Performance prediction on a novel solar assisted heat pump with hybrid Fresnel PV plus TEG evaporator
ENERGY CONVERSION AND MANAGEMENT
Authors: Song, Zhiying; Ji, Jie; Cai, Jingyong; Li, Zhaomeng; Gao, Yuhe
Abstract
Aiming to make full use of the heat on PV, a novel solar assisted heat pump with hybrid Fresnel PV plus TEG evaporator (FPV/TEG/SAHP) is proposed and the performance is predicted in this paper. As we all know, most irradiation is transformed to heat as the solar irradiation is absorbed by the PV, resulting in high temperature, while the evaporator of the heat pump could provide a lower temperature. Particularly, TEG could complete the conversion from heat to electrical energy under high temperature difference. In this case, we proposed a novel hybrid system, predicted the performance and discussed the influence of solar irradiation, ambient temperature and condensing water temperature. Results show that by adding TEG between PV and evaporator, the heat on PV can be transformed to electrical energy as a second electrical generation, which can complete a maximum lift of 43.77 W electrical energy and increase the electrical efficiency by 1.40% under 800 W/m(2) and the COPPVT of the hybrid system can reach 7.89. Besides, for the FPV/TEG evaporator the thermal efficiency, photovoltaic efficiency and the photovoltaic/thermal efficiency could achieve 142.96%, 28.11% and 216.41% respectively under 300 W/m(2) irradiation, which all decrease with the increase of the solar irradiation. Additionally, the exergy efficiency of the hybrid system has optimal irradiation varying with ambient temperature or water temperature.
Severity of White Matter Hyperintensities and Effects on All-Cause Mortality in the Mayo Clinic Florida Familial Cerebrovascular Diseases Registry
MAYO CLINIC PROCEEDINGS
Authors: Hasan, Tasneem F.; Barrett, Kevin M.; Brott, Thomas G.; Badi, Mohammed K.; Lesser, Elizabeth R.; Hodge, David O.; Meschia, James F.
Abstract
Objective: To compare all-cause mortality rates across the severity range of white matter hyperintensities (WMH). Patients and Methods: Between October 26, 2010, and October 5, 2017, the ongoing Mayo Clinic Florida Familial Cerebrovascular Diseases Registry prospectively enrolled 1011 diverse participants with and without cerebrovascular disease. T2-weighted magnetic resonance imaging of the brain was used to evaluate WMH in 455 participants using the Fazekas scale. Fazekas deep WMH (FD) and periventricular WMH (FPV) scores (0-3 points) were assigned on the basis of WMH severity. Kaplan-Meier survival analyses, Cox proportional hazards models, and estimated hazard ratios compared survival rates across FD and FPV categories. The Fisher exact and chi(2) tests evaluated the relationship of categorical variables, and the Kruskal-Wallis test measured the relationship of continuous variables across FD and FPV categories. All tests were performed at a P<.05 significance level. Results: Over a median follow-up of 3.06 years (range, 0.00-6.96 years), 96 deaths occurred. Higher FD scores corresponded to a higher likelihood of mortality (P<.001). Participants with an FD score of 3 were 4.69 (95% CI, 2.60-8.46) times more likely to die compared with those with an FD score of 0.Participants with higher FPV scores had a higher likelihood of mortality (P<.001). Participants with an FPV score of 3 were 7.04 (95% CI, 3.39-14.62) times more likely to die compared with those with an FPV score of 0. Once adjusted, age and baseline functional status explained most of the survival differences among the FD scores. Conclusion: Associations between all-cause mortality rates across the severity range of WMH were observed in the Registry. Further studies are warranted to understand the clinical importance of WMH in other clinical populations. (C) 2018 Mayo Foundation for Medical Education and Research