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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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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Privacy-Preserving Aggregation of Controllable Loads to Compensate Fluctuations in Solar Power

Cybersecurity and privacy are of the utmost importance for safe, reliable operation of the electric grid. It is well known that the increased connectivity/interoperability between all stakeholders (e.g., utilities, suppliers, and consumers) will enable personal information collection. Significant advanced metering infrastructure (AMI) deployment and demand response (DR) programs across the country, while enable enhanced automation, also generate energy data on individual consumers that can potentially be used for exploiting privacy. Inspired by existing works which consider DR, battery-based perturbation, and differential privacy noise adding, we novelly consider the aggregator (cluster) level privacy issue in the DR framework of solar photovoltaic (PV) generation following. Different from most of the existing works which mainly rely on the charging/discharging scheduling of rechargeable batteries, we utilize controllable building loads to serve as virtual storage devices to absorb a large portion of the PV genertaion while delicately keeping desired noisy terms to satisfy the differential privacy for the raw load profiles at the aggregator level. This not only ensures differential privacy, but also improves the DR efficiency in load following since part of the noisy signal in solar PV generation has been filtered out. In particular, a mixed integer quadratic optimization problem is formulated to optimally dispatch a population of on/off controllable loads to achieve this privacy-preserving DR service.

Dong, Jin↗
DOE OSTI2018

Secondary Active Rectifier Control Scheme for a Wireless Power Transfer System with Double-Sided LCC Compensation Topology

This paper proposes a secondary control method using an active rectifier for a double-sided LCC tuned wireless power transfer system (WPT) to reduce the communication requirements of the system. As the active rectifier regulates the output power with a constant primary coil current, the secondary circulating time interval is adjusted while maintaining a unity power factor. First, circuit modelling and sensitivity analyses for the voltage gain, input impedance, coil current rating and power transfer are investigated with a design example of 20kW WPT. Subsequently, the control scheme is developed by considering the four operation modes with the phase difference as the control variable. To prove the effectiveness of the proposed control method, a simulation model is built, and the results demonstrate good dynamic performance with high accuracy for voltage regulation. Compared with the conventional secondary control, it improves the performance of the system along with a well-developed converter gain by maintaining the equivalent load resistive and reduced circulating time intervals, which further improves the system efficiency. The proposed system also eliminates the need for an additional de/de converter on the secondary side.

Zou, Shenli↗
DOE OSTI2018

Sensitivity Analysis of Primary-Side LCC and Secondary-Side Series Compensated Wireless Charging System

This paper presents the sensitivity analysis of primary-side LCC tuned and secondary-side series tuned wireless charging system with experimental validation. The primary and secondary coils have been modeled as a loosely coupled transformer to obtain a circuit model which can be analyzed for parametric sensitivity. Furthermore, sensitivity to variation in coupling coefficient and load are presented. To prove the effectiveness of the theoretical analyses, a test setup was built and tested up to 10kW, demonstrating the operation of the primary-side LCC and secondary-side series wireless power transfer system. The circuit model derived using the loosely coupled transformer model is verified experimentally by using a frequency response analyzer. The experimental results confirmed that the sensitivity analysis can be accurately used for future system designs.

Galigekere, Veda Prakash↗
DOE OSTI2019

Earlier plant growth helps compensate for reduced carbon fixation after 13 years of warming

1. Drylands play a dominant role in global carbon cycling and are particularly vulnerable to increasing temperatures, but our understanding of how dryland ecosystems will respond to climatic change remains notably poor. Considering that the area of drylands is projected to increase by 11%–23% by 2,100, understanding the impacts of warming on the functions and services furnished by these arid and semi-arid ecosystems has numerous implications. 2. In a unique 13-year ecosystem warming experiment in a south-western U.S. dryland, we investigated the consequences of rising temperature on Achnatherum hymenoides, a widespread, keystone grass species on the Colorado Plateau. We tracked individual- and population-level responses to identify optimal strategies that may have been masked if considering only one level of plant response. 3. In this work, we found several factors combined to affect the timing and magnitude of plant responses during the 13th year of warming. These included large warming-induced biomass increases for individual plants, an 8.5-day advancement in the growing season and strong reductions in photosynthetic rates and population cover. 4. Importantly, we observed a lack of photosynthetic acclimation and, thus, a warming-induced downregulation of photosynthetic rates. However, these physiological responses were concurrent with warmed-plant increases in growing season length and investment in photosynthetic surfaces, demonstrating the species’ ability to balance carbon fixation limitations with warming. 5. These results, which bring together ecophysiological, phenological, reproductive and morphological assessments of plant responses to warming, suggest that the extent of change in A. hymenoides populations will be based upon numerous adaptive responses that vary in their direction and magnitude. Plant population responses to climatic warming remain poorly resolved, particularly for Earth's drylands, and our in situ experiment assessing multiple strategies offers a novel look into a warmer world.

54 ENVIRONMENTAL SCIENCES↗