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Sports centers are significant energy consumers. This article outlines the engineering design for a comprehensive energy performance upgrade of the indoor sports hall in Arkalochori, Greece, and presents the projected results. The indoor sports hall constitutes a major sport facility on the mainland of Crete, hosting a broad cluster of sport municipal activities and the official basketball games of the local team in the 2nd national category. Having been constructed in the mid-1990s, the facility exhibits very low thermal performance, with considerably high U-factors for all constructive elements (from 4 to 5 W/m2∙K), still use of diesel oil for indoor space heating and domestic heat water production, and ineffective old lamps and luminaries covering the lighting needs of the facility. The energy performance upgrade of the indoor sports hall was studied, and the following passive and active measures were considered: Opaque-surfaces' thermal insulation and openings' replacement, stone wool panels, installation of heat pumps for indoor space conditioning, removal of diesel oil for any end use, production of domestic hot water from a novel solar-combi system, upgrade of lighting equipment, installation of solar tubes on the main sports hall roof for natural lighting as well as of a photovoltaic system for covering the remaining electricity consumption. With the proposed interventions, the studied building becomes a zero-energy facility. The payback period of the investment was calculated at 26 years on the basis of the avoided energy cost. This work was funded by the "NESOI" Horizon 2020 project and received the public award "Islands Gamechanger" competition of the NESOI project and the Clean Energy for EU Islands initiative. [ABSTRACT FROM AUTHOR]

A power-quality (PQ) measure is introduced in this paper. The proposed measure, based on the Shannon's entropy, expresses the deviation of the examined voltage cycle from the ideal one. Two entropy concepts are introduced--the spectral and the probabilistic entropy. The two entropies, calculated for every voltage cycle, are properly combined to provide the PQ measure. The PQ measure is represented graphically on a 2-D Cartesian coordinate system. The PQ measure is calculated for the most common PQ disturbances. The graphical representation of the calculated PQ measurements leads to the definition of an area of acceptable PQ on the PQ measure 2-D diagram. The PQ of a power system may be evaluated by the proposed measure, by implementing voltage measurements during predetermined time periods in selected network nodes. The produced electricity price may be configured in terms of the measured PQ. Index Terms--Disturbances, dynamic, events, measure, power, quality, security, variations.

Featured Application: The article highlights the huge possibilities for energy saving in large size sports facilities and anticipates to constitute a benchmark reference on energy performance upgrade of similar infrastructure. Energy performance upgrade of stadiums constitutes a complex and demanding task because of both the size and the variety of the involved energy loads. The present article aims to summarize the basic results of the implemented study on the energy performance upgrade of the Pancretan Stadium, Crete, Greece. This target was approached with a cluster of passive and active measures: replacement of old openings, a photovoltaic station, an open loop geothermal system, installation of energy-efficient lighting devices, a solar-biomass combi system and a Building Energy Management System (BEMS) for the control of the main energy consumptions. The dimensioning of all the proposed active systems is optimized through the computational simulation of their annual operation. With the applied technologies, the achieved annual energy saving percentage exceeds 83%. The Renewable Energy Sources annual penetration percentage is calculated at 82% versus the annual energy consumption. The Stadium's energy performance is upgraded from rank D to rank A+, according to the European Union's directives. The set-up cost of the under consideration energy performance upgrade systems is approximately calculated at 2,700,000 €, with a payback period of 12 years, calculated versus the achieved monetary savings due to the reduction of the consumed energy resources. [ABSTRACT FROM AUTHOR]

The scope of this article is to review the potential causes that can lead to wind turbine blade failures, assess their significance to a turbine's performance and secure operation and summarize the techniques proposed to prevent these failures and eliminate their consequences. Damage to wind turbine blades can be induced by lightning, fatigue loads, accumulation of icing on the blade surfaces and the exposure of blades to airborne particulates, causing so-called leading edge erosion. The above effects can lead to damage ranging from minor outer surface erosion to total destruction of the blade. All potential causes of damage to wind turbine blades strongly depend on the surrounding environment and climate conditions. Consequently, the selection of an installation site with favourable conditions is the most effective measure to minimize the possibility of blade damage. Otherwise, several techniques and methods have already been applied or are being developed to prevent blade damage, aiming to reduce damage risk if not able to eliminate it. The combined application of damage prevention strategies with a SCADA system is the optimal approach to adequate treatment. [ABSTRACT FROM AUTHOR]