Christopher Dey

Sunshape distributions for terrestrial solar simulations

Abstract In considering solar concentrating systems, the energy distribution in the focal plane depends, among other things, on the radial distribution (sunshape) of the incident solar energy. Individual sunshapes are created by the small angle forward scattering of sunlight off aerosols in the troposphere, having the effect of transferring some part of the solar energy from within the solar disk to the circumsolar aureole. The ratio of the amount of energy contained in the circumsolar aureole to the total amount of direct energy arriving from the sun, being that from the solar aureole and within the solar disk, is termed the circumsolar ratio (CSR) and is a useful parameter for characterising individual sunshapes. The degree to which the energy distribution in the focal plane of an optical system depends on a characteristic sunshape is usually not well defined, but it is clear that it is non-negligible. Using the Lawrence Berkeley Laboratory’s vast circumsolar database, collected from 11 sites across the United States in the late 1970s and early 1980s, and the recently published sunshapes from the German Aerospace Centre (DLR) correlating three European sites, this paper describes a sunshape model that is independent of geographic location. Further, this paper illustrates that, on average, the circumsolar ratio defines the spatial energy distribution across the solar disk and aureole, and presents an algorithm that can be used to model these distributions for simulating solar concentrating systems.

Using Input‐Output Analysis to Measure the Environmental Pressure of Consumption at Different Spatial Levels

Input‐output modeling is a useful tool for tracing environmental impacts of consumption. Because it includes impacts originating from production layers of infinite order (capturing the entire economy), input‐output modeling is highly relevant for studies operating in a life‐cycle context. In this article we show how the input‐output approach can be used to enumerate the problem of sustainable consumption. Based on a literature survey including research done by the authors we present measures of the emissions of carbon dioxide at different spatial levels: nation, city, and household. Further, we take more environmental effects into account and introduce the concept of environmental efficiency by combining input‐output modeling and data envelopment analysis. Finally, we discuss the policy relevance of the different measures. The article demonstrates that input‐output modeling has a wide range of life‐cycle oriented applications when combined with other data sources such as detailed trade statistics, foreign input‐output and environmental statistics, and household expenditure data.

Environmental impact assessment including indirect effects—a case study using input–output analysis

Abstract Environmental impact assessment (EIA) is a process covered by several international standards, dictating that as many environmental aspects as possible should be identified in a project appraisal. While the ISO 14011 standard stipulates a broad-ranging study, off-site, indirect impacts are not specifically required for an Environmental Impact Statement (EIS). The reasons for this may relate to the perceived difficulty of measuring off-site impacts, or the assumption that these are a relatively insignificant component of the total impact. In this work, we describe a method that uses input–output analysis to calculate the indirect effects of a development proposal in terms of several indicator variables. The results of our case study of a Second Sydney Airport show that the total impacts are considerably higher than the on-site impacts for the indicators land disturbance, greenhouse gas emissions, water use, emissions of NO x and SO 2 , and employment. We conclude that employing input–output analysis enhances conventional EIA, as it allows for national and international effects to be taken into account in the decision-making process.

Truncation error in embodied energy analyses of basic iron and steel products

An input–output study of the energy requirements for the manufacture of basic iron and steel products by the Australian steel industry is presented. The basis of this study is a decomposition of the total energy requirement per mass output of steel into partial requirements from industry sectors supplying the steel industry. A separation into different order requirements shows that lower order energy requirements for basic iron and steel, chosen from the supplying industries identified in a recent process analysis, are 19 MJ/kg, and that the total energy requirement is 40.1 MJ/kg. This proportion demonstrates that truncation error in this process analysis, that is, the omission of higher order energy contributions, is of the order of 50%.

Economic, energy and greenhouse emissions impacts of some consumer choice, technology and government outlay options

Abstract The impacts of selected spending options in the Australian economy are determined in terms of energy consumption, greenhouse gas emissions and a range of economic parameters. Six case studies of one current-practice and one alternative, environmentally motivated spending option are carried out, describing consumer choices, technologies and government outlays. The assessment method is based on input–output theory and, as such, enables both the direct and indirect effects of spending to be quantified. In general, the results indicate that pro-environmental objectives, such as reductions in energy consumption and greenhouse gas emissions, are compatible with broad socio-economic benefits, such as increases in employment and income, and reductions in imports.

Measurement of local heat flow in flat evacuated glazing

A guarded hot-plate apparatus has been developed for measuring the local thermal conductance of flat evacuated glazing. Parasitic heat flows in the apparatus have been reduced to below an equivalent thermal conductance of 0.01 W m2 K1. Techniques are described for determining the separate contributions to heat flow through the sample from pillar conduction, conduction through residual gas, and radiation. The accuracy of the measurement system is estimated to be better than ±2% and the reproducibility for sequential measurements is better than ±0.004 W m2 K1 for a measurement area of approximately 1.7 cm2.

AUSTRALIA'S CARBON FOOTPRINT

This paper gives an overview of the construction techniques and methods used to assign greenhouse gas accounts to industry sectors and of the use of input–output analysis to subsequently calculate the carbon footprint of Australia. The work is motivated by the introduction of an emissions-trading scheme in Australia, and by the need for policy to be developed around the direct and indirect (life-cycle) greenhouse gas emissions of industries, especially with regards to the trade exposure of industries with large carbon footprints. Greenhouse gas multipliers, which show the carbon footprint intensity of consumption items, are calculated to gain insight into opportunities for ‘greening’ consumption. Key industries are identified in relation to both greenhouse gas emissions and economic importance. The effects of imports, exports and capital consumption are explored and a brief analysis of the change in greenhouse gas multipliers over time is given.

The effective size of the solar cone for solar concentrating systems

In this paper we define a virtual solar cone, whose principle axis is aligned with the solar vector, having a radial angular displacement containing a pre-defined proportion of the terrestrial solar radiation. By simulating various sunshape profiles, the angular extent of the energy distribution is established to give the effective size of the solar cone for a range of atmospheric conditions. Then, by simulating the reflection of these solar distributions off a set of non-ideal mirrored surfaces, accounting for non-specular reflection and mirror shape errors, the combined effect of sunshape and mirror properties on the solar image is obtained. Clear trends are presented that show the dependence of the effective size of the solar image on the accuracy of a mirrored surface for different sunshapes. We then identify the effective size of the solar image at the absorber plane that must be accommodated in the design and optimisation of solar concentrating systems.

The measurement and calculation of radiative heat transfer between uncoated and doped tin oxide coated glass surfaces

Abstract Accurate measurements are reported of the radiative heat transfer between parallel surfaces of uncoated and doped tin oxide coated glass. The infrared properties of the tin oxide coated glass are calculated by a novel approach by fitting a three parameter Drude model to reflectance measurements at a specified angle, and over a restricted range of wavelengths. Estimates of the radiative heat transfer between uncoated and coated glass surfaces are calculated from a consideration of the directional spectral emittances and the blackbody spectrum. This procedure gives results that are in more consistent agreement with experimental measurements than results obtained by considering the hemispherical total, or directional total emittances. Copyright

Modelling Interactions Between Economic Activity, Greenhouse Gas Emissions, Biodiversity and Agricultural Production

In this article, we develop a modelling approach which examines selected drivers of ecosystem functioning and agricultural productivity. In particular, we develop linkages between land use and biodiversity and between biodiversity and agricultural productivity. We review the literature for quantitative estimates of key relationships and their parameters for modelling human consumption, land use, energy use, and greenhouse gas emissions on biodiversity and agricultural productivity. We assemble these specifications into an iterative causal model and carry out a number of scenario projections of country-level consumption, production, land use, energy use, greenhouse gas emissions, species diversity, and agricultural production up to 2050. Finally, we dissect the projections into key drivers using structural decomposition and sensitivity analyses.