Hybrid Insulation Research Articles

Flexible and high noise margin organic enhancement inverter using hybrid insulator

We demonstrate a high noise margin and highly flexible enhancement inverter based on the organic-inorganic hybrid insulator. Organic insulators generally show high leakage current and inorganic insulators are brittle. In this work, hybrid insulator was used in pentacene-based organic thin film transistors (OTFTs) to overcome the limitations of each single type of insulator. We report highly flexible OTFTs with reduced threshold voltage and negligible hysteresis using a poly(methyl methacrylate)/silicon nitride hybrid insulator. Using the optimized hybrid insulator, we also demonstrate an enhancement inverter which shows high noise margin with noise margin low of 2.2V, a noise margin high of 14.1V and gain of 2.1.

A Case Study on Insulating Main Steam Line (MSL) with Silica Aerogel

In this paper, a case study on replacing the existing insulating material (Mineral wool) by the Silica Aerogel in the main steam line (MSL) of the thermal power plant is presented.A sample length of 3 m in MSL was insulated with various thicknesses of silica aerogel, mineral wool and the combinations of mineral wool and silica aerogel. The heat loss in the sample length with different insulating material was calculated by carrying out field experiments. The results show that the silica aerogel is providing better insulation than the mineral wool. Nonetheless, the use of silica aerogel is expensive. To bring down the cost, hybrid insulation with the optimal thickness of silica aerogel + mineral wool + silica aerogel was suggested. This hybrid combination considerably reduced the heat loss and improved the thermal efficiency. The payback period for this implementation was reported.

Use of a hot-box facility to evaluate hybrid reflective insulation assemblies

The determination of the thermal performance of hybrid insulation assemblies that include an enclosed reflective airspace and a separate layer of insulation is being done using a hot-box test facility operated in accordance with ASTM C1224, the Standard Specification for Reflective Insulation. The thermal resistance determination of the insulated region requires a hot-box test with known thermal insulation to determine heat flow through the framing. Factors that affect the result for the hybrid insulation assembly will be discussed along with results obtained using the ASTM C1224 protocol. The thermal resistance obtained using the hot-box apparatus will be compared with calculated values obtained from published correlations. The uncertainty in the hybrid insulation assembly and the enclosed reflective airspace due to uncertainty in the thermal resistance of the calibration material are of particular interest.

Hybrid and Reflective Insulation Assemblies for Buildings

Materials with a low thermal emittance surface have been used for many years to create reflective insulations that reduce the rate of heat flow across building envelopes. Reflective insulation technology is now being combined with other energy conserving technologies to optimize overall thermal performance. The basis for the performance of reflective insulations and radiant barriers will be discussed along with the combination of these materials with cellular plastic or mineral fiber insulations to form hybrid insulation assemblies. Calculations of thermal resistance for enclosed reflective air spaces and current field data from Southeast Asia will be presented. These data show that reductions in heat transfer across the building enclosure can be effectively reduced by the use of enclosed reflective air spaces and attic radiant barriers. Reflective technology increases the overall thermal resistance of the building enclosure when used to insulate poured concrete structures.

Applications of Low-Emissivity Hybrid Insulation in South Korea

Applications of Low-Emissivity Hybrid Insulation in South Korea

Applications of Low-Emissivity Hybrid Insulation in South Korea

Low-Emissivity Hybrid Insulation has been developed in South Korea. It combines both resistive and reflective insulating principle. It is composed with many layers of reflective aluminum foils and honeycomb-structure air cells with polyethylene foam. This paper introduces recent South Korean building insulation code and the applications of Low-Emissivity Hybrid Insulation to meet the code.

Assessing the Thermal Performance of District Heating Twin Pipes with Vacuum Insulation Panels

In Sweden, around 10% of the energy supplied to the district heating networks are lost through heat losses from the distribution pipes. In cylindrical geometries it is preferable to improve the insulation as close to the center as possible. This has resulted in a hybrid insulation district heating pipe concept with a combination of vacuum insulation panels at the center, held in place by polyurethane foam. In the twin pipe concept, the vacuum insulation panel cover the supply pipe. This creates a complex temperature profile over the section and measured results on single pipes might not be applicable. Therefore, there is a need for a method to evaluate the improvement of hybrid insulation twin pipes in the laboratory. This paper presents a method where two guarded hot pipe apparatuses is used, one heating rod for each pipe, to measure the heat losses from hybrid pipes and compare to a conventional polyurethane pipe. The measurements indicate an improvement in thermal performance by 12%-18% for the total losses and by 29% -39% for the supply pipe losses.

Impact of local overheating on conventional and hybrid insulations for power transformers

For more than a century, conventional mineral oil/cellulose insulation is being used as main insulation for power transformers. The life span of these major assets is determined amongst others by the insulation system’s mechanical resistance to withstand short circuit current forces. Since cellulose paper aging is accelerated by temperature, moisture and oxygen, poly-aramid-based synthetic insulation paper, with better thermal stability emerged for application in transformers. However the relatively limited number of studies on hybrid insulation and the cost of aramid paper still limit their use in distribution transformers. This contribution attempts to demonstrate that despite the high cost of aramid paper, hybrid insulation could be used in large power transformers which represent a significant financial investment. To do this, the quality of mineral oil aged with hybrid solid insulation and the thermal aging of the cellulose paper of this insulation are investigated. Comparison was made with traditional mineral oil impregnated cellulose paper to provide a benchmark for comparison. The samples underwent thermal accelerated aging procedure according to ASTM-D1934 standard and, furthermore, were submitted to local overheating. The condition of oil samples collected from each aging vessel was assessed using several diagnostic techniques, namely the relative amount of the Dissolved Decay Products (DDP), Turbidity, and Interfacial Tension (IFT). The Degree of Polymerisation (DPv) and Dissolved gas Analysis (DGA) were used to monitor the thermal aging of the cellulose paper samples. The results indicate that oil aged with hybrid solid insulation yield fewer decay products at some aging stages, especially after the application of a local overheating. The results also indicate that the cellulose paper within solid hybrid insulation is slightly less degraded compared to that of conventional insulation.

Field measurements on a district heating pipe with vacuum insulation panels

In Swedish district heating networks, around 10% of the supplied thermal energy is lost in the distribution system. One solution to decrease the losses is to use hybrid insulation district heating pipes, a concept where the innermost part of the thermal insulation consists of vacuum insulation panels, held in place by polyurethane foam. One problem with vacuum insulation panels are their sensitivity to high temperatures. This paper presents field measurements on a hybrid insulation district heating pipe where the temperatures have been measured continuously at various positions of a pipe section. The measurements show consistency and a large difference between hybrid insulation parts and reference parts without vacuum insulation panels. A superposition model has been used to calculate the temperature in a point and compare it to the measurement. The results are compared to the same calculation on the results from finite element simulations. The results show clearly that the vacuum panels in the pipes have not collapsed. A slow deterioration of the panels is harder to find with this model. Changes in the system, such as a return temperature which decreases over time, can give a larger impact, concealing the change in the panel performance.

Lightning Impulse Breakdown Characteristic of Dry-Air/Silicone Rubber Hybrid Insulation in Rod-Plane Electrode

Sulfur hexafluoride (SF6) gas is used widely in electric power equipment such as Gas Insulated Switchgear (GIS), Gas Insulation transmission Line (GIL), and Gas Circuit Breaker (GCB). But applications of SF6 should be restricted because SF6 gas is one of the greenhouse effect gases. To reduce use of SF6 gas, a study on eco-friendly alternative insulation medium is needed. In this paper, we investigated lightning impulse (LI) breakdown of dry-air which is attracting attention as an ecofriendly alternative gas and the LI breakdown of hybrid insulation combined with dry-air and solid insulation (Room-Temperature Vulcanizing Silicone Rubber-RTV SIR) and dry-air in inhomogeneous fields according to gap distance and pressure. The experiment results showed that the LI breakdown strength of hybrid insulation system was higher than that of dry-air insulation system. It was verified that the development of technology related to eco-friendly power apparatus compact such GIS, GCB and GIL can be used as basic research data.

Enameled Wire Having Polyimide-silica Hybrid Insulation Layer Prepared by Sol-gel Process

Enameled Wire Having Polyimide-silica Hybrid Insulation Layer Prepared by Sol-gel Process

Discharge Inception Points of Hybrid Insulation System with SF6 Gas and Solid Insulator

Discharge Inception Points of Hybrid Insulation System with SF₆ Gas and Solid Insulator

Analysis and Optimum Design of Hybrid Plasmonic Slab Waveguides

Propagation properties of hybrid plasmonic slab waveguides are studied in detail using transfer matrix method considering structural and material aspects. Hybrid metal–insulator, hybrid metal–insulator–metal, and hybrid insulator–metal–insulator waveguides are considered. Propagation length (Lp), spatial length (Ls), and mode length (Lm) are utilized as three common figures of merit to compare and optimize the waveguides according to the layer thicknesses and metal/dielectric materials. The effect of constituting materials including metals (such as silver, gold, copper, and aluminum) and dielectrics (common dielectric materials used in photonic integrated circuit technologies such as silicon and silicon compounds, III–V compounds, and polymers) are discussed. It is found that hybrid waveguides are partially to completely superior to conventional plasmonic waveguides, providing a better balance between confinement and loss.

Evaluation of Organic-Inorganic Hybrid Insulation Material Using Inorganic Filler and Polyurethane

Recently, inorganic-organic hybrid materials have attracted much attention not only for their excellent thermal conductivity but also for their flame retardant properties. In this study, the properties of organic-inorganic hybrid insulating materials using inorganic fillers and polyurethane foam with different foaming conditions have been investigated. The addition of 1.5 wt% water to polyurethane as foaming agent shows the best foaming properties. The pore size was decreased in the foaming body with increasing of the <TEX>$CaCO_3$</TEX> addition. The apparent density and thermal conductivity were increased by increasing the <TEX>$CaCO_3$</TEX> addition. With an increasing amount of <TEX>$CaCO_3$</TEX> powder, the flame retardant property is improved, but the properties of thermal conductivity and apparent density tend to decrease. When the addition of fine particles of <TEX>$CaCO_3$</TEX>, the apparent density and thermal conductivity were increased and, also, with the addition of coarse particles over <TEX>$45{\mu}m$</TEX> in size, the apparent density and thermal conductivity were increased as well. In this study, the adding of <TEX>$CaCO_3$</TEX> with average particle size of <TEX>$27{\mu}m$</TEX> led to the lowest thermal conductivity and apparent density. After evaluation with different inorganic fillers, <TEX>$Mg(OH)_2$</TEX> showed the highest thermal conductivity; on the other hand, <TEX>$CaCO_3$</TEX> showed the lowest thermal conductivity.

Fabrication of Organic Thin-Film Transistors Based on Cross-Linked Hybrid Dielectric Materials

We report here the synthesis and dielectric properties of cross-linked hybrid dielectrics for organic field-effect transistor application. Hybrid thin films were first fabricated by hydrolysis of methacrylate-modified titanium and zirconium alkoxides and were further cross-linked via polymerization under UV. The dielectrics exhibit high dielectric constants (5.2–9) and good insulating properties with low leakage current densities (10-6–10-7 A/cm2) even though the dielectric film thickness was about 25–150 nm. Furthermore, the hybrid thin films had smooth and hydrophobic surfaces. The fabricated pentacene field-effect transistors using these dielectrics show good electric performance, including a carrier mobility as large as 0.29 cm2 V-1 s-1, a subthreshold swing as low as 0.13 V/decade, an on/off current ratio of ∼105, and a low threshold voltage of 0.3 V with TiO2 hybrid dielectrics. Organic thin-film transistors (OTFTs) fabricated with ZrO2 hybrid insulators exhibit a carrier mobility of 0.21 cm2 V-1 s-1 with an Ion/Ioff ratio of ∼104, a threshold voltage of -0.83 V, and a subthreshold swing of 0.39 V/decade.

Design development and performance studies of a novel Single Family Solar Cooker

This paper presents the design development and, thermal and cooking performance studies of a novel solar cooker; it is named as Single Family Solar Cooker (SFSC). Small size, convenient design, inexpensive lightweight hybrid insulation and specially designed lightweight polymeric glaze are the main features of this cooker. A complete theoretical consideration for the fabrication of SFSC has been presented. The thermal profiles of various components of SFSC on different days under different conditions have been measured. During testing, the highest plate stagnation temperature, under no-load condition, approached 144 °C. The two figures of merits F1 and F2 are found to be 0.116 °C m2/W and 0.466, respectively, which are according to the Bureau of Indian Standards. The cooking power regression curve is fairly linear with the regression coefficient R2 = 0.948. Initial cooking power 103.5 W and the heat loss level 1.474 W/°C, place it in the region of small cooker with good insulation, as per International Standard. Cooking tests of several food items performed during 2009 confirm year round good performance of this cooker.

A study on hybrid insulation composition joint using gas and solid insulator for gas‐insulated power equipment

AbstractSF6 is used as the main insulation gas for gas‐insulated switchgear (GIS), but it has recently become a gas that must be restricted because of its greenhouse effects. To date, we have studied the insulation characteristics of compressed N2 and CO2 as possible alternatives for SF6. We have reported that N2 or CO2 must be pressurized to 2.0 MPa when it is used as a substitute for SF6 at 0.5 MPa. Therefore, we have proposed a hybrid installation composition that uses gas and solid insulators. Because the central conductor of GIS is covered by a solid insulator in this composition, a high‐pressure gas at 2.0 MPa is not needed. However, the joint of the solid insulator becomes a weak point for discharge development. In this paper, we describe an effective configuration for improvement of the withstand voltage based on experiments. The most effective connector was made of resin without an implant electrode and the most effective configuration was one without a solid–solid interface between the solid insulator of the central conductor and the resin connector. In this experiment, the improvement of breakdown electric field of the hybrid composition was 44% or more compared with the case of only gas insulation (conventional method). In addition, further improvement can be expected by optimizing the insulation creepage distance and configuration. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 11–20, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21107

Hybrid gate insulator for OTFT using dip-coating method

With metal alkoxide(Ti, Ta, Zr) and copolymer, hybrid insulator film between 10 nm and 100 nm was prepared by dip-coating method on Si substrate and showed better frequency performance in terms of dielectric characteristics than did the copolymer. Also, the dielectric constant of hybrid dielectrics became larger as the content of metal alkoxide increased. With very thin hybrid dielectrics, OTFT with pentacene as organic semi-conductor can be operated below 10 V. From the transfer characteristics, the mobility of OTFT performance and sub-threshold were 3.5 cm 2/V, 0.09 V/dec, respectively, and on/off current ratio was ∼2.9 × 10 7. Dipping process to make thin hybrid gate insulator has been confirmed to be easy and versatile.

Development of 72/84‐kV dry air‐insulated dead tank VCB

AbstractThis paper describes a newly developed 72/84‐kV dry air‐insulated dead tank vacuum circuit breaker (VCB). VCB technology, which is essential for SF6 gas‐free equipment, has made advances in the fields of high‐voltage, large current interruption and environment‐conscious design. Light weight, decreased size, and reduced operating energy have been achieved by the new design. From the viewpoint of insulation, the characteristics of dry air, hybrid insulation structure, and insulation strength in vacuum were considered. Various performance verification tests in accordance with standards have been carried out and the reliability of the equipment has been verified. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(1): 1–10, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21145

Investigation of the DC breakdown mechanism in elastic syntactic foams

Modern insulation systems have to become more compact, less massive and environmentally acceptable. Elastic syntactic foams represent a multifunctional, elastic and compressible hybrid insulation material with a low density and a strong adhesion to polymers and metals. This kind of 'elastic foam' consists of a silicone gel and polymeric microspheres in a range of several 10 μm used as filler, which are often additionally coated with CaCO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . Elastic syntactic foams are increasingly used for power transmission equipment and also dc applications e.g. in cable terminations. This paper deals with the breakdown mechanisms under short- and long-term dc stress. Therefore, electrical and optical investigations, as well as field simulations on this insulation material have been carried out. The results should serve as a basis to develop design criteria for such dc insulation systems. It is found that coating the spheres improves the dielectric strength of this insulation material. Variation of the filling degree also influences the electrical properties. The discharge process itself takes place in the silicone gel due to field displacements caused by the microspheres.