An effective simulation model to predict and optimize the performance of single and double glaze flat-plate solar collector designs

This paper outlines and formulates a compact and effective simulation model, which predicts the performance of single and double glaze flat-plate collector. The model uses an elaborated iterative simulation algorithm and provides the collector top losses, the glass covers temperatures, the collector absorber temperature, the collector fluid outlet temperature, the system efficiency, and the thermal gain for any operational and environmental conditions. It is a numerical approach based on simultaneous guesses for the three temperatures, Tp plate collector temperature and the temperatures of the two glass covers Tg1, Tg2. A set of energy balance equations is developed which allows for structured iteration modes whose results converge very fast and provide the values of any quantity which concerns the steady state performance profile of any flat-plate collector design. Comparison of the results obtained by this model for flat-plate collectors, single or double glaze, with those obtained by using the Klein formula, as well as the results provided by other researchers, is presented

On the relationship factor between the PV module temperature and the solar radiation on it for various BIPV configurations

Temperatures of c-Si, pc-Si and a-Si PV modules making part of a roof in a building or hanging outside windows with various inclinations were measured with respect to the Intensity of the solar radiation on them under various environmental conditions. A relationship coefficient f was provided whose values are compared to those from a PV array operating in a free standing mode on a terrace. A theoretical model to predict f was elaborated. According to the analysis, the coefficient f takes higher values for PV modules embedded on a roof compared to the free standing PV array. The wind effect is much stronger for the free standing PV than for any BIPV configuration, either the PV is part of the roof, or placed upon the roof, or is placed outside a window like a shadow hanger. The f coefficient depends on various parameters such as angle of inclination, wind speed and direction, as well as solar radiation. For very low wind speeds the effect of the angle of inclination, β, of the PV module with respect to the horizontal on PV temperature is clear. As the wind speed increases, the heat transfer from the PV module shifts from natural flow to forced flow and this effect vanishes. The coefficient f values range from almost 0.01 m2°C/W for free standing PV arrays at strong wind speeds, vW>7m/s, up to around 0.05 m2°C/W for the case of flexible PV modules which make part of the roof in a BIPV system

The Geography of Employment Polarisation in Britain

This paper investigates the regional and subregional patterns of employment polarisation in Great Britain. Extending recent econometric evidence for employment polarisation at the national level, the focus of analysis is to examine the geography of this polarisation. Methodological issues on how we define and measure ‘job polarisation’ are presented and plausible theories for explaining this polarisation are reviewed. It has been suggested that low-quality jobs, defined either as low-paid jobs or low-skill jobs, depend increasingly on the growth of employment and wages of high-quality jobs. The presence of a growing high-income workforce in the economy generates consumer demand for local services leading this way to an increase in the low-skill employment sector. As these local services refer mainly to the non-traded sector of the economy, this hypothesis implies physical proximity of the low-skilled and high-skilled jobs. Therefore, in the empirical part of the paper, econometric techniques are used in order to investigate the location of job polarisation. Specifically, we examine whether employment polarisation happens within regions or just across regions and test further for such evidence at the subregional level and neighbouring localities. New Earnings Survey (NES) microdata that span over a long time period and are workplace-based are used for such purposes. Furthermore, evidence for dependency of low-skill jobs on high-skill ones at the local level and possible urban-specificity of the phenomenon are investigated. Taking into account the importance of employment shifts, changes in median wages of the different jobs and within job-inequality for explaining the increase in earnings inequality in GB in the recent decades, the contribution of employment polarisation to the actual rise in inequality is examined. Additionally, the paper examines whether employment polarisation patterns are associated with regional differences in the labour force composition.

Intelligent energy buildings based on RES and Nanotechnology

The paper presents the design features, the energy modelling and optical performance details of two pilot Intelligent Energy Buildings, (IEB). Both are evolution of the Zero Energy Building (ZEB) concept. RES innovations backed up by signal processing, simulation models and ICT tools were embedded into the building structures in order to implement a new predictive energy management concept. In addition, nano-coatings, produced by TiO2 and ITO nano-particles, were deposited on the IEB structural elements and especially on the window panes and the PV glass covers. They exhibited promising SSP values which lowered the cooling loads and increased the PV modules yield. Both pilot IEB units were equipped with an on-line dynamic hourly solar radiation prediction model, implemented by sensors and the related software to manage effectively the energy source, the loads and the storage or the backup system. The IEB energy sources covered the thermal loads via a south façade embedded in the wall and a solar roof which consists of a specially designed solar collector type, while a PV generator is part of the solar roof, like a compact BIPV in hybrid configuration to a small wind turbine

Thermal modelling and experimental assessment of the dependence of PV module temperature on wind velocity and direction, module orientation and inclination

A theoretical and experimental analysis of PV module temperature under various environmental conditions is presented in relation to module inclination, wind velocity and direction. The present experimental study, makes use of hourly PV temperature data collected from a double-axis sun-tracking PV system and environmental parameters monitored for a period of one year. The f coefficient which relates the PV module temperature with the intensity of the global solar radiation on the PV plane and the ambient temperature, is assessed in relation to the angle of PV inclination, the wind velocity and the angle of incidence of the wind stream on the PV surface, either front or back. The f coefficient is evaluated both experimentally and theoretically through thermal modelling based on the energy balance equation. The simulation model developed in this study considers heat convection by natural and air forced flow, the flow pattern either laminar or turbulent, the relative geometry of the PV module with respect to the wind direction, and the radiated heat by the PV module. Various expressions for the forced heat convection coefficient available in the literature are tested within the thermal model with reference to the windward and leeward side of the PV module, and their applicability to PV thermal analysis is experimentally assessed in terms of the agreement shown with measured data. The values of the f coefficient provided by the simulation model lie very close to the experimental data for the entire range of PV inclination angles, wind velocities and wind directions tested

Perception of Reverberation in Domestic and Automotive Environments

nrpages: 227status: publishe