Future reliable renewable energy conversion systems & networks: A collaborative UK-China project.

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Engineering

Abstract

Reliability is essential to the success of renewable energy systems. The estimated life of wind turbines is about 20 years, this is in comparison to 40 years for a conventional steam turbine generator unit. However the failure rate of wind turbines is about 3 times higher than that of conventional generators. The key feature that differentiates a renewable energy source, from conventional generation, is the inherent fluctuation of the source, giving rise to poor reliability due to fatigue cycling and consequently high life-cycle cost. This proposal aims to build a consortium of UK and Chinese researchers to investigate the scientific causes of poor reliability of components and develop solutions to improve it. Stress analysis and impact evaluation will be performed for stresses in thermal, mechanical, or coupled thermo-mechanical domains, taking into account the practical operating conditions. Accelerated aging test will be carried out to identify critical areas where improvement can be made cost-effectively. The research aims to develop new design concepts and new techniques that can be integrated in future renewable energy conversion systems and networks for reliability. Potential new techniques include active thermal management, integrated power smoothing, and mechanical stress releasing methods. These will be compared with alternative technologies that have been pursued by the consortium members and other researchers, such as gearless direct-drive systems, modular and fault tolerant designs and condition monitoring. The research will initially focus on wind turbines but will be extended to other forms of renewable electrical power generation including wave and tidal stream systems.Five UK and four Chinese universities as well as Chinese Academy of Sciences are initially included in the consortium which is strengthened by seven industrial partners from the two countries, in order to establish the expertise and facilities needed to address the multidisciplinary problem. The programme promotes essential and close interaction between the themes and the individual tasks. The interactions take a range of forms, from providing testing materials and facilities to the development of stress and reliability models for techniques for performance improvement. Chinese organisations will commit 9 PhD studentships to compliment the 7 themed PhD studentships in UK universities. The dissemination will involve academic publications, a dedicated website, consortium meetings, international seminars and events.

Publications

10 25 50
 
Description This project is part of a larger project with a number of UK (Durham, Warwick, Nottingham & Newcastle) and Chinese partners (Tsinghua University, Zheijiang University, Chinese Academy of Science, Nanjing University & Chongqing University). The project entitled, Future Reliable Renewable Energy Conversion Systems and Networks has the acronym FRENS.

Offshore renewable energy systems operate in a harsh environment difficult to access, and so component reliability is important. The electrical generator is a key component, but when it fails the system suffers from long downtime, because of the time required to remove and replace, which is also dependent upon the weather. Within the generator the bearings and winding insulation tend to be the main sub-components to fail. In this project we focused specifically on the insulation system. Insulation failure occurs because of the generator operates at too high a temperature, or due to thermal cycling. In order to investigate this a detailed electromagnetic-thermal model of the generator was developed, and linked to an insulation lifetime model, which uses temperature and electrical stresses as the input. The generator model was linked to a model of an oscillating water column wave device, so that typical and extreme operating conditions could be simulated to investigate the temperature distribution in the generator and ultimately the impact in insulation lifetime. If the generator is operating at too high a temperature because the renewable energy input is too high, then this can have a significant impact on the insulation life. Initial results from the work has shown that by controlling the power flow in the generator the temperature will be reduced and could double the expected lifetime of the insulation. Power management control linked to the thermal performance of the machine and component lifetime models will increase availability of the complete system. If such control is linked to operation and maintenance schedules then the generator can continue to produce power albeit at lower output until a suitable weather window is available for component replacement. The work from this project is continuing at Edinburgh through additional PhD students and funding from the University Sustainability Fund is being sought.
Exploitation Route The main use for this research is in the industrial sector, not only renewables, but also automotive, aerospace and offshore oil and gas for example. The technques developed in Edinburgh's part as well as the whole FRENS project can be implemented to develop more intelligent control systems to monitor and manage the health of components within industrial drive systems. In doing so industry will be able to manage the development of a component fault in a more controlled way and thus avoid catastrophic and potential expensive failures. Such intelligent condition monitoring control linked to operation and maintenance schedules would allow more timely replace and repair to take place. Potential exploitation routes include licencing, patents or even spin outs. Edinburgh is applying the techniques to tidal turbines in two EU H2020 projects, TIPA and ENFAIT, both led by Nova Innovations.
Sectors Aerospace, Defence and Marine,Energy

URL http://www.reliable-renewables.com/
 
Description In terms of impact the project results and methodology have been taken further in subsequent research projects, with one economic impact: a knowledge transfer project with Nova Innovations. The KT project with Nova was completed in 2016, and was judged as "outstanding" by Innovate UK. Results from the project were used by the company to obtain additional funding through EU H2020 programmes, in which the team at Edinburgh are involved. In terms of subsequent research projects, the findings have been used to develop additional projects at both PhD and undergraduate level. The original project was to investigate the stresses on generator windings and the impact on lifetime, with the focus on modelling. In order to add an experimental dimension, there have been three undergraduate MEng projects to investigate different air-cored winding topologies exposed to thermal, humidity and salt water stresses. Equipment for this experimental work was purchased with an equipment grant from the University of Edinburgh. The results from this work is in the process of being written up into a paper. The methodology developed in the EPSRC project, combined with the experimental investigation will be used in a TSB KTP project with Nova Innovations, in which a novel fully flooded generator is being developed for a tidal current turbine. The KTP project commenced on 1st April 2014 for 2 years. In terms of PhD research (Kaswar Mostafa), the research methodology is being applied to mechanical stresses in an electrical generator, in particular to investigate bearing wear that arises due to both mechanical and electromagnetic asymmetry. Results have been published from this work at international conferences: European Wave and Tidal Energy Conference (2013), IET Power Electronics, Machines and Drives Conference (2014) and European Wind Energy Conference (2014). Kaswar Mostafa was awarded his PhD in 2018, and is now continuing to work on the reliability of electrical generators on two EU H2020 projects, TIPA and ENFAIT, both led by Nova Innovations. In addition another PhD student (Jen Hao Wu) funded by the Energy Technology Partnership and working with Gaia Wind Ltd is investigating the reliability of small wind turbines using statistical failure data to estimate meant team to failure, service intervals and warranty costs. The statistical analysis is being linked to condition monitoring to provide intelligence to O&M procedures and thus reducing operating costs. Within FRENS this aspect was included in the modelling, but by making used of multi-physics models rather than statistical models. Jen Hao Wu was awarded his PhD in 2018. In 2015 an EPSRC Impact Accelerator Project was awarded to investigate component lifetime analysis for a small wind turbine, and how it could be applied to reliability calculations. This award follows on from the original FRENs project, but also Jen Hao Wu's PhD award from the Energy Technology Partnership with Gaia Wind Ltd highlighted above. This work is being used by Gaia Wind Ltd to inform their O&M activities and predict warranty and service costs.
Sector Energy
Impact Types Economic

 
Description EPSRC Impact Accelerator Account
Amount £19,142 (GBP)
Organisation University of Edinburgh 
Sector Academic/University
Country United Kingdom
Start 11/2015 
End 04/2016
 
Description Energy Technology Partnership Spirit Studentship
Amount £47,000 (GBP)
Organisation Energy Technology Partnership (ETP) 
Sector Academic/University
Country United Kingdom
Start 09/2013 
End 09/2015
 
Description Knowledge Transfer Partnership
Amount £220,000 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 04/2014 
End 03/2016
 
Description Tidal Energy Converter Cost Reduction via Power Take Off Optimization (TIDEL-EC FP7) 
Organisation Offshore Renewable Energy Catapult
Country United Kingdom 
Sector Charity/Non Profit 
PI Contribution Edinburgh developed thermal models and electrical models to investigate reliability of electrical machines in tidal turbines.
Collaborator Contribution The partners provided physical data for verifying models developed. The models are to be used by the industrial partners to advance existing and develop new technology. OREC were the lead partners in the project, but Edinburgh also worked with TOcardo (Dutch) and Minesto (Swedish), both tidal developers, and SINTEF in Norway. With SINTEF we developed a thermal modelling tool for electrical machines, which was then used in conjunction with electromagnetic models at Edinburgh to model generators being used by Tocardo and Minesto.
Impact Outputs from Edinburgh are in the form of Deliverables: 1. Final Report results of thermal investigation of submerged generator test, and report of validation of CFD tool as part of RTD subcontract - multi-disciplinary - thermal and electrical modelling. 2. Numerical Modelling of Losses in the Permanent Magnet Synchronous Generator (PMSG) 3. Conceptual Designs for Optimised Permanent Magnet Generators 4. Strategy for improved Power Take Off (PTO) reliability final report - mechanical and electrical. Both public and confidential versions are available for these reports.
Start Year 2016
 
Description Tidal Turbine Power Take-Off Accelerator (TIPA H2020) 
Organisation Nova Innovation Ltd
Country United Kingdom 
Sector Private 
PI Contribution My team is involved in developing reliability models of direct drive generators for tidal turbines, building directly on the methodology developed in the FRENS project. In addition my team is providing design verification working closely with the lead partner Nova Innovation and Technical University of Delft.
Collaborator Contribution The partner will be providing design information and physical data for verification of all models developed.
Impact One deliverable has been submitted already: 1. Tidal to wire Model.
Start Year 2016