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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 OSTI2024

Exploring Dynamic P-Q Capability and Abnormal Operations of Inverter-Based Resources

Nowadays, inverter-based resources are rapidly growing in electric power systems. On the other side, abnormal inverter operations are also occurring more often. Traditionally, inverter PQ capability charts are employed by electric utility companies to ensure safe and reliable operations of inverter-based resources. However, it is found in this paper that existing inverter PQ capability charts do not address the operating characteristics of an inverter correctly, which can result in irregular and unstable inverter operations. Here in this paper, a novel study is conducted to investigate inverter PQ capability charts, where constraints that are specific to an inverter are considered. It is found in this paper that the inverter PQ capability charts exhibit a unique dynamic nature under uncertain grid conditions. This dynamic nature has not been considered by the industry in managing, designing, and controlling an inverter as well as in developing international standards for inverter-based resources. Via both electromagnetic transient simulation and hardware experimental investigations, it is found that the dynamic PQ capability nature, together with the limitations of the existing control methods, are the underlying causes of many unusual inverter operations that have been reported in the literature.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2021

In-Operando Characterization of P-I-N Perovskite Solar Cell Under Reverse Bias

A solar module is often exposed to a variety of intensity and uniformity illumination conditions throughout a day. In the field, objects or dirt can block light from hitting the module creating a partial shading event. When a partial shading event occurs the module power point tracking system will typically push the shaded cells into reverse bias in order to avoid the current loss from the other series connected illuminated cells. When perovskite solar cells are operated in reverse bias, electrochemical reactions can occur, leading to both reversible and irreversible performance losses. Excess holes generated by reverse bias cause and push the oxidation reaction of halide ions from the lattice to neutral halogen interstitial. Small interstitial halogen atoms can diffuse across the device and potentially move from the perovskite layer and into the transport layers, shifting the fermi levels in the devices. In this investigation we utilize cross-sectional kelvin probe atomic force microscopy to map the band energetics of perovskite solar cells during reverse bias. We observe a 150 meV decrease in the work function of the C 60 . This leads to a decrease of 150 mV and 4 mA/cm 2 in V oc and in J sc respectively. Finally, we discuss methods to prevent this irreversible degradation after a perovskite device is held under reverse bias.

fullerene↗
DOE OSTI2022

Mesophyll conductance response to short-term changes in p CO 2 is related to leaf anatomy and biochemistry in diverse C 4 grasses

Mesophyll CO 2 conductance (g m ) in C 3 species responds to short-term (minutes) changes in environment potentially due to changes in leaf anatomical and biochemical properties and measurement artefacts. Compared with C 3 species, there is less information on g m responses to short-term changes in environmental conditions such as partial pressure of CO 2 (pCO 2 ) across diverse C 4 species and the potential determinants of these responses. Using 16 C 4 grasses we investigated the response of g m to short-term changes in pCO 2 and its relationship with leaf anatomy and biochemistry. In general, g m increased as pCO 2 decreased (statistically significant increase in 12 species), with percentage increases in gm ranging from +13% to +250%. Greater increase in g m at low pCO 2 was observed in species exhibiting relatively thinner mesophyll cell walls along with greater mesophyll surface area exposed to intercellular air spaces, leaf N, photosynthetic capacity and activities of phosphoenolpyruvate carboxylase and Rubisco. Species with greater CO 2 responses of g m were also able to maintain their leaf water-use efficiencies (TE i ) under low CO 2 . Our study advances understanding of CO 2 response of g m in diverse C 4 species, identifies the key leaf traits related to this response and has implications for improving C 4 photosynthetic models and TE i through modification of g m .

59 BASIC BIOLOGICAL SCIENCES↗