25-year Lifetime Research Articles

Technical and economical evaluation of grid-connected renewable power generation system for a residential urban area

This research investigates the techno-economic assessment of a hybrid grid system of solar and wind power for a residual urban area in Khvaf town located in the eastern part of Iran. The temperature profiles of a 10-year period are gathered based on the existing solar and wind condition data. Simulation, economical and technical evaluations of this hybrid system are studied with the aid of HOMER software. To reach a proper independent structure from the total net present cost and energy cost viewpoints, thousands of cases were studied. Change of the factor investing on PV panels together with the amount of the sun radiance as well as change of the investment factor of wind turbines with the consideration of wind velocity and sun radiance on the system layout are studied and discussed. The initial investment is 440 thousand dollars and the contribution portion of the renewable energies is 84% for the case containing four wind turbines and a power grid system (optimal system). This optimal system returns the investment over a 4-year period which is very economically attractive. The optimal system for the case with a low mean wind speed of 3 m/s is preferred to involve 13-kW photovoltaic (PV) panels, one-wind turbine and a 10-kW converter with a power grid network. Results shown that when the cost of the PV panel is 0.6 times higher than the current cost, a system consisting 4-wind turbines connected to the grid network is still the optimal system. In addition, a sensitivity analysis is made on the load demand of the hybrid system and the renewable energy resource. As a result, the most influential variables on the performance of the system are identified in this research. Based on the economic and technical evaluation, establishing a hybrid grid system for a residential urban area is perfectly reasonable with the investment return during the fourth year of a 25-year project lifetime. Also, among the systems studied, a system with four wind turbines and a power grid system is chosen as an optimal system due to the fact that the region has favorable potential for wind energy.

Fatigue analysis of the steam generator of a parabolic trough solar power plant

This work proposes a methodology to perform the fatigue analysis of the steam generator of a parabolic trough power plant. The following methodology assumes cycling duty scenario (300 start-ups and shut downs per year). Two start-up operations of the steam generator are analyzed: evaporator temperature ramp and heat transfer fluid temperature ramp. Furthermore, a part load operation is studied.The results show that the most compromised parts of the steam generator are the reheater tubesheet for the TEMA CFU design, the steam drum-downcomer junction and the superheater nozzle. Besides, former reheater design (TEMA CFU) does not fulfil the 25-year lifetime condition. To overcome this problem, two alternative designs for the reheater are proposed: U-shell and two TEMA CFU in series. Finally, the lifetimes of TEMA NXU and kettle evaporator designs are compared. Our results show that TEMA NXU allows temperature ramps up to 9 °C/min without putting the steam generator lifetime at risk, whereas kettle temperature ramps greater than 5 °C/min do not fulfil the designed lifetime of 25 years.Respect to the load changes, the evaporator drum is the most stressed element. A 50% load change produces a damage equivalent to 60% of the damage produced by a daily start-up/shut-down cycle.

Lightweighting shipping containers: Life cycle impacts on multimodal freight transportation

Freight transportation by truck, train, and ship accounts for 5% of the United States’ annual energy consumption (U.S. Energy Information Administration, 2017a). Much of this freight is transported in shipping containers. Lightweighting containers is an unexplored strategy to decrease energy and GHG emissions. We evaluate life cycle fuel savings and environmental performance of lightweighting scenarios applied to a forty-foot (12.2 meters) container transported by ship, train, and truck. Use phase burdens for both conventional and lightweighted containers (steel reduction, substitution with aluminum, or substitution with high tensile steel) were compared to life cycle burdens. The study scope ranged from the transportation of one container 100 km to the lifetime movement of the global container fleet on ships. Case studies demonstrated the impact of lightweighting on typical multimodal freight deliveries to the United States. GREET 1 and 2 (Argonne National Laboratory, 2016a,b) were used to estimate the total fuel cycle burdens associated with use phase fuel consumption. Fuel consumption was determined using modal Fuel Reduction Values (FRV), which relate mass reduction to fuel reduction. A lifetime reduction of 21% in the fuel required to transport a container, and 1.4% in the total fuel required to move the vehicles, cargo, and containers can be achieved. It was determined that a 10% reduction in mass of the system will result in a fuel reduction ranging from 2% to 8.4%, depending on the mode. Globally, container lightweighting can reduce energy demand by 3.6 EJ and GHG emissions by 300 million tonnes CO2e over a 15-year lifetime.

Cost-effectiveness of nivolumab in patients with advanced renal cell carcinoma treated in the United States

BackgroundWe evaluated the cost-effectiveness of nivolumab versus everolimus in patients with advanced renal cell carcinoma (RCC) from a US payer perspective.MethodsA partitioned survival model consisting of three health states, progression-free survival (PFS), progressive disease, and death, was developed to evaluate the cost-effectiveness of intravenous nivolumab versus oral everolimus over a lifetime. The proportion of patients in each state was calculated based on parametric distributions fitted to PFS and overall survival (OS) data from CheckMate 025 (N = 821), a large randomized phase 3 trial of nivolumab versus everolimus for advanced RCC. Health state utility data were derived from CheckMate 025 EQ-5D data. Scenario analyses and deterministic and probabilistic sensitivity analyses assessed the impact of uncertainty in model inputs on outcomes.ResultsOver a 25-year lifetime horizon, treatment with nivolumab resulted in a gain of 0.64 quality-adjusted life-years (QALYs) versus everolimus. Nivolumab had greater total costs versus everolimus ($US197,089 vs. $US163,902), mainly due to higher acquisition costs. The incremental cost-utility ratio (ICUR), a measure of incremental costs divided by incremental QALYs, was $US51,714 per QALY gained for nivolumab versus everolimus, and an incremental cost-effectiveness ratio was $US44,576 per life-year gained for nivolumab versus everolimus. In sensitivity analyses, average body weight had the greatest impact on the ICUR for nivolumab versus everolimus (base case $US51,714; range $US8863–$US94,566). At a $US150,000 willingness-to-pay (WTP) threshold, nivolumab had a 91.7% probability of being cost-effective versus everolimus.ConclusionsIn the United States, at a WTP threshold of $US150,000 per QALY, nivolumab was found to be cost-effective. Key drivers of cost-effectiveness were survival inputs for OS and the average weight of patients; the latter directly affects nivolumab drug acquisition cost.

Conditional reliability of bulk carriers damaged by ship collisions

Time-variant reliability analysis of a bulk carrier in damage conditions, after a collision event, is performed by Monte Carlo simulation. Two different collision models are applied, the former based on the deterministic format actually embodied in the Harmonized Common Structural Rules for Oil Tankers and Bulk Carriers, the latter based on a probabilistic format, derived by the recently developed GOALDS database statistics for collision and grounding events. A modified incremental-iterative method is applied, to account for instantaneous neutral axis rotation, due to asymmetrically damaged cross-sections, as for collision events. Time-variant residual strength statistical properties are preliminarily determined by Monte Carlo simulation, up to 25-year ship lifetime, accounting for corrosion wastages of all structural members contributing to hull girder strength, welding residual stresses and material properties randomness. Finally, time-variant reliability analysis is performed, to investigate the incidence of the applied collision damage models on hull girder annual failure probabilities in sagging and hogging conditions. Reliability analysis is performed for the Capesize single side bulk carrier, benchmarked in the 2012 ISSC report and assumed as reference ship in current analysis. Obtained results are fully investigated and discussed.

Energy return on investment, energy payback time, and greenhouse gas emissions of coal seam gas (CSG) production in China: a case of the Fanzhuang CSG project

The studies and development of coal seam gas (CSG) have been conducted for more than 30 years in China, but few of China’s CSG projects have achieved large-scale commercial success; faced with the boom of shale gas, some investors are beginning to lose patience and confidence in CSG. China currently faces the following question: Should the government continue to vigorously support the development of the CSG industry? To provide a reference for policy makers and investors, this paper calculates the EROIstnd [a standardized energy return on investment (EROI) method], EROIide (the maximum theoretical EROI), EROI3,i (EROI considering the energy investment in transport), and EROI3,1+e (EROI with environmental inputs) of a single vertical CSG well in the Fanzhuang CSG project in the Qinshui Basin. The energy payback time (EPT) and the greenhouse gas (GHG) emissions of the CSG systems are also calculated. The results show that over a 15-year lifetime, EROIstnd, EROIide, EROI3,1, and EROI3,1+e are expected to deliver EROIs of approximately 11:1, 20:1, 7:1, and 6:1, respectively. The EPT within different boundaries is no more than 2 years, and the life-cycle GHG emissions are approximately 18.8 million kg CO2 equivalent. The relatively high EROI and short EPT indicate that the government should take more positive measures to promote the development of the CSG industry.

Sizing of Photovoltaic-Wind-Battery Hybrid System for a Mediterranean Island Community Based on Estimated and Measured Meteorological Data

Deploying renewable energy systems (RES) to supply electricity faces many challenges related to cost and the variability of the renewable resources. One possible solution to these challenges is to hybridize RES with conventional power systems and include energy storage units. In this study, the feasibility analysis of a grid-connected photovoltaic (PV)-wind-battery hybrid system is presented as a microgrid for a university campus-scale community on a Mediterranean island. Models for PV and wind turbine systems are presented to estimate energy production, and net present cost (NPC) and levelized cost of electricity (LCOE) are used as economic metrics. A parametric study is performed with hourly time-steps to determine the sizes of energy generation and storage units to minimize the NPC for a small community as the case study. Two alternate configurations with and without storage are proposed. In both cases, the resulting LCOE is 0.15 USD/kWh while the current electricity tariff for the analyzed location was 0.175 USD/kWh in 2015. This lower unit cost of electricity leads to a lower NPC considering a 25-year lifetime. Different estimated and measured solar irradiance and wind speed data sets are used to evaluate the performance of the designed microgrid. Sensitivity analysis on different available weather data sets shows that the uncertainty in wind resource estimations is much higher than the uncertainty in solar resource estimations. Moreover, the results show that solar and wind resources could be utilized synergistically for the studied location.

Natural Regeneration Potential of the Black Saxaul Shrubforests in Semi-Deserts of Central Asia - the Ili River Delta Area, SE Kazakhstan

ABSTRACT Two saxaul species - black saxaul (Haloxylon aphyllum Minkw.) and white saxaul (Haloxylon persicum Bunge) - constitute the principal arboreal cover of the cold continental deserts of Central Asia. While the latter is a rain-fed shrub distributed on sand dunes, the former is a ground-water phreatophyte mainly found on alluvial terraces. Saxaul has played an important role as a fodder plant also used as firewood by local herders. Due to over-grazing and over-exploitation for fuel during the past fifty years, the oncedominant saxaul vegetation has considerably degraded. Important growth characteristics at the present plantations (such as height, and basal trunk and crown diameters) show a direct quantitative relationship between the plants' age up to the 25-year lifetime and the total tree biomass reduced by natural degradation. Annual productivity largely depends on the overall vegetation density that reflects specific environmental conditions at particular locations. The recommended harvest rate, ...

Impact of distributed power electronics on the lifetime and reliability of PV systems

This paper quantifies the impact of distributed power electronics in photovoltaic (PV) systems in terms of end-of-life energy-capture performance and reliability. The analysis is based on simulations of PV installations over system lifetime at various degradation rates. It is shown how module-level or submodule-level power converters can mitigate variations in cell degradation over time, effectively increasing the system lifespan by 5–10 years compared with the nominal 25-year lifetime. An important aspect typically overlooked when characterizing such improvements is the reliability of distributed power electronics, as power converter failures may not only diminish energy yield improvements but also adversely affect the overall system operation. Failure models are developed, and power electronics reliability is taken into account in this work, in order to provide a more comprehensive view of the opportunities and limitations offered by distributed power electronics in PV systems. It is shown how a differential power-processing approach achieves the best mismatch mitigation performance and the least susceptibility to converter faults. Copyright © 2017 John Wiley & Sons, Ltd.

Environmental effect of space debris repositioning

One of the proposed measures to limit the number of near-Earth orbiting fragments to a sustainable level is to actively remove large derelict objects from crowded orbital regions. The two main removal procedures considered so far are (1) a direct targeted reentry maneuver or (2) a deorbit maneuver resulting in a predicted 25-year lifetime for the target object. We study here the viability of a third option, which consists of repositioning the target to an optimally chosen altitude according to a selected benefit/cost objective function. The objective function accounts for both the maneuver cost and the reduction of environmental criticality of the object. Numerical simulations are conducted to determine the optimal sequence of repositioning maneuvers for a given available deorbiting propellant. Results show that an optimal repositioning campaign tends to displace ton-class objects from around 900–1000km altitude down to around 750–800km altitude and to redistribute debris mass from altitudes around 1500km across lower density nearby altitudes. Comparisons with a 25-year lifetime deorbiting suggest a significant performance improvement.

Incidence of load combination methods on time-variant oil tanker reliability in intact conditions

Reliability analysis of an oil tanker in intact conditions is performed to investigate the incidence of load combination methods on hull girder sagging/hogging time-variant failure probability. Particularly, Turkstra rule, Ferry Borges and Castanheta method and Poisson square wave model are applied to evaluate the statistical distribution of bending moment, with reference to both one voyage and 1-year period. Statistical properties of time-variant ultimate strength are determined by Monte Carlo simulation, up to 25-year ship lifetime; bending capacity is determined by means of a modified incremental-iterative method, to account for corrosion wastage of structural members contributing to hull girder strength, welding residual stresses and material properties randomness. After determining the still water load combination factors, based on statistical properties of still water, wave and total vertical bending moments, with reference to 1-year time interval, reliability analysis is performed by Monte Carlo simulation, based on limit state formulations relative to different load combination methods. Finally, the VLCC double hull oil tanker, benchmarked in the 2012 ISSC report, is assumed as a reference ship and obtained results are fully discussed.

Comparative life cycle energy and cost analysis of post-disaster temporary housings

Temporary housings play an important role by providing people a habitable environment while the effects of a disaster are being fixed. In this paper, life cycle energy and cost analysis of two common types of post-disaster temporary housings constructed in Turkey has been studied. The aim of this study was to identify whether it is more convenient to use prefabricated (PH) or container housings (CH) in post-disaster reconstruction projects. Construction and operational energy requirements are calculated over 15years using a comprehensive approach. The energy and financial requirements of the housings have been evaluated by considering four different base areas. The life cycle investment, operation, maintenance, service and end of life costs have been investigated by using the net present value technique. Life cycle primary energy consumption values of the most widely used prefabricated (PH70) and container (CH20) housings are calculated to be 18.5 and 24.7GJ/m2, respectively. The results show that operational phase was dominant over the housings 15-year lifetime. The life cycle cost of PH70 and CH20 are calculated to be 919 and 1308$/m2, respectively. It is found that increasing the total base area of the housings is an important cost-effective energy reduction measure. The results expressed that prefabricated housings have 25.1 and 29.7% lower life cycle energy and cost requirements respectively.

Time-variant bulk carrier reliability analysis in pure bending intact and damage conditions

Time-variant reliability analysis of a corroded bulk carrier in intact and damage conditions is performed by First-Order (FORM), Second-Order (SORM) Reliability Methods and Importance Sampling simulation. Annual failure probabilities are determined up to 25-year ship lifetime, accounting for time-variant corrosion wastage of structural members contributing to hull girder strength. Statistical properties of hull girder capacity are determined by Monte Carlo simulation, applying three correlation models among corrosion wastages of structural members contributing to hull girder strength, namely no correlation, full correlation and full correlation among wastages of structural members belonging to the same category of compartments. A modified incremental-iterative method is applied, to account for instantaneous neutral axis rotation, in case of asymmetrical damage conditions, as for collision and grounding events. Incidence of intact/damage condition, as well as correlation among corrosion wastages, on annual sagging/hogging time-variant failure probability is investigated and discussed. Time-variant sensitivity analyses for intact and damage conditions are also performed, to investigate the incidence of random variables' uncertainties on the attained failure probability. Finally, the bulk carrier section scheme, benchmarked in the last ISSC Report, is applied as test case.

Levelized costs of conventional and battery electric vehicles in china: Beijing experiences

Electric vehicles offer the potential to reduce oil consumption, air pollutants, and greenhouse gas (GHG) emissions. To take advantage of electric vehicles and improve its urban environment, Beijing, as one of China’s most polluted cities, launched an electric vehicle promotion program that provided a generous subsidy for consumers who purchased battery electric vehicles (BEVs). In this study, we compare the levelized costs of a conventional vehicle (CV) versus a BEV using real data from the Beijing BEV subsidy program. Levelized cost for this study considers consumer driving patterns and vehicle age. For consumers with average driving profiles—i.e., an average driving distance of around 20 km per trip—the levelized cost of CVs decreases from 1.40 yuan/km for an 8-year vehicle lifetime to 1.04 yuan/km for a 15-year lifetime, while the levelized cost for BEVs decreases from 1.44 yuan/km for an 8-year vehicle lifetime to 1.01 yuan/km for a 15-year lifetime. BEVs are more cost competitive than CVs for consumers with medium and high driving profiles and a 12-year and 15-year lifetime. Under current conditions, the subsidy and tax incentives are necessary to make BEVs cost competitive. However, we project that, even if the subsidy is phased out in 2020, BEVs may become cost competitive with CVs because of the decrease in battery cost. Our study results suggest that the BEV subsidy should reflect changes in battery cost and gasoline prices to help continuing deployment of BEVs.

Photodegradation in a stress and response framework: poly(methyl methacrylate) for solar mirrors and lens

In the development of materials for enhanced photovoltaic (PV) performance, it is critical to have quantitative knowledge of both their initial performance and their performance over the required 25-year warranted lifetime of the PV system. Lifetime and degradation science, based on an environmental stress and response framework, is being developed to link the inten- sity and net stress to which materials, components, and systems are exposed to the responses observed and their subsequent degradation and damage accumulation over the lifetime. Induced absorbance to dose (IAD), a metric developed for solar radiation durability studies of solar and environmentally exposed materials, is defined as the rate of photodarkening or photobleaching of a material as a function of radiation dose. Quantitative degradation rates like IAD, determined over a wide range of stress intensities and net stresses, have the potential to predict degradation, failure, and power loss rates in photovoltaic systems over time caused by damage accumulation. Two grades of poly(methyl methacrylate) were exposed and evaluated in two cases of high- intensity ultraviolet exposures. A three- to six-fold increase in photodarkening was observed for one acrylic formulation when exposed to UVA-340 light when compared with concentrated xenon-arc exposure. The other, more highly stabilized acrylic formulation, showed up to three times more photodarkening in the same exposure. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.JPE.2.022004)

Durability of Materials in a Stress-Response Framework: Acrylic Materials for Photovoltaic Systems

ABSTRACTIn the development of novel materials for enhanced photovoltaic (PV) performance, it is critical to have quantitative knowledge of the initial performance, as well as the performance of these materials over the required 25-year lifetime of the PV system. Lifetime and degradation science (L&DS) allows for the development of new metrology and metrics, coupled to degradation mechanisms and rates. Induced absorbance to dose (IAD), a new metric being developed for solar radiation durability studies of solar and environmentally exposed photovoltaic materials, is defined as the rate of photodarkening or photobleaching of a material as a function of total absorbed solar radiation dose. In a reliability engineering framework, these quantitative degradation rates can be determined at various solar irradiances making possible real time and accelerated testing. The potential to predict power losses in a photovoltaic system over time caused by the accumulation of this kind of degradation can be calculated for real time applications or extrapolated for accelerated exposure conditions. Three formulations of poly (methyl methacrylate) (PMMA) used for mirror augmented PV systems were analyzed for the changes in IAD after accelerated testing.

Technical and economic evaluation of the utilization of solar energy at South Africa's SANAE IV base in Antarctica

The technical and economic feasibility of utilizing solar energy at South Africa's SANAE IV station in Antarctica was evaluated in order to estimate potential financial and external savings, and to alleviate the programme's dependence on the special blend of diesel shipped annually from Cape Town. The average global horizontal and tilted insolation rates at the base were studied, energy consumption data of the station was investigated, technical performance characteristics of devices for harnessing solar energy were assessed and an economic analysis was completed. It was shown that at SANAE IV flat-plate solar thermal collectors could potentially be used in conjunction with the snow smelter (a device that meets the station's fresh water demand) and that photovoltaic modules could feasibly be used to reduce the station's electrical demand. Flat-plate solar thermal collectors could collect solar energy at an average of 3.13 R/kWh (viz. 0.49 US$/kWh) from a suggested 143 m 2 array, while comparatively a 40 kWp photovoltaic system would be less economically sound and only able to pay back costs at the end of the system's expected 25-year lifetime, generating electricity at an estimated 3.20 R/kWh (annual electrical consumption at SANAE IV amounts to more than 1062 MWh). The total diesel savings of the solar thermal and photovoltaic systems were estimated at approximately 12 245 and 9958 l, respectively, which represent savings in externalities of R67 338 and R55 879 each.

Cost-effective and robust mitigation of space debris in low earth orbit

For the wide acceptance of space debris mitigation measures throughout government agencies and industry, their cost-effectiveness must be demonstrated. The selected measures must not only be effective at controlling the future growth of the debris population, but they should also aim to minimise the collision risk to spacecraft at a minimal cost of implementation. Furthermore, the selected measures must be sufficiently robust to retain their effectiveness if unexpected increases in space activity were to occur. In this paper, clear criteria are established in order to assess numerous different Low Earth Orbit (LEO) debris mitigation scenarios for their cost-effectiveness and robustness. The ESA DELTA debris model is used to provide long-term debris environment projections for these scenarios as an input to the effectiveness/robustness element. Manoeuvre requirements for the different post-mission disposal scenarios are calculated in order to define the cost-related element. A 25-year post-mission lifetime de-orbit policy, combined with explosion prevention and mission-related object limitation, was found to be the most cost-effective solution to the space debris problem in LEO. This package would also be robust enough to retain its effectiveness even after a significant increase in future launch traffic. It was found that the re-orbiting of space systems above the LEO region would not lead to significant collision activity there over the next century. However, above-LEO disposal should be used sparingly because the disposal region could become unstable after a limited number of localised explosion or collision-induced breakup events due to a lack of air drag to remove the resulting fragments.

Comparative Life-Cycle Cost Analysis of Underground Heat Distribution Systems

An analytical model was developed to compare the life-cycle costs of two types of underground heat distribution systems: directly buried conduits and concrete trench installations. The costs of initial construction, routine maintenance, operation, repair, and replacement are represented in the model. Comparisons are made to explore the influence of failure rates, heat loss assumptions, the discount rate, and the policy on partial section replacement. Failure rate estimates are obtained from the literature and also from survey results obtained by the U.S. Army. Life-cycle cost computations indicate that, when initial construction costs are the same, concrete trench installations have a cost advantage of $18-$42 per foot over buried steel conduit when other cost components are taken into account over a 25-year lifetime. The cost advantage of concrete trench over fiberglass reinforcement plastic (FRP) buried systems is $32-$133 per foot. The variation in the cost advantage reflects the variation in the estimate of the failure rate for buried steel and FRP systems. Routine maintenance was crucial for the buried systems to avoid dramatic increases in operation and replacement costs that would make the cost advantage of concrete trench installation even greater than stated above. In contrast, the low incidence of failure associated with concrete trench systems made their life-cycle costs relatively insensitive to maintenance policy.

Hydroponic Production of Cut Chrysanthemums: A Commercial Trial

Abstract A hydroponic nutrient film (NF) system was compared with soil for the production of five cut chrysanthemum crops in a commercial greenhouse. Crops of the cultivars Polaris; Blue, White and Florida Marble; Icecap; Chardonnay; and Heirloom matured 5 days earlier, on average, in NF than in soil. Yields of flowering stems were similar in each system, but close spacing increased productivity per unit greenhouse area for NF. Costs and returns for installation and operation of soil and NF systems in a 1-ha greenhouse were analyzed based on data obtained from the trial crops. Capital and operating costs per unit area increased for NF, but productivity and returns were also greatly improved. Internal rates of return (IRR) were higher for NF, compared to soil, over economic lifetimes ranging from 5 to 25 years. Product price variations caused similar changes in IRR for both systems. A 20% downturn in price, however, resulted in IRR of 3.5% and 19.4% for soil and NF, respectively, over a 25-year lifetime.