1,720,961 research outputs found
The effect of the type of illumination on the energy harvesting performance of solar cells
No full textThis paper presents the effect of the illumination type on the performance of photovoltaic energy harvesting for application in buildings. A range of different types of solar cells are available to suit differing illumination sources and intensities. Modules made from polycrystalline silicon, amorphous silicon and dye-sensitized TiO2 were investigated under illumination from incandescent, fluorescent, white light LED and RGB colour-controllable LED light sources in this paper. It is shown that it is important to select the solar cell to suit the type of light. In this paper, the maximum power points of four types of solar cell have been investigated under three different electrical light sources for various illumination levels allowing the selection of the optimum solar cell type for a given combination of electrical light source and a particular illumination level. An analysis of the effect of varying the spectral composition of the illumination is achieved by using a colour-controllable LED to provide the primary colours of white light. Generally, most power is harvested by solar cells under incandescent illumination sources followed by compact fluorescent (CFL) and then LED. The amorphous-Si solar cells tested show a similar power output under all three illumination sources, therefore a device using these should perform consistently under all lighting sources, whereas the poly-crystalline silicon solar cell tested shows a significant difference between incandescent and CFL/white light LED sources which could restrict operation to just incandescent lighting
Effects of the binder material on the mechanical properties of thick-film magnetostrictive materials
No full textThis paper presents research carried out at the University of Southampton into the development of a magnetostrictive thick-film material suitable for use with silicon micromachined devices. This form of magnetostrictive material has previously been deposited onto alumina substrates and this paper reports further work on migrating the technology onto silicon. The evaluation of two alternative glass frits for use as the binder within the thick film is reported. The correct choice of the binder material is important in a thick-film material because it is responsible for binding the active material within the thick film into a composite material and also adhering the film to the substrate. A series of tests have been applied to samples fabricated using various glass frits to assess their mechanical properties and suitability for the micro-actuator applications
Energy harvesting from solar cells under typical illumination conditions in buildings
No full textEnergy harvesting powered devices have the potential for widespread use in buildings. The most prevalent ambient energy source available in buildings is light, which is normally harvested using photovoltaic devices. The light to be harvested can be from both natural and artificial sources and a range of different types of solar cells are available to suit differing light sources and intensities, and as such must be selected to suit the type of light to be encountered. For use inside buildings it is desirable to choose a device which will operate efficiently under artificial lighting as many locations have limited or no natural light, however, the nature of artificial sources is changing over time from incandescent sources, through fluorescent lights, with LED lights currently attracting significant interest due to energy savings. This paper presents an investigation into the selection of solar cell type for a range of artificial lighting sources and illumination levels
Flexible Integration of Alternative Energy Sources for Autonomous Sensing
No full textRecent developments in energy harvesting and autonomous sensing mean that it is now possible to power sensors solely from energy harvested from the environment. Clearly this is dependent on sufficient environmental energy being present. The range of feasible environments for operation can be extended by combining multiple energy sources on a sensor node. The effective monitoring of their energy resources is also important to deliver sustained and effective operation. This paper outlines the issues concerned with combining and managing multiple energy sources on sensor nodes. This problem is approached from both a hardware and embedded software viewpoint. A complete system is described in which energy is harvested from both light and vibration, stored in a common energy store, and interrogated and managed by the node
Modular Plug-and-Play Power Resources for Energy-Aware Wireless Sensor Nodes
No full textWireless sensors are normally powered by non-rechargeable batteries, but these must be replaced when depleted. Recent developments in energy harvesting technology allow sensors to be powered by environmental energy where it is present, but the wide range of situations where sensors are deployed means that it is desirable for the energy components of a sensor node (i.e. batteries, supercapacitors, and power generation devices) to be selected and configured at the time of node deployment. Previous energy harvesting-powered systems have been designed for specific energy hardware and been difficult to adapt for different resources. Energy-awareness is useful for state-of-the-art network algorithms, but present systems do not provide a standardized or straightforward way for nodes to monitor and manage their energy hardware. The developments reported in this paper deliver a reconfigurable energy subsystem for wireless autonomous sensors. The new system permits energy modules to be selected and fitted to the sensor node in-situ, in a plug-and-play manner, without the need for reprogramming or the modification of hardware. The node can monitor and intelligently manage its energy resources and assess its overall energy status by analyzing its level of stored energy and rate of power generation. These activities are facilitated by a proposed common hardware interface (which allows multiple energy modules to be connected) and an electronic datasheet structure for the energy modules. The system has been verified through the development and testing of a prototype wireless sensor node which operates from a mix of energy sources
Fabrication techniques for manufacturing flexible coils on textiles for inductive power transfer
Full text linkThis paper presents a comprehensive evaluation of fabrication techniques for the integration of coils into textiles, for the purpose of enabling low power wireless power transfer; for example, the powering of on-body monitoring devices such as heart-rate monitors. Key electrical parameters of the coils required to maximize power transfer efficiency are identified from theory. Flexible coils have been fabricated using standard processes widely used in the textile industry, such as screen printing and embroidery. The screen printed coils were fabricated with a silver-polymer ink on a printed interface layer, the embroidered coils were fabricated using a variety of conductive threads formed by coating textile fibers and through the use of copper fibers. These coils have been experimentally characterized and evaluated for use in wireless power transfer applications. The effects of coil geometry and separation on the DC-DC power transfer efficiency using Qi standard compliant driver and receiver circuits are reported
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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