1,721,069 research outputs found
Gender as a factor in delivering sustainable energy
Full text linkThis paper reviews the role of energy in contributing to the solution of a major development objective: moving people out of poverty. Understanding gender issues, especially the crucial role women play in household energy provision, is important in the design and implementation of appropriate energy interventions. The role energy plays in improving women’s lives and the role women can play in providing energy services is reviewed. Some indictors of success factors for sustainable energy interventions are identified based on recent field experience
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
Effects on photovoltaic solar module performance in the UK climate
No full textPresently, PV devices are rated on the basis of a standard test condition (STC) efficiency and not on their energy production, which would be a much better parameter for their cost per generated kWh. There is a lack of knowledge of factors affecting performance of thin film PV devices, especially operating in maritime climates such as the UK's. Modules studied in this investigation include crystalline, polycrystalline and amorphous silicon, cadmium telluride and copper indium diselenide. The different factors affecting the performance of PV modules operated in the UK climate are investigated. The main effects identified are changes in the spectrum, operating temperature and irradiance, each affecting device performance according to the type of cell material. The spectral effect is predictably more pronounced for the wider band gap materials (amorphous silicon and cadmium telluride) and includes two separate identifiable effects, termed primary and secondary. The primary spectral effect depends on the availability of spectrally useful irradiance and is more pronounced for the amorphous silicon (a-Si) single junctions, where it varies by + 5% to -9% with respect to the annual average. There is also evidence of a secondary effect in the a-Si multijunctions, due to mismatch of current between the series connected sub-cells, the magnitude of which is much less than the primary spectral effect, but is noticeable nevertheless. The materials with narrower band gaps (polycrystalline, crystalline and copper indium diselenide) suffer more significantly from thermal effects and less from spectral effects than do devices with a wider band gap. The effect of radiation intensity is device-specific; some devices (crystalline and polycrystalline) benefit from increased irradiance, although some thin films show a deterioration of efficiency with increasing irradiance. The importance of shunt and series resistance is discussed in this context
Thermal modelling of a building with an integrated ventilated PV facade
No full textThis paper presents a dynamic thermal model based on TRNSYS, for a building with an integrated ventilated PV façade/solar air collector system. The building model developed has been validated against experimental data from a 6.5 m high PV façade on the Mataro Library near Barcelona. Preheating of the ventilation air within the façade is through incident solar radiation heating of the PV elements and subsequent heat transmission to the air within the ventilation gap. The warmed air can be used for building heating in winter. Modelled and measured air temperatures are found to be in good agreement. The heating and cooling loads for the building with and without such a ventilated façade have been calculated and the impact of climatic variations on the performance such buildings has also been investigated. It was found that the cooling loads are marginally higher with the PV façade for all locations considered, whereas the impact of the façade on the heating load depends critically on location
Parameter estimation for ventilated photovoltaic facades
No full textIn this paper, the estimation of thermal parameters that describe the performance of ventilated photovoltaic (PV) façades integrated into buildings is investigated. In the most simpli” ed representation of the thermal characteristics of the building, the key factors are the coef” cients of solar heat gain and total heat loss. For an integrated building with a ventilated PV façade, a more accurate representation involves the interactions between the interior space, the ventilated space of the façade construction, the exterior PV elements, and the outside environmental conditions. The heat loss from the interior consists of both losses to ambient and to the ventilation air via the inner glazing or panelling. A direct numerical approach has been developed to identify the parameters that describe these heat transfer processes. The method allows the heat transfer coef” cients to be obtained directly from data measured on an operational ventilated PV façade. The results are compared with values taken from conventional practice
Spectral dependence of amorphous silicon photovoltaic device performance
No full textThe short circuit currents of a single, double and triple junction amorphous silicon (a-Si) device are investigated for changes with spectral irradiance variation. Two effects have been previously identified; (i) a primary spectral effect that depends purely on the availability of spectrally-useful irradiance within the absorption band of the device, and (ii) a secondary effect that depends also on the spectral distribution within this band. The average photon energy (APE) has been introduced as a useful parameter for describing spectra. It is a device-independent environmental parameter, which effectively puts a figure to the blueness of a spectrum and readily allows the analysis of spectral effects on photovoltaic devices. Single junction cells have a better performance as light becomes more blue-shifted. Double and triple junction cells have a performance that is maximised when the received spectrum is matched to the absorption profile and that decreases when the radiation is either red- or blue-shifted
A wind-powered seawater reverse-osmosis system without batteries
No full textThe development of small-scale stand-alone desalination systems is important to communities on islands and in isolated inland areas. In such places, electricity supplies are often expensive and unreliable, while the wind resource is abundant. The system presented here comprises a 2.2 kW wind turbine generator powering a variable-flow Reverse osmosis (RO) desalination unit. It is highly efficient, rugged, built with off-the-shelf components and suitable for use in remote areas. Operation at variable-flow allows the uncertainty and variability of the wind to be accommodated without need of energy storage. Batteries, which are common in stand-alone systems, are avoided and water production is dependent on the instantaneous wind speed. A model-based control strategy is used to independently maximize both the energy extracted from the wind and the water output of the RO unit. A computer model of the system has been developed based on component models, identified through laboratory testing. Performance predictions are presented and discussed
A small-scale seawater reverse-osmosis system with excellent energy efficiency over a wide operating range
No full textA small-scale seawater reverse-osmosis system with excellent energy efficiency is presented. The system promises to deliver up to 460 l/h of potable water, from seawater (at 40,000 ppm), while consuming less than 1600 W of electrical power. This represents a specific energy consumption of less than 3.5 kWh/m3. Moreover, the flow may be controlled in order to reduce the power consumption by a factor of four without any significant loss of efficiency — the specific energy consumption remains near to 3.5 kWh/m3. The keys to these impressive figures are the energy recovery provided by the Clark pump, from Spectra Watermakers Inc., and the use of a variable water recovery ratio control algorithm, developed by CREST. The significance of the system is that it may be operated from variable intermittent renewable-energy sources, such as wind and solar-photovoltaic (PV), without need of batteries. Results of laboratory testing and extensive modeling are presented
Laboratory demonstration of a photovoltaic-powered seawater reverse-osmosis system without batteries
No full textA prototype photovoltaic-powered reverse-osmosis system has been constructed at CREST, Loughborough, UK. The rate of production of fresh water varies throughout the day according to the available solar power, and thus, the system operates without need of batteries. The system is designed to operate from seawater, and a Clark pump brine-stream energy recovery mechanism is coupled with a variable recovery ratio technique to achieve a specific energy consumption of less than 4 kWh/m3 over a wide range of operation. Measurements showing the variable operation over a two-day period are presented and discussed
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