Long-period Energy Research Articles

Long-period energy releases during a C2.8 flare

Context. The study of quasi-periodic pulsations (QPPs) is a key diagnostic of intermittent or periodic energy releases during solar flares. Aims. We investigated the intermittent energy-releasing processes by analyzing the long-period pulsations during a C2.8 flare on 2023 June 3. Methods. The solar flare was simultaneously observed by the solar X-ray detector on board the Macau Science Satellite-1B, the Geostationary Operational Environmental Satellite, the Chinese Hα Solar Explorer, the Expanded Owens Valley Solar Array, the Atmospheric Imaging Assembly, and the Extreme Ultraviolet Variability Experiment for the Solar Dynamics Observatory. Results. The C2.8 flare shows three successive and repetitive pulsations in soft X-ray (SXR) and high-temperature extreme ultraviolet (EUV) emissions, which may imply three episodes of energy releases during the solar flare. The QPP period is estimated to be as long as ∼7.5 minutes. EUV imaging observations suggest that these three pulsations come from the same flare area dominated by the hot loop system. Conversely, the flare radiation in wavelengths of radio/microwave, low-temperature EUV, ultraviolet (UV), and Hα only reveals the first pulsation, which may be associated with nonthermal electrons accelerated by magnetic reconnection. The other two pulsations in wavelengths of SXR and high-temperature EUV might be caused by the loop-loop interaction. Conclusions. Our observations indicate that the three episodes of energy releases during the C2.8 flare are triggered by different mechanisms, namely the accelerated electron via magnetic reconnection, and the loop-loop interaction in a complicated magnetic configuration.

Dissecting Earth's Magnetosphere: 3D Energy Transport in a Simulation of a Real Storm Event

AbstractWe present new analysis methods of 3D MHD output data from the Space Weather Modeling Framework during a simulated storm event. Earth's magnetosphere is identified in the simulation domain and divided based on magnetic topology and the bounding magnetopause definition. Volume energy contents and surface energy fluxes are analyzed for each subregion to track the energy transport in the system as the driving solar wind conditions change. Two energy pathways are revealed, one external and one internal. The external pathway between the magnetosheath and magnetosphere has magnetic energy flux entering the lobes and escaping through the closed field region and is consistent with previous work and theory. The internal pathway, which has never been studied in this manner, reveals magnetically dominated energy recirculating between open and closed field lines. The energy enters the lobes across the dayside magnetospheric cusps and escapes the lobes through the nightside plasmasheet boundary layer. This internal circulation directly controls the energy content in the lobes and the partitioning of the total energy between lobes and closed field line regions. Qualitative analysis of four‐field junction neighborhoods indicate the internal circulation pathway is controlled via the reconnection X‐line(s), and by extension, the interplanetary magnetic field orientation. These results allow us to make clear and quantifiable arguments about the energy dynamics of Earth's magnetosphere, and the role of the lobes as an expandable reservoir that cannot retain energy for long periods of time but can grow and shrink in energy content due to mismatch between incoming and outgoing energy flux.

Techno-economic analysis to identify the optimal conditions for green hydrogen production

The intermittency of renewable energy sources necessitates energy storage to meet the full demand and balancing requirements of the grid. Green hydrogen (H2) is a chemical energy carrier that can be used in a flexible manner and store large amounts of energy for long periods of time. This techno-economic analysis investigates H2 production from wind using commercially available desalination and electrolysis units. Proton exchange membrane and alkaline electrolyser units are utilised and compared. The intermittency of wind is examined, with comparison against grid-bought electricity. A model is developed to determine the selling price required to ensure profitability over a 10-year period. Firstly, where H2 is produced using energy from the grid, with electricity purchased when below a specified price point or between specified hours. In the second scenario a wind turbine is owned by the user and the electricity price is not considered, while the turbine capital expenditure is. The price of H2 production from wind is found to be comparable with natural gas derived H2 at a larger scale, with a minimum selling price calculated to be 4.85 £/kg at a setpoint of 500 kg of H2/hr. At a setpoint of 50 kg of H2/hr, this is significantly higher at 12.10 £/kg. In both cases, the alkaline electrolyser produced cheaper H2. This study demonstrates an economy of scale with H2 prices decreasing with increased scale. H2 prices are also closely linked to the capital expenditure, with the equipment size, space and safety identified as limiting factors.

The potential of retrofitting existing coal power plants: A case study for operation with green iron

Storing electrical energy for long periods and transporting it over long distances is an essential task of the necessary transition to a CO2-free energy economy. An oxidation–reduction cycle based on iron and its oxides represents a very promising technology in this regard. The present work assesses the potential of converting an existing modern coal-fired power plant to operation with iron. For this purpose, a systematic retrofit study is carried out, employing a model that balances all material and energy fluxes in a state-of-the-art coal-fired power plant. Particular attention is given to components of the burner system and the system’s heat exchanger. The analysis provides evidence that main components such as the steam generator and steam cycle can be reused with moderate modifications. Major modifications are related to the larger amounts of solids produced during iron combustion, for instance in the particle feeding and removal systems. Since the high particle densities and lower demand for auxiliary systems improve the heat transfer, the net efficiencies of iron operation can be one to two percentage points better than coal operation, depending on operating conditions. This new insight can significantly accelerate the introduction of this innovative technology by guiding future research and the development of the retrofit option.

Controlling persistent luminescence in nanocrystalline phosphors.

Persistent luminescent phosphors can store light energy in advance and release it with a long-lasting afterglow emission. With their ability to eliminate in situ excitation and store energy for long periods of time, they are promising for broad applications, including background-free bioimaging, high-resolution radiography, conformal electronics imaging and multilevel encryption. This Review provides an overview of various strategies for trap manipulation in persistent luminescent nanomaterials. We highlight key examples in the design and preparation of nanomaterials with tunable persistent luminescence, particularly in the near-infrared range. In subsequent sections, we cover the most current developments and trends concerning the use of these nanomaterials in biological applications. Moreover, we assess their advantages and disadvantages compared with conventional luminescent materials for biological applications. We also discuss future research directions and challenges, such as insufficient brightness at the single-particle level, and possible solutions to these challenges.

High-resolution mid-mantle imaging with multiple-taper SS-precursor estimates

SUMMARY SS-precursor imaging is used to image sharp interfaces within Earth’s mantle. Current SS-precursor techniques require tightly bandpassed signals (e.g. 0.02–0.05 Hz), limiting both vertical and horizontal resolutions. Higher frequency content would allow for the detection of finer structure in and around the mantle transition zone (MTZ). Here, we present a new SS-precursor deconvolution technique based on multiple-taper correlation (MTC). We show that applying MTC to SS-precursor deconvolution can increase the frequency cut-off up to 0.5 Hz, which potentially sharpens vertical resolution to ∼10 km. Furthermore, the high-pass frequency can be lowered (≪ 0.01 Hz), allowing more long-period energy to be included in the calculation, to better constrain the signal and reduce side lobes. Our method is benchmarked on full-waveform synthetic seismograms computed via AxiSEM3D for the PREM 1-D Earth model. We apply our novel MTC-SS-precursor deconvolution to ∼7000 seismograms recorded at broad-band borehole sensors of the Global Seismographic Network with source–receiver bounce points in the North-Central Pacific Ocean. The MTZ in this region appears to be thin, which agrees with previous results. We do not observe the 520-km discontinuity in our SS-precursor estimates. Additionally, we detect a low-velocity zone above the MTZ to the north of the Hawaiian Islands that has previously been inferred from asymmetry in side lobe amplitudes. Our high-frequency analysis demonstrates this feature to be a sharp interface (≤ 10-km thickness), rather than a thick wave speed gradient.

Supercooled sodium acetate aqueous solution for long-term heat storage to support heating decarbonisation

Heating decarbonisation through electrification requires the development of novel heat batteries. They should be suitable for the specific application and match the operation conditions of domestic renewable energy sources. Supercooled liquids, often considered a drawback of phase change materials, are among the most promising technologies supporting heating decarbonisation. Although some studies have shed light on stable supercooling, the fundamentals and stability remain open problems not always accompanied by relevant experimental investigations. This research critically analyses the physic and chemistry of sodium acetate (SA, NaCH3COO) aqueous solution, a low-cost, non-toxic, and abundant compound with stable supercooling for long-term heat storage. It has an appropriate phase change temperature for high-density heat storage using heat pumps or solar thermal technologies in residential applications. The existing discrepancies in literature are critically discussed through a systematic experimental evaluation, providing novel insights into efficient material design and appropriate boundary conditions for reliable material use in long-term heat batteries. Despite previous studies showing that the thermal reliability and stability of sodium acetate aqueous solution as a supercooled liquid for heat storage cannot be guaranteed, this study demonstrates that through an appropriate encapsulation and sealing method, the peritectic composition of sodium acetate solution (p-SA 58 wt%) can be used as a supercooled liquid for long-term heat storage with a stable melting temperature of 57 °C, appropriate for domestic heat technologies. It is demonstrated that energy storage efficiency can be maintained under cycling, with a constant latent heat storage capacity of 245 kJ/kg and a volumetric storage density of 314 MJ/m3. It was confirmed that the material should achieve a fully-melted state for stable supercooling. Finally, local cooling and retaining seed crystals through high pressure were highlighted as the most suitable basic principles for successful crystallization and heat release. This promising material can store energy for long periods without latent heat losses due to its stable subcooling. Latent heat can be released when required at any selected time and temperature just by a simple activation process.

A Molten-Salt Battery for Seasonal Energy Storage

Cost-competitive renewable energy sources, such as wind and solar energy, are more rapidly replacing fossil fuels for power generation. As their integration into the power grid increases, the inherent intermittency exposes a great challenge in maintaining the grid stability. Therefore, the development of low-cost energy storage technology suitable for large-scale manufacturing is essential for the further deployment of renewable energy. We noticed that renewable electricity production usually follows predictable seasonal trends. For example, the longer daylight in summers corresponds to more solar power generated. If any seasonal excess can be efficiently stored and redistributed in times of needs, a power grid based on 100% renewable energy is more feasible. Unfortunately, current rechargeable battery technologies have not been optimized for seasonal storage, as the self-discharge rate ranges from approximately 3–5% for lithium-ion batteries to almost 30% for nickel metal hydride batteries in the first month.In this presentation, we will demonstrate the concept of a rechargeable molten-salt battery with earth-abundant elements and simple construction that preserve the stored energy for long periods of time. Due to its unique operating mechanism, this battery can discharge most of its stored capacity (> 90%) after a period of 1 to 8 weeks. This approach brings new possibilities to seasonal energy storage and helps the grid to overcome short supply during seasonal fluctuations.

Wave dispersion and dissipation in landfast ice: comparison of observations against models

Abstract. Observations of wave dissipation and dispersion in sea ice are a necessity for the development and validation of wave–ice interaction models. As the composition of the ice layer can be extremely complex, most models treat the ice layer as a continuum with effective, rather than independently measurable, properties. While this provides opportunities to fit the model to observations, it also obscures our understanding of the wave–ice interactive processes; in particular, it hinders our ability to identify under which environmental conditions these processes are of significance. Here, we aimed to reduce the number of free variables available by studying wave dissipation in landfast ice. That is, in continuous sea ice, such as landfast ice, the effective properties of the continuum ice layer should revert to the material properties of the ice. We present observations of wave dispersion and dissipation from a field experiment on landfast ice in the Arctic and Antarctic. Independent laboratory measurements were performed on sea ice cores from a neighboring fjord in the Arctic to estimate the ice viscosity. Results show that the dispersion of waves in landfast ice is well described by theory of a thin elastic plate, and such observations could provide an estimate of the elastic modulus of the ice. Observations of wave dissipation in landfast ice are about an order of magnitude larger than in ice floes and broken ice. Comparison of our observations against models suggests that wave dissipation is attributed to the viscous dissipation within the ice layer for short waves only, whereas turbulence generated through the interactions between the ice and waves is the most likely process for the dissipation of wave energy for long periods. The separation between short and long waves in this context is expected to be determined by the ice thickness through its influence on the lengthening of short waves. Through the comparison of the estimated wave attenuation rates with distance from the landfast ice edge, our results suggest that the attenuation of long waves is weaker in comparison to short waves, but their dependence on wave energy is stronger. Further studies are required to measure the spatial variability of wave attenuation and measure turbulence underneath the ice independently of observations of wave attenuation to confirm our interpretation of the results.

A Review on the Challenges of Using Zeolite 13X as Heat Storage Systems for the Residential Sector

In recent years, several attempts have been made to promote renewable energy in the residential sector to help reducing its CO2 emissions. Among existing approaches utilizing substances capable of directly storing and transporting thermal energy has recently become a point of interest. Zeolite 13X with exceptional capacity to safely store thermal energy for long periods and release heat due to its unique molecular structure is known to be one of the best options serving this purpose. However, the application of this ceramic as a heat storage material in the residential sector is associated with significant challenges dictated by the limitations of the sector, such as space restrictions and affordability. The current review attempts to explore the extent of these challenges, mainly related to design and efficiency from different perspectives. The main aim here is to provide a clear vision for a better understanding of the state of the art of this technology and to help to identify possible solutions fostering the adaptation of this technology to the residential sector.

Risk Transfer in an Electricity Market

Energy is traded using different products; long-term contracts or electricity forward contracts can assure the future transaction price. However, due to the difficulties in storing electrical energy for long periods and in large amounts, risks must be incorporated when defining contract prices through a Forward Risk Premia (FRP). This study analyzes the transfer of uncertainty from electricity market variables to the FRP in long-term contracts. We evaluate a type of econometric risk with the construction of Autoregressive Distributed Lag contagion models for the FRP using electricity demand, spot price, power generation via different technologies, and the Oceanic Niño Index. As a case study, we consider the Colombian electricity market. Our results show empirical models where the FRP has a short-term response with the following variables: hydropower generation, coal power generation, electricity demand, and Oceanic Niño Index, even though its transaction is reflected one or two years after the occurrence of the event.

Algorithm for optimal pairing of res and hydrogen energy storage systems

The global climate and environmental crisis dictate the need for the development and implementation of environmentally friendly and efficient technical solutions, for example, generation based on renewable energy sources. However, the annually increasing demand for electricity (according to the forecasts of the U.S. Energy Information Administration, the amount of energy consumed for the period 2006–2030 will increase by 44 %) cannot be fully provided by alternative energy. The main reason is not so much the high cost of these technologies, like unstable power generation, which determines the need for an additional reserve of regulated power.The solution to this problem can be the combined use of generation based on renewable energy sources with energy storage units of large capacity. Currently, a promising direction is the use of excess electricity for the production of hydrogen and its further accumulation in hydrogen storage. In this case an additional energy can be generated using industrial fuel cells (electrochemical generators) to compensate for the power shortage.At the same time, the distinctive advantage of hydrogen energy storage systems lies in the ability to accumulate a large amount of energy for long periods of time. This fact makes it possible to increase the reliability of the functioning of the electric power system, to provide power supply with a sufficiently long interruption (in case of faults) or allocation for isolated operation.With an increase in the unit capacity and the share of renewable generation in the total installed capacity, researches that aimed to systematic analysis of the impact of the implemented generation unit and the energy storage system on the parameters of the mode of the electric power system become more relevant. There are a number of tasks can be noted related to determining the optimal location and size of the generation unit and energy storage systems being implemented in terms of reducing power losses and maintaining an appropriate voltage level in the nodes of the electric power system. In this article, a variant of solving the optimization task for a typical 15-bus IEEE scheme is presented by means of software calculation using the bubble sorting method. To achieve this goal, the following tasks were solved: the objective function, which indicates the optimal location and size of the generation unit, and constraints, for example, the available deviation of voltage level, were formed; the software implementation of the algorithm for calculating power flows and power losses using the bubble sorting method was carried out. The results of the work of the program code for two scenarios are presented: for instance, installation of one renewable generation unit with a different range of possible capacities, and are compared with the data obtained in the MATLAB/Simulink software package.

Prolonging WSNs lifetime in IoT applications based on consistent algorithm

The rapid expansion in the use of IoT imposes the importance of developing its infrastructure. One of the most important components in IoT infrastructures is the wireless sensor networks. The development of these networks largely depends on how to extend their life. As one of the effective options adopted in this field is the use of cluster heads (CHs). This paper introduces an algorithm that efficiently determine the CHs by iteratively extracting an associative value for each node depending on two factors; node's residual energy, and geometrical distances between nodes and base station. In light of the extracted values, the nodes with the best associative values are elected as CHs based on adjustable threshold determined according to the network usage requirements. The algorithm has proven a significant increase in the lifetime of the network, as well as, it has proven its ability to maintain a high level of energy for long period of time. The proposed algorithm outperformed similar protocols like low energy adaptive clustering hierarchy (LEACH) and region based low energy adaptive clustering hierarchy (R-LEACH) by prolonging the network lifetime and increasing network stability, as well as enhances the throughput significantly.

Adsorption Characteristics of Zeolite A Synthesized from Wassa Kaolin for Thermal Energy Storage

Zeolites based on the numerous applications can be utilised in providing solutions to some challenges of our world. With the ability to store thermal energy as chemical potential, zeolites are able to store thermal energy for long periods. This can occur with very minimal loss of energy and indefinitely unless the zeolite comes into contact with an adsorbate. The use of zeolite - water as adsorbent - adsorbate pair in thermal energy storage (TES) applications have been studied and have shown good results. However, the cost of zeolites synthesized from reagents continue to hamper the effective use of this adsorbent. Zeolite A was synthesized from kaolin from Wassa in Ghana based on a modified synthesis route. The adsorption properties of the zeolite utilising a designed and fabricated TES system using amounts of 100g, 200g, 300g, 400g and 500g of zeolite with a 1:1.5 ratio to water. Adsorption isosteres were plotted with the temperature and pressure values recorded and results showed correlation to adsorption behaviour of zeolites. Langmuir adsorption isotherms with r-squared values greater than 90% confirmed the affinity of water for zeolites. isosteric heat of adsorption was calculated with the minimum being 5,655.84 J/g and the maximum being 8,113.44 J/g. This confirms that the Zeolite A synthesized from Was kaolin has the structural properties needed for TES applications.

Indirect integration of thermochemical energy storage with the recompression supercritical CO2 Brayton cycle

Dispatchability is a major technological obstacle for concentrated solar power (CSP) plants. Calcium looping (CaL) is a potential solution for storing solar energy for long periods using raw materials (e.g., natural limestone or dolomite) which are high energy density, widespread availability, and low cost. This study aimed to propose a CSP-CaL plant indirectly integrated with the recompression supercritical CO2 Brayton cycle to realize carbonation under atmospheric pressure. To understand this indirect integration, the thermodynamic models are developed in Aspen and Matlab. The results show that the considered system can achieve storage exergy efficiency in the range of 8.26–16.34%, and power exergy efficiency in the range of 13.6–23.85%. In addition, a sensitivity analysis reveals that the storage exergy efficiency is largely determined by reaction temperature and conversion. Its value decreases with calcination temperature, and increases with carbonation temperature and CaCO3 conversion. Besides, it is found that the power exergy efficiency increase with an increase in power conditions (cycle low pressure, intermediate cycle pressure, and cycle high pressure) initially. However, above a certain pressure (80, 170, 210 bar, respectively), further increase leads to a decrease in power exergy efficiency. The results also indicate that high reaction temperature has a positive effect on power exergy efficiency. Compared to the molten-salt-based and direct integration, this CSP-CaL indirect integration offers competitive performance and promising potential for the commercialization of CSP-CaL systems in the near future.

Active Power Control based on Hydrogen Availability in a Storage Power Plant

The concept of Electrical Energy Storage (EES) has progressively gained prominence as a means to large-scale integration of intermittent Renewable Energy Sources (RES). The Storage Power Plant (SPP), which uses hydrogen as its primary fuel, is one such solution that can autonomously supply or store electrical energy in bulk according to the requirements of the network. Previous investigations have verified the ability of such a power plant to provide the required ancillary services in order to ensure a secure electrical power supply system. However, one aspect that has remained untested is the effect of diminishing or excess stored hydrogen on the operation of this power plant. In practice, the SPP can be exposed to such extreme situations when it is required to generate or store energy for long periods. Thus, in this paper, a controller model has been recommended which can protect the SPP system when the hydrogen mass in its storage reaches alarming levels. Based on the control mechanism, whenever the hydrogen mass in its storage is about to surpass the upper or lower permissible limits, the SPP can seamlessly transition from one mode to another and adjust its power output. This enables the SPP to regulate the level of its stored hydrogen mass.

Controlling heat release of crystallization from supercooling state of a solid-solid PCM, 2-amino-2-methyl-1,3-propanediol

The use of phase change materials (PCMs) for heat storage and as a heat source has become an important aspect for energy management. Some PCMs store energy when in a non-equilibrium state (a supercooling state), and supply energy when released from this state. This means PCMs have the ability to sustain heat energy for long periods and select the heat supply timing. 2-amino-2-methyl-1,3-propanediol (AMP), a solid-solid PCM, stores about 264 J/g of heat energy at the crystal transition temperature of about 78 °C. AMP has the attractive characteristic of storing heat energy in its solid supercooling state, similar to solid-liquid PCMs. In addition, AMP crystallizes from the supercooling state and releases heat energy of about 140 J/g during the heating process. These positive attributes make AMP a good candidate to assist in heating a system. This study applied this characteristic to methods handling the exoergic heat energy of the crystallization of AMP. First, the thermal properties are studied by DSC measurement and thermal cycle tests in different mass conditions. Second, the crystallization is investigated by observation of crystal growth. The results show that the supercooling state crystallizes with exoergic heat during the heating process. It turns out that the crystal nucleation rate (1/s) highly depends on the temperature and AMP mass. The crystal growth rate (μm/s) is acquired in this experiment. By using this information, it is possible to handle the exoergic heat of the crystallization from the supercooling state by changing the AMP mass and minimum temperature during cooling. Moreover, the heat energy that is kept in the supercooling state can be also controlled by crystal nucleus addition or impact.

Complex rupture of the 13 November 2016 Mw 7.8 Kaikoura, New Zealand earthquake: Comparison of high-frequency and low-frequency observations

We apply a back-projection analysis to determine the locations and timing of the sources of short-period (0.5 to 2 s) energy generated by the 13 November 2016 Mw 7.8 Kaikoura, New Zealand earthquake using data from Australian and Southeast Asia. The sources of strong short-period energy are distributed northeast of the epicenter at distances of 70 to 80 km during the time period of 70 to 80 s after the initiation. The locations of sources of long-period energy derived from global seismic and local GPS data are close to the northeastern edge of the source area, and complementary to the areas of short-period energy which occur in the converging region of the Upper Kowhal, Papatea, and Jordan Thrust faults. The obvious frequency dependence might be attributed to complexities in fault geometry, possible rupture in the subduction interface, or varying focal mechanisms during the earthquake.

Male reproductive cycle of hibernating Korean greater horseshoe bat, Rhinolophus ferrumequinum korai (Chiroptera: Rhinolophidae): annual cycle of the seminiferous epithelium and morphological changes of the testes

Morphological changes of testes and the annual cycle of the seminiferous epithelium were observed by optical and transmission electron microscopy to determine the male reproductive cycle of the Korean greater horseshoe bat, Rhinolophus ferrumequinum korai. In this study, R. ferrumequinum korai showed a distinct reproductive cycle, unlike other hibernating bat species. The testicular reproductive cycle of R. ferrumequinum korai consists of three main stages. The first is the spermatogenesis stage (from April to September), including spermatocytogenesis (which appears from April to May) and spermiogenesis (from June to September). The activity of spermatogenesis was highest in August. The lumen of seminiferous tubules was open from mid-April to mid-October. It was closed from November to March of the following year. The second stage is the phagocytosis stage (from mid-October to mid-November), which is a purification process to prepare for new spermatogenesis the following year. This period is called the cleansing period. The third is the dormant stage – that is, a state of holding only spermatogonia and Sertoli cells. It is an adaptation strategy to store energy for long periods of hibernation. Compared to previous studies, spermatogenesis period preceded 1 month earlier. This suggests that temperature increase can impact reproductive development and spermatogenesis.

Detailed investigation of Long-Period activity at Campi Flegrei by Convolutive Independent Component Analysis

This work is devoted to the analysis of seismic signals continuously recorded at Campi Flegrei Caldera (Italy) during the entire year 2006. The radiation pattern associated with the Long-Period energy release is investigated. We adopt an innovative Independent Component Analysis algorithm for convolutive seismic series adapted and improved to give automatic procedures for detecting seismic events often buried in the high-level ambient noise. The extracted waveforms characterized by an improved signal-to-noise ratio allows the recognition of Long-Period precursors, evidencing that the seismic activity accompanying the mini-uplift crisis (in 2006), which climaxed in the three days from 26–28 October, had already started at the beginning of the month of October and lasted until mid of November. Hence, a more complete seismic catalog is then provided which can be used to properly quantify the seismic energy release. To better ground our results, we first check the robustness of the method by comparing it with other blind source separation methods based on higher order statistics; secondly, we reconstruct the radiation patterns of the extracted Long-Period events in order to link the individuated signals directly to the sources. We take advantage from Convolutive Independent Component Analysis that provides basic signals along the three directions of motion so that a direct polarization analysis can be performed with no other filtering procedures. We show that the extracted signals are mainly composed of P waves with radial polarization pointing to the seismic source of the main LP swarm, i.e. a small area in the Solfatara, also in the case of the small-events, that both precede and follow the main activity. From a dynamical point of view, they can be described by two degrees of freedom, indicating a low-level of complexity associated with the vibrations from a superficial hydrothermal system. Our results allow us to move towards a full description of the complexity of the source, which can be used, by means of the small-intensity precursors, for hazard-model development and forecast-model testing, showing an illustrative example of the applicability of the CICA method to regions with low seismicity in high ambient noise.