Economic Sizing of Batteries for the Smart Home

Growing rooftop photovoltaics (PV) adoption is beginning to challenge the electric power grid in some locations today. During many hours of the year, power is flowing out of PV-enabled buildings and back into grid. When this happens in many homes, the entire feeder voltage is raised significantly, which can be unsafe for grid assets and home appliances. Battery storage provides a good solution to this problem. By storing energy within the home, less energy flows back onto the grid. Scheduling a battery to charge during times a home would otherwise export energy, and discharge when it would otherwise import energy, the bidirectional flow of energy on the feeder is reduced. However, batteries are still expensive and need to be introduced optimally. Battery sizing is not well studied in the literature; most research uses rule of thumb to determine the battery size whereas others use tool-based methods. This paper presents a methodology to economically size a residential battery based on parametric analysis using a home energy management system (HEMS) software to optimally dispatch the battery along with controllable loads under several use cases. The study accounts for connected equipment, controls, renewable resources, and accounts for other factors such as occupancy patterns, and house characteristics. The paper defines an initial analytical pathway for such a sizing tool, develops initial sizing guidance, and clarifies technical and market opportunities for home batteries in the context of existing and emerging equipment and control technologies. One of the unique contributions of our paper is that we demonstrate how dynamic control of building equipment may change the selection, operation, lifespan and economics of solar and battery storage. We use the HEMS to optimally control the same solar-enabled residential building in three different use cases: a) with controllable loads, b) with controllable battery, and c) with controllable loads and battery. As more loads can be interactively controlled, they can relieve the burden of some of the battery’s use. This may change the cycling use cases for the battery, and possibly enable smaller batteries to be used in conjunction with equipment homeowners are already purchasing to achieve the same outcomes. In our initial study, a parametric analysis that included 132 scenarios has been performed based on different combinations of pertinent parameters. Results indicate that four parameters dominate the decision-making process: utility tariffs, application scenarios, existence of HEMS, and the anticipated payback time. Life-cycle cost analysis indicated in the absence of utility incentives, batteries plus HEMS haveat least 10-year payback time for new construction under time-of-use rate structure and feed-in tariff; larger batteries have longer payback time but may provide more benefits to utilities on power backfeed reduction under certain circumstances

Model-free Method of Reinforcement Learning for Visual Tasks

There has been success in recent years for neural networks in applications requiring high level intelligence such as categorization and assessment. In this work, we present a neural network model to learn control policies using reinforcement learning. It takes a raw pixel representation of the current state and outputs an approximation of a Q value function made with a neural network that represents the expected reward for each possible state-action pair. The action is chosen an \epsilon-greedy policy, choosing the highest expected reward with a small chance of random action. We used gradient descent to update the weights and biases of this network as it is efficient in terms of computation and convergence rate even with large scale models. To test this network, we designed a simple search task over a 4x4 grid. No assumptions were made about the control task. Given only raw inputs for state and the reward received from actions paired with that state, the agent was able to learn this task. Performance was evaluated using the number of rewards received out of 10000 opportunities. Over the course of 5 epochs, the network demonstrated significantly higher accuracy than random action alone for low dimensionality spaces. On higher dimensionality inputs, oscillation is observed leading to significantly lower accuracy and much higher variability. PCA proved to be an effective means of feature extraction reducing the dimensionality of the input, increasing precision; however, it required a dataset to be generated from initial random action

An Exploratory Study of Social Factors Influencing Virtual Community Members\u27 Satisfaction with Avatars

Virtual communities that feature avatars are an emerging social software business model on the Internet. Avatars are Internet users\u27 graphical representations of themselves in virtual environments. This study investigates how virtual community members\u27 satisfaction with avatars is formed. We test a research model that proposes that social factors influence virtual community members\u27 satisfaction with avatars. We draw upon social presence theory, social comparison theory, and self-identity theory. Data from a field experiment (N=134) is analyzed using Structural Equation Modeling (SEM). Our results provide empirical support for our proposed model. We report that social factors affect virtual community members\u27 satisfaction with the use of avatars in virtual communities. Our intended contribution is to help both managers and academics understand aspects of customer behavior and customer satisfaction when using avatars in virtual communities. This study also presents suggestions for future research regarding the use of social software in business

DGR mutagenic transposition occurs via hypermutagenic reverse transcription primed by nicked template RNA.

Diversity-generating retroelements (DGRs) are molecular evolution machines that facilitate microbial adaptation to environmental changes. Hypervariation occurs via a mutagenic retrotransposition process from a template repeat (TR) to a variable repeat (VR) that results in adenine-to-random nucleotide conversions. Here we show that reverse transcription of the Bordetella phage DGR is primed by an adenine residue in TR RNA and is dependent on the DGR-encoded reverse transcriptase (bRT) and accessory variability determinant (Avd ), but is VR-independent. We also find that the catalytic center of bRT plays an essential role in site-specific cleavage of TR RNA for cDNA priming. Adenine-specific mutagenesis occurs during reverse transcription and does not involve dUTP incorporation, indicating it results from bRT-catalyzed misincorporation of standard deoxyribonucleotides. In vivo assays show that this hybrid RNA-cDNA molecule is required for mutagenic transposition, revealing a unique mechanism of DNA hypervariation for microbial adaptation

An evaluation of arborist handsaws

A review of the scientific literature reveals little research on the ergonomics of handsaws and no literature on the specific challenges of arborist saws (saws for cutting and pruning living trees). This study was designed to provide some insight into the effects of saw design and height of sawing activity on the biomechanical response of the upper extremity. Eighteen participants performed a simple sawing task at three different heights using six different arborist handsaws. As they performed this task, the electromyographic activity of several muscle groups of the forearm (flexor and extensor digitorum), arm (biceps brachii long and short heads) and shoulder girdle (posterior deltoid, infraspinatus and latissimus dorsi) were sampled. Also gathered were the wrist postures in the radial/ulnar plane at the beginning and ending of the sawing stroke, the time to complete the sawing task and a subjective ranking of the six different saws. The results show an interesting mix of biomechanical and subjective responses that provide insight into handsaw design. First, there were tradeoffs among muscle groups as a function of work height. As work height increased the biceps muscles increased their activation levels (∼19%) while the posterior deltoid activity decreased (∼17%) with the higher location. The results also showed the benefits of a bent handle design (average 21% reduction in ulnar deviation). The subjective responses of the participants generally supported the productivity data, with the saws demonstrating the shortest task completion time also being the ones most highly ranked

Observation of genuine three-photon interference

Multiparticle quantum interference is critical for our understanding and exploitation of quantum information, and for fundamental tests of quantum mechanics. A remarkable example of multi-partite correlations is exhibited by the Greenberger-Horne-Zeilinger (GHZ) state. In a GHZ state, three particles are correlated while no pairwise correlation is found. The manifestation of these strong correlations in an interferometric setting has been studied theoretically since 1990 but no three-photon GHZ interferometer has been realized experimentally. Here we demonstrate three-photon interference that does not originate from two-photon or single photon interference. We observe phase-dependent variation of three-photon coincidences with 90.5 \pm 5.0 % visibility in a generalized Franson interferometer using energy-time entangled photon triplets. The demonstration of these strong correlations in an interferometric setting provides new avenues for multiphoton interferometry, fundamental tests of quantum mechanics and quantum information applications in higher dimensions.Comment: 7 pages, 7 figure

Herders’ Attitude and Decision Making in Stocking Rates and Implication for Grassland Management in China

Overgrazing is widely acknowledged to be the main driver of grassland degradation. Governments seeking to address the grassland degradation problem have therefore focused on policies designed to reduce overgrazing. The Chinese government has implemented a series of policies with the aim of protecting the grasslands from more serious degradation. The efficacy of these policies has been questioned given that, since their introduction, stocking rates have remained high in many affected areas. It has been suggested that the government should enhance grassland monitoring and the punishment of overgrazing. Increasing penalties would reduce stocking rates, however that is likely to cause more social and economic problems. A survey of 1588 herders found that 40% consider the government should set a grass-animal balance rule and implement it strictly, and 30% think the government should only recommend a grass-animal balance rule for herders to follow，only 30% of herders were likely to set the stocking rate by themselves. An analysis of the survey data showed that household expenditure (food, house, clothing, medical expenses) was an important driver of overgrazing. Most herders depend upon their livestock for income; only 3% have a part-time job, compared to over 30% of all Chinese farmers. On average 70% of a herders’ income comes from livestock production and around 26% comes from subsidies. The contingent model developed found that, increasing subsidies with punishment for non-compliance, should reduce stocking rates and help maintain herders’ income, but not to the level required to alleviate poverty and unsustainable. We suggest that herders need training to improve their business skills so they can move from a focus on survival to one where optimising production and better marketing, are the aims of their livestock enterprise. Demonstration farms need to be part of this training

A new topology of the HK97-like fold revealed in Bordetella bacteriophage by cryoEM at 3.5 A resolution.

Bacteriophage BPP-1 infects and kills Bordetella species that cause whooping cough. Its diversity-generating retroelement (DGR) provides a naturally occurring phage-display system, but engineering efforts are hampered without atomic structures. Here, we report a cryo electron microscopy structure of the BPP-1 head at 3.5 Å resolution. Our atomic model shows two of the three protein folds representing major viral lineages: jellyroll for its cement protein (CP) and HK97-like ('Johnson') for its major capsid protein (MCP). Strikingly, the fold topology of MCP is permuted non-circularly from the Johnson fold topology previously seen in viral and cellular proteins. We illustrate that the new topology is likely the only feasible alternative of the old topology. β-sheet augmentation and electrostatic interactions contribute to the formation of non-covalent chainmail in BPP-1, unlike covalent inter-protein linkages of the HK97 chainmail. Despite these complex interactions, the termini of both CP and MCP are ideally positioned for DGR-based phage-display engineering. DOI: http://dx.doi.org/10.7554/eLife.01299.001