Changes in the Efficiency of Photovoltaic Energy Conversion in Temperature Range with Extreme Limits

The efficiency of the photovoltaic energy conversion depends on the temperature significantly. We monitored the behavior of I-V characteristics of the PV cell based on monocrystalline silicon in temperature range with extreme limits from-170 °C to +100 °C. We have not yet found a similar measurement in this temperature interval. The temperature of PV modules without radiation concentration can reach values of-100 °C to +100 °C on the Earth\u27s surface. The temperature range may be few wider in space. Changes of I-V characteristics and P-V characteristics are discussed in terms of the theory of solids. The open-circuit voltage dependence is approximately linear over a wide temperature range, but saturation occurs at temperatures around-150 °C, which is also explained in accordance with the theory of semiconductors. The decrease in energy conversion efficiency with increasing temperature has a value of about 0.5%/°C throughout the whole temperature range possible on the Earth\u27s surface. If there are large changes in the temperature of the PV modules during operation of the PV system, the electrical voltage of the PV modules will also change considerably. In space applications, these fluctuations may be greater. This must be taken into account when designing PV systems (especially for deep space missions). For example, electronic inverters are sensitive to overvoltage or undervoltage

Reduced real lifetime of PV panels – Economic consequences

The maintenance and analyzing failures of PV systems and plants are becoming more and more important issues. Our data from the long-term operation of 85 photovoltaic power plants in central Europe show that their actual lifetime is about half that of the originally planned lifetime. After about 10 years, serious failures of 1st tier (bankable) PV panels occur at an increasing rate. This article presents selected typical data and describes the most serious failures. Furthermore, economic calculations of returns on investment are carried out in relation to the price of electricity, which is currently changing at a rapid pace. It shows that the PV panel lifetime reduction from 20 to 30 years, declared at commercial leaflets, to real lifetime about 10–12 years can reduce PV power plant profit substantially, but the investment is still worth it. The reason is that after 10–12 years ser vice/maintenance expenses to replace damaged PV panels and inverters are growing very quickly. The new information could be helpful for owners of PV power plants to get a more realistic estimation of profits

Photovoltaics : theory and practice of solar energy utilization

169 p. : col. ill. ; 24 cm

Behavior of Photovoltaic System during Solar Eclipse in Prague

PV power plants have been recently installed in very large scale. So the effects of the solar eclipse are of big importance especially for grid connected photovoltaic (PV) systems. There was a partial solar eclipse in Prague on 20th March 2015. We have evaluated the data from our facility in order to monitor the impact of this natural phenomenon on the behavior of PV system, and these results are presented in the paper. The behavior of PV system corresponds with the theoretical assumption. The power decrease of the PV array corresponds with the relative size of the solar eclipse. I-V characteristics of the PV panel correspond to the theoretical model presented in our previous work

Analysis of Output Signal Distortion of Galvanic Isolation Circuits for Monitoring the Mains Voltage Waveform

Different methods for galvanically isolated monitoring of the mains voltage waveform were evaluated. The aim was to determine the level of distortion of the output signal relative to the input signal and the suitability of each method for calculating active power values. Six fixtures were tested: two voltage transformers, an electronic circuit with a current transformer, a standalone current transformer, a simple circuit with optocouplers, and a circuit with an A/D-D/A converter with capacitive coupling. The input and output waveforms were mathematically analyzed by three methods: (1) calculating the spectral components of waveforms and the relative changes in their THD (total harmonic distortion) values, (2) determining the similarity of waveforms according to the size of the area bounded by the input and output waveform curves, and (3) determining the accuracy of the active power calculation based on the output waveform. The time difference in the zero crossing of the input and output signals was measured, and further calculations for the second and third method were performed on the zero-crossing time shift-corrected waveforms. Other aspects of selecting the appropriate type of monitoring element, such as power consumption or overall circuit complexity, were also evaluated

Polysiloxane gel lamination technology for solar panels and rastered glazing

93 p. : col. ill. ; 24 cm

Distribution Grid Stability—Influence of Inertia Moment of Synchronous Machines

This paper shows the influence of grid frequency oscillations on synchronous machines coupled to masses with large moments of inertia and solves the maximum permissible value of a moment of inertia on the shaft of a synchronous machine in respect to the oscillation of grid frequency. Grid frequency variation causes a load angle to swing on the synchronous machines connected to the grid. This effect is particularly significant in microgrids. This article does not consider the effects of other components of the system, such as the effects of frequency, voltage, and power regulators

Monitoring of Defects of a Photovoltaic Power Plant Using a Drone

Drone infrared camera monitoring of photovoltaic (PV) power plants allows us to quickly see a large area and to find the worst defects in PV panels, namely cracked PV cells with broken contacts. Roofs are suitable for the integration of PV power plants into buildings. The power plant at the Czech University of Life Sciences in Prague, which was monitored by this method, does not show any significant defects, and the produced electric energy exceeds the expected values. On the contrary, the PV power plant in Ladná has visible defects, and the data monitoring system Solarmon-2.0 also indicates defects. Our newly developed data monitoring system Solarmon-2.0 has been successfully used in 65 PV power plants in the Czech Republic and in many PV power plants throughout the world. Data are archived and interpreted in our dispatch area at the Czech University of Life Sciences in Prague. The monitoring system can report possible failure(s) if the measured amount of energy differs from the expected value(s). The relation of the measured values of PV power to the PV panel temperature is justified, which is consistent with the physical theory of semiconductors

New Monitoring System for Photovoltaic Power Plants’ Management

An innovative solar monitoring system has been developed. The system aimed at measuring the main parameters and characteristics of solar plants; collecting, diagnosing and processing data. The system communicates with the inverters, electrometers, metrological equipment and additional components of the photovoltaic arrays. The developed and constructed long working system is built on special data collecting technologies. At the generating plants, a special data logger BBbox is installed. The new monitoring system has been used to follow 65 solar plants in the Czech Republic and elsewhere for 175 MWp. As an example, we have selected 13 PV plants in this paper that are at least seven years old. The monitoring system contributes to quality management of plants, and it also provides data for scientific purposes. Production of electricity in the built PV plants reflects the expected values according to internationally used software PVGIS (version 5) during the previous seven years of operation. A comparison of important system parameters clearly shows the new solutions and benefits of the new Solarmon-2.0 monitoring system. Secured communications will increase data protection. A higher frequency of data saving allows higher accuracy of the mathematical models