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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Development of Mission Profiles for Humidity Models in the Reliability Testing of PV Inverters: Preprint

To understand the impacts of humidity on PV inverters, mission profiles were developed to accurately describe the different processes and rates based on the environmental factors of temperature, relative humidity, and irradiance. The operating environment of the device introduces stress factors dependent on component temperature, relative humidity, and component voltage. The development of profiles started from looking at historical climate conditions at Cocoa, Florida, a hot and humid location. The profile developed from field location was compared with existing humidity test profiles in industrial and military standards to determine acceleration factors. Prior to the evaluation of the mission profiles, critical components in the PV inverter were identified based on vendor discussions along with failure modes of interest. The profiles considered in this study was demonstrated using a 4-kVA string inverter. The measurements from the devices were substituted in device manufacturer specified equation to determine the severity of each test. The severity of each test was compared against the severity of the 24-hour result to determine the acceleration factor of each test. The acceleration factors were determined to be over a range of 1.2-6 for the existing humidity tests from standards, when compared against the mission profile developed from field data. This optimal humidity/thermal profile will be passed to the IEC standards development for inverter qualification testing.

humidity models↗
DOE OSTI2021

Inverters: A Pivotal Role in PV Generated Electricity

This presentation discusses the pivotal role inverters play in PV generated electricity. Topics include: the inverter as the center of the system--increasingly becoming the brain, with more features and capabilities (hybrid systems, safety, islanding, monitoring, etc.); increasing inverter-based generated electricity associated with many renewable energy sources; increased dependence for grid support and forming capability; communication within the grid and security increasingly required; increasing complexity leads to more chances to fail; as in most PV segments, there is cost reduction pressure, which makes it more challenging to keep the reliability high.

ENGINEERING,SOLAR ENERGY↗
DOE OSTI2022

Gallium nitride electromagnetic pulse arrestor

A GaN diode EMP arrestor exhibits breakdown in <10 ns at reverse-bias voltage >20 kV. Additionally, the arrestor exhibits avalanche ruggedness at 1 kA/cm 2 in a 1 mm 2 device (i.e. 10 A absolute current) over a period of 500 ns following the onset of breakdown. Finally, the specific on-resistance in the forward direction is <20 mΩ cm 2 .

Kaplar, Robert↗
DOE OSTI2016

Uranium from Seawater Cost Analysis: Recent Updates

Uranium from seawater can act as an economic backstop by putting an effective ceiling on the cost of recovering uranium. Although it is not meant to be a direct competitor with conventionally mined uranium there is significant effort, by a consortium of five national labs and ten universities, to improve the recovery process. Accurately predicting the cost associated with this method of uranium production is an important factor in determining a cost ceiling for uranium fuels and assuring supply security for uranium based nuclear fuel cycles. Given the evolving nature of this technology, this paper aims to provide an update of the economic model to reflect recent progress. The recovery system analyzed here is a passive collection process under persistent development by Oak Ridge and Pacific Northwest National Labs (ORNL and PNNL). The process relies on an amidoxime based uranium adsorbents constructed by co-grafting an amidoxime precursor and a hydrophilic comonomer onto a high density polyethylene (HDPE) backbone. After further chemical processing the adsorbent fibers are braided into 60 meter segments. The braids are then sent out to sea where they are moored to the bottom of the ocean. Upon realization of their soaking campaign the braids are winched up so the uranium may be eluted off the adsorbent. The acidic chemicals used in the elution process require an alkaline regeneration procedure to be applied to the adsorbent before it can be redeployed for another campaign. The deployment and elution process is repeated as many times as economically feasible, as dictated by the severity of degradation suffered by the braid due to the elution process and exposure to seawater. A large number of design and deployment parameters influence the final uranium production cost. Some are strongly affected by the chemical technologies, such as uranium uptake and degradation rate, while others are operational parameters, such as number of adsorbent uses and length of soaking campaign. Still others are both intrinsic and affected by operational choices, such as the ocean temperature and degree of oceanic biofouling. Recent experiments have been focused on improved characterization of the effect of: oceanic temperature, a novel elution method, adsorbent degradation rates, and oceanic biofouling, and they will therefore be the focus of this paper. The degradation results presented here are likely to represent a worst case scenario. Since chemically similar adsorbents were able to achieve a much lower degradation rate with the previous acidic elution process it is very possible that modifications can be made to the new adsorbents to ameliorate the degradation suffered, especially with the new bicarbonate elution process, which is believed to be less harsh. Similarly, the 30% loss in uptake suffered as a result of biofouling is likely an upper-bound. The experiments were conducted in full light and at 20 deg. C. In reality however the braids will be submersed approximately 100 meters beneath the surface, potentially subject to a temperature gradient that may influence biofouling patterns. Also the light reaching the adsorbent surface may not be as intense as in laboratory conditions due to seawater turbidity and shadows cast by nearby braids. In light of these factors, it is appropriate to present a range of costs, reflecting the best and worst case scenarios of all of the parameters considered here. Table II shows the updated parameter ranges and uranium production costs. Ongoing work, particularly into the mitigation of biofouling and degradation, is expected to tighten this cost range and reduce the predicted cost. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Uranium from Seawater Cost Analysis: Recent Updates

While it is not meant to be a direct competitor with conventionally mined uranium, seawater uranium has significant potential to sway policy makers and the public toward the long term viability of nuclear power. Given the large mass of uranium contained within the ocean and its continual replenishment by freshwater run-off and the ocean floor, seawater uranium can be considered for all practical purposes a renewable resource. In addition to this assurance of supply security placing nuclear power on equal footing with other renewable energy generation technologies, seawater uranium removes a key uncertainty by establishing a cost ceiling on uranium based fuels. Given the evolving nature of this technology, this paper aims to provide an update of the economic model to reflect recent progress. This analysis will reference a passive collection system currently under development by Oak Ridge and Pacific Northwest National Labs. This system consists of a polymer modified to contain amidoxime functional groups, a ligand with high uranium affinity. The adsorbing material is then braided into long segments so it may be moored to the bottom of the ocean where it passively collects uranium for a period on the order of weeks to months. Upon completion of its soaking campaign adsorbent is winched to the surface by work boats so the uranium may be eluted off the braids. After a chemical rinse the braids may then be redeployed for another soaking campaign and uranium elution. The adsorbent can be redeployed as many times as is economically feasible, which is a function of the degradation the material suffers upon each reuse. Noteworthy experimental progress has tightened the gap separating estimates of the optimistic and pessimistic case uranium production cost relative to the most recent analysis. It has been demonstrated before that significant uncertainty in adsorbent performance, and thus recovery cost, arises primarily from variability in adsorbent degradation upon reuse and the effects of marine biofouling on uptake. While the underlying recovery mechanism remains, significant changes have been made regarding the method of adsorbent synthesis, propagating to improvements in adsorbent durability. Additionally, further experimentation regarding the area of marine biofouling has tightened the range of expected adsorbent performance when placed in true marine conditions.

07 ISOTOPE AND RADIATION SOURCES↗