The hydrodynamic behavior of two annual legumes (Trifolium angustifolium L. and Onobrychis caput-galli (L.) Lam.) under water shortage was studied in a rain shelter experiment. Seeds were collected ...from natural grasslands of northern Greece and were sown in pots. Two months after seedlings' emergence, full irrigation (up to field capacity) and limited irrigation (40% of field capacity) were applied. During the vegetative period the leaf water potential and the relative water content were measured at seven day intervals in both treatments. T. angustifolium retained the lowest values of psi both under full (-0.11 to -1.78 MPa) and limited irrigation (-0.16 to -2.90 MPa), while the highest values in both cases were those of O. caput-galli (-0.05 to -0.5 MPa). The results suggested that T. angustifolium was the species mostly affected by limited water supply. T. angustifolium seemed to display adaptation mechanisms to drought similar to those of perennial plants. O. caput-galli displayed a more isohydric behavior by not altering its water potential under limited irrigation.
The cost of hydrogen in early fuel cell electric vehicle (FCEV) markets is dominated by the cost of refueling stations, mainly due to the high cost of refueling equipment, small station capacities, ...lack of economies of scale, and low utilization of the installed refueling capacity. Using the hydrogen delivery scenario analysis model (HDSAM), this study estimates the impacts of these factors on the refueling cost for different refueling technologies and configurations, and quantifies the potential reduction in future hydrogen refueling cost compared to today's cost in the United States. The current hydrogen refueling station levelized cost, for a 200 kg/day dispensing capacity, is in the range of $6–$8/kg H2 when supplied with gaseous hydrogen, and $8–$9/kg H2 for stations supplied with liquid hydrogen. After adding the cost of hydrogen production, packaging, and transportation to the station's levelized cost, the current cost of hydrogen at dispensers for FCEVs in California is in the range of $13–$15/kg H2. The refueling station capacity utilization strongly influences the hydrogen refueling cost. The underutilization of station capacity in early FCEV markets, such as in California, results in a levelized station cost that is approximately 40% higher than it would be in a scenario where the station had been fully utilized since it began operating. In future mature hydrogen FCEV markets, with a large demand for hydrogen, the refueling station's levelized cost can be reduced to $2/kg H2 as a result of improved capacity utilization and reduced equipment cost via learning and economies of scale.
•Current hydrogen cost to FCEV customers in California is $13–$15/kg H2.•Hydrogen filling stations have major impact on hydrogen cost to customers.•Refueling stations today contribute $6–$8/kg H2 of the hydrogen cost to customers.•With increased demand, hydrogen fueling cost contribution can be reduced to $2/kg H2.
A quantitative risk assessment of human life during the operation of a hydrogen refueling station (HRS) is conducted. We calculate the risks for three accident scenarios: a hydrogen leak from the ...external piping surrounding a dispenser, a hydrogen leak from an accumulator connection piping and a hydrogen leak from a compressor/connection piping in the HRS. We first calculate the probability of accident by multiplying the estimated leak frequency with the incident occurrence probability considering the ignition probability and failure probability of the safety barrier systems obtained through event tree analysis for each scenario. We next simulate the blast and flame effects of the ignition of concentration fields formed by hydrogen leakage. We then use existing probit functions to estimate the consequences of eardrum rupture, fatalities due to displacement by the blast wave, fatalities due to head injuries, first-degree burns, second-degree burns, and fatal burn injuries by accident scenario, leak size, and incident event, and we estimate the risk distribution in 1-m cells. We finally assess the risk reduction effects of barrier placement and the distance to the dispenser and quantify the risk level that HRSs can achieve under existing law. Quantitative risk assessment reveals that the risk for a leak near the dispenser is less than 10−6 per year outside a distance of 6 m to the dispenser. The risk for a leak near the accumulators and compressors exceeds 10−4 per year within a distance of 10 m from the ignition point. A separation of 6 m to the dispenser and a barrier height of 3 m keep the fatal risk from burns to the workers, consumers and residents and passersby below the acceptable level of risk. Our results therefore show that current laws sufficiently mitigate the risks posed by HRSs and open up the possibility for a regulatory review.
•A quantitative risk assessment of human life in a hydrogen refueling station (HRS) was conducted.•A separation distance of 6 m to the dispenser keeps the fatal risk from burns to the residents and passersby.•A barrier height of 3 m keeps the fatal risk from burns to the workers and consumers in the HRS.•Current laws sufficiently mitigate the risks posed by HRSs.
In this paper, we show the rapid generation of phase diagrams for block copolymer amphiphiles. We demonstrate the high-throughput approach for two separate types of amphiphilic block copolymers: One ...type consisting of poly(ethylene glycol)-b-poly(2-hydroxypropyl methacrylate) and the other consisting of poly(2-(dimethylamino)ethyl methacrylate)-b-poly(2-hydroxypropyl methacrylate), where each amphiphilic block copolymer was prepared by systematically varying the degree of polymerization of the hydrophobic block. These were each synthesized in 96-well plates using polymerization-induced self-assembly to rapidly generate a range of morphologies in aqueous solution. In this manner, 45 different assembled polymer samples were prepared at a time. These samples were sampled by automated picoliter volume liquid handling (piezoelectric robotic dispenser) and analyzed by automated transmission electron microscopy and automated image analysis to rapidly generate phase diagrams.
In this study, different hydrogen refueling station (HRS) architectures are analyzed energetically as well as economically for 2015 and 2050. For the energetic evaluation, the model published in ...Bauer et al. 1 is used and norm-fitting fuelings according to SAE J2601 2 are applied. This model is extended to include an economic evaluation. The compressor (gaseous hydrogen) resp. pump (liquid hydrogen) throughput and maximum pressures and volumes of the cascaded high-pressure storage system vessels are dimensioned in a way to minimize lifecycle costs, including depreciation, capital commitment and electricity costs. Various station capacity sizes are derived and energy consumption is calculated for different ambient temperatures and different station utilizations. Investment costs and costs per fueling mass are calculated based on different station utilizations and an ambient temperature of +12 °C. In case of gaseous trucked-in hydrogen, a comparison between 5 MPa and 20 MPa low-pressure storage is conducted. For all station configurations and sizes, a medium-voltage grid connection is applied if the power load exceeds a certain limit. For stations with on-site production, the electric power load of the hydrogen production device (electrolyzer or gas reformer) is taken into account in terms of power load. Costs and energy consumption attributed to the production device are not considered in this study due to comparability to other station concepts. Therefore, grid connection costs are allocated to the fueling station part excluding the production device. The operational strategy of the production device is also considered as energy consumption of the subsequent compressor or pump and the required low-pressure storage are affected by it. All station concepts, liquid truck-supplied hydrogen as well as stations with gaseous truck-supplied or on-site produced hydrogen show a considerable cost reduction potential. Long-term specific hydrogen costs of large stations (6 dispensers) are 0.63 €/kg – 0.76 €/kg (dependent on configuration) for stations with gaseous stored hydrogen and 0.18 €/kg for stations with liquid stored hydrogen. The study focuses only on the refueling station and does not allow a statement about the overall cost-effectiveness of different pathways.
•Energetic and economic comparison of hydrogen refueling station concepts.•Main components are sized in a way to minimize lifecycle costs.•Analysis based on ambient temperature and utilization for several station sizes.•For large liquid station concept costs of 0.18 € per kg expected in 2050.•For large gaseous station concepts costs of 0.63–0.76 € per kg expected in 2050.
Fuel cell electric vehicles (FCEVs) have now entered the market as zero-emission vehicles. Original equipment manufacturers such as Toyota, Honda, and Hyundai have released commercial cars in ...parallel with efforts focusing on the development of hydrogen refueling infrastructure to support new FCEV fleets. Persistent challenges for FCEVs include high initial vehicle cost and the availability of hydrogen stations to support FCEV fleets. This study sheds light on the factors that drive manufacturing competitiveness of the principal systems in hydrogen refueling stations, including compressors, storage tanks, precoolers, and dispensers. To explore major cost drivers and investigate possible cost reduction areas, bottom-up manufacturing cost models were developed for these systems. Results from these manufacturing cost models show there is substantial room for cost reductions through economies of scale, as fixed costs can be spread over more units. Results also show that purchasing larger quantities of commodity and purchased parts can drive significant cost reductions. Intuitively, these cost reductions will be reflected in lower hydrogen fuel prices. A simple cost analysis shows there is some room for cost reduction in the manufacturing cost of the hydrogen refueling station systems, which could reach 35% or more when achieving production rates of more than 100 units per year. We estimated the potential cost reduction in hydrogen compression, storage and dispensing as a result of capital cost reduction to reach 5% or more when hydrogen refueling station systems are produced at scale.
•Accelerated roll-outs of hydrogen stations in many countries in Europe, Asia and North America.•Discussion of manufacturing analysis of key parts in the hydrogen stations.•Reduction of the hydrogen station cost could play role in reducing the cost of hydrogen at the pump.•U.S. based manufacturers have advantages of the long experience and low energy cost.•Storage bank and compressors are the key cost contributor in the hydrogen station.
•Design and fabrication of TEGs for low temperature waste heat application.•Scalable manufacturing demonstrated using dispenser printing.•Achieved power output 33×10−6W and power density of ...2.8Wm−2.•Practical situation of pipes carrying hot fluid simulated in the lab.•The power output evaluated in forced convection and natural convection.
This work focuses on the design, fabrication and testing of thermoelectric generator (TEG) devices using dispenser printer. A series-parallel prototype of 50 couples, with 3.5mm×600μm×100μm printed element dimensions, is fabricated on a custom designed polyimide substrate. Se doped mechanically alloyed (MA) Bi2Te3 was used as the n-type material whereas Te doped MA Bi0.5Sb1.5Te3 was used as p-type material. The prototype TEG device produces a power output of 33×10−6W at 0.75×10−3A and 43×10−3V for a temperature difference of 20K resulting in a device areal power density of 2.8Wm−2. To achieve a similar power output in a practical situation, such as from pipes carrying hot fluid an experimental study in forced and natural convection is performed. In forced convection, 33×10−6W power output is achieved when the pipe surface temperature is about 373K. While, in natural convection, maximum power up to 8×10−6W power is obtained at 373K pipe surface temperature. Forced convection is desired for the system to generate sufficiently high power. In the case of natural convection, we achieved much lower power compared to forced convection. The prototype presented in this work demonstrates the feasibility of deploying a printable and “perpetual” power solution for practical wireless sensor network (WSN) applications.
We conducted a techno-economic and thermodynamic analysis of precooling units (PCUs) at hydrogen refueling stations and developed a cost-minimizing design algorithm for the PCU observing the SAE ...J2601 refueling protocol for T40 stations (requiring −40 °C precooling temperature). In so doing, we identified major factors that affect PCU cost and energy use. The hydrogen precooling energy intensity depends strongly on the station utilization rate, but approaches 0.3 kWhe/kg-H2 at full utilization. In early fuel cell electric vehicle markets where utilization of the refueling capacity is low, the overhead cooling load (to keep the heat exchanger cold at −40 °C) results in significantly high PCU energy intensity because only a small amount of hydrogen is being dispensed. We developed a parameterized precooling energy intensity prediction formula as a function of the ambient temperature and station utilization rate. We also found that the Joule-Thomson effect of the flow control device introduces a significant increase in temperature upstream of the PCU's heat exchanger (HX), which impacts the PCU design capacity. An optimal PCU (per dispenser, at 35 °C HX inlet temperature) consists of a 13-kW refrigerator and a HX with 1400 kg of thermal mass (aluminum), which currently costs $70,000 (uninstalled). The total (installed) capital and operation cost of PCU at a fully utilized hydrogen refueling station adds $0.50/kg-H2.
•Tradeoff between different precooling unit (PCU) design options are assessed.•An optimal PCU consists of a 13-kW refrigerator and a 1400 kg of HX thermal mass.•Hydrogen precooling energy intensity approaches 0.3 kWhe/kg-H2 at full utilization.•PCU cost at a fully utilized hydrogen refueling station adds $0.50/kg-H2.•J-T effect of the flow control device causes significant increase in temperature.
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