The Status and Future of Flywheel Energy Storage

Flywheels, one of the earliest forms of energy storage, could play a significant role in the transformation of the electrical power system into one which is fully sustainable yet low cost. This article describes the major components that make up a flywheel configured for electrical storage and why current commercially available designs of steel and composite rotor families coexist. In the process, design drivers, based on fundamentals are explained in a clear and simple manner inclusive of approaches to safety. The robust characteristics of flywheels deem them highly suitable for applications requiring fast response and high daily cycles, a need that is growing as grid inertia reduces. Lithium Ion batteries are currently the technology of choice for fast response but suffer from limited cycle and calendar life. This can be mitigated by having sufficient energy capacity to limit depth of discharge during short duration cycles whilst using this capacity to earn revenue for provision of other services. Now, as other mechanical, thermal to electric and renewable fuel based storage technologies develop, these will provide storage at a lower cost, greater duration and in a more sustainable way than Lithium Ion. However, the need for fast response storage will remain and steel flywheels are well placed to provide this given potential for low power cost and their sustainability credentials. In order to obtain cost estimates for flywheels in volume production, the cost of the power and storage elements were separated out with costs for each based on similar technologies in volume production. These indicate significantly lower costs than given for current commercially available flywheels, none of which are in volume production relative to Lithium Ion. Finally, some areas of research with potential to improve performance are described but, to be worthwhile, these developments must not lead to increased costs

Radioactive nondestructive test method

Various radioisotope techniques were used as diagnostic tools for determining the performance of spacecraft propulsion feed system elements. Applications were studied in four tasks. The first two required experimental testing involving the propellant liquid oxygen difluoride (OF2): the neutron activation analysis of dissolved or suspended metals, and the use of radioactive tracers to evaluate the probability of constrictions in passive components (orifices and filters) becoming clogged by matter dissolved or suspended in the OF2. The other tasks were an appraisal of the applicability of radioisotope techniques to problems arising from the exposure of components to liquid/gas combinations, and an assessment of the applicability of the techniques to other propellants

Evidence for C II Diffuse Line Emission at Redshift z2.6

C II is one of the brightest emission lines from star-forming galaxies and is an excellent tracer for star formation. Recent work measured the C II emission line amplitude for redshifts 2 < z < 3.2 by cross-correlating Planck High Frequency Instrument emission maps with tracers of overdensity from the Baryon Oscillation Spectroscopic Sky Survey, finding I(CII)=6.6(sup +5.0, sub 4.810(exp 4) Jy/sr at 95per cent confidence level. In this paper, we present a refinement of this earlier work by improving the mask weighting in each of the Planck bands and the precision in the covariance matrix. We report a detection of excess emission in the 545 GHz Planck band separate from the cosmic infrared background (CIB) present in the 353857 GHz Planck bands. This excess is consistent with redshifted C II emission, in which case we report b(CII)I(CII)=2.0(sup +1.2, sub 1.110(exp 5) Jy/sr at 95 per cent confidence level, which strongly favours many collisional excitation models of C II emission. Our detection shows strong evidence for a model with a non-zero C II parameter, though line intensity mapping observations at high spectral resolution will be needed to confirm this result

Cosmic Microwave Background Statistics for a Direction-Dependent Primordial Power Spectrum

Statistical isotropy of primordial perturbations is a common assumption in cosmology, but it is an assumption that should be tested. To this end, we develop cosmic microwave background statistics for a primordial power spectrum that depends on the direction, as well as the magnitude, of the Fourier wavevector. We first consider a simple estimator that searches in a model-independent way for anisotropy in the square of the temperature (and/or polarization) fluctuation. We then construct the minimum-variance estimators for the coefficients of a spherical-harmonic expansion of the direction-dependence of the primordial power spectrum. To illustrate, we apply these statistics to an inflation model with a quadrupole dependence of the primordial power spectrum on direction and find that a power quadrupole as small as 2.0% can be detected with the Planck satellite.Comment: Published in Phys. Rev. D; 8 pages; 1 table; Table 1 corrected; references adde

Interloper bias in future large-scale structure surveys

Next-generation spectroscopic surveys will map the large-scale structure of the observable universe, using emission line galaxies as tracers. While each survey will map the sky with a specific emission line, interloping emission lines can masquerade as the survey's intended emission line at different redshifts. Interloping lines from galaxies that are not removed can contaminate the power spectrum measurement, mixing correlations from various redshifts and diluting the true signal. We assess the potential for power spectrum contamination, finding that an interloper fraction worse than 0.2% could bias power spectrum measurements for future surveys by more than 10% of statistical errors, while also biasing power spectrum inferences. We also construct a formalism for predicting cosmological parameter bias, demonstrating that a 0.15%-0.3% interloper fraction could bias the growth rate by more than 10% of the error, which can affect constraints on gravity upcoming surveys. We use the COSMOS Mock Catalog (CMC), with the emission lines re-scaled to better reproduce recent data, to predict potential interloper fractions for the Prime Focus Spectrograph (PFS) and the Wide-Field InfraRed Survey Telescope (WFIRST). We find that secondary line identification, or confirming galaxy redshifts by finding correlated emission lines, can remove interlopers for PFS. For WFIRST, we use the CMC to predict that the 0.2% target can be reached for the WFIRST H$\alpha$ survey, but sensitive optical and near-infrared photometry will be required. For the WFIRST [OIII] survey, the predicted interloper fractions reach several percent and their effects will have to be estimated and removed statistically (e.g. with deep training samples). (Abridged)Comment: Matches version accepted by PAS

The talented Mr. Littlepage & The Spirit of ’76: An American character study

The curious life of Lewis Littlepage, an American-born courtier in late eighteenth century Europe, revealed the true nature of the United States’ exceptional identity and highlighted the negative effects of social refinement on its unique character. Initially imbued with republican values, Littlepage traveled to Europe in order to pursue a practical political education that would render him useful to the U.S. However, the Virginian’s experiences overseas transformed him into a man unable to control his ambitions, incapable of feeling loyalty to any nation or set of principles, and more dedicated to his personal comfort and luxury than to any sense of republican duty. This study, in order to reach its conclusions, compares Littlepage’s education to that advocated by Thomas Jefferson and examines the differences between the leadership style he eventually developed and the noble republican example modeled by George Washington. It utilizes primary evidence from the Curtis Carroll Davis Collection and the Holladay Family Papers to support its assertions. The uniqueness of the U.S., its exceptionalism, was ultimately a product of its citizens’ self-control. The earliest concern of the nation’s founders, the creators of the grand American experiment to prove that humans were capable of self-government, was how to produce citizens capable of controlling themselves and supporting a republican government. Answering this question, Thomas Jefferson and other Founders concluded that Americans needed a practical republican education and proper role models. The purpose of this training was to teach them how to pursue the common good by controlling their own ambitions, dedicating themselves to republican principles rather than to rulers, and persevering in the face of hardship. Littlepage’s polite education and the process of social refinement he underwent were in opposition to these republican values. Rather than teaching the Virginian to control his own ambitions, to subordinate his interests to the importance of upholding republican values, and to persevere in these endeavors, these processes taught him to proudly display his self-interested ambitions through ostentatious dress and elaborate shows of his useless knowledge. The result was to produce an image of a character that did not conform to America’s exceptional identity

Vehicles for rural transport services in sub-Saharan Africa

There is a critical lack of affordable transport services linking villages to markets, healthcare and other facilities in rural areas of sub-Saharan Africa, which significantly restrains rural development. A key factor is the severe constraint on profitability of services due to the high operating costs of conventional vehicles operating at relatively low speeds on rural roads. This paper argues that there is a need to consider lower-speed alternatives based on motorcycles. It shows that motorcycle-based vehicles such as trailers and three-wheelers can carry loads up to 1 t on rural roads when geared down to an appropriate speed. The operating costs of these vehicles are shown to be around half those of conventional vehicles, greatly increasing the potential for setting up profitable transport services. Further development is needed to show that motorcycle-based vehicles can be used safely and profitably to help rural people improve their livelihoods and facilitate rural development