Accuracy of energy prediction methodologies

In the current market, the specific annual energy yield (kWh/kWp) of a PV system is gaining in importance due to its direct link to the financial returns for possible investors who typically demand an accuracy of 5% in this prediction. This paper focuses on the energy prediction of photovoltaic modules themselves, as there have been significant advances achieved with module technologies which affect the device physics in a way that might force the revisiting of device modelling. The paper reports the results of a round robin based evaluation of European modelling methodologies. The results indicate that the error in predicting energy yield for the same module at different locations was within 5% for most of the methodologies. However, this error increased significantly if the nominal nameplate rating is used in the characterization stage. For similar modules at the same location the uncertainties were much larger due to module-module variations

Analysis of spectral irradiance variation in northern Europe using average photon energy distributions

One major factor affecting the energy yield of photovoltaic modules is the spectral distribution of incident solar radiation. As spectral irradiance data is scarce, this study provides further documentation of recorded spectra at tilt angle 30°– 45°over a period from one to several years, with the resulting distributions of average photon energy (APE) in the 350–1050 nm wavelength range, from five locations in northern Europe. The results show a general trend of higher monthly APE values in summer and lower values in winter, with more pronounced APE variation at increasing latitude. Compared to the reference APE value of 1.88 eV, the largest variation in monthly APE is seen for the northernmost location of Grimstad, Norway, ranging from 1.82 eV to 1.93 eV between January and July with an annual average APE of 1.90 eV. The smallest variation is found for Merklingen, Germany, ranging from 1.86 eV to 1.88 eV between March and July, with an annual average APE of 1.86 eV. Comparing the annual average APE values of the various locations, the study shows a slightly blue-shifted spectrum for Berlin, Enschede and Grimstad, whereas Merklingen experiences a slightly red-shifted spectrum and the APE at Utrecht is similar to the standard reference spectrum. The simulations through SMARTS show air mass, water vapor and aerosols as the major parameters affecting the spectrum. During the winter months, distinct contributions from both clear and cloudy sky conditions result in a bi-modal APE distribution for all locations, which is not observed during the summer months. Analysis of APE demonstrates different site-specific behaviors, even though all sites are categorized in the same Köppen–Geiger (KG) climate class. These differences arise mainly due to atmospheric factors, whereas dissimilarity in albedo conditions, plane of tilt and instrumentation also have some contributions

Photovoltaic performance measurements in Europe: PV-catapult round robin tests

Two sets of modules have been sent around to different testing installations across Europe, one set to laboratories performing indoor calibrations and one set to laboratories performing outdoor power and energy ratings. The results show that for crystalline and polycrystalline devices, a very good agreement between laboratories has been achieved. A lower agreement between laboratories has been achieved for thin film devices and further need for research is identified

Accuracy of Energy Prediction Methodologies

In the current market, the specific annual energy yield (kWh/kWp) of a PV system is gaining in importance due to its direct link to the financial returns for possible investors who typically demand an accuracy of 5% in this prediction. This paper focuses on the energy prediction of photovoltaic modules themselves, as there have been significant advances achieved with module technologies which affect the device physics in a way that might force the revisiting of device modelling. The paper reports the results of a round robin based evaluation of European modelling methodologies. The results indicate that the error in predicting energy yield for the same module at different locations was within 5% for most of the methodologies. However, this error increased significantly if the nominal nameplate rating is used in the characterization stage. For similar modules at the same location the uncertainties were much larger due to module-module variations

Reduktion von ungeplanten Kurzstillständen an einer hochproduktiven Anlage mit Hilfe der TPM-Philosophie

Im Unilever-Werk in Buxtehude werden Abfüll- und Verpackungslinien für Duschbäder und Lotionen betrieben. Anhand einer Gesamtanlagenverfügbarkeits-Ermittlung im Rahmen des TPM-Programms werden Verluste der einzelnen Linien elektronisch erfasst und regelmäßig ausgewertet. Als eine der ältesten Anlagen im Werk hat die zu betreuende Anlage eine relativ schlechte Anlagenverfügbarkeit. Ungeplante Kurzstillstände sind dabei im Vergleich zu anderen Anlagen sehr hoch und liegen deutlich über dem Werksdurchschnitt. Im Rahmen dieser Diplomarbeit geht es um die Ermittlung von Phänomenen, die ungeplante Kurzstillstände verursachen, sowie um die Entwicklung und Umsetzung von Lösungen zur dauerhaften Eliminierung, mit dem Ziel, die Anlage an den Werksdurchschnitt heranzubringen. Zur Ermittlung der Hauptausfälle und größten Verluste erfolgt eine detaillierte Auswertung des Ausfallverhaltens der Anlage mit Hilfe der firmeninternen. Anhand der Auswertung werden verschiedene Aggregate in den Fokus gerückt, an denen vor Ort detaillierte Störungsanalysen durchgeführt werden. Es folgt die Ermittlung von Lösungsansätzen und deren technische Umsetzung. Außerdem wird zur vorbeugenden Reduktion von Stillständen die Einführung neuer Aggregate mitbetreut und die Thematik der Qualitätsprobleme an Flaschen aufgegriffen. In einer abschließenden Auswertung wird der Nutzen der Maßnahmen bewertet