Net Capture Research Articles

Natural Gas vs. Electricity for Solvent-Based Direct Air Capture

Removing CO2from the air with chemicals (Direct Air Capture, DAC) requires a significant amount of energy. Here, we evaluate the cost of co-constructing a solvent DAC process with its energy system. We compare eight energy systems paired with two alternative designs for a liquid-solvent DAC system capturing 1 MtCO2/year, which requires roughly 240 to 300 megawatts of steady power equivalent, 80% thermal and 20% electric. Two energy systems burn natural gas onsite for heat and electricity, capturing nearly all the CO2released during combustion, and six are all-electric non-fossil systems. The cost of the DAC facility alone contributes $310/tCO2for a conventional process-based design and $150/tCO2for a more novel design. When the decomposition of calcium carbonate occurs within a natural-gas-heated calciner, the energy system adds only $80/tCO2to these costs, assuming $3.25/GJ ($3.43/MMBtu) gas. However, leakage in the natural gas supply chain increases the cost of net capture dramatically: with 2.3% leakage (U.S. national average) and a 20-year Global Warming Potential of 86, costs are about 50% higher. For the all-electric systems, the total capture cost depends on the electricity cost: for each $/MWh of levelized cost of electricity, the total capture cost increases by roughly $2/tCO2. Continuous power is required, because the high-temperature calciner cannot be cycled on and off, so solar and wind power must be supplemented with storage. Our representative capture costs are $250–$440/tCO2for geothermal energy, $370–$620/tCO2for nuclear energy (two variants–a light water reactor and small modular nuclear), $360–$570/tCO2for wind, $430–$690/tCO2for solar photovoltaics (two variants assuming different daily solar capacities), and $300–$490/tCO2for a hybrid system with a natural-gas-powered electric calciner.

Dynamic Simulation of Space Debris Cloud Capture Using the Tethered Net

Space debris, especially the space debris cloud, has threatened severely the safety of future space missions. In the framework of multibody system dynamics, a computational approach is proposed in this study to investigate the dynamics of net deployment and capture of space debris cloud using this net subject to large overall motions and large deformations. To obtain high simulation fidelity of capturing space debris cloud, the gradient deficient beam element of the absolute nodal coordinate formulation (ANCF) is employed to discretize threads which are woven into the net. The normal contact force between the net and the debris cloud and among debris particles is computed by using the penalty method. Some deployment examples are presented to investigate the influences of shooting velocity of bullets and microgravity as well as the angle between the traveling direction of the net and the microgravity direction on the deployment characteristics of the tethered net. Other capturing examples are given to clarify the effect of the deployment area of the net at the moment it starts to contact with the debris cloud on the capture rate and to demonstrate the effectiveness of the proposed approach for capturing space debris cloud using the net in microgravity conditions.

Post-capture control of a tumbling space debris via tether tension

The Earth orbit is in a serious predicament caused by millions of space debris, and operational spacecraft are facing a risk of collision with those objects. The net capturing method has been considered as one of the most promising method to remove space debris objects. However, a tumbling target has a risk to slide toward the service satellite and collide with it after captured. To avoid this from happening, a control method must be designed for the combined system. This paper first presents the necessity of controlling the combined system right after the net capture. In another respect, the existing configurations of the combined system always include an additional mechanism to de-tumble the target which will dramatically complicate the design. Instead of using an additional mechanism, a novel control strategy is proposed to de-tumble the target only via the tether connecting to the service satellite and the target. Dynamics of the system is analyzed and flexibility of the tether is considered by employing the mass–spring–damper model. The control method includes three control modes to actively control the pose of the service satellite which significantly impacts the tether tension so that the target can be maintained a safe distance to the service satellite. Numerical simulations demonstrate that the proposed control strategy can be utilized to effectively de-tumble the target within a short period of time and mitigate the risk of collision with the service satellite.

INVENTARIO DE CARBONO EN LA RECUPERACIÓN DE PLAYAS CUBANAS

The objective of this study is to construct an inventory of carbon for the nourishment of Cuban sand beaches. It uses data of a beach nourishment project executed in 2016 in the archipelago of Jardines del Rey in Ciego de Avila, Cuba, according to an algorithm of carbon inventory for the recovery of beaches. The carbon budget was 62531.04 Mg, of which 952.36 were contained in consumed fossil fuels, 2338.95 were retained in the protected or rehabilitated vegetation, and 59239.73 Mg were retained in carbonate sands. The mole ratio in carbon compounds was used to transform the inventory into a net capture of 5084.16 Mg of carbon dioxide and the net depositions of calcium carbonate at 493652.11 Mg. These amounts were valued at 127 104.06 and 30 413 906.67 Cuban pesos, respectively. The total amounts were compared with the cost of investment. A positive net present value was deducted, representing a profitable investment in terms of carbon capture and increased carbonate sand surfaces on the studied beaches. We recommend to continue the study of sand beaches, in other to complete the inventory by our further research on carbon emission due to changes produced in the vegetation of the submarine zone.

Capture dynamics and control of tethered space net robot for space debris capturing in unideal capture case

Tethered Space Net Robot (TSNR) is proposed as a hopeful solution for space debris capturing. An unideal case of net capture is studied in this paper, in which the net does not contact the target in the center of the net. For this case, the net cannot naturally close to wrap around the target completely after collision due to the asymmetric net configuration. Therefore, an integral adaptive Super-Twisting sliding mode control (IASTSMC) is designed to close the net. The control algorithm consists of a nonlinear integral sliding surface and adaptive Super-Twisting sliding mode control (ASTSMC), which not only has the property of “saturate the large error, magnify the small error”, but also provides a positive chattering alleviation effect. Compared with the nonlinear integral sliding mode control (ISMC) with equivalent control technique and the original Super-Twisting algorithm (STA), the proposed control method shows a better performance to close the net in this unideal case.

Net Electron Capture in Collisions of Multiply Charged Projectiles with Biologically Relevant Molecules

A model for the description of proton collisions from molecules composed of atoms such as hydrogen, carbon, nitrogen, oxygen and phosphorus (H, C, N, O, P) was recently extended to treat collisions with multiply charged ions with a focus on net ionization. Here we complement the work by focusing on net capture. The ion–atom collisions are computed using the two-center basis generator method. The atomic net capture cross sections are then used to assemble two models for ion–molecule collisions: An independent atom model (IAM) based on the Bragg additivity rule (labeled IAM-AR), and also the so-called pixel-counting method (IAM-PCM) which introduces dependence on the orientation of the molecule during impact. The IAM-PCM leads to significantly reduced capture cross sections relative to IAM-AR at low energies, since it takes into account the overlap of effective atomic cross sectional areas. We compare our results with available experimental and other theoretical data focusing on water vapor (H2O), methane (CH4) and uracil (C4H4N2O2). For the water molecule target we also provide results from a classical-trajectory Monte Carlo approach that includes dynamical screening effects on projectile and target. For small molecules dominated by a many-electron atom, such as carbon in methane or oxygen in water, we find a saturation phenomenon for higher projectile charges (q=3) and low energies, where the net capture cross section for the molecule is dominated by the net cross section for the many-electron atom, and the net capture cross section is not proportional to the total number of valence electrons.

Ecology and conservation of bats in Temotu Province, Solomon Islands and Torba Province, Vanuatu

Bats are essential to the functioning of many island ecosystems. A large proportion of Pacific Island Pteropus are endemics, limited in their distribution to single paleotropical islands or close island groups. This subset is also highly threatened by hunting and habitat disturbance. Further exacerbating these threats is a dearth of scientific knowledge that makes long-term management and conservation planning difficult. We aimed to gather data on seven bat species from Nendö, Reef Islands, Tinakula, and Vanikoro (Solomon Islands), and Vanua Lava and Mota (Vanuatu). Between 1990 and 2019 we surveyed bats using walked transects, mist nets and camp counts, and collected data on diets and roosting sites. Data collection targeted four limited range endemics (Nendö tube-nosed bat (Nyctimene sanctacrucis), Banks flying-fox (Pteropus fundatus), Temotu flying-fox (Pteropus nitendiensis) and Vanikoro flying-fox (Pteropus tuberculatus), and three more widespread species (Vanuatu flying-fox (Pteropus anetianus), Pacific flying-fox (Pteropus tonganus) and Fijian blossom bat (Notopteris macdonaldi). Notopteris macdonaldi, P. nitendiensis, P. tonganus and P. tuberculatus were the most common species recorded on transects and mist net surveys. Transect encounter rates were 0.1–4.5km−1 (P. nitendiensis), 0.2–20.0km−1 (P. tonganus) and 0–7.2km−1 (P. tuberculatus). Pteropus fundatus was rarer, we did not detect this species during daytime searches, and it was the least common mist net capture. We documented 65 Pteropus food plants in our study area. Nyctimene sanctacrucis was not detected on Nendö, Tinakula and Reef Islands despite considerable effort. We consider this bat is likely extinct, if in fact it is a distinct species.

CO2 sequestration and simultaneous zeolite production by carbonation of coal fly ash: Impact on the trapping of toxic elements

Coal-fired power plants are main contributors to atmospheric CO2 emissions. They also produce huge amounts of coal fly ash (CFA) waste, which is typically landfilled, posing significant environmental risks due to its high content of potentially toxic elements (PTE). However, CFA is an alkaline aluminosilicate-rich waste, which offers the possibility of CO2 mineral capture and the production of economically-relevant mineral by-products such as zeolites. Yet, the combined carbonation and zeolite production from CFA resulting in PTE trapping has never been explored. Here we show that under mild hydrothermal conditions (150 °C) and depending of various process parameters such as pH and background alkali metal ion in (bi)carbonate solutions, a carbonation efficiency of up to 79 %, with a net CO2 mineral capture of 0.045 g/g CFA can be achieved, even when using a low Ca and Mg (3.72 wt% CaO, 1.74 wt% MgO) Class F fly ash. Moreover, amorphous zeolitic precursors and different crystalline zeolites (yield up to 60 wt%) are simultaneously obtained, and PTE in CFA are effectively trapped into the newly formed calcite, zeolitic precursors, and zeolite phases. This is the first time that a combined study of carbonation, zeolitization and PTE trapping in newly formed phases has been developed. These results have important implications for carbon capture and storage, as well as for the safe reutilization and disposal of CFA waste.

Collision Cone-Based Net Capture of a Swarm of Unmanned Aerial Vehicles

This paper addresses the problem of capturing a swarm of intruder unmanned aerial vehicles (UAVs) using a net manipulated by a team of defense UAVs. The intruder UAV swarm may be stationary, in motion, and even maneuver. The concept of collision cones in three-dimensional space is used to determine the strategy used by the net-carrying UAVs to maneuver or manipulate the net in space in order to capture the intruders. The manipulation of the net involves guiding the net to pursue the intruders and orienting it in space appropriately so as to maximize the effectiveness of capture. The net manipulation strategy is derived from the concept of collision cones defined in a relative velocity framework, and analytical expressions of nonlinear guidance laws are obtained. Simulations are presented to demonstrate the efficacy of these guidance laws.

Influence of early rearing environment on water-borne cortisol and expression of stress-related genes in grass carp (Ctenopharyngodon idella).

Nowadays, lower post-release survivorship of hatchery-reared fish in natural aquatic bodies has attained great attention and research is in progress to determine the reasons for their higher mortality. It is assumed that hatchery rearing environments negatively affect the physiological stress response of the fish. Thus, understanding how rearing environments modulate this is important for the well-being of fish. Here, an attempt has been made to assess the influence of two early rearing environments, i.e., barren (BR), mimic the conventional hatchery rearing environment; without any substrate and enrichment items and structurally enriched (ER), containing multi-colored gravel substrate, cobbles and plants, on the stress regulators i.e., HPI-axis and brain monoaminergic system of fish. Three-day old grass carp (Ctenopharyngodon idella) postlarvae were reared up to the fingerling stage in the aforementioned environments. For the stress assay, fish were subjected to net capture followed by 30min confinement in a small container at a lower water level. The pre- and post-stress responses were compared by evaluating their water-borne cortisol and the mRNA level of corticotropin releasing hormone (CRH), dopamine D1A receptor (DRD1A) and hydroxytryptamine receptor 2B (HTR2B) in the whole brain through qPCR analysis. Results of two-way ANOVA revealed significantly low (p < .001) post-stress concentration and release rate of water-borne cortisol and pre- and post-stress expression of CRH, DRD1A and HTR2B genes in the ER than BR fish. It is concluded that a structurally complex early rearing environment reduces the stress level in fish.

Rapid attitude maneuver of the space tether net capture system using active disturbance rejection control

Abstract. The space tether net capture system is a spacecraft system with a mounting tether net for capturing targets. It has the advantages of reusability and the adaptability to capture varying targets with different geometries or flying-motion statuses. However, due to its flexible tether net, the system shows strong nonlinearity, which makes it difficult to achieve the desired control performance for rapid and accurate maneuvering; moreover, this limits the ability of the tether net system to capture fast-moving targets. This paper focused on the maneuver controller design of the space capture system with a large flexible tether net. Firstly, based on the absolute node coordinate method, the dynamic model of the space tether net system is established, which can accurately describe the geometric and material nonlinearities of the space tether net. Then, a two-loop active disturbance rejection control is proposed for the rapid and high-precision maneuvering of the flexible system; meanwhile the second-order extended state observer is designed to estimate and compensate for the tether net vibration disturbance. The simulation validated the proposed control, which could complete the rapid and accurate maneuvering and also compensate for the disturbance caused by the vibration of the flexible tether net.

Electron capture and ionization cross-section calculations for proton collisions with methane and the DNA and RNA nucleobases

Net ionization and net capture cross-section calculations are presented for proton collisions from methane molecules and the DNA/RNA nucleobases adenine, cytosine, guanine, thymine, and uracil. We use the recently introduced independent-atom-model pixel counting method to calculate these cross sections in the 10 keV to 10 MeV impact energy range and compare them with results obtained from the simpler additivity rule, a previously used complete-neglect-of-differential-overlap method, and with experimental data and previous calculations where available. It is found that all theoretical results agree reasonably well at high energies, but deviate significantly in the low-to-intermediate energy range. In particular, the pixel counting method which takes the geometrical overlap of atomic cross sections into account is the only calculation that is able to describe the measurements for capture in proton-methane collisions down to 10 keV impact energy. For the nucleobases it also yields a significantly smaller cross section in this region than the other models. New measurements are urgently required to test this prediction.

Cost, energy and GHG emission assessment for microbial biodiesel production through valorization of municipal sludge and crude glycerol.

In this study, cost simulations were made based on 20 million L blended biodiesel B-10 production per year using INRS and conventional process. In case of INRS process, microbial lipid was produced by T. oleaginosus using washed municipal secondary sludge fortified with crude glycerol while lipid was extracted from wet biomass using biodegradable surfactant and petroleum-diesel (PD). The conventional process uses commercial substrates for lipid production and organic solvents for lipid extraction from dry biomass. The unit B-10 production cost of INRS process was estimated to be $ 0.72/L for an annual capacity of 20 million L, which is 9.5 times more economical than conventional biodiesel production process. For INRS process, the unit B-10 biodiesel production cost was sensitive to plant capacity and lipid productivity during the fermentation. INRS process exhibited positive net energy gain and positive GHG capture, which proves to be energetically and environmentally viable.

Design and optimization of a space net capture system based on a multi-objective evolutionary algorithm

Space net capture is an innovative concept for active debris removal that provides a prospective method for the removal of large, non-cooperative space targets. The design of a space net capture system must meet two basic requirements: maximizing the capture ability and minimizing the system cost. This paper presents an inexpensive multi-objective optimization framework to solve this design problem. In this framework, a design optimization approach using a lumped parameter modelling method as well as an improved inexpensive multi-objective optimization algorithm is proposed. The system mass and effective distance are chosen as objectives of this optimization problem. The simulation results reveal that the multi-objective optimization framework is feasible and effective for the design of a space net capture system, and the designer preferred solutions that enhance system design are reliably identified.

The active space debris removal mission RemoveDebris. Part 1: From concept to launch

This is the first of two companion papers that describe the development of the RemoveDEBRIS; mission. This first article focusses on the mission design and hardware development up to the delivery of the spacecraft to the launch authority. The Second article describes the in-orbit operations.The European Commission funded RemoveDebris mission has been the world's first Active Debris Removal (ADR) missions to demonstrate, in orbit, some cost effective key technologies, including net and harpoon capture; and elements of the whole sequence of operations, like the vision-based navigation, ultimately planning to terminate the mission with the deployment of the dragsail to de-orbit the craft. The mission has utilised two 2U CubeSats as artificial debris targets released from the main 100 kg satellite, to demonstrate the various technologies.This paper examines the design of the mission from initial concepts through to Manufacture, Assembly Integration and Testing of the payloads, up to launch, and apart from a general consideration of the mission, will focus on the elements of design and testing that differ from a conventional mission.

Simulation of a calcium looping CO2 capture process for pressurized fluidized bed combustion

The Canadian regulations on carbon dioxide emissions from power plants aim to lower the emissions from coal‐fired units down to those of natural gas combined cycle (NGCC) units. Since coal is significantly more carbon intensive than natural gas, coal‐fired plants must operate at higher net efficiencies and implement carbon capture to meet the new regulations. Calcium looping (CaL) is a promising post‐combustion carbon capture (PCC) technology that, unlike other capture processes, generates additional power. By capturing carbon dioxide at elevated temperatures, the energy penalty that carbon capture technologies inherently impose on power plant efficiencies is significantly reduced. In this work, the CO2 capture performance of a calcium‐based sorbent is determined via thermogravimetric analysis under relatively high carbonation and low calcination temperatures. The results are used in an aspenONE™ simulation of a CaL process applied to a pressurized fluidized bed combustion (PFBC) system at thermodynamic equilibrium. The combustion of both natural gas and coal are considered for sorbent calcination in the CaL process. A sensitivity analysis on several process parameters, including sorbent feed rate and carbonator operating pressure, is undertaken. The energy penalty associated with the capture process ranges from 6.8–11.8 percentage points depending on fuel selection and operating conditions. The use of natural gas results in lower energy penalties and solids circulation rates, while operating the carbonator at 202 kPa(a) results in the lowest penalties and drops the solids circulations rates to below 1000 kg/s.

ARTROPODOFAUNA CADAVÉRICA ASOCIADA A Sus scrofa L. EN EL SUR DE URUGUAY

Forensic Entomology is the branch of science that uses arthropods as a tool in research when classical forensic methods are insufficient. It is thus that this branch represents an invaluable aid in cases where the human remains are colonized by insects. The most important contribution of forensic entomology is associated with the estimation of the post-mortem interval since some species of the sarcosaphage community are associated with specific stages of the decomposition process. The Artropodofauna cadaverica decomposing organic remains, both animal and human, undergo a series of physical, chemical and biological changes, transforming it into a nutritionally rich but provisional resource, for different taxa of animals. During the decomposition process, the orders Diptera, Coleoptera and Hymenoptera, are predominant in diversity and abundance. The objective of this work is to present the first seasonal study of cadaveric arthropodofauna on experimental porcine models in a forest environment for Southern Uruguay. For this, two specimens of white pig (Sus scrofa L.) were used as biological model. A malaise trap, entomological net and manual capture were used for the capture of adult insects. A total of 2926 adults was collected from three orders and 14 families. The greatest species richness was observed in the summer season and in the lower spring.

Performance evaluation of novel wet vibrational precipitator

ABSTRACT This study reports the development, construction, and initial testing of a novel vibrational precipitator (VP), patented at Ohio University in 2016, that uses vibrating metal cables with water running over them to capture particulate matter in an exhaust stream. Unlike traditional electrostatic precipitators relying on electric energy to capture particles, this new system uses the concept of vortex shedding to produce vibrations in vertical cables running perpendicular to an exhaust stream. Collisions between particles in the exhaust stream and these vibrating cables cause the particles to land onto a thin film of flowing water around the cables, which carries the particles downward for collection and removal. Initial tests with air containing particulates of 3 micron average particle size show capture efficiencies up to 54% using U.S. Environmental Protection Agency (EPA) Method 5 to measure the particulate concentrations at the upstream and downstream of a VP comprising 8 cells. These results show that this system, without consuming any electric energy, has a significant potential to be a simple and cost-effective way to treat particle-laden exhaust gases. Implications: In this work, for the first time, a novel precipitator is investigated that captures particles without using any particle charging and (hence) any electricity. The capture mechanism is governed by vibrations of collection electrodes, which are vertical steel cables wetted through continuous flow of water. Without any discharge electrodes, electrode suspension mechanism, and ability of the system to be installed in existing ducts, the novel precipitator becomes a simple chamber housing containing multiple collection electrode cells. The preliminary results show that this new technology can achieve net particulate matter capture efficiency of 54%. This paves a pathway forward for reducing capital and operating cost of air pollution control systems.

Reduced stress response in juvenile Chinook Salmon reared with structure

Understanding how rearing environments influence the stress response is relevant to many fish management practices. This is particularly relevant in aquaculture, where it is important to be able to minimize the effects of stress to enhance animal wellbeing. The stress response is also interesting from a basic science perspective, where it is important to understand how environmental differences can influence phenotypic traits and the physiological reaction to stressors. We tested the hypothesis that rearing fish in a more complex environment would reduce their stress response when presented with stressors. Specifically, we tested for the effect of structure in rearing tanks on the stress response of juvenile Chinook Salmon (Oncorhynchus tshawytscha) exposed to a handling and crowding stressor, something like hatchery fish might experience during transportation to new locations. For both rearing treatments (with and without structure), we compared fish that were subjected to the stressor to fish sampled from the respective rearing tank as the control. For the stressed treatment, we subjected fish to net capture followed by three hours in lowered water levels in a novel tank and then moved to a second novel holding tank. This process was designed to mimic typical stressors fish may experience at a hatchery. We analyzed plasma collected before the start of the stressor, during the stressor, and throughout 20 h post-stressor for cortisol in both stressed and unstressed fish. For both rearing treatments, fish that experienced the stressor had elevated plasma cortisol compared to control fish. However, the cortisol levels of fish in the stressed treatment reared with structure were significantly less than fish reared without structure. Additionally, plasma cortisol levels in structure-reared fish returned to baseline by 20 h post-stress while fish reared without structure had not fully recovered. Our findings suggest that increasing complexity of the rearing environment might be advantageous as a way of minimizing effects of handling-type stressors.

Atmospheric net particle accumulation on 96 plant species with contrasting morphological and anatomical leaf characteristics in a common garden experiment

Urban green spaces function as biological filters in reducing atmospheric particles. Yet there is a profound requisite to identify the most effective plant species by their leaf traits that can enhance particle capture and improve ambient air quality. In this study, we investigated leaves of 96 perennial urban plant species consisting of 43 deciduous broadleaf trees, 32 deciduous broadleaf shrubs, 14 deciduous and evergreen needle/scale-like, 5 evergreen broadleaves, and 2 climber species for their differences in net particle accumulation. Leaf saturation isothermal remanent magnetization (SIRM), a proxy for traffic and industry induced particle accumulation, along with morphological and anatomical leaf traits were analyzed in a common garden experiment in June and September 2016. Leaf SIRM varied significantly between plant species. The most effective net particle accumulating plant species with a median value of 23.0 μA were Buddleja davidii, Viburnum opulus, Carpinus betulus, Quercus ilex, Viburnum lantana, Rosa rugosa, Sorbus aria, Aesculus hippocastanum, Pseudotsuga menziesii, Acer campestre. The least effective net particle accumulating plant species with a median value of 10.4 μA were Populus alba, Alnus glutinosa, Larix kaempferi, Larix decidua, Plantanus x acerilifolia, Acer pseudoplatanus, Robinia pseudoacacia, Quercus palustris, Rosa canina, Liquidambar styraciflua. The “variable importance” in net particle accumulation for the investigated plant species was achieved using ®randomForest. The presence of leaf trichomes and specific leaf area were identified as important leaf traits for categorization of the selected plant species in low, medium, and high net particle accumulators. The extensive analysis of plant species at leaf-level with distinct micro-morphology contributes to a better understanding of plant species behavior in net particle capture and their contribution in reducing atmospheric particulate matter. Furthermore, this study has practical implications for policymakers in making informed choices when planning urban green infrastructures. Lastly, our study can become a basis to validate atmospheric deposition model using species-specific information.