The current industrial landscape is becoming increasingly aware of the need to optimize energy use and management for all domains, including telecommunications. Among others, RF Energy Harvesting is a promising technique for 5G systems as an alternative to traditional energy supply sources. This paper presents 5G landscape and ecosystem. It positions RF-Energy Harvesting in 5G context and reviews its techniques. It also considers constraints and research trends for different aspects needed to make RF energy harvesting ready for deployment along with 5G enabling technologies.
Accurate and precisess estimation of spatio-temporal variability of solar radiation is critical. Some commonly used models evaluate this variability using methods in which the data required for estimating atmospheric attenuation may not be easily accessible for some study areas. Here, a daily solar radiation estimation method which uses ambient air temperature, a Digital Elevation Model, time of year, and monthly radiation estimates from Solar Analyst model has been proposed. The objective was to use air temperature-based empirical models for atmospheric transmissivity and diffuse fractions to vary total monthly radiation estimation from Solar Analyst, and then calculate total daily radiation as a fraction of total monthly radiation by applying a daily transmissivity-based ratio, as air temperature data are readily available at most locations on the planet. Results revealed that daily solar radiation can be estimated very well, with Mean Absolute Bias Error of around 40-53 W m −2 or Mean Bias Error of ± 10%, under all sky conditions at seven sites in diverse climate regions, using significantly less input data. The presented method is an improvement over previously used methods with Mean Bias Error of under 10% but more input parameters. Furthermore, the hourly solar radiation values can be calculated using the presented method using the ratio between daily and hourly radiation, for example from literature values and estimated daily insolation. The result also showed that the method is more useful for those stations with substantially higher numbers of sunny days than cloudy or partly cloudy days because the uncertainty of the model decreased from cloudy to sunny sky conditions. The implemented Digital Elevation Models environment of this method makes it applicable in many studies that need spatial estimation of solar radiation, especially for solar energy generation projects.
Keywords Solar radiation · Digital elevation model · Solar analyst · Atmospheric transmissivity · Air temperature
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The aim of this paper is to study experimentally and theoretically the effect of some geometrical parameters on low temperature differential Stirling engines (LT-SE) performance. The studied parameters are: the phase angle, the compression ratio and the dead volume. Results show that for optimizing the performance of these engines, dead volume should be minimized, the compression ratio should be maximized and the optimal phase angle for the gamma type is 90°. For the adopted theoretical model, based on Schmidt theory, even if theoretical numerical results are different from those found experimentally, but it still remains a valid model for finding out some parameters effect on the LT-SE performance, and for calculating approximately the engine work and power.
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