How Does Wind Project Performance Change with Age in the United States?

Wind-plant performance declines with age, and the rate of decline varies between regions. The rate of performance decline is important when determining wind-plant financial viability and expected lifetime generation. We determine the rate of age-related performance decline in the United States wind fleet by evaluating generation records from 917 plants. We find the rate of performance decline to be 0.53%/year for older vintages of plants and 0.17%/year for newer vintages of plants on an energy basis for the first 10 years of operation, which is on the lower end of prior estimates in Europe. Unique to the United States, we find a significant drop in performance by 3.6% after 10 years, as plants lose eligibility for the production tax credit. Certain plant characteristics, such as the ratio of blade length to nameplate capacity, influence the rate of performance decline. These results indicate that the performance decline rate can be partially managed and influenced by policy

Deviations from Matthiessen's Rule for SrRuO3{\rm SrRuO_3} and CaRuO3{\rm CaRuO_3}

We have measured the change in the resistivity of thin films of ${\rm SrRuO_3}$ and ${\rm CaRuO_3}$ upon introducing point defects by electron irradiation at low temperatures, and we find significant deviations from Matthiessen's rule. For a fixed irradiation dose, the induced change in resistivity {\it decreases} with increasing temperature. Moreover, for a fixed temperature, the increase in resistivity with irradiation is found to be {\it sublinear}. We suggest that the observed behavior is due to the marked anisotropic scattering of the electrons together with their relatively short mean free path (both characteristic of many metallic oxides including cuprates) which amplify effects related to the Pippard ineffectiveness condition

Financing investments in renewable energy: The role of policy design and restructuring

The costs of electric power projects utilizing renewable energy technologies are highly sensitive to financing terms. Consequently, as the electricity industry is restructured and new renewables policies are created, it is important for policymakers to consider the impacts of renewables policy design on project financing. This report describes the power plant financing process and provides insights to policymakers on the important nexus between renewables policy design and finance. A cash-flow model is used to estimate the impact of various financing variables on renewable energy costs. Past and current renewable energy policies are then evaluated to demonstrate the influence of policy design on the financing process and on financing costs. The possible impacts of electricity restructuring on power plant financing are discussed and key design issues are identified for three specific renewable energy programs being considered in the restructuring process: (1) surcharge-funded policies; (2) renewables portfolio standards; and (3) green marketing programs. Finally, several policies that are intended to directly reduce financing costs and barriers are analyzed. The authors find that one of the key reasons that renewables policies are not more effective is that project development and financing processes are frequently ignored or misunderstood when designing and implementing renewable energy incentives. A policy that is carefully designed can reduce renewable energy costs dramatically by providing revenue certainty that will, in turn, reduce financing risk premiums

Creek habitats as sources for the spread of an invasive herb in a New Zealand mountain landscape

Landscapes typically comprise various habitats that differ in their susceptibility to invasion by exotic species. Highly invasible habitats such as riparian corridors can act as a conduit for rapid movement across the landscape and as a propagule source to facilitate spread into adjacent, less invasible habitats. If this is so, there should be a decline in invader frequency and/or abundance with distance away from the source; the local abundance of invasive species in the source habitat should be positively correlated with local abundance in the adjacent habitat; and, having accounted for variation in local source population size, the slope of the decline in invader abundance with distance away from the source habitat should reflect the ease with which adjacent habitat can be invaded. Here, we test these predictions to assess whether creek habitats function as a source to facilitate the spread of the invasive plant Hieracium lepidulum Stenstr. (Asteraceae) in upland catchments of the South Island, New Zealand, by surveying H. lepidulum abundance in creek margin and adjacent beech forest and subalpine habitat in 17 creek catchments. Our results imply that propagule pressure from populations in creek margins and other disturbed areas is driving catchment-wide H. lepidulum invasion, but forest and subalpine habitats currently differ in the way H. lepidulum spreads from source populations. Our results suggest that H. lepidulum invasion is at an earlier stage in subalpine areas, that there are few barriers to invasion across this habitat, and that subalpine habitats will become more heavily invaded than forests. These findings can be used to underpin monitoring strategies and management prioritisation for this invader

California renewable energy policy and implementation issues: An overview of recent regulatory and legislative action

This paper has three primary goals: (1) to provide a brief account of recent events in California renewables policy; (2) to outline the California State Legislature`s ultimate decision on renewable energy policy; and (3) to aid other states in their efforts with renewables policy by summarizing some of the key implementation issues and political conflicts that may occur when crafting some of the potential threats and opportunities that electricity restructuring presents to the development of renewable energy. We then outline the renewables policy debate in California since the California Public Utility Commission`s ``Blue Book``, including both regulatory and legislative developments. We also provide some insight into the minimum renewables purchase requirement (MRPR) versus surcharge-based renewables policy debate in California. Finally, we identify and discuss key renewables policy implementation issues that have driven the dialogue and recent decisions in California`s renewables policy

Sequential low-temperature depolymerization and liquefaction of US coals

Suitable conditions for high-yield conversion of a Pittsburgh [number sign]8 (Pennsylvania) coal sample, supplied by the Argonne program and designated below as PB(PA) coal, were previously developed (see Progress Report no. 4, pp. 3--15; and Progress Report no. 6, pp- 3--4). In some recent experiments, the yield of low-boiling hydrocarbon fuel fractions (gasoline, kerosene and gas oil; b.p. up to 325[degrees]C) from this coal was further increased to a level of 70--72 wt % (MAF basis). The main emphasis of the research work during the reporting period was on the structural analysis of the depolymerized PB(PA) coal, with the uftimate objective of developing an average molecular structure for the predominant (71.5 -- 76.0 wt %) oil fraction (fr. no. 6, Figure 1) as well as for the small asphattene and asphaftol fractions (fr. no. 7 and 8, Figure 1) of this depolymerized product. The oil and asphaftene fractions of the depolymerized PB(PA) coal (Figure 1, fractions [number sign]6 and 7, respectively) were analyzed by gas chromatography/mass spectrometry (GC/MS). Figure 2 shows the reconstructed ion chromatogram for the oil fraction of the depolymerized PB(PA) coal. As seen, the bulk of the compounds present in this fraction elute in the 125--225[degrees]C range as an incompletely resolved hump. It is indicated that the oil contains a wide range of compound types

Sequential low-temperature depolymerization and liquefaction of US coals

A Beulah-Zap (North Dakota) lignite sample, designated below as BZ(ND) lignite, was obtained from the Argonne National Laboratory premium coal program. This lignite had the following ultimate analysis (MAF basis) in wt.%: C, 71.05; H, 5.58; N, 1.17; S, 1.60; 0 (diff), 20.6. The ash content (dry basis) was 6.0 wt.%. As expected, the BZ(ND) lignite had a considerably higher oxygen content ([approximately]20.6%) in comparison with that of previously studied coals (Progress Reports nos. 1--4). The BZ(ND) lignite was subjected to a previously developed stepwise depolymerization-liquefaction procedure [for details and recent applications see J. Shabtai and T. Skulthai, Proc. 1987 Internat. Confer. Coal Science, Elsevier, Amsterdam (J.A. Moulijn, K.A. Nater, and H.A.G. Chermin, Eds.), 1987, pp. 761764; and J. Shabtai, T. Skulthai, and I. Saito, Am. Chem. Soc. Div. Fuel Chem. Prepr., 31 (4), 15--23 (1986)]. The procedure, as summarized in Figure 1, consists essentially of the following sequential steps: (1) intercalation of the coal sample with catalytic amounts (5--20 %) of FeCl[sub 3] followed by mild hydrotreatment (HT) of the coal-FeCl[sub 3] intercalate; (2) base-catalyzed depolymerization (BCD) of the product from step 1, under super-critical conditions; and (3) hydroprocessing (HPR) of the depolymerized product from the two preceding steps, using a sulfided 6Co8Mo catalyst. The results obtained in processing the BZ(ND) lignite according to the above procedure are described

Sequential low-temperature depolymerization and liquefaction of US coals

Results obtained in the studies with BS(IL) coal as feed can be summarized as follows: (1) The low-temperature depolymerization - liquefaction procedure, summarized in Figure 1, is easily adaptable and applicable to a high-sulfur, Burning Star (Illinois No. 6) coal sample. The final product obtained consists of a fully desulfurized, light hydrocarbon oil. (2)Suitable processing conditions for each step of the stepwise depolymerization - liquefaction of the above coal were determined. (3)Direct hydroprocessing of the Burning Star (Illinois No. 6) coal with sulfided catalysts is ineffective for its conversion into a light hydrocarbon product. In accordance with the research program the depolymerized, THF-soluble coal products will be subjected to detailed analysis for the purpose of deriving average molecular structures for the oil, asphaltene and asphaltol fractions. The data obtained will be used to develop a structural model for the BS(IL) coal

Magnetic susceptibility of insulators from first principles

We present an {\it ab initio} approach for the computation of the magnetic susceptibility $\chi$ of insulators. The approach is applied to compute $\chi$ in diamond and in solid neon using density functional theory in the local density approximation, obtaining good agreement with experimental data. In solid neon, we predict an observable dependence of $\chi$ upon pressure.Comment: Revtex, to appear in Physical Review Lette