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This paper addresses long-term historical changes in solar irradiance in West Africa (3 to 20° N and 20° W to 16° E) and the implications for photovoltaic systems. Here, we use satellite irradiance (Surface Solar Radiation Data Set – Heliosat, Edition 2.1 – SARAH-2.1) and temperature data from a reanalysis (ERA5) to derive photovoltaic yields. Based on 35 years of data (1983–2017), the temporal and regional variability as well as long-term trends in global and direct horizontal irradiance are analyzed. Furthermore, a detailed time series analysis is undertaken at four locations. According to the high spatial resolution SARAH-2.1 data record (0.05°×0.05°), solar irradiance is largest (up to a 300 W m−2 daily average) in the Sahara and the Sahel zone with a positive trend (up to 5 W m−2 per decade) and a lower temporal variability (<75 W m−2 between 1983 and 2017 for daily averages). In contrast, the solar irradiance is lower in southern West Africa (between 200 W m−2 and 250 W m−2) with a negative trend (up to −5 W m−2 per decade) and a higher temporal variability (up to 150 W m−2). The positive trend in the north is mostly connected to the dry season, whereas the negative trend in the south occurs during the wet season. Both trends show 95 % significance. Photovoltaic (PV) yields show a strong meridional gradient with the lowest values of around 4 kWh kWp−1 in southern West Africa and values of more than 5.5 kWh kWp−1 in the Sahara and Sahel zone.
This dataset contains data from two measurement campaigns in autumn 2018 and summer 2019 that were part of the BMWi project "MetPVNet", and serve as a supplement to the paper "Dynamic model of photovoltaic module temperature as a function of atmospheric conditions", published in the special edition of "Advances in Science and Research", the proceedings of the 19th EMS Annual Meeting: European Conference for Applied Meteorology and Climatology 2019.
Data are resampled to one minute, and include:
PV module temperature
Ambient temperature
Plane-of-array irradiance
Windspeed
Atmospheric thermal emission
The data were used for the dynamic temperature model, as presented in the paper
Long-term variability of solar irradiance and its implications for photovoltaic power in West Africa
(2020)
West Africa is one of the least developed regions in the world regarding the energy availability and energy security. Located close to the equator West Africa receives high amounts of global horizontal irradiance (GHI). Thus, solar power and especially photovoltaic (PV) systems seem to be a promising solution to provide electricity with low environmental impact. To plan and to dimension a PV power system climatological data for global horizontal irradiance (GHI) and its variability need to be taken into account. However, ground based measurements of irradiances are not available continuously and cover only a few discrete locations.
For a sustainable development the electricity sector needs to be decarbonized. In 2017 only 54% of the West African households had access to the electrical grid. Thus, renewable sources should play a major role for the development of the power sector in West Africa. Above all, solar power shows highest potential of renewable energy sources. However, it is highly variable, depending on the atmospheric conditions. This study addresses the challenges for a solar based power system in West Africa by analyzing the atmospheric variability of solar power. For this purpose, two aspects are investigated. In the first part, the daily power reduction due to atmospheric aerosols is quantified for different solar power technologies. Meteorological data at six ground-based stations is used to model photovoltaic and parabolic trough power during all mostly clear-sky days in 2006. A radiative transfer model is combined with solar power model. The results show, that the reduction due to aerosols can be up to 79% for photovoltaic and up to 100% for parabolic trough power plants during a major dust outbreak. Frequent dust outbreaks occurring in West Africa would cause frequent blackouts if sufficient storage capacities are not available. On average, aerosols reduce the daily power yields by 13% to 22% for photovoltaic and by 22% to 37% for parabolic troughs. For the second part, long-term atmospheric variability and trends of solar irradiance are analyzed and their impact on photovoltaic yields is examined for West Africa. Based on a 35-year satellite data record (1983 - 2017) the temporal and spatial variability and general trend are depicted for global and direct horizontal irradiances. Furthermore, photovoltaic yields are calculated on a daily basis. They show a strong meridional gradient with highest values of 5 kWh/kWp in the Sahara and Sahel zone and lowest values in southern West Africa (around 4 kWh/kWp). Thereby, the temporal variability is highest in southern West Africa (up to around 18%) and lowest in the Sahara (around 4.5%). This implies the need of a North-South grid development, to feed the increasing demand on the highly populated coast by solar power from the northern parts of West Africa. Additionally, global irradiances show a long-term positive trend (up to +5 W/m²/decade) in the Sahara and a negative trend (up to -5 W/m²/decade) in southern West Africa. If this trend is continuing, the spatial differences in solar power potential will increase in the future. This thesis provides a better understanding of the impact of atmospheric variability on solar power in a challenging environment like West Africa, characterized by the strong influence of the African monsoon. Thereby, the importance of aerosols is pointed out. Furthermore, long-term changes of irradiance are characterized concerning their implications for photovoltaic power.
Im Projekt wurden die Nachhaltigkeitspotentiale partizipativer landwirtschaftlicher Produktionskonzepte exemplarisch untersucht und der Versuch gemacht, deren Zufriedenheitspotential für Erzeuger und Bürger zu erfassen. Die landwirtschaftlichen Betriebe konnten dabei auf der Grundlage der Leitlinien der Sustainability Assessment of Food and Agriculture (SAFA) in den Dimensionen gute Unternehmensführung, ökologische Integrität, ökonomische Resilienz und soziales Wohlergehen bewertet werden. Die einzelnen Ergebnisse sind nach Dimensionen und korrespondierenden Indikatoren in diesem Working Paper beschrieben. Zudem konnten Handlungsempfehlungen auch dazu erarbeitet werden, wie Untersuchungen anhand der SAFA-Leitlinien erfolgreich durchgeführt werden können.
Das Forschungsprojekt beruht auf zwei Elementen: Die erste Untersuchung, ein Verhaltensexperiment mit 35 Studierenden der Hochschule Bonn-Rhein-Sieg, erforschte den Einfluss von Gruppengröße (Zuschauereffekt) und dargebotenen Informationen zu Verantwortungsdiffusion (Priming) auf nachhaltiges Verhalten. Mithilfe eines zweiten Online-Experiments folgte eine Erhebung zum Einfluss von wahrgenommener persönlicher Bedrohung auf die Bereitschaft zu nachhaltigem Verhalten (N = 72). Die Ergebnisse des ersten Experimentes zeigen einen schwachen, statistisch nicht signifikanten Einfluss der Gruppengröße sowie einen, z.T. statistisch signifikanten, Einfluss der dargebotenen Informationen zu Verantwortungsdiffusion auf das gemessene nachhaltige Verhalten. Bequemlichkeit sowie monetärer Aufwand stellen mit Abstand die größten Hindernisse für nachhaltiges Verhalten dar, während die Beeinflussung durch andere und das Ziel des Umweltschutzes als positive Argumente für nachhaltiges Verhalten genannt wurden. In der Folgestudie konnte ein statistisch signifikanter kausaler Zusammenhang zwischen der wahrgenommenen persönlichen Bedrohung durch die aktuelle Umwelt- und Klimasituation und der Bereitschaft zu nachhaltigem Verhalten nachgewiesen werden. Alle Resultate zu Verhaltensintentionen zeigten insgesamt eine hohe Bereitschaft der Probanden zu nachhaltigem Verhalten.
Incoming solar radiation is an important driver of our climate and weather. Several studies (see for instance Frank et al. 2018) have revealed discrepancies between ground-based irradiance measurements and the predictions of regional weather models. In the realm of electricity generation, accurate forecasts of solar photovoltaic (PV)energy yield are becoming indispensable for cost-effective grid operation: in Germany there are 1.6 million PVsystems installed, with a nominal power of 46 GW (Bundesverband Solarwirtschaft 2019). The proliferation of PV systems provides a unique opportunity to characterise global irradiance with unprecedented spatiotemporalresolution, which in turn will allow for highly resolved PV power forecasts.
Atmospheric aerosols affect the power production of solar energy systems. Their impact depends on both the atmospheric conditions and the solar technology employed. By being a region with a lack in power production and prone to high solar insolation, West Africa shows high potential for the application of solar power systems. However, dust outbreaks, containing high aerosol loads, occur especially in the Sahel, located between the Saharan desert in the north and the Sudanian Savanna in the south. They might affect the whole region for several days with significant effects on power generation. This study investigates the impact of atmospheric aerosols on solar energy production for the example year 2006 making use of six well instrumented sites in West Africa. Two different solar power technologies, a photovoltaic (PV) and a parabolic through (PT) power plant, are considered. The daily reduction of solar power due to aerosols is determined over mostly clear-sky days in 2006 with a model chain combining radiative transfer and technology specific power generation. For mostly clear days the local daily reduction of PV power (at alternating current) (PVAC) and PT power (PTP) due to the presence of aerosols lies between 13 % and 22 % and between 22 % and 37 %, respectively. In March 2006 a major dust outbreak occurred, which serves as an example to investigate the impact of an aerosol extreme event on solar power. During the dust outbreak, daily reduction of PVAC and PTP of up to 79 % and 100 % occur with a mean reduction of 20 % to 40 % for PVAC and of 32 % to 71 % for PTP during the 12 days of the event.
Erfassung der N-Dynamik verschiedener Wirtschaftsdünger in Wintergerste und Senf im Dürrejahr 2018
(2019)
Due to the policy goals for sustainable energy production, renewable energy plants such as photovoltaics are increasingly in use. The energy production from solar radiation depends strongly on atmospheric conditions. As the weather mostly changes, electrical power generation fluctuates, making technical planning and control of power grids to a complex problem.
Renewable energies play an increasingly important role for energy production in Europe. Unlike coal or gas powerplants, solar energy production is highly variable in space and time. This is due to the strong variability of cloudsand their influence on the surface solar irradiance. Especially in regions with large contribution from photovoltaicpower production, the intermittent energy feed-in to the power grid can be a risk for grid stability. Therefore goodforecasts of temporal and spatial variability of surface irradiance are necessary to be able to properly regulate thepower supply.
Background & Objective: Due to the policy goals for sustainable energy production, renewable energy plants such as photovoltaics are increasingly in use. The energy production from solar radiation depends strongly on atmospheric conditions. As the weather mostly changes, electrical power generation fluctuates, making technical planning and control of power grids to a complex problem. Due to used materials (semiconductors e.g. silicon, gallium arsenide, cadmium telluride) the photovoltaic cells are spectrally selective. It means that only radiation of certain wavelengths converts into electrical energy. A material property called spectral response characterizes a certain degree of conversion of solar radiation into the electric current for each wavelength of solar light.
In January 2015, German retail and industry jointly started a sector-wide initiative ("Initiative Tierwohl" - ITW) to improve animal welfare standards. The principle of the ITW is communicated mostly via the websites of ITW and its participating companies. However, uncertainty remained whether or not these websites provide the necessary information consumers need on the ITW products. Based on Schwartz's basic human values, different types of consumers were identified by a cluster analysis (ward-method, k-means). The results showed that depending on expressed meta‐values (Self-Transcendence/Openness to Change Self-Enhancement or Conservation), respondents had different specific information sources and needs. Online sources were rarely mentioned, the majority of consumers referred to brochures, flyers and interpersonal contacts.
Zur Milderung des Klimawandels sind Maßnahmen zur Förderung von Energieeinsparungen notwendig. Energiespartipps informieren über energiesparende Verhaltensweisen und Produkte. Zur Formulierung wirkungsvoller Energiespartipps untersucht die Arbeit, welchen Einfluss Ergänzungen von CO2-Angaben und Formulierungen der Konsequenzen auf die wahrgenommene Informationsqualität, Nützlichkeit und Verhaltensabsicht haben. Außerdem wird untersucht, ob es diesbezüglich Unterschiede zwischen verhaltens- und investitionsorientierten Tipps gibt. Dazu wurde ein Onlineexperiment (N = 352) im 4 x 4 x 2 Design mit den vierstufigen Zwischensubjektfaktoren Framing der Währung (alleinige CO2-Angabe, Jahresvergleichswert, äquivalente Fahrstrecke, äquivalente Laptopnutzung) und Framing der Konsequenz (erreichte Einsparung, vermiedener Ausstoß, entgangene Einsparung, verursachter Ausstoß) sowie der Art des Energiespartipps (verhaltens- vs. investitionsorientiert) als zweistufigen Innersubjektfaktor konzipiert. Varianzanalysen ergaben, dass der verhaltensorientierte Tipp positiver als der investitionsorientierte Tipp bewertet wurde und verhaltensnahe Ergänzungen die Nützlichkeit von CO2-Angaben sowie die Verhaltensintention erhöhen. Das Framing der Konsequenz hatte keinen Effekt. Die Ergebnisse zeigen die Relevanz, zwischen verhaltens- und investitionsorientierten Energiespartipps zu differenzieren und verhaltensnahe Ergänzungen von CO2-Angaben in Kilogramm zu berücksichtigen.
Ein Prüf- und Zertifizierungsstandard zur gesellschaftlichen Verantwortung von Organisationen
(2019)
Nach einem breiten Konsens in Gesellschaft, Politik und Wissenschaft lässt sich die gegenwärtige Art zu wirtschaften so nicht fortsetzen. Ein weltweit gültiger Zertifizierungsstandard, der einen einheitlichen und politisch neutralen Ordnungsrahmen zur gesellschaftlichen Verantwortung von Organisationen gegenüber Mensch und Natur zum Ziel hat, kann helfen, die sich dynamisch verändernden und jeweils notwendigen Anforderungen zu messen, deren Einhaltung (auch komparativ) nachzuweisen und ggf. notwendige Korrekturen zu definieren. Die internationale Norm DIN EN ISO/IEC 26000:2010 bietet einen grundsätzlich geeigneten Orientierungsrahmen zu gesellschaftlich verantwortlichem Handeln für Organisationen.