Operational research and simulation methods for autonomous ride-sourcing

Ride-sourcing platforms provide on-demand shared transport services by solving decision problems related to ride-matching and pricing. The anticipated commercialisation of autonomous vehicles could transform these platforms to fleet operators and broaden their decision-making by introducing problems such as fleet sizing and empty vehicle redistribution. These problems have been frequently represented in research using aggregated mathematical programs, and alternative practises such as agent-based models. In this context, this study is set at the intersection between operational research and simulation methods to solve the multitude of autonomous ride-sourcing problems. The study begins by providing a framework for building bespoke agent-based models for ride-sourcing fleets, derived from the principles of agent-based modelling theory, which is used to tackle the non-linear problem of minimum fleet size. The minimum fleet size problem is tackled by investigating the relationship of system parameters based on queuing theory principles and by deriving and validating a novel model for pickup wait times. Simulating the fleet function in different urban areas shows that ride-sourcing fleets operate queues with zero assignment times above the critical fleet size. The results also highlight that pickup wait times have a pivotal role in estimating the minimum fleet size in ride-sourcing operations, with agent-based modelling being a more reliable estimation method. The focus is then shifted to empty vehicle redistribution, where the omission of market structure and underlying customer acumen, compromises the effectiveness of existing models. As a solution, the vehicle redistribution problem is formulated as a non-linear convex minimum cost flow problem that accounts for the relationship of supply and demand of rides by assuming a customer discrete choice model and a market structure. An edge splitting algorithm is then introduced to solve a transformed convex minimum cost flow problem for vehicle redistribution. Results of simulated tests show that the redistribution algorithm can significantly decrease wait times and increase profits with a moderate increase in vehicle mileage. The study is concluded by considering the operational time-horizon decision problems of ride-matching and pricing at periods of peak travel demand. Combinatorial double auctions have been identified as a suitable alternative to surge pricing in research, as they maximise social welfare by relying on stated customer and driver valuations. However, a shortcoming of current models is the exclusion of trip detour effects in pricing estimates. The study formulates a shared-ride assignment and pricing algorithm using combinatorial double auctions to resolve the above problem. The model is reduced to the maximum weighted independent set problem, which is APX-hard. Therefore, a fast local search heuristic is proposed, producing solutions within 10\% of the exact approach for practical implementations.Open Acces

A Review of Current Research Trends in Power-Electronic Innovations in Cyber-Physical Systems.

In this paper, a broad overview of the current research trends in power-electronic innovations in cyber-physical systems (CPSs) is presented. The recent advances in semiconductor device technologies, control architectures, and communication methodologies have enabled researchers to develop integrated smart CPSs that can cater to the emerging requirements of smart grids, renewable energy, electric vehicles, trains, ships, internet of things (IoTs), etc. The topics presented in this paper include novel power-distribution architectures, protection techniques considering large renewable integration in smart grids, wireless charging in electric vehicles, simultaneous power and information transmission, multi-hop network-based coordination, power technologies for renewable energy and smart transformer, CPS reliability, transactive smart railway grid, and real-time simulation of shipboard power systems. It is anticipated that the research trends presented in this paper will provide a timely and useful overview to the power-electronics researchers with broad applications in CPSs.post-print2.019 K

Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems

The electrical power system is undergoing a revolution enabled by advances in telecommunications, computer hardware and software, measurement, metering systems, IoT, and power electronics. Furthermore, the increasing integration of intermittent renewable energy sources, energy storage devices, and electric vehicles and the drive for energy efficiency have pushed power systems to modernise and adopt new technologies. The resulting smart grid is characterised, in part, by a bi-directional flow of energy and information. The evolution of the power grid, as well as its interconnection with energy storage systems and renewable energy sources, has created new opportunities for optimising not only their techno-economic aspects at the planning stages but also their control and operation. However, new challenges emerge in the optimization of these systems due to their complexity and nonlinear dynamic behaviour as well as the uncertainties involved.This volume is a selection of 20 papers carefully made by the editors from the MDPI topic “Optimisation, Optimal Control and Nonlinear Dynamics in Electrical Power, Energy Storage and Renewable Energy Systems”, which was closed in April 2022. The selected papers address the above challenges and exemplify the significant benefits that optimisation and nonlinear control techniques can bring to modern power and energy systems

Techno-economic assessment and optimisation of a carnot battery application in a concentrating solar power plant.

Thesis (MEng)--Stellenbosch University, 2022.ENGLISH SUMMARY: The techno-economic assessment as well as optimisation of a Carnot battery application in a parabolic trough concentrating solar power (CSP) plant is conducted. A computational techno-economic model of the Carnot battery is developed and verified with reasonable accuracy. The model entails electric resistive heating integrated with the thermal energy storage of the CSP plant. During solar thermal charge cycles, potentially abundant solar photovoltaic grid electricity is stored as thermal energy. Stored energy is discharged during periods of lower solar thermal supply to promote baseload power generation. A fundamental techno-economic understanding of the CSP Carnot battery is developed. Charging costs, together with low round-trip efficiencies, can inhibit the system’s economic viability. Nonetheless, the CSP plant displays increased potential for baseload power generation once retrofitted. This enhances its continuity of inertial support and reduces intermittent power generation. The standard solar-thermal charge-discharge cycles are inherently suited for ideal time-shifting of surplus electricity, more so during summer than winter. Multi-objective optimisation determines the optimum thermal energy storage capacity for heater integration. The mathematical significance of optimisation results is explored via Pareto fronts and energy-cost curves. In general, the storage capacity is inversely related to the installed heater capacity at which the latter overcharges energy. At this point, electrical energy is stored at the expense of underutilised solar thermal energy. Plants with larger solar fields are more prone to overcharge, yielding less capacity for optimally allocated heaters. This could present a barrier to technical synergy.AFRIKAANS OPSOMMINGS: Die tegno-ekonomiese assessering sowel as optimisering van ’n Carnot-battery toepassing in ’n paraboliese trog gekonsentreerde sonkragaanleg (GSK) word uitgevoer. ’n Tegno-ekonomiese berekeningsmodel van die Carnot-battery word ontwikkel en as redelik akkuraat bevestig. Die model behels elektriese weerstandsverhitters wat met die aanleg se termiese energie-opbergingseenheid geïntegreer word. Vanuit die kragnetwerk word moontlike oortollige fotovoltaïese elektrisiteit tydens sontermiese laaisiklusse as termiese energie gestoor. Hierdie energie word tydens periodes van sontermiese onderverskaffing ontlaai, met die doel om basislading elektrisiteit op te wek. ’n Fundamentele tegno-ekonomiese begrip van die GSK Carnot-battery word ontwikkel. Laaikostes en lae omskakelingsdoeltreffendheid kan ekonomiese lewensvatbaarheid inhibeer. As ’n Carnot-battery toon die GSK-aanleg nietemin meer potensiaal vir basislading elektrisiteitsopwekking. Dit bevorder die kontinuïteit van traagheidsondersteuning en verminder afwisselende kragopwekking. Die standaard sontermiese laai-ontlaai siklusse is inherent gepas vir ideale tydverskuiwing van oortollige energie, veral meer tydens somer as winter. Meerdoelige optimisering word benut om die optimale termiese energie stoorkapasiteit vir verhitter toevoeging te bepaal. Die wiskundige betekenis van optimiseringsresultate word deur middel van Pareto-fronte en energie-koste kur-wes verken. In die algemeen is die stoorkapasiteit omgekeerd eweredig aan die verhitterkapasiteit waarby laasgenoemde energie oorlaai. Hier word elektriese energie ten koste van onderbenutte sontermiese energie gestoor. Aanlegte met groter sonvelde is meer vatbaar vir oorlading en bevat minder kapasiteit vir optimale verhitter integrasie. Hierdie eienskap kan tegniese sinergie bemoeilik.Master

1992 NASA/ASEE Summer Faculty Fellowship Program

For the 28th consecutive year, a NASA/ASEE Summer Faculty Fellowship Program was conducted at the Marshall Space Flight Center (MSFC). The program was conducted by the University of Alabama and MSFC during the period June 1, 1992 through August 7, 1992. Operated under the auspices of the American Society for Engineering Education, the MSFC program, was well as those at other centers, was sponsored by the Office of Educational Affairs, NASA Headquarters, Washington, DC. The basic objectives of the programs, which are the 29th year of operation nationally, are (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate and exchange ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of the participants' institutions; and (4) to contribute to the research objectives of the NASA centers

A State-of-the-Art Review on Heat Extraction Methodologies of Photovoltaic/Thermal System

One of the critical emerging branches of solar technology is photovoltaic/thermal (PV/T) systems that amalgamate solar collectors and solar photovoltaic panels into a unit to produce heat and electricity from stochastic solar insolation. In sunny countries, the conversion efficiency ( η ) reduces due to the elevated temperature of solar cells because solar panels absorb a sizeable portion of solar insolation as heat. The critical function of PV/T is to minimize the temperature of photovoltaic modules and enhance their electricity production with yielded thermal energy used for other applications. Energy and exergy are two essential aspects of examining an energy system. The exergy analysis of such systems is of great concern because it works on the quality of energy. The energy and thermal and electrical efficiencies are enhanced by applying proper cooling media in the PV/T. This brief provides a comprehensive review of the air, fluids, and PCM-based cooling media of the PV/T systems. A thorough review of various recently published research in the heat extraction methodologies of PV/T systems has been incorporated into this study. Based on the rigorous review, future recommendations for the implementation of cooling medias are also included in this study. The vivid tabular analysis of heat extraction methodologies provides a proper guideline for the researchers. This review work will provide a deep insight into the investigated area for the industrialists and researchers working in the field of PV/T technology