A vertically aligned carbon nanotube/fiber based electrode for economic hydrogen production by water electrolysis

Electrolysis is the most mature form of hydrogen production. Unfortunately, water electrolysis has not yet achieved the efficiency and the cost levels required for any practical application. In order to enhance the current density, modification of the electrolyte and the electrode morphology are the most popular approaches. Recently there have been numerous reports on how to improve the efficiency of hydrogen production by water splitting [1-3]. On the electrode side, the use of non-platinum high efficiency electrode materials for water splitting will provide a promising future for the hydrogen economy. An ideal electrode for water electrolysis should have good permeability to water and gas. It should also offer good electrical properties with a long life. A porous graphite plate, when coated with titania, for example, is known to provide a simple and economical electrode for water electrolysis [4]. © 2010 IEEE.

The incentives for supply chain collaboration to improve material efficiency in the use of steel: An analysis using input output techniques

In the face of increasing demand and limited emission reduction opportunities, the steel industry will have to look beyond its process emissions to bear its share of emission reduction targets. One option is to improve material efficiency - reducing the amount of metal required to meet services. In this context, the purpose of this paper is to explore why opportunities to improve material efficiency through upstream measures such as yield improvement and lightweighting might remain underexploited by industry. Established input-output techniques are applied to the GTAP 7 multi-regional input-output model to quantify the incentives for companies in key steel-using sectors (such as property developers and automotive companies) to seek opportunities to improve material efficiency in their upstream supply chains under different short-run carbon price scenarios. Because of the underlying assumptions, the incentives are interpreted as overestimates. The principal result of the paper is that these generous estimates of the incentives for material efficiency caused by a carbon price are offset by the disincentives to material efficiency caused by labour taxes. Reliance on a carbon price alone to deliver material efficiency would therefore be misguided and additional policy interventions to support material efficiency should be considered. © 2013 Elsevier B.V.

Use of axially graded burnable boron for hot-spot temperature reduction in a pressurized water reactor core

Shortly after the loading of a pressurized water reactor (PWR) core, the axial power distribution in fresh fuel has already attained the characteristic, almost flat shape, typical of burned fuel. At beginning of cycle (BOC), however, the axial distribution is centrally peaked. In assemblies hosting uniform burnable boron rods, this BOC peaking is even more pronounced. A reduction in the axial peaking is today often achieved by shortening the burnable boron rods by some 30 cm at each edge. It is shown that a two-zone grading of the boron rod leads, in a representative PWR cycle, to a reduction of the hot-spot temperature of approximately 70 °C, compared with the nongraded case. However, with a proper three-zone grading of the boron rod, an additional 20 °C may be cut off the hot-spot temperature. Further, with a slightly skewed application of this three-zone grading, an additional 50 °C may be cut off. The representative PWR cycle studied was cycle 11 of the Indian Point 2 station, with a simplification in the number of fuel types and in the burnup distribution. The analysis was based on a complete three-dimensional burnup calculation. The code system was ELCOS, with BOXER as an assembly code for the generation of burnup-dependent cross sections and SILWER as a three-dimensional core code with thermal-hydraulic feedback.

An integrated representation of the services provided by global water resources

Water is essential not only to maintain the livelihoods of human beings but also to sustain ecosystems. Over the last few decades several global assessments have reviewed current and future uses of water, and have offered potential solutions to a possible water crisis. However, these have tended to focus on water supply rather than on the range of demands for all water services (including those of ecosystems). In this paper, a holistic global view of water resources and the services they provide is presented, using Sankey diagrams as a visualisation tool. These diagrams provide a valuable addition to the spatial maps of other global assessments, as they track the sources, uses, services and sinks of water resources. They facilitate comparison of different water services, and highlight trade-offs amongst them. For example, they reveal how increasing the supply of water resources to one service (crop production) can generate a reduction in provision of other water services (e.g., to ecosystem maintenance). The potential impacts of efficiency improvements in the use of water are also highlighted; for example, reduction in soil evaporation from crop production through better farming practices, or the results of improved treatment and re-use of return flows leading to reduction of delivery to final sinks. This paper also outlines the measures needed to ensure sustainable water resource use and supply for multiple competing services in the future, and emphasises that integrated management of land and water resources is essential to achieve this goal. © 2013 Elsevier Ltd.

A global assessment of manufacturing: Economic development, energy use, carbon emissions, and the potential for energy efficiency and materials recycling

We present in two parts an assessment of global manufacturing. In the first part, we review economic development, pollution, and carbon emissions from a country perspective, tracking the rise of China and other developing countries. The results show not only a rise in the economic fortunes of the newly industrializing nations, but also a significant rise in global pollution, particularly air pollution and CO2 emissions largely from coal use, which alter and even reverse previous global trends. In the second part, we change perspective and quantitatively evaluate two important technical strategies to reduce pollution and carbon emissions: energy efficiency and materials recycling. We subdivide the manufacturing sector on the basis of the five major subsectors that dominate energy use and carbon emissions: (a) iron and steel, (b) cement, (c) plastics, (d) paper, and (e) aluminum. The analysis identifies technical constraints on these strategies, but by combined and aggressive action, industry should be able to balance increases in demand with these technical improvements. The result would be high but relatively flat energy use and carbon emissions. The review closes by demonstrating the consequences of extrapolating trends in production and carbon emissions and suggesting two options for further environmental improvements, materials efficiency, and demand reduction. © 2013 by Annual Reviews. All rights reserved.