Search

Partially shaded photovoltaic systems operate with nonuniform conditions within the photovoltaic array, which lead to power losses. Module‐level power electronics can potentially improve the performance of such photovoltaic systems. However, the potential performance increase compared to standard string inverter systems is site specific. To investigate this, power optimizer and string inverter efficiency measurements are conducted in the ZHAW indoor laboratory. With these results, simulations are performed for a module‐level power electronics system with power optimizers at every module and a standard string inverter rooftop photovoltaic system. As a performance comparison, the P370 power optimizer and 3500H inverter are used for the module‐level power electronics system and partial shading by a chimney is considered. For the standard string inverter system, the string inverter SUN2000‐3.68KTL‐L1, without the use of module‐level power electronics, is chosen. The results of the annual simulations show a gain of the module‐level power electronics system between –0.9% and 1.4% (14 modules) or –0.2% and 0.8% (13 modules), depending on the position of the chimney. Furthermore, the shading adaption efficiency, a method of quantifying the annual performance for shading situations by applying weightings to a few indoor measured performance values of power electronic components, is described. [ABSTRACT FROM AUTHOR]

The low-voltage distribution grid in Dettighofen, Germany was analysed regarding load flows and the voltage behaviour because of decentralised photovoltaic (PV) power generation. High load flow fluctuations of 400 kW within 25 min were observed in the more critical western part of the grid. During the night, the average base and the peak load obtained from the medium voltage grid was 55.8 and 150 kW, respectively. On certain days, the transformer (400 kVA) fed with rated power into the medium-voltage grid. The relative voltage rise on the transformer was between 2% and 3%. A critical situation was found at a distribution box with two long stubs and a total PV installation power of 99.3 kWp. The load flows caused a relative voltage rise of 4.5% on a day with clear sky, and there was a voltage peak slightly above 110% on a day with high fluctuating irradiance. In a second step, load flow simulations with NEPLAN were performed to analyse three different voltage reducing measures. The relative voltage rise could be reduced by 3% with an active power curtailment ratio of 70% together with reactive power control (cosφ of 0.95 and cosφ of 0.9 at p > 13.8kW). Peak shifting with battery storage leads to the same reduction if the power that exceeds 40% of the rated PV power is shifted. The average costs of limiting the active power to 70% are 1.45 ct/kWh compared with €3.11/kWh for peak shifting with commercial available lead-acid batteries. This is due to the low number of storage cycles resulting in high costs. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Transport accounts for 31% of Swiss green house gas emissions due to the high degree of oil dependence in transport energy supply. The emissions of transport could be reduced significantly if all the vehicles that ran on fossil fuels would be replaced by electric vehicles powered by photovoltaic solar energy. Compared with other sources of renewable transport energy, photovoltaic generation of electricity has two advantages: it requires little space and can also be applied to built-up areas or transport infrastructure. In this paper, we will examine the potential of parking lots for the photovoltaic generation of solar electricity. The paper is based on simulations that were carried out for 48 parking lots in Frauenfeld, a typical Swiss medium-sized city of 22 665 inhabitants. Covered with solar carports, these parking lots alone would cover 15-40% of the energy demand by the city's road passenger transport. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]