E. Torres

Polyolefin materials and technology in artificial turf I: Yarn developments

Artificial turf surfaces with “soft” yarns are increasingly used because of haptic attractiveness and player-friendliness. Linear low density polyethylene (LLDPE) with low density is preferred to achieve the desired softness. The choice of LLDPE material is guided by the performance requirements outlined in the FIFA Quality Concept for football turf. Different LLDPE materials were extruded into monofilament yarns on production scale machinery. Yarn tenacity, elongation and shrinkage were characterized and built into a statistical model to relate processing conditions and material properties to yarn performance. Processing conditions and choice of particular LLDPE greatly influence yarn performance. Shrinkage is identified as an important measure to characterize residual stress in low density LLDPE yarns and can be related to performance in the Lisport test used to determine the durability of an artificial turf yarn. The model results are used to optimize properties of yarn made with a given low density LLDPE. Improved durability and softness is shown to be synergistic with superior elastic recovery (resiliency) of low density LLDPE. With use of the processing model the performance of artificial turf yarns can be optimized for the best possible playing conditions.

Evaluating the impact of geographic distribution of photovoltaic self-consumption on energy losses

Photovoltaic (PV) self-consumption concept has emerged as a sustainable and economically viable alternative to save electricity provided by electric utilities. There are several concerns about the massive deployment of PV self-consumption installations. One of them is the influence of such installations on energy losses. Several research works have indicated that PV self-consumption installations reduce or increase energy losses depending on their penetration level. These research works use a uniform geographic distribution of PV self-consumption installations. However, rural areas are more likely to have a higher PV self-consumption penetration rate than urban areas and so, a uniform distribution may not be a proper approach. This paper proposes a methodology with different levels of geographic distribution to evaluate this issue. This methodology has been applied to the electric network of Murcia (Spain). Simulation results show that there is a significant influence of geographic concentration or dispersion of PV self-consumption systems on energy losses.

Modeling and validation of photovoltaic plants using generic dynamic models

Dynamic simulation models of photovoltaic plants are needed during the design stage of the plant, to show compliance with grid code requirements, as well as after commissioning, to validate the model response with the real plant performance. Due to the large number of PV installations and inverter models, there is a strong need to move from specific manufacturers user models to generic models, as the ones proposed by the Western Electricity Coordinating Council (WECC). This paper discusses the need for generic models, introduces the photovoltaic plant model developed by WECC and presents a case of generic model parameterization and validation of a commercial three-phase inverter, based on factory test. The simulation results show the validity of the generic model to reproduce the Low Voltage Fault Ride Through (LVFRT) capability of the inverter.

A Survey on Innovative Solutions and Projects for the Integration of Renewable Generation in Weak Power Grids

This paper deals with the most relevant issues about the integration of renewable generation in weak power grids. Initially, the main parameters that characterize these types of networks are reviewed, in terms of short circuit power, system inertia and frequency and voltage characteristics. Afterwards, improvement measures in the structure of weak power grids are proposed, analyzing different storage technologies in order to guarantee a high efficiency and reliability of the power system. Finally, the paper reviews the most prominent projects developed worldwide which include the integration of renewable energy in weak grids.