Optimisation of hybrid off-grid energy systems by linear programming

Background: In this study, a general model of a hybrid off-grid energy system is developed, which can be adjusted to reflect real conditions in order to achieve economical and ecological optimisation of off-grid energy systems. Methods: Using linear programming methods in the General Algebraic Modeling System (GAMS) environment, the optimal configuration of the electrical power supply system following characteristic restrictions as well as hourly weather and demand data is found. From this model, the optimal mix of solar- and wind-based power generators combined with storage devices and a diesel generator set is formed. Results: The operation of this model was tested in two real off-grid energy systems, a cluster of villages in India and Titumate in Colombia. Both optimisation processes resulted in hybrid energy systems, utilising photovoltaics (PV), lead-acid batteries and a diesel generator as a load-balancing facility. Conclusions: With respect to small off-grid energy systems, it was found that renewable energy in combination with electrical storage devices help to reduce the cost of energy compared to stand-alone diesel generator sets. The optimal solutions strongly depend on the particular load demand curve. As both PV and wind energy benefit from energy storage, the costs of the battery can be shared and the two technologies complement each other. Finally, although the optimised capacity of the diesel generator remains nearly constant, its contribution to the total power generation is being substituted by renewable energy sources, which serve as fuel-saving technologies

Marine Ice: A sleeping iron giant in the Southern Ocean?

The Polar Southern Ocean (PSO) provides an excess amount of macro-nutrients but productivity is largely limited by the availability of essential micro-nutrients, namely iron, manganese, zinc and others. Seasonal patches of increased productivity off major ice shelfs around Antarctica suggest that local sources of these deficient micro-nutrients must be present. With this session contribution we present a new study on marine ice from the Filchner-Ronne Ice Shelf (FRIS) as a potential source of iron and other limiting micro-nutrients for the Atlantic sector of the PSO. Marine ice is formed via partial melting of meteoric shelf ice near the grounding line of large ice shelves (e.g. FRIS). During this process small refrozen ice platelets accumulate in a layer of over 100 m thickness underneath the ice shelf to form marine ice containing high amounts of particulate material. In a project funded by the German Research Foundation (DFG) within the priority program SPP1158, we analyse 2 marine ice cores (B13: 62m, B15: 167m of marine ice) recovered in the 1990’s from the FRIS on their geochemical compositions. The coring location of B13 was about 40 km away from the shelf ice edge and B15 was drilled another 136 km further inland along the reconstructed flow line of B13. Due to shelf ice migration over the last 30 years, their locations have shifted about 30 km towards the shelf ice edge. First results show dissolved Fe (dFe) and Mn (dMn) concentrations ranging between 30 and 300 nMol and particulate Fe (pFe) of 20 to 120 µMol (0.2 to 1.4 µMol for pMn). These concentrations are orders of magnitude higher than the ones currently found in the PSO for those elements. Basal melting and ice-berg calving of marine ice with the accompanied release of these essential trace metals could therefore fuel local productivity in regions with large extent of shelf ice. With our study we aim to evaluate marine ice as potentially overlooked source for limiting micro-nutrients that could explain high productivity areas within an otherwise relatively low productive PSO

Wissensstandsanalyse zu Qualität, Verbraucherschutz und Verarbeitung ökologischer Lebensmittel

Zielsetzung des Projektes war es, den aktuellen Stand des Wissens zur Qualität und Verarbeitung ökologischer Lebensmittel sowie zum Verbraucherschutz aufzuzeigen und zu bewerten. Das Projektteam setzte sich aus Wissenschaftlern des Forschungsinstituts für biologischen Landbau (Deutschland und Schweiz), des Büros für Lebensmittelkunde, des Forschungsrings für Biologisch-Dynamische Wirtschaftsweise e.V. sowie des Fachgebiets Ökologische Lebensmittelqualität und Ernährungskultur der Universität Kassel zusammen. In dem zeitlich sehr begrenzten Projekt fokussierte die Arbeitsgruppe die Betrachtung auf folgende Themenkomplexe und Produktgruppen: Bereich Qualität - Ernährung - Sensorik - Ökospezifische Qualitäten - Authentizität und Rückverfolgbarkeit Bereich Verarbeitung - Rohwaren/Lagerung und Technologien für die Produktgruppen: -- Getreide -- Milch -- Fleisch -- Obst und Gemüse und Erzeugnisse aus diesen - Nachhaltigkeit im Unternehmen und entlang der Prozesskette - Verpackung Vorhandenes Wissen, aktuelle Fragestellungen und Entwicklungsrichtungen wurden nach thematisch angepassten Vorgehensweisen identifiziert und anhand internationaler Literatur und Experteninterviews diskutiert. Zu allen Themenkomplexen wurden kurze und allgemeinverständliche Reports erstellt, die einen schnellen und fundierten Überblick zum aktuellen Stand des Wissens und zu eventuellen Wissenslücken geben. Der Abschlussreport wurde in deutscher und englischer Sprache veröffentlicht. Insgesamt wurde festgestellt, dass in den betrachteten Themenkomplexen erheblicher Bedarf an Forschung und Entwicklung sowie an Wissenstransfer besteht. Neben einer Reihe von Detailfragen sind grundlegende Themen, wie beispielsweise das Anforderungsprofil an eine „ökologische Verarbeitung“, nicht hinreichend erforscht und geklärt. Diese Arbeiten sind jedoch Voraussetzung für die Bearbeitung von Detailthemen, da hier Aufgabenstellungen, Schwerpunktsetzungen und Methoden definiert werden

CO(1-0) in z ≳ 4 Quasar Host Galaxies: No Evidence for Extended Molecular Gas Reservoirs

We present ^(12)CO(J = 1 → 0) observations of the high-redshift quasi-stellar objects (QSOs) BR 1202-0725 (z = 4.69), PSS J2322+1944 (z = 4.12), and APM 08279+5255 (z = 3.91) using the NRAO Green Bank Telescope (GBT) and the MPIfR Effelsberg 100 m telescope. We detect, for the first time, the CO ground-level transition in BR 1202-0725. For PSS J2322+1944 and APM 08279+5255, our observations result in line fluxes that are consistent with previous NRAO Very Large Array (VLA) observations, but they reveal the full line profiles. We report a typical lensing-corrected velocity-integrated intrinsic ^(12)CO(J = 1 → 0) line luminosity of L'_(CO) = 5 × 10^(10) K km s^(-1) pc^2 and a typical total H_2 mass of M(H_2) = 4 × 10^(10) M_☉ for the sources in our sample. The CO/FIR luminosity ratios of these high-z sources follow the same trend as seen for low-z galaxies, leading to a combined solution of log L_(FIR) = (1.39 ± 0.05) log L_(CO) - 1.76. It has previously been suggested that the molecular gas reservoirs in some quasar host galaxies may exhibit luminous, extended ^(12)CO(J = 1 → 0) components that are not observed in the higher J CO transitions. Using the line profiles and the total intensities of our observations and large velocity gradient (LVG) models based on previous results for higher J CO transitions, we derive that emission from all CO transitions is described well by a single gas component in which all molecular gas is concentrated in a compact nuclear region. Thus, our observations and models show no indication of a luminous extended, low surface brightness molecular gas component in any of the high-redshift QSOs in our sample. If such extended components exist, their contribution to the overall luminosity is limited to at most 30%