The Expected Perimeter in Eden and Related Growth Processes

Following Richardson and using results of Kesten on First-passage percolation, we obtain an upper bound on the expected perimeter in an Eden Growth Process. Using results of the author from a problem in Statistical Mechanics, we show that the average perimeter of the lattice animals resulting from a very natural family of "growth histories" does not obey a similar bound.Comment: 11 page

Catalytic Reforming of Higher Hydrocarbon Fuels to Hydrogen: Process Investigations with Regard to Auxiliary Power Units

This thesis discusses the investigation of the catalytic partial oxidation on rhodium-coated honeycomb catalysts with respect to the conversion of a model surrogate fuel and commercial diesel fuel into hydrogen for the use in auxiliary power units. Furthermore, the influence of simulated tail-gas recycling was investigated

Aviation fuel production pathways from lignocellulosic biomass via alcohol intermediates – A technical analysis

In order to achieve the goal of limiting global warming to 1.5 ◦C, also the growing aviation industry needs to take measures to reduce their greenhouse gas emissions. Various renewably sourced aviation fuels can significantly reduce greenhouse gas emissions and most of them, except for example liquid hydrogen or LNG, can be used in the existing infrastructure without airport or aircraft modifications. As most of these renewably sourced fuel types are not (yet) produced at commercial scale, many technological assessment parameter (e.g. carbon or energy efficiency) are uncertain. Thus, the goal of this study is to compare two different process routes, both being based on biochemical and thermochemical conversion steps. The processes evaluated against conversion efficiency of the available raw feedstock and process energy requirements. The evaluation uses theoretical and biochemical carbon efficiency as well as energy efficiency as indicators. A steady-state flowsheet simulation for two biogenic process paths via biogas and bioethanol as intermediate products is carried out on the basis of literature data. In addition, the optional use of solid residue from the biotechnological process step by combustion for direct heat supply cases are studied. In the ethanol-based route, about 23% of the carbon in the feed can be recovered as kerosene, whereas this is only about 19% in the biogas route. Simultaneously, the ethanolbased route without the combustion of the residue has an energy efficiency of 28%, while the biogas route has an efficiency of 24%.Funded by the European Union, th BIOCTANE project received EU funding from the European Climate, Infrastructure and Environment Executive Agency (under the Grant No 101084336)

Farm systems assessment of bioenergy feedstock production: Integrating bio-economic models and life cycle analysis approaches

Climate change and energy security concerns have driven the development of policies that encourage bioenergy production. Meeting EU targets for the consumption of transport fuels from bioenergy by 2020 will require a large increase in the production of bioenergy feedstock. Initially an increase in ‘first generation’ biofuels was observed, however ‘food competition’ concerns have generated interest in second generation biofuels (SGBs). These SGBs can be produced from co-products (e.g. cereal straw) or energy crops (e.g. miscanthus), with the former largely negating food competition concerns. In order to assess the sustainability of feedstock supply for SGBs, the financial, environmental and energy costs and benefits of the farm system must be quantified. Previous research has captured financial costs and benefits through linear programming (LP) approaches, whilst environmental and energy metrics have been largely been undertaken within life cycle analysis (LCA) frameworks. Assessing aspects of the financial, environmental and energy sustainability of supplying co-product second generation biofuel (CPSGB) feedstocks at the farm level requires a framework that permits the trade-offs between these objectives to be quantified and understood. The development of a modelling framework for Managing Energy and Emissions Trade-Offs in Agriculture (MEETA Model) that combines bio-economic process modelling and LCA is presented together with input data parameters obtained from literature and industry sources. The MEETA model quantifies arable farm inputs and outputs in terms of financial, energy and emissions results. The model explicitly captures fertiliser: crop-yield relationships, plus the incorporation of straw or removal for sale, with associated nutrient impacts of incorporation/removal on the following crop in the rotation. Key results of crop-mix, machinery use, greenhouse gas (GHG) emissions per kg of crop product and energy use per hectare are in line with previous research and industry survey findings. Results show that the gross margin – energy trade-off is £36 GJ−1, representing the gross margin forgone by maximising net farm energy cf. maximising farm gross margin. The gross margin–GHG emission trade-off is £0.15 kg−1 CO2 eq, representing the gross margin forgone per kg of CO2 eq reduced when GHG emissions are minimised cf. maximising farm gross margin. The energy–GHG emission trade-off is 0.03 GJ kg−1 CO2 eq quantifying the reduction in net energy from the farm system per kg of CO2 eq reduced when minimising GHG emissions cf. maximising net farm energy. When both farm gross margin and net farm energy are maximised all the cereal straw is baled for sale. Sensitivity analysis of the model in relation to different prices of cereal straw shows that it becomes financially optimal to incorporate wheat straw at price of £11 t−1 for this co-product. Local market conditions for straw and farmer attitudes towards incorporation or sale of straw will impact on the straw price at which farmers will supply this potential bioenergy feedstock and represent important areas for future research

Renewables within the German Electricity System - Experiences and Needs

During the last two decades renewable sources of energy as an environmentally friendly alternative to fossil fuel energy have gained more and more importance within the German electricity system. Their share has increased from less than 4 % to roughly one third of the gross electricity production in the last 25 years. Against this background, the goal of this paper is to present briefly the current status of the use of renewables within the German electricity system, to assess selected developments taking place during this development process as well as to identify given challenges and needs as well as necessary actions to pave the road for a further use of renewable sources of energy within the German electricity provision system. The political driver for the latter is the overarching goal to reduce Greenhouse Gas (GHG) emissions which has been confirmed within the Paris agreement signed by the end of 2015

Greenhouse gas emissions and energy use in UK-grown short-day strawberry (Fragaria xananassa Duch) crops

Original article can be found at: http://journals.cambridge.org/ Copyright Cambridge University PressReducing greenhouse gas emissions and optimizing energy consumption are important for mitigating climate change and improving resource use efficiency. Strawberry (Fragaria xananassa Duch) crops are a key component of the UK soft fruit sector and potentially resource-intensive crops. This is the first study to undertake a detailed environmental impact assessment of all methods of UK strawberry production. A total of 14 systems with six additional sub-systems grown for between 1 and 3 years were identified. They were defined by the growing of short-day (Junebearer) or everbearer varieties, organic production, covering with polytunnels or grown in the open, soil-grown (with or without fumigation) or container-grown (with peat or coir substrate) and summer or spring planted. Pre-harvest, the global warming potential varied between 1·5 and 10·3 t CO2 equiv/ha/crop or 0·13 and 1·14 t CO2 equiv/t of class 1 fruit. Key factors included the use of tunnels, mulch and irrigation, sterilization of soil with fumigants and the use of peat substrate. Seasonal crops without covers grown where rotation of sufficient length reduced Verticillium (system 4) were the most efficient. System 4a (that did not use mulch) emitted 0·13 t CO2 equiv/t of class 1 fruit. A second or third cropping year in soil-grown systems prolonged the effect of mulch and soil fumigants. Greenhouse gases from system 4 (with mulch) averaged 0·30 t CO2 equiv/t of class 1 fruit after 3 years of cropping compared to 0·63 and 0·36 t CO2 equiv/t after 1 and 2 years, respectively.Peer reviewe

Modelling Effects of Agricultural Policies on Regional Greenhouse Gas Emissions From Cattle Raising Production Systems in Baden-Württemberg (Southwest Germany)

In the light of the anthropogenic climate change and the resulting need to mitigate greenhouse gas (GHG) emissions, policies are needed which efficiently abate GHG emissions in the agricultural sector. However, reliable estimates of regional GHG abatement potentials in the agricultural sector are rare because the models do not integrate the economic and environmental effects of different agricultural policies and are generally restricted to a single-gas approach. Coupling an economic sector model with a process-oriented ecosystem model can overcome this gap and thus provide realistic exante information of socioeconomically and environmentally sustainable agricultural policies

Einsatz künstlicher neuronaler Netze bei der kurzfristigen Lastprognose

Um die erweiterten Möglichkeiten des Stromhandels, die sich durch die geplante Liberalisierung des Strommarktes ergeben, optimal nutzen zu können, muß die Planung zur Deckung der Stromnachfrage in Energieversorgungs- und anderen Unternehmen auf einer verläßlichen Lastprognose beruhen. Künstliche neuronale Netze, über deren Möglichkeiten bei der Lastprognose ein kurzer Überblick gegeben wird, weisen in diesem Zusammenhang, u. a. gegenüber der klassischen multiplen Regression, Vorteile auf. Anhand typischer Merkmale werden die Lastprognosesysteme mit künstlichen neuronalen Netzen, die teilweise bereits mit Erfolg eingesetzt werden, kurz charakterisiert. Darüber hinaus werden noch vorhandene Probleme im Umgang mit dieser Methode aufgezeigt, die vor allem darin bestehen, daß die Entwicklung solcher Systeme bisher weitgehend auf Versuch und Irrtum basiert. Daher wird abschließend eine entsprechende Entwicklungsmethodik vorgestellt und diskutiert, die zwar im Detail noch auszugestalten ist, auf die aber für eine breite wirtschaftliche Anwendung individuell angepaßter Systeme nicht verzichtet werden kann

Leistungseffekte einer Stromerzeugung aus Windkraft und Solarstrahlung

Derzeit wird in einer Reihe von Pilot- und Demonstrationsprojekten die Nutzung erneuerbarer Energieträger vor allem für die Gewinnung von elektrischer Energie untersucht. Damit wird zunehmend auch die Frage nach dem Anteil, den diese Energiegewinnungsoptionen zur »gesicherten Leistung« des Kraftwerksparks beitragen könnten, technisch und ökonomisch relevant. Die Verfasser erläutern verschiedene Ansätze zur Bestimmung des Leistungseffektes einer Stromerzeugung aus Windkraft und Solarstrahlung und stellen die zugrunde liegenden Vorgehehensweisen unter den Gegebenheiten in Baden-Württemberg einander vergleichend gegenüber