Fundamental Limits on Wavelength, Efficiency and Yield of the Charge Separation Triad

In an attempt to optimize a high yield, high efficiency artificial photosynthetic protein we have discovered unique energy and spatial architecture limits which apply to all light-activated photosynthetic systems. We have generated an analytical solution for the time behavior of the core three cofactor charge separation element in photosynthesis, the photosynthetic cofactor triad, and explored the functional consequences of its makeup including its architecture, the reduction potentials of its components, and the absorption energy of the light absorbing primary-donor cofactor. Our primary findings are two: First, that a high efficiency, high yield triad will have an absorption frequency more than twice the reorganization energy of the first electron transfer, and second, that the relative distance of the acceptor and the donor from the primary-donor plays an important role in determining the yields, with the highest efficiency, highest yield architecture having the light absorbing cofactor closest to the acceptor. Surprisingly, despite the increased complexity found in natural solar energy conversion proteins, we find that the construction of this central triad in natural systems matches these predictions. Our analysis thus not only suggests explanations for some aspects of the makeup of natural photosynthetic systems, it also provides specific design criteria necessary to create high efficiency, high yield artificial protein-based triads

Injection rate analysis of a modern diesel injection system using straight vegetable oils as fuel

Abstract It is a matter of common knowledge, that rural produced straight vegetable oils can be an alternative fuel to fossil diesel and contribute to an effective reduction of greenhouse gas emissions. Beside the use of rapeseed oil for powering a diesel engine, there is also a great interest in jatropha oil with its comparable physical properties. In this case, the following work opposes the injection rate characteristics of the mentioned oils and fossil diesel, using a modern common rail diesel injection system, providing rail pressures up to 1600 bar. To analyze the injection rate, Moehwald´s injection rate analyzer HDA is used. Furthermore a preheating system is adapted at the test bench, to adjust different temperatures to the fuel downstream the high pressure pump. The high pressure parts of the system (high pressure lines, rail and injector) are also temperature-controlled, using an electrical heating unit. Finally the piezo actuated injector contains three temperature measuring points that allow a determination of the injection rate depending on a defined reference temperature. First of all, the mechanisms during the injector opening process were examined. By using fossil diesel, this process is less dependent on the fuel temperature according to the negligible viscosity variation in the interesting temperature range. Fueling with straight rapeseed or jatropha oil entails a considerable variation of opening delay time with declining fuel temperatures down to the possibility of non-opening. Measurements throughout a warm up cycle also show the possibility of changing the injector's dynamic regime with increasing fuel temperature. These effects were examined with regard to injected mass, opening and closing delay time. Finally a meaningful measuring location at the injector was found, that represents fuel temperature in a sufficient way. Thereby a measuring technique was defined to determine the injection parameters according to this reference temperature. Derived from that, the opening and closing mechanisms of the injector can be investigated to find new ways for the application of plant oil fueled engines

New completely renewable biofuels: Formulations and engine tests on an unmodified up-to-date diesel engine

New completely green biofuels with rapeseed oil as the main component were formulated. They not only fulfil the principles of green chem. and thus do not contain any environmentally harmful additives, but also match the currently valid stds. for biodiesel regarding their physicochem. properties. Using a vegetable oil as a fuel component, its major drawbacks, high kinematic viscosity and high f.p., had to be fixed. It could be shown that the properties of mixts. of rapeseed oil with and without its corresponding fatty acid Me ester, so-​called biodiesel, can be adjusted by several further components. For this purpose, different furan derivs. and terpenes could be used to fulfil the American and European viscosity stds. for biodiesel. The furan derivs. stem from sugar and cellulose, whereas terpenes are mainly constituents of essential oils of trees and the peels of citrus plants as well as producible by the bio-​transformation of sugarcane. With furan derivs. as further fuel components, the amt. of necessary biodiesel could be drastically reduced, and cloud points below -​20 °C were obtained. Using terpenes, these conditions could be matched without any biodiesel in the formulations, and cloud points even below -​40 °C were achieved. To further characterize these biofuel formulations, ignition, combustion and emission tests were performed on an up-​to-​date 2.2 L diesel engine using a blend of rapeseed oil, rapeseed oil-​based biodiesel and 2-​methylfuran. The results showed that the properties of the formulated biofuel were similar to or even better than those of common diesel despite the high requirement profile of modern diesel formulations. Besides improving the relevant physicochem. parameters of the fuel, 2-​methylfuran also increased its oxygen content. This enhanced the soot oxidn. and therefore led to a complete inhibition of soot emissions. Nevertheless, the main drawback of biofuels in general, slightly higher NOx emissions than diesel, still remained, which requires a common exhaust gas aftertreatment of diesel engines. In the scope of this paper, the new formulations are discussed with regard to the concept of green and sustainable chem

Optimising the biodiesel production process: Implementation of glycerol derivatives into biofuel formulations and their potential to form hydrofuels

A new biofuel concept is developed, enabling the usage of vegetable oils and glycerol derivatives in mixtures with biodiesel. This concept significantly enhances the biodiesel production's profitability and thus strongly contributes to the sustainability of future biofuels. After simple addition reactions with building block chemicals, less hydrophilic glycerol derivatives are obtained, which are compatible with biofuels. Even more, the products of the reactions of glycerol with acetone or butyric acid, referred to as solketal and tributyrin, respectively, lead to promising biofuels in mixtures with rapeseed oil and its biodiesel. Due to their low freezing points, they act as cloud and freezing point depressants, when added to vegetable oil/biodiesel blends. Further, since their viscosity is close to common biodiesel, biofuels containing high amounts of vegetable oil and even more glycerol derivatives than they arise during the biodiesel production can be obtained. Thus, this new class of biofuels enables adaptable compositions depending on the application and also the usage as drop-in fuel without any or just few percent of further additives. After optimising the formulations, ignition delay, exhaust gas recirculation, fuel consumption and combustion process measurements were performed in an unmodified upto-date diesel engine. The experiments showed that the properties of the formulated biofuels are either similar to or even better than diesel. The hydrotropy of the glycerol derivatives in these mixtures enables the potential to implement water into biofuels, so-called hydrofuels, reducing nitrogen oxide emissions and leading to further optimised dropin fuels

(A) Orthogonality of the yield, , and the energy storage efficiency, , of QSS formation by the PCT.

<p>For each point, and are set to the values that maximizes within the limits set by and as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036065#pone-0036065-g005" target="_blank">Figure 5</a>. is strongly sensitive to the separation distance, , and is primarily sensitive to . (B) The decrease in the maximal values of with increasing plotted for different values of and . At large values of the optimized yield is primarily dependent on .</p

The evolution of the charge separated state derived in eqn:ct.

<p> is normalized by , which we take to be unity. Rate constants are chosen as , and s. Relevant timescales are labeled on the upper axis and are marked by vertical lines (see eqn:kpm for definitions of ). A central quasi-steadystate (QSS) plateau region is formed when these timescales are well separated. We define the decay time of the QSS, , as the lifetime of the charge separated state. The horizontal line marks the yield, , defined as the value of <i>C</i> in QSS. Analytical expressions for and are derived in Equations 14 and 17, respectively.</p