The paper presents a study of transient spark: a streamer-to-spark transition discharge in air at atmospheric pressure. The transient spark (TS) is applicable for flue gas cleaning or biodecontamination and has a potential in combustion, and flow control applications. Despite the DC applied voltage, TS has a pulsed character with short (~10-100 ns) high current (>1A) pulses, with repetitive frequencies 1-10 kHz. The electron density n e ~10 17 cm −3 at maximum is reached in TS using relatively low power delivered to the plasma (0.2-3W). The estimate of temporal evolution of n e was derived from the resistance of plasma, obtained by detailed analysis of the electric circuit representing TS and the plasma diameter measurements using a fast iCCD camera. This estimate was compared with n e calculated from the measured Stark broadening of H α line. Good agreement was obtained when plasma diameter was approximated using the full width at the half maximum of the radial emission intensity profile of the plasma channel after the Abel inversion.

The paper presents investigations of self-pulsing discharges in atmospheric pressure air preheated to 300-1000 K. Despite using a direct-current power supply, two self-pulsing discharge regimes, a repetitive transient spark (TS) and a repetitive streamer (RS) were generated. The pulse repetition frequency, on the order of a few kHz, can be controlled by adjusting the generator voltage. The TS is a discharge initiated by a streamer, followed by a short (tens of ns) spark current pulse (∼ 1 A), associated with the total discharging of the internal capacity of the electric circuit. The TS is suitable for the study of 'memory' effects (pre-heating, preionization) on the mechanisms of streamer-to-spark transition and electrical breakdown in atmospheric pressure air. The TS regime was stable below ∼600 K. Above ∼600 K, a stable repetitive streamer (RS) regime was observed. In this regime, the breakdown and spark did not occur. After the initial streamer, the internal capacity of the electrical circuit discharged partially. With further pre-heating of the gas, the stable TS appeared again at ∼1000 K.

The kinetic model simulating plasma chemistry induced by Transient Spark (TS) discharge in air is presented in this paper. TS is a dc-driven self-pulsing discharge of streamer-to-spark transition type. The presented kinetic model defines the temporal evolution of reduced electric field strength E/N, gas temperature, and density of neutrals N during the evolution of TS discharge, so that calculated electron density is in agreement with experimental results. We studied the mechanism of the streamer-to-spark transition and breakdown in TS using this model. We assume that the breakdown mechanism in TS is based on the gas density decrease and can be summarized as follows: heating of the channel → increase in the pressure → hydrodynamic expansion → decrease in N in the core of the channel → increase in E/N → acceleration of ionization processes. However, this mechanism is influenced by species accumulated due to previous TS pulses at higher TS repetition frequencies. Sensitivity analysis focused on major electron loss and production processes indicates an important role of the amount of O 2 dissociated by the previous pulses. A lower density of O 2 means a lower rate of electron attachment, while accumulated atomic oxygen atoms lead to acceleration of electron detachment processes. Index Terms-Breakdown, kinetic model, transient spark (TS).

In the framework of the H2020 SERENDI‐PV project, it is aspired to tackle challenges in photovoltaic (PV) modeling and yield simulations, that are emerging today, on four interrelated aspects: i) improved modeling of loss/degradation mechanisms, ii) improved modeling of bifacial PV, floating PV, and building integrated photovoltaics systems, iii) solar resource and uncertainties modeling, and iv) financial risks modeling. As groundwork for this effort, a comprehensive 8‐month study is carried out, the results of which are presented in this article. The study has two parts and main objectives: i) a comprehensive survey addressed to multiple stakeholders, to identify and assess today's “best practices” and needs of the PV industry on PV energy yield simulations; ii) a multi‐model multi‐case benchmarking and evaluation study, i.e., of eight state‐of‐the‐art tools/software for PV energy yield simulations of seven real‐life PV systems addressing diverse “scenarios” (different climates, site characteristics, PV typologies, and technologies).