The ocean is a vast source of stored energy, energy that is constantly being absorbed from wind. This source of energy now has the potential to play a vital role in the urgent need to decarbonise our atmosphere.
The ocean is a vast source of stored energy, energy that is constantly being absorbed from wind. This source of energy now has the potential to play a vital role in the urgent need to decarbonise our atmosphere.
The ocean is a vast source of stored energy, energy that is constantly being absorbed from wind. This source of energy now has the potential to play a vital role in the urgent need to decarbonise our atmosphere.
The ocean is a vast source of stored energy, energy that is constantly being absorbed from wind. This source of energy now has the potential to play a vital role in the urgent need to decarbonise our atmosphere.
The ocean is a vast source of stored energy, energy that is constantly being absorbed from wind. This source of energy now has the potential to play a vital role in the urgent need to decarbonise our atmosphere.
“The best way to predict the future is to design it” – Buckminster Fuller
ABOVE: Early Concept Drawing of a Full Size Device in Heave 2011
Currently there are several basic types of Wave Energy Converter all of which incorporate various design concepts attributed to each type. The diversity of these concepts is the result of many different points of view, different designers having differing opinions as to what constitutes the best embodiment of design priorities.
The SEACATT WEC development has been in progress since 2010. To date, apart from the years of design including physical and numerical development, four laboratory test projects have been undertaken at established European facilities, three of these projects have been funded under the MARINET programme.
MARINET (Marine Renewables Infrastructure Network for emerging Energy Technologies) is an EC-funded network of research centres and organisations that are working together to accelerate the development of marine renewable energy - wave, tidal & offshore-wind. The initiative is funded through the EC's Seventh Framework Programme (FP7) and runs for four years until 2015. The network of 29 partners with 42 specialist marine research facilities is spread across 11 EU countries and 1 International Cooperation Partner Country (Brazil). The aim of the initiative is to streamline the capabilities of test infrastructures in order to enhance their impact and accelerate the commercialisation of marine renewable energy. See www.fp7-marinet.eu for more details.
The SEACATT is based on an attenuator type design and the concept has been developed to take into consideration the following points outlined below.
No matter how efficient or cost effective a device is if it’s considered to be at odds with the environment it is trying to protect it will be unlikely to succeed commercially. In the longer term established WEC’s will be more likely to benefit from having the ability to be deployed in deeper water offshore, where energy density is greater.
Visual /environmental impacts will be greatly reduced with distance from shore, especially when successful devices are developed into multi-unit arrays. Closer to shore is not necessarily the safest place to be for moored devices, if moorings fail, reaction times for corrective measures in the event of drifting are compromised.
Even the most productive, cost effective device is unlikely to succeed commercially without high levels of certainty in terms of its overall survivability. Its sea keeping qualities would need to be equal to those of any all-weather vessel.
Apart from general survivability during periods of extreme weather, and no matter what distance from shore, it must be accepted that any device will at times have to “fend for itself” when deployed in areas of high energy density. Adequate levels of system redundancy would have to be built into the design to cope with these situations.
Successful devices will necessarily lead to large arrays; it will be very difficult for an operator to manage a large number of devices simultaneously if it is not possible to perform some level of critical maintenance while they are deployed on their moorings. The operation of any device would benefit from a design that, in terms of accessibility, could support this type of maintenance activity.
It would also be desirable from a maintenance perspective to have all core mechanical and electrical components at the surface where they can be accessed and observed without the need for diving equipment.
Although capital and operating costs are critical to any commercial project, as ultimately all renewable energy projects must be commercially viable, to date many projects that have suffered major financial setbacks have done so due to underlying technical feasibility issues. Throughout the course of its development, a project that can be demonstrated as being “technically feasible” at all key stages will be more likely to achieve ongoing financial support. Many successful technologies, including wind energy, had prolonged periods of technical development before reaching full commercial viability. Where wave energy is concerned there are currently no full scale devices operating commercially. A lot of emphasis is placed on financial viability from the very outset as part of WEC concept development protocols, financial viability is naturally difficult to predict at the early stages of development considering that the technology could and should undergo major changes if warranted in the course of design revisions.
The SEACATT WEC development has been in progress since 2010. To date, apart from the years of design including physical and numerical development, four laboratory test projects have been undertaken at established European facilities, three of these projects have been funded under the MARINET programme as follows.
As mentioned above, four laboratory test projects have been undertaken at established European facilities, three of these projects have been funded under the MARINET programme as follows.
Nov 2012, 2 weeks, the project was tested successfully for basic concept validation at the Kelvin Hydrodynamics Laboratory in Glasgow using a model of 1:40 scale.
Oct 2013, 2 weeks the Ifremar Laboratory in Brest, using a scale model of 1:15 to test to develop a representative PTO.
Sept 2014, 2 weeks, KHL Glasgow, a revised hull was successfully tested.
https://www.youtube.com/watch?v=dkHYT72pwKY The SEACATT 1:15 scale model project during testing at the Ifremer Deep Seawater Tank, Brest, France.
The “SEACATT” is a WEC which is intended for operations several kilometres offshore in depths greater than 60 metres. In this environment the device is designed to capture energy directly from ocean waves and convert it to electrical power using on-board technology.
The articulated hulls closely follow the concept of incorporating ship design into the overall structure and shape to provide good seakeeping and a secure weather-tight enclosure for the on-board installations.
Above, Early Concept Drawing at Full Scale & Cut-Away Section Showing PTO Arrangement
ABOVE: 1st Scale Test Project at the Kelvin Hydro Lab Glasgow 2012
Above, CAD Drawing of 15TH Scale Layout 201, For’d View, 2013
Above, CAD Drawing of 15TH Scale Layout 2013 Aft View, 2013
Above, CAD Drawing of 15TH Scale Layout 2013, Heave 2013
Above, CAD Drawing of 15TH Scale Layout 2013, Pitch 2013
Above, The 15th Scale Test Project During the IFREMER Deep Seawater Tank Access, Brest, 2013
Above: Heave During 1:15 Scale Test Project at the IFREMER Deep Seawater Tank, Brest, 2013.
Above, Kelvin Hydro Lab Glasgow, 1:40 Scale Project, Testing Design Development, Sept 2014
The technical fundamentals of this design which concern the operation and integration of the PTO and hull have been central to the concept from the outset. The design has a discrete mechanical PTO arrangement, with generators and an integrated system for energy accumulation and smoothing.
One of the core functions of the PTO system is to transfer the wave induced oscillations of the primary mover to the PTO main input shafts, these oscillations are put through a relatively simple mechanical rectification process which allows the output shafts to produce unidirectional rotation with useful torque applications. This mechanical rectification process also provides the PTO with the ability to absorb power from both the heave and pitch motions of the hull.
The physical process of absorbing energy from ocean waves is realised in accordance with the nature of the waves themselves, the quantity of energy being absorbed in a given moment is highly variable, following the peaks and troughs. Due to its inherent instability this form of energy initially, while still very valuable, is not compatible with the operation of standard electrical systems and would not be suitable in its raw state for direct grid integration. The power output from WEC’s therefore must undergo a process of smoothing which can be performed either within the device itself or externally. There are different types of electronic and mechanical technologies capable of facilitating stable power output but most WEC’S are designed to provide unstable power production to an external smoothing system.
As mentioned the SEACATT PTO has a power stabilisation option in the form of integrated mechanical systems which are designed to facilitate a smooth output of electrical power. The absorbed variable energy is first accumulated by a system which can deal with its unstable nature and then applied so as to provide a stabilised transfer of torque to directly driven generators. This energy smoothing process is accomplished by the use of gravitational energy accumulators which are configured to exploit the advantage that is provided by the depth of water in which the device is operating.
Each discrete PTO assembly is designed to perform four main functions in two separate operations, these are
1) Energy capture.
2) Energy accumulation.
3) Energy regeneration.
4) Electrical power production.
The PTO control system will synchronise these functions so that energy is both absorbed and produced simultaneously in order to produce a smooth energy output.
The SEACATT WEC project development has from the outset been implemented on the basis that both the hull and PTO systems should be considered and progressed as one integrated unit, this will continue to be the case.
The hull will also continue to be developed in line with the current design and a view to exploring the use of materials various materials which would reduce the capital cost of the full scale device, e.g. Ferrocement.
