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This work aims to assess the impact of renewable energy incentives, particularly that of the feed-in tariff (FiT), on the long-term development of solar photovoltaics (PVs). With this aim, the paper introduces a dynamic model based on nonlinear delay differential algebraic equations to simulate the evolution of the PV capacity and its commitment in the power grid. The model assumes the FiT budget, the PV cost and willingness of the public to install PVs as the main drivers for solar PV installations. In particular, the learning-by-doing concept to model the PV cost and consequently the PV deployment is proposed for the first time in this paper. The accuracy of the model is validated against historical data of two of the biggest PV markets in the world driven by FiT, namely, Italy during 2008–2014, and Germany during 2000–2014. A sensitivity analysis based on the Italian PV market is carried out to identify the impact of the parameters of the proposed model. Results indicate that the proposed model is a valuable tool that can help policymakers in the decision-making process, such as the definition of the FiT price and the duration of the incentives. [ABSTRACT FROM AUTHOR]

• Dynamic modeling of a fault arc burning in air occurring on overhead transmission lines and its numerical simulation in time-domain using an electromagnetic transients program. • Determination of the secondary arc duration in case of a single-phase autoreclosure on EHV transmission systems. • Influence of various factors on mixed transmission lines consisting of several overhead line and underground cable sections compensated by shunt reactors. The transmission system expansion plan of Germany foresees several new EHV (Extra High Voltage) transmission lines to transmit bulk power generated by wind farms in the north of Germany to the South. Some of these EHV lines will be so called "mixed lines" consisting of several underground cable and overhead line sections. The high charging current of XLPE cables has to be compensated by shunt reactors. A planned double-circuit 380 kV transmission line with total length of ca. 110 km is of interest for the analysis of SPAR (single-phase autoreclosure) operation in this paper, where a cable section along the line has a length of 5.5 km. By means of electromagnetic transients simulations the maximum secondary arc duration will be determined for the mixed line under various operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents the numerical code VibPile for simulation of the nonlinear dynamic response of large monopiles under harmonic loading and installation by vibration or impact driving. VibPile is based on a nonlinear FE model of the pile-soil interaction along the shaft and the tip by elasto-plastic springs representing the near field and elasto-dynamic elements (spring and dashpot) for the far field. While for the shaft friction and tip resistance the classical engineering solutions, such as those by standards or guidelines (e.g. API) and literature, are used in the numerical simulations, new computational models are developed for the dynamic response of the soil inside the pile and the far-field elasto-dynamic springs. What primarily differentiates the present model from the existing ones is the treatment of the soil inside the monopile together with the stiffness at the pile tip. Most existing models are based on the solutions for piles with solid sections or pipe piles in which the soil inside the pile follows the pile vibrations like a solid section. For large diameter monopiles commonly used for offshore wind turbines, both the soil response inside the pile and the stiffness of the pile tip are different. The developed model is verified against the vibro-pile test data collected at Altenwalde, Germany. The results include axial pile strains, accelerations, and shear stresses along the pile shaft and at the pile tip. Both the strains and accelerations as well as the rate of pile driving measured at Altenwalde are reproduced by VibPile with reasonable accuracy. Sensitivity analyses are presented to highlight the effects of the shear wave velocity and shear strength at the pile-soil interface on the pile driving rate. Moreover, the effect of the natural period of the inner soil on the pile driving is investigated. • New simulation model for vibro-piling. • New analytical solutions for dynamic stiffness of hollow, large diameter monopiles for small and high frequencies. • Verification of developed model against detailed large-scale pile-driving tests. • Highlighting importance of soil parameters on vibro-piling simulations. [ABSTRACT FROM AUTHOR]

Biomass combined heat and power plants (CHPPs) can operate target-specifically because of their controllability while supporting decarbonization in district heating. The transition from the German Renewable Energies Act funding, which has promoted biomass CHPPs but is now about to expire, to direct marketing, is a major economic challenge for many biomass-heating grids. To successfully accomplish it, the flexible operation of biomass CHPPs, compared to the previous baseline-operation, is becoming an increasingly important requirement if participation in the electricity markets is to remain profitable. This paper presents a techno-economic assessment of flexible CHPP operation in a modeled district heating system with a CHPP, a peak load boiler and a thermal heat storage. The simulation model compares two cases - a natural gas and a wood-chip gasifier CHPP. The analysis of the results investigates the parameters that need to be adapted to make biomass-fired CHPP heating grids more efficient compared to fossil-fired CHPP heating grids in a flexible operating scenario. It highlights the technical and economic superiority of a fossil-fired CHPP in flexible operation in comparison to the wood gasifier system. The introduction of a CO 2 -tax on natural gas as a fuel, currently under discussion in Germany, would increase the competitiveness of the wood gasifier. • Simulation model of a district heating system. • Model units are wood or natural CHP plant, peakload boiler and heat storage. • Three scenarios for CHP plant dispatch under consideration of electricity prices. • Focus on dynamic differences of the CHP plant operation strategy. • Results show limitations in operational flexibility of the wood gas CHP plant. [ABSTRACT FROM AUTHOR]