Net primary energy balance of a solar-driven photoelectrochemical water-splitting device

A fundamental requirement for a renewable energy generation technology is that it should produce more energy during its lifetime than is required to manufacture it. In this study we evaluate the primary energy requirements of a prospective renewable energy technology, solar-driven photoelectrochemical (PEC) production of hydrogen from water. Using a life cycle assessment (LCA) methodology, we evaluate the primary energy requirements for upstream raw material preparation and fabrication under a range of assumptions of processes and materials. As the technology is at a very early stage of research and development, the analysis has considerable uncertainties. We consider and analyze three cases that we believe span a relevant range of primary energy requirements: 1550 MJ m(-2) (lower case), 2110 MJ m(-2) (medium case), and 3440 MJ m(-2) (higher case). We then use the medium case primary energy requirement to estimate the net primary energy balance (energy produced minus energy requirement) of the PEC device, which depends on device performance, e. g. longevity and solar-to-hydrogen (STH) efficiency. We consider STH efficiency ranging from 3% to 10% and longevity ranging from 5 to 30 years to assist in setting targets for research, development and future commercialization. For example, if STH efficiency is 3%, the longevity must be at least 8 years to yield a positive net energy. A sensitivity analysis shows that the net energy varies significantly with different assumptions of STH efficiency, longevity and thermo-efficiency of fabrication. Material choices for photoelectrodes or catalysts do not have a large influence on primary energy requirements, though less abundant materials like platinum may be unsuitable for large scale-up

Incorporating Experience Curves in Appliance Standards Analysis

The technical analyses in support of U.S. energy conservation standards for residential appliances and commercial equipment have typically assumed that manufacturing costs and retail prices remain constant during the projected 30-year analysis period. There is, however, considerable evidence that this assumption does not reflect real market prices. Costs and prices generally fall in relation to cumulative production, a phenomenon known as experience and modeled by a fairly robust empirical experience curve. Using price data from the Bureau of Labor Statistics, and shipment data obtained as part of the standards analysis process, we present U.S. experience curves for room air conditioners, clothes dryers, central air conditioners, furnaces, and refrigerators and freezers. These allow us to develop more representative appliance price projections than the assumption-based approach of constant prices. These experience curves were incorporated into recent energy conservation standards for these products. The impact on the national modeling can be significant, often increasing the net present value of potential standard levels in the analysis. In some cases a previously cost-negative potential standard level demonstrates a benefit when incorporating experience. These results imply that past energy conservation standards analyses may have undervalued the economic benefits of potential standard levels

To be Makiran is to see like Mr Parrot: the anthropology of wonder in Solomon Islands

This article lays out a general thesis for the development of a comparative ethnographic approach to the anthropology of wonder. It suggests that wonder is both an index and a mode of challenge to existing ontological premises. Through analytical engagement with the theme of wonder in Western philosophy and the anthropology of ontology, it extends this thesis to include the corollary that different ontological premises give rise to different wonders. Ethnographically, the article supports these claims via analysis of wonder discourses among the Arosi of Solomon Islands. These discourses, it is argued, both respond to and promote ontological transformations in a context where the premises at stake are neither those of the Cartesian dualism commonly ascribed to modernity nor of the relational non-dualism commonly ascribe to anthropology’s ethnographic ‘others’, but of a non-Cartesian pluralism termed poly-ontology

Opportunities for Efficiency Improvements in the U.S. Natural Gas Transmission, Storage and Distribution System

This report provides an in-depth review of the U.S. natural gas transmission, storage and distribution system, from gas gathering at wellheads to final delivery to consumers, with a focus on energy efficiency opportunities. Drawing upon several resources published by the U.S. government and the natural gas industry, as well as handful of research papers and company publications, this report provides an overview of system components, historical and potential future trends, technical efficiency opportunities, cost estimates, and a final synthesis including policy recommendations. While far from comprehensive, a number of general conclusions could be drawn from the available information. First, there are a number of technical efficiency opportunities located throughout the natural gas infrastructure system that have yet to be fully realized. This includes improvements in compressors, prime movers (gas engines/turbines and electric motors), and capacity/operational choices; pipeline sizing, layout, cleaning, and interior coatings; and opportunities for waste heat recovery. However, the natural gas industry is currently constrained to make investment decisions that are increasingly short-term from an economic payback perspective, due to the current prevalence of short-term (<15years) customer contracts and the challenge of full cost recovery in a regulated market. While the industry strives to maximize efficiency in order to reduce the cost of their operations, decisions typically fall short of maximizing thermodynamic efficiency. While the greatest opportunities for efficiency improvement lie in new systems, options do exist for improving the efficiency of existing systems as well. The report concludes that additional policies will likely be required in order to push the industry toward higher efficiency operations; a number of options are raised that warrant further exploration

Estimating Policy-Driven Greenhouse Gas Emissions Trajectories in California: The California Greenhouse Gas Inventory Spreadsheet (GHGIS) Model

A California Greenhouse Gas Inventory Spreadsheet (GHGIS) model was developed to explore the impact of combinations of state policies on state greenhouse gas (GHG) and regional criteria pollutant emissions. The model included representations of all GHG- emitting sectors of the California economy (including those outside the energy sector, such as high global warming potential gases, waste treatment, agriculture and forestry) in varying degrees of detail, and was carefully calibrated using available data and projections from multiple state agencies and other sources. Starting from basic drivers such as population, numbers of households, gross state product, numbers of vehicles, etc., the model calculated energy demands by type (various types of liquid and gaseous hydrocarbon fuels, electricity and hydrogen), and finally calculated emissions of GHGs and three criteria pollutants: reactive organic gases (ROG), nitrogen oxides (NOx), and fine (2.5 ?m) particulate matter (PM2.5). Calculations were generally statewide, but in some sectors, criteria pollutants were also calculated for two regional air basins: the South Coast Air Basin (SCAB) and the San Joaquin Valley (SJV). Three scenarios were developed that attempt to model: (1) all committed policies, (2) additional, uncommitted policy targets and (3) potential technology and market futures. Each scenario received extensive input from state energy planning agencies, in particular the California Air Resources Board. Results indicate that all three scenarios are able to meet the 2020 statewide GHG targets, and by 2030, statewide GHG emissions range from between 208 and 396 MtCO2/yr. However, none of the scenarios are able to meet the 2050 GHG target of 85 MtCO2/yr, with emissions ranging from 188 to 444 MtCO2/yr, so additional policies will need to be developed for California to meet this stringent future target. A full sensitivity study of major scenario assumptions was also performed. In terms of criteria pollutants, targets were less well-defined, but while all three scenarios were able to make significant reductions in ROG, NOx and PM2.5 both statewide and in the two regional air basins, they may nonetheless fall short of what will be required by future federal standards. Specifically, in Scenario 1, regional NOx emissions are approximately three times the estimated targets for both 2023 and 2032, and in Scenarios 2 and 3, NOx emissions are approximately twice the estimated targets. Further work is required in this area, including detailed regional air quality modeling, in order to determine likely pathways for attaining these stringent targets

Modeling California Policy Impacts on Greenhouse Gas Emissions

This paper examines policy and technology scenarios in California, emphasizing greenhouse gas (GHG) emissions in 2020 and 2030. Using CALGAPS, a new, validated model simulating GHG and criteria pollutant emissions in California from 2010 to 2050, four scenarios were developed: Committed Policies (S1), Uncommitted Policies (S2), Potential Policy and Technology Futures (S3), and Counterfactual (S0), which omits all GHG policies. Forty-nine individual policies were represented. For S1-S3, GHG emissions fall below the AB 32 policy 2020 target [427 million metric tons CO2 equivalent (MtCO2e) yr 1], indicating that committed policies may be sufficient to meet mandated reductions. In 2030, emissions span 211 to 428 MtCO2e yr 1, suggesting that policy choices made today can strongly affect outcomes over the next two decades. Long-term (2050) emissions were all well above the target set by Executive Order S-3-05 (85 MtCO2e yr 1); additional policies or technology development (beyond the study scope) are likely needed to achieve this objective. Cumulative emissions suggest a different outcome, however: due to early emissions reductions, S3 achieves lower cumulative emissions in 2050 than a pathway that linearly reduces emissions between 2020 and 2050 policy targets. Sensitivity analysis provided quantification of individual policy GHG emissions reduction benefits