Maggie shares her highlights from the Conference on Power Plant Operation & Flexibility at the Institute of Materials, Minerals and Mining in London 4 – 6 July 2018.
Historically, some power plant flexibility has been important to balance energy supply and demand. Recently, it has become increasingly relevant to enable the integration of variable renewable energy (VRE), mainly wind and solar, which requires coal-fired power plants to adapt to a new operating regime. This includes: frequent start-ups and shut-downs, quick ramping, operating at low minimum load and operating in cycling mode. Additionally, power plants must still comply with emission limits.
Operating alongside VRE to provide constant, reliable energy has a significant impact on the life and costs of a power plant. As more VRE comes online, existing plants will be required to be more flexible, and new power plant designs and management methods will be needed. Hence the conference last week on Power Plant Operation and Flexibility organised by European Technology Development Ltd (ETD) was very timely and provided practical information on a range of topics, including:
- Key equipment design, materials and corrosion;
- Operational constraints and optimisation;
- Manpower, management and automation issues;
- Component replacement, maintenance and operating costs; and
- Strategies for optimising maintenance and cyclic operation.
As highlighted by Prof Scott Lockyer (Uniper Technologies),
‘preparing for flexible operation is fundamentally a Change Management process, involving both risks and opportunities to the power plant and to the Operations and Maintenance (O&M) processes and people’.
It is vital to have an adequate methodology in place, which is built on identification of risks and implementation of mitigation measures so that the risks can be addressed. For example, Uniper’s commercial solution ‘Economic Flexible Operation’ (EFO), tackles a number of flexible operation issues and has been used successfully on several power plants. Typical outcomes were illustrated in case studies and included: shorter start-up times, improved ramp rates, reduced minimum load, increased outage intervals and extended economic life of power plants.
There were a number of presentations describing both existing and under development non-destructive techniques (NDT) used for plant inspection and monitoring. These included systems to help detect early stage creep and fatigue damage as well as to map high temperature strain localisation in steel weldments.
Inspection of power plants remains a labour and time intensive task. The size of a power plant and its components, such as boilers, heat recovery systems, burners, and ducting, means that visual inspection of the various parts requires time, scaffolding and some hazardous climbing. Even then, some parts are not accessible. One potential solution is the use of drones, as currently being explored by some utilities in the USA, Europe, Australia and Japan. The use of robots that can climb up the industrial structure, crawl and creep along the power plant boiler, turbine and other equipment, or robotic arms that can reach and examine the inaccessible areas can also be very useful and save time and money, as noted by Dr Ahmed Shibli, from ETD. However, at present, existing commercially available drones are not guided through satellite navigation so they cannot be tightly controlled and need sensors to avoid frequent collisions. Once these issues are overcome, drones have the potential to be used not only for visual inspection but for other purposes, such as carrying small polishing heads and ultrasonic (UT) testing probes to carry out wall thickness measurement or detection and sizing of cracks.
For example, drones can take photographs for boiler inspection which can be enlarged 20 times and used to identify the cause of failure. In the case of a burst evaporator tube, such a photo can reveal if the damage is caused by impure feed/boiler water (thick edged rupture) or by overheating, fireside wastage and others (thin edged rapture).
In emergency shutdowns, a drone can be ‘a front runner’ (whereas for human inspection, the erection of scaffolding or ladders would be required). Drones can also carry out external inspections at elevated levels within the boiler house, turbine hall or stack or cooling towers (both internal and external). Additionally, drones can carry out aerial thermal surveys from positions that are otherwise only accessible by helicopter. Such investigations can identify where lagging is inadequate, hot gases and steam are escaping and generally where improvements and modifications are needed.
Existing robots are not suitable for power plant inspection due to their mobility issues. For example, they cannot climb the tubes in a power plant boiler due to the challenges posed by factors such as the deposits on the tubes and variations in the gaps between tubes. A possible solution for both drones and robots may be the development of a novel drone-robot hybrid device as proposed by ETD, which is already 6 months into research on this topic and is looking for interested parties to collaborate with them.
While the conference papers improved our understanding of power plant flexibility, which is my new research topic, the conference dinner and the boat cruise on Thames river gave us the opportunity to enjoy some of the most interesting London’s landmarks in the evening sun, including the Tower Bridge, London Eye and Greenwich.