Method for carbon dioxide splitting

A method for splitting carbon dioxide via a two-step metal oxide thermochemical cycle by heating a metal oxide compound selected from an iron oxide material of the general formula AxFe3-xO4, where 0≦x≦1 and A is a metal selected from Mg, Cu, Zn, Ni, Co, and Mn, or a ceria oxide compound of the general formula MaCebOc, where

Screening analysis of solar thermochemical hydrogen concepts.

A screening analysis was performed to identify concentrating solar power (CSP) concepts that produce hydrogen with the highest efficiency. Several CSP concepts were identified that have the potential to be much more efficient than today's low-temperature electrolysis technology. They combine a central receiver or dish with either a thermochemical cycle or high-temperature electrolyzer that operate at temperatures >600 C. The solar-to-hydrogen efficiencies of the best central receiver concepts exceed 20%, significantly better than the 14% value predicted for low-temperature electrolysis

Hybrid metal oxide cycle water splitting

Hybrid thermochemical water splitting systems are disclosed that thermally reduces metal oxides particles to displace some but not all of the electrical requirements in a water splitting electrolytic cell. In these hybrid systems, the thermal reduction temperature is significantly reduced compared to two-step metal-oxide thermochemical cycles in which only thermal energy is required to produce hydrogen from water. Also, unlike conventional higher temperature systems where the reduction step must be carried out under reduced oxygen pressure, the reduction step in the proposed hybrid systems can be carried out in air, allowing for thermal input by a solar power tower with a windowless, cavity receiver

Hybrid metal oxide cycle water splitting

Hybrid thermochemical water splitting cycles are provided in which thermally reduced metal oxides particles are used to displace some but not all of the electrical requirements in a water splitting electrolytic cell. In these hybrid cycles, the thermal reduction temperature is significantly reduced compared to two-step metal-oxide thermochemical cycles in which only thermal energy is required to produce hydrogen from water. Also, unlike the conventional higher temperature cycles where the reduction step must be carried out under reduced oxygen pressure, the reduction step in the proposed hybrid cycles can be carried out in air, allowing for thermal input by a solar power tower with a windowless, cavity receiver

Dish/Stirling systems: Overview of an emerging commercial solar thermal electric technology

Dish/Stirling is a solar thermal electric technology which couples parabolic, point-focusing solar collectors and heat engines which employ the Stirling thermodynamic cycle. Since the late 1970s, the development of Dish/Stirling systems intended for commercial use has been in progress in Germany, Japan, and the US. In the next several years it is expected that one or more commercial systems will enter the market place. This paper provides a general overview of this emerging technology, including: a description of the fundamental principles of operation of Dish/Stirling systems; a presentation of the major components of the systems (concentrator, receiver, engine/alternator, and controls); an overview of the actual systems under development around the world, with a discussion of some of the technical issues and challenges facing the Dish/Stirling developers. A brief discussion is also presented of potential applications for small Dish/Stirling systems in northern Mexico

Status of the Boeing Dish Engine Critical Component Project

The Boeing Company's Dish Engine Critical Component (DECC) project started in April of 1998. It is a continuation of a solar energy program started by McDonnell Douglas (now Boeing) and United Stirling of Sweden in the mid 1980s. The overall objectives, schedule, and status of this project are presented in this paper. The hardware test configuration, hardware background, operation, and test plans are also discussed. A summary is given of the test data, which includes the daily power performance, generated energy, working-gas usage, mirror reflectivity, solar insolation, on-sun track time, generating time, and system availability. The system performance based upon the present test data is compared to test data from the 1984/88 McDonnell Douglas/United Stirling AB/Southem California Edison test program. The test data shows that the present power, energy, and mirror performance is comparable to when the hardware was first manufactured 14 years ago

Summary report : direct approaches for recycling carbon dioxide into synthetic fuel.

The consumption of petroleum by the transportation sector in the United States is roughly equivalent to petroleum imports into the country, which have totaled over 12 million barrels a day every year since 2004. This reliance on foreign oil is a strategic vulnerability for the economy and national security. Further, the effect of unmitigated CO{sub 2} releases on the global climate is a growing concern both here and abroad. Independence from problematic oil producers can be achieved to a great degree through the utilization of non-conventional hydrocarbon resources such as coal, oil-shale and tarsands. However, tapping into and converting these resources into liquid fuels exacerbates green house gas (GHG) emissions as they are carbon rich, but hydrogen deficient. Revolutionary thinking about energy and fuels must be adopted. We must recognize that hydrocarbon fuels are ideal energy carriers, but not primary energy sources. The energy stored in a chemical fuel is released for utilization by oxidation. In the case of hydrogen fuel the chemical product is water; in the case of a hydrocarbon fuel, water and carbon dioxide are produced. The hydrogen economy envisions a cycle in which H{sub 2}O is re-energized by splitting water into H{sub 2} and O{sub 2}, by electrolysis for example. We envision a hydrocarbon analogy in which both carbon dioxide and water are re-energized through the application of a persistent energy source (e.g. solar or nuclear). This is of course essentially what the process of photosynthesis accomplishes, albeit with a relatively low sunlight-to-hydrocarbon efficiency. The goal of this project then was the creation of a direct and efficient process for the solar or nuclear driven thermochemical conversion of CO{sub 2} to CO (and O{sub 2}), one of the basic building blocks of synthetic fuels. This process would potentially provide the basis for an alternate hydrocarbon economy that is carbon neutral, provides a pathway to energy independence, and is compatible with much of the existing fuel infrastructure

Global estimates of mortality associated with long-term exposure to outdoor fine particulate matter.

Exposure to ambient fine particulate matter (PM2.5) is a major global health concern. Quantitative estimates of attributable mortality are based on disease-specific hazard ratio models that incorporate risk information from multiple PM2.5 sources (outdoor and indoor air pollution from use of solid fuels and secondhand and active smoking), requiring assumptions about equivalent exposure and toxicity. We relax these contentious assumptions by constructing a PM2.5-mortality hazard ratio function based only on cohort studies of outdoor air pollution that covers the global exposure range. We modeled the shape of the association between PM2.5 and nonaccidental mortality using data from 41 cohorts from 16 countries-the Global Exposure Mortality Model (GEMM). We then constructed GEMMs for five specific causes of death examined by the global burden of disease (GBD). The GEMM predicts 8.9 million [95% confidence interval (CI): 7.5-10.3] deaths in 2015, a figure 30% larger than that predicted by the sum of deaths among the five specific causes (6.9; 95% CI: 4.9-8.5) and 120% larger than the risk function used in the GBD (4.0; 95% CI: 3.3-4.8). Differences between the GEMM and GBD risk functions are larger for a 20% reduction in concentrations, with the GEMM predicting 220% higher excess deaths. These results suggest that PM2.5 exposure may be related to additional causes of death than the five considered by the GBD and that incorporation of risk information from other, nonoutdoor, particle sources leads to underestimation of disease burden, especially at higher concentrations