TiO2-based nanocoating with self-cleaning and anti-reflective properties: effects on PV performance

Photovoltaic modules operating in field conditions exhibit a significant reduction in their power output due to dust accumulated on their surface. Depending on the amount of dust accumulated the reduction in peak power has been reported in the range of 5-15%. The accumulated dust is linked to meteorological and environmental parameters such as humidity, precipitation, solar radiation, ambient temperature, dusty winds, air pollution, etc., but also to the location and surroundings of the installation and the period for which the PV modules have been left without cleaning. To reduce the effect of dust, research has been recently focused on coatings with self-cleaning properties that may be applied on PV glass surface. Also, coatings with spectral selective properties have been investigated to enhance PV performance. The purpose of this study is to examine the effect of a nanocoating with self-cleaning and anti-reflective properties on the performance of a PV module when applied on its glass surface. Particular interest is given to its anti-reflective properties which are assessed for angles-of-incidence of solar radiation greater than 40o, where reflectance is generally higher. The performance of two same PV modules one with and one without the coating is compared

The Social Scope of Roman Identity in Byzantium: An Evidence-Based Approach

 Η ΚΟΙΝΩΝΙΚΗ ΕΜΒΕΛΕΙΑ ΤΗΣ ΡΩΜΑΪΚΗΣ ΤΑΥΤΟΤΗΤΑΣ ΣΤΟ ΒΥΖΑΝΤΙΟ: ΜΙΑ ΠΡΟΣΕΓΓΙΣΗ ΒΑΣΕΙ ΤΩΝ ΓΡΑΠΤΩΝ ΠΗΓΩΝ Έχουν προταθεί προσφάτως αντίθετες ερμηνείες αναφορικά με την κοινή διαπίστωση ότι οι Βυζαντινοί «αυτοαποκαλούνται Ρωμαίοι». Σύμφωνα με μία άποψη, το Βυζάντιο ήταν ρωμαϊκό έθνος-κράτος, ενώ αντιθέτως έχει υποστηριχθεί επίσης ότι η ρωμαϊκή ταυτότητα ήταν αποκλειστικότητα μιας αριθμητικά περιορισμένης «ελίτ». Το παρόν άρθρο χαρτογραφεί για πρώτη φορά την κοινωνική εμβέλεια της ρωμαϊκής ταυτότητας, όπως προκύπτει από τις γραπτές πηγές: ποιούς εννοούσαν οι Βυζαντινοί και οι Άραβες συγγραφείς, όταν χρησιμοποιούσαν τον όρο «Ρωμαίοι»; Οι Ρωμαίοι ήταν ένα στενό κοινωνικό-οικονομικό στρώμα ή είχαν συνείδηση ότι αποτελούσαν το μεγαλύτερο μέρος του πληθυσμού της αυτοκρατορίας; Από την ανάλυση των κειμένων προκύπτει ότι η ρωμαϊκή ταυτότητα δεν περιοριζόταν στην πολιτικοκοινωνική ελίτ της αυτοκρατορίας, αλλά αφορούσε σε όλα σχεδόν τα κοινωνικά στρώματα, τόσο στην Κωνσταντινούπολη όσο και στην επαρχία. Η αντίθετη ερμηνεία περί ελίτ βασίζεται σε παραπλανητικές σύγχρονες θεωρίες και όχι στις πρωτογενείς πηγές

The Chronology of the Reign of Alexios III Komnenos for the years 1198-1202 AD and its Implications

Η χρονολογία των γεγονότων της βασιλείας του Αλεξίου Γ΄ για τα έτη 1198 -1202 και οι επιπτώσεις της Η χρονολογία των γεγονότων της βασιλείας του Αλεξίου Γ΄   απασχόλησε την έρευνα για τελευταία φορά προ πεντηκονταετίας, χωρίς όμως να αξιοποιηθούν όλα τα διαθέσιμα στοιχεία. Στην μελέτη επανεξετάζεται το θέμα και ανασκευάζεται η εικόνα του συγκεκριμένου αυτοκράτορα, που παρουσιάζεται από τον Νικήτα Χωνιάτη ως οκνηρός, αδιάφορος και συβαρίτης

The Social Scope of Roman Identity in Byzantium: An Evidence-Based Approach

 Η ΚΟΙΝΩΝΙΚΗ ΕΜΒΕΛΕΙΑ ΤΗΣ ΡΩΜΑΪΚΗΣ ΤΑΥΤΟΤΗΤΑΣ ΣΤΟ ΒΥΖΑΝΤΙΟ: ΜΙΑ ΠΡΟΣΕΓΓΙΣΗ ΒΑΣΕΙ ΤΩΝ ΓΡΑΠΤΩΝ ΠΗΓΩΝ Έχουν προταθεί προσφάτως αντίθετες ερμηνείες αναφορικά με την κοινή διαπίστωση ότι οι Βυζαντινοί «αυτοαποκαλούνται Ρωμαίοι». Σύμφωνα με μία άποψη, το Βυζάντιο ήταν ρωμαϊκό έθνος-κράτος, ενώ αντιθέτως έχει υποστηριχθεί επίσης ότι η ρωμαϊκή ταυτότητα ήταν αποκλειστικότητα μιας αριθμητικά περιορισμένης «ελίτ». Το παρόν άρθρο χαρτογραφεί για πρώτη φορά την κοινωνική εμβέλεια της ρωμαϊκής ταυτότητας, όπως προκύπτει από τις γραπτές πηγές: ποιούς εννοούσαν οι Βυζαντινοί και οι Άραβες συγγραφείς, όταν χρησιμοποιούσαν τον όρο «Ρωμαίοι»; Οι Ρωμαίοι ήταν ένα στενό κοινωνικό-οικονομικό στρώμα ή είχαν συνείδηση ότι αποτελούσαν το μεγαλύτερο μέρος του πληθυσμού της αυτοκρατορίας; Από την ανάλυση των κειμένων προκύπτει ότι η ρωμαϊκή ταυτότητα δεν περιοριζόταν στην πολιτικοκοινωνική ελίτ της αυτοκρατορίας, αλλά αφορούσε σε όλα σχεδόν τα κοινωνικά στρώματα, τόσο στην Κωνσταντινούπολη όσο και στην επαρχία. Η αντίθετη ερμηνεία περί ελίτ βασίζεται σε παραπλανητικές σύγχρονες θεωρίες και όχι στις πρωτογενείς πηγές

Wind power forecasting using historical data and artificial neural networks modeling

One of the main parameters affecting the reliability of the renewable energy sources (RES) system, compared to the local conventional power station, is the ability to forecast the RES availability for a few hours ahead. To this end, the main objective of this work is the prognosis of the mean, maximum and minimum hourly wind power (WP) 8hours ahead. For this purpose, Artificial Neural Networks (ANN) modeling is applied. For the appropriate training of the developed ANN models hourly meteorological data are used. These data have been recorded by a meteorological mast in Tilos Island, Greece. For the evaluation of the developed ANN forecasting models proper statistical evaluation indices are used. According to the results, the coefficient of the determination ranges from 0.285 up to 0.768 (mean hourly WP), from 0.227 up to 0.798 (maximum hourly WP) and from 0.025 up to 0.398 (minimum hourly WP). Furthermore, the proposed forecasting methodology shows that is able to give sufficient and adequate prognosis of WP by a wind turbine in a specific location 8 hours ahead. This will be a useful tool for the operator of a RES system in order to achieve a better monitoring and a better management of the whole system

Improving understanding of energy autonomy: a systematic review

Autonomy is often cited as a key aspect of energy systems. Previous academic literature on energy autonomy has predominantly approached it from a technological perspective, and conceptualized it as self-sufficiency of energy production. In addition to self-sufficiency, autonomous energy users and communities often aim to create energy systems that treat different stakeholders as equals, with a balanced distribution of costs and benefits. This paper has two aims. First, it aims to clarify the concept of ‘energy autonomy’. Second, it aims to provide an overview of existing literature addressing energy autonomy, identifying relevant publications and publication outlets, as well as main research themes and activities. The results, based on a systematic review of 71 peer-reviewed academic articles, show that energy autonomy research has increased in the last twenty years. The results also show how existing literature has understood, and used, the concept of energy autonomy in varying ways. Furthermore, the paper reveals how motivations, technologies, and scales differ in energy autonomy projects. While the aim of reaching energy autonomy is often motivated by economic and/or social reasons, these aspects are nevertheless rarely discussed in academic literature as the predominant focus tends to be on technological issues and self-sufficiency. The paper concludes with energy policy implications and avenues for future research

Improving understanding of energy autonomy: a systematic review

Autonomy is often cited as a key aspect of energy systems. Previous academic literature on energy autonomy has predominantly approached it from a technological perspective, and conceptualized it as self-sufficiency of energy production. In addition to self-sufficiency, autonomous energy users and communities often aim to create energy systems that treat different stakeholders as equals, with a balanced distribution of costs and benefits. This paper has two aims. First, it aims to clarify the concept of ‘energy autonomy’. Second, it aims to provide an overview of existing literature addressing energy autonomy, identifying relevant publications and publication outlets, as well as main research themes and activities. The results, based on a systematic review of 71 peer-reviewed academic articles, show that energy autonomy research has increased in the last twenty years. The results also show how existing literature has understood, and used, the concept of energy autonomy in varying ways. Furthermore, the paper reveals how motivations, technologies, and scales differ in energy autonomy projects. While the aim of reaching energy autonomy is often motivated by economic and/or social reasons, these aspects are nevertheless rarely discussed in academic literature as the predominant focus tends to be on technological issues and self-sufficiency. The paper concludes with energy policy implications and avenues for future research

Bringing innovation to market: business models for battery storage

Power systems around the world have undergone significant transitions towards a decentralization and decarbonization with higher requirements on supply security and flexibility. Technology advancement helps to improve energy efficiency and bring down cost, which in turn promote the growth of battery storage internationally. Business models of battery storage remain vague given its early stages of development but it is clear that there is no universal business model for batteries given the breadth of applications. In this study, we review the main components of existing business models and highlight the areas to be strengthened in a novel business model. Business models should be distinguished at different scales (utility-scale; behind-the-meter application; community-island mode operation) addressing different needs (to replace existing system or to add new capacity). A successful business model of a battery storage system needs to take into account electricity system transition, market and regulatory barriers, among others. Last but not least, it is important to consider innovations in other technologies for the design of a business model