1,721,158 research outputs found
Lightweight, affordable, low power solar groundwater piston pump for rural remote regions.
Full text linkSolar photovoltaic powered groundwater pumping systems (SPWPS) are popular way of fetching water from boreholes in semi-arid areas in rural remote regions of most developing countries, where commercial water and electricity supply is out of reach. As the climate changes and the water table drops in such marginal regions, borehole depth is ever increasing into hundreds of metres below the ground surface. In a SPWPS, the required energy to fulfil water demand at a certain head is termed as the required hydraulic energy which is maintained by the pump unit of SPWPS. However, this acts ultimately as a load on the PV generator. The pump unit typically requires more power in order to maintain this hydraulic energy. For high head systems, groundwater piston pumps perform better than centrifugal pumps. A detailed literature review established that the current piston pumps have design limitations that act as load on the pump driver, which uses extra external and internal mechanical components. These include long piston drive rods, connecting rod, meshing gears, crossheads and crossways. This study put forth a new concept design of a groundwater piston pump optimised for power consumption using a scotch-yoke mechanism that excludes unnecessary components in the pump in order to conserve power usage. A mathematical model was built to support the claim of low power consumption by the new pump design. The widely-used computer aided design and finite element analysis (CAD/FEA) technique was used to ensure the structural viability of the concept design for high head application, which is based on material selection process. The study also compares the concept pump power consumption among existing photovoltaic (PV) operated pumps including piston rod and non-piston rod pumps. The developed mathematical model for power consumption finds significant power savings when compared with benchmarked low-power long-piston rod pumps. For example, with a 200 m head and 10.2 lpm flow demand, the proposed pump uses up to 22.4% and 7% less power than a pump that uses either a steel or glass fibre reinforced composite (GFRC - e.g. polyester) rod, respectively. Hydraulic efficiency calculations show an increase of up to 76.7% compared to 59.5% and 71.4% using steel and GFRC piston rods, respectively. Additionally, significant energy savings of 1505.7 Wh/day and 383.7 Wh/day are also found for daily pump operation compared to commercial steel and GFRC piston rods pumps, which consequently reduces the associated costs of PV panels. Design safety factors of the conceived pump for high head loads such as 200 m are evaluated using structural FEA. Material selection process based on performance indices is also carried out using the Cambridge Engineering Selector (CES Selector) program. The design of the proposed pump components was also optimised for mass, based on the fatigue life constraint of selected materials using a FE parametric approach coupled with material variation. The optimisation model developed in this study reduces the mass with optimum fatigue safety factors contrary to yield strength criteria, incorporating performance factors such as material cost and energy consumption. Stainless steel 'BioDur 108' was found overall to be the best contender, with optimised dimensions saving up to 29.39% of mass and material cost, along with 29.25% reduction in power consumption. In conclusion, the developed design for a groundwater piston pump in this study is optimised for low power consumption, along with structural suitability for SPWPS with high head requirements in rural remote areas. The pump design's structural adequacy is checked by FEA, material selection and design optimisation. The pump is also suitable for other locations depending on its structural ability to withstand loads with suitable materials
Gas diffusion transport characteristics and mathematical description of membrane systems with application for biogas upgrading.
Full text linkGreenhouse gas emissions (GHGs) and their effects have been a matter of global concern over the past decade. With growing energy demands to support developing economies, there has been a challenge of harnessing and utilizing renewable energy to meet these demands. However, despite the effect of global warming and the problems associated with it, the use of fossil fuels is still increasing. This problem has negatively impacted the climate, because the greenhouse gases produced by burning fossil fuels are increasing the concentration of carbon dioxide in the atmosphere. This study investigates a method that could remedy the situation - channelling biogas for use as a renewable energy source using membrane technology. The study began with observing the behaviour of biogas components as they travel selectively through the membrane support. This was done by conducting gas permeation tests to experimentally show how methane and carbon dioxide gases flow distinctively through ceramic membranes with different physico-chemical properties. Permeation tests were carried out under various operating conditions of temperature (up to 100 degrees Celsius) and pressure (up to 3 bar), using membranes of different pore sizes and characteristics, to ascertain the influence of these parameters on the membrane perm-selectivity. It was identified that the membranes were operating in a parallel flow regime and gas permeability was a function of viscous and Knudsen flow. A mass transfer model was developed to confirm that mass transfer conditions were not limiting in the boundary layer of the membrane surface. The model incorporates the influence of both structural and fluid properties in characterising diffusive and convective flow through the membrane. The analysis showed that under the same pressure drop across the membrane, the mass flux in porous membrane can be over four orders of magnitude higher than in a silica PDMS membrane with the similar thickness. Based on these findings, a dynamic approach was considered to modify the membrane by dip coating technique which allows easy manipulation of the deposition quantity and thickness, and it was possible to achieve a finely modified membrane with reduced pore size that improves the perm-selectivity. A methane selectivity of 1.6 was achieved, which is of the ideal Knudsen selectivity, with a 42% decrease in the CO2 concentration of the gas mixture. Permeation studies of the coated membrane shows that gas permeance is dependent on temperature with little impact due to pressure changes which can be attributed to a reduced impact of viscous flow due to the coating. The reduction in pore size due to coating was to a degree that significantly impacts the viscous flow contribution. The characterization results confirm this pore size reduction with the methane gas permeation rates reduced from 6x10-6 mol/m2sPa to 1x10-6 mol/m2sPa for the support and coated membrane respectively. A numerical method of estimating the pore size of the coated membrane was adopted based on the operating flow mechanism using a series model in conjunction with flow parameters through the layers. It was confirmed that the pore size of the coated membrane was sufficiently reduced to 36nm, which is in the dominant Knudsen range. Hence it was confirmed that, by modifying the membranes with this technique, it is possible to increase the selectivity of the methane by Knudsen diffusion. From this study, it can be established that a membrane's selectivity performance is dependent on an interplay of factors: (i) the structural effect that filters gases based on their interaction with pores; (ii) the thermodynamic equilibrium effect having to do with operating conditions; and (iii) the kinetic effect that considers the different diffusion rates of gas components, making them permeate quicker than others
Cuttings transport and hydraulics optimisation for underbalanced drilling (UBD) operations in concentric and eccentric, directional and extended reach wells.
Full text linkUnderbalanced drilling facilitates the effective control of wellbore pressures - amongst several other important advantages - when compared to conventional drilling technology. However, this involves the flow of multiphase fluids, which introduces additional complexities due to highly transient flow patterns, unpredictable wellbore hydraulics and increased tendency for the settling of drilled cuttings in the wellbore. An accurate prediction of fluid dynamics and cutting transport efficiency is required to achieve an effective pressure-management hole-cleaning operation. In this research, a theoretical, numerical and experimental study was performed to analyse and investigate cutting transport dynamics and wellbore hydraulics. The analytical study involved the development of several mechanistic models, which are valid for both single phase and two-phase flows in the concentric and eccentric annuli, both with and without inner pipe rotation. The study derives and presents Reynolds number and effective viscosity equations valid for annuli flow of both Newtonian and non-Newtonian Power law, Bingham plastic and Yield power law fluids. The study also used the solution of the continuity equation of motion for axial steady-state flows to formulate new Laminar and turbulent friction geometry parameter and friction factor equations, which take into account the combined effect of the fluid rheology, fluid circulation rate, pipe eccentricity and inner pipe rotation speed for the evaluation of the flow dynamics and pressure losses in the annuli. In addition, the study developed new flow gas-liquid pattern-dependent multi-layered models for the different cuttings transport mechanisms, valid for both horizontal and inclined annuli flows. Numerical computational fluid dynamics simulations were performed to discretise and solve the governing equations for fluid flow, using a finite volume mathematical approach to obtain velocity, viscosity and pressure fields for different input conditions. Furthermore, an experimental study was carried out to evaluate the interplay between the two-phase gas-liquid flow patterns and the major drilling parameters, and to investigate the influence on the cuttings and fluid flow dynamics in a horizontal and inclined drilling wellbore. Results showed that the effect of the drillpipe rotation on cuttings transport in the annuli is highly dependent on the fluid rheological properties, the drillpipe eccentricity, the wellbore inclination and fluid flow pattern. The annuli pressure gradient was found to be dependent on the fluid flow pattern and the prevailing cutting transport mechanism. The minimum requirements to clean an eccentric annulus is higher than that required for the concentric annulus. Furthermore, the local mixture properties and gas-liquid flow pattern of the fluid is strongly influenced by the inclination angle of the wellbore, which consequently influences annuli pressure losses and cutting transport dynamics. Although drillpipe rotation can improve cuttings transport through the annuli, the influence of drillpipe rotation on the cutting's movement in the two-phase gas-liquid drilling fluid is much less than that of the single-phase drilling fluid. Overall, a good match was found when the mathematical models were compared to the experimental data. The output of this research is very useful for implementing an efficient cutting transport operation, hydraulic program optimisation and effective wellbore control, particularly for managed pressure drilling operations
Design and performance evaluation of lead-free inorganic perovskite solar cells for addressing Nigeria's energy crisis.
Full text linkNigeria, the most populous nation in Sub-Saharan Africa with over 200 million people, faces a critical energy deficit, with approximately 45% of its population lacking access to electricity. To achieve energy sustainability, the country requires 160 GW of electricity. However, reliance on crude oil and natural-gas-fired power plants, which are often unavailable, has led to frequent energy crises. Despite this, Nigeria possesses vast untapped Renewable Energy (RE) resources, particularly solar radiation, with potential varying from 3.393 to 6.669 kWh/m2/day across its six geopolitical zones. While solar energy could significantly enhance Nigeria’s energy mix, its high initial cost poses a challenge to widespread adoption in developing economies. This research investigates the use of environmentally friendly, non-toxic, lead-free inorganic perovskite called potassium germinate chloride (KGeCl3) solar cells as a cost-effective and stable alternative to address Nigeria’s electricity challenges. Using finite element modelling in COMSOL Multiphysics, the study designs and evaluates the performance of a 3D inorganic Perovskite Solar Cell (PSC) and crystalline silicon (c-Si) solar cells. The proposed PSC structure, comprising FTO/C60/KGeCl3/PEDOT: PSS/Au, achieved a power conversion efficiency of 21.1%, with an output current density of 35.01 mA/cm2, an open-circuit voltage of 0.77 V, and a Fill Factor (FF) of 0.7642. For crystalline silicon, varying the absorber layer thickness influenced the power conversion efficiency, which reached 25% at 300 K with an open-circuit voltage of 0.64 V and a short-circuit current density range of 18–36.2 mA/cm2. The findings demonstrate the potential of KGeCl3 solar cells to enhance charge carrier mobility, reduce recombination losses, and offer high thermal and humidity stability. These results provide valuable insights for the feasible fabrication and design of high-efficiency, low-cost solar cells, offering a pathway to addressing Nigeria’s energy crisis
Building integrated photovoltaics in Ghana: aesthetics and policy.
Full text linkBuildings are known to account for over 40% of CO2 emissions globally, a number which is likely to increase if no feasible interventions are adopted. One sure way is the adoption of advanced solar applications such as building integrated photovoltaics (BIPV), intending to make buildings energy producers instead of mere energy consumers. BIPV has benign energy-generating capability and aesthetics concomitantly. Despite the seeming hype and significance of BIPV, its adoption has been relatively sluggish in developing countries. This study considers BIPV adoption in Ghana, focusing on aesthetics and policy. Considering the topography, climatic advantage, electricity supply challenges and advancement in the built environment, Ghana is a strategic location for BIPVs, especially as it serves as the gateway to Africa. Currently, there is no evidence of research on BIPV in Ghana, as the focus has been on regular building applied photovoltaics (BAPV). This thesis, therefore, adopts a mixed method by relying on a blend of quantitative and experimental analysis to investigate the prospects of BIPV in Ghana with a focus on aesthetics and policy. Survey questionnaires were administered to respondents to test their level of BIPV awareness, willingness to adopt solar energy and BIPV, aesthetic preferences and policy perspectives. An initial pilot study indicated a low level of awareness hence architectural visualisation (AV), and adverts were used to sensitise respondents ahead of the main survey. Awareness increased significantly (from 18% to 79.5%), indicating the impact of AV and advertising on BIPV diffusion in Ghana. In terms of aesthetic preferences, the respondents preferred bright colours and a variety of shapes in BIPV design. The study also indicates a high willingness to adopt BIPVs after simulating traditional Adinkra symbols in BIPV design. A further experiment was conducted using the screen-printing approach to print traditional Adinkra symbols on solar cells. It examined these symbols' benefits, printing limitations and characterisation, and suggested some enhancement techniques. The findings reveal that custom patterns for the top contact design of solar cells are achievable through direct printing. However, the outcome showed a lower efficiency due to conductivity issues. Challenges from the printing process, such as thicker line widths and imperfect metal ink bonding, high curing temperature led to shading losses and decreased efficiency. The research suggests optimizing printing parameters, addressing metal ink bonding issues, and minimizing the shading losses by thin line width at the top contact to enhance performance and efficiency. The key findings of this study reveal that BIPV has excellent prospects in Ghana, especially when customised with Adinkra symbols. Key policy areas are ensuring that measures are implemented to boost awareness and providing incentives/financial aid to increase adoption. This research intersects solar energy, aesthetics, architecture and policy in Ghana. It highlights the potential of BIPV to transform buildings into energy producers, enhancing both energy efficiency and visual appeal. The study addresses the low awareness of BIPV in developing countries, proposing customized designs using traditional Adinkra symbols to increase acceptance. By focusing on aesthetic preferences and policy, the study informs both green building technologies and policy frameworks aimed at reducing CO2 emissions and advancing sustainable architecture
Electric vehicles and their charging – in or out? User acceptance of bidirectional charging in Germany
Full text linkAn electric vehicles’ battery capacity can be used to store energy and redistribute it to the grid when connected to it. This concept of bidirectional charging is relatively new and has not been introduced widely. Bidirectional charging could be particularly important in times of high grid load. In the present study, it is examined from the perspective of EV users. Their acceptance determines whether bidirectional charging will be introduced and adopted in the future, particularly when charging at home. Through two focus group discussions with EV owners, one with home owners and one with tenants, we identifiy potentials and barriers from a user perspective. Given the design of our focus group discussions, we compare results for home owners and tenants qualitatively. Financial aspects are discussed as an incentive for use but also as a barrier if one needs to invest in new technology. The groups differed in how strongly they wished for governmental support in these issues. Tenants requested incentives for bidirectional charging more strongly. Additionally, acceptance of bidirectional charging was related to its compatibility with daily life, participants were more concerned to employ bidirectional charging when wishing to use their EV spontaneously. One key aspect for all participants was determining a minimum energy level that ought to remain in their vehicle. We find indications that home owners have a more holistic view of their vehicle within the context of their home energy system. As most home owners also had a private photovoltaic (PV-) system, they played a more active role in their own energy system. They also perceived greater personal advantages of bidirectional charging compared to tenants and might even be seen as early adopters. Tenants focussed more on their vehicle and worried about personal disadvantages, e.g. them or their vehicle being impacted negatively by bidirectional charging
Optimisation of electric vehicle battery size
Full text linkEnergy storage and battery technologies have taken centre stage in the race to meet the UK government target to ban new petrol and diesel cars by 2030. However, underlying key issues such as resource demand and negative public opinion must be solved before the high uptake of electric vehicles. The research conducted in this paper proposed viable solutions to these challenges through modelling of real driver data utilising an agent based modelling approach. Per month state of charge analysis confirmed that the current charging infrastructure in circulation will not accommodate the miniaturisation of electric vehicle battery size. Thus, an improved alternative charging infrastructure was proposed, which enabled the optimal battery size to be reduced by up to 40%. The users stop times were analysed to assign an optimal battery size based upon monthly driving behaviour concluding daily inner city drivers require a 30kWh battery and daily long distance drivers require a 40kWh battery. When decreasing the battery size by the proposed 40% there is a £2650.60 saving and a 6.4kg lithium demand decrease per battery when compared to the current average battery size
Impact of different charging methods on electric bus battery size and grid demand
Full text linkThis paper presents an agent-based model (ABM) that estimates battery size and electricity grid demand for bus charging infrastructure. The ABM considers four charging methods: overnight charging (ONC), end-line charging (ELC), occasionally fast charging (OFC), and wireless charging (WLC). The model accurately captures the energy consumption and charge load of battery electric buses (BEBs) by incorporating GPS coordinates, average speed, and temperature profiles. A case study is conducted on a bus route in Cardiff, UK, to showcase the functionality of the ABM. The results of simulations demonstrate significant reductions in electric bus battery sizes for different charging methods. For example, end-line charging reduces battery size by 235 kWh per bus compared to overnight charging. Occasionally fast charging and wireless charging achieve even lower capacities of 86 kWh and 69 kWh, respectively, however, these charging methods lead to higher and more fluctuating grid loads, resulting in a poor load factor. In summary, this ABM provides a practical tool for infrastructure planners. The case study illustrates its effectiveness in optimizing battery size and evaluating grid demand for BEB charging infrastructure. The findings provide critical directions for both bus operator shifting towards electrification of their fleets and city planners responsible for the deployment of related charging infrastructure
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