Chris Christie, 19th May 2008
In order to achieve the aims, the emergent programme known as Supergen was divided into 12 parallel, but closely linked, work programmes. They comprise:
Appraisal of energy resource and converters: environmental interaction: before Supergen, little was known about the impact of energy extraction on natural wave conditions and tidal currents. As a result of this work, the physical consequences of energy extraction on marine resources are now quantifiable, and resource assessment before and after device deployment can be effectively conducted based on firm scientific principles.
Development of methodologies for device evaluation and optimisation: as a result of this work, new hardware systems for laboratory measurement are now available, as is a new generation of prediction and measurement approaches for the numerical and physical modelling of wave and tidal current energy converters at laboratory and full-scale.
Engineering guidance: this work drew on all the themes within Supergen and, as a result, there is now a central resource of documented R&D output, including old and new experience, and a research and development roadmap defining sequential priorities and needs to support the sector from concept to deployment.
Offshore energy conversion and power conditioning: thanks to this ground-breaking programme, it is now possible to gauge the network impact of individual or aggregate production from marine energy converters and explore control strategies to improve their integration with the electricity network.
Chemical conversion and storage: conventional thinking suggests that energy from marine energy devices will be exported as electricity. As a result of this work, alternative chemical media have been tested for their capacity to store and return marine energy economically, and the prospects and enabling mechanisms for chemical storage have been identified.
Network interaction of marine energy: if energy is to be exported into the electrical grid, it is necessary to understand the relationships between the marine systems and the grid itself. A novel means has been developed to explore the synergies between wind, wave and tidal current energy resources and to explore their aggregate network impact over time.
Lifetime economics: all too often, predictions of the economics of marine energy are based on debatable assumptions and methodologies. It is now possible, thanks to this work, to compare directly the relative economic efficiency of wave energy schemes of equal capacity independent of “best guesses” of individual component costs and of variations in market prices.
Moorings and foundations: this project looked at the applicability of conventional mooring systems for wave power applications and what alternative approaches are available. Non-linear effects have been shown to be fundamental to the understanding of device response and must be considered in any detailed design of the station-keeping system and its influence on peak loading and energy conversion efficiency.
Novel control systems for marine energy converters: the behaviour of wave and tidal systems is highly complex. New adaptive control techniques investigated by the project team have demonstrated the capability to increase the energy capture from a heaving wave device. Neural-network predictors, for example, have been developed to forecast next-wave data for a new generation of control systems.
Full-scale field validation: much of the theoretical and laboratory work conducted elsewhere in Supergen needed validation through full-scale study. Data collected by Supergen staff, in association with EMEC, have enabled, for the first time, systematic study of full-scale mooring and turbulence parameters crucial for assessing the interactions between the technology and the environment. Crucially, the complex and intense nature of turbulence in tidal channels has been identified as an essential topic for further study as it will have major impact on power quality and fatigue.
Assessment of testing procedures for tidal current devices: it has been common to simulate tidal devices at laboratory scales by towing models through still water. This is known to be subject to potentially significant errors. This project demonstrated the differences between measured forces on tidal device components fixed in flowing water compared with being towed in still waterand identified means of resolving these.
Economic, environmental and social impact of new marine technologies: the results of this work are the first systematic attempt to quantify the potential importance for regional and national economic development of an industry based on marine renewable energy.
As in the first round of Supergen, the work, which commenced in October, 2007, is conducted in a series of linked work streams. These are:
Numerical and physical convergence: the design of both wave and tidal systems is highly dependent on model testing and numerical modelling on computers. But how much confidence do we have in such techniques? Will tests conducted in Belfast agree with those conducted in Edinburgh, and will either set of tests agree with computer predictions? If not, which are correct or are any correct? This work will answer such questions and determine how to conduct physical and computer modelling to ensure confidence in the rests. It is rather worrying that the wave and tidal sector has not done this earlier.
Optimisation of collector form and response: there is a wide range of alternative ideas and concepts for wave energy devices. Many of these have been developed from original ideas conceived by isolated inventors and then subsequently enhanced and developed. Few, if any, have resulted from designs driven from the outset by the application of engineering science. In this project, state-of-the-art numerical optimisation procedures, such as genetic algorithms, will be used to guide the design and test process with theaim of producing optimal designs, taking into account fluid dynamics, material properties, fatigue, manufacturability and, crucially, cost. The process will mirror those already used in the aviation industry.
Combined wave and tidal effects: present-generation designs of wave energy devices do not work well in the presence of currents. Similarly, waves appear to have detrimental effects on tidal current devices. This work stream will look at how the design and performance of tidal current devices will be affected by waves; how the design and performance of wave power converters will be influenced by currents and water level changes, and how this knowledge can be used to enhance the design process.
Arrays, wakes and near field effects: as marine renewable energy moves from the deployment of individual prototype devices to commercial development of arrays, it is vital that array interaction is understood to allow accurate predictions of performance and to predict changes in the natural physical processes in coastal waters. The work will focus on both wave and tidal arrays.
Power take-off and conditioning: wave and tidal devices act by converting energy in the marine environment, first into mechanical motion within the device and then, usually, into electricity for export into the electrical grid. This work will focus on determining the best options for this second conversion, taking into account weight and, of course, cost.
Moorings and positioning: the outputs from the first phase of Supergen made it clear that moorings represent a significant uncertainty in the design and operation of marine renewable energy systems. This work will extend the substantial progress under the first phase into arrays of both wave and tidal devices.
Advanced control of devices and network integration: the marine environment and the response of devices to the environment represent a series of complex linked processes that defy the kind of simple mathematical analysis necessary for the application of most traditional control processes. This work will continue and extend that in the first phase to include effects relating to arrays and the incorporation of further more sophisticated techniques.
Reliability: there is little or no information about long-term fatigue and reliability of marine energy systems. This could represent a significant disincentive to commercial investment. Can methods and data from related industries such as wind or the offshore industry be used to prime the creation of effective reliability databases?
Economic analysis of variability and penetration: wave and tidal resources around Scotland and the UK display significant seasonal, daily and hourly variability. In addition, uncertainties, misinformation and confusion about the economic consequences of intermittency of peripheral resources have become a major issue in planning processes at national and regional levels. This work will investigate whether it is possible to predict the pattern and timing of future uptake of marine energy by the market, recognising its nature and location. Once marine renewable systems increase their proportional penetration into the electrical generating mix, how will their variability impact on the rest of the electricity network and electricity consumers, especially considering the peripherality of generation sites?
Ecological consequences of tidal and wave energy conversion: it is inevitable that the deployment and operation of marine energy extraction devices will disturb the surrounding environment. This work will study the principal ecological consequences of the extraction of tidal and wave energy in coastal and more offshore zones and determine whether such changes can be predicted from forecasts of change in the ambient flow field, energy and associated particulate regimes.
Professor Ian G. Bryden holds the chair of renewable energy at the Institute for Energy Systems, University of Edinburgh