Offshore wind, wave and tidal energy – the technological challenges
16 June 2015
Authors: John MacAskill, head of renewables (Europe), Bureau Veritas; Andrew Baldock, director sustainable energy solutions, Black & Veatch; and Dr Keith O’ Sullivan, senior marine engineer, Black & Veatch
The demand drivers for renewable energy are well known, including the decarbonisation of the power generation sector and the legally binding 2020 renewable energy targets each EU member state has set. Looking beyond 2020 to 2050, the European Union (EU) heads of states have agreed on reductions of 80-95 per cent in greenhouse gas emissions. Given the issues with reducing emissions in areas such as transport and agriculture, achieving the heads of state agreement is only possible if the power sector is essentially carbon neutral well before 2050.
On January 15, 2015, Engineers Ireland organised an event titled ‘Offshore Wind, Wave and Tidal Energy – The technological challenges’ kindly hosted at Enterprise Ireland in London and sponsored by the Sustainable Energy Authority of Ireland (SEAI). John MacAskill of Bureau Veritas and Andrew Baldock of Black & Veatch outlined the technological challenges facing the offshore renewables industry in the face of ambitious EU 2020 targets.
Despite the technical, financial and regulatory challenges facing the offshore renewables industry, the opportunities remain immense within this emerging sector. Fixed offshore wind is now largely considered a bankable asset while floating wind technology continues to emerge as a long-term solution to deeper water sites farther offshore with significant potential.
The trends emerging in this vibrant industry may be summed up as “bigger, farther, deeper and cheaper”. The key target for the offshore wind industry is to reduce the levelised cost of energy (LCOE) by 2020. To achieve this, the industry has developed larger capacity turbines to achieve more power capacity per installation.
However, the sites within which the required roll-out rate can be achieved to reach 2020 targets are now in deeper waters farther from shore. This has resulted in the need for a range of further innovations to be incorporated into the industry to continue to reduce LCOE. Foundations suited to deeper water need to be cost effective, installation methodologies need to be capable of installing larger components (foundations and turbines) faster and farther from shore and transmission infrastructure needs to deal with increased losses with increasing distance from shore.
These challenges combined have led to the industry producing some impressive innovations. These have not solely been in the interest of economic benefit but also have led to improvements in health and safety of installation activities offshore. For example, Eneco’s Luchterduinen offshore wind farm has implemented 43 non-grouted monopile foundations.
This is in contrast to the industry standard monopile plus transition piece solution and has removed the potential for grout failures. This solution also results in less steel and faster installation but has its challenges such as offshore installation of secondary steel, new piling grab to install at the required verticality and design of the monopile flange to accommodate piling without damaging the foundation.
A further innovation at this farm is the removal of scour protection for two extra-long monopile foundations. Eneco have installed monitors on the foundations to record the seabed profile around the monopile to provide measurements to challenge existing industry standards.
The introduction of floating foundations is anticipated to unlock substantial additional capacity offshore however the technology is still at the prototype deployment stage. Continued RD&D promises to deliver this technology in the medium term.
The recent financing structure achieved by the Gemini offshore wind farm in the Netherlands is also an encouraging development. The securing of project based finance or non-recourse project financing has the potential to unlock further reductions in the cost of energy. This progress is however inherently linked to the risk associated with the technology being utilised within the project itself.
The offshore wind industry is now bankable yet continuing integration of innovations in the technology as well as financing models results in lowering the cost of energy. The developments in this industry will act as significant examples for other emerging offshore renewable technologies.
Marine renewable energy is still considered very much an emerging technology. Tidal and wave energy technologies are in the technology development and prototype deployment phase, similar to floating offshore wind. Tidal and wave energy technology face similar technological challenges as they progress towards first array deployment, though both face technology specific challenges also.
The industry is currently in a difficult position with the planned divestment of the industry leading Marine Current Turbines (MCT) by Siemens and the purchasing of the former Pelamis Wave Power (PWP) intellectual property and assets by Wave Energy Scotland (WES).
The range of concepts for the extraction of energy from tidal current energy is substantial; however, the design architecture has, to an extent, converged to a widely adopted configuration – horizontal axis axial turbines (HAAT). The first generation HAAT prototypes are generally reasonably well proven with the key technical challenges being reliability, availability, maintainability (RAM) and LCOE.
The majority of variations between prototypes are in deployment techniques and the scale of the turbine itself. It is expected that these first generation machines will be used in the recent site leases for tidal energy farms in Scotland and Northern Ireland.
Achieving cost competitiveness with other forms of renewable energy remains a challenge and continuing innovations and RD&D projects are required to ensure the target LCOE can be achieved, through drivetrain reliability, foundation design and marine operations optimisation.
The recent Energy Technologies Institute (ETI) Tidal Energy Converter (TEC) project has proposed innovative solutions to these challenges. For tidal current technology, the challenges include long-term availability and RAM/operation and maintenance (O&M) strategy as well as scaling.
Scaling up of the technology will rely heavily on blades and power take-off direct drive systems, multi-turbine solutions (foundations), installation methodologies, subsea electrical infrastructure and lean design tools. Development of several types of second and third generation machines continues.
Encouragingly, the first array project at the MeyGen Pentland Firth location in Scotland has started construction. As the technology is rolled out it is anticipated that further OEM participation will take place in the industry, helping it to further address the challenges it faces in LCOE reduction, project financing and R&D funding.
In contrast to tidal current energy technology, wave technology has not converged to an accepted solution and the recent events at PWP and Aquamarine Power (APL) may open further opportunities to new designs and there are many hundreds of possibilities.
Full scale prototypes of wave devices are much less well proven than tidal equivalents, with approximately 10 per cent of the cumulative energy yield or fully operational time to date. The scale of the market is sufficient to attract government and OEMs but the key issue is the time to market for both parties.
The time scale between concept identification and full commercialisation could be up to 20 years depending on technology performance and funding availability. Adhering to a staged technology development protocol is a key element of technology de-risking and ensuring measurable progress up to deployment of a full scale prototype, which to date has not been very successful.
Sub-prototype scale devices need to be deployed rapidly and have a clear route to scaling up technically, financially and organisationally. The key technological challenges facing the wave energy industry include long-term availability/survivability of technology, RAM/O&M strategy as well as cost reductions in the device structure and increased energy yield through wave-wave sensing and control.
The industry needs continued support for technology development to assist in reducing LCOE, provision of sufficient incentives, commercial leasing rounds providing market pull and testing of first small scale arrays. The WestWave project off the west of Ireland is a prime example of an industry enabling project.
The status of offshore renewable energy technologies cannot be summed up simply, as the technologies involved are in very different stages of development. Offshore wind continues to progress forward through balancing the incorporation of innovations to address the technological challenges in reducing LCOE against increasing project related risk.
The unlocking of LCOE reductions through project financing structures and project certification provides an additional dimension to the drive for cost reduction by 2020.
Tidal current and wave energy continue to develop the technologies from concept verification stage through to prototype development stage. The recent commencement of the MeyGen Phase 1A tidal current project in Scotland provides a much needed boost to the industry and will increase confidence in the sector.
Wave energy continues to face technological challenges of reliability and survivability, yet announcements such as the US Department of Energy grant aid to Ocean Energy USA to deploy a full scale machine in Hawaii and the ESB WestWave project are encouraging developments which will continue to provide the environment the industry needs to continue to progress forwards towards commercialisation.http://www.engineersjournal.ie/2015/06/16/offshore-wind-wave-tidal-energy/http://www.engineersjournal.ie/wp-content/uploads/2015/06/wave11.jpghttp://www.engineersjournal.ie/wp-content/uploads/2015/06/wave11-300x300.jpgElecenergy,European Union,renewables,tidal,wind