• Energy Research

Abstract The goal of this project is to determine the reductions in greenhouse gas (GHG) emissions associated with the recycling of aerospace alloys. This study is based on an aerospace recycler that sells much of its high-performance alloy scrap directly to remelters that produce these alloys for aircraft engine component manufacturers, with significant potential environmental benefits arising from the substitution of recycled materials for virgin materials. The project team explored existing sources of environmental data for all of the metals that make up aerospace alloys, and ten common alloys were chosen as case studies. Certain metal elements, including niobium, rhenium, tungsten, and zirconium, did not have any robust environmental impact information, and for these GHG emissions factors from primary production were modeled using a variety of statistical and industrial data sources. The project team then investigated the forms of metal inputs into alloying operations to ensure that the model reflects actual industrial practices and that the alloy scrap substitutes for virgin materials. GHG emissions are also incurred through alloy scrap collection and processing, and so a carbon footprint was performed for alloy recycling operations in order to determine these burdens. Overall, the recycling of aerospace alloys for reuse in the aerospace industry represents significant reductions in GHG emissions for each of the ten alloys considered, while emissions associated with collection and processing are

To supply even a small share of electricity in 2030, several thin-film photovoltaic (PV) technologies, such as CdTe shown here, would require metal production growth rates that exceed those observed historically. In contrast, crystalline silicon could supply a majority electricity share without requiring unprecedented metal growth rates.

Abstract Photovoltaic (PV) module costs have declined rapidly over forty years but the reasons remain elusive. Here we advance a conceptual framework and quantitative method for quantifying the causes of cost changes in a technology, and apply it to PV modules. Our method begins with a cost model that breaks down cost into variables that changed over time. Cost change equations are then derived to quantify each variable's contribution. We distinguish between changes observed in variables of the cost model – which we term low-level mechanisms of cost reduction – and research and development, learning-by-doing, and scale economies, which we refer to as high-level mechanisms. We find that increased module efficiency was the leading low-level cause of cost reduction in 1980–2012, contributing almost 25% of the decline. Government-funded and private R&D was the most important high-level mechanism over this period. After 2001, however, scale economies became a more significant cause of cost reduction, approaching R&D in importance. Policies that stimulate market growth have played a key role in enabling PV's cost reduction, through privately-funded R&D and scale economies, and to a lesser extent learning-by-doing. The method presented here can be adapted to retrospectively or prospectively study many technologies, and performance metrics besides cost.

Technology hardware and deployment processes ('soft technology') seem fundamentally different, but little work examines the nature of this difference and its implications for technology improvement. Here we present a model to study the roles of hardware and soft technology in cost evolution and apply it to solar photovoltaic (PV) systems. Differing properties of hardware and soft technology help explain PV's cost decline. Rapid improvements in hardware affected globally traded components that lowered both hardware and soft costs. Improvements in soft technology occurred more slowly, were not shared as readily across locations and only affected soft costs, ultimately contributing less than previously estimated. As a result, initial differences in soft technology across countries persisted and the share of soft costs rose. In general, we show the usefulness of modelling dependencies between technology costs and features to understand past drivers of cost change and inform future technology development. Hardware and non-hardware features affect the cost of technologies but evolve in different ways over time. Klemun et al. build a model to account for such evolution and analyse the case of photovoltaics.

We present a life cycle assessment of synthetic paraffinic kerosene produced from Jatropha curcas. The feedstock is grown in an intercropping arrangement with pasture grasses so that Jatropha is coproduced with cattle. Additional innovations are introduced including hybrid seeds, detoxification of jatropha seedcake, and cogeneration. Two fuel pathways are examined including a newly developed catalytic decarboxylation process. Sensitivities are examined including higher planting density at the expense of cattle production as well as 50% lower yields. Intercropping with pasture and detoxifying seedcake yield coproducts that are expected to relieve pressure on Brazil's forests and indirectly reduce environmental impacts of biofuel production. Other innovations also reduce impacts. Results of the baseline assessment indicate that innovations would reduce impacts relative to the fossil fuel reference scenario in most categories including 62-75% reduction in greenhouse gas emissions, 64-82% reduction in release of ozone depleting chemicals, 33-52% reduction in smog-forming pollutants, 6-25% reduction in acidification, and 60-72% reduction in use of nonrenewable energy. System expansion, which explicitly accounts for avoided deforestation, results in larger improvements. Results are robust across allocation methodologies, improve with higher planting density, and persist if yield is reduced by half.

Sources of Cost Overrun in Nuclear Power Plant Construction Call for a New Approach to Engineering Design

Summary Nuclear plant costs in the US have repeatedly exceeded projections. Here, we use data covering 5 decades and bottom-up cost modeling to identify the mechanisms behind this divergence. We observe that nth-of-a-kind plants have been more, not less, expensive than first-of-a-kind plants. “Soft” factors external to standardized reactor hardware, such as labor supervision, contributed over half of the cost rise from 1976 to 1987. Relatedly, containment building costs more than doubled from 1976 to 2017, due only in part to safety regulations. Labor productivity in recent plants is up to 13 times lower than industry expectations. Our results point to a gap between expected and realized costs stemming from low resilience to time- and site-dependent construction conditions. Prospective models suggest reducing commodity usage and automating construction to increase resilience. More generally, rethinking engineering design to relate design variables to cost change mechanisms could help deliver real-world cost reductions for technologies with demanding construction requirements.