Risk assessment of power systems under a corrective control paradigm

Given the fact that the load is continuously growing as a sign of economic development and that renewable intermittent generation is growing rapidly driven by global climate change concerns and rising fuel costs, existing power systems need to be reinforced in order to accommodate the growing load and intermittent generation. Corrective control is a promising alternative solution to preventive control which, in this context, is represented by traditional system reinforcement of building more transmission facilities. The concept of reliability, existing reliability assessment methodologies and the latest development in this field were reviewed. The corrective control system was modelled as a common cause failure. New indices were derived and presented in the context of corrective control. They are Linear Weighed Reliability Index (LINWRI), Incremental Benefit of System Reinforcement (IBSR), Demand Response Incremental Cost Benefit (DRICB), and Voluntary Energy Curtailment Level (VECL).Three means of corrective control considered in this research are Demand Response (DR), Flexible AC Transmission Systems (FACTS) and Energy Storage (ES). One of the corrective control applications is the Active Management (AM) on distribution systems. The model of AM control system was developed and incorporated into chronological Monte Carlo simulation (CMCS). Different AM configurations and different reliability levels of AM with the same configuration have been proposed. Their impact on the ability to accommodate wind generation and on power system reliability was investigated. Economic assessment was also performed. A 'win-win' situation was achieved when a relatively reliable AM system is configured with Wind Generation Output Control (WGOC) function and the capacity of wind generation is adequate.DR models and the models of typical FACTS devices were reviewed and summarised. The Battery Energy Storage (BES) and Static Synchronous Compensator/BES (STATCOM/BES) models were developed based on the general structure of Energy Storage (ES) and a list of assumptions regarding their operation. Their models together with the model of the control system have been incorporated into CMCS which is applied as the reliability assessment methodology. The impact of DR, FACTS and ES on power system reliability was studied to a detailed level through test cases. The results have demonstrated the reliability improvement from corrective control compared to 'doing nothing at all' as well as the potential advantage of corrective control over traditional reinforcement in terms of cost effectiveness. The direction for future research related to this field was identified to be the investigation in network planning as an upstream project under a corrective control paradigm, the development of a more efficient and accurate nonlinear optimisation toolbox, the upgrade of DR models and FACTS models and the incorporation of transient analysis, etc.EThOS - Electronic Theses Online ServiceEngineering and Physical Science Research CouncilGBUnited Kingdo

Optimal Design of Hybrid Renewable Energy for Tanzania Rural Communities

Abstract Rural communities in developing countries lack access to electricity due to high costs of grid extension. This paper proposes a hybrid system of renewable energy (HRES) as solution. The HRES consists of solar, wind, and battery energy storage (BES). The village called Ngw’amkanga in Shinyanga region of Tanzania, East Africa is selected as a case study. An iterative method to determine the size of wind and solar photovoltaic (PV) generation required assuming a project life of 25 years at minimum annualised cost of the system ( ) is proposed. The project life time is fixed on the life span of the main component, solar PV at 25 years. The iteration is undertaken to meet the energy demand ensuring the BES is charged throughout the year. The required BES has three days of autonomy, and a maximum battery depth of discharge 50%. At minimum ACS, the HRES comprises only solar PV and BES, due to insufficient wind at this site. The levelised cost of energy ( ) of the HRES is 27.18 p/kWh, paid by the users. This is cheaper than the grid connected small power producers of Tanzania as discussed in the paper. Keywords: Renewable energy; wind energy generation; solar photovoltaic; annualised cost of the system; levelised cost of energ

Integration of hybrid organic-based solar cells for micro-generation

Despite the fact that the global photovoltaic (PV) market has grown rapidly during the last two decades, driven by global climate change concerns and public policy supports of renewable energy sources, a PV system is still considered an expensive alternative energy source when compared to other sources of electricity. Emerging organic-based PV solar cells may lead to significant price reductions of a PV system. Though, in the short and medium term, the lifetime, efficiencies and reliability are expected to be lower than current commercially available silicon wafer-based and mature inorganic thin film PV modules.A consortium formed by inter-disciplinary scientists and engineers between the University of Manchester and Imperial College London was set-up to investigate organic-based hybrid solar cells. Potential solar cell materials with higher resultant conversion efficiency in research, targeting lower costs than other PV technologies were developed. The designs investigated feature hybrid organic-based quantum dot (QD) solar cells topology.This research seeks to integrate this new PV technology concept into future PV micro-generators. The challenges faced by emerging PV technologies with regard to PV module lifetime, efficiency and cost / price were summarised. The uniqueness of this work is that, throughout this research, the issues for commercialisation of emerging PV technologies for micro-generation; in particular with regards to low efficiency, short lifetime and high efficiency degradation, and low-cost / price were extensively analysed in every aspect.The technical, economic and also environmental viability perspectives of emerging PV technologies for micro-generation were found. A wide range of models and / or methodologies were developed, extended or applied for the first time to PV technologies for micro-generation, with particular focus where possible on the hybrid organic-based QD solar cells. Lifetime-adjusted calculations and life cycle costing were used to determine cost boundaries and PV electricity costs. Life cycle environmental impacts were determined by the use of life cycle analysis. A mixed integer single / multi-objective optimisation program was developed to determine optimal, compromise and trade-off relationships on PV system characteristics. These PV system characteristics, which are analysed on a systems level included module efficiency, grid interconnection rating, solar fraction, energy storage capacities, annualised life cycle costs, project worth value and environmental CO2 impacts / benefit. Finally, PV technologies for micro-generation were ranked by the use of multi-criteria decision analysis. The results clarify, inform and suggest concepts for emerging PV technologies integration for micro-generation by providing boundaries, trade-offs and suggestions to all stakeholder including commercial, domestic and public bodies.The direction for future research in emerging PV technologies for micro-generation is identified to be the development of customer decision tools for diversified PV technologies, policy adaptation for the inclusion of emerging PV technologies and large-scale manufacturing investigations on emerging PV modules that makes use of an organic-based PV technology.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Characterisation of virtual power plants

The growing number of micro generation devices in the electrical network is leading many to consider that these devices can no longer be considered as fit and forget, but should instead be considered as having a demonstrable network impact which should be predicted and utilised. One of the techniques for considering the impacts of these devices is the Virtual Power Plant (VPP). The VPP is the aggregation of all the Distributed Generation (DG) connected into the network up to and including the connection voltage of the VPP, such that the cumulative power up the voltage levels can be seen in the single VPP unit, rather than across a broad spread of devices. One of the crucial tasks in characterising the VPP, developed in this work, is the ability to correctly predict and then aggregate the behaviour of several technology types which are weather driven, as a large proportion of DG is weather driven. Of this weather driven DG, some can only typically be dispatched with modification and the rest cannot be dispatched at all. The aggregation of the VPP as part of the electrical network is also developed, as the constraints of the network and the reliability of the network cannot be overlooked when considering the aggregation of the VPP. From a distribution network operator's (DNO) perspective, these characterisation models can be used to highlight problems in the network introduced by the addition of DG, but are also generally utilitarian in their role of predicting the power output (or negative load) found throughout the network due to DG. For a commercial agent interested in selling energy, these models allow for accurate predictions of energy to be determined for the trading period. A VPP agent would also be adversely affected by line failure in the network, leading to the development of an N-1 analysis based upon reliability rates of the network, which is used as the basis for a discussion on the impacts of single line failure and the mitigation available through feedback from the DNO.EThOS - Electronic Theses Online ServiceEPSRCGBUnited Kingdo

Improving the Load Estimation Process in the Design of Rural Electrification Systems

From MDPI via Jisc Publications RouterHistory: accepted 2021-08-27, pub-electronic 2021-09-03Publication status: PublishedFunder: European Commission; Grant(s): 810809The design of reliable and sustainable rural electrification systems relies on accurate prediction of the electrical load. This paper evaluates the current methods for load estimation and proposes an improved approach for load estimation for off-grid unelectrified rural communities that yields more accurate estimates. Improved accuracy is mainly due to better modelling of the influence of customer habits and gender on the estimated current and future load using the Markov chain process. A program was developed using MATLAB software to generate load profiles. The results show that gender considerations have a significant impact on load profiles and that the Markov chain process can suitably be used to determine year-to-year load profiles by incorporating the effect of changes in customer habits on the estimated load. The results from the case study on energy consumption in rural community households showed an increase in average daily consumption when gender was considered during load estimation. The peak consumption when gender was considered was about 50% higher than the value for when gender was not considered

Analyzing sub-optimal rural microgrids and methods for improving the system capacity and demand factors : filibaba microgrid case study examined

Solar energy kiosks in developing countries are commonly designed with battery storage as daytime energy production does not coincide with an evening peak consumption. Curtailment of excess solar energy production can occur when current load and battery storage charging is not high enough during peak solar generation hours. Valuation of the options for coping with this phenomena, after a system is already built, is important for kiosk operators to continue to improve technical and economic performance. Furthermore, little real-world data is available to analyze the extent and impact of this issue, much less the available decisions for the manager of such systems when it occurs. This paper analyzes some of these phenomena and the decisions that kiosk operators can make to improve such performance. Furthermore it analyzes data-sets from a 1.8 kW solar-battery energy kiosk in rural Filibaba, Zambia to determine the level of lost energy production/curtailing that occurred in that system. Finally, potential strategies, including demand response strategies are proposed to both increase as well as shift consumption to daytime hours and ultimately increase the capacity factor of the system. Such strategies could potentially help reduce the lost production of almost 1.7MWh that was witnessed in 11 months of system usage. These strategies could also increase the revenue of the system by approx. US$810 annually. Such strategies include pricing incentives, manual demand response, and system re-design options. In the general context of operations of rural solar kiosks, this work advocates for the need to continuously improve operational as well as hardware strategy based on field-evidence

Community engagement for the Voluntary Medical Male Circumcision (VMMC) program: an analysis of key stakeholder roles to promote a sustainable program in Zambia [version 2; peer review: 1 approved, 2 approved with reservations]

Background: Within the Voluntary Medical Male Circumcision (VMMC) programme, community engagement has been central in facilitating the acceptance of VMMC, especially in non-circumcising communities. We used the case of the development of community engagement plans for sustainability of VMMC in Zambia to illustrate diversity of stakeholders, their power, roles, and strategies in community engagement. Methods: Data were collected using document review, in-depth interviews (n=35) and focus group discussions (n=35) with community stakeholders, health workers, health centre committees, counsellors, teachers, community volunteers and parents/caregivers. Data were analysed using thematic analysis. The analysis was guided by the power and interest model. Results: Differences were noted between the rural and urban sites in terms of power/influence and interest rating of community stakeholders who could be involved in the sustainability phase of the VMMC response in Zambia. For example, in the urban setting, neighbourhood health committees (NHCs), health workers, leaders of clubs, community health workers (CHWs), radio, television and social media platforms were ranked highest. From this list, social media and television platforms were not highly ranked in rural areas. Some stakeholders had more sources of power than others. Forms or sources of power included technical expertise, local authority, financial resources, collective action (action through schools, churches, media platforms, other community spaces), and relational power.   Key roles and strategies included strengthening and broadening local coordination systems, enhancing community involvement, promoting community-led monitoring and evaluation, through the use of locally recognised communication spaces and channels, facilitating ownership of VMMC, and improving local accountability processes in VMMC activities. Conclusions: By consulting with the most relevant stakeholders, and considering community needs in programme development, the VMMC programme may be able to leverage the community structures and systems to reduce long term demand generation costs for VMMC and increase the acceptability and frequency of male circumcision

Differential Changes in Expression of Intestinal Antimicrobial Peptide Genes During Ascaris lumbricoides Infection in Zambian Adults Do Not Respond to Helminth Eradication

Background. Intestinal helminthiasis modulates immune responses to vaccines and environmental allergens. To explore the impact on intestinal host defense, we assessed expression of antimicrobial peptide genes, together with T cell subset markers and cytokines, in patients with ascariasis before and after treatment

Knowledge and Perceptions of Couples' Voluntary Counseling and Testing in Urban Rwanda and Zambia: A Cross-Sectional Household Survey

Most incident HIV infections in sub-Saharan Africa occur between cohabiting, discordant, heterosexual couples. Though couples' voluntary HIV counseling and testing (CVCT) is an effective, well-studied intervention in Africa, <1% of couples have been jointly tested.We conducted cross-sectional household surveys in Kigali, Rwanda (n = 600) and Lusaka, Zambia (n = 603) to ascertain knowledge, perceptions, and barriers to use of CVCT.Compared to Lusaka, Kigali respondents were significantly more aware of HIV testing sites (79% vs. 56%); had greater knowledge of HIV serodiscordance between couples (83% vs. 43%); believed CVCT is good (96% vs. 72%); and were willing to test jointly (91% vs. 47%). Stigma, fear of partner reaction, and distance/cost/logistics were CVCT barriers.Though most respondents had positive attitudes toward CVCT, the majority were unaware that serodiscordance between cohabiting couples is possible. Future messages should target gaps in knowledge about serodiscordance, provide logistical information about CVCT services, and aim to reduce stigma and fear