Ocean thermal energy: Potentials and pitfalls
Abstract Thermal energy in vast reaches of the world's oceans lies waiting to be tapped by a fuel‐hungry world. The United States— the one heavily industrialized nation with “OTEC”; waters lapping its shores—is actively developing the technology; Japan and a European consortium are also pressing forward. The resource may be of practical value soon to favorably situated islands (e.g., Hawaii, Puerto Rico, Cuba) and Third World countries. Meaningful contributions to mainland U.S. electricity needs are almost certainly a decade or more in the future, and conjectural. Environmental dangers loom if OTEC is too extensively and hurriedly deployed, and for the United States it is not a substitute for nuclear fission and fossil fuel in meeting immediate energy needs.
Quantitative evaluation of closed-cycle Ocean Thermal Energy Conversion (OTEC) technology in central station applications
The results of an independent quantitative evaluation by Rand of Ocean Thermal Energy Conversion (OTEC) for central station applications are summarized. The methodology developed and implemented for the quantitative analysis of cost sensitivities and engineering uncertainties provides the Office of Energy Research (OER) with the capability for evaluating the effects of alternative OTEC R and D strategies. The analysis also provides a general quantitative approach to assess advanced energy technologies. This study focuses on closed-cycle OTEC for delivery of electric power to the United States. Performance and costs of complete commercial OTEC systems are analyzed at the system level using inputs from component analyses and thermal-resource data for sites in the Gulf of Mexico. Such sites could feed the Gulf Coast from the west coast of Florida to the New Orleans areas. In this evaluation, the energy conversion analysis, i.e., the study of the power system, is based on a thermodynamic analysis of the complete system, which includes allowances for losses in all circuits. A cost-minimization scheme is used to ensure that the cycle component choices are near optimal. To make these cost-minimization calculations, cost algorithms are developed for the principal components. Off-design operations are of great importance in themore » Gulf of Mexico because of significant seasonal surface temperature variations and the quite large resulting variations of output power. These effects are accounted for in this study by calculating the off-design performance of the power systems and by selecting the cycle that maximizes the average power over the year. Capital cost estimates are made for the complete system. (WHK)« less
Studies on root enamel (2). Enamel pearls. A review of their morphology, localization, nomenclature, occurrence, classification, histogenesis and incidence.
Enamel pearls are one of a number of different enamel structures that can be found on the roots of deciduous and permanent teeth. They have a distinct predilection for the furcation areas of molar teeth, particularly the maxillary third and second molars. They can consist primarily of enamel, but in most instances, a core of dentin is contained within them. On rare occasions, even pulpal tissues can be found. Enamel pearls usually occur singularly, but up to 4 enamel pearls have been observed on the same tooth. Depending on the study, enamel pearls on permanent molar teeth have an incidence rate of between 1.1%-9.7% with distinct differences among racial and national groups. The incidence of enamel pearls increases greatly in histological studies, suggesting that they are often obscured by a covering of cementum.