1. Performance and Test (P&T)
2. Power Plant Condition Monitoring (PPCM)
3. Plant Life Cycle Management (LCM)
4. Component Management (CLCM)
5. Environmental Protection (ENV)
6. Smart Grid
7. Power System Simulation (PSS)
… at 8 Centres of Specialisation
■ Energy Efficiency at the University of Cape Town
■ Combustion Engineering at the University of the Witwatersrand
■ Emissions Control at North-West University
■ Material Science at the University of Cape Town
■ Asset Management at the University of Pretoria
■ High Voltage Engineering AC at the University of the Witwatersrand
■ High Voltage Engineering DC at the University of Kwa-Zulu-Natal
■ Renewable Energy at Stellenbosch University
Energy Efficiency at the University of Cape Town
It is the aim of the SC in Energy Efficiency to develop skills and tools to improve the availability, reliability and environmental impact of Eskom power plants by increasing the efficiency of energy production. This will be achieved by focusing on complete plant process flow modelling and analysis.
Modelling will focus on the Rankine water-steam cycle, which is the main process common to more than 90% of all power plants in South Africa as well over 70% worldwide. The models will include all necessary control and instrumentation logic to enable steady-state and transient design analysis as well as normal and incidental operation analysis. The models will be physics-based rather than empirically based, using fundamental thermodynamic principles.
The modelling will be done in three different regimes, namely, steady state, transient state and component level. The steady-state models will mainly focus on plant design and normal operation while the transient models will focus on transitions from one steady condition to the next as well as various control schemes. Refined component models of the fluid-structure interaction of some specific components will be developed and integrated in the steady-state or transient-state models, where needed.
It is envisaged that the developed plant models will serve as the integrator/federator for work done by other SCs within the EPPEI programme. Plant model outputs will serve as inputs to SCs requiring thermohydraulic process conditions. Further integration can be done with grid models developed at the two High Voltage Engineering SCs to eventually have a complete macrosystem model that could predict any scenario response on the national grid and its local influence on plants in terms of participation, availability and remaining life.
Finally, key plant performance indicators identified by this SC could be fed back to the online monitoring systems to better operate and maintain the current plants. The plant model will serve as a high-fidelity simulator to train operators, technicians and engineers in efficient use and design of power plants. This will improve the root cause analysis capability and the ability to conduct cost-effective trade-off studies of plant modifications or improvement.
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Combustion Engineering at the University of the Witwatersrand
Measurement and instrumentation equipment installed on key components in the full combustion systems is quite limited and sometimes inaccurate in existing plants. Additionally, control devices have drawbacks and inaccuracies, which complicate control of the operation set points of components and sometimes control of total boiler behaviour. It is, therefore, difficult to monitor the combustion system online for early detection and diagnosis of abnormal situations that cause unreliable and inefficient operation.
Local environmental standards require implementation of NOx reduction technology in all existing and new-build plants. The low-NOx burner operation requires accurate coal and air flow measurements for optimal control due to its operational limits and the variations in coal quality and the need for load shifting of Eskom plant.
An urgent need exists to improve measurement and online monitoring of:
- coal mass flow and coal quality, especially ash and moisture content;
- milling plant performance to control fuel/air ratios, particle size, and mass flows;
- air streams to wind boxes, burners, and air heaters;
- heat transfer from flue gases to the air and water-steam circuit.
The SC strives to improve understanding of local coal impact and predicting of the effects on coal-fired power plant. Research is focused on current Eskom requirements to:
- improve and grow a repository of skills and knowledge of existing plant;
- create skills and tools to design, operate, and maintain plants;
- ensure that future plants are cleaner, available, reliable, efficient, and safe (CARES);
- achieve world-class output in combustion engineering-related technologies;
- retain a highly skilled engineer base in Eskom to create a healthy fleet for current and future power generation using state-of-the-art technology;
- host the combustion system design intellectual property purchased by Eskom;
- attract local manufacturers to build and supply burners for the local market;
- provide a continuously improved bouquet of experimental facilities in heat transfer, combustion technology, and thermodynamics.
To achieve its goals, the SC embarks on an applied research method ranging from fundamental research to pilot-scale and full-scale testing, which is then taken to implementation and further development, as outlined in the research flow chart.
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Emissions Control at North-West University
Eskom operates coal-fired power stations, which emit approximately 230 million tons of CO2 and more than one million ton of SO2 into the atmosphere annually. International pressure and local legislation controlling pollutant emissions such as SO2, particulates, and NOx have become more stringent over the past decade.
Emissions control must be considered to optimise and, if necessary, modify old technology to perform beyond design capabilities for the existing fleet and ensure that plant emissions meet increasingly strict standards that have been set by government for new power stations currently under construction. The primary focus of this SC is (i) to understand existing emissions of SO2, NOx, CO2, Hg, and particulates into the local atmosphere from power stations and (ii) to research and develop effective pollution mitigation technologies for the retrofitting of current processes.
In addition, the SC will work closely with Eskom and OEM technology providers to ensure that new power plants meet future emission requirements. The main objectives are, therefore, to ensure that Eskom is at the forefront of understanding emission mitigation technologies to limit the total emissions into the atmosphere from its processes without making electricity unaffordable within the South African context.
Smoke emission monitoring
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Material Science at the University of Cape Town
Power generating plants operate under highly demanding conditions that include high temperature, high stress, oxidation and corrosion, and complex tribological environments. In its most basic form, plant reliability is critically dependent on the integrity of a broad range of engineering materials (mostly metals) that make up structures, machines and systems within the plant.
Given the anticipated plant life-time, material integrity is expected to remain within the design performance for periods often in excess of 300 000 hours. Consequently, accurate characterisation of the material condition with regards to the damage level, and prediction of the damage that occurs during exposure to operating conditions, and concomitant loss in design properties, is necessary. The situation is further complicated by repair activities, particularly those involving welding, that alter existing materials and could disadvantage integrity. New material developments are required to handle these challenges and an industry must be developed to manage the use of new materials during design, construction and maintenance while existing plants continue to produce the most energy at the lowest cost.
The SC activities are directed towards the most urgent challenges in this field. The focus is on high temperature behaviour, fatigue and corrosion, with emphasis on materials utilised in power generation. Research will explore the influence of service operating environments on performance in order to:
- better predict life of engineering materials and components in power generating plant;
- optimise material selection for plant construction, improve manufacturing technologies including welding;
- improve the reliability of material and component integrity monitoring.
Seven focus areas have been identified by Eskom:
- physical metallurgy and metallography;
- structural integrity;
- high temperature behaviour (including creep and fatigue);
- environmental degradation (including corrosion);
- welding metallurgy and processes;
- materials modelling;
- non-destructive evaluation (NDE).
The principle research objective lies in integrity management of a range of materials within Eskom’s fleet. As such, the key aspects are monitoring and understanding, modelling and predicting of prevalent material damage mechanisms. Detailed research questions include creep life assessment of metal alloys and welded joints, fracture and fatigue measurement and modelling of boiler tubes and other high temperature components, stress corrosion cracking (SCC), creep rupture properties of advanced materials, the welding thermal cycle effect on service properties and the use of NDE to assess and monitor material integrity and remnant life. The research is categorised in three major parts: (i) sample allocation and materials testing, (ii) investigation and understanding of microstructural processes, and (iii) modelling of material behaviour.
Damage and cracking indicated with Digital Image Correlation
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Asset Management at the University of Pretoria
This SC is developing skills and techniques to monitor and manage key components affecting the availability of Eskom plant assets such as turbines, fans, generators, boilers (piping and tubes), transformers, mills, and bulk solids plant. Management of such complex assets requires a deep understanding of asset management principles enhanced by highly specialised asset integrity analysis and evaluation capabilities. This is a multidisciplinary challenge which draws expertise from diverse fields such as machine condition monitoring, signal processing, artificial intelligence, statistics, structural dynamics, finite element analysis and fatigue as well as integration of these principles into life cycle management and the decision environment.
Once critical assets have been identified, carefully selected operational data are acquired. The data feeds into the condition monitoring process, which forms the basis for diagnostics processes to identify the nature and extent of incipient faults. There is an increasing need to interpret this information from a forecasting strategy point of view, for example, to estimate the remaining useful life of assets. This information, coupled with an understanding of the asset’s load profile, provides input for life cycle decisions and interventions. All of this happens in an environment where immense amounts of data need to be stored and be accessible in standardised formats of high integrity. This process is summarised in the following schematic.
Schematic of main research thrusts
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High Voltage Engineering AC at the University of the Witwatersrand
This SC aims to build up the Eskom skills base in electrical engineering by presenting courses and 4 conducting research in the area of high voltage (AC), which includes generation, transmission and distribution.
Generator stator insulation and generator rotor insulation integrity is crucial for reliable generator operation. Due to high temperatures, mechanical stresses, and vibration present in an operating generator, there is an inevitable steady degradation of the insulation condition. Partial discharge testing is one of the most important diagnostic tests conducted on generator insulation, but test result interpretation and estimation of remaining life is still a challenge. Generator transformers also operate in demanding environments, and their failure accounts for a large portion of the current Eskom unplanned capability loss factor (UCLF).
The transmission research focuses on the performance of transmission lines in environments that include lightning strikes, switching surges, power frequency overvoltages and pollution. Once again, the objective is to maintain reliable operation of Eskom’s large transmission network. Expertise in lightning performance of transmission lines is crucial for line designs that have acceptable lightning performance (a limited number of flashovers due to lightning). Switching surge performance is particularly important for live-line work where human safety must be ensured. Good pollution performance requires insulator selection that considers the pollution performance of various types of insulators (ceramic or polymeric). In addition to a reliable transmission network, reliable operation of large electrical networks involves maintaining acceptable transient stability, small-signal stability, voltage stability and frequency stability.
In the area of distribution, research focuses on improved monitoring and protection of equipment such as transformers, which have historically had limited monitoring. Stresses on transformers have increased due to electricity theft, non-linear loads, and unbalanced sharing of single-phase loads among the three phases. With increased penetration of renewable generation in distribution, better monitoring and control of transformers will be essential. The presence of non-linear loads increases the importance of power quality and electromagnetic compatibility studies.
Factors contributing to oil-paper insulation degradation
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High Voltage Engineering DC at the University of Kwa-Zulu-Natal
This SC has two operational high voltage laboratories, one focused on direct current (DC) and the other on alternating current (AC). The combination of the two laboratories at sea level, along with a powerful real-time digital simulator (RTDS), is well situated to support Eskom with its expanding grid.
The impact of new resources, including renewable electricity sources and possibly nuclear energy, on the existing grid is important and will naturally result not only in growth, but also in a more complex grid. This will put increased pressure on South Africa to develop and consider different technologies in order to deliver electrical power efficiently and reliably.
Eskom views high voltage direct current (HVDC) systems as an enabler for future expansion of the existing grid. There are a number of potential HVDC systems, a bipole connecting the Limpopo province to Gauteng province, a separate bipole through KwaZulu-Natal, and an increase in capacity of the existing system from the Cahora Bassa Dam in Mozambique.
The strategic plan is to develop laboratories, the intellectual competence, and the design ability of Eskom and UKZN in line with the grid capacity upgrade.
HVDC systems research will focus on:
- circuit-breaker technology;
- conversion technology;
- system configurations;
- implementation of new components and technologies;
- condition monitoring;
- line configurations;
- insulation materials for transformers, overhead lines, and cables;
Modelled sphere-sphere gap
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Renewable Energy at Stellenbosch University
In the framework of the upcoming renewable energy development in South Africa in wind and concentrated solar power (CSP), some of the key technical challenges that need to be addressed by Eskom engineers in the short to medium term include:
- integrating renewable energy power stations with variable output into the national grid;
- forecasting electricity production from these power stations;
- operating and maintaining the Eskom renewable energy power stations to optimise electricity production and to reduce costs; and
- addressing some unique South African challenges such as dry-air cooling for CSP plants and cleaning of mirrors and panels in dusty, arid conditions
- support design, operation, and maintenance of wind farms and CSP plants, including the optimisation of electricity production;
- feasibility studies for renewable energy power stations;
- tender specifications and procurement processes;
- overseeing construction, commissioning and grid integration; and
- research and development to facilitate technology transfer to South African operations.
High concentration of direct normal solar irradiance over the Northern Cape
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