Technological learning in bioenergy systems

The main goal of this article is to determine whether cost reductions in different bioenergy systems can be quantified using the experience curve approach, and how specific issues (arising from the complexity of biomass energy systems) can be addressed. This is pursued by case studies on biofuelled combined heat and power (CHP) plants in Sweden, global development of fluidized bed boilers and Danish biogas plants. As secondary goal, the aim is to identify learning mechanisms behind technology development and cost reduction for the biomass energy systems investigated. The case studies reveal large difficulties to devise empirical experience curves for investment costs of biomass-fuelled power plants. To some extent, this is due to lack of (detailed) data. The main reason, however, are varying plant costs due to differences in scale, fuel type, plant layout, region etc. For fluidized bed boiler plants built on a global level, progress ratios (PRs) for the price of entire plants lies approximately between 90–93% (which is typical for large plant-like technologies). The costs for the boiler section alone was found to decline much faster. The experience curve approach delivers better results, when the production costs of the final energy carrier are analyzed. Electricity from biofuelled CHP-plants yields PRs of 91–92%, i.e. an 8–9% reduction of electricity production costs with each cumulative doubling of electricity production. The experience curve for biogas production displays a PR of 85% from 1984 to the beginning of 1990, and then levels to approximately 100% until 2002. For technologies developed on a local level (e.g. biogas plants), learning-by-using and learning-by-interacting are important learning mechanism, while for CHP plants utilizing fluidized bed boilers, upscaling is probably one of the main mechanisms behind cost reductions.     

RRR-Tocopherols and their Acetates as a Possible Scavenger of Free Radicals Produced in the Skin upon UVA-Exposure – An in vivo Screening Method

RRR-tocopherols currently draw attention as constituent of cosmetic preparations a. o. to prevent damage by over-exposure to sunlight. Because they only absorb part of the UVB and are transparent to UVA, their skin protective activity is supposed to be based on scavenging of reactive intermediates formed by ultraviolet radiation. To investigate this possibility, an in vivo method was developed. This is based on the determination of irreversible binding to epidermal DNA/RNA, proteins and lipids, of reactive intermediates formed by photodecomposition of a xenobiotic in the skin. The results support the conclusion that RRR-tocopherols can indeed scavenge reactive intermediates which are formed upon UV-exposure in the skin. RRR-tocopherol acetates also are active in this respect but only after pretreatment for some days (possibly because enzymatic hydrolysis of these compounds is a prerequisite).     

Reflection contrast microscopy for high resolution detection of (3)H-estradiol in ultrathin sections of human stratum corneum

A single autoradiographical method for light and electron microscopy (LM and EM) is presented. Human skin, containing (3)H-estradiol ((3)H-E2) after an in vitro permeation experiment, was processed via a non-extractive tissue preparation protocol, comprising cryo-fixation, freeze-drying, osmium tetroxide vapor fixation, and Spurr resin embedding. Semithin sections were processed for LM autoradiography, while ultrathin sections were processed both for high-resolution LM and EM autoradiography. The autoradiographs were visualized by bright-field microscopy (BFM), reflection contrast microscopy (RCM), and transmission electron microscopy to evaluate the potentials of RCM visualization in high-resolution LM autoradiography. RCM visualization of ultrathin vs. semithin resin sections showed an improved stratum corneum morphology. Histological staining was superfluous. The localization of (3)H-E2 in human stratum corneum using high-resolution LM autoradiography and RCM was as accurate as with high-resolution EM autoradiography.     

A three-compartment electrolytic cell for anodic oxidation of sulfur dioxide and cathodic production of hydrogen

A three-compartment electrolytic cell with a minimized ohmic resistance avoiding the cathodic reduction of sulfur dioxide was constructed. Since sulfur dioxide penetrates all separators studied, sulfur dioxide migration from anode to cathode compartment is prevented by an additional electrolyte flow through an intermediate compartment. The intermediate compartment is limited by two cation exchanger membranes in order to avoid electrolyte interchange by pressure variations. NEOSEPTA membranes turned out to be stable at sulfuric acid concentrations up to 55 w/o and 90°C. Resistivity is sufficiently low. Graphite felt flow-through electrodes fitted onto the membranes and additional catalysts were used. Other cell materials were impregnated graphite, PVDF and copper. The cell voltage was 455, 565, 665, 770, 880 mV at 100, 200, 300, 400, 500 mA cm^?2, respectively, with 50 w/o sulfuric acid at 88°C.