As the world transitions to a clean, sustainable way of living, tidal energy has emerged as a reliable, predictable form of renewable energy that can be used to power our communities and industry, write Dr William Finnegan, Dr Thomas Flanagan, Patrick Cronin and Professor Jamie Goggins.
Figure 1a: The ORPC RivGen Marine Hydrokinetic (MHK) turbine, a schematic of the installed device
The theoretical amount of marine energy available in tidal streams, ocean currents, and riverine currents is estimated at 2,051 TWh per year. Even when conservative estimates are made to determine the amount of the resource that is practically extractable (ie, once areas with environmental, social, and economic conflicts are removed), there is 615 TWh per year of harvestable energy, which is 22 times the average annual electricity requirement of the Republic of Ireland.
Leading Irish composites design, manufacturing and testing company ÉireComposites and global marine renewable energy solutions company ORPC have teamed up with researchers at the MaREI Centre, the National University of Ireland Galway (NUI Galway), to develop and market a Marine Hydrokinetic (MHK) turbine based on ORPC’s proven, proprietary design.
The consortium also includes Mitsubishi Chemical Advanced Materials (MCAM, Germany) and Consiglio Nazionale delle Ricerche (CNR, Italy). When in operation, this innovative marine hydrokinetic power system will produce clean energy at a reduced cost, while increasing reliability and performance of electricity output.
Figure 1b: The ORPC RivGen Marine Hydrokinetic (MHK) turbine shows it being deployed
The CRIMSON project plans to bring to market ORPC’s reliable, sustainable marine energy river and tidal turbine with foils made entirely of recycled carbon fibre, while also reducing capital expenditure and operating expenditure by 33% and 66%, respectively. The project has been funded by the European Commission via the Fast Track to Innovation (FTI) programme, with a total project budget of €3.9 million.
ORPC’s marine hydrokinetic turbine
The ORPC marine hydrokinetic (MHK) turbine will see an improved design, in particular in relation to the shape and stiffness of the foils compared with the previous versions of the device.
The ORPC RivGen device is shown in Figure 1a and 1b, operating in the village of Igiugig, Alaska, where it powers a remote community, using sustainable, predictable local energy from the Kvichak River.
The RivGen Power Systems are horizontally mounted cross-flow turbines which either sit on the seabed or can be located in the middle of the water column for deeper tidal sites. From an environmental point of view, there systems offer a no-carbon, low-noise option, positively impacting local economies and enhancing ecotourism opportunities.
Recycled carbon fibre
One of the key enabling technologies of the CRIMSON project is the use of recycled carbon fibre material for the turbine foils. Currently, it is estimated that about 30% of produced carbon fibre ends up as waste in landfills and we have reached a point where global demand for carbon fibre has surpassed production.
Therefore, the CRIMSON consortium will take a circular economy approach, where old carbon-fibre components undergo a pyrolysis process to recover the carbon fibre materials and then, instead of being downcycled, are reused for the high-value application of marine component production.
MCAM’s technology was specifically designed to burn the pyrolysis gases produced to supply the energy required for the recycling process and consequently reduce the CO2 footprint.
Compared with virgin carbon fibres, the recovered short fibres do not show any negative material changes or damage and have no residual adhesions, such as pyrolysis coke on the fibre surface. Additionally, recycled carbon fibre is 20-40% less expensive than virgin carbon fibre.
Manufacture and testing
Once the foils have been redesigned, in order to improve their efficiency and energy capture, a demonstrator foil will be manufactured by ÉireComposites. The firm will use its patented composite powder epoxy technology, which has the advantage of increasing fibre straightness and fibre volumes and reducing the void content, in comparison to traditional Vacuum Assisted Resin Transfer Moulding (VARTM) methods.
This technology results in increased strength and stiffness and also has the advantages of faster cure times, lower tooling and energy cost, and safer, more environmentally friendly production. ÉireComposites will make moulds in-house for the foils, based on the new design, which are suitable for volume production.
The demonstrator foil will be installed at the Large Structures Testing Laboratory in NUI Galway for advanced structural testing in line with international standards, namely DNV GL-ST-0164 and IEC 62600-23. A first generation ORPC foil is shown in Figure 2 during structural testing.
Figure 2: Testing of a first generation ORPC RivGen foil at the Large Structures Testing Laboratory in NUI Galway
Static and dynamic will be performed on the demonstrator foil to confirm the stiffness distribution, natural frequency and strength of the foil. Following this, the foil will undergo a high-cycle fatigue test to demonstrate its fatigue strength and durability over its design lifespan of 20 years. Finally, a residual strength test will be performed on the demonstrator foil to quantify its remaining strength at end of life.
Following this advanced testing programme, a MHK turbine will be produced, incorporating any recommendations from the manufacture and structural testing of the demonstrator foil.
Operational trials of the MHK turbine will be performed by deploying the device in the CNR-INM tank and towing it at the required speed to reproduce operation over a range of current flow speed and loading conditions, in line with standard procedures for hydrokinetic turbines (IEC TS 62600-200 standards, ITTC recommended procedures 7.5-02-07-03.9). This will de-risk the new design and manufacturing technologies for the next generation of the ORPC power system.
The development of marine renewable energy provides a more reliable, sustainable form of energy production, where the proposed solution is based on a circular economy approach that uses recycled technologies and takes account of the end of life of its product.
As marine and tidal energy are still emerging forms of energy, they are struggling to compete in terms of costs. The CRIMSON project will demonstrate a 20% reduction in the levelised cost of marine renewable energy, as the use of recycled carbon fibre will be demonstrated, which has a cost reduction of 30%, results in less emissions, and is a high-performance alternative to virgin carbon fibre.
The success of the CRIMSON project will help see reduced energy bills and a cleaner, sustainable future for the Irish and EU consumers.
Authors: Dr William Finnegan is a research fellow in the MaREI Centre at the National University of Ireland Galway and a principal investigator of the CRIMSON project. He is a Chartered Engineer, and is chair of Engineers Ireland West Region, and a member of Engineers Ireland Council. Dr Tomas Flanagan is the CEO of ÉireComposites Teo and project coordinator of the CRIMSON project. Patrick Cronin is the head of European operations at ORPC. Prof Jamie Goggins is an established professor of civil engineering and a principal investigator in the MaREI Centre at the National University of Ireland Galway. He is a Chartered Engineer and a former member of Engineers Ireland Council.