trained for each of the total moment orders
involved. The neural networks were trained and validated using randomly
generated data over a wide range of parameters employed by the
parameterization. An analysis of the predicted total moment errors was
performed, aimed to establish the accuracy of the parameterization at
reproducing the integrated distribution moments representative of physical
variables. The applied machine learning approach shows a good accuracy level when compared to the output of an explicit collision–coalescence model.
The globular cluster Omega Centauri is the most massive and luminous cluster in the Galaxy. The γ-ray source FL8Y J1326.7-4729 is coincident with the core of the cluster, leading to speculation that ...hitherto unknown radio pulsars or annihilating dark matter may be present in the cluster core. Here we report on the discovery of five millisecond pulsars (MSPs) in Omega Centauri following observations with the Parkes radio telescope. Four of these pulsars are isolated with spin periods of 4.1, 4.2, 4.6, and 6.8 ms. The fifth has a spin period of 4.8 ms and is in an eclipsing binary system with an orbital period of 2.1 hr. Deep radio continuum images of the cluster center with the Australian Telescope Compact Array reveal a small population of compact radio sources, making it likely that other pulsars await discovery. We consider it highly likely that the MSPs are the source of the γ-ray emission. The long-term timing of these pulsars opens up opportunities to explore the dynamics and interstellar medium of the cluster.
In ocean conditions of low temperature and high pressure, gas can be converted into hydrates, impacting the behavior of plumes from oil and gas blowouts. This study presented and evaluated ...formulations to parameterize the processes of formation, dissolution, and decomposition of hydrates implemented in a numerical model that simulates the fate of oil and gas releases in deepwater. Comparisons between the model results and available observations showed a good agreement. Numerical experiments were performed to understand the plume behavior with the presence of hydrates from blowouts at different depths. The analysis of the dynamics of the plume composed of water and gas showed that the hydrate formation increases the plume density and reduces its acceleration due to the buoyancy. As expected, the deeper the blowout, the greater the mass of hydrate in the plume and slower its displacement, spending more time to complete the disappearance of the hydrate.
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•Gas can combine with water around the bubbles, forming hydrates.•Low temperature and high pressure are favorable for the hydrate formation.•The hydrate changes the buoyancy of oil-gas plumes, impacting their behavior.•Parameterizations of hydrates processes are paramount in oil-gas blowout models.
Portugal, in line with the European Union, is aiming for carbon neutrality by 2050 (Net Zero), which implies a transition to sustainable energy sources. Climate change is all too evident, as extreme ...weather periods are occurring in a cyclical manner with greater brevity to such an extent that the grid operator must deal with production scenarios where it can no longer rely on hydroelectric production given the recurring drought situation. This situation increases dependence on thermal production using natural gas and imports. This has significant economic implications. Portugal has exploited its onshore wind potential, reaching an installed capacity of 5.671 MW by 2022. However, the expansion of onshore wind energy is limited to reinforcing the existing infrastructure. To overcome these challenges, it is necessary to expand the exploitation of the offshore wind potential that is already underway. This article proposes the location of offshore wind production platforms along the Portuguese coast. This allows for an analysis of offshore production and its optimization according to the minimum cost per MWh in the face of extreme scenarios, i.e., in periods of extreme drought where the hydroelectric production capacity is practically non-existent. The model is fed by using market price indications and the amount of energy needed for the following day. Using forecast data, the model adapts offshore wind production for the following day according to the minimization of the average market price. This study presents an optimization model adapted to combat the unpredictability of extreme weather conditions. This strategic framework significantly increases the resilience and reliability of offshore wind energy production, marking a significant advance in the management of renewable energy under the pressure of climate variability. The results of the simulations allow us to conclude that despite the high cost of offshore technology (in deep waters), in extreme climate scenarios, it enables cost reduction and a clear decrease in imports.
Photovoltaic microgeneration (μG) located near the domestic consumers is expected to increase more in the future. Known issues regarding high μG penetration are voltage rise and reverse power flow. ...The concept of self-consumption and storage is emerging as a way to improve network power supply quality and to facilitate the integration of small renewable energy sources in low voltage networks. This paper intends to give a further contribution by assessing the improvements provided by allowing domestic clients to consume and store the energy they produce. The tool at hand to study the situation is the unbalanced three-phase load flow algorithm, based on the power summation technique, improved with the capability of explicitly compute the neutral voltages. The behaviour of a test radial distribution grid is assessed in different operating conditions, namely winter/summer, μG penetration level and μG operating mode. Voltage profile, active power flow in the service transformer and losses are monitored. The results suggest that self-consumption with storage operating mode is a promising solution. Voltage excursions above normal grid voltage operating limits were not observed, the situation of reverse active power flow does not occur and the power losses are reduced.
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