Review of high concentration photovoltaic thermal hybrid systems for highly efficient energy cogeneration

This is the final version.Available on open access from Elsevier via the DOI in this recordConcentrated photovoltaic/thermal hybrid systems are a combination of concentrated photovoltaics and photovoltaic/thermal hybrid systems which capture waste heat for later application. Higher concentrations lead to higher energy fluxes over smaller areas which is beneficial for several reasons. Firstly, less photovoltaic material is required, instead using relatively cheap optics. This allows more efficient types of PV material to be used effectively. Secondly, the concentrated heat flux easily allows for a high outlet temperature which in turn increases the applicability. Point focused systems have experimentally achieved cogeneration efficiencies of 86.47% (excluding system losses) and concentrations of over 1000 suns, but the technology still faces challenges. The design of the cooling system must be optimised to maximise both electrical and thermal efficiency. Furthermore, the optics and cell interconnections must mitigate the effects a non-uniform focal image for high electrical efficiencies. These challenges must be faced while minimising the thermal stresses the system undergoes to ensure the system has a substantial lifetime. This review provides an in depth understanding of the challenges and function of point focused concentrated photovoltaic/thermal systems. From the literature, it is clear more focus should be put on microchannel/impinging jet hybrid cooling systems for use in dense array concentrated photovoltaic/thermal systems. More physical experimentation is needed, especially full model systems which include the output image of the optics, along with consideration to alternative cooling fluids (particularly nanofluids).Engineering and Physical Sciences Research Council (EPSRC

Optical Losses and Durability of 4-Domed Optic for Concentrator Photovoltaics

This is the author accepted manuscript.The use of optical elements to focus light onto a smaller area of semiconductor material can enhance the cost effectiveness and electrical performance. Enabling ultrahigh concentration ratios for photovoltaic systems requires an optic bonded directly to the solar cell to further concentrate and homogenise the illumination, as well as to improve the acceptance angle. For many optical materials manufacture flaws are common, and difficult to prevent. An estimation of the effective external quantum efficiency of the receiver based on the material’s transmissivity tells us the effect of added absorptivity from manufacture defects. Evaluating the module under a solar simulator under various angles yields information on how scattered light changes the optic’s concentration ability. This study suggests sapphire has higher optical losses due to its higher refractive index compared to slygard184. Thus, the need for a higher refractive index material must be considered carefully and matched with anti-reflective coatings if needed. The effective concentration of slygard-184 notably suffers when flaws are present, dropping up to 48.2%. Further, the optimum angle is difficult to predict. Minor flaws could be deemed acceptable in performance when high acceptance angles are not the primary design requirement.Engineering and Physical Sciences Research Council (EPSRC

Outdoor experimental validation for ultra-high concentrator photovoltaic with serpentine-based cooling system

This is the final version. Available from Elsevier via the DOI in this record.With demand for renewable energy growing, concentrator photovoltaic thermal hybrids have great potential. Maximising concentration ratios through the deployment of multi-stage optics can yield high power outputs from multi-junction solar cells. To prevent damaging thermal stress and to enable extraction of thermal energy, a capable cooling system is necessary. The primary objective of this study is to maximise the effective concentration ratio over a solar cell and calibrate the system to optimise the energetic and exergetic efficiencies. The capability of the serpentine-based cooling system is investigated for each concentrator optic configuration. Originality is found in the presentation of the 3-stage optic, and the use of outdoor real-world experimental data to validate a computational model. This model uses both ray tracing, heat and mass transfer simulations to enhance the understanding of system operation and enable accurate prediction of performance under various conditions. Results show focal spot shape is more important than raw optical efficiency for electrical output, making the 3-stage optic superior to the other configurations in most regards. An effective concentration of over 1200 × is achieved. Higher exergetic efficiencies are consistently found in the double serpentine configuration, though variation does not exceed ±0.3% when only changing cooling system geometry.Engineering and Physical Sciences Research CouncilSaudi Arabia Culture Bureau in the U

Indoor experimental analysis of Serpentine-Based cooling scheme for high concentration photovoltaic thermal systems

This is the final version. Available on open access from Elsevier via the DOI in this record.Data availability statement: Data will be made available on request.High concentration photovoltaic thermal hybrids are expected to play an important role in meeting growing energy demands. When approaching concentrations over 1000 suns, a cooling system is needed to maximise both the thermal and electrical performance of the multi-junction solar cell without producing excessive parasitic losses. This study develops a novel simulation model to provide an in-depth understanding of the functionality of a concentrated photovoltaic thermal hybrid system with serpentine-based cooling systems. An ultra-high concentrator photovoltaic optic irradiance profile (peak effective concentration ratio: ∼1500 suns) is considered within the simulation model, which has been validated through indoor experimentation. The effectiveness of cooling is also evaluated through maximum thermal stresses generated in the multi-junction solar cell. The double serpentine design was deemed the highest performing, primarily because of the single serpentine’s excessive pressure drop. Copper as the heat sink material yielded superior performance because of its higher thermal conductivity. The maximum total exergetic efficiency achieved by the receiver was ∼ 10.9% with this configuration. Compared to some examples in the literature this value may seem low, however, it is more accurate due to the inclusion of a specific irradiance profile. All serpentine-based cooling systems could maintain the recommended operating temperature.Engineering and Physical Sciences Research Council (EPSRC)Saudi Arabia Culture Bureau, U

Work‒family interface in the context of career success: A qualitative inquiry

Work–family researchers are increasingly recognizing the need to expand their focus to advance the field. One population largely neglected by work‒family researchers is individuals who have been extremely successful in their careers. In addition, organizational career scholars have largely neglected the interplay between employees’ work and family lives. This study contributes to the work‒family literature by studying work‒family interface (WFI) in the context of career success. We sought to explore the lived experiences of 28 distinguished professors who are among the top 2‒5% scholars in their field, to provide an in-depth understanding of their WFI and the prominent factors affecting it over their careers. Our findings have theoretical implications for both work‒family and career success literature

Clean birth kits to improve birth practices: development and testing of a country level decision support tool

Background: Clean birth practices can prevent sepsis, one of the leading causes of both maternal and newborn mortality. Evidence suggests that clean birth kits (CBKs), as part of package that includes education, are associated with a reduction in newborn mortality, omphalitis, and puerperal sepsis. However, questions remain about how best to approach the introduction of CBKs in country. We set out to develop a practical decision support tool for programme managers of public health systems who are considering the potential role of CBKs in their strategy for care at birth. Methods: Development and testing of the decision support tool was a three-stage process involving an international expert group and country level testing. Stage 1, the development of the tool was undertaken by the Birth Kit Working Group and involved a review of the evidence, a consensus meeting, drafting of the proposed tool and expert review. In Stage 2 the tool was tested with users through interviews (9) and a focus group, with federal and provincial level decision makers in Pakistan. In Stage 3 the findings from the country level testing were reviewed by the expert group. Results: The decision support tool comprised three separate algorithms to guide the policy maker or programme manager through the specific steps required in making the country level decision about whether to use CBKs. The algorithms were supported by a series of questions (that could be administered by interview, focus group or questionnaire) to help the decision maker identify the information needed. The country level testing revealed that the decision support tool was easy to follow and helpful in making decisions about the potential role of CBKs. Minor modifications were made and the final algorithms are presented. Conclusion: Testing of the tool with users in Pakistan suggests that the tool facilitates discussion and aids decision making. However, testing in other countries is needed to determine whether these results can be replicated and to identify how the tool can be adapted to meet country specific needs

Managerial Work in a Practice-Embodying Institution - The role of calling, the virtue of constancy

What can be learned from a small scale study of managerial work in a highly marginal and under-researched working community? This paper uses the ‘goods-virtues-practices-institutions’ framework to examine the managerial work of owner-directors of traditional circuses. Inspired by MacIntyre’s arguments for the necessity of a narrative understanding of the virtues, interviews explored how British and Irish circus directors accounted for their working lives. A purposive sample was used to select subjects who had owned and managed traditional touring circuses for at least 15 years, a period in which the economic and reputational fortunes of traditional circuses have suffered badly. This sample enabled the research to examine the self-understanding of people who had, at least on the face of it, exhibited the virtue of constancy. The research contributes to our understanding of the role of the virtues in organizations by presenting evidence of an intimate relationship between the virtue of constancy and a ‘calling’ work orientation. This enhances our understanding of the virtues that are required if management is exercised as a domain-related practice

Union effectiveness: In Search of the Holy Grail

YesThis article revisits the concept of union effectiveness and proposes a conceptual model to inform its study and application. Previous conceptual and empirical work is examined to identify key strengths and weaknesses, and to relate the union effectiveness concept to union renewal and other key concepts. This leads to the proposal of a Goal-System framework that builds and improves on prior research