18 research outputs found

    Effects of rotation on stellar spectra

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    ix, 69 leaves : col. ill. ; 29 cm.Includes abstract.Includes bibliographical references (leaves 67-69).Models have been produced to study the spectral energy distributions (SEDs) and absorption lines for rapidly rotating B stars. A fully implicit 2D stellar structure and evolution code was used to generate the rotating structure models. The code PHOENIX was then used to generate non-LTE stellar atmospheres and spectra. An integrator code, CLIC, then created SEDs and absorption lines as viewed from 10 inclination angles. The SEDs were used to create a series of inclination curves, defining a rotating star's possible positions on an HR diagram. It was found that uniform rotation creates a relatively straight line parallel to the main sequence. The line extends in length and moves away from the main sequence as the rate of rotation increases. Differential rotation creates a more extended and complex inclination curve. The effects of differential rotation on line profiles was explored. It was found that differential rotation creates a very different profile from uniform rotation, especially when viewed closer to the pole. Both the SEDs and line profiles were used to test the limits of von Zeipel's theorem against more realistic models. The SEDs produced appreciably different inclination curves for rotation rates greater than around 0.76 of critical rotation. The difference in the line profiles produced by von Zeipel's models and the more realistic models were small

    Retrofit information challenges and potential solutions: Perspectives of households, retrofit professionals and local policy makers in the United Kingdom

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    Rapidly scaling up energy retrofit for existing buildings is critical to help meet climate targets. Information is frequently identified as a key barrier to residential retrofit. This paper explores the role of information sharing in accelerating retrofit market transformation, through interviews and photo elicitation with homeowners (N = 9) and two workshops with stakeholders (N = 33) in a local authority retrofit project in Gloucestershire (UK). Findings are thematically analysed and suggestions for future local and national policy action are identified. The research finds that even for engaged, knowledgeable homeowners, accessing appropriate information is still a significant retrofit barrier. Two themes around the nature of information and information delivery are identified and key issues include information overload, a lack of context-specific information and in-person engagement, and a need for trustworthy, local information sources. Local authorities have potential to act as trusted intermediaries for structured, relevant retrofit information but require support from national governments to increase capacity and resources at local levels. National governments also have a critical role in providing clear and consistent messaging and leadership on the importance and benefits of retrofit. Policies around financial incentives are not sufficient alone and must be accompanied by strategies to overcome informational and other barriers if retrofit is to be accelerated in this decisive decade for climate action

    Lessons for the UK Green Deal from the US BBNP

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    <p>How can programme design and strategy drive the decision actually to undertake retrofit upgrades? The US Better Buildings Neighborhood Program (BBNP) and the UK Green Deal both represent ambitious efforts to drive domestic retrofit markets. These programmes are compared and the differences in their conversion rates explored in the context of marketing, outreach and workforce engagement strategies. The impact of financial incentives is also explored. This paper supports the consensus that the US BBNP was successful against most of its stated objectives. The UK Green Deal, while slow to start, was gaining momentum before it was effectively ended. Semi-structured interviews with programme organizers give evidence that the Green Deal would have benefited from a more active approach to marketing and outreach, specifically emphasizing the distinction between the two. Marketing generates interest, but local outreach through word of mouth and personal referrals is needed to drive upgrades. The Green Deal did not sufficiently engage the workforce through an ongoing communication strategy and should have better facilitated both technical and non-technical skills development. The interest rate of the Green Deal is shown to be but one factor influencing participation, and can be effectively balanced through programme design in other areas.</p

    Review of Intelligent Control Systems for Natural Ventilation as Passive Cooling Strategy for UK Buildings and Similar Climatic Conditions

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    Natural ventilation is gaining more attention from architects and engineers as an alternative way of cooling and ventilating indoor spaces. Based on building types, it could save between 13 and 40% of the building cooling energy use. However, this needs to be implemented and operated with a well-designed and integrated control system to avoid triggering discomfort for occupants. This paper seeks to review, discuss, and contribute to existing knowledge on the application of control systems and optimisation theories of naturally ventilated buildings to produce the best performance. The study finally presents an outstanding theoretical context and practical implementation for researchers seeking to explore the use of intelligent controls for optimal output in the pursuit to help solve intricate control problems in the building industry and suggests advanced control systems such as fuzzy logic control as an effective control strategy for an integrated control of ventilation, heating and cooling systems

    Designing an ‘optimal’ domestic retrofit programme

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    <p>The US Better Buildings Neighborhood Program (BBNP) consisted of 41 different versions of thermal retrofit programmes with a common structure and objectives. This created a natural experiment in thermal retrofit programme design. This paper uses qualitative interviews with programme organizers measured against third-party programme performance data to create a model of 14 programme steps that were common to all BBNP grantees. This model uses the experiences of programme organizers to define best-practice principles associated with each programme step. Five themes emerge from the programme steps: (1) programme design: local market features and suitable programme structures; (2) marketing and outreach: the processes of creating awareness versus personal engagement – how community-based social marketing is a key strategy in driving demand; (3) workforce engagement: the skills gaps across the supply chain; (4) financial incentives: the merits of grants versus loans – how to use them in combination; and (5) data and evaluation: best-practice techniques for both programme evaluation and enabling iterative programme adjustments. These principles create a template for an ‘optimal’ programme model for retrofit programmes with stated objectives similar to the US BBNP. The potential and limitations in extrapolating this model to UK retrofit markets are considered.</p

    Grants versus Financing for Domestic Retrofits: A Case Study from Efficiency Maine

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    Any attempts to limit the impacts of climate change must maximize the potential for energy efficiency in existing dwellings. Retrofitting the existing stock of aging and inefficient dwellings is a challenge on many fronts. A number of programs have been put in place to encourage domestic retrofits by reducing barriers such as the upfront costs and access to capital. While many such programs are delivering positive results, there is much uncertainty regarding what constitutes success, as well as the long term cost effectiveness of various approaches. Geographic, demographic, and programmatic differences frequently cloud the ability to make comparisons across programs. This work examines a case study from Efficiency Maine in the United States, in which a grant program transitioned to a financing program. The grant program was highly popular and delivered significant energy savings, but used considerable public funds. The financing program reaches fewer homeowners, but delivers larger retrofit projects per homeowner, and leverages private investment with smaller public expenditures. Which of the two programs can be considered more successful? This work explores the methods of assessing this question and offers the author’s perspectives
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