Wireless sensor node powered by aircraft specific thermoelectric energy harvesting

An energy autonomous wireless sensor system consisting of an energy harvesting power source, an energy management unit and a low power wireless sensor node is tested for aircraft applications. The autonomous power source combines aircraft specific outside temperature changes with a thermoelectric generator (TEG) and a heat storage unit. The temperature difference generated with the latter component artificially at the TEG is used to power the sensor node by thermoelectricity. Additionally, a high efficient low input voltage power management circuit is necessary to store the generated energy and to convert it to higher voltage levels needed to operate the sensor. The experimental data are compared with results from numerical simulation models to predict the energy conversion in the heat storage - TEG system. A new TEG prototype is tested and the energy output is improved by 14%. The power management storage capacitors are adapted to the available energy, thereby increasing storage voltage and conversion efficiency. Doing so, the efficiency of the complete system can be increased by around 50%.     

Temperature sensor using ferrofluid thin film

A brand new design of temperature sensor using ferrofluid thin film is proposed in this paper. When magnetic field parallel to the plane of the ferrofluid thin film is applied, magnetic chains form in the same direction of the magnetic field, which results in the suppressing of optical transmission. It is observed that the optical transmission is changed by the ambient temperature, so that temperature sensor can be constructed by measuring the transmission power of a laser. The physics and the sensitivity of the temperature sensor are also analyzed.     

A minimal mass deployable structure for solar energy harvesting on water canals

This paper produces a design for a minimal mass, deployable support structure for a solar panel covering of water canals. The results are based upon the minimal mass properties of tensegrity structures. The efficient structure is a tensegrity system which has an optimal complexity (i.e. an optimal number of members) for minimal mass. This optimal complexity is derived in this paper, along with deployable schemes which are useful for construction, repairs, for Sun following, and for servicing. It is shown that the minimal structure naturally has deployable features so that extra mass is not needed to add the multifunctional features. The design of bridge structures with tensegrity architecture will show an optimal complexity depending only on material choices and external loads. The minimization problem considers a distributed load (from weight of solar panels and wind loads), subject to buckling and yielding constraints. The result is shown to be a Class 1 Tensegrity substructure (support structure only below the deck). These structures, composed of axially-loaded members (tension and compressive elements), can be easily deployable and have many port-able applications for small spans. The focus of this paper is an application of these minimal mass tensegrity concepts to design shading devices to prevent or reduce evaporation loss, while generating electric power with solar panels as the cover. While the economics of the proposed designs are far from finalized, this paper shows a technical solution that uses the smallest material resources, and shows the technical feasibility of the concept.     

大挠度压电聚合物薄膜的能量收集研究

为了给微型传感器持续稳定地供电,利用聚偏二氟乙烯(PVDF)薄膜受外部激励产生大挠度变形来产生更多的电能.通过使不同长度的PVDF薄膜产生不同程度的位移,来探究PVDF薄膜变形与发电量的关系.有限元分析结果表明:在同一长度的PVDF薄膜中,发电量随位移的增大而增大.分别将长度为4.1,7.3,17.1 cm的PVDF薄...     

Topology optimization of energy harvesting devices using piezoelectric materials

Energy harvesting devices based on the piezoelectric effect that converts ambient energy to electric energy is a very attractive energy source for remote sensors and embedded devices. Although topology optimization has been applied to the design of piezoelectric transducers, the locations of piezoelectric materials are predefined and only the optimal layout of elastic materials is considered. In this paper, both elastic materials as well as piezoelectric materials are considered for the design of energy harvesting devices under the topology optimization formulation. The objective function for this study is to maximize the energy conversion factor. The sensitivities of both stored strain energy and electrical energy are derived by the adjoint method. Examples of energy harvesting devices are presented and discussed using the proposed method.     

Optimal shape for optical absorption in organic thin film solar cells

The power conversion efficiency of organic solar cells can be increased by using light trapping geometries, which enhance the light absorption. In this paper, we analyze the optical performance of organic thin film solar cells using the finite element method solving the Maxwell equations. Shape optimization is then performed with the goal of maximizing the light absorption in the active layer, while keeping its thickness low. The optimization algorithm is based on the gradient of the objective function, where sensitivity is obtained from the adjoint approach. To avoid irregular shapes in the optimized structures, two different shape representation techniques, finite element node based curve representation in conjunction with the Helmholtz filter and B-spline curve representation with varying number of control points are used. Both are demonstrated being effective in smoothing the design shapes. Periodic grating structures are observed in the optimized shapes and significant increase in light absorption is achieved in the active layer with low thickness.     

Ultrathin dual‐layer triple‐band flexible microwave metamaterial absorber for energy harvesting applications

An ultrathin dual‐layer flexible metamaterial absorber with triple‐band for RF energy harvesting applications has been reported in this article. The sub‐wavelength unit cell of the proposed absorber is composed of six distinct concentric annular having outer circumference of ring and octagonal inner circumference. The metallic resonators are constructed from copper foil self‐adhesive tape which are affixed on flexible neoprene rubber sheet terminated by metal ground plate. The proposed absorber prototype is ultrathin and compact with the thickness less than 0.037λ₀ and cell size less than 0.2λ₀ at the lower absorption frequency of 1.75 GHz. Flexible dual‐layer absorber exhibits triple absorption peaks of 96.91%, 96.41% and 90.12% at 1.75 GHz, 2.17 GHz and 2.6 GHz with full width at half maximum (FWHM) bandwidth of about ~6.5%. The RF performance of proposed absorber is numerically computed for different polarization and incidence angle variations. The absorption value is above 76% for the oblique incidence angle up to 45° in TE mode operation, whereas the absorption value is 94% for oblique incidence angle up to 60° in TM mode operation. The measured outcomes are in agreement with the numerically calculated results. The energy harvesting potential of the proposed absorber structure is numerically confirmed by the resulting improved RF absorption value in dependence to different resistive loading of the polarization insensitive unit cells.     

Ethanol sensing using CuO/MWNT thin film

Copper (II) oxide (CuO)/multiwall carbon nanotube (MWNT) thin film based ethanol-sensors were fabricated by dispersing CVD-prepared MWNTs in varying concentration over DC magnetron sputtered-CuO films. The responses of these sensors as a function of MWNT concentrations and temperatures were measured, and compared. The sensing response was the maximum at an operating temperature near 400 °C for all the samples irrespective of the MWNTs dispersed over them. At optimum operating temperature (T_opt) of 407 ± 1 °C, the response is linear for 100-700 ppm range and tends to saturate at higher concentrations. In comparison with bare CuO sample, the response of CuO/MWNT sensing films increased up to 50% in the linear range. The response improvement for 2500 ppm of ethanol was up to 90% compared to bare CuO sample. In addition, the sensing response time also reduced to around 23% for lowest ethanol concentration at T_opt. However, a decrease in the sensor response was observed on films with very high concentrations of MWNTs.     

CIGS太阳能电池中薄膜材料电阻率的研究

研究了减小CIGS太阳能电池中Mo,CIGS,n-ZnO三层薄膜电阻率的溅射工艺方法,以达到减小电池串联电阻的目的.改变工艺参数制备不同样品并对其进行测试分析,得到了溅射气压、村底温度、退火工艺对电阻率和薄膜微观形貌的影响.证明了采用双层溅射法制备的Mo、低气压、衬底加热、溅射后退火得到的CIGS以及3～5 Pa下制备...     

Magnetron sputtering of piezoelectric AlN and AlScN thin films and their use in energy harvesting applications

This paper reports on the deposition of AlN and Al_XSc_1?XN films by pulse magnetron sputtering. The first part will focus on the Al_XSc_1?XN deposition process in comparison to the already established AlN process. The effect of doping AlN with Sc regarding piezoelectric and mechanical properties is presented. The films show the expected increase of piezoelectric properties as well as the softening of the material with higher Sc concentrations. Above a threshold concentration of around 40 % Sc in the Al_XSc_1?XN films, there exists a separation into two phases, an Al-rich and a Sc-rich wurtzite phase, which is shown by XRD. At Sc concentrations higher than 50 %, the films are not piezoelectric, as the films are composed primarily of the cubic ScN phase. The second main part of this paper evaluates the films for application in energy harvesting. Especially the Sc doping allows a significant increase in the energy generated in our test setup. Directly measuring the AC voltage at resonance depending on load resistance with base excitation of ±2.5 µm, 350 µW power have been generated under optimum conditions compared to 70 µW for pure AlN. For a more application oriented measuring setup, a standard and a SSHI-based (“Synchronised Switch Harvesting on Inductor”) AC/DC converter circuit have been tested. The SSHI interface showed a significant improvement to 180 % compared to the standard interface.     

Application of an expert knowledge-based system to the semiconductor thin film device coating process

This paper briefly describes an expert knowledge-based system which assists and diagnoses in the thin film device coating process. The system gains knowledge from qualitative and experience judgement of the operation in supervisory work and self experience. An explanation is given of the expert knowledge-based system and an example is given of the user interface. Various problems in the production process itself which experts in the laboratory find difficult to solve are indicated. A knowledge-based representation scheme involving rules is presented as well. The system currently under development would be a flexible time-saving and practical decision support system.     

Plasma display panel MgO thin film properties and their modification by low energy ion bombardment

This paper contributes to a phenomenological understanding of the low energy ion bombardment induced changes of MgO thin films inside plasma display panels. SEM (scanning electron microscope) and optical photography are utilized to delineate local MgO changes such as densification and stress reversal at the operated gas panel cell site. MgO surface transformation is shown to be influenced by the presence of contaminants, surface topography, ion current and panel operating time. The implications of some of these with respect to panel operation are discussed. MgO thin film growth behaviour using electron-beam deposition and MgO film properties are dealt with in order to understand better the observed surface changes.     

表面等离子共振Ag-SnO_2薄膜光化学气体传感器

提出一种新型的Ag-SnO2复合膜H2S光化学表面等离子共振(SPR)气体传感器结构。结构中使用一只金红石材料作成的棱镜作为耦合棱镜,在棱镜的底边采用射频溅射技术制作Ag-SnO2复合膜(CuO为掺杂质),Ag膜和SnO2膜的厚度分别为50 nm和100 nm,在复合膜上设置待测气体的样品池。在白光入射激励下,复合膜的分界面发生SPR现象。实验结果表明:SPR的波长与H2S气体的体积分数基本呈线性关系。     

Application of ultra wideband RF energy harvesting by using multisection Wilkinson power combiner

In this study, an ultra‐wide band (UWB) energy harvesting circuit was proposed using the Greinacher rectifier circuit. The circuit was designed with Wilkinson power combiner (WPC) for use at two different radio frequency signal inputs. To enable broadband operation, the multisection Chebyshev impedance matching technique was applied in the branches of the WPC circuit. The center frequency was selected 2.2 GHz in the design. In terms of the parameters of reflection, transmission and isolation, the WPC circuit operates in the 0.4 GHz‐3.4 GHz range and the percentage bandwidth has been calculated as 136%. In the designed Greinacher rectifier circuit, power conversion efficiency (PCE) was analyzed for different input powers. When load resistor selected as R = 1500 Ω, the PCE for the input power of 9 dBm was about 70%. The proposed circuit, where WPC and Greinacher rectifier circuits was used together for energy harvesting; was operated in the frequency ranges BW₁ = 0.4‐0.81 GHz, BW₂ = 1.54‐1.84 GHz, and BW₃ = 2.2 GHz‐2.89 GHz. As a power combining application, dual power inputs were applied to the WPC circuit with frequencies of 540 MHz‐1800 MHz, 540 MHz‐2450 MHz, 540 MHz‐2700 MHz, 800 MHz‐1800 MHz, 800 MHz‐2450 MHz and 800 MHz‐2700 MHz. Eventually, approximately 70.5% PCE and 1.65 V output voltage were obtained.     

Characterisation of PZT thin film micro-actuators using a silicon micro-force sensor

This paper reports on the measurements of displacement and blocking force of piezoelectric micro-cantilevers. The free displacement was studied using a surface profiler and a laser vibrometer. The experimental data were compared with an analytical model which showed that the PZT thin film has a Young's modulus of 110 GPa and a piezoelectric coefficient d_31,f of 30 pC/N. The blocking force was investigated by means of a micro-machined silicon force sensor based on the silicon piezoresistive effect. The generated force was detected by measuring a change in voltage within a piezoresistors bridge. The sensor was calibrated using a commercial nano-indenter as a force and displacement standard. Application of the method showed that a 700 μm long micro-cantilever showed a maximum displacement of 800 nm and a blocking force of 0.1 mN at an actuation voltage of 5 V, within experimental error of the theoretical predictions based on the known piezoelectric and elastic properties of the PZT film.     

CAD of a low-temperature solar energy collector using interactive programming

This paper describes a pilot interactive computer program used by midshipmen in the early phases of design of a low-temperature solar energy collector. The model has been made as simple as possible without losing the fundamental relationships of thermodynamics, fluid dynamics and heat transfer theory. The subjects covered include solar radiation, flat plate collectors, application loads and economics. Design parameters are location, time duration, absorptivity, reflectivity, tilt angle, number of cover glasses, collector temperature, air temperature, insulation condition, etc. The program provides enough information to allow users to evaluate and design their own solar thermal processes.     

Modeling the front side plasmonics effect in nanotextured silicon surface for thin film solar cells application

We report the computational modeling of the front side plasmonics effect arising on gold (Au) nanoparticles array in combination with nanotextured silicon surface for thin film silicon solar cells application. The ultimate efficiency of the optimized silicon nanoholes (SiNH) array textured surface using Au plasmonics effect is 38.58 %, which is 24.01 % greater than SiNH array textured surface without Au plasmonics effect. Furthermore, SiNH array textured surface perform better compared to silicon nanopillar (SiNP) array textured surface for all the parameters studied. The maximum possible short circuit current density and power conversion efficiency of the proposed SiNH array textured surface with Au plasmonics effect are 31.57 mA/cm² and 25.45 % respectively, which compares favorably well to the computed values of 26.17 mA/cm² and 21.12 %, respectively for the SiNP array textured surface with Au plasmonics effect.     

A unified approach of energy and data cooperation in energy harvesting WSNs

Energy harvesting (EH) provisioned wireless sensor nodes are key enablers to increase network life time in modern wireless sensor networks (WSNs). However, the intermittent nature of the EH process necessitates management of nodes’ limited data and energy buffer capacity. In this paper, a unified mathematical model for a cooperative EHWSN with an opportunistic relay is presented. The energy and data causality constraints are expressed in terms of throughput, available energy, delay and transmission time. Considering finite energy buffers, data buffers and discrete transmission rates (as defined in the standard IEEE 802.15.4) at the nodes, different intuitive online power allocation policies at the relay are studied. The results show that a policy achieving high throughput is less fair and vice versa. Therefore, a joint rate and power allocation policy (JRPAP) is proposed in this study which provides a better trade off between fairness, throughput and energy over intuitive policies. Based on the JRPAP results, we propose to use data aggregation (DA) to achieve throughput gain at lower buffer sizes. In addition, the notion of energy aggregation (EA) is introduced to achieve throughput gain at higher buffer sizes. Combining both EA and DA further improves the overall throughput at all buffer sizes.     

超声液体环境下压电式振动能量采集的研究

针对在液体环境下工作的器件不利于直接供能这一难题,制作了一种可在液体环境下工作的振动能量采集器,采用压电悬臂梁结构在液体环境中采集水中的超声能量,在32 kHz超声频率激励下,最高获得了5.04V的输出电压.通过改变超声波与悬臂梁的相对方向及液体盐分质量分数,发现能量采集器在超声液体环境下工作的发电效率随盐分质量分数的...