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4 pages, 147 KiB

Open AccessEditorial

Special Issue on Plasma Processes for Renewable Energy Technologies

by Masaaki Okubo

Energies 2019, 12(23), 4416; https://doi.org/10.3390/en12234416 - 20 Nov 2019

Viewed by 1474

Abstract

The use of renewable energy is an effective solution to mitigate global warming [...] Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

Research

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13 pages, 4775 KiB

Open AccessArticle

High Reduction Efficiencies of Adsorbed NO_x in Pilot-Scale Aftertreatment Using Nonthermal Plasma in Marine Diesel-Engine Exhaust Gas

by Takuya Kuwahara, Keiichiro Yoshida, Tomoyuki Kuroki, Kenichi Hanamoto, Kazutoshi Sato and Masaaki Okubo

Energies 2019, 12(19), 3800; https://doi.org/10.3390/en12193800 - 08 Oct 2019

Cited by 7 | Viewed by 2614

Abstract

An efficient NO_x reduction aftertreatment technology for a marine diesel engine that combines nonthermal plasma (NTP) and NO_x adsorption/desorption is investigated. The aftertreatment technology can also treat particulate matter using a diesel particulate filter and regenerate it via NTP-induced ozone. In [...] Read more.

An efficient NO_x reduction aftertreatment technology for a marine diesel engine that combines nonthermal plasma (NTP) and NO_x adsorption/desorption is investigated. The aftertreatment technology can also treat particulate matter using a diesel particulate filter and regenerate it via NTP-induced ozone. In this study, the NO_x reduction energy efficiency is investigated. The investigated marine diesel engine generates 1 MW of output power at 100% engine load. NO_x reduction is performed by repeating adsorption/desorption processes with NO_x adsorbents and NO_x reduction using NTP. Considering practical use, experiments are performed for a larger number of cycles compared with our previous study; the amount of adsorbent used is 80 kg. The relationship between the mass of desorbed NO_x and the energy efficiency of NO_x reduction via NTP is established. This aftertreatment has a high reduction efficiency of 71% via NTP and a high energy efficiency of 115 g(NO₂)/kWh for a discharge power of 12.0 kW. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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9 pages, 2398 KiB

Open AccessArticle

Collection Characteristic of Nanoparticles Emitted from a Diesel Engine with Residual Fuel Oil and Light Fuel Oil in an Electrostatic Precipitator

by Akinori Zukeran, Hidetoshi Sawano and Koji Yasumoto

Energies 2019, 12(17), 3321; https://doi.org/10.3390/en12173321 - 28 Aug 2019

Cited by 7 | Viewed by 2229

Abstract

The purpose of this study was to investigate the collection characteristics of nanoparticles emitted from a diesel engine in an electrostatic precipitator (ESP). The experimental system consisted of a diesel engine (400 cc) and an ESP; residual fuel oil and light fuel oil [...] Read more.

The purpose of this study was to investigate the collection characteristics of nanoparticles emitted from a diesel engine in an electrostatic precipitator (ESP). The experimental system consisted of a diesel engine (400 cc) and an ESP; residual fuel oil and light fuel oil were used for the engine. Although, the peak value of distribution decreased as the applied voltage increased due to the electrostatic precipitation effect, the particle concentration, at a size of approximately 20 nm, increased compared with that at 0 kV, in the exhaust gas, from the diesel engine with residual fuel oil. However, the efficiency increased by optimizing the applied voltage, and the total collection efficiency in the exhaust gas, using the residual fuel oil, was 91%. On the other hand, the particle concentration, for particle diameters smaller than 20 nm, did not increase in the exhaust gas from the engine with light fuel oil. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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14 pages, 4991 KiB

Open AccessArticle

Fundamental Evaluation of Thermal Switch Based on Ionic Wind

by Keiichiro Yoshida

Energies 2019, 12(15), 2963; https://doi.org/10.3390/en12152963 - 01 Aug 2019

Cited by 2 | Viewed by 2344

Abstract

A significant amount of thermal energy (mainly under 200 °C) is wasted in the world. To utilize the waste heat, efficient heat management and thermal switching is required. The basic characteristics of a thermal switch that controls the flow of heat by switching [...] Read more.

A significant amount of thermal energy (mainly under 200 °C) is wasted in the world. To utilize the waste heat, efficient heat management and thermal switching is required. The basic characteristics of a thermal switch that controls the flow of heat by switching on/off the ionic wind is discussed in this study. The study was conducted through experiments and numerical simulations. A heater made of aluminum block maintained at 100 °C was used as a heat source, and the rate of heat flow to a copper plate placed over it was measured. Ionic wind was induced by corona discharge with a needle placed on the heater. The ratio of heat transfer coefficients was obtained in the range of 3–4, with an energy efficiency of around 10. The heat flux at this condition was approximately 400 W/m². The numerical simulations indicate that the heat transfer is enhanced by ionic winds, and the results were found to corroborate well with the experimental ones. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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11 pages, 4455 KiB

Open AccessArticle

Development of an Electrostatic Precipitator with Porous Carbon Electrodes to Collect Carbon Particles

by Yoshihiro Kawada and Hirotaka Shimizu

Energies 2019, 12(14), 2805; https://doi.org/10.3390/en12142805 - 21 Jul 2019

Cited by 4 | Viewed by 3265

Abstract

Exhaust gases from internal combustion engines contain fine carbon particles. If a biofuel is used as the engine fuel for low-carbon emission, the exhaust gas still contains numerous carbon particles. For example, the ceramic filters currently used in automobiles with diesel engines trap [...] Read more.

Exhaust gases from internal combustion engines contain fine carbon particles. If a biofuel is used as the engine fuel for low-carbon emission, the exhaust gas still contains numerous carbon particles. For example, the ceramic filters currently used in automobiles with diesel engines trap these carbon particles, which are then burned during the filter regeneration process, thus releasing additional CO₂. Electrostatic precipitators are generally suitable to achieve low particle concentrations and large treatment quantities. However, low-resistivity particles, such as carbon particles, cause re-entrainment phenomena in electrostatic precipitators. In this study, we develop an electrostatic precipitator to collect fine carbon particles. Woodceramics were used for the grounded electrode in the precipitator to collect carbon particles on the carbon electrode. Woodceramics are eco-friendly materials, made from sawdust. The electrical resistivity and surface roughness of the woodceramics are varied by the firing temperature in the production process. Woodceramics electrodes feature higher resistivity and roughness as compared to stainless-steel electrodes. We evaluated the influence of woodceramics electrodes on the electric field formed by electrostatic precipitators and calculated the corresponding charge distribution. Furthermore, the particle-collection efficiency of the developed system was evaluated using an experimental apparatus. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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14 pages, 5645 KiB

Open AccessFeature PaperArticle

Plasma–Chemical Hybrid NO_x Removal in Flue Gas from Semiconductor Manufacturing Industries Using a Blade-Dielectric Barrier-Type Plasma Reactor

by Haruhiko Yamasaki, Yuki Koizumi, Tomoyuki Kuroki and Masaaki Okubo

Energies 2019, 12(14), 2717; https://doi.org/10.3390/en12142717 - 16 Jul 2019

Cited by 36 | Viewed by 3451

Abstract

NO_x is emitted in the flue gas from semiconductor manufacturing plants as a byproduct of combustion for abatement of perfluorinated compounds. In order to treat NO_x emission, a combined process consisting of a dry plasma process using nonthermal plasma and a [...] Read more.

NO_x is emitted in the flue gas from semiconductor manufacturing plants as a byproduct of combustion for abatement of perfluorinated compounds. In order to treat NO_x emission, a combined process consisting of a dry plasma process using nonthermal plasma and a wet chemical process using a wet scrubber is performed. For the dry plasma process, a dielectric barrier discharge plasma is applied using a blade-barrier electrode. Two oxidation methods, direct and indirect, are compared in terms of NO oxidation efficiency. For the wet chemical process, sodium sulfide (Na₂S) is used as a reducing agent for the NO₂. Experiments are conducted by varying the gas flow rate and input power to the plasma reactor, using NO diluted in air to a level of 300 ppm to simulate exhaust gas from semiconductor manufacturing. At flow rates of ≤5 L/min, the indirect oxidation method verified greater removal efficiency than the direct oxidation method, achieving a maximum NO conversion rate of 98% and a NO_x removal rate of 83% at 29.4 kV and a flow rate of 3 L/min. These results demonstrate that the proposed combined process consisting of a dry plasma process and wet chemical process is promising for treating NO_x emissions from the semiconductor manufacturing industry. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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13 pages, 2132 KiB

Open AccessArticle

Gasification of Waste Cooking Oil to Syngas by Thermal Arc Plasma

by Andrius Tamošiūnas, Dovilė Gimžauskaitė, Mindaugas Aikas, Rolandas Uscila, Marius Praspaliauskas and Justas Eimontas

Energies 2019, 12(13), 2612; https://doi.org/10.3390/en12132612 - 07 Jul 2019

Cited by 20 | Viewed by 4483

Abstract

The depletion and usage of fossil fuels causes environmental issues and alternative fuels and technologies are urgently required. Therefore, thermal arc water vapor plasma for a fast and robust waste/biomass treatment is an alternative to the syngas method. Waste cooking oil (WCO) can [...] Read more.

The depletion and usage of fossil fuels causes environmental issues and alternative fuels and technologies are urgently required. Therefore, thermal arc water vapor plasma for a fast and robust waste/biomass treatment is an alternative to the syngas method. Waste cooking oil (WCO) can be used as an alternative potential feedstock for syngas production. The goal of this experimental study was to conduct experiments gasifying waste cooking oil to syngas. The WCO was characterized in order to examine its properties and composition in the conversion process. The WCO gasification system was quantified in terms of the produced gas concentration, the H₂/CO ratio, the lower heating value (LHV), the carbon conversion efficiency (CCE), the energy conversion efficiency (ECE), the specific energy requirements (SER), and the tar content in the syngas. The best gasification process efficiency was obtained at the gasifying agent-to-feedstock (S/WCO) ratio of 2.33. At this ratio, the highest concentration of hydrogen and carbon monoxide, the H₂/CO ratio, the LHV, the CCE, the ECE, the SER, and the tar content were 47.9%, 22.42%, 2.14, 12.7 MJ/Nm³, 41.3% 85.42%, 196.2 kJ/mol (or 1.8 kWh/kg), and 0.18 g/Nm³, respectively. As a general conclusion, it can be stated that the thermal arc-plasma method used in this study can be effectively used for waste cooking oil gasification to high quality syngas with a rather low content of tars. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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12 pages, 3585 KiB

Open AccessArticle

Control Strategy for Power Conversion Systems in Plasma Generators with High Power Quality and Efficiency Considering Entire Load Conditions

by Hyo Min Ahn, Eunsu Jang, Seung-Hee Ryu, Chang Seob Lim and Byoung Kuk Lee

Energies 2019, 12(9), 1723; https://doi.org/10.3390/en12091723 - 07 May 2019

Cited by 3 | Viewed by 2732

Abstract

In this paper, a control method for the power conversion system (PCS) of plasma generators connected with a plasma chamber has been presented. The PCS generates the plasma by applying a high magnitude and high frequency voltage to the injected gasses, in the [...] Read more.

In this paper, a control method for the power conversion system (PCS) of plasma generators connected with a plasma chamber has been presented. The PCS generates the plasma by applying a high magnitude and high frequency voltage to the injected gasses, in the chamber. With regards to the PCS, the injected gases in the chamber could be equivalent to the resistive impedance, and the equivalent impedance had a wide variable range, according to the gas pressure, amount of injected gases and the ignition state of gases in the chamber. In other words, the PCS for plasma generators should operate over a wide load range. Therefore, a control method of the PCS for plasma generators, has been proposed, to ensure stable and efficient operation in a wide load range. In addition, the validity of the proposed control method was verified by simulation and experimental results, based on an actual plasma chamber. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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16 pages, 7337 KiB

Open AccessArticle

Experimental and Numerical Investigations of Plasma Ignition Characteristics in Gas Turbine Combustors

by Shizheng Liu, Ningbo Zhao, Jianguo Zhang, Jialong Yang, Zhiming Li and Hongtao Zheng

Energies 2019, 12(8), 1511; https://doi.org/10.3390/en12081511 - 22 Apr 2019

Cited by 9 | Viewed by 4031

Abstract

Reliable ignition is critical for improving the operating performance of modern combustor and gas turbines. As an alternative to the traditional spark discharge ignition, plasma assisted ignition has attracted more interest and been shown to be more effective in increasing ignition probability, accelerating [...] Read more.

Reliable ignition is critical for improving the operating performance of modern combustor and gas turbines. As an alternative to the traditional spark discharge ignition, plasma assisted ignition has attracted more interest and been shown to be more effective in increasing ignition probability, accelerating kernel growth, and decreasing ignition delay time. In this paper, the operating characteristic of a typical self-designed plasma ignition system is investigated. Based on the optical experiment, the plasma jet flow feature during discharge is analyzed. Then, a detailed numerical study is carried out to investigate the effects of different plasma parameters on ignition enhancement of a one can-annular combustor used in gas turbines. The results show that plasma indeed has a good ability to expand the ignition limit and decrease the minimum ignition energy. For the studied plasma ignitor, the initial discharge kernel is not a sphere but a jet flow cone with a length of about 30 mm. Besides, the numerical comparisons indicate that the additions of plasma active species and the increases of initial energy, plasma jet flow length and discharge frequency can benefit the acceleration of kernel growth and flame propagation via thermal, kinetic and transport pathways. The present study may provide a suitable understanding of plasma assisted ignition in gas turbines and a meaningful reference to develop high performance ignition systems. Full article

(This article belongs to the Special Issue Plasma Processes for Renewable Energy Technologies)

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