Design and performance analysis of concentrated photovoltaic cooling.

Kahagala Gamage, Upul - Associate SupervisorThe use of solar energy as a global energy source has increased over the past two decades. Photovoltaic cells, which utilise the sun to generate electricity, are a promising alternative to fossil fuels that contribute to climate change. However, the high intensity of concentrated solar radiation can cause overheating in photovoltaic cells, reducing their efficiency and power output. Researchers worldwide are improving cooling in concentrated photovoltaic cells (CPV) to enhance temperature uniformity and improve power output. Previous studies have demonstrated that pulsating flow can effectively enhance heat transfer in various fields, including electronics, mechanical engineering, and medicine. In this research, three flow patterns (continuous flow, uniform pulsating flow, and bio-inspired pulsating flow) were studied in both simulation and experimental designs. Two cooling designs were considered: the conventional design (C- Design) and the parallel design with baffles (W-B) and without baffles (Wout-B). With the implementation of 30 pulses per minute bio-inspired pulsating flow a reduction of 1.96% in solar cell temperature was observed when compared to continuous flow. This reduction in temperature was consistently observed across a range of flow rates from 0.5 to 2.5 L/m, employing the parallel Wout-B design. Notably, the bio-inspired pulsating flow shows better performance in comparison to uniform pulsating flow, as well as the conventional designs with continuous flow and uniform pulsating flow, resulting in notable improvements in cooling efficiency of 1.22%, 2.14%, and 4.00%, respectively. In terms of a direct comparison, the implementation of uniform pulsating flow in the parallel Wout-B design exhibited a maximum cooling improvement of 0.74% when contrasted with continuous flow. Furthermore, when assessing uniform pulsating flow against the C-design with uniform pulsating flow in the parallel Wout-B design, a noteworthy enhancement of 0.93% was observed. Remarkably, the C-design with uniform pulsating flow demonstrated a superior effectiveness of 1.90% when compared to the C-design with continuous flow.MSc by Research in Energy and Powe

Cooling of concentrated photovoltaic cells - a review and the perspective of pulsating flow cooling

This article presents a review to provide up-to-date research findings on concentrated photovoltaic (CPV) cooling, explore the key challenges and opportunities, and discuss the limitations. In addition, it provides a vision of a possible future trend and a glimpse of a promising novel approach to CPV cooling based on pulsating flow, in contrast to existing cooling methods. Non-concentrated photovoltaics (PV) have modest efficiency of up to around 20% because they utilise only a narrow spectrum of solar irradiation for electricity conversion. Therefore, recent advances employed multi-junction PV or CPV to widen the irradiation spectrum for conversion. CPV systems concentrate solar irradiation on the cell’s surface, producing high solar flux and temperature. The efficient cooling of CPV cells is critical to avoid thermal degradation and ensure optimal performance. Studies have shown that pulsating flow can enhance heat transfer in various engineering applications. The advantage of pulsating flow over steady flow is that it can create additional turbulence and mixing in the fluid, resulting in a higher heat transfer coefficient. Simulation results with experimental validation demonstrate the enhancement of this new cooling approach for future CPV systems. The use of pulsating flow in CPV cooling has shown promising results in improving heat transfer and reducing temperature gradients.Engineering and Physical Sciences Research Council (EPSRC): EP/T006315/1. Petroleum Technology Development Fund, Nigeria

Biogas Production: A Comparative Study of Chicken Droppings (Poultry Waste) and Banana Peels as the Gas Source

Biogas has been increasingly used in generating energy in the deregulated energy market. Biogas production has been identified as a sustainable approach to mitigating the effect of climate change and global warming. This work conducted a comparative study of biogas production from poultry waste (Chicken droppings) and banana peels under the same operating conditions. 100g of each sample was mixed with 200cm³ of water for poultry waste and 400cm³ for banana peels and loaded into four cylindrical digesters. Each container was shaken to ensure a homogenous mixture and fermentation. Biogas was measured using the water displacement method for 14 days at an average of 27.7oC. The pH, temperature, and concentration were observed to affect biogas production. Within 14 days, 1556cm3 and 755cm3 of biogas were produced for poultry waste and banana peels. This shows that poultry waste produces more biogas than banana peels. Hence, it can be deduced that poultry waste is potentially a more promising feedstock for biogas production than banana peels; and can provide an alternative energy source for the local community in place of the conventional fossil fuel source

A scalable optical meta-surface glazing design for agricultural greenhouses

Optical meta-surfaces allow controllable reflection and transmission spectra in both optical and infrared regions. In this study, we explore their potential in enhancing the performance of low-emission glazing designed for improved energy efficiency, for agricultural greenhouses in cold climates. The low-emission glazing employs thin film optics to retain heat by allowing solar radiation while reflecting radiation emitted by room-temperature objects. The incorporation of metamaterials that can be scalably manufactured and designed for capturing solar energy in the mid-infrared spectrum, offers an opportunity to further enhance the glazing's energy efficiency. Based on existing literature, the finite difference time domain (FDTD) method and the transfer matrix method are utilised to propose a metamaterial structure, with spherical silver nanoparticles and thin-films. We compare the performance of this proposed design against existing materials. The outcome of this study offers insights into the potential of metamaterials in optimizing the energy efficiency of cold-climate agricultural greenhouses

Advancing hydrogen: a closer look at implementation factors, current status and future potential

This review article provides a comprehensive analysis of the hydrogen landscape, outlining the imperative for enhanced hydrogen production, implementation, and utilisation. It places the question of how to accelerate hydrogen adoption within the broader context of sustainable energy transitions and international commitments to reduce carbon emissions. It discusses influencing factors and policies for best practices in hydrogen energy application. Through an in-depth exploration of key factors affecting hydrogen implementation, this study provides insights into the complex interplay of both technical and logistical factors. It also discusses the challenges of planning, constructing infrastructure, and overcoming geographical constraints in the transition to hydrogen-based energy systems. The drive to achieve net-zero carbon emissions is contingent on accelerating clean hydrogen development, with blue and green hydrogen poised to complement traditional fuels. Public–private partnerships are emerging as catalysts for the commercialisation of hydrogen and fuel-cell technologies, fostering hydrogen demonstration projects worldwide. The anticipated integration of clean hydrogen into various sectors in the coming years signifies its importance as a complementary energy source, although specific applications across industries remain undefined. The paper provides a good reference on the gradual integration of hydrogen into the energy landscape, marking a significant step forward toward a cleaner, greener future

Harnessing energy for wearables: a review of radio frequency energy harvesting technologies

Wireless energy harvesting enables the conversion of ambient energy into electrical power for small wireless electronic devices. This technology offers numerous advantages, including availability, ease of implementation, wireless functionality, and cost-effectiveness. Radio frequency energy harvesting (RFEH) is a specific type of wireless energy harvesting that enables wireless power transfer by utilizing RF signals. RFEH holds immense potential for extending the lifespan of wireless sensors and wearable electronics that require low-power operation. However, despite significant advancements in RFEH technology for self-sustainable wearable devices, numerous challenges persist. This literature review focuses on three key areas: materials, antenna design, and power management, to delve into the research challenges of RFEH comprehensively. By providing an up-to-date review of research findings on RFEH, this review aims to shed light on the critical challenges, potential opportunities, and existing limitations. Moreover, it emphasizes the importance of further research and development in RFEH to advance its state-of-the-art and offer a vision for future trends in this technology

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

Background: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population